GM – Geomorphology
GM1.1 – Frontiers in Geomorphology - Earth surface interactions, couplings and feedbacks
EGU21-12838 | Presentations | GM1.1 | GM Division Outstanding ECS Award Lecture 2021
Detecting flood drivers through large-sample geomorphologyLouise Slater
Many fluvial processes have long been treated as stationary, fluctuating within an unchanging envelope of variability. However, a large body of evidence has revealed that shifts in climate, land cover and river basin management may manifest locally along river networks through hydrological and geomorphic change. Measuring the effect of these changes on the local flood risk requires a large sample approach. Large sample geomorphology has existed for many decades but is currently undergoing a step-change characterised by computational techniques, scalability, and growing interdisciplinarity. This step-change has been assisted by the availability of remotely sensed datasets describing the land surface (including satellite, airborne and ground-based acquisitions), alongside other datasets more conventionally employed in hydro-climatology (including weather and climate observations, reanalysis, and projections). Within this context, data science and AI approaches facilitate pattern detection and the testing of both long-standing and emerging theories, to derive insights about processes and mechanisms at play. Here, we will discuss the value of large-sample geomorphology for understanding nonstationary landscapes and the associated flood risk. We will provide insights into the promise and pitfalls of large-sample approaches within an evolving discipline, and discuss ways forward, with more systematic hypothesis testing and developing projections of future change.
How to cite: Slater, L.: Detecting flood drivers through large-sample geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12838, https://doi.org/10.5194/egusphere-egu21-12838, 2021.
Many fluvial processes have long been treated as stationary, fluctuating within an unchanging envelope of variability. However, a large body of evidence has revealed that shifts in climate, land cover and river basin management may manifest locally along river networks through hydrological and geomorphic change. Measuring the effect of these changes on the local flood risk requires a large sample approach. Large sample geomorphology has existed for many decades but is currently undergoing a step-change characterised by computational techniques, scalability, and growing interdisciplinarity. This step-change has been assisted by the availability of remotely sensed datasets describing the land surface (including satellite, airborne and ground-based acquisitions), alongside other datasets more conventionally employed in hydro-climatology (including weather and climate observations, reanalysis, and projections). Within this context, data science and AI approaches facilitate pattern detection and the testing of both long-standing and emerging theories, to derive insights about processes and mechanisms at play. Here, we will discuss the value of large-sample geomorphology for understanding nonstationary landscapes and the associated flood risk. We will provide insights into the promise and pitfalls of large-sample approaches within an evolving discipline, and discuss ways forward, with more systematic hypothesis testing and developing projections of future change.
How to cite: Slater, L.: Detecting flood drivers through large-sample geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12838, https://doi.org/10.5194/egusphere-egu21-12838, 2021.
EGU21-948 | Presentations | GM1.1
Influence of Wildfire on Earth Surface Processes and GeomorphologyPaul Santi and Francis Rengers
Wildfire is a global phenomenon that is expected to increase in extent and severity due to shifting land management practices and climate change. It removes vegetation, deposits ash, influences water-repellent soil formation, and physically weathers rock. These changes typically lead to increased erosion through sheetwash, rilling, rock spalling, and dry ravel, as well as increased mass movement in the form of floods, debris flows, rockfall, and landslides. Post-wildfire changes in these processes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Research has documented increases in erosion after wildfire ranging from 2-1000 times the pre-fire rates. Post-wildfire landscape lowering by erosion has been measured in the western U.S. at magnitudes of 2 mm per year, with sediment delivery at the mouths of canyons increased in the range of 160-1000% during the post-wildfire window of disturbance. Furthermore, post-wildfire sediment transport enhances the development of alluvial fans, debris fans, and talus cones. Debris-flow likelihood is increased following wildfire, such that modest rainstorms with <2 year recurrence intervals are typically sufficient to trigger debris flows with volumes much larger (270-540%) than at unburned sites. In the western U.S., as much as 25-50% of alluvial fan accumulation can be attributed to post-wildfire debris flows and other post-wildfire fluvial transport. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years. Consequently, wildfire is an important agent of geomorphic change.
How to cite: Santi, P. and Rengers, F.: Influence of Wildfire on Earth Surface Processes and Geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-948, https://doi.org/10.5194/egusphere-egu21-948, 2021.
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Wildfire is a global phenomenon that is expected to increase in extent and severity due to shifting land management practices and climate change. It removes vegetation, deposits ash, influences water-repellent soil formation, and physically weathers rock. These changes typically lead to increased erosion through sheetwash, rilling, rock spalling, and dry ravel, as well as increased mass movement in the form of floods, debris flows, rockfall, and landslides. Post-wildfire changes in these processes bring about landform changes as hillslopes are lowered and stream channels aggrade or incise at increased rates. Research has documented increases in erosion after wildfire ranging from 2-1000 times the pre-fire rates. Post-wildfire landscape lowering by erosion has been measured in the western U.S. at magnitudes of 2 mm per year, with sediment delivery at the mouths of canyons increased in the range of 160-1000% during the post-wildfire window of disturbance. Furthermore, post-wildfire sediment transport enhances the development of alluvial fans, debris fans, and talus cones. Debris-flow likelihood is increased following wildfire, such that modest rainstorms with <2 year recurrence intervals are typically sufficient to trigger debris flows with volumes much larger (270-540%) than at unburned sites. In the western U.S., as much as 25-50% of alluvial fan accumulation can be attributed to post-wildfire debris flows and other post-wildfire fluvial transport. The window of disturbance to the landscape caused by wildfire is typically on the order of three to four years, with some effects persisting up to 30 years. Consequently, wildfire is an important agent of geomorphic change.
How to cite: Santi, P. and Rengers, F.: Influence of Wildfire on Earth Surface Processes and Geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-948, https://doi.org/10.5194/egusphere-egu21-948, 2021.
EGU21-2971 | Presentations | GM1.1
How geomorphology can shape policy - Advances in system understanding of the Mekong delta reveal large anthropogenic impacts and drive policy changePhilip S.J. Minderhoud, Sepehr Eslami, and Gualbert Oude Essink
Deltas have been a focal point for geomorphologists for decades, as these geologically young and transient landforms are formed and influenced by the interplay of many Earth surface processes. Hence delta systems are highly dynamic with sophisticated couplings and feedbacks that often span across multiple scientific domains. Climate change (including sea-level rise) and upstream damming alter the boundary conditions that determine how deltas form, grow, or shrink, however, the impact of human pressures within the delta system is becoming increasingly dominant in driving environmental change. Rapid economic development and urbanization of the world deltas often lead to overexploitation and exhaustion of natural resources, such as fresh water and sand. The impacts of such human-induced overexploitations have recently been shown to be dominant in driving the current geomorphological changes witnessed in the Mekong delta. The overexploitation of fresh groundwater is caused wide-spread decrease in groundwater levels in the aquifer-system, which leads to accelerated rates of land subsidence and salinization of fresh groundwater resources. The extraction of riverbed sand and upstream impoundments deepen the river channels which changes the fluvial and tidal dynamics leading to increased riverbank erosion and surface water salinization.
Recent advances in geomorphological system understanding of the Mekong delta have revealed its critical state and show its disastrous trajectory towards which it is going when current business-as-usual practices are continued in the next decades. The scientific findings from several research groups have been instrumental to the quick increase in awareness and sense of urgency within governmental bodies and has laid the foundation for the development of more system-inclusive delta policy. Although the road towards effective mitigation of the root causes is still long, multi-disciplinary geomorphological research was effective in quantifying gradual but crucial human-induced changes in the delta system. This talk highlights some of the key scientific findings in the Mekong delta and elaborates on how science was instrumental to make the issues visible to a larger community of stakeholders and policymakers.
How to cite: Minderhoud, P. S. J., Eslami, S., and Oude Essink, G.: How geomorphology can shape policy - Advances in system understanding of the Mekong delta reveal large anthropogenic impacts and drive policy change , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2971, https://doi.org/10.5194/egusphere-egu21-2971, 2021.
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Deltas have been a focal point for geomorphologists for decades, as these geologically young and transient landforms are formed and influenced by the interplay of many Earth surface processes. Hence delta systems are highly dynamic with sophisticated couplings and feedbacks that often span across multiple scientific domains. Climate change (including sea-level rise) and upstream damming alter the boundary conditions that determine how deltas form, grow, or shrink, however, the impact of human pressures within the delta system is becoming increasingly dominant in driving environmental change. Rapid economic development and urbanization of the world deltas often lead to overexploitation and exhaustion of natural resources, such as fresh water and sand. The impacts of such human-induced overexploitations have recently been shown to be dominant in driving the current geomorphological changes witnessed in the Mekong delta. The overexploitation of fresh groundwater is caused wide-spread decrease in groundwater levels in the aquifer-system, which leads to accelerated rates of land subsidence and salinization of fresh groundwater resources. The extraction of riverbed sand and upstream impoundments deepen the river channels which changes the fluvial and tidal dynamics leading to increased riverbank erosion and surface water salinization.
Recent advances in geomorphological system understanding of the Mekong delta have revealed its critical state and show its disastrous trajectory towards which it is going when current business-as-usual practices are continued in the next decades. The scientific findings from several research groups have been instrumental to the quick increase in awareness and sense of urgency within governmental bodies and has laid the foundation for the development of more system-inclusive delta policy. Although the road towards effective mitigation of the root causes is still long, multi-disciplinary geomorphological research was effective in quantifying gradual but crucial human-induced changes in the delta system. This talk highlights some of the key scientific findings in the Mekong delta and elaborates on how science was instrumental to make the issues visible to a larger community of stakeholders and policymakers.
How to cite: Minderhoud, P. S. J., Eslami, S., and Oude Essink, G.: How geomorphology can shape policy - Advances in system understanding of the Mekong delta reveal large anthropogenic impacts and drive policy change , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2971, https://doi.org/10.5194/egusphere-egu21-2971, 2021.
EGU21-3386 | Presentations | GM1.1
Geomorphological context of Quaternary desert loess - from dust sink to dust sourceOnn Crouvi, Rivka Amit, and Yehouda Enzel
Quaternary loess covers desert margins and vast areas of the Negev, southern Israel. The Negev loess is among the best-studied desert loess, with research going back to the early 20th century. The contrast between carbonate rocks of the Negev and its silicate-rich coarse-silt loess allows determining the loess sources, learning the synoptic-scale paleoclimatology, and exploring processes of coarse silt formation. Here, we present an overview of new perspectives on the origins and climatic significance of the Negev loess, expand on how (a) coarse silts affected soils farther downwind, and (b) how the loess has now turned into an active dust source.
The sources of the Negev loess are the (a) distal Sahara and Arabia delivering fine silts and clays, transported over thousands of kilometers, and (b) proximal sand dunes in Sinai and Negev, advancing and concurrently supplying the coarse silts to the loess accretion through eolian abrasion of sand grains. It was found that the coarse silts which compose the majority of the loess, commenced during the late middle Pleistocene – early late Pleistocene, coeval with the appearance of the advancing Sinai/Negev sand dunes and the first coarse silt accretion in regional soils; The main loess formation episode is ~95-10 ka, when the dunes appeared in the Negev. Within the loess, the dust mass accumulations rates (MAR), and consequently, soil formation rates, spatiotemporally vary according to specific site location and distance relative to the proximal sources. With increasing distance beyond the loess zone, both dust MARs and grain size gradually decrease; thus, whereas Mediterranean mountains located in central Israel, tens of kilometers downwind the loess, exhibit thick soils on top of the carbonate bedrock, the even wetter regions in northern Israel, located hundreds kilometers away from the loess, exhibit only thin soils. Thus, in Mediterranean regions located at the desert fringe, coarse silt influx is one of the main factors in determining the environmental sustainability, rather than only the precipitation amount.
During the Holocene, dust MARs in the Negev were much lower than late Pleistocene ones, and loess was not formed. Recently, the Negev loess became a prime source of dust mainly due to anthropogenic interferences, contributing to the regional dust cycle, and thus, at present the loess zone is a dust source rather than a dust sink. Today, the Negev loess is a non-replenishable natural resource that is slowly eroding and disappearing from the landscape.
How to cite: Crouvi, O., Amit, R., and Enzel, Y.: Geomorphological context of Quaternary desert loess - from dust sink to dust source, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3386, https://doi.org/10.5194/egusphere-egu21-3386, 2021.
Quaternary loess covers desert margins and vast areas of the Negev, southern Israel. The Negev loess is among the best-studied desert loess, with research going back to the early 20th century. The contrast between carbonate rocks of the Negev and its silicate-rich coarse-silt loess allows determining the loess sources, learning the synoptic-scale paleoclimatology, and exploring processes of coarse silt formation. Here, we present an overview of new perspectives on the origins and climatic significance of the Negev loess, expand on how (a) coarse silts affected soils farther downwind, and (b) how the loess has now turned into an active dust source.
The sources of the Negev loess are the (a) distal Sahara and Arabia delivering fine silts and clays, transported over thousands of kilometers, and (b) proximal sand dunes in Sinai and Negev, advancing and concurrently supplying the coarse silts to the loess accretion through eolian abrasion of sand grains. It was found that the coarse silts which compose the majority of the loess, commenced during the late middle Pleistocene – early late Pleistocene, coeval with the appearance of the advancing Sinai/Negev sand dunes and the first coarse silt accretion in regional soils; The main loess formation episode is ~95-10 ka, when the dunes appeared in the Negev. Within the loess, the dust mass accumulations rates (MAR), and consequently, soil formation rates, spatiotemporally vary according to specific site location and distance relative to the proximal sources. With increasing distance beyond the loess zone, both dust MARs and grain size gradually decrease; thus, whereas Mediterranean mountains located in central Israel, tens of kilometers downwind the loess, exhibit thick soils on top of the carbonate bedrock, the even wetter regions in northern Israel, located hundreds kilometers away from the loess, exhibit only thin soils. Thus, in Mediterranean regions located at the desert fringe, coarse silt influx is one of the main factors in determining the environmental sustainability, rather than only the precipitation amount.
During the Holocene, dust MARs in the Negev were much lower than late Pleistocene ones, and loess was not formed. Recently, the Negev loess became a prime source of dust mainly due to anthropogenic interferences, contributing to the regional dust cycle, and thus, at present the loess zone is a dust source rather than a dust sink. Today, the Negev loess is a non-replenishable natural resource that is slowly eroding and disappearing from the landscape.
How to cite: Crouvi, O., Amit, R., and Enzel, Y.: Geomorphological context of Quaternary desert loess - from dust sink to dust source, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3386, https://doi.org/10.5194/egusphere-egu21-3386, 2021.
Since geologic time began, Earth’s surface has been evolving through natural processes (geologic and climate forcing). Now a new force of global change is altering Earth’s morphology in unprecedented ways: humanity. Anthropogenic activities are leaving their fingerprints across Earth, driven by increasing populations, technological capacities, and societal demands (e.g. food). The magnitude of this fingerprint is currently growing, with clear impacts upon in biosphere. The recognition and analysis of these changes represent a challenge for understanding the evolution of the Earth's landscape. The purpose of this talk is focus on a specific aspect of anthropogenic landform modifications and their interaction with climate: agriculture. Agricultural landscapes cover large areas of the world, on the plains but also on high steep hillslopes. Such areas are also served by an articulated network of rural roads. Not optimal tillage practices, poor design and lack of maintenance of the drainage systems, and wrong rural road construction could significantly affect runoff patterns, cause severe erosion or even more articulated mass movements, with a direct consequence to the entire agricultural sector (e.g. productivity, cost of restoration) but also people (safety). Climate change is worsening the entire scenario. It is clear that our society should develop more resilient agriculture, where different practices should be adapted to local conditions such as climate, soil properties, but especially geomorphology. With the help of the recent remote sensing techniques and platforms (e.g., LiDAR, drones) is now possible to provide a high-resolution 3D view of terrain (also multitemporal), providing new opportunities for a better understanding of Earth surface processes based on their geomorphic signatures. In the case of agriculture, through a detailed map of concavities and convexities, and surface roughness, it is possible to recognize the alteration, due to different till practices, of important processes such as infiltration, water storage depression, and soil water erosion. It is also possible to represent in detail surface water flow directions and concentrations along rural roads, thus estimating potential soil erosion patterns or even potential landslides activation in high-steep cultivated landscapes. This work provides an overview of some useful case studies, located in low-land but also high-steep agricultural landscapes in Italy. The purpose is to offer a geomorphologic perspective, on the effects of human activities on the Earth. Understanding and addressing the causes and consequences of anthropogenic landform modifications are a global challenge. But this challenge also poses an opportunity to manage environmental resources better and protect environmental values.
References
- Tarolli P (2016). Humans and the Earth’s surface. Earth Surface Processes and Landforms, 41, 2301–2304, doi:10.1002/esp.4059.
- Tarolli P, Cao W, Sofia G, Evans D, Ellis EC (2019). From features to fingerprints: a general diagnostic framework for anthropogenic geomorphology. Progress in Physical Geography, 43, 95–128, doi:10.1177/0309133318825284.
- Tarolli P, Pijl A, Cucchiaro S, Wei W (2021). Slope instabilities in steep cultivation systems: process classification and opportunities from remote sensing. Land Degradation & Development, doi:10.1002/ldr.3798.
How to cite: Tarolli, P.: The Geomorphology of Life, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3561, https://doi.org/10.5194/egusphere-egu21-3561, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Since geologic time began, Earth’s surface has been evolving through natural processes (geologic and climate forcing). Now a new force of global change is altering Earth’s morphology in unprecedented ways: humanity. Anthropogenic activities are leaving their fingerprints across Earth, driven by increasing populations, technological capacities, and societal demands (e.g. food). The magnitude of this fingerprint is currently growing, with clear impacts upon in biosphere. The recognition and analysis of these changes represent a challenge for understanding the evolution of the Earth's landscape. The purpose of this talk is focus on a specific aspect of anthropogenic landform modifications and their interaction with climate: agriculture. Agricultural landscapes cover large areas of the world, on the plains but also on high steep hillslopes. Such areas are also served by an articulated network of rural roads. Not optimal tillage practices, poor design and lack of maintenance of the drainage systems, and wrong rural road construction could significantly affect runoff patterns, cause severe erosion or even more articulated mass movements, with a direct consequence to the entire agricultural sector (e.g. productivity, cost of restoration) but also people (safety). Climate change is worsening the entire scenario. It is clear that our society should develop more resilient agriculture, where different practices should be adapted to local conditions such as climate, soil properties, but especially geomorphology. With the help of the recent remote sensing techniques and platforms (e.g., LiDAR, drones) is now possible to provide a high-resolution 3D view of terrain (also multitemporal), providing new opportunities for a better understanding of Earth surface processes based on their geomorphic signatures. In the case of agriculture, through a detailed map of concavities and convexities, and surface roughness, it is possible to recognize the alteration, due to different till practices, of important processes such as infiltration, water storage depression, and soil water erosion. It is also possible to represent in detail surface water flow directions and concentrations along rural roads, thus estimating potential soil erosion patterns or even potential landslides activation in high-steep cultivated landscapes. This work provides an overview of some useful case studies, located in low-land but also high-steep agricultural landscapes in Italy. The purpose is to offer a geomorphologic perspective, on the effects of human activities on the Earth. Understanding and addressing the causes and consequences of anthropogenic landform modifications are a global challenge. But this challenge also poses an opportunity to manage environmental resources better and protect environmental values.
References
- Tarolli P (2016). Humans and the Earth’s surface. Earth Surface Processes and Landforms, 41, 2301–2304, doi:10.1002/esp.4059.
- Tarolli P, Cao W, Sofia G, Evans D, Ellis EC (2019). From features to fingerprints: a general diagnostic framework for anthropogenic geomorphology. Progress in Physical Geography, 43, 95–128, doi:10.1177/0309133318825284.
- Tarolli P, Pijl A, Cucchiaro S, Wei W (2021). Slope instabilities in steep cultivation systems: process classification and opportunities from remote sensing. Land Degradation & Development, doi:10.1002/ldr.3798.
How to cite: Tarolli, P.: The Geomorphology of Life, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3561, https://doi.org/10.5194/egusphere-egu21-3561, 2021.
EGU21-5520 | Presentations | GM1.1
Using the concept of hydrological connectivity to integrate physical and social systemsLouise Bracken and Jacky Croke
The concept of connectivity has found great traction in understanding the movement of fluxes across the surface of the earth through disciplinary perspectives including hydrology, geomorphology and ecology (Bracken and Croke, 2007; Bracken et al 2013;2015). Connectivity-based approaches have also generated new understanding of structural-functional relationships that characterise complex systems, for instance in computational neuroscience, social network science and systems biology (Turnbull et al., 2018). Whilst the concept of hydrological connectivity has been used widely, at all scales and with respect to fluxes of both water and sediment, critique and development of the concept is less frequent in the literature. In this paper we revisit the existing body of work around hydrological connectivity to examine whether the concept has been used to it’s full potential and explore further ways in which the concept of hydrological connectivity could be expanded to continue to drive geomorphological research. One potential avenue for research is to learn from complex systems and use the concept of connectivity to embrace human dynamics (through managing the landscape and guiding policy and regulation) on one hand and climate change (which drives system inputs) on the other. This opportunity is explored here using the water sector as a case study where planning, and managing for, water security under growing population pressures and future climate change are explored through this broader interpretation of connectivity. We see this wider coupling between humans and system inputs playing a significant role in shaping earth surface processes and sediment dynamics and a widening of definition may enable hydrologists and geomorphologists to better integrate socio-ecological systems into our research.
How to cite: Bracken, L. and Croke, J.: Using the concept of hydrological connectivity to integrate physical and social systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5520, https://doi.org/10.5194/egusphere-egu21-5520, 2021.
The concept of connectivity has found great traction in understanding the movement of fluxes across the surface of the earth through disciplinary perspectives including hydrology, geomorphology and ecology (Bracken and Croke, 2007; Bracken et al 2013;2015). Connectivity-based approaches have also generated new understanding of structural-functional relationships that characterise complex systems, for instance in computational neuroscience, social network science and systems biology (Turnbull et al., 2018). Whilst the concept of hydrological connectivity has been used widely, at all scales and with respect to fluxes of both water and sediment, critique and development of the concept is less frequent in the literature. In this paper we revisit the existing body of work around hydrological connectivity to examine whether the concept has been used to it’s full potential and explore further ways in which the concept of hydrological connectivity could be expanded to continue to drive geomorphological research. One potential avenue for research is to learn from complex systems and use the concept of connectivity to embrace human dynamics (through managing the landscape and guiding policy and regulation) on one hand and climate change (which drives system inputs) on the other. This opportunity is explored here using the water sector as a case study where planning, and managing for, water security under growing population pressures and future climate change are explored through this broader interpretation of connectivity. We see this wider coupling between humans and system inputs playing a significant role in shaping earth surface processes and sediment dynamics and a widening of definition may enable hydrologists and geomorphologists to better integrate socio-ecological systems into our research.
How to cite: Bracken, L. and Croke, J.: Using the concept of hydrological connectivity to integrate physical and social systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5520, https://doi.org/10.5194/egusphere-egu21-5520, 2021.
EGU21-9827 | Presentations | GM1.1
WALIS - Towards a global database of Last Interglacial sea-level proxies.Alessio Rovere, Deirdre Ryan, Matteo Vacchi, Alexander Simms, Andrea Dutton, and Colin Murray-Wallace
The standardization of geological data, and their compilation into geodatabases, is essential to allow more coherent regional and global analyses. In sea-level studies, the compilation of databases containing details on geological paleo sea-level proxies has been the subject of decades of work. This was largely spearheaded by the community working on Holocene timescales. While several attempts were also made to compile data from older interglacials, a truly comprehensive approach was missing. Here, we present the ongoing efforts directed to create the World Atlas of Last Interglacial Shorelines (WALIS), a project spearheaded by the PALSEA (PAGES/INQUA) community and funded by the European Research Council (ERC StG 802414). The project aims at building a sea-level database centered on the Last Interglacial (Marine Isotope Stage 5e, 125 ka), a period of time considered as an "imperfect analog" for a future warmer climate. The database is composed of 17 tables embedded into a mySQL framework with a total of more than 500 single fields to describe several properties related to paleo sea-level proxies, dated samples and metadata. In this presentation, we will show the first results of the global compilation, which includes nearly 2000 data points and will discuss its relevance in answering some of the most pressing questions related to sea-level changes in past warmer worlds.
How to cite: Rovere, A., Ryan, D., Vacchi, M., Simms, A., Dutton, A., and Murray-Wallace, C.: WALIS - Towards a global database of Last Interglacial sea-level proxies., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9827, https://doi.org/10.5194/egusphere-egu21-9827, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The standardization of geological data, and their compilation into geodatabases, is essential to allow more coherent regional and global analyses. In sea-level studies, the compilation of databases containing details on geological paleo sea-level proxies has been the subject of decades of work. This was largely spearheaded by the community working on Holocene timescales. While several attempts were also made to compile data from older interglacials, a truly comprehensive approach was missing. Here, we present the ongoing efforts directed to create the World Atlas of Last Interglacial Shorelines (WALIS), a project spearheaded by the PALSEA (PAGES/INQUA) community and funded by the European Research Council (ERC StG 802414). The project aims at building a sea-level database centered on the Last Interglacial (Marine Isotope Stage 5e, 125 ka), a period of time considered as an "imperfect analog" for a future warmer climate. The database is composed of 17 tables embedded into a mySQL framework with a total of more than 500 single fields to describe several properties related to paleo sea-level proxies, dated samples and metadata. In this presentation, we will show the first results of the global compilation, which includes nearly 2000 data points and will discuss its relevance in answering some of the most pressing questions related to sea-level changes in past warmer worlds.
How to cite: Rovere, A., Ryan, D., Vacchi, M., Simms, A., Dutton, A., and Murray-Wallace, C.: WALIS - Towards a global database of Last Interglacial sea-level proxies., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9827, https://doi.org/10.5194/egusphere-egu21-9827, 2021.
EGU21-14966 | Presentations | GM1.1
Evolution and hydrological importance of debris-covered glaciers and ice-debris landformsTobias Bolch, Owen King, James Ferguson, Nico Mölg, Andreas Vieli, and Francesca Pellicciotti
Debris-covered glaciers and ice-debris landforms such as rock glaciers are common in many mountain areas of Earth, are important for the debris transport system and contain a significant amount of ice. The presence, amount and characteristics of debris can strongly alter ice melt and the evolution of glaciers and ice-debris landforms. However, debris cover and debris content exhibits strong spatial variations. To understand the evolution and physiognomies of ice-debris complexes it is important to consider both debris supply and transport as well as deposition, which are impacted by climatic conditions, topography and lithology. A holistic approach to the investigation of these coupled complex systems seems thus crucial.
In this talk we present findings from our work based on in-situ investigations (e.g. geophysical methods), multitemporal high resolution remotely sensed imagery (including historical aerial images, Corona KH 4 images and recent data) and modelling (including surface ablation, englacial debris transport and ice flow) conducted on selected debris-covered glaciers and ice debris landforms worldwide.
Results show that a significant amount of ice is buried beneath debris cover in glacier forefields, ice cored moraines and rock glaciers under permafrost conditions. The response of rock glaciers to climate change is heterogenous with overall increasing velocities and on average only slight surface elevation changes. Slight increases in surface elevation occur their termini while debris-covered glaciers show on average a clear signal of surface lowering and decreasing velocities. The heterogeneity of debris cover can to a large extend be explained by the different debris sources and the characteristics of the headwalls while englacial and supraglacial streams favour the evolution of rough surface topography on debris-covered glaciers with the presence of ice cliffs. The findings will be illustrated with specific examples from the Swiss Alps, the Himalaya and the Tien Shan.
How to cite: Bolch, T., King, O., Ferguson, J., Mölg, N., Vieli, A., and Pellicciotti, F.: Evolution and hydrological importance of debris-covered glaciers and ice-debris landforms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14966, https://doi.org/10.5194/egusphere-egu21-14966, 2021.
Debris-covered glaciers and ice-debris landforms such as rock glaciers are common in many mountain areas of Earth, are important for the debris transport system and contain a significant amount of ice. The presence, amount and characteristics of debris can strongly alter ice melt and the evolution of glaciers and ice-debris landforms. However, debris cover and debris content exhibits strong spatial variations. To understand the evolution and physiognomies of ice-debris complexes it is important to consider both debris supply and transport as well as deposition, which are impacted by climatic conditions, topography and lithology. A holistic approach to the investigation of these coupled complex systems seems thus crucial.
In this talk we present findings from our work based on in-situ investigations (e.g. geophysical methods), multitemporal high resolution remotely sensed imagery (including historical aerial images, Corona KH 4 images and recent data) and modelling (including surface ablation, englacial debris transport and ice flow) conducted on selected debris-covered glaciers and ice debris landforms worldwide.
Results show that a significant amount of ice is buried beneath debris cover in glacier forefields, ice cored moraines and rock glaciers under permafrost conditions. The response of rock glaciers to climate change is heterogenous with overall increasing velocities and on average only slight surface elevation changes. Slight increases in surface elevation occur their termini while debris-covered glaciers show on average a clear signal of surface lowering and decreasing velocities. The heterogeneity of debris cover can to a large extend be explained by the different debris sources and the characteristics of the headwalls while englacial and supraglacial streams favour the evolution of rough surface topography on debris-covered glaciers with the presence of ice cliffs. The findings will be illustrated with specific examples from the Swiss Alps, the Himalaya and the Tien Shan.
How to cite: Bolch, T., King, O., Ferguson, J., Mölg, N., Vieli, A., and Pellicciotti, F.: Evolution and hydrological importance of debris-covered glaciers and ice-debris landforms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14966, https://doi.org/10.5194/egusphere-egu21-14966, 2021.
EGU21-16314 | Presentations | GM1.1
Connectivity in geomorphologyRonald E. Pöppl, Saskia D. Keesstra, and Anthony J. Parsons
In the past two decades, connectivity has emerged as a relevant conceptual framework for understanding the transfer of water and sediment through landscapes. In geomorphology, the concept has had particular success in the fields of fluvial geomorphology and soil erosion to better explain rates and patterns of geomorphic change in catchment systems. Sediment (dis)connectivity in geomorphic systems is generally governed by the spatial arrangement of sediment sources, transfer pathways and sinks (i.e. the structural component) as well as the interactions between landscape compartments and the frequency-magnitude relationships that dictate the relative effectiveness of geomorphic processes (i.e. the structural component; Poeppl et al., 2020). This presentation will provide a short general overview on existing concepts of connectivity in geomorphology, further highlighting and discussing recent developments in geomorphological connectivity research.
References
Ronald E. Poeppl, Kirstie A. Fryirs, Jon Tunnicliffe, Gary J. Brierley (2020). Managing sediment (dis)connectivity in fluvial systems, Science of The Total Environment, Volume 736, 139627
How to cite: Pöppl, R. E., Keesstra, S. D., and Parsons, A. J.: Connectivity in geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16314, https://doi.org/10.5194/egusphere-egu21-16314, 2021.
In the past two decades, connectivity has emerged as a relevant conceptual framework for understanding the transfer of water and sediment through landscapes. In geomorphology, the concept has had particular success in the fields of fluvial geomorphology and soil erosion to better explain rates and patterns of geomorphic change in catchment systems. Sediment (dis)connectivity in geomorphic systems is generally governed by the spatial arrangement of sediment sources, transfer pathways and sinks (i.e. the structural component) as well as the interactions between landscape compartments and the frequency-magnitude relationships that dictate the relative effectiveness of geomorphic processes (i.e. the structural component; Poeppl et al., 2020). This presentation will provide a short general overview on existing concepts of connectivity in geomorphology, further highlighting and discussing recent developments in geomorphological connectivity research.
References
Ronald E. Poeppl, Kirstie A. Fryirs, Jon Tunnicliffe, Gary J. Brierley (2020). Managing sediment (dis)connectivity in fluvial systems, Science of The Total Environment, Volume 736, 139627
How to cite: Pöppl, R. E., Keesstra, S. D., and Parsons, A. J.: Connectivity in geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16314, https://doi.org/10.5194/egusphere-egu21-16314, 2021.
GM1.2 – Biogeomorphology/Ecogeomorphology: process understanding and application
EGU21-9406 | vPICO presentations | GM1.2 | Highlight
Embracing the “I” in biogeomorphology - on the role of individuals in self-organised coastal landscapesValérie Reijers
Biogeomorphic landscapes emerge through feedback interactions between geophysical processes and biota. Plants can stabilize the soil with their extensive root systems or modulate flows of wind and water with their aboveground canopy, promoting local sediment deposition. Different plant species have evolved different suites of traits that affect their landscape-modifying ability. Here, I will present our recent work on the interactions between individual-scale organization patterns and sediment capture for dune building grasses. Using a combination of field surveys, experiments, and simple numerical models, we demonstrate that different species exhibit different clonal expansion strategies, which determine their sediment capture efficiency. Additionally, even within the same species individuals can express different organizational patterns depending on sediment dynamics. Understanding how individual plants engineer their environment depending on prevailing geophysical conditions, and how these individual-scale interactions affect both plant and landscape dynamics, is crucial for unravelling the dynamics of complex biogeomorphic landscapes.
How to cite: Reijers, V.: Embracing the “I” in biogeomorphology - on the role of individuals in self-organised coastal landscapes , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9406, https://doi.org/10.5194/egusphere-egu21-9406, 2021.
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Biogeomorphic landscapes emerge through feedback interactions between geophysical processes and biota. Plants can stabilize the soil with their extensive root systems or modulate flows of wind and water with their aboveground canopy, promoting local sediment deposition. Different plant species have evolved different suites of traits that affect their landscape-modifying ability. Here, I will present our recent work on the interactions between individual-scale organization patterns and sediment capture for dune building grasses. Using a combination of field surveys, experiments, and simple numerical models, we demonstrate that different species exhibit different clonal expansion strategies, which determine their sediment capture efficiency. Additionally, even within the same species individuals can express different organizational patterns depending on sediment dynamics. Understanding how individual plants engineer their environment depending on prevailing geophysical conditions, and how these individual-scale interactions affect both plant and landscape dynamics, is crucial for unravelling the dynamics of complex biogeomorphic landscapes.
How to cite: Reijers, V.: Embracing the “I” in biogeomorphology - on the role of individuals in self-organised coastal landscapes , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9406, https://doi.org/10.5194/egusphere-egu21-9406, 2021.
EGU21-3048 | vPICO presentations | GM1.2
Biogeomorphic development of foredune trough blowouts quantified from medium-resolution satellite imageryGerben Ruessink, Niels van Kuik, Job de Vries, and Christian Schwarz
Foredune trough blowouts are wind-eroded trough-shaped hollows in the most seaward coastal dune with their adjoining depositional lobes. They evolve on time scales ranging from strong wind events, seasons to multiple decades due to biogeomorphic interactions. Trough blowouts play an essential role in the sand budget of many coastal dune systems by connecting the beach with the backdune. There, the deposited sand can lead to vegetation rejuvenation and an overall larger floral diversity. In Northwestern Europe, nature and coastal managers have started to experiment with constructing trough blowouts in the hope that a positive sand budget beyond the foredune in concert with enlarged biodiversity improves coastal resilience in times of climate change. The spatio-temporal evolution of trough blowouts and the factors driving this evolution are not well understood, despite their common natural occurrence and construction for nature-based management.
The aim of this contribution is to quantify the spatio-temporal development of selected trough-blowout systems around the globe utilizing cloud-free medium-resolution Landsat and Sentinel-2 spectral imagery available in the Google Earth Engine platform. Linear spectral unmixing was applied on a single image basis to extract blowout surface area over time at one man-made blowout system (Zuid-Kennemerland, Netherlands) and two natural systems (Haurvig, Denmark; Padre Island, Texas, USA), assigning pixels with a fractional vegetation cover less than 50% to the blowout. At Zuid-Kennemerland and Haurvig, the blowout surface area fluctuated predominantly on seasonal time scales, with the smallest and largest values in late summer/early autumn and late winter/early spring, respectively. This seasonal variability reflects plant phenology in combination with increased sand accumulation in winter because of the more energetic wind conditions. In summer, vegetation regrew mainly at the edges of the depositional lobes and on the foredune between individual blowouts. The blowout surface area at the subtropical Padre Island varied predominantly on a multi-annual time scale. Most notably, multi-annual area decay was observed when a blowout progressed inland and lost its open connection to the beach, likely resulting in less physical disturbance and hence a dominance of ecological processes. In future work, we will combine our results with auxiliary information (e.g., multitemporal digital elevation models, time series of external forcing conditions, plant species and traits) to develop and test an eco-geomorphological model for blowout evolution. Such a model is adamant to understand what factors contribute to the success or failure of dune restoration projects involving blowouts as nature-based solutions to increase coastal resilience.
How to cite: Ruessink, G., van Kuik, N., de Vries, J., and Schwarz, C.: Biogeomorphic development of foredune trough blowouts quantified from medium-resolution satellite imagery, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3048, https://doi.org/10.5194/egusphere-egu21-3048, 2021.
Foredune trough blowouts are wind-eroded trough-shaped hollows in the most seaward coastal dune with their adjoining depositional lobes. They evolve on time scales ranging from strong wind events, seasons to multiple decades due to biogeomorphic interactions. Trough blowouts play an essential role in the sand budget of many coastal dune systems by connecting the beach with the backdune. There, the deposited sand can lead to vegetation rejuvenation and an overall larger floral diversity. In Northwestern Europe, nature and coastal managers have started to experiment with constructing trough blowouts in the hope that a positive sand budget beyond the foredune in concert with enlarged biodiversity improves coastal resilience in times of climate change. The spatio-temporal evolution of trough blowouts and the factors driving this evolution are not well understood, despite their common natural occurrence and construction for nature-based management.
The aim of this contribution is to quantify the spatio-temporal development of selected trough-blowout systems around the globe utilizing cloud-free medium-resolution Landsat and Sentinel-2 spectral imagery available in the Google Earth Engine platform. Linear spectral unmixing was applied on a single image basis to extract blowout surface area over time at one man-made blowout system (Zuid-Kennemerland, Netherlands) and two natural systems (Haurvig, Denmark; Padre Island, Texas, USA), assigning pixels with a fractional vegetation cover less than 50% to the blowout. At Zuid-Kennemerland and Haurvig, the blowout surface area fluctuated predominantly on seasonal time scales, with the smallest and largest values in late summer/early autumn and late winter/early spring, respectively. This seasonal variability reflects plant phenology in combination with increased sand accumulation in winter because of the more energetic wind conditions. In summer, vegetation regrew mainly at the edges of the depositional lobes and on the foredune between individual blowouts. The blowout surface area at the subtropical Padre Island varied predominantly on a multi-annual time scale. Most notably, multi-annual area decay was observed when a blowout progressed inland and lost its open connection to the beach, likely resulting in less physical disturbance and hence a dominance of ecological processes. In future work, we will combine our results with auxiliary information (e.g., multitemporal digital elevation models, time series of external forcing conditions, plant species and traits) to develop and test an eco-geomorphological model for blowout evolution. Such a model is adamant to understand what factors contribute to the success or failure of dune restoration projects involving blowouts as nature-based solutions to increase coastal resilience.
How to cite: Ruessink, G., van Kuik, N., de Vries, J., and Schwarz, C.: Biogeomorphic development of foredune trough blowouts quantified from medium-resolution satellite imagery, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3048, https://doi.org/10.5194/egusphere-egu21-3048, 2021.
EGU21-5669 | vPICO presentations | GM1.2
Integrating biogeomorphic feedbacks in the coastal zone to bolster coastal resiliencyCindy Palinkas and Lorie Staver
Living shorelines, defined in this study as narrow marsh fringes with adjacent sills, have been gaining traction as the preferred management strategy to mitigate shoreline erosion. These nature-based features provide the same ecosystem services as natural marshes while protecting coastlines. However, they also are threatened by the same environmental changes (sea-level rise, changing sediment supply) as natural marshes and may change characteristics of adjacent subtidal sediments. This study evaluates the role of plants in both the created marshes of living shorelines and, where present, beds of submersed aquatic vegetation (SAV) in the adjacent subtidal in the effectiveness, impacts, and resiliency of living shorelines over ~10 years in mesohaline Chesapeake Bay. At study sites, there is a net seaward movement of shorelines with living shoreline installation due to construction technique. This movement replaces shallow-water habitat immediately adjacent to the pre-existing shoreline; farther offshore, sedimentological changes vary among sites but do not appear to drive changes in the presence/absence of subtidal SAV. While current accretion rates in the created marshes are greater than local relative sea-level rise, there is evidence that accretion rates increase with marsh age, suggesting that living shorelines are most vulnerable in the first few years after installation. Because nutrient burial is maximized when SAV occur next to living shorelines, a management strategy that considers the subtidal and intertidal as integrated components of the coastal system is needed to optimize co-benefits of coastal protection.
How to cite: Palinkas, C. and Staver, L.: Integrating biogeomorphic feedbacks in the coastal zone to bolster coastal resiliency, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5669, https://doi.org/10.5194/egusphere-egu21-5669, 2021.
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Living shorelines, defined in this study as narrow marsh fringes with adjacent sills, have been gaining traction as the preferred management strategy to mitigate shoreline erosion. These nature-based features provide the same ecosystem services as natural marshes while protecting coastlines. However, they also are threatened by the same environmental changes (sea-level rise, changing sediment supply) as natural marshes and may change characteristics of adjacent subtidal sediments. This study evaluates the role of plants in both the created marshes of living shorelines and, where present, beds of submersed aquatic vegetation (SAV) in the adjacent subtidal in the effectiveness, impacts, and resiliency of living shorelines over ~10 years in mesohaline Chesapeake Bay. At study sites, there is a net seaward movement of shorelines with living shoreline installation due to construction technique. This movement replaces shallow-water habitat immediately adjacent to the pre-existing shoreline; farther offshore, sedimentological changes vary among sites but do not appear to drive changes in the presence/absence of subtidal SAV. While current accretion rates in the created marshes are greater than local relative sea-level rise, there is evidence that accretion rates increase with marsh age, suggesting that living shorelines are most vulnerable in the first few years after installation. Because nutrient burial is maximized when SAV occur next to living shorelines, a management strategy that considers the subtidal and intertidal as integrated components of the coastal system is needed to optimize co-benefits of coastal protection.
How to cite: Palinkas, C. and Staver, L.: Integrating biogeomorphic feedbacks in the coastal zone to bolster coastal resiliency, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5669, https://doi.org/10.5194/egusphere-egu21-5669, 2021.
EGU21-11017 | vPICO presentations | GM1.2
Insights in beachrock formation mechanism using multiproxy experimental data: Case study of Diolkos, Corinth, GreeceGiannis Saitis, Konstantinos Tsanakas, Anna Karkani, Satoru Kawasaki, and Niki Evelpidou
Many studies have been published concerning the occurrence and formation mechanism of beachrocks around the world. However, there are only few quantified data on the precipitation mechanism and the parameters affecting it. The formation mechanism of beachrocks is directly related to their palaeoenvironmental significance, as it provides insights into sea level evolution and palaeogeographic evolution. In this study we corelate analytical data of natural and artificial beachrocks, which were created by the microbially induced carbonate precipitation (MICP) technique using sediments and ureolytic bacteria from the coastal zone of Diolkos, Corinth, Greece.
A multiproxy analysis was accomplished which included the mineralogical and geochemical analysis of both natural and artificial beachrocks, and the sedimentological and mechanical properties analysis of the artificial ones. This study focuses on four parameters that concern the cementation processes of artificial beachrocks: (a) sediment granulometry, (b) CaCO3 content, (c) bacteria type and (d) cement type. Diolkos, due to its location and history, presents great palaeo-geographic and geoarchaeological interest; for this reason, luminescence dating was accomplished on selected beachrock samples, in order to elucidate the relative sea level changes (RSL) and palaeogeographic evolution of the site.
For the artificial beachrocks formation, we conducted solidification test using ureolytic bacteria Micrococcus yunnanensis sp. and Virgibacillus sp. isolated from local sand samples. In order to determine the solidification of the beach sediments we estimated the unconfined compressive strength (UCS) by using needle penetration test on the surface of each sample. Furthermore, the precipitated CaCO3 cement of the artificial beachrock samples, was calculated using HCl rinsing method. The artificial beachrocks were examined under SEM-EDS, XRD and XRF for their mineralogical and chemical composition accordingly.
Microscopy studies (optical and SEM-EDS) revealed that the cement of the artificial beachrock consists of calcite, in form of acicular sediment coating forming fans and multilayer concentrations. The cement in many cases was amorphous calcite crystals or microcrystalline, with thickness varying between 5 μm and 40 μm. The analysis from the artificial beachrock was correlated with the natural beachrock of Diolkos area. Our results revealed that the artificial beachrocks had different type of cement with microstratigraphy of an early digenesis. Moreover, amongst the artificial beachrocks, the sample with very well sorting (in terms of granulometry) has shown high values of CaCO3 content, which corresponds to cement, a mean value of UCS 11 MPa and the best cement precipitation.
How to cite: Saitis, G., Tsanakas, ., Karkani, A., Kawasaki, S., and Evelpidou, N.: Insights in beachrock formation mechanism using multiproxy experimental data: Case study of Diolkos, Corinth, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11017, https://doi.org/10.5194/egusphere-egu21-11017, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Many studies have been published concerning the occurrence and formation mechanism of beachrocks around the world. However, there are only few quantified data on the precipitation mechanism and the parameters affecting it. The formation mechanism of beachrocks is directly related to their palaeoenvironmental significance, as it provides insights into sea level evolution and palaeogeographic evolution. In this study we corelate analytical data of natural and artificial beachrocks, which were created by the microbially induced carbonate precipitation (MICP) technique using sediments and ureolytic bacteria from the coastal zone of Diolkos, Corinth, Greece.
A multiproxy analysis was accomplished which included the mineralogical and geochemical analysis of both natural and artificial beachrocks, and the sedimentological and mechanical properties analysis of the artificial ones. This study focuses on four parameters that concern the cementation processes of artificial beachrocks: (a) sediment granulometry, (b) CaCO3 content, (c) bacteria type and (d) cement type. Diolkos, due to its location and history, presents great palaeo-geographic and geoarchaeological interest; for this reason, luminescence dating was accomplished on selected beachrock samples, in order to elucidate the relative sea level changes (RSL) and palaeogeographic evolution of the site.
For the artificial beachrocks formation, we conducted solidification test using ureolytic bacteria Micrococcus yunnanensis sp. and Virgibacillus sp. isolated from local sand samples. In order to determine the solidification of the beach sediments we estimated the unconfined compressive strength (UCS) by using needle penetration test on the surface of each sample. Furthermore, the precipitated CaCO3 cement of the artificial beachrock samples, was calculated using HCl rinsing method. The artificial beachrocks were examined under SEM-EDS, XRD and XRF for their mineralogical and chemical composition accordingly.
Microscopy studies (optical and SEM-EDS) revealed that the cement of the artificial beachrock consists of calcite, in form of acicular sediment coating forming fans and multilayer concentrations. The cement in many cases was amorphous calcite crystals or microcrystalline, with thickness varying between 5 μm and 40 μm. The analysis from the artificial beachrock was correlated with the natural beachrock of Diolkos area. Our results revealed that the artificial beachrocks had different type of cement with microstratigraphy of an early digenesis. Moreover, amongst the artificial beachrocks, the sample with very well sorting (in terms of granulometry) has shown high values of CaCO3 content, which corresponds to cement, a mean value of UCS 11 MPa and the best cement precipitation.
How to cite: Saitis, G., Tsanakas, ., Karkani, A., Kawasaki, S., and Evelpidou, N.: Insights in beachrock formation mechanism using multiproxy experimental data: Case study of Diolkos, Corinth, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11017, https://doi.org/10.5194/egusphere-egu21-11017, 2021.
EGU21-1133 | vPICO presentations | GM1.2
Numerical Study on the Effects of Vegetation on the Intradelta Lobe AvulsionDongxue Li
Coastal wetlands play an important role for both human society and coastal ecosystems. The intradelta lobe avulsion, which causes channel shift inside the delta lobe, can create new coastal wetlands and benefit wetland restoration. Previous studies suggest that intradelta lobe avulsion is controlled by the river mouth bar stagnation that results in back filling of the river channel, which further increases the overbank flow at the natural levees and eventually leads to the avulsion. However, the natural levees are commonly colonized by vegetation, and its relevant effects on the avulsion at the levees are still elusive. In this study, we aim to quantify the effects of vegetation on the occurrence of intradelta lobe avulsion at the natural levees through numerical experiments using Delft3D. Numerical simulations of vegetated and non-vegetated scenarios were conducted with different combination of vegetation height and density, river discharge, suspended-sediment concentration and Chezy coefficient. The model results show that the existence of vegetation results in shorter levee length and river mouth bar distance relative to those of non-vegetated scenarios. The levee length and the river mouth bar distance are primarily dictated by the Chezy coefficient and the representative Chezy coefficient for non-vegetated and vegetated scenarios, respectively. In addition, the time scales of river mouth bar stagnation and the intradelta lobe avulsion tend to be shorter for vegetated scenarios, which is presumably due to the shorter river mouth bar distance that leads to a smaller accommodation space for back filling of the river channel. Our findings have important implications for predicting the future avulsion of intradelta lobe and improving the management of deltas and estuaries.
How to cite: Li, D.: Numerical Study on the Effects of Vegetation on the Intradelta Lobe Avulsion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1133, https://doi.org/10.5194/egusphere-egu21-1133, 2021.
Coastal wetlands play an important role for both human society and coastal ecosystems. The intradelta lobe avulsion, which causes channel shift inside the delta lobe, can create new coastal wetlands and benefit wetland restoration. Previous studies suggest that intradelta lobe avulsion is controlled by the river mouth bar stagnation that results in back filling of the river channel, which further increases the overbank flow at the natural levees and eventually leads to the avulsion. However, the natural levees are commonly colonized by vegetation, and its relevant effects on the avulsion at the levees are still elusive. In this study, we aim to quantify the effects of vegetation on the occurrence of intradelta lobe avulsion at the natural levees through numerical experiments using Delft3D. Numerical simulations of vegetated and non-vegetated scenarios were conducted with different combination of vegetation height and density, river discharge, suspended-sediment concentration and Chezy coefficient. The model results show that the existence of vegetation results in shorter levee length and river mouth bar distance relative to those of non-vegetated scenarios. The levee length and the river mouth bar distance are primarily dictated by the Chezy coefficient and the representative Chezy coefficient for non-vegetated and vegetated scenarios, respectively. In addition, the time scales of river mouth bar stagnation and the intradelta lobe avulsion tend to be shorter for vegetated scenarios, which is presumably due to the shorter river mouth bar distance that leads to a smaller accommodation space for back filling of the river channel. Our findings have important implications for predicting the future avulsion of intradelta lobe and improving the management of deltas and estuaries.
How to cite: Li, D.: Numerical Study on the Effects of Vegetation on the Intradelta Lobe Avulsion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1133, https://doi.org/10.5194/egusphere-egu21-1133, 2021.
EGU21-200 | vPICO presentations | GM1.2
Benthic species as mud patrol - modelled effects of bioturbators and biofilms on large-scale estuarine mud and morphologyMuriel Brückner, Christian Schwarz, Giovanni Coco, Anne Baar, Márcio Boechat Albernaz, and Maarten Kleinhans
Benthic species that live within estuarine sediments stabilize or destabilize local mud deposits through their eco-engineering activities, affecting the erosion of intertidal sediments. Possibly, the altered magnitudes in eroded sediment affect the large-scale redistribution of fines and hence morphological change. To quantify this biological control on the morphological development of estuaries, we numerically model i) biofilms, ii) two contrasting bioturbating species present in NW-Europe, and iii) their combinations by means of our novel eco-morphodynamic model. The model predicts local mud erodibility based on species pattern, which dynamically evolves from the hydrodynamics, soil mud content, competition and grazing, and is fed back into the hydromorphodynamic computations.
We find that biofilms reduce mud erosion on intertidal floodplains and stabilize estuarine morphology, whereas the two bioturbators significantly enhance inter- and supratidal mud erosion and bed elevation change, leading to a large-scale reduction in deposited mud and a widening of the estuary. In turn, the species-dependent changes in mud content redefines their habitat and leads to a redistribution of species abundances. Here, the eco-engineering affects habitat conditions and species abundance while species interactions determine species dominance. Our results show that species-specific biostabilization and bioturbation determine large-scale morphological change through mud redistribution, and at the same time affect species distribution. This suggests that benthic species have subtly changed estuarine morphology through space and time and that aggravating habitat degradation might lead to large effects on the morphology of future estuaries.
How to cite: Brückner, M., Schwarz, C., Coco, G., Baar, A., Boechat Albernaz, M., and Kleinhans, M.: Benthic species as mud patrol - modelled effects of bioturbators and biofilms on large-scale estuarine mud and morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-200, https://doi.org/10.5194/egusphere-egu21-200, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Benthic species that live within estuarine sediments stabilize or destabilize local mud deposits through their eco-engineering activities, affecting the erosion of intertidal sediments. Possibly, the altered magnitudes in eroded sediment affect the large-scale redistribution of fines and hence morphological change. To quantify this biological control on the morphological development of estuaries, we numerically model i) biofilms, ii) two contrasting bioturbating species present in NW-Europe, and iii) their combinations by means of our novel eco-morphodynamic model. The model predicts local mud erodibility based on species pattern, which dynamically evolves from the hydrodynamics, soil mud content, competition and grazing, and is fed back into the hydromorphodynamic computations.
We find that biofilms reduce mud erosion on intertidal floodplains and stabilize estuarine morphology, whereas the two bioturbators significantly enhance inter- and supratidal mud erosion and bed elevation change, leading to a large-scale reduction in deposited mud and a widening of the estuary. In turn, the species-dependent changes in mud content redefines their habitat and leads to a redistribution of species abundances. Here, the eco-engineering affects habitat conditions and species abundance while species interactions determine species dominance. Our results show that species-specific biostabilization and bioturbation determine large-scale morphological change through mud redistribution, and at the same time affect species distribution. This suggests that benthic species have subtly changed estuarine morphology through space and time and that aggravating habitat degradation might lead to large effects on the morphology of future estuaries.
How to cite: Brückner, M., Schwarz, C., Coco, G., Baar, A., Boechat Albernaz, M., and Kleinhans, M.: Benthic species as mud patrol - modelled effects of bioturbators and biofilms on large-scale estuarine mud and morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-200, https://doi.org/10.5194/egusphere-egu21-200, 2021.
EGU21-1588 | vPICO presentations | GM1.2
Mind the gap: extending the conceptual model of river island development to different environmental conditions and tree speciesWalter Bertoldi and Angela M. Gurnell
We present recent results of field observations on an island braided reach of the middle Tagliamento River, Italy, where riparian vegetation survival and establishment depends on an unstable balance between vegetation growth and flood disturbance. We combined field observations and information extracted from aerial images, airborne lidar data, and river flow time series for the period 1986-2017 to investigate the changing spatial distribution of woody vegetation and the associated changes in river topography. We also explored the role of Alnus incana (a member of the Betulaceae family), in an environment dominated by the Salicaceae family (e.g. Populus nigra).
We observed that gaps between established islands and/or floodplain offer shelter to vegetation, supporting higher colonisation success and different vegetation-landform evolution pathways.
In particular, A. incana predominantly grows in lines along channel, island and floodplain edges, bordering wooded areas dominated by P. nigra. Given their association with floodplain and island edges and the relationship of taller (older) trees with more elevated surfaces, A. incana in the study reach appears to complement the physical engineering of the dominant species, P. nigra. This suggests that P. nigra may facilitate colonisation by alder but then both species trap sediments to aggrade channel edges and bar surfaces and build island and floodplain landforms.
Time sequences of aerial images in combination with the flood disturbance time series allowed us to interpret vegetation dynamics and to identify the fate of sexual and asexual reproduction strategies by observing vegetation expansion from lines of young plants and shrubs and from uprooted deposited trees and pioneer islands, respectively. Field observations are then generalized to extend a conceptual model of island development.
Growing conditions, disturbance energy, and time (window of opportunity) between major floods are the main controls on vegetation colonization. These vary among rivers, among reaches along the same river and locally, as in the investigated gaps, allowing different tree species with different life history traits (e.g. Populus nigra, Alnus incana) to engineer local river landforms in different and complementary ways.
Although the conceptual model is inspired by observations on the Tagliamento River, consideration of species life history traits and the joint influences of growing conditions, disturbance energy and windows of opportunity provide a framework that may be applied to other temperate rivers where trees drive landform development.
How to cite: Bertoldi, W. and Gurnell, A. M.: Mind the gap: extending the conceptual model of river island development to different environmental conditions and tree species, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1588, https://doi.org/10.5194/egusphere-egu21-1588, 2021.
We present recent results of field observations on an island braided reach of the middle Tagliamento River, Italy, where riparian vegetation survival and establishment depends on an unstable balance between vegetation growth and flood disturbance. We combined field observations and information extracted from aerial images, airborne lidar data, and river flow time series for the period 1986-2017 to investigate the changing spatial distribution of woody vegetation and the associated changes in river topography. We also explored the role of Alnus incana (a member of the Betulaceae family), in an environment dominated by the Salicaceae family (e.g. Populus nigra).
We observed that gaps between established islands and/or floodplain offer shelter to vegetation, supporting higher colonisation success and different vegetation-landform evolution pathways.
In particular, A. incana predominantly grows in lines along channel, island and floodplain edges, bordering wooded areas dominated by P. nigra. Given their association with floodplain and island edges and the relationship of taller (older) trees with more elevated surfaces, A. incana in the study reach appears to complement the physical engineering of the dominant species, P. nigra. This suggests that P. nigra may facilitate colonisation by alder but then both species trap sediments to aggrade channel edges and bar surfaces and build island and floodplain landforms.
Time sequences of aerial images in combination with the flood disturbance time series allowed us to interpret vegetation dynamics and to identify the fate of sexual and asexual reproduction strategies by observing vegetation expansion from lines of young plants and shrubs and from uprooted deposited trees and pioneer islands, respectively. Field observations are then generalized to extend a conceptual model of island development.
Growing conditions, disturbance energy, and time (window of opportunity) between major floods are the main controls on vegetation colonization. These vary among rivers, among reaches along the same river and locally, as in the investigated gaps, allowing different tree species with different life history traits (e.g. Populus nigra, Alnus incana) to engineer local river landforms in different and complementary ways.
Although the conceptual model is inspired by observations on the Tagliamento River, consideration of species life history traits and the joint influences of growing conditions, disturbance energy and windows of opportunity provide a framework that may be applied to other temperate rivers where trees drive landform development.
How to cite: Bertoldi, W. and Gurnell, A. M.: Mind the gap: extending the conceptual model of river island development to different environmental conditions and tree species, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1588, https://doi.org/10.5194/egusphere-egu21-1588, 2021.
EGU21-6450 | vPICO presentations | GM1.2
A hierarchical approach linking hydraulic and ecological modeling for habitat predictions for riverine pioneer vegetationSabine Fink, Erik van Rooijen, Davide Vanzo, David F. Vetsch, Annunziato Siviglia, and Christoph Scheidegger
The distribution of sessile riparian plant species and their habitats along riverways are highly dependent on river dynamics and connectivity. River restoration and conservation of riparian plant species rely on expert knowledge and more recently also on modelling approaches to predict species’ occurrence. Ecological modelling on habitat suitability for terrestrial species is usually based on climatic and topographic features, whilst river hydrodynamics is rarely considered.
Our study aims at predicting suitable habitat for a characteristic pioneer species for dynamic riverine habitats, the German Tamarisk (Myricaria germanica). Habitat predictions are tested in a case study on a floodplain along Moesa river in canton Grisons in South-East Switzerland. We link two modeling approaches having two different spatial scales using a hierarchical process. First, we define a large-scale habitat suitability matrix based on climatic, geological and topographic predictors. Using a two-dimensional hydrodynamic model, inundation frequency maps and flood level maps for several significant months for German Tamarisk establishment are constructed, to further refine the niche for the riparian plant.
The predicted habitat suitability is evaluated with species presence data for both adult and offspring plants. Our results allow gaining insights into the importance of linking ecological and hydraulic models having different spatial and temporal scales, for more refined predictions of riparian species distribution.
How to cite: Fink, S., van Rooijen, E., Vanzo, D., Vetsch, D. F., Siviglia, A., and Scheidegger, C.: A hierarchical approach linking hydraulic and ecological modeling for habitat predictions for riverine pioneer vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6450, https://doi.org/10.5194/egusphere-egu21-6450, 2021.
The distribution of sessile riparian plant species and their habitats along riverways are highly dependent on river dynamics and connectivity. River restoration and conservation of riparian plant species rely on expert knowledge and more recently also on modelling approaches to predict species’ occurrence. Ecological modelling on habitat suitability for terrestrial species is usually based on climatic and topographic features, whilst river hydrodynamics is rarely considered.
Our study aims at predicting suitable habitat for a characteristic pioneer species for dynamic riverine habitats, the German Tamarisk (Myricaria germanica). Habitat predictions are tested in a case study on a floodplain along Moesa river in canton Grisons in South-East Switzerland. We link two modeling approaches having two different spatial scales using a hierarchical process. First, we define a large-scale habitat suitability matrix based on climatic, geological and topographic predictors. Using a two-dimensional hydrodynamic model, inundation frequency maps and flood level maps for several significant months for German Tamarisk establishment are constructed, to further refine the niche for the riparian plant.
The predicted habitat suitability is evaluated with species presence data for both adult and offspring plants. Our results allow gaining insights into the importance of linking ecological and hydraulic models having different spatial and temporal scales, for more refined predictions of riparian species distribution.
How to cite: Fink, S., van Rooijen, E., Vanzo, D., Vetsch, D. F., Siviglia, A., and Scheidegger, C.: A hierarchical approach linking hydraulic and ecological modeling for habitat predictions for riverine pioneer vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6450, https://doi.org/10.5194/egusphere-egu21-6450, 2021.
EGU21-10083 | vPICO presentations | GM1.2
Modeling groundwater-driven morphodynamic evolution of a gravel bed river in presence of riparian vegetationIlaria Cunico, Damiano Fantin, Annunziato Siviglia, Walter Bertoldi, Nico Bätz, and Francesco Caponi
The morphological trajectory of gravel bed rivers is often dictated by the interaction between riparian vegetation, flow and sediment transport. Vegetation encroachment on riverbed can significantly reduce channel mobility, preventing bank erosion and ultimately confining the river to a single-thread planform. The rate at which plants can encroach the riverbed has been mainly associated to the frequency and magnitude of flooding removing vegetation. However, recent observations indicate that the groundwater dynamics can drive distinct morphological patterns, because of its effect on the spatial distribution of vegetation and growth. However, the quantification of the processes that links groundwater to river morphological changes through vegetation remains unclear.
Here we aim at investigating the ecomorphodynamics of a gravel bed river induced by spatial variations in vegetation density by means of numerical simulations. Our case study is a 3 km long reach of the Allondon river, Switzerland, characterized by a wandering river morphology and that underwent spatially contrasting river planform changes in the last decades. Field observations suggest that deep groundwater in the upper part of the reach limited vegetation growth over years, with the main channel keeping a larger active width and dynamic behavior. On the other hand, a shallower groundwater in the downstream part provided accessible water resources for plants, which encroached the riverbed and confined the channel into a single-thread type of morphology. We performed numerical simulations with the 2D shallow water model BASEMENT, considering a mobile bed composed by uniform sediment and including the main feedbacks between vegetation growth and erosion, the flow field, and the sediment transport processes. We set up the model parameters to reproduce different vegetation spatial distributions, associated with different groundwater depths, and investigated the effect of a 10-years return period flood on the river planform change.
Model results highlight that a low vegetation biomass density, particularly at lower riverbed elevations, caused no significant effect on scour and deposition processes, favoring channel mobility and plant removal by uprooting. This behavior is in line with the observations in the groundwater-deep part of the reach. In contrast, the occurrence of high biomass density at low elevations reduced significantly the channel mobility and the river active width. In this case, vegetation was able to trigger sedimentation on bars and reduce scouring in the main channel, which are key processes for the formation of vegetated, stable riverbeds.
This study represents a step forward to the understanding of the role of the complex link between vegetation dynamics and gravel bed rivers morphodynamics and shows the potential of ecomorphodynamic modeling to interpret river morphological trajectories.
How to cite: Cunico, I., Fantin, D., Siviglia, A., Bertoldi, W., Bätz, N., and Caponi, F.: Modeling groundwater-driven morphodynamic evolution of a gravel bed river in presence of riparian vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10083, https://doi.org/10.5194/egusphere-egu21-10083, 2021.
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The morphological trajectory of gravel bed rivers is often dictated by the interaction between riparian vegetation, flow and sediment transport. Vegetation encroachment on riverbed can significantly reduce channel mobility, preventing bank erosion and ultimately confining the river to a single-thread planform. The rate at which plants can encroach the riverbed has been mainly associated to the frequency and magnitude of flooding removing vegetation. However, recent observations indicate that the groundwater dynamics can drive distinct morphological patterns, because of its effect on the spatial distribution of vegetation and growth. However, the quantification of the processes that links groundwater to river morphological changes through vegetation remains unclear.
Here we aim at investigating the ecomorphodynamics of a gravel bed river induced by spatial variations in vegetation density by means of numerical simulations. Our case study is a 3 km long reach of the Allondon river, Switzerland, characterized by a wandering river morphology and that underwent spatially contrasting river planform changes in the last decades. Field observations suggest that deep groundwater in the upper part of the reach limited vegetation growth over years, with the main channel keeping a larger active width and dynamic behavior. On the other hand, a shallower groundwater in the downstream part provided accessible water resources for plants, which encroached the riverbed and confined the channel into a single-thread type of morphology. We performed numerical simulations with the 2D shallow water model BASEMENT, considering a mobile bed composed by uniform sediment and including the main feedbacks between vegetation growth and erosion, the flow field, and the sediment transport processes. We set up the model parameters to reproduce different vegetation spatial distributions, associated with different groundwater depths, and investigated the effect of a 10-years return period flood on the river planform change.
Model results highlight that a low vegetation biomass density, particularly at lower riverbed elevations, caused no significant effect on scour and deposition processes, favoring channel mobility and plant removal by uprooting. This behavior is in line with the observations in the groundwater-deep part of the reach. In contrast, the occurrence of high biomass density at low elevations reduced significantly the channel mobility and the river active width. In this case, vegetation was able to trigger sedimentation on bars and reduce scouring in the main channel, which are key processes for the formation of vegetated, stable riverbeds.
This study represents a step forward to the understanding of the role of the complex link between vegetation dynamics and gravel bed rivers morphodynamics and shows the potential of ecomorphodynamic modeling to interpret river morphological trajectories.
How to cite: Cunico, I., Fantin, D., Siviglia, A., Bertoldi, W., Bätz, N., and Caponi, F.: Modeling groundwater-driven morphodynamic evolution of a gravel bed river in presence of riparian vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10083, https://doi.org/10.5194/egusphere-egu21-10083, 2021.
EGU21-12515 | vPICO presentations | GM1.2
Rock and Roll: RFID Tracking of Fluvial Bedload Transport and Interaction with Large WoodMiles Clark, Georgie Bennett, Aldina Franco, Sandra Ryan-Burkett, and David Sear
Bedload transport is a fundamental process by which coarse sediment is transferred through landscapes by river networks and is characterized by cyclic sequences of particle motion and rest. Bedload transport has many complex physical controls but may be well described stochastically by distributions of grain step length and rest time obtained through tracer studies. To date, none of these published tracer studies have specifically investigated the influence of large wood on distributions of step length or rest time, limiting the applicability of stochastic sediment transport models in these settings. Large wood is a major component of many forested rivers and is increasing because of disturbances such as wildfire and insect infestations as well as its use in rivers as part of ‘Natural Food Management’ (NFM) practice. This study aims to investigate and model the influence of large wood on grain-scale bedload transport.
St Louis Creek, an alpine stream in the Fraser Experimental Forest, Colorado, is experiencing increased wood loading resulting from the infestation of the mountain pine beetle in the past decades. We inserted 957 Passive Integrative Transponders (PIT) tagged cobbles in 2016 upstream of a wood loaded reach and measured and tagged > 20 pieces of large wood in the channel. We resurveyed the cobbles and wood on an annual basis after snowmelt, building distributions of rock-step lengths as well as observing any changes and transport of large wood. Additionally, a novel modelling approach based on linear mixed modelling (LMM) statistical approaches is implemented to establish the significance of wood and other factors on probability of particle entrainment, deposition and step length.
Tracer sediments accumulated both up and downstream of large wood pieces, with LMM analysis confirming a reduction in the probability of entrainment of tracers closer to wood. In addition, when tracers were remobilised, their subsequent step lengths were shorter the closer they were deposited to large wood. In 2019, large wood significantly reduced the step lengths of tracer particles, forcing premature deposition of tracers. This study demonstrates the role of large wood in influencing bedload transport in alpine stream environments, with implications for both natural and anthropogenic addition of wood debris in fluvial environments.
How to cite: Clark, M., Bennett, G., Franco, A., Ryan-Burkett, S., and Sear, D.: Rock and Roll: RFID Tracking of Fluvial Bedload Transport and Interaction with Large Wood , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12515, https://doi.org/10.5194/egusphere-egu21-12515, 2021.
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Bedload transport is a fundamental process by which coarse sediment is transferred through landscapes by river networks and is characterized by cyclic sequences of particle motion and rest. Bedload transport has many complex physical controls but may be well described stochastically by distributions of grain step length and rest time obtained through tracer studies. To date, none of these published tracer studies have specifically investigated the influence of large wood on distributions of step length or rest time, limiting the applicability of stochastic sediment transport models in these settings. Large wood is a major component of many forested rivers and is increasing because of disturbances such as wildfire and insect infestations as well as its use in rivers as part of ‘Natural Food Management’ (NFM) practice. This study aims to investigate and model the influence of large wood on grain-scale bedload transport.
St Louis Creek, an alpine stream in the Fraser Experimental Forest, Colorado, is experiencing increased wood loading resulting from the infestation of the mountain pine beetle in the past decades. We inserted 957 Passive Integrative Transponders (PIT) tagged cobbles in 2016 upstream of a wood loaded reach and measured and tagged > 20 pieces of large wood in the channel. We resurveyed the cobbles and wood on an annual basis after snowmelt, building distributions of rock-step lengths as well as observing any changes and transport of large wood. Additionally, a novel modelling approach based on linear mixed modelling (LMM) statistical approaches is implemented to establish the significance of wood and other factors on probability of particle entrainment, deposition and step length.
Tracer sediments accumulated both up and downstream of large wood pieces, with LMM analysis confirming a reduction in the probability of entrainment of tracers closer to wood. In addition, when tracers were remobilised, their subsequent step lengths were shorter the closer they were deposited to large wood. In 2019, large wood significantly reduced the step lengths of tracer particles, forcing premature deposition of tracers. This study demonstrates the role of large wood in influencing bedload transport in alpine stream environments, with implications for both natural and anthropogenic addition of wood debris in fluvial environments.
How to cite: Clark, M., Bennett, G., Franco, A., Ryan-Burkett, S., and Sear, D.: Rock and Roll: RFID Tracking of Fluvial Bedload Transport and Interaction with Large Wood , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12515, https://doi.org/10.5194/egusphere-egu21-12515, 2021.
EGU21-10684 | vPICO presentations | GM1.2
Terrestrial biospheric carbon export from rivers by bedload transportSophia Dosch, Hovius Niels, Repasch Marisa, Scheingross Joel, Turowski Jens, and Sachse Dirk
Rivers are natural conveyor belts distributing the products of erosion across Earth’s surface. If river biospheric organic matter survives long-distance transport and fluvial reworking, it can be deposited and buried in marine depozones, acting to remove carbon from the short-term carbon cycle and draw down CO2 from the atmosphere to a carbon sink over geological time scales.
It is estimated that globally, river suspended sediment fluxes deliver up to 230 MtC yr-1 biospheric particulate organic carbon (POC) to the ocean. In addition to this commonly measured POC, coarse particulate organic matter (CPOM, > 1mm) has been observed to travel with bedload in modern rivers. Several studies describe terrestrial coarse litter and woody debris buried in sandy turbidite layers and capped by muddy sediment, suggesting effective transport and burial of coarse, relatively fresh organic material to marine depozones.
However, it is unknown whether this CPOM derives from distal sources and survives long-distance fluvial transit, or if distal material is degraded during transit and replaced by CPOM from sources proximal to the coasts. Furthermore, fluxes of CPOM travelling at the river bed are largely unknown, making it an important, yet largely unconstrained term of the carbon budget. Here we investigate the fate of bedload CPOM transported over long distances to determine whether it is preserved, deposited, or degraded and replaced during fluvial transit.
We sampled river bed material from several locations along the Río Bermejo, an intracontinental lowland river in northeast Argentina. At each sampling location, we found substantial amounts of organic matter, together with clastic sediment, from the river bed. To trace the source of the CPOM, we extracted leaf wax n-alkanes and measured their stable hydrogen isotope ratios (d2Hwax). We compared d2Hwax of bed CPOM to d2Hwax of river suspended sediment, soil and litter samples from the river catchment in order to determine its provenance and transport pathway.
Changes in biomarker distribution suggest that the organic matter is recruited from local sources along the river, either as plant debris or as partly degraded litter. In addition, CPOM becomes more degraded, while the n-alkane concentration increases with increasing downstream transport. Our initial data suggests that CPOM is derived partly from distal sources and preserved during fluvial transit. While some part of the CPOM is likely to be oxidized to CO2, fresh input is added along the way, potentially overprinting the upstream signal.
With additional measurements of stable carbon isotope ratios, we expect to verify the source and the fate of the bed CPOM. While it is difficult to quantify the flux of bedload CPOM, we plan to present a first-order approximation by combining river bed flow velocities measured via acoustic doppler current profiler (ADCP) and measurements of CPOM mass collected over our sampling times.
How to cite: Dosch, S., Niels, H., Marisa, R., Joel, S., Jens, T., and Dirk, S.: Terrestrial biospheric carbon export from rivers by bedload transport, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10684, https://doi.org/10.5194/egusphere-egu21-10684, 2021.
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Rivers are natural conveyor belts distributing the products of erosion across Earth’s surface. If river biospheric organic matter survives long-distance transport and fluvial reworking, it can be deposited and buried in marine depozones, acting to remove carbon from the short-term carbon cycle and draw down CO2 from the atmosphere to a carbon sink over geological time scales.
It is estimated that globally, river suspended sediment fluxes deliver up to 230 MtC yr-1 biospheric particulate organic carbon (POC) to the ocean. In addition to this commonly measured POC, coarse particulate organic matter (CPOM, > 1mm) has been observed to travel with bedload in modern rivers. Several studies describe terrestrial coarse litter and woody debris buried in sandy turbidite layers and capped by muddy sediment, suggesting effective transport and burial of coarse, relatively fresh organic material to marine depozones.
However, it is unknown whether this CPOM derives from distal sources and survives long-distance fluvial transit, or if distal material is degraded during transit and replaced by CPOM from sources proximal to the coasts. Furthermore, fluxes of CPOM travelling at the river bed are largely unknown, making it an important, yet largely unconstrained term of the carbon budget. Here we investigate the fate of bedload CPOM transported over long distances to determine whether it is preserved, deposited, or degraded and replaced during fluvial transit.
We sampled river bed material from several locations along the Río Bermejo, an intracontinental lowland river in northeast Argentina. At each sampling location, we found substantial amounts of organic matter, together with clastic sediment, from the river bed. To trace the source of the CPOM, we extracted leaf wax n-alkanes and measured their stable hydrogen isotope ratios (d2Hwax). We compared d2Hwax of bed CPOM to d2Hwax of river suspended sediment, soil and litter samples from the river catchment in order to determine its provenance and transport pathway.
Changes in biomarker distribution suggest that the organic matter is recruited from local sources along the river, either as plant debris or as partly degraded litter. In addition, CPOM becomes more degraded, while the n-alkane concentration increases with increasing downstream transport. Our initial data suggests that CPOM is derived partly from distal sources and preserved during fluvial transit. While some part of the CPOM is likely to be oxidized to CO2, fresh input is added along the way, potentially overprinting the upstream signal.
With additional measurements of stable carbon isotope ratios, we expect to verify the source and the fate of the bed CPOM. While it is difficult to quantify the flux of bedload CPOM, we plan to present a first-order approximation by combining river bed flow velocities measured via acoustic doppler current profiler (ADCP) and measurements of CPOM mass collected over our sampling times.
How to cite: Dosch, S., Niels, H., Marisa, R., Joel, S., Jens, T., and Dirk, S.: Terrestrial biospheric carbon export from rivers by bedload transport, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10684, https://doi.org/10.5194/egusphere-egu21-10684, 2021.
EGU21-16278 | vPICO presentations | GM1.2
Quantification of biogeomorphic interactions between small-scale sediment transport and primary vegetation succession on proglacial slopes of the Gepatschferner, AustriaStefan Haselberger, Lisa-Maria Ohler, Jan-Christoph Otto, Robert R. Junker, Thomas Glade, and Sabine Kraushaar
Proglacial slopes provide suitable conditions to observe the co-development of abiotic and biotic systems. The frequency and magnitude of geomorphic processes and composition of plants govern this interplay, which is described in the biogeormorphic feedback window for glacier forelands. The study sets out to quantify small-scale sediment transport via mechanical erosion plots along a plant cover gradient and to investigate the multidirectional interactions between abiotic and biotic processes. We aim to generate quantitative data to test the biogeomorphic feedback window.
Small-scale biogeomorphic interactions were investigated on 30 test plots of 2 x 3 m size on proglacial slopes of the Gepatschferner (Kaunertal) in the Austrian Alps during snow-free summer months over three consecutive years. The experimental plots were established on slopes along a plant cover gradient. A detailed vegetation survey was carried out to capture biotic conditions and specific sediment yield was measured at each plot. Species abundance and composition at each site, as well as plant functional types reflected successional stages.
We observed a strong decline in geomorphic activity on plots with above 30% plant cover. Mean monthly rates of specific sediment yield decreased from 111 g m-2 to 37 g m-2. Non-metric multidimensional scaling showed distinct vegetation composition for the three stages of biogeomorphic succession. Quantified process rates and observed vegetation composition support the concept of biogeomorphic feedback windows. The findings help to narrow down a stage during succession where the importance of biotic processes start to dominate.
How to cite: Haselberger, S., Ohler, L.-M., Otto, J.-C., Junker, R. R., Glade, T., and Kraushaar, S.: Quantification of biogeomorphic interactions between small-scale sediment transport and primary vegetation succession on proglacial slopes of the Gepatschferner, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16278, https://doi.org/10.5194/egusphere-egu21-16278, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Proglacial slopes provide suitable conditions to observe the co-development of abiotic and biotic systems. The frequency and magnitude of geomorphic processes and composition of plants govern this interplay, which is described in the biogeormorphic feedback window for glacier forelands. The study sets out to quantify small-scale sediment transport via mechanical erosion plots along a plant cover gradient and to investigate the multidirectional interactions between abiotic and biotic processes. We aim to generate quantitative data to test the biogeomorphic feedback window.
Small-scale biogeomorphic interactions were investigated on 30 test plots of 2 x 3 m size on proglacial slopes of the Gepatschferner (Kaunertal) in the Austrian Alps during snow-free summer months over three consecutive years. The experimental plots were established on slopes along a plant cover gradient. A detailed vegetation survey was carried out to capture biotic conditions and specific sediment yield was measured at each plot. Species abundance and composition at each site, as well as plant functional types reflected successional stages.
We observed a strong decline in geomorphic activity on plots with above 30% plant cover. Mean monthly rates of specific sediment yield decreased from 111 g m-2 to 37 g m-2. Non-metric multidimensional scaling showed distinct vegetation composition for the three stages of biogeomorphic succession. Quantified process rates and observed vegetation composition support the concept of biogeomorphic feedback windows. The findings help to narrow down a stage during succession where the importance of biotic processes start to dominate.
How to cite: Haselberger, S., Ohler, L.-M., Otto, J.-C., Junker, R. R., Glade, T., and Kraushaar, S.: Quantification of biogeomorphic interactions between small-scale sediment transport and primary vegetation succession on proglacial slopes of the Gepatschferner, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16278, https://doi.org/10.5194/egusphere-egu21-16278, 2021.
EGU21-4179 | vPICO presentations | GM1.2
UAV-based cm-scale mapping of biofilms and Chl-a patterns in glacial forefields using visible band ratiosMatteo Roncoroni, Davide Mancini, Tyler Joe Kohler, Floreana Marie Miesen, Mattia Gianini, Tom Ian Battin, and Stuart Nicholas Lane
Biofilms have received great attention in the last few decades including their potential contribution to carbon fluxes and ecosystem engineering in aquatic ecosystems. Quantifying the spatial distribution of biofilms and their dynamics through time is a critical challenge. Satellite imagery is one solution, and can provide multi- and hyper-spectral data but not necessarily the spatial resolution that such studies need. Multi- and hyper-spectral data sets may be of particular value for not simply detecting the presense/absence of biofilms but also indicators of primary productivity such as chlorophyll-a concentrations. Spatial resolution is sensor quality dependent, but also controlled by sensor elevation above the ground. Hence, higher resolutions can be achieved either by using a very expensive sensor or by decreasing the distance between the target area and the sensor itself. To date, sensor technology has advanced to a point where multi- or even hyper-spectral cameras can be easily transported by UAVs, potentially yielding wide-range spectral information at unprecedented spatial resolutions. That said, such set ups have often exorbitant costs (several 1000s of US$) that few research institutions can afford or, due to the high probability of sensor lost, are risky to use. This is particularly true for glacier forefields where low air temperatures, dust and sudden wind gusts can easily damage both UAV and sensor components.
In this paper we test the performance of visible band ratios for mapping both biofilms and chlorophyll-a concentrations in an alpine glacier forefield characterized by a well-developed and heterogeneous (kryal, krenal and rhithral) stream system. The paper shows that low-cost and consumer grade UAVs can be easily deployed in such extreme environments, delivering high temporal resolution datasets and with sufficient quality RGB images for photogrammetric (SfM-MVS) processing and post-processing image analysis (i.e., band ratios). This paper shows also that visible band ratios correlates with chlorophyll-a concentrations yielding reliable chlorophyll-a information of the forefield and at the centimetric scale. This in turn allows for precise identification of the environmental conditions that lead to both biofilm development and removal through perturbation.
How to cite: Roncoroni, M., Mancini, D., Kohler, T. J., Miesen, F. M., Gianini, M., Battin, T. I., and Lane, S. N.: UAV-based cm-scale mapping of biofilms and Chl-a patterns in glacial forefields using visible band ratios, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4179, https://doi.org/10.5194/egusphere-egu21-4179, 2021.
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Biofilms have received great attention in the last few decades including their potential contribution to carbon fluxes and ecosystem engineering in aquatic ecosystems. Quantifying the spatial distribution of biofilms and their dynamics through time is a critical challenge. Satellite imagery is one solution, and can provide multi- and hyper-spectral data but not necessarily the spatial resolution that such studies need. Multi- and hyper-spectral data sets may be of particular value for not simply detecting the presense/absence of biofilms but also indicators of primary productivity such as chlorophyll-a concentrations. Spatial resolution is sensor quality dependent, but also controlled by sensor elevation above the ground. Hence, higher resolutions can be achieved either by using a very expensive sensor or by decreasing the distance between the target area and the sensor itself. To date, sensor technology has advanced to a point where multi- or even hyper-spectral cameras can be easily transported by UAVs, potentially yielding wide-range spectral information at unprecedented spatial resolutions. That said, such set ups have often exorbitant costs (several 1000s of US$) that few research institutions can afford or, due to the high probability of sensor lost, are risky to use. This is particularly true for glacier forefields where low air temperatures, dust and sudden wind gusts can easily damage both UAV and sensor components.
In this paper we test the performance of visible band ratios for mapping both biofilms and chlorophyll-a concentrations in an alpine glacier forefield characterized by a well-developed and heterogeneous (kryal, krenal and rhithral) stream system. The paper shows that low-cost and consumer grade UAVs can be easily deployed in such extreme environments, delivering high temporal resolution datasets and with sufficient quality RGB images for photogrammetric (SfM-MVS) processing and post-processing image analysis (i.e., band ratios). This paper shows also that visible band ratios correlates with chlorophyll-a concentrations yielding reliable chlorophyll-a information of the forefield and at the centimetric scale. This in turn allows for precise identification of the environmental conditions that lead to both biofilm development and removal through perturbation.
How to cite: Roncoroni, M., Mancini, D., Kohler, T. J., Miesen, F. M., Gianini, M., Battin, T. I., and Lane, S. N.: UAV-based cm-scale mapping of biofilms and Chl-a patterns in glacial forefields using visible band ratios, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4179, https://doi.org/10.5194/egusphere-egu21-4179, 2021.
EGU21-4239 | vPICO presentations | GM1.2
Effects of vegetation as an ecosystem service on the changes in runoff and sediment yield in a Mediterranean semi-arid basinMaría Rosario Vidal-Abarca Gutiérrez, Alberto Martínez-Salvador, Carmelo Conesa-García, María Luisa Suárez-Alonso, Francisco Alonso-Sarria, Pedro Pérez-Cutillas, and Francisco J. Gomáriz-Castillo
Semiarid basins contribute significantly to sediment loads, as they are often characterized by torrential flows, source areas with high sediment-producing rates, great availability of erodible material subjected to intense weathering processes, and poor vegetation cover. Vegetation, despite its scarce presence, is a dynamic component of this environment, which provides a range of important ecosystem services such as biodiversity, flood retention, nutrient sink, erosion control and groundwater recharge. This study examines the vegetation responses to the magnitude of peak flows and its contribution to the changes in runoff and sediment yield during the period 1997-2020 in a catchment Mediterranean semiarid basin: The Rambla de la Azohía (southeastern Spain).Vegetation type, density, preferred location and degree of permanence in each sub-basin were analyzed in order to determine their degree of influence on surface runoff and erosion control. Changes in riparian vegetation cover was quantified at large scale for the analysis period (1997-2020), using remotely sensed spatial information, such as satellite images and aerial photographs separated by two years on average (at scales from 1:15000 to 1:30000, and resolution between 0.22 and 0.50 m/pixel). A geo-spatial erosion prediction model was applied to estimate the runoff and sediment load generated at the event scale, taking into account the variability of the vegetation cover in each sub-basin. The simulated outputs of this model were previously calibrated with water levels measured by pressure sensors and suspended sediment records.The results showed both a poor response of vegetation (low incidence in the runoff coefficient) in steep metamorphic watersheds, capable of supplying large sediment loads, and functioned as an efficient ecosystem service (stabilization of slopes and decrease in peak flow) in less steep sub-basins with slopes in the shadow, composed of limestone formations and alluvial fans. This suggests important spatial differences in the vegetation impact, according to other environmental conditions intrinsic to each sub-basin, but also a low overall influence on the temporal variability of sediment fluxes at the event scale. This research was funded by FEDER/Spanish Ministry of Science, Innovation and Universities—State Research Agency (AEI)/Projects CGL2017-84625-C2-1-R and CGL2017-84625-C2-2-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
How to cite: Vidal-Abarca Gutiérrez, M. R., Martínez-Salvador, A., Conesa-García, C., Suárez-Alonso, M. L., Alonso-Sarria, F., Pérez-Cutillas, P., and Gomáriz-Castillo, F. J.: Effects of vegetation as an ecosystem service on the changes in runoff and sediment yield in a Mediterranean semi-arid basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4239, https://doi.org/10.5194/egusphere-egu21-4239, 2021.
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Semiarid basins contribute significantly to sediment loads, as they are often characterized by torrential flows, source areas with high sediment-producing rates, great availability of erodible material subjected to intense weathering processes, and poor vegetation cover. Vegetation, despite its scarce presence, is a dynamic component of this environment, which provides a range of important ecosystem services such as biodiversity, flood retention, nutrient sink, erosion control and groundwater recharge. This study examines the vegetation responses to the magnitude of peak flows and its contribution to the changes in runoff and sediment yield during the period 1997-2020 in a catchment Mediterranean semiarid basin: The Rambla de la Azohía (southeastern Spain).Vegetation type, density, preferred location and degree of permanence in each sub-basin were analyzed in order to determine their degree of influence on surface runoff and erosion control. Changes in riparian vegetation cover was quantified at large scale for the analysis period (1997-2020), using remotely sensed spatial information, such as satellite images and aerial photographs separated by two years on average (at scales from 1:15000 to 1:30000, and resolution between 0.22 and 0.50 m/pixel). A geo-spatial erosion prediction model was applied to estimate the runoff and sediment load generated at the event scale, taking into account the variability of the vegetation cover in each sub-basin. The simulated outputs of this model were previously calibrated with water levels measured by pressure sensors and suspended sediment records.The results showed both a poor response of vegetation (low incidence in the runoff coefficient) in steep metamorphic watersheds, capable of supplying large sediment loads, and functioned as an efficient ecosystem service (stabilization of slopes and decrease in peak flow) in less steep sub-basins with slopes in the shadow, composed of limestone formations and alluvial fans. This suggests important spatial differences in the vegetation impact, according to other environmental conditions intrinsic to each sub-basin, but also a low overall influence on the temporal variability of sediment fluxes at the event scale. This research was funded by FEDER/Spanish Ministry of Science, Innovation and Universities—State Research Agency (AEI)/Projects CGL2017-84625-C2-1-R and CGL2017-84625-C2-2-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
How to cite: Vidal-Abarca Gutiérrez, M. R., Martínez-Salvador, A., Conesa-García, C., Suárez-Alonso, M. L., Alonso-Sarria, F., Pérez-Cutillas, P., and Gomáriz-Castillo, F. J.: Effects of vegetation as an ecosystem service on the changes in runoff and sediment yield in a Mediterranean semi-arid basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4239, https://doi.org/10.5194/egusphere-egu21-4239, 2021.
EGU21-7882 | vPICO presentations | GM1.2
How spatial vegetation distribution affects soil erosion and sediment transportMalte Kuegler, Thomas Hoffmann, Jana Eichel, Lothar Schrott, and Juergen Schmidt
There are a multitude of factors that affect soil erosion and the process of sediment movement. One particular factor known to have a considerable impact is vegetation coverage within catchment areas. Previous studies have examined the impact of vegetation cover on erosion. However, there is a lack of research on how the spatial distribution of vegetation influences erosion rates.
A greater understanding of hillslope erosion is fundamental in modelling previous and future topographic changes under various climate conditions. Here, the physical based erosion model EROSION 3D © is used to evaluate the impact of a variety of vegetation patterns and degrees of vegetation cover on sediment erosion and transport. The model was applied on a natural catchment in La Campana (Central Chile). For this purpose, three different vegetation patterns were created: (i) random distribution, (ii) water-dependent distribution (TWIR) and (iii) banded vegetation pattern distribution. Additional to this, the areas covered by vegetation generated in the first step were expanded by steps of 10% [0...100%]. The Erosion3D © model then was applied on all vegetation patterns and degrees of cover.
Our results show an initial increase of soil erosion with increasing plant coverage within the catchment up to a certain cover threshold ranging between 10 and 40%. At larger vegetation cover soil erosion rates decline. The strength of increase and decline, as well as the cover-threshold is strongly conditioned by the spatial vegetation pattern. In the light of this, future research should pay particular attention to the properties of the plants and their distribution, not solely on the amount of biomass within catchment areas.
How to cite: Kuegler, M., Hoffmann, T., Eichel, J., Schrott, L., and Schmidt, J.: How spatial vegetation distribution affects soil erosion and sediment transport, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7882, https://doi.org/10.5194/egusphere-egu21-7882, 2021.
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There are a multitude of factors that affect soil erosion and the process of sediment movement. One particular factor known to have a considerable impact is vegetation coverage within catchment areas. Previous studies have examined the impact of vegetation cover on erosion. However, there is a lack of research on how the spatial distribution of vegetation influences erosion rates.
A greater understanding of hillslope erosion is fundamental in modelling previous and future topographic changes under various climate conditions. Here, the physical based erosion model EROSION 3D © is used to evaluate the impact of a variety of vegetation patterns and degrees of vegetation cover on sediment erosion and transport. The model was applied on a natural catchment in La Campana (Central Chile). For this purpose, three different vegetation patterns were created: (i) random distribution, (ii) water-dependent distribution (TWIR) and (iii) banded vegetation pattern distribution. Additional to this, the areas covered by vegetation generated in the first step were expanded by steps of 10% [0...100%]. The Erosion3D © model then was applied on all vegetation patterns and degrees of cover.
Our results show an initial increase of soil erosion with increasing plant coverage within the catchment up to a certain cover threshold ranging between 10 and 40%. At larger vegetation cover soil erosion rates decline. The strength of increase and decline, as well as the cover-threshold is strongly conditioned by the spatial vegetation pattern. In the light of this, future research should pay particular attention to the properties of the plants and their distribution, not solely on the amount of biomass within catchment areas.
How to cite: Kuegler, M., Hoffmann, T., Eichel, J., Schrott, L., and Schmidt, J.: How spatial vegetation distribution affects soil erosion and sediment transport, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7882, https://doi.org/10.5194/egusphere-egu21-7882, 2021.
EGU21-10183 * | vPICO presentations | GM1.2 | Highlight
Estimating the global geomorphological importance of ants in the AnthropoceneHeather Viles, Andrew Goudie, and Alice Goudie
Ants are active, numerous and widespread across most landscapes on Earth. They are known to be geomorphologically important, through a range of activities (such as production of galleries and mounds) by which they move and store sediment both above and below ground. They also co-exist and interact with a wide range of other geomorphologically-active organisms, sometimes resulting in complex influences on the landscape (as ant mounds can influence soils and plant biodiversity, for example). Human impacts in the Anthropocene are having direct and indirect impacts on the geomorphological importance of ants – through species invasions, climate change etc. A geolocated database of over 100 studies, covering more than 60 ant species, carried out in Europe, Africa, South America, southern Africa, USA and Australia, is used to produce some estimates of the global impacts of ants within the Anthropocene, including a first order estimate of 7.5 – 10 Gt sediment moved per year by ants across the land surface.
How to cite: Viles, H., Goudie, A., and Goudie, A.: Estimating the global geomorphological importance of ants in the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10183, https://doi.org/10.5194/egusphere-egu21-10183, 2021.
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Ants are active, numerous and widespread across most landscapes on Earth. They are known to be geomorphologically important, through a range of activities (such as production of galleries and mounds) by which they move and store sediment both above and below ground. They also co-exist and interact with a wide range of other geomorphologically-active organisms, sometimes resulting in complex influences on the landscape (as ant mounds can influence soils and plant biodiversity, for example). Human impacts in the Anthropocene are having direct and indirect impacts on the geomorphological importance of ants – through species invasions, climate change etc. A geolocated database of over 100 studies, covering more than 60 ant species, carried out in Europe, Africa, South America, southern Africa, USA and Australia, is used to produce some estimates of the global impacts of ants within the Anthropocene, including a first order estimate of 7.5 – 10 Gt sediment moved per year by ants across the land surface.
How to cite: Viles, H., Goudie, A., and Goudie, A.: Estimating the global geomorphological importance of ants in the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10183, https://doi.org/10.5194/egusphere-egu21-10183, 2021.
EGU21-2715 | vPICO presentations | GM1.2 | Highlight
Identifying causal links between tectono-geomorphic processes and biodiversity with a coupled landscape-biodiversity evolution modelHelen Beeson, Sean Willett, and Loïc Pellissier
Landscapes and their associated ecosystems coevolve over geologic time. Correlative approaches have elucidated the importance of topographic diversity and tectonic history but have not identified specific causal links between tectono-geomorphic processes and biodiversity metrics. To address this issue, we coupled the numerical landscape evolution model DAC (Divide and Capture) with a mechanistic model for biodiversity that simulates dispersal, allopatric speciation, and extinction to develop hypothetical biological signatures of different functional groups to a variety of landscape histories. In our coupled model, DAC-BIO, suitable habitat for terrestrial species is defined using a combination of elevation, slope, and aspect, which are measured at sub-grid scale from the simulated landscape and meant to represent more complex physical parameters such as temperature, precipitation, soil properties, and hydrologic environment. In addition to habitability requirements, species are assigned dispersal characteristics (rate and ability to cross uninhabitable terrain) and speciation rate (isolation time needed to form new species). We test whether distinct trends in the size and number of contiguous habitat patches emerge in response to various tectono-geomorphic processes, including a step change in uplift rate, a shift from uniform uplift to an uplift gradient, steady shortening (horizontal advection), and escarpment retreat. We find that these tectono-geomorphic processes do yield distinct trends in the size and number of habitat patches and that the resulting changes in habitat connectivity across the landscape leaves distinct biological signatures in diversification rates, species richness, and endemic richness.
How to cite: Beeson, H., Willett, S., and Pellissier, L.: Identifying causal links between tectono-geomorphic processes and biodiversity with a coupled landscape-biodiversity evolution model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2715, https://doi.org/10.5194/egusphere-egu21-2715, 2021.
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Landscapes and their associated ecosystems coevolve over geologic time. Correlative approaches have elucidated the importance of topographic diversity and tectonic history but have not identified specific causal links between tectono-geomorphic processes and biodiversity metrics. To address this issue, we coupled the numerical landscape evolution model DAC (Divide and Capture) with a mechanistic model for biodiversity that simulates dispersal, allopatric speciation, and extinction to develop hypothetical biological signatures of different functional groups to a variety of landscape histories. In our coupled model, DAC-BIO, suitable habitat for terrestrial species is defined using a combination of elevation, slope, and aspect, which are measured at sub-grid scale from the simulated landscape and meant to represent more complex physical parameters such as temperature, precipitation, soil properties, and hydrologic environment. In addition to habitability requirements, species are assigned dispersal characteristics (rate and ability to cross uninhabitable terrain) and speciation rate (isolation time needed to form new species). We test whether distinct trends in the size and number of contiguous habitat patches emerge in response to various tectono-geomorphic processes, including a step change in uplift rate, a shift from uniform uplift to an uplift gradient, steady shortening (horizontal advection), and escarpment retreat. We find that these tectono-geomorphic processes do yield distinct trends in the size and number of habitat patches and that the resulting changes in habitat connectivity across the landscape leaves distinct biological signatures in diversification rates, species richness, and endemic richness.
How to cite: Beeson, H., Willett, S., and Pellissier, L.: Identifying causal links between tectono-geomorphic processes and biodiversity with a coupled landscape-biodiversity evolution model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2715, https://doi.org/10.5194/egusphere-egu21-2715, 2021.
GM1.3 – Visages of geodiversity: time-spatial scales, uncertainty of assessments, promotional activities
EGU21-15619 | vPICO presentations | GM1.3 | Highlight
Challenges in the development of the geodiversity conceptJosé Brilha
The concept of geodiversity, despite being in use for almost 30 years, still has little impact on society. It is not easy to explain the reason for this dissociation, considering that the elements that constitute geodiversity are intrinsically part of nature, play an essential role in ecosystem services and, consequently, in human well-being.
During the last decade we have seen a great development in the interest of the geoscientific community in this subject, represented by the increase in the publication of papers and doctoral and master theses all over the world. One of the main challenges is now to transpose all this scientific knowledge into society. Obviously, theoretical and conceptual discussions about geodiversity are an integral part of science and must continue, but if we want that society recognizes the importance and value of geodiversity, we must be able to demonstrate clearly how geodiversity can help to solve some of the problems we face today.
Among other priorities, the geoscientific community has to be able to demonstrate in an structured way:
- The importance of geodiversity in implementing nature conservation actions and its direct relationship with biodiversity;
- The contribution of geodiversity for ecosystems restoration and its accounting as part of natural capital;
- The need to quantify the role of geodiversity in ecosystem services;
- The urgency of make environmental impact assessments including all possible effects that may affect geodiversity elements and processes;
- The importance of integrate the concept of geodiversity in pre-university education curricula;
- That the information and environmental interpretation provided to visitors of protected areas and other conservation areas should always include geodiversity.
Once the importance of geodiversity is fully recognized by policy-makers, managers, and the society in general, the fulfilment of the UN Sustainable Development Goals will be for sure closer than it is today.
How to cite: Brilha, J.: Challenges in the development of the geodiversity concept, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15619, https://doi.org/10.5194/egusphere-egu21-15619, 2021.
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The concept of geodiversity, despite being in use for almost 30 years, still has little impact on society. It is not easy to explain the reason for this dissociation, considering that the elements that constitute geodiversity are intrinsically part of nature, play an essential role in ecosystem services and, consequently, in human well-being.
During the last decade we have seen a great development in the interest of the geoscientific community in this subject, represented by the increase in the publication of papers and doctoral and master theses all over the world. One of the main challenges is now to transpose all this scientific knowledge into society. Obviously, theoretical and conceptual discussions about geodiversity are an integral part of science and must continue, but if we want that society recognizes the importance and value of geodiversity, we must be able to demonstrate clearly how geodiversity can help to solve some of the problems we face today.
Among other priorities, the geoscientific community has to be able to demonstrate in an structured way:
- The importance of geodiversity in implementing nature conservation actions and its direct relationship with biodiversity;
- The contribution of geodiversity for ecosystems restoration and its accounting as part of natural capital;
- The need to quantify the role of geodiversity in ecosystem services;
- The urgency of make environmental impact assessments including all possible effects that may affect geodiversity elements and processes;
- The importance of integrate the concept of geodiversity in pre-university education curricula;
- That the information and environmental interpretation provided to visitors of protected areas and other conservation areas should always include geodiversity.
Once the importance of geodiversity is fully recognized by policy-makers, managers, and the society in general, the fulfilment of the UN Sustainable Development Goals will be for sure closer than it is today.
How to cite: Brilha, J.: Challenges in the development of the geodiversity concept, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15619, https://doi.org/10.5194/egusphere-egu21-15619, 2021.
EGU21-15820 | vPICO presentations | GM1.3
Geodiversity, Geoheritage, Geoconservation: a semantic challengeAlizia Mantovani, Vincenzo Lombardo, and Marco Giardino
The concept of geoheritage took more and more relevance since the International Conference of Protection of Geological Heritage in 1991 (Martini, 1994).
During these 30 years, many authors have been proposing their definitions of geoheritage. The analysis of these definitions highlights how the geoheritage concept is deeply connected with geodiversity and geoconservation. All the definitions tend to select geoheritage among the geodiversity elements that are worthy of inclusion into the geoconservation programs because of their value for humanity. The “relevance for humanity”, however, seems to diverge in the several definitions, in what are the values and the qualities that a geological feature should possess to be considered part of geological heritage. For example, the list of values proposed by Shaples (2002), including tourism and sense of place, differs from the list proposed by Brilha (2016), including values as economic and functional, and they both differ from the geosystem services approach by Gray (2013), where relevant values are also provisioning and regulation. Lately, Brilha (2018) stated that only the scientific value is a condition to include a geologic feature in the geologic heritage category. However, the definition of what this “scientific value” represents is not clear, as for the other values of the different lists provided by the various authors.
The result of this variety of definitions and qualities raises a high level of ambiguity, with the result that some geological features may be considered geoheritage by one author and not by another author.
The aim of this presentation is to analyze the definitions of geodiversity geoheritage and geoconservation and address the differences and similarities with a semantic approach. This is the first step of a wider research: we will address the state of the art to pursue a semantic characterization of definitions and their encoding into an ontological, machine-readable approach, with the aim to reduce the level of ambiguity of the above cited concepts. This research can lead to improve the knowledge about geodiversity and geoheritage and increase the transparency in the decision process for what concerns programs of geoconservation and institution of geosites or geoparks.
References
Brilha, J., 2016. Inventory and Quantitative Assessment of Geosites and Geodiversity Sites: a Review. Geoheritage 8, 119–134. https://doi.org/10.1007/s12371-014-0139-3
Gray, M., 2013. Geodiversity: Valuing and Conserving Abiotic Nature, 2nd ed. Wiley Blackwell, Chichester, UK.
Martini, G. (Ed.), 1994. Actes du Premier Symposium international sur la protection du patrimoine géologique: Digne-les-Bains, 11-16 juin 1991. Sociètè Gèologique de France, Paris.
Sharples, Chris. (2002). Concepts and principles of geoconservation.
How to cite: Mantovani, A., Lombardo, V., and Giardino, M.: Geodiversity, Geoheritage, Geoconservation: a semantic challenge, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15820, https://doi.org/10.5194/egusphere-egu21-15820, 2021.
The concept of geoheritage took more and more relevance since the International Conference of Protection of Geological Heritage in 1991 (Martini, 1994).
During these 30 years, many authors have been proposing their definitions of geoheritage. The analysis of these definitions highlights how the geoheritage concept is deeply connected with geodiversity and geoconservation. All the definitions tend to select geoheritage among the geodiversity elements that are worthy of inclusion into the geoconservation programs because of their value for humanity. The “relevance for humanity”, however, seems to diverge in the several definitions, in what are the values and the qualities that a geological feature should possess to be considered part of geological heritage. For example, the list of values proposed by Shaples (2002), including tourism and sense of place, differs from the list proposed by Brilha (2016), including values as economic and functional, and they both differ from the geosystem services approach by Gray (2013), where relevant values are also provisioning and regulation. Lately, Brilha (2018) stated that only the scientific value is a condition to include a geologic feature in the geologic heritage category. However, the definition of what this “scientific value” represents is not clear, as for the other values of the different lists provided by the various authors.
The result of this variety of definitions and qualities raises a high level of ambiguity, with the result that some geological features may be considered geoheritage by one author and not by another author.
The aim of this presentation is to analyze the definitions of geodiversity geoheritage and geoconservation and address the differences and similarities with a semantic approach. This is the first step of a wider research: we will address the state of the art to pursue a semantic characterization of definitions and their encoding into an ontological, machine-readable approach, with the aim to reduce the level of ambiguity of the above cited concepts. This research can lead to improve the knowledge about geodiversity and geoheritage and increase the transparency in the decision process for what concerns programs of geoconservation and institution of geosites or geoparks.
References
Brilha, J., 2016. Inventory and Quantitative Assessment of Geosites and Geodiversity Sites: a Review. Geoheritage 8, 119–134. https://doi.org/10.1007/s12371-014-0139-3
Gray, M., 2013. Geodiversity: Valuing and Conserving Abiotic Nature, 2nd ed. Wiley Blackwell, Chichester, UK.
Martini, G. (Ed.), 1994. Actes du Premier Symposium international sur la protection du patrimoine géologique: Digne-les-Bains, 11-16 juin 1991. Sociètè Gèologique de France, Paris.
Sharples, Chris. (2002). Concepts and principles of geoconservation.
How to cite: Mantovani, A., Lombardo, V., and Giardino, M.: Geodiversity, Geoheritage, Geoconservation: a semantic challenge, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15820, https://doi.org/10.5194/egusphere-egu21-15820, 2021.
EGU21-7427 | vPICO presentations | GM1.3
Scale and Value: Challenges in the assessment and representation of geodiversity in AustraliaMelinda McHenry
Though interpretations of the concept of geodiversity vary widely between the prominent researchers and practitioners of Australia, most agree that the definition is inclusive of abiotic elements (which can be detected spatially and assessed quantitatively), and their associated values (which can be used in reserve system planning, geotourism and to relate culture and nature to elements and functions). Challenges in Australian geodiversity assessment and representation are three-fold - there is lack of recognition of the concept across the nation, spatial datasets are incomplete or inadequate in some regions, and the spatial extent of some elements extends hundreds of kilometres whilst other potentially equally-significant elements occur at scales of tens of meters.
In this presentation, I present three case studies of Australian geodiversity. I first explore a regional interpretation of geodiversity, in a spatially-heterogenous protected area in Tasmania - a place that has myriad unique superlative natural values. I demonstrate that the delineation between elements of geodiversity is supported by a geological framework, that facilitates adequate rank comparisons of similar landforms and/or geological types across variable topography and vegetation communities. I then demonstrate the challenges associated with values-based assessment of geodiversity at this scale - that nearly all elements become regionally significant, there are many singular examples that cannot be adequately compared, and that the additional values associated with superlative landform elements may skew the spatial expression of more scientifically significant forms.
I then present two examples of state (similarity 'provincial') 'geodiversity site' (sensu Brilha 2016) inventories. One is extensively populated, is backed by expertise and universally-accepted criteria that dates back to the founding notions of geodiversity, but nominations are ad hoc and therefore a spatially-systematic ranked system has not been used. Conversely, in the other state example, inventory are systematically allocated on the basis of pre-established criteria - but this state is inherently far less spatially geodiverse than the former example, leading to a situation where the inventory entries of the latter would not be considered significant enough to warrant listing in the former.
Finally, I present some upcoming future challenges with national-level geodiversity assessment. I show the spatial extent and granularity of our four key national datasets (soils, geology, landform, topography). I present new data that shows the values associated with geodiversity elements that are recognised in IUCNIa-III reserve management plans across Australia. I demonstrate how the comparative dearth of spatial element complexity on the Australian mainland is at odds with the immensely heterogeneous state of Tasmania, and how this may in part have influenced prior thinking regarding the concept and its inherent value to conservation and society.
The 'Australian Geodiversity Assessment Challenge' raises questions about scale, territory, value, precision and representativeness - all of which are likely to be consistent with attempts to create a unified global geodiversity index or assessment approach. It is hoped that this presentation stimulates discussion among members, and informs the debate on the ways in which geodiversity elements and values can be evaluated at a range of spatial scales.
How to cite: McHenry, M.: Scale and Value: Challenges in the assessment and representation of geodiversity in Australia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7427, https://doi.org/10.5194/egusphere-egu21-7427, 2021.
Though interpretations of the concept of geodiversity vary widely between the prominent researchers and practitioners of Australia, most agree that the definition is inclusive of abiotic elements (which can be detected spatially and assessed quantitatively), and their associated values (which can be used in reserve system planning, geotourism and to relate culture and nature to elements and functions). Challenges in Australian geodiversity assessment and representation are three-fold - there is lack of recognition of the concept across the nation, spatial datasets are incomplete or inadequate in some regions, and the spatial extent of some elements extends hundreds of kilometres whilst other potentially equally-significant elements occur at scales of tens of meters.
In this presentation, I present three case studies of Australian geodiversity. I first explore a regional interpretation of geodiversity, in a spatially-heterogenous protected area in Tasmania - a place that has myriad unique superlative natural values. I demonstrate that the delineation between elements of geodiversity is supported by a geological framework, that facilitates adequate rank comparisons of similar landforms and/or geological types across variable topography and vegetation communities. I then demonstrate the challenges associated with values-based assessment of geodiversity at this scale - that nearly all elements become regionally significant, there are many singular examples that cannot be adequately compared, and that the additional values associated with superlative landform elements may skew the spatial expression of more scientifically significant forms.
I then present two examples of state (similarity 'provincial') 'geodiversity site' (sensu Brilha 2016) inventories. One is extensively populated, is backed by expertise and universally-accepted criteria that dates back to the founding notions of geodiversity, but nominations are ad hoc and therefore a spatially-systematic ranked system has not been used. Conversely, in the other state example, inventory are systematically allocated on the basis of pre-established criteria - but this state is inherently far less spatially geodiverse than the former example, leading to a situation where the inventory entries of the latter would not be considered significant enough to warrant listing in the former.
Finally, I present some upcoming future challenges with national-level geodiversity assessment. I show the spatial extent and granularity of our four key national datasets (soils, geology, landform, topography). I present new data that shows the values associated with geodiversity elements that are recognised in IUCNIa-III reserve management plans across Australia. I demonstrate how the comparative dearth of spatial element complexity on the Australian mainland is at odds with the immensely heterogeneous state of Tasmania, and how this may in part have influenced prior thinking regarding the concept and its inherent value to conservation and society.
The 'Australian Geodiversity Assessment Challenge' raises questions about scale, territory, value, precision and representativeness - all of which are likely to be consistent with attempts to create a unified global geodiversity index or assessment approach. It is hoped that this presentation stimulates discussion among members, and informs the debate on the ways in which geodiversity elements and values can be evaluated at a range of spatial scales.
How to cite: McHenry, M.: Scale and Value: Challenges in the assessment and representation of geodiversity in Australia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7427, https://doi.org/10.5194/egusphere-egu21-7427, 2021.
EGU21-12338 | vPICO presentations | GM1.3
Geodiversity of RewildingKenneth F. Rijsdijk, Amalia Llano, Perry Cornelissen, Ashleigh Campbell, Stijn de Boer, Lukas P. Struiksma, Franciska T. de Vries, and A.C. Harry Seijmonsbergen
Rewilding is a novel way of managing nature reserves that involves minimal management with the aim to promote self-sustaining provisioning of ecosystem services. Trophic rewilding is an approach whereby a reserve facilitates both large herbivores such as bison and deer and top predators such as wolfs and bears. A famous example of trophic rewilding is Yellow Stone National Park (8983 km2) in the USA, this mountainous landscape hosts both large herbivores and large predators. In contrast, in The Netherlands the Oostvaardersplassen (55 km2) is a flat man-made marshland, hosting domestic large herbivores such as red deers and horses without large predators. The success of these rewilding schemes is generally quantitatively evaluated against biodiversity metrics, i.e. the increase of plant or bird species richness in an area. The role of the components in geodiversity that promote or demote success is underexposed. Therefore, we aim to investigate how the interaction between large herbivores and predators shape the landscape, in particular how they affect the geodiversity by changing the rate and extent of surface processes such as erosion at fine scales, the dynamics of floodplain morphology on broad scales, and the altering of soil physical and chemical properties. It has become apparent that the changes in components of geodiversity depend, amongst others, on the total number of large herbivores in an area. More grazers, for example, result in lower diversity of vegetation structural types, more compacted soils and increased erosion. Therefore, changes in grazer densities may alter the quality and areal extent of geodiversity components at multiple scales. Geodiversity components may thus affect the way large herbivores use and interact with the abiotic environment in reserves. For example, a topographically diverse landscape may host localities to shelter against harsh weather conditions, and function as safe spots against predators. Although the practise of rewilding has been implemented for several decades, it is not clear to what extent geodiversity influences rewilding success. Here, we evaluate how components of geodiversity affects rewilding success against an independent success metric, and we assess in what way geodiversity may help to identify the success or the limiting factors of potential rewilding reserves. To do this we use openly available thematic digitized spatial data to calculate a geodiversity index that includes geomorphology, topographic openness, roughness and soil diversity. We use an ArcGIS Pro environment of selected nature reserves that are managed under a rewilding regime. We include change analyses of multi temporal satellite and aerial imagery in combination with field measurements to assess how geodiversity components influence rewilding success. Ultimately, we design a geodiversity-based suitability workflow to evaluate potential successful rewilding reserves for highly fragmented landscapes such as in North Western Europe.
How to cite: Rijsdijk, K. F., Llano, A., Cornelissen, P., Campbell, A., de Boer, S., Struiksma, L. P., de Vries, F. T., and Seijmonsbergen, A. C. H.: Geodiversity of Rewilding, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12338, https://doi.org/10.5194/egusphere-egu21-12338, 2021.
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Rewilding is a novel way of managing nature reserves that involves minimal management with the aim to promote self-sustaining provisioning of ecosystem services. Trophic rewilding is an approach whereby a reserve facilitates both large herbivores such as bison and deer and top predators such as wolfs and bears. A famous example of trophic rewilding is Yellow Stone National Park (8983 km2) in the USA, this mountainous landscape hosts both large herbivores and large predators. In contrast, in The Netherlands the Oostvaardersplassen (55 km2) is a flat man-made marshland, hosting domestic large herbivores such as red deers and horses without large predators. The success of these rewilding schemes is generally quantitatively evaluated against biodiversity metrics, i.e. the increase of plant or bird species richness in an area. The role of the components in geodiversity that promote or demote success is underexposed. Therefore, we aim to investigate how the interaction between large herbivores and predators shape the landscape, in particular how they affect the geodiversity by changing the rate and extent of surface processes such as erosion at fine scales, the dynamics of floodplain morphology on broad scales, and the altering of soil physical and chemical properties. It has become apparent that the changes in components of geodiversity depend, amongst others, on the total number of large herbivores in an area. More grazers, for example, result in lower diversity of vegetation structural types, more compacted soils and increased erosion. Therefore, changes in grazer densities may alter the quality and areal extent of geodiversity components at multiple scales. Geodiversity components may thus affect the way large herbivores use and interact with the abiotic environment in reserves. For example, a topographically diverse landscape may host localities to shelter against harsh weather conditions, and function as safe spots against predators. Although the practise of rewilding has been implemented for several decades, it is not clear to what extent geodiversity influences rewilding success. Here, we evaluate how components of geodiversity affects rewilding success against an independent success metric, and we assess in what way geodiversity may help to identify the success or the limiting factors of potential rewilding reserves. To do this we use openly available thematic digitized spatial data to calculate a geodiversity index that includes geomorphology, topographic openness, roughness and soil diversity. We use an ArcGIS Pro environment of selected nature reserves that are managed under a rewilding regime. We include change analyses of multi temporal satellite and aerial imagery in combination with field measurements to assess how geodiversity components influence rewilding success. Ultimately, we design a geodiversity-based suitability workflow to evaluate potential successful rewilding reserves for highly fragmented landscapes such as in North Western Europe.
How to cite: Rijsdijk, K. F., Llano, A., Cornelissen, P., Campbell, A., de Boer, S., Struiksma, L. P., de Vries, F. T., and Seijmonsbergen, A. C. H.: Geodiversity of Rewilding, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12338, https://doi.org/10.5194/egusphere-egu21-12338, 2021.
EGU21-13977 | vPICO presentations | GM1.3 | Highlight
Initiative to establish the International Geodiversity DayZbigniew Zwoliński, Jose Brilha, Murray Gray, and Jack Matthews
On May 22, 2020, when International Biodiversity Day was celebrated, Murray Gray and Zbigniew Zwoliński independently wrote an email to José Brilha with a proposal to make efforts to establish the International Geodiversity Day (IGD). This was on the eve of the Oxford Geoheritage Virtual Conference (OxGVC) launch. Therefore, at the end of the conference, a declaration of establishing the IGD was prepared, which was supported by over 600 participants from over 60 countries. Virtual PICO presents further and ongoing scientific, organizational and diplomatic efforts to proclaim the IGD: starting from the Oxford Declaration, through letters of support from 108 individuals and international and national professional earth science nature conservation organizations and the International Union of Geological Sciences to Natural Sciences Sector – Division for Earth and Ecological Sciences UNESCO and Executive Board of UNESCO.
The proclamation of an International Geodiversity Day would provide an annual reminder of the essential role of geodiversity for human well-being. It provides the foundations and habitats for all living things. It is the source of materials that build our towns and cities; it provides our energy resources, including renewable energy and the materials mined to manufacture wind turbines and solar panels; it allows us to bury our waste, provides us with freshwater and attenuates our pollution; it helps us to understand and predict natural hazards, it inspires our artists and provides us with incredible landscapes from mountains to coasts. Geodiversity gives us evidence of past climate and landscape changes and their causes, and therefore helps us to understand and plan for the impacts of future environmental changes.
How to cite: Zwoliński, Z., Brilha, J., Gray, M., and Matthews, J.: Initiative to establish the International Geodiversity Day, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13977, https://doi.org/10.5194/egusphere-egu21-13977, 2021.
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On May 22, 2020, when International Biodiversity Day was celebrated, Murray Gray and Zbigniew Zwoliński independently wrote an email to José Brilha with a proposal to make efforts to establish the International Geodiversity Day (IGD). This was on the eve of the Oxford Geoheritage Virtual Conference (OxGVC) launch. Therefore, at the end of the conference, a declaration of establishing the IGD was prepared, which was supported by over 600 participants from over 60 countries. Virtual PICO presents further and ongoing scientific, organizational and diplomatic efforts to proclaim the IGD: starting from the Oxford Declaration, through letters of support from 108 individuals and international and national professional earth science nature conservation organizations and the International Union of Geological Sciences to Natural Sciences Sector – Division for Earth and Ecological Sciences UNESCO and Executive Board of UNESCO.
The proclamation of an International Geodiversity Day would provide an annual reminder of the essential role of geodiversity for human well-being. It provides the foundations and habitats for all living things. It is the source of materials that build our towns and cities; it provides our energy resources, including renewable energy and the materials mined to manufacture wind turbines and solar panels; it allows us to bury our waste, provides us with freshwater and attenuates our pollution; it helps us to understand and predict natural hazards, it inspires our artists and provides us with incredible landscapes from mountains to coasts. Geodiversity gives us evidence of past climate and landscape changes and their causes, and therefore helps us to understand and plan for the impacts of future environmental changes.
How to cite: Zwoliński, Z., Brilha, J., Gray, M., and Matthews, J.: Initiative to establish the International Geodiversity Day, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13977, https://doi.org/10.5194/egusphere-egu21-13977, 2021.
EGU21-13170 | vPICO presentations | GM1.3
The Geological Index of the Scottish Caledonides northwest of the Highland Boundary FaultAlex G Neches
The quantification and mapping of geodiversity have gained more interest in recent years due to practical application in natural resource management and conservation. The Geological Index (IGeo) represents the quantitative expression of geological features and is part of a broader Geodiversity Index (IGeodiv), which also includes geomorphological, pedological, paleontological and hydrological elements.
In Scotland, the area delimited by the Moine Thrust Zone to the northwest and the Highland Boundary Fault to the southeast represents a fragment of the Caledonian orogenic belt that extends across parts of North America, Greenland and Scandinavia. It includes the Highlands, most of the Inner Hebrides and the islands of Orkney and Shetland. The area is underlain by two tectonic blocks – the Northern Highlands Terrane and the Grampian Terrane – separated by a major strike-slip fault, the Great Glen. Both blocks consist of an Archaean-Paleoproterozoic basement covered by the Neoproterozoic metamorphic suites of the Moine and Dalradian Supergroups, together with a series of magmatic intrusions and other rocks of late Precambrian and Phanerozoic age.
The IGeo was obtained from lithostratigraphic and lithodemic units, mapped at group and suite/complex level respectively, major geologic contacts and faults and minor igneous intrusions from the British Geological Survey 1:625k digital datasets. These were reclassified and analyzed using QGIS and ArcGIS software.
The results show overall medium and high values of IGeo, with regional variations and well-individualized areas of very high and very low values. Conspicuous transitions between extremes are observed at the north and south edges of the study area.
High IGeo values occur in five major areas across the mainland: 1). on the north coast, which exhibits small outcrops of varied lithologies; 2). in the northeast Grampian Mountains, where the deformed Dalradian rocks are intruded by the Cairngorms suite of the Newer Granites; 3). along the Great Glen, the meeting place of adjacent tectonic blocks; 4). in the Firth of Lorne area and further inland, where Neoproterozoic and Paleozoic rocks come into contact with more recent Cenozoic rocks of the Hebridean Province; 5). at the southern tip of the Kintyre Peninsula that contains isolated exposures of rocks characteristic of the nearby Midland Valley.
Low IGeo values are encountered in three major areas of the mainland: 1). southeast of the Moine Thrust Zone, an area occupied by the oldest Moine group; 2). in the Pentland Firth area that consists of the Old Red Sandstone Supergroup; 3). in the Firth of Clyde area and further inland, around the main outcrop of the youngest Dalradian group.
Offshore, the islands of Orkney and Shetland have IGeo values at opposite ends of the spectrum. The first are made up of a monotonous sedimentary cover. The latter comprise a mosaic of rocks of Precambrian and early Phanerozoic age.
How to cite: Neches, A. G.: The Geological Index of the Scottish Caledonides northwest of the Highland Boundary Fault, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13170, https://doi.org/10.5194/egusphere-egu21-13170, 2021.
The quantification and mapping of geodiversity have gained more interest in recent years due to practical application in natural resource management and conservation. The Geological Index (IGeo) represents the quantitative expression of geological features and is part of a broader Geodiversity Index (IGeodiv), which also includes geomorphological, pedological, paleontological and hydrological elements.
In Scotland, the area delimited by the Moine Thrust Zone to the northwest and the Highland Boundary Fault to the southeast represents a fragment of the Caledonian orogenic belt that extends across parts of North America, Greenland and Scandinavia. It includes the Highlands, most of the Inner Hebrides and the islands of Orkney and Shetland. The area is underlain by two tectonic blocks – the Northern Highlands Terrane and the Grampian Terrane – separated by a major strike-slip fault, the Great Glen. Both blocks consist of an Archaean-Paleoproterozoic basement covered by the Neoproterozoic metamorphic suites of the Moine and Dalradian Supergroups, together with a series of magmatic intrusions and other rocks of late Precambrian and Phanerozoic age.
The IGeo was obtained from lithostratigraphic and lithodemic units, mapped at group and suite/complex level respectively, major geologic contacts and faults and minor igneous intrusions from the British Geological Survey 1:625k digital datasets. These were reclassified and analyzed using QGIS and ArcGIS software.
The results show overall medium and high values of IGeo, with regional variations and well-individualized areas of very high and very low values. Conspicuous transitions between extremes are observed at the north and south edges of the study area.
High IGeo values occur in five major areas across the mainland: 1). on the north coast, which exhibits small outcrops of varied lithologies; 2). in the northeast Grampian Mountains, where the deformed Dalradian rocks are intruded by the Cairngorms suite of the Newer Granites; 3). along the Great Glen, the meeting place of adjacent tectonic blocks; 4). in the Firth of Lorne area and further inland, where Neoproterozoic and Paleozoic rocks come into contact with more recent Cenozoic rocks of the Hebridean Province; 5). at the southern tip of the Kintyre Peninsula that contains isolated exposures of rocks characteristic of the nearby Midland Valley.
Low IGeo values are encountered in three major areas of the mainland: 1). southeast of the Moine Thrust Zone, an area occupied by the oldest Moine group; 2). in the Pentland Firth area that consists of the Old Red Sandstone Supergroup; 3). in the Firth of Clyde area and further inland, around the main outcrop of the youngest Dalradian group.
Offshore, the islands of Orkney and Shetland have IGeo values at opposite ends of the spectrum. The first are made up of a monotonous sedimentary cover. The latter comprise a mosaic of rocks of Precambrian and early Phanerozoic age.
How to cite: Neches, A. G.: The Geological Index of the Scottish Caledonides northwest of the Highland Boundary Fault, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13170, https://doi.org/10.5194/egusphere-egu21-13170, 2021.
EGU21-696 | vPICO presentations | GM1.3
A quantitative assessment of geodiversity in UNESCO Global GeoparksEmma Polman, W. Daniel Kissling, and Harry Seijmonsbergen
UNESCO Global Geoparks aim to protect globally significant geoheritage and geodiversity. However, the representativeness of geodiversity in these geoparks has never been quantified in a global context. Here, we quantify geodiversity in 147 UNESCO Global Geoparks and compare the outcome to global, Asian and European geodiversity using a geodiversity index with a global coverage, based on openly available geological, soil, hydrological and topographical input data. The global geodiversity index has five categories (from very low to very high) based on the total scores of the individual geodiversity components per 10 x 10 km grid cell. In addition, we assessed the occurrence of soil types and lithology types in geoparks using global lithology and soil datasets. Our results show that total geodiversity, lithological diversity and topographical diversity were significantly higher in UNESCO Global Geoparks compared to random locations of parks, reflecting that many geoparks are located in mountainous areas where lithological and topographic diversity is high. Soil diversity and hydrological diversity were not significantly higher in geoparks compared to random areas, and 22% and 65% of all globally occurring soil types and lithology types were not represented in any geopark. This indicates that soil and hydrology features are not sufficiently represented in the criteria used to establish geoparks (which emphasize geological and geomorphological features), and that current geoparks are unevenly distributed across the world, with most of them being located in Asia and in Europe. Our results highlight important gaps in geodiversity conservation and can help to identify which areas of high soil and hydrological diversity are currently underrepresented and which soil and lithology types should be included in future efforts to improve the representativeness of UNESCO Global Geoparks.
How to cite: Polman, E., Kissling, W. D., and Seijmonsbergen, H.: A quantitative assessment of geodiversity in UNESCO Global Geoparks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-696, https://doi.org/10.5194/egusphere-egu21-696, 2021.
UNESCO Global Geoparks aim to protect globally significant geoheritage and geodiversity. However, the representativeness of geodiversity in these geoparks has never been quantified in a global context. Here, we quantify geodiversity in 147 UNESCO Global Geoparks and compare the outcome to global, Asian and European geodiversity using a geodiversity index with a global coverage, based on openly available geological, soil, hydrological and topographical input data. The global geodiversity index has five categories (from very low to very high) based on the total scores of the individual geodiversity components per 10 x 10 km grid cell. In addition, we assessed the occurrence of soil types and lithology types in geoparks using global lithology and soil datasets. Our results show that total geodiversity, lithological diversity and topographical diversity were significantly higher in UNESCO Global Geoparks compared to random locations of parks, reflecting that many geoparks are located in mountainous areas where lithological and topographic diversity is high. Soil diversity and hydrological diversity were not significantly higher in geoparks compared to random areas, and 22% and 65% of all globally occurring soil types and lithology types were not represented in any geopark. This indicates that soil and hydrology features are not sufficiently represented in the criteria used to establish geoparks (which emphasize geological and geomorphological features), and that current geoparks are unevenly distributed across the world, with most of them being located in Asia and in Europe. Our results highlight important gaps in geodiversity conservation and can help to identify which areas of high soil and hydrological diversity are currently underrepresented and which soil and lithology types should be included in future efforts to improve the representativeness of UNESCO Global Geoparks.
How to cite: Polman, E., Kissling, W. D., and Seijmonsbergen, H.: A quantitative assessment of geodiversity in UNESCO Global Geoparks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-696, https://doi.org/10.5194/egusphere-egu21-696, 2021.
EGU21-2230 | vPICO presentations | GM1.3 | Highlight
Assessment of static and dynamic geodiversity in the Sesia Val Grande UNESCO Global Geopark: constraints for a sustainable use of related abiotic ecosystem servicesCristina Viani, Luigi Perotti, Federico Tognetto, Ilaria Selvaggio, and Marco Giardino
Geodiversity includes geological, geomorphological, hydrological and soil elements and processes. By analysing geodiversity we can offer static and dynamic views of abiotic landscapes on the Earth. The current state of geodiversity includes both relict, long-term features recalling the past of our planet earth and active landforms and processes whose monitoring is a key for interpreting relationships between geosphere, biosphere and human activities. If the long term geodiversity mainly represents distribution of litho-structural “static” constrains to environmental changes, recent and active environmental features may act as dynamic “proxies” for interpreting climate change.
Aim of this work is to analyse relevant examples of both static and dynamic geodiversity within the territory of the Sesia Val Grande UNESCO Global Geopark (Western Alps, Italy), in order to assess their role as georesources and to highlight possible sustainable use of related abiotic ecosystem services, including geoheritage. Geodiversity assessment has been performed by means of creation of geothematic maps and related factors analysed for better mountain environment understanding and management.
Starting with static geodiversity we collected, analysed and interpreted lithological and structural data in order to obtain information on distribution of georesources in the study area and to create a geothematic map on landscape resistance to erosion.
Thereafter we focused on two aspects related to dynamic geodiversity and their relationships with dramatic changes of the alpine landscape: glacial evolution and fluvial processes. On one hand, valley scale geomorphological evolution has been reconstructed by means of multitemporal data (e.g.: glacial landforms maps, glacier inventories) on evidences in the Sesia Valley. Obtained information crossed with national landslide inventory allowed to identify areas of strong glacial influence on slope stability (deep-seated gravitational slope deformation and landslides due to slope debutressing). Moreover, recent glacier withdrawal results in new glacier lakes increasing the hydrogeodiversity of the area and representing important potential georesources to be used. Finally, recent alluvial event (October 2020) has been considered for its high impact in reshaping fluvial environment and effects on both infrastructures and popular geosites along the Sesia river.
Results of this work are useful for the establishment of a proper Driver-Pressure-State-Impact-Response (DPSIR) framework related to environmental issues due to global change in order to support educational activities and sustainable development of alpine “tourism hubs” included in the Sesia Val Grande UNESCO Global Geopark by the “ArcticHubs” H2020-EU.3.5.1 project.
How to cite: Viani, C., Perotti, L., Tognetto, F., Selvaggio, I., and Giardino, M.: Assessment of static and dynamic geodiversity in the Sesia Val Grande UNESCO Global Geopark: constraints for a sustainable use of related abiotic ecosystem services, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2230, https://doi.org/10.5194/egusphere-egu21-2230, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Geodiversity includes geological, geomorphological, hydrological and soil elements and processes. By analysing geodiversity we can offer static and dynamic views of abiotic landscapes on the Earth. The current state of geodiversity includes both relict, long-term features recalling the past of our planet earth and active landforms and processes whose monitoring is a key for interpreting relationships between geosphere, biosphere and human activities. If the long term geodiversity mainly represents distribution of litho-structural “static” constrains to environmental changes, recent and active environmental features may act as dynamic “proxies” for interpreting climate change.
Aim of this work is to analyse relevant examples of both static and dynamic geodiversity within the territory of the Sesia Val Grande UNESCO Global Geopark (Western Alps, Italy), in order to assess their role as georesources and to highlight possible sustainable use of related abiotic ecosystem services, including geoheritage. Geodiversity assessment has been performed by means of creation of geothematic maps and related factors analysed for better mountain environment understanding and management.
Starting with static geodiversity we collected, analysed and interpreted lithological and structural data in order to obtain information on distribution of georesources in the study area and to create a geothematic map on landscape resistance to erosion.
Thereafter we focused on two aspects related to dynamic geodiversity and their relationships with dramatic changes of the alpine landscape: glacial evolution and fluvial processes. On one hand, valley scale geomorphological evolution has been reconstructed by means of multitemporal data (e.g.: glacial landforms maps, glacier inventories) on evidences in the Sesia Valley. Obtained information crossed with national landslide inventory allowed to identify areas of strong glacial influence on slope stability (deep-seated gravitational slope deformation and landslides due to slope debutressing). Moreover, recent glacier withdrawal results in new glacier lakes increasing the hydrogeodiversity of the area and representing important potential georesources to be used. Finally, recent alluvial event (October 2020) has been considered for its high impact in reshaping fluvial environment and effects on both infrastructures and popular geosites along the Sesia river.
Results of this work are useful for the establishment of a proper Driver-Pressure-State-Impact-Response (DPSIR) framework related to environmental issues due to global change in order to support educational activities and sustainable development of alpine “tourism hubs” included in the Sesia Val Grande UNESCO Global Geopark by the “ArcticHubs” H2020-EU.3.5.1 project.
How to cite: Viani, C., Perotti, L., Tognetto, F., Selvaggio, I., and Giardino, M.: Assessment of static and dynamic geodiversity in the Sesia Val Grande UNESCO Global Geopark: constraints for a sustainable use of related abiotic ecosystem services, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2230, https://doi.org/10.5194/egusphere-egu21-2230, 2021.
EGU21-1363 | vPICO presentations | GM1.3
The use of geomorphons in geodiversity assessmentMárton Pál and Gáspár Albert
The quantification of geodiversity has become an important task for researchers just after the formulation of the definition. For ‘measuring’ the values of the physical environment, many quantitative assessment models were presented in the past decades. The common characteristic of these methods is that they use thematic (geological, geomorphological, pedological, mineralogical, palaeontological) layers/datasets to evaluate each geoscientific property of a certain sample area. These data can be printed maps or databases with geospatial reference. The geodiversity index can be produced by objectively examining and evaluating these source materials. However, in some countries, scientists lack proper datasets, or they do not have the legislative background to use them.
We propose an alternative methodology based on Pereira et al. (2013) to determine geomorphological diversity, an important subvalue of the geodiversity index. The concept of geomorphons (Jasiewicz & Stepinski, 2013) is a relatively new pattern recognition approach to classify and map landforms. Any kind of DEMs (Digital Elevation Models) can be used to produce this categorization (better resolution means a more realistic result). The algorithm uses 8-tuple pattern of the visibility neighbourhood (not necessarily immediate neighbours) to delineate terrain forms in the eight principle directions to a certain point. The result of the algorithm produces a quasi-geomorphological map with 10 relief categories: flat, summit, ridge, shoulder, spur, slope, hollow, footslope, valley and depression.
This concept can be built in the geodiversity assessment process of any area as DEMs are freely available with at least 1 arc second resolution all over the world. We have used geomorphons during the geodiversity assessment of the Bakony–Balaton UNESCO Global Geopark in Hungary. The results follow field experiences and the patterns of large-scale geomorphological maps. As geomorphons are freely available in desktop GIS software (e.g. GRASS), their use can become an objective global opportunity to quantify geomorphological diversity.
From the part of G.A. financial support was provided from the NRDI Fund of Hungary, Thematic Excellence Programme no. TKP2020-NKA-06 (National Challenges Subprogramme) funding scheme.
Jasiewicz, J., Stepinski, T. (2013): Geomorphons - a pattern recognition approach to classification and mapping of landforms. Geomorphology, vol. 182, pp. 147-156.
Pereira, D.I., Pereira, P., Brilha, J., Santos, L. (2013): Geodiversity assessment of Paraná State (Brazil): An innovative approach. Environmental Management, vol. 52, pp. 541–552.
How to cite: Pál, M. and Albert, G.: The use of geomorphons in geodiversity assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1363, https://doi.org/10.5194/egusphere-egu21-1363, 2021.
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The quantification of geodiversity has become an important task for researchers just after the formulation of the definition. For ‘measuring’ the values of the physical environment, many quantitative assessment models were presented in the past decades. The common characteristic of these methods is that they use thematic (geological, geomorphological, pedological, mineralogical, palaeontological) layers/datasets to evaluate each geoscientific property of a certain sample area. These data can be printed maps or databases with geospatial reference. The geodiversity index can be produced by objectively examining and evaluating these source materials. However, in some countries, scientists lack proper datasets, or they do not have the legislative background to use them.
We propose an alternative methodology based on Pereira et al. (2013) to determine geomorphological diversity, an important subvalue of the geodiversity index. The concept of geomorphons (Jasiewicz & Stepinski, 2013) is a relatively new pattern recognition approach to classify and map landforms. Any kind of DEMs (Digital Elevation Models) can be used to produce this categorization (better resolution means a more realistic result). The algorithm uses 8-tuple pattern of the visibility neighbourhood (not necessarily immediate neighbours) to delineate terrain forms in the eight principle directions to a certain point. The result of the algorithm produces a quasi-geomorphological map with 10 relief categories: flat, summit, ridge, shoulder, spur, slope, hollow, footslope, valley and depression.
This concept can be built in the geodiversity assessment process of any area as DEMs are freely available with at least 1 arc second resolution all over the world. We have used geomorphons during the geodiversity assessment of the Bakony–Balaton UNESCO Global Geopark in Hungary. The results follow field experiences and the patterns of large-scale geomorphological maps. As geomorphons are freely available in desktop GIS software (e.g. GRASS), their use can become an objective global opportunity to quantify geomorphological diversity.
From the part of G.A. financial support was provided from the NRDI Fund of Hungary, Thematic Excellence Programme no. TKP2020-NKA-06 (National Challenges Subprogramme) funding scheme.
Jasiewicz, J., Stepinski, T. (2013): Geomorphons - a pattern recognition approach to classification and mapping of landforms. Geomorphology, vol. 182, pp. 147-156.
Pereira, D.I., Pereira, P., Brilha, J., Santos, L. (2013): Geodiversity assessment of Paraná State (Brazil): An innovative approach. Environmental Management, vol. 52, pp. 541–552.
How to cite: Pál, M. and Albert, G.: The use of geomorphons in geodiversity assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1363, https://doi.org/10.5194/egusphere-egu21-1363, 2021.
EGU21-3081 | vPICO presentations | GM1.3
Geodiversity in the Liguria region: a preliminary GIS-based quantitative assessmentAndrea Ferrando, Francesco Faccini, Flavio Poggi, and Paola Coratza
Geodiversity is an important natural resource that must be considered in developing an effective land management strategy. In recent times there has been a great impulse on the research on geodiversity topics; particular attention has been given to geodiversity assessment methodologies, both qualitative and quantitative. The Liguria region in Northern Italy, despite its small geographic scale, encompasses a great variety of natural and cultural features of international significance. This wide variety is due to its particular geographical, geological and geomorphological conditions. In this work a first preliminary assessment of geodiversity in the Liguria region has been carried out, according to the quantitative method proposed by Melelli et al (2017). This GIS-based method uses spatial analysis techniques, taking into account five parameters: a geological index (lithology) and four morphometric indices (drainage density, roughness, slope position index and landform category), combined to obtain a total Geodiversity Index. The results show that the Liguria region is characterized by many areas with high geodiversity. The most important examples are the western Ligurian Alps, the Finalese, the Sestri-Voltaggio Zone and its surroundings, the eastern Ligurian Apennines, the Cinque Terre, which are in fact the areas with the greatest morphological and lithological variety. Most of these areas are well known by geoscientists for their significant geological and geomorphological heritage, and by the general public for their impressive landscapes. There is a correspondence between the most geodiverse areas, the main natural parks and the Natura 2000 network of protected areas, established to protect and enhance biodiversity. This suggest a link between geodiversity and biodiversity, that may be subject to further research.
How to cite: Ferrando, A., Faccini, F., Poggi, F., and Coratza, P.: Geodiversity in the Liguria region: a preliminary GIS-based quantitative assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3081, https://doi.org/10.5194/egusphere-egu21-3081, 2021.
Geodiversity is an important natural resource that must be considered in developing an effective land management strategy. In recent times there has been a great impulse on the research on geodiversity topics; particular attention has been given to geodiversity assessment methodologies, both qualitative and quantitative. The Liguria region in Northern Italy, despite its small geographic scale, encompasses a great variety of natural and cultural features of international significance. This wide variety is due to its particular geographical, geological and geomorphological conditions. In this work a first preliminary assessment of geodiversity in the Liguria region has been carried out, according to the quantitative method proposed by Melelli et al (2017). This GIS-based method uses spatial analysis techniques, taking into account five parameters: a geological index (lithology) and four morphometric indices (drainage density, roughness, slope position index and landform category), combined to obtain a total Geodiversity Index. The results show that the Liguria region is characterized by many areas with high geodiversity. The most important examples are the western Ligurian Alps, the Finalese, the Sestri-Voltaggio Zone and its surroundings, the eastern Ligurian Apennines, the Cinque Terre, which are in fact the areas with the greatest morphological and lithological variety. Most of these areas are well known by geoscientists for their significant geological and geomorphological heritage, and by the general public for their impressive landscapes. There is a correspondence between the most geodiverse areas, the main natural parks and the Natura 2000 network of protected areas, established to protect and enhance biodiversity. This suggest a link between geodiversity and biodiversity, that may be subject to further research.
How to cite: Ferrando, A., Faccini, F., Poggi, F., and Coratza, P.: Geodiversity in the Liguria region: a preliminary GIS-based quantitative assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3081, https://doi.org/10.5194/egusphere-egu21-3081, 2021.
EGU21-15464 | vPICO presentations | GM1.3
Geodiversity assessment with Crowdsourced Data and Spatial Multicriteria AnalysisAlicja Najwer, Piotr Jankowski, Zbigniew Zwoliński, and Jacek Niesterowicz
The main objective of virtual PICO is to present an approach to geodiversity assessment based on spatial multicriteria analysis (MCE) with Crowdsourced Data. Geodiversity assessment usually involves an individual expert or a group of experts who assess the value of geodiversity factors to the overall geodiversity score for a study area. The biggest objection to methods used so far is subjectivism. Responding to these objections, a crowdsourcing approach that uses an online geo-questionnaire linked with an interactive map was used.
The assessment input data comprised of seven environmental factor ratings and weights were obtained from 57 Earth science researchers worldwide. These data served as the bases for a joint assessment of geodiversity. To provide more comprehensive assessment approach for aggregating factor ratings and weights to compute an overall measure of geodiversity the weighted linear combination (WLC) method and its local version L-WLC were used. Karkonosze National Park (KNP) located in south-western Poland in the border area between Poland and the Czech Republic was chosen as a research area. Karkonosze is the highest mountain range of the Sudetes, characterised by unique geological and geomorphological values. The geodiversity of the research area was valued with regards to the reliability of assessment evaluated by means of spatially explicit uncertainty analysis. Average (AVG) and standard deviation (STD) geodiversity maps (on the basis of 57 respondent data) were computed. As a result of their cross-tabulation, a bivariate maps with average geodiversity values (AVG: low, high) and standard deviation values (STD: low, high) were created. Two such maps, one for WLC results and another for L-WLC results, were compiled and evaluated, providing a more holistic visages of final geodiversity and its uncertainty. Given that L-WLC provides a realistic assessment of geodiversity and guided by its results, the areas of high geodiversity and low uncertainty have been identified within Karkonosze range.
How to cite: Najwer, A., Jankowski, P., Zwoliński, Z., and Niesterowicz, J.: Geodiversity assessment with Crowdsourced Data and Spatial Multicriteria Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15464, https://doi.org/10.5194/egusphere-egu21-15464, 2021.
The main objective of virtual PICO is to present an approach to geodiversity assessment based on spatial multicriteria analysis (MCE) with Crowdsourced Data. Geodiversity assessment usually involves an individual expert or a group of experts who assess the value of geodiversity factors to the overall geodiversity score for a study area. The biggest objection to methods used so far is subjectivism. Responding to these objections, a crowdsourcing approach that uses an online geo-questionnaire linked with an interactive map was used.
The assessment input data comprised of seven environmental factor ratings and weights were obtained from 57 Earth science researchers worldwide. These data served as the bases for a joint assessment of geodiversity. To provide more comprehensive assessment approach for aggregating factor ratings and weights to compute an overall measure of geodiversity the weighted linear combination (WLC) method and its local version L-WLC were used. Karkonosze National Park (KNP) located in south-western Poland in the border area between Poland and the Czech Republic was chosen as a research area. Karkonosze is the highest mountain range of the Sudetes, characterised by unique geological and geomorphological values. The geodiversity of the research area was valued with regards to the reliability of assessment evaluated by means of spatially explicit uncertainty analysis. Average (AVG) and standard deviation (STD) geodiversity maps (on the basis of 57 respondent data) were computed. As a result of their cross-tabulation, a bivariate maps with average geodiversity values (AVG: low, high) and standard deviation values (STD: low, high) were created. Two such maps, one for WLC results and another for L-WLC results, were compiled and evaluated, providing a more holistic visages of final geodiversity and its uncertainty. Given that L-WLC provides a realistic assessment of geodiversity and guided by its results, the areas of high geodiversity and low uncertainty have been identified within Karkonosze range.
How to cite: Najwer, A., Jankowski, P., Zwoliński, Z., and Niesterowicz, J.: Geodiversity assessment with Crowdsourced Data and Spatial Multicriteria Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15464, https://doi.org/10.5194/egusphere-egu21-15464, 2021.
EGU21-10698 | vPICO presentations | GM1.3
Coupling GIS and Machine Learning for the quantitative assessment of geomorphodiversityLaura Melelli, Maurizio Petrelli, and Claudio De Blasio
EGU21-5176 | vPICO presentations | GM1.3
Quantifying geodiversity with alpha, beta and gamma componentsHelena Tukiainen, Janne Alahuhta, Jan Hjort, Marja Lindholm, Tuija Maliniemi, Henriikka Salminen, Henna Snåre, Maija Toivanen, Annika Vilmi, and Jani Heino
A variety of ways can be used to measure geodiversity, but no consensus on quantifying it exists to date. Most quantifications have thus far focused on the abiotic diversity of individual sites, which offers only limited views on variation of abiotic nature. It is, therefore, important to examine the between-site geodiversity, i.e., the dissimilarities of geofeatures (elements of geodiversity) between different sites. For instance, it would be interesting to recognize not only the most geodiverse sites of an area, but also the sites that have the most unique compositions of geofeatures. This extended geodiversity information could be further applied in nature conservation or land-use planning. We propose that geodiversity research would benefit from adopting the alpha, beta and gamma concepts of species diversity research to provide a more holistic framework for geodiversity assessments. In particular, the inclusion of distance metrics for measuring beta biodiversity could open new perspectives in evaluating beta geodiversity. The integration of these diversity concepts into geodiversity research would also allow a better joint understanding of biotic and abiotic diversity.
How to cite: Tukiainen, H., Alahuhta, J., Hjort, J., Lindholm, M., Maliniemi, T., Salminen, H., Snåre, H., Toivanen, M., Vilmi, A., and Heino, J.: Quantifying geodiversity with alpha, beta and gamma components, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5176, https://doi.org/10.5194/egusphere-egu21-5176, 2021.
A variety of ways can be used to measure geodiversity, but no consensus on quantifying it exists to date. Most quantifications have thus far focused on the abiotic diversity of individual sites, which offers only limited views on variation of abiotic nature. It is, therefore, important to examine the between-site geodiversity, i.e., the dissimilarities of geofeatures (elements of geodiversity) between different sites. For instance, it would be interesting to recognize not only the most geodiverse sites of an area, but also the sites that have the most unique compositions of geofeatures. This extended geodiversity information could be further applied in nature conservation or land-use planning. We propose that geodiversity research would benefit from adopting the alpha, beta and gamma concepts of species diversity research to provide a more holistic framework for geodiversity assessments. In particular, the inclusion of distance metrics for measuring beta biodiversity could open new perspectives in evaluating beta geodiversity. The integration of these diversity concepts into geodiversity research would also allow a better joint understanding of biotic and abiotic diversity.
How to cite: Tukiainen, H., Alahuhta, J., Hjort, J., Lindholm, M., Maliniemi, T., Salminen, H., Snåre, H., Toivanen, M., Vilmi, A., and Heino, J.: Quantifying geodiversity with alpha, beta and gamma components, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5176, https://doi.org/10.5194/egusphere-egu21-5176, 2021.
EGU21-693 | vPICO presentations | GM1.3 | Highlight
Exploring ocean floor geodiversity in relation to mineral resources in the Pacific OceanHarry Seijmonsbergen, Sanne Valentijn, Lisan Westerhof, and Kenneth Rijsdijk
There is a growing demand for mineral resources such as metals and rare earth elements, but global terrestrial resources are rapidly declining. Alternatively, the ocean floor provides unprecedented mining potential. However, their occurrences in relation to ocean floor geodiversity is largely unexplored. Therefore, it is unclear what the (irreversible) potential impact of future mining is on ocean floor geodiversity.
Here, we quantify the ocean floor geodiversity of the West-Pacific ocean floor and explore the distribution of three mineral resources: polymetallic sulfides, cobalt-rich ferromanganese crusts and polymetallic nodules. We developed a workflow for the calculation of a geodiversity index composed of openly available geomorphological, sediment thickness, bathymetric and derived ocean floor roughness input data in ArcGIS Pro.
Our results show a large variety in geodiversity on the West-Pacific ocean floor, ranging from very low and low geodiversity on large plateaus and in wide trenches and throughs, to high and very high geodiversity in heterogeneous, patchy environments on shelves, basins and abyssal plains. Regression analysis results indicate that polymetallic sulfides and cobalt-rich ferromanganese crusts positively correlate to the geodiversity index, while polymetallic nodules indicate a negative correlation. Further analysis will focus on refining and expanding this method to a global extent by adding ocean floor age, a possible important factor, into the geodiversity assessment.
Our findings suggest that understanding of ocean floor geodiversity can contribute to promote sustainable mining and support conservation of the ocean floor.
How to cite: Seijmonsbergen, H., Valentijn, S., Westerhof, L., and Rijsdijk, K.: Exploring ocean floor geodiversity in relation to mineral resources in the Pacific Ocean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-693, https://doi.org/10.5194/egusphere-egu21-693, 2021.
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There is a growing demand for mineral resources such as metals and rare earth elements, but global terrestrial resources are rapidly declining. Alternatively, the ocean floor provides unprecedented mining potential. However, their occurrences in relation to ocean floor geodiversity is largely unexplored. Therefore, it is unclear what the (irreversible) potential impact of future mining is on ocean floor geodiversity.
Here, we quantify the ocean floor geodiversity of the West-Pacific ocean floor and explore the distribution of three mineral resources: polymetallic sulfides, cobalt-rich ferromanganese crusts and polymetallic nodules. We developed a workflow for the calculation of a geodiversity index composed of openly available geomorphological, sediment thickness, bathymetric and derived ocean floor roughness input data in ArcGIS Pro.
Our results show a large variety in geodiversity on the West-Pacific ocean floor, ranging from very low and low geodiversity on large plateaus and in wide trenches and throughs, to high and very high geodiversity in heterogeneous, patchy environments on shelves, basins and abyssal plains. Regression analysis results indicate that polymetallic sulfides and cobalt-rich ferromanganese crusts positively correlate to the geodiversity index, while polymetallic nodules indicate a negative correlation. Further analysis will focus on refining and expanding this method to a global extent by adding ocean floor age, a possible important factor, into the geodiversity assessment.
Our findings suggest that understanding of ocean floor geodiversity can contribute to promote sustainable mining and support conservation of the ocean floor.
How to cite: Seijmonsbergen, H., Valentijn, S., Westerhof, L., and Rijsdijk, K.: Exploring ocean floor geodiversity in relation to mineral resources in the Pacific Ocean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-693, https://doi.org/10.5194/egusphere-egu21-693, 2021.
EGU21-9416 | vPICO presentations | GM1.3
Noise maps complexity in regards of environmental propertiesDavid Dellong, Florent Le Courtois, Jean-Michel Boutonnier, and Bazile G. Kinda
Maps of underwater noise generated by shipping activity became a useful tool to support international regulations on marine environments. They are used to infer the risk of impact on biodiversity. Maps are performed by 1) computing the emitted noise levels from ships, 2) propagating the acoustic signal in the environment and 3) using localized measurements to validate the results. Because of mismatches in environmental data and a limited number of measurements, noise maps remain highly uncertain.
In this work, the uncertainty of the noise maps is investigated through the potential complexity of soundscape. The acoustic signal at each receiving cell is computed from the convolution of the source of the ships by the transmission losses of the environment. Complexity is mapped by computing Shannon's entropy of the transmission losses for each receiver. High entropy areas only reflect high shipping densities and favorable acoustic propagation properties of the local environment. Low entropy areas reflect: low shipping density and/or poor acoustic propagation properties. An area with high shipping densities and poor acoustic propagation properties will still have low entropy values.
Entropy maps allow classifying areas depending on their environmental features. Thus, scenarios of uncertainty are defined. Results highlight the necessity to consider the diversity of the environmental properties in support of the production of noise maps. The methodology could help in optimizing spatial and temporal resolution of map computations, as well as optimizing acoustic monitoring strategies.
How to cite: Dellong, D., Le Courtois, F., Boutonnier, J.-M., and Kinda, B. G.: Noise maps complexity in regards of environmental properties, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9416, https://doi.org/10.5194/egusphere-egu21-9416, 2021.
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Maps of underwater noise generated by shipping activity became a useful tool to support international regulations on marine environments. They are used to infer the risk of impact on biodiversity. Maps are performed by 1) computing the emitted noise levels from ships, 2) propagating the acoustic signal in the environment and 3) using localized measurements to validate the results. Because of mismatches in environmental data and a limited number of measurements, noise maps remain highly uncertain.
In this work, the uncertainty of the noise maps is investigated through the potential complexity of soundscape. The acoustic signal at each receiving cell is computed from the convolution of the source of the ships by the transmission losses of the environment. Complexity is mapped by computing Shannon's entropy of the transmission losses for each receiver. High entropy areas only reflect high shipping densities and favorable acoustic propagation properties of the local environment. Low entropy areas reflect: low shipping density and/or poor acoustic propagation properties. An area with high shipping densities and poor acoustic propagation properties will still have low entropy values.
Entropy maps allow classifying areas depending on their environmental features. Thus, scenarios of uncertainty are defined. Results highlight the necessity to consider the diversity of the environmental properties in support of the production of noise maps. The methodology could help in optimizing spatial and temporal resolution of map computations, as well as optimizing acoustic monitoring strategies.
How to cite: Dellong, D., Le Courtois, F., Boutonnier, J.-M., and Kinda, B. G.: Noise maps complexity in regards of environmental properties, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9416, https://doi.org/10.5194/egusphere-egu21-9416, 2021.
EGU21-15071 | vPICO presentations | GM1.3
A Geomorphological Approach to Geodiversity and Geotourism in Uttarakhand Himalaya, India: A Pilot SurveyAnita Pande
Himalaya is the greatest heritage of India. The objective of this paper is to present a view of the geomorphological heritage of the Himalaya.Uttarakhand state (77°35’5”-81°2’25” E and 28°43’45”-31°8’18’’N, Area: 53,066 sq.km.) lies almost wholly within the realm of the Himalaya and is a distinct geographical entity. The state is a land of vast geological and topographic diversities and a realm with rich geo-wealth and geoheritage. Geological and geomorphological features occurring in different parts of Uttarakhand Himalaya are part of the natural assets and are precious state heritage (geoheritage), worthy of conservation. Apart from rock monuments and fossil parks, geomorphological features or geomorphosites have great potential to exert a pull on tourists. These sites have noteworthy impact on the geoscience education and research. Geotourism is growing rapidly all over the world and Himalaya region is no exception to this. To promote geotourism in the Himalayan State of Uttarakhand, comprehensive information about geomorphosites should be made available to the tourists by way of websites. For this, first a peer-reviewed state inventory of geomorphosites and their classification, mapping and assessment is required. Geodiversity in Uttarakhand State can best be understood in the form of the rise of Himalayan mountains from the bed of Tethys Sea which gave rise to four distinct tectonic units largely varying in lithology and structure. The relief was fragmented into four major morphosculptural units which signify the mountainous part of the state: viz. i. the Tethys zone or the Trans-Himalaya ii. the Greater Himalaya iii. the Lesser Himalaya and iv. the Siwalik. Apart from this mountainous region of the State, there is outlying region of the state, which incompasses : iv. Bhabhar and Tarai (a sub-montane tract) - a landscape feature along the foothills, v. Dun Valleys – valleys of tectonic origin and vi. Plains of North India - the lowest part in Uttarakhand with an altitude of 200 m. These geological units recognised on the basis of evolutionary history, stratigraphic sequences and component rock units and reveal identical topographic and climatic characteristics. These units are separated by various tectonic boundaries. Apart from geodiversity, the geomorphological diversity can be assessed in the form of towering snow peaks, awe-inspiring horned peaks with natural grandeur, widely distributed stretches of wide and fertile valleys, valleys of tectonic origin-canoe shaped longitudinal valleys, lofty snow capped peak surrounded by several small and big snowfields, glaciers and lakes, mountain passes and elevated zones packed in a series of multi-level distinctive waterfalls. Thus, being the youngest mountain of the world, this Himalayan State has geotouristic potential from the point of view of its geomorphological heritage.
Keywords: Himalaya, geodiversity , geomorphological heritage, geomorphosites, geotourism.
How to cite: Pande, A.: A Geomorphological Approach to Geodiversity and Geotourism in Uttarakhand Himalaya, India: A Pilot Survey , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15071, https://doi.org/10.5194/egusphere-egu21-15071, 2021.
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Himalaya is the greatest heritage of India. The objective of this paper is to present a view of the geomorphological heritage of the Himalaya.Uttarakhand state (77°35’5”-81°2’25” E and 28°43’45”-31°8’18’’N, Area: 53,066 sq.km.) lies almost wholly within the realm of the Himalaya and is a distinct geographical entity. The state is a land of vast geological and topographic diversities and a realm with rich geo-wealth and geoheritage. Geological and geomorphological features occurring in different parts of Uttarakhand Himalaya are part of the natural assets and are precious state heritage (geoheritage), worthy of conservation. Apart from rock monuments and fossil parks, geomorphological features or geomorphosites have great potential to exert a pull on tourists. These sites have noteworthy impact on the geoscience education and research. Geotourism is growing rapidly all over the world and Himalaya region is no exception to this. To promote geotourism in the Himalayan State of Uttarakhand, comprehensive information about geomorphosites should be made available to the tourists by way of websites. For this, first a peer-reviewed state inventory of geomorphosites and their classification, mapping and assessment is required. Geodiversity in Uttarakhand State can best be understood in the form of the rise of Himalayan mountains from the bed of Tethys Sea which gave rise to four distinct tectonic units largely varying in lithology and structure. The relief was fragmented into four major morphosculptural units which signify the mountainous part of the state: viz. i. the Tethys zone or the Trans-Himalaya ii. the Greater Himalaya iii. the Lesser Himalaya and iv. the Siwalik. Apart from this mountainous region of the State, there is outlying region of the state, which incompasses : iv. Bhabhar and Tarai (a sub-montane tract) - a landscape feature along the foothills, v. Dun Valleys – valleys of tectonic origin and vi. Plains of North India - the lowest part in Uttarakhand with an altitude of 200 m. These geological units recognised on the basis of evolutionary history, stratigraphic sequences and component rock units and reveal identical topographic and climatic characteristics. These units are separated by various tectonic boundaries. Apart from geodiversity, the geomorphological diversity can be assessed in the form of towering snow peaks, awe-inspiring horned peaks with natural grandeur, widely distributed stretches of wide and fertile valleys, valleys of tectonic origin-canoe shaped longitudinal valleys, lofty snow capped peak surrounded by several small and big snowfields, glaciers and lakes, mountain passes and elevated zones packed in a series of multi-level distinctive waterfalls. Thus, being the youngest mountain of the world, this Himalayan State has geotouristic potential from the point of view of its geomorphological heritage.
Keywords: Himalaya, geodiversity , geomorphological heritage, geomorphosites, geotourism.
How to cite: Pande, A.: A Geomorphological Approach to Geodiversity and Geotourism in Uttarakhand Himalaya, India: A Pilot Survey , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15071, https://doi.org/10.5194/egusphere-egu21-15071, 2021.
EGU21-16256 | vPICO presentations | GM1.3
Geoheritage and Potential Geotourism Sites in Spiti Valley, Himachal Pradesh, IndiaKrishnanand Krishnanand
Geoheritage are those components of geodiversity that are specifically identified as having conservation significance; that have some specific value to human society and therefore ought to be conserved, particularly if they are threatened by human activities and could therefore be lost or damaged. The Spiti valley of Himachal Pradesh, India is unique due to the presence of Tethyan sediments that are exposed and have abundance of fossils that makes it a rich and valuable geoheritage site. The research focuses upon the study of various existing tourist hot spots and potential geoheritage sites. The main objective of the study is to assess the human response (geotourism) to the diversity of existing and potential geoheritage sites in the area. The study is largely based on the field work conducted in the study area between 2014-19 in which data has been collected through structured questionnaire survey, observation and in-depth interviews through field work and SWOT analysis has been done accordingly. The locations of geoheritage sites have been marked using Global positioning System (GPS) and an overlay map has been prepared using Arc Map 10 (GIS software). Overall, the major issue is the lack of geoconservation policy and inaccessibility which needs to be addressed with better management efforts such as Fossil Park or geo-park establishment.
Key words: Geoheritage, Geotourism, Spiti Valley, Potential Geoheritage Sites, Fossil Park
How to cite: Krishnanand, K.: Geoheritage and Potential Geotourism Sites in Spiti Valley, Himachal Pradesh, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16256, https://doi.org/10.5194/egusphere-egu21-16256, 2021.
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Geoheritage are those components of geodiversity that are specifically identified as having conservation significance; that have some specific value to human society and therefore ought to be conserved, particularly if they are threatened by human activities and could therefore be lost or damaged. The Spiti valley of Himachal Pradesh, India is unique due to the presence of Tethyan sediments that are exposed and have abundance of fossils that makes it a rich and valuable geoheritage site. The research focuses upon the study of various existing tourist hot spots and potential geoheritage sites. The main objective of the study is to assess the human response (geotourism) to the diversity of existing and potential geoheritage sites in the area. The study is largely based on the field work conducted in the study area between 2014-19 in which data has been collected through structured questionnaire survey, observation and in-depth interviews through field work and SWOT analysis has been done accordingly. The locations of geoheritage sites have been marked using Global positioning System (GPS) and an overlay map has been prepared using Arc Map 10 (GIS software). Overall, the major issue is the lack of geoconservation policy and inaccessibility which needs to be addressed with better management efforts such as Fossil Park or geo-park establishment.
Key words: Geoheritage, Geotourism, Spiti Valley, Potential Geoheritage Sites, Fossil Park
How to cite: Krishnanand, K.: Geoheritage and Potential Geotourism Sites in Spiti Valley, Himachal Pradesh, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16256, https://doi.org/10.5194/egusphere-egu21-16256, 2021.
EGU21-10566 | vPICO presentations | GM1.3
Geodiversity of proglacial areas and implications on abiotic ecosystem servicesIrene Maria Bollati, Cristina Viani, Anna Masseroli, Giovanni Mortara, Bruno Testa, Gianluca Tronti, Emmanuel Reynard, and Manuela Pelfini
Proglacial areas, defined as the areas left free from glaciers since the Little Ice Age, are open-air laboratories to study the effects of climate change on high mountain environments. Their different abiotic features (i.e. geodiversity) depend mainly on the bedrock characteristics, the type of glaciers acting in the areas and the morphometry of their hydrographic basins, which influence the geomorphic dynamics (i.e., geomorphodiversity). From this, it could derive a different response of glacier forefields to deglaciation and particular evolutionary trends. Hydrological elements and dynamics are particularly variable (i.e. hydrogeodiversity), especially in terms of proglacial lakes diversification, having effects down-valley, even far from the strict proglacial area, and also in term of potential natural hazards. Moreover, geodiversity of proglacial areas may have implications on other types of “diversity”. After the glacier retreat, glacier forefields are, in fact, characterized by soils development and vegetation settlement. In particular, soils characterized by different ages and by different degree of development coexist over short distances (i.e. pedodiversity), functioning also as a support for living organisms. Biotic components gradually colonize such areas, from the pioneer to the late-successional species, bringing varied species along the proglacial plains (i.e. biodiversity). All these aspects can be discussed in the perspective of the abiotic ecosystem services (i.e. regulating, supporting, provisioning, and cultural) provided by glacier forefields. Regulating services are related to both atmospheric and terrestrial processes, including natural hazard regulation. Supporting services deal mainly with habitat provision and soils development. Provisioning services include both material (freshwater, building materials) and immaterial (i.e. tourism) resources. Finally, cultural services, that are the most numerous, take into account, among the others, the spiritual and historical meaning, the geohistorical importance for the Earth Sciences development, the educational and geotourism-related opportunities, and the landscape benefit effects. Considering all these aspects, and the intense dynamics proglacial areas are affected by, which will be illustrated through examples mainly from the European Alps, it emerges the importance of a careful monitoring and management of such areas, hopefully through an even more holistic approach.
How to cite: Bollati, I. M., Viani, C., Masseroli, A., Mortara, G., Testa, B., Tronti, G., Reynard, E., and Pelfini, M.: Geodiversity of proglacial areas and implications on abiotic ecosystem services, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10566, https://doi.org/10.5194/egusphere-egu21-10566, 2021.
Proglacial areas, defined as the areas left free from glaciers since the Little Ice Age, are open-air laboratories to study the effects of climate change on high mountain environments. Their different abiotic features (i.e. geodiversity) depend mainly on the bedrock characteristics, the type of glaciers acting in the areas and the morphometry of their hydrographic basins, which influence the geomorphic dynamics (i.e., geomorphodiversity). From this, it could derive a different response of glacier forefields to deglaciation and particular evolutionary trends. Hydrological elements and dynamics are particularly variable (i.e. hydrogeodiversity), especially in terms of proglacial lakes diversification, having effects down-valley, even far from the strict proglacial area, and also in term of potential natural hazards. Moreover, geodiversity of proglacial areas may have implications on other types of “diversity”. After the glacier retreat, glacier forefields are, in fact, characterized by soils development and vegetation settlement. In particular, soils characterized by different ages and by different degree of development coexist over short distances (i.e. pedodiversity), functioning also as a support for living organisms. Biotic components gradually colonize such areas, from the pioneer to the late-successional species, bringing varied species along the proglacial plains (i.e. biodiversity). All these aspects can be discussed in the perspective of the abiotic ecosystem services (i.e. regulating, supporting, provisioning, and cultural) provided by glacier forefields. Regulating services are related to both atmospheric and terrestrial processes, including natural hazard regulation. Supporting services deal mainly with habitat provision and soils development. Provisioning services include both material (freshwater, building materials) and immaterial (i.e. tourism) resources. Finally, cultural services, that are the most numerous, take into account, among the others, the spiritual and historical meaning, the geohistorical importance for the Earth Sciences development, the educational and geotourism-related opportunities, and the landscape benefit effects. Considering all these aspects, and the intense dynamics proglacial areas are affected by, which will be illustrated through examples mainly from the European Alps, it emerges the importance of a careful monitoring and management of such areas, hopefully through an even more holistic approach.
How to cite: Bollati, I. M., Viani, C., Masseroli, A., Mortara, G., Testa, B., Tronti, G., Reynard, E., and Pelfini, M.: Geodiversity of proglacial areas and implications on abiotic ecosystem services, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10566, https://doi.org/10.5194/egusphere-egu21-10566, 2021.
EGU21-5392 | vPICO presentations | GM1.3
Geodiversity and geotourism for the local people - a study of the Western Carpathians.Pawel Strus, Anna Chrobak, and Jan Novotny
Study of the geodiversity in last decade was very popular in scientific literature. Also the Western Carpathians was the study area for geodiversity and geotourist assessment many times. As part of this study, an attempt was made to answer several questions regarding geodiversity and geotourism in relation to the local inhabitants of the area: 1/Is geodiversity and geotourism in the Western Carpathians able to attract wider crowds of tourists, not only interested specialists? 2/Do people living near a geotourist attraction realize its potential? In addition the authors want to show the summarizing geodiversity map of the Western Carpathians and how much time does the whole procedure of creating a geodiversity map for such a large area as the Western Carpathians take and how much work is required to prepare a study for that region. Important question is also a coherence of the study in a case of the region covering many countries and therefore various character of data available. Secondly, the authors have compared the geodiversity map with the distribution of geosites available in databases of Polish, Slovak and Czech Geological Surveys. This comparison shows that not always the largest number of geosites are located in places with the highest geodiversity index, as it might seem. Finally, the authors present a pilot study of the perception of inanimate nature by local residents that have been carried out in Podtatrze area (Southern Poland/Northern Slovakia). The results show that assumption that local people know their region very well is not entirely true. Most of the inhabitants do not know the basic forms of the relief that occur in the vicinity of their place of residence, cannot correctly recognize the type of rocks that are around them, or are unable to name the peaks that they look at from the window of their house. What could be the reason of it? Perhaps the lack of knowledge about their "little homeland" which they should acquire in primary school; or the simple lack of interest in inanimate nature resulting from the economic lack of profitability vision; or the lack of promotion of the most interesting geotouristic elements in the region. Summing up, the area of the Western Carpathians has areas with a very high and high geodiversity index, which may increase their (geo)tourism potential and constitute a source of additional profit for local residents, but requires access and promotion.
How to cite: Strus, P., Chrobak, A., and Novotny, J.: Geodiversity and geotourism for the local people - a study of the Western Carpathians., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5392, https://doi.org/10.5194/egusphere-egu21-5392, 2021.
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Study of the geodiversity in last decade was very popular in scientific literature. Also the Western Carpathians was the study area for geodiversity and geotourist assessment many times. As part of this study, an attempt was made to answer several questions regarding geodiversity and geotourism in relation to the local inhabitants of the area: 1/Is geodiversity and geotourism in the Western Carpathians able to attract wider crowds of tourists, not only interested specialists? 2/Do people living near a geotourist attraction realize its potential? In addition the authors want to show the summarizing geodiversity map of the Western Carpathians and how much time does the whole procedure of creating a geodiversity map for such a large area as the Western Carpathians take and how much work is required to prepare a study for that region. Important question is also a coherence of the study in a case of the region covering many countries and therefore various character of data available. Secondly, the authors have compared the geodiversity map with the distribution of geosites available in databases of Polish, Slovak and Czech Geological Surveys. This comparison shows that not always the largest number of geosites are located in places with the highest geodiversity index, as it might seem. Finally, the authors present a pilot study of the perception of inanimate nature by local residents that have been carried out in Podtatrze area (Southern Poland/Northern Slovakia). The results show that assumption that local people know their region very well is not entirely true. Most of the inhabitants do not know the basic forms of the relief that occur in the vicinity of their place of residence, cannot correctly recognize the type of rocks that are around them, or are unable to name the peaks that they look at from the window of their house. What could be the reason of it? Perhaps the lack of knowledge about their "little homeland" which they should acquire in primary school; or the simple lack of interest in inanimate nature resulting from the economic lack of profitability vision; or the lack of promotion of the most interesting geotouristic elements in the region. Summing up, the area of the Western Carpathians has areas with a very high and high geodiversity index, which may increase their (geo)tourism potential and constitute a source of additional profit for local residents, but requires access and promotion.
How to cite: Strus, P., Chrobak, A., and Novotny, J.: Geodiversity and geotourism for the local people - a study of the Western Carpathians., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5392, https://doi.org/10.5194/egusphere-egu21-5392, 2021.
EGU21-12903 | vPICO presentations | GM1.3 | Highlight
The Estrela UNESCO Global Geopark Science and Education Network for Sustainable DevelopmentHugo Gomes, Emanuel Castro, Gonçalo Vieira, Carla Mora, Susana Echeverria, and Helena Freitas
The Network of Science and Education for Sustainable Development of the Estrela UNESCO Global Geopark, implemented in 2019, aims at supporting and fostering applied research in the Estrela Geopark’s territory, based on an articulated set of interdisciplinary working Groups with close links to the Higher Education Institutions and the national scientific and technological system, highlighting the entities that carry out research in mountain regions. Besides, it will also serve as a catalyst for the new generation of scientists who will benefit from the more than 2,200 km2 of this territory as a living laboratory.
The Network presents a dynamic structure, through a set of nuclei (working groups), promoting science and education, and developing scientific research in complementary areas. Each Nucleus is coordinated by a Responsible Researcher (RR) and includes a team appointed by him. The Nuclei develop their R & D activity in articulation with public and private research units and technology centres, whose activity is developed in lines and projects closely related to the Estrela Geopark. Its priority activities will be defined within the framework of the Estrela Geopark’s Strategic Plan for Science, as well as within the premises of UNESCO, with priority in the following areas: Geology and Geomorphology, Landscape, Culture and Heritage, Climate and Climate Change, Biodiversity and Ecology, Environment and Natural Resources, Territory Planning and Risks, Tourism, Leisure and Sustainable Development.
Thus, this network aim at creating activities that promote science, education and scientific knowledge, in a collaborative way, based on the establishment of medium and long-term strategic partnerships between different actors of the territory and institutions that carry out research in the several themes, having as main objectives the cooperation in the identification of challenges, joint planning of activities, the definition of projects, the development of studies on the territory of the Estrela, the sharing of resources and infrastructures and the mobility and / or exchange of resources, with the aim of transferring, sharing and disseminating knowledge.
This Network promotes 5 working groups of science and education in: Climate Change; Water Resources; Biodiversity and Ecology; Tourism and Sustainability; Geodiversity and Geoconservation.
This holistic strategy aims at putting scientific knowledge at the service of the communities, through an effective citizen science, implementing various activities with the direct involvement of the communities and its promotion.
How to cite: Gomes, H., Castro, E., Vieira, G., Mora, C., Echeverria, S., and Freitas, H.: The Estrela UNESCO Global Geopark Science and Education Network for Sustainable Development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12903, https://doi.org/10.5194/egusphere-egu21-12903, 2021.
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The Network of Science and Education for Sustainable Development of the Estrela UNESCO Global Geopark, implemented in 2019, aims at supporting and fostering applied research in the Estrela Geopark’s territory, based on an articulated set of interdisciplinary working Groups with close links to the Higher Education Institutions and the national scientific and technological system, highlighting the entities that carry out research in mountain regions. Besides, it will also serve as a catalyst for the new generation of scientists who will benefit from the more than 2,200 km2 of this territory as a living laboratory.
The Network presents a dynamic structure, through a set of nuclei (working groups), promoting science and education, and developing scientific research in complementary areas. Each Nucleus is coordinated by a Responsible Researcher (RR) and includes a team appointed by him. The Nuclei develop their R & D activity in articulation with public and private research units and technology centres, whose activity is developed in lines and projects closely related to the Estrela Geopark. Its priority activities will be defined within the framework of the Estrela Geopark’s Strategic Plan for Science, as well as within the premises of UNESCO, with priority in the following areas: Geology and Geomorphology, Landscape, Culture and Heritage, Climate and Climate Change, Biodiversity and Ecology, Environment and Natural Resources, Territory Planning and Risks, Tourism, Leisure and Sustainable Development.
Thus, this network aim at creating activities that promote science, education and scientific knowledge, in a collaborative way, based on the establishment of medium and long-term strategic partnerships between different actors of the territory and institutions that carry out research in the several themes, having as main objectives the cooperation in the identification of challenges, joint planning of activities, the definition of projects, the development of studies on the territory of the Estrela, the sharing of resources and infrastructures and the mobility and / or exchange of resources, with the aim of transferring, sharing and disseminating knowledge.
This Network promotes 5 working groups of science and education in: Climate Change; Water Resources; Biodiversity and Ecology; Tourism and Sustainability; Geodiversity and Geoconservation.
This holistic strategy aims at putting scientific knowledge at the service of the communities, through an effective citizen science, implementing various activities with the direct involvement of the communities and its promotion.
How to cite: Gomes, H., Castro, E., Vieira, G., Mora, C., Echeverria, S., and Freitas, H.: The Estrela UNESCO Global Geopark Science and Education Network for Sustainable Development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12903, https://doi.org/10.5194/egusphere-egu21-12903, 2021.
GM1.4 – Quantifying geomorphic and sedimentary processes
EGU21-7032 * | vPICO presentations | GM1.4 | Highlight
Impact of extreme hydrological perturbation on sediment distribution from source to sink, PETM, Spain.Marine Prieur, Alexander C. Whittaker, Fritz Schlunegger, Tor O. Sømme, Jean Braun, and Sebastien Castelltort
Sedimentary dynamics and fluxes are influenced by both autogenic and allogenic forcings. A better understanding of the evolution of sedimentary systems through time and space requires us to decipher, and therefore to characterise, the impact of each of these on the Earth’s landscape. Given the current increase in the concentration of atmospheric carbon, studying the impact of rapid and global climate changes is of particular importance at the present time. Such events have been clearly defined in the geologic record. Among them, the Paleocene-Eocene Thermal Maximum (PETM) has been extensively studied worldwide and represents a possible analogue of the rapid current climate warming.
The present project focuses on the Southern Pyrenees (Spain) where excellent exposures of the Paleocene-Eocene interval span a large range of depositional environments from continental to deep-marine. These conditions allow us to collect data along the whole depositional system in order to document changes in sediment fluxes and paleohydraulic conditions. Because hydrological conditions have an impact on sediment transport through hydrodynamics, paleoflow reconstructions can shed light on changes in sediment dynamics. This information is reconstructed from the statistical distributions of channel morphologies, characteristic system dimensions including bankfull channel depth and width, and grain-sizes.
With this approach, our aim is to provide both qualitative and quantitative assessments of the magnitude and extent of the perturbation of sedimentary fluxes along an entire source-to-sink system during an episode of extreme climate change. This will lead to a better understanding of the impact of abrupt climate change on earth surface systems in mid-latitudinal areas, with possible implications for current climate adaptation policy.
This research is carried out in the scope of the lead author’s PhD project and is part of the S2S-FUTURE European Marie Skłodowska-Curie ITN (Grant Agreement No 860383).
How to cite: Prieur, M., Whittaker, A. C., Schlunegger, F., Sømme, T. O., Braun, J., and Castelltort, S.: Impact of extreme hydrological perturbation on sediment distribution from source to sink, PETM, Spain., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7032, https://doi.org/10.5194/egusphere-egu21-7032, 2021.
Sedimentary dynamics and fluxes are influenced by both autogenic and allogenic forcings. A better understanding of the evolution of sedimentary systems through time and space requires us to decipher, and therefore to characterise, the impact of each of these on the Earth’s landscape. Given the current increase in the concentration of atmospheric carbon, studying the impact of rapid and global climate changes is of particular importance at the present time. Such events have been clearly defined in the geologic record. Among them, the Paleocene-Eocene Thermal Maximum (PETM) has been extensively studied worldwide and represents a possible analogue of the rapid current climate warming.
The present project focuses on the Southern Pyrenees (Spain) where excellent exposures of the Paleocene-Eocene interval span a large range of depositional environments from continental to deep-marine. These conditions allow us to collect data along the whole depositional system in order to document changes in sediment fluxes and paleohydraulic conditions. Because hydrological conditions have an impact on sediment transport through hydrodynamics, paleoflow reconstructions can shed light on changes in sediment dynamics. This information is reconstructed from the statistical distributions of channel morphologies, characteristic system dimensions including bankfull channel depth and width, and grain-sizes.
With this approach, our aim is to provide both qualitative and quantitative assessments of the magnitude and extent of the perturbation of sedimentary fluxes along an entire source-to-sink system during an episode of extreme climate change. This will lead to a better understanding of the impact of abrupt climate change on earth surface systems in mid-latitudinal areas, with possible implications for current climate adaptation policy.
This research is carried out in the scope of the lead author’s PhD project and is part of the S2S-FUTURE European Marie Skłodowska-Curie ITN (Grant Agreement No 860383).
How to cite: Prieur, M., Whittaker, A. C., Schlunegger, F., Sømme, T. O., Braun, J., and Castelltort, S.: Impact of extreme hydrological perturbation on sediment distribution from source to sink, PETM, Spain., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7032, https://doi.org/10.5194/egusphere-egu21-7032, 2021.
EGU21-4124 | vPICO presentations | GM1.4 | Highlight
Quaternary sediment sources, sinks and transport pathways in the Black Sea-Caspian Sea regionChiara Költringer, Thomas Stevens, Martin Lindner, Yunus Baykal, and Redzhep Kurbanov
The Black Sea-Caspian Sea region is a vast and geomorphologically variable area where sea level changes, large rivers and their migration, and numerous interacting climate systems and aeolian regimes lead to a highly dynamic and complex situation of sediment supply and reworking. The area is blanketed by extensive loessic and sandy aeolian deposits, extending from northern Iran, through the Caucasus piedmont, Caspian lowland, and into the Crimea and East European Plain, as well as marine, fluvial and alluvial sediments. While loess deposits are especially extensive adjacent to major rivers such as the Volga, Don and Dnieper, the provenance, transport and nature of loess in this complex and highly dynamic environment remains poorly known.
Both, the Black Sea and the Caspian Sea experienced several transgressive and regressive phases during the Pleistocene, with temporary connections occurring over the Manych passage and resulting in the formation of marine terraces over a wide area, which are dry at present. The sea levels of the Caspian and Black seas and long-range north to south sediment transport are heavily influenced by the great rivers draining the previously glaciated East European Plain, the Volga, Don and Dnieper. In addition, the Black Sea and Caspian Sea are surrounded by mountain ranges, with the Carpathians in the west, the North Anatolian Mountains south of the Black Sea, the Crimea-Caucasus orogen and the Alborz mountains extending from northeast of the Black Sea to south of the Caspian Sea, all of which may act as sediment source regions. Furthermore, more distal orogens lying to the east, such as the Ural, Altai, Pamir and Kopet-Dag, and their palaeo-drainage systems, also represent potential sediment source areas for the Caspian Sea basin. The Karakum desert lying to the east of the south Caspian combines the potential of being a sediment sink for material from these mountains, as well as a secondary source for the Caspian Sea and the large loess area in northern Iran.
Here we apply U-Pb dating of detrital zircons to constrain the major sediment generating regions in this large area, transport pathways, and to further address the implications for sediment generation and cycling. In addition to loess, we aim to constrain the sediment transport pathways both for fluvial, marine and aeolian systems more generally, and to reconstruct the network of sediment routing in the Black Sea-Caspian Sea region. Our results reveal great spatial variability in zircon provenance and indicate the contribution of multiple source regions and transport pathways for most analysed samples and sites. Rivers have the strongest control on sediment erosion and distribution and are also in control of aeolian deposits, while not much sediment mixing seems to occur within the sea basins.
How to cite: Költringer, C., Stevens, T., Lindner, M., Baykal, Y., and Kurbanov, R.: Quaternary sediment sources, sinks and transport pathways in the Black Sea-Caspian Sea region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4124, https://doi.org/10.5194/egusphere-egu21-4124, 2021.
The Black Sea-Caspian Sea region is a vast and geomorphologically variable area where sea level changes, large rivers and their migration, and numerous interacting climate systems and aeolian regimes lead to a highly dynamic and complex situation of sediment supply and reworking. The area is blanketed by extensive loessic and sandy aeolian deposits, extending from northern Iran, through the Caucasus piedmont, Caspian lowland, and into the Crimea and East European Plain, as well as marine, fluvial and alluvial sediments. While loess deposits are especially extensive adjacent to major rivers such as the Volga, Don and Dnieper, the provenance, transport and nature of loess in this complex and highly dynamic environment remains poorly known.
Both, the Black Sea and the Caspian Sea experienced several transgressive and regressive phases during the Pleistocene, with temporary connections occurring over the Manych passage and resulting in the formation of marine terraces over a wide area, which are dry at present. The sea levels of the Caspian and Black seas and long-range north to south sediment transport are heavily influenced by the great rivers draining the previously glaciated East European Plain, the Volga, Don and Dnieper. In addition, the Black Sea and Caspian Sea are surrounded by mountain ranges, with the Carpathians in the west, the North Anatolian Mountains south of the Black Sea, the Crimea-Caucasus orogen and the Alborz mountains extending from northeast of the Black Sea to south of the Caspian Sea, all of which may act as sediment source regions. Furthermore, more distal orogens lying to the east, such as the Ural, Altai, Pamir and Kopet-Dag, and their palaeo-drainage systems, also represent potential sediment source areas for the Caspian Sea basin. The Karakum desert lying to the east of the south Caspian combines the potential of being a sediment sink for material from these mountains, as well as a secondary source for the Caspian Sea and the large loess area in northern Iran.
Here we apply U-Pb dating of detrital zircons to constrain the major sediment generating regions in this large area, transport pathways, and to further address the implications for sediment generation and cycling. In addition to loess, we aim to constrain the sediment transport pathways both for fluvial, marine and aeolian systems more generally, and to reconstruct the network of sediment routing in the Black Sea-Caspian Sea region. Our results reveal great spatial variability in zircon provenance and indicate the contribution of multiple source regions and transport pathways for most analysed samples and sites. Rivers have the strongest control on sediment erosion and distribution and are also in control of aeolian deposits, while not much sediment mixing seems to occur within the sea basins.
How to cite: Költringer, C., Stevens, T., Lindner, M., Baykal, Y., and Kurbanov, R.: Quaternary sediment sources, sinks and transport pathways in the Black Sea-Caspian Sea region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4124, https://doi.org/10.5194/egusphere-egu21-4124, 2021.
EGU21-8593 | vPICO presentations | GM1.4 | Highlight
Autogenic progradation of Bayhead deltas during sea-level rise wIthin incised valleys : theory, experiment and field examplesLaure Guerit, Brady Foreman, Chen Chen, Chris Paola, and Sébastien Castelltort
The evolution of sedimentary landscapes is primary driven by the interplay between the rate of accommodation creation A, controlled by sea-level and subsidence, and the rate of sediment supply S, controlled by erosion and sediment transport. In simple terms, the balance between A and S can be used to predict periods of progradation (when sediment supply exceeds accommodation) and periods of retrogradation (when accommodation exceeds sediment supply). However, a growing list of observations show that internal feedbacks within the sediment transport system can generate large-scale, autogenic stratigraphic patterns that are not anticipated by the A/S theory. These observations call for a reanalysis of several sequence stratigraphic precepts that assume a deterministic relationship between external forcings and stratigraphic products. Here, we focus on the filling of incised valleys during constant sea-level rise, and by a constant sediment flux. We develop a simple conceptual model of valley filling and we show that the classic sequence stratigraphic phenomenon of bayhead deltaic systems can be generated by purely autogenic progradation during the late stage of valley flooding. This transient “auto-advance” event results from a strong decrease of in-valley accommodation as base-level rises towards the valley apex. To test this model, we build a laboratory experiment that successfully reproduces the dynamics predicted by the model. Finally, we apply our model to two similar field examples, the Trinity and Brazos rivers incised valleys (Texas, USA). There systems are broadly similar in dimension and sea-level history but were filled at different sediment rates. We propose that this led to auto-advance event in the Trinity River valley while no advance is observed in the Brazos system. We thus show by conceptual, experimental and natural examples that auto-advance can produce out-of-sequence regressive bayhead diastems during highstands similar to a transient change in allogenic forcing. Combined with other recent studies, our findings support the idea that meso-scale autogenic patterns are ubiquitous in the fluvio-deltaic record, and need to be more extensively incorporated into reconstructions of Earth surface evolution and reservoir models.
How to cite: Guerit, L., Foreman, B., Chen, C., Paola, C., and Castelltort, S.: Autogenic progradation of Bayhead deltas during sea-level rise wIthin incised valleys : theory, experiment and field examples , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8593, https://doi.org/10.5194/egusphere-egu21-8593, 2021.
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The evolution of sedimentary landscapes is primary driven by the interplay between the rate of accommodation creation A, controlled by sea-level and subsidence, and the rate of sediment supply S, controlled by erosion and sediment transport. In simple terms, the balance between A and S can be used to predict periods of progradation (when sediment supply exceeds accommodation) and periods of retrogradation (when accommodation exceeds sediment supply). However, a growing list of observations show that internal feedbacks within the sediment transport system can generate large-scale, autogenic stratigraphic patterns that are not anticipated by the A/S theory. These observations call for a reanalysis of several sequence stratigraphic precepts that assume a deterministic relationship between external forcings and stratigraphic products. Here, we focus on the filling of incised valleys during constant sea-level rise, and by a constant sediment flux. We develop a simple conceptual model of valley filling and we show that the classic sequence stratigraphic phenomenon of bayhead deltaic systems can be generated by purely autogenic progradation during the late stage of valley flooding. This transient “auto-advance” event results from a strong decrease of in-valley accommodation as base-level rises towards the valley apex. To test this model, we build a laboratory experiment that successfully reproduces the dynamics predicted by the model. Finally, we apply our model to two similar field examples, the Trinity and Brazos rivers incised valleys (Texas, USA). There systems are broadly similar in dimension and sea-level history but were filled at different sediment rates. We propose that this led to auto-advance event in the Trinity River valley while no advance is observed in the Brazos system. We thus show by conceptual, experimental and natural examples that auto-advance can produce out-of-sequence regressive bayhead diastems during highstands similar to a transient change in allogenic forcing. Combined with other recent studies, our findings support the idea that meso-scale autogenic patterns are ubiquitous in the fluvio-deltaic record, and need to be more extensively incorporated into reconstructions of Earth surface evolution and reservoir models.
How to cite: Guerit, L., Foreman, B., Chen, C., Paola, C., and Castelltort, S.: Autogenic progradation of Bayhead deltas during sea-level rise wIthin incised valleys : theory, experiment and field examples , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8593, https://doi.org/10.5194/egusphere-egu21-8593, 2021.
EGU21-7683 | vPICO presentations | GM1.4
The origin of elevated low-relief surfaces in the Eastern Alps from geomorphic criteria and cosmogenic nuclide datingGerit Gradwohl, Kurt Stüwe, Moritz Liebl, and Jörg Robl
Elevated low-relief surfaces are peculiar landforms found in many areas across the Eastern Alps, most notably on the plateaus of the Northern Calcareous Alps and the southern metamorphic ranges from Nock Mountains to Koralpe. Found in domains both glaciated and unglaciated during the Pleistocene, (peri-)glacial erosion as well as fluvial prematurity have been cited as two opposing models for their formation. In order to contribute to this debate, we present a map of the existing low-relief surfaces in the Eastern Alps, bridging both glaciated and unglaciated regions, using a combined effort of field mapping and GIS-based mapping. Hypsometric statistics and analysis of longitudinal channel profiles show clear differences between formerly glaciated, partly-glaciated and unglaciated regions and their relations to the mapped surfaces. Furthermore, the pace of late- to post-Miocene incision is quantified via cosmogenic nuclide dating (26Al, 10Be, 21Ne) of allogenic siliceous sediments from discrete elevations correlating with the low-relief surfaces, in particular from cave sediments in the Northern Calcareous Alps. This information can be used to demonstrate that low-relief surfaces in many unglaciated regions, but also in some glaciated regions can be interpreted in terms of pre-Pleistocene relict landscapes.
How to cite: Gradwohl, G., Stüwe, K., Liebl, M., and Robl, J.: The origin of elevated low-relief surfaces in the Eastern Alps from geomorphic criteria and cosmogenic nuclide dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7683, https://doi.org/10.5194/egusphere-egu21-7683, 2021.
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Elevated low-relief surfaces are peculiar landforms found in many areas across the Eastern Alps, most notably on the plateaus of the Northern Calcareous Alps and the southern metamorphic ranges from Nock Mountains to Koralpe. Found in domains both glaciated and unglaciated during the Pleistocene, (peri-)glacial erosion as well as fluvial prematurity have been cited as two opposing models for their formation. In order to contribute to this debate, we present a map of the existing low-relief surfaces in the Eastern Alps, bridging both glaciated and unglaciated regions, using a combined effort of field mapping and GIS-based mapping. Hypsometric statistics and analysis of longitudinal channel profiles show clear differences between formerly glaciated, partly-glaciated and unglaciated regions and their relations to the mapped surfaces. Furthermore, the pace of late- to post-Miocene incision is quantified via cosmogenic nuclide dating (26Al, 10Be, 21Ne) of allogenic siliceous sediments from discrete elevations correlating with the low-relief surfaces, in particular from cave sediments in the Northern Calcareous Alps. This information can be used to demonstrate that low-relief surfaces in many unglaciated regions, but also in some glaciated regions can be interpreted in terms of pre-Pleistocene relict landscapes.
How to cite: Gradwohl, G., Stüwe, K., Liebl, M., and Robl, J.: The origin of elevated low-relief surfaces in the Eastern Alps from geomorphic criteria and cosmogenic nuclide dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7683, https://doi.org/10.5194/egusphere-egu21-7683, 2021.
EGU21-14866 | vPICO presentations | GM1.4
Remotely-sensed time series of rapid terrace formation in the Laguna del Viedma valley (Patagonia)Varyl Thorndycraft
The Patagonian Andes were subject to a range of geophysical drivers of landscape incision during the Last Glacial Interglacial Transition and Early Holocene, including tectonic and isostatic uplift, and base level fall triggered by rapid lake drainage events. Deciphering the drivers of river system response during this period is complex, and magnitudes and timescales of landscape change are poorly constrained. Herein, a remotely sensed time series of modern lake elevation change and terrace development is investigated for the Laguna del Viedma valley (Argentina) as a modern analogue of Late Quaternary landscape evolution. The aim of the research was to constrain the timing of terrace formation following lake-level fall of the Laguna del Viedma over a ~35 year period from 1985-2019. The objectives were to: 1) use satellite imagery from the period 1985-2019 to document landform, glacier and lake changes in the study area; 2) use remotely sensed imagery to map the landforms of the Laguna del Viedma valley; and 3) analyse terrace elevations using GIS. In total 7 terrace surfaces were distinguished by remotely sensed geomorphological mapping. The highest, and vegetated, T1 terrace surface (+75 m) was likely formed at the end of the last Holocene neoglacial advance. Viedma glacier recession at this time caused the abandonment of an ice-lateral spillway and allowed a subglacial drainage pathway leading to less stable lake level elevations and terrace formation. Whether the abandonment of T1 was associated with the 4 ka or 0.15 ka neoglacial termination constrains ~45 m of incision, at a rate of 0.01-0.33 m/yr, down to the T3 floodplain level by 1985. There then followed ~20 m of incision to the T4 level, which must have occurred by 2006, constraining a minimum rate of incision of 0.95 m/yr. The time series demonstrates rapid terrace formation occurred by vertical incision and lateral erosion, with mass movements contributing to lateral terrace recession. The implications of the data-set are discussed within the context of the Late Quaternary palaeohydrology of Patagonia where lake level falls of 10s to 100s of metres occurred within most large river systems from 42-52 ⁰S demonstrating that base level falls from lake drainage, and catastrophic floods events, were likely a major driver of landscape change in the region.
How to cite: Thorndycraft, V.: Remotely-sensed time series of rapid terrace formation in the Laguna del Viedma valley (Patagonia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14866, https://doi.org/10.5194/egusphere-egu21-14866, 2021.
The Patagonian Andes were subject to a range of geophysical drivers of landscape incision during the Last Glacial Interglacial Transition and Early Holocene, including tectonic and isostatic uplift, and base level fall triggered by rapid lake drainage events. Deciphering the drivers of river system response during this period is complex, and magnitudes and timescales of landscape change are poorly constrained. Herein, a remotely sensed time series of modern lake elevation change and terrace development is investigated for the Laguna del Viedma valley (Argentina) as a modern analogue of Late Quaternary landscape evolution. The aim of the research was to constrain the timing of terrace formation following lake-level fall of the Laguna del Viedma over a ~35 year period from 1985-2019. The objectives were to: 1) use satellite imagery from the period 1985-2019 to document landform, glacier and lake changes in the study area; 2) use remotely sensed imagery to map the landforms of the Laguna del Viedma valley; and 3) analyse terrace elevations using GIS. In total 7 terrace surfaces were distinguished by remotely sensed geomorphological mapping. The highest, and vegetated, T1 terrace surface (+75 m) was likely formed at the end of the last Holocene neoglacial advance. Viedma glacier recession at this time caused the abandonment of an ice-lateral spillway and allowed a subglacial drainage pathway leading to less stable lake level elevations and terrace formation. Whether the abandonment of T1 was associated with the 4 ka or 0.15 ka neoglacial termination constrains ~45 m of incision, at a rate of 0.01-0.33 m/yr, down to the T3 floodplain level by 1985. There then followed ~20 m of incision to the T4 level, which must have occurred by 2006, constraining a minimum rate of incision of 0.95 m/yr. The time series demonstrates rapid terrace formation occurred by vertical incision and lateral erosion, with mass movements contributing to lateral terrace recession. The implications of the data-set are discussed within the context of the Late Quaternary palaeohydrology of Patagonia where lake level falls of 10s to 100s of metres occurred within most large river systems from 42-52 ⁰S demonstrating that base level falls from lake drainage, and catastrophic floods events, were likely a major driver of landscape change in the region.
How to cite: Thorndycraft, V.: Remotely-sensed time series of rapid terrace formation in the Laguna del Viedma valley (Patagonia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14866, https://doi.org/10.5194/egusphere-egu21-14866, 2021.
EGU21-10394 | vPICO presentations | GM1.4
Tectonics and shore platform development: Rates and patterns of erosion on recently uplifted mudstone and limestone rocks at Kaikōura Peninsula, New ZealandJokotola Omidiji, Wayne Stephenson, Kevin Norton, and Mark Dickson
On tectonically active rock coasts, there is a dearth of erosion data documenting how rocks adjust (either fast or slow) in response to marine and subaerial processes immediately after coseismic uplift. Here we report erosion rates and evidence of reshaping of shore platform morphology on intertidal- and previously subtidal- rocks at Kaikōura Peninsula, South Island New Zealand. As a result of the November 2016 Kaikōura 7.8 (Mw) earthquake, platforms around the peninsula were uplifted by ~1.01 m, extended in width, and a 43-year active erosion monitoring campaign was abruptly halted but an opportunity to record how rocks respond to sudden environmental change like tectonics was presented. High-resolution topographic data obtained from quarterly surveys over four years using the micro-erosion meters (MEM) and Structure-from-Motion Multi View Stereo (SfM-MVS) surveys have provided accurate quantitative rates of erosion and visual representation of surface morphologies. MEM erosion data revealed variations in erosion, weathering and deposition rates across lithology, seasons, tidal positions, and platform elevation after the uplift. Four-years post-uplift erosion data shows a resetting of erosion rates and faster rock breakdown on both mudstone and limestone lithologies compared to pre-uplift rates. Over the 4-year period, surface downwearing rates for all platforms was 2.19 mm/yr, a 99.9% increase from a pre-uplift rate of 1.10 mm/yr. Average lowering rates on limestone, hard mudstone and soft mudstone platforms are 1.31 mm/yr, 2.13 mm/yr and 3.60 mm/yr, respectively. Seasonal trends in erosion rates remain unchanged as higher rates are still experienced during summer than winter seasons due to greater periods of higher temperatures and increased wetting and drying cycles. A year after uplift, previously reported across shore variations where erosion rates decreased from inner/landward margins of the platform to the outer/seaward sections disappeared with higher erosion rates fluctuating across all platform sections. Increased lowering rates on limestone rocks at the inner and outer sections were attributed to greater periods of wetting and drying, and loss of biological cover. These initially rapid rates decreased on the seaward sections after 3 years as a result of bioprotection and increased tidal wetting. On one of the harder mudstone rocks, a dramatic increase from a pre-uplift erosion rate of 0.43 mm/yr to 19.23 mm/yr (1-year after uplift) and subsequent decline to 1.54 mm/yr after four years is suggestive of isolated incidents of block detachment and erosion. For the first time, we complement MEM data with available SfM-MVS derived orthomosaics to provide evidence of changing rock morphology and processes such as intense granular disintegration, flaking, algal growth, and boring. On tectonically active rock coasts, the strong fluctuations in erosion rates and platform morphological expressions indicate the actions of not only waves, tides, and weathering processes but also tectonics in shore platform development.
How to cite: Omidiji, J., Stephenson, W., Norton, K., and Dickson, M.: Tectonics and shore platform development: Rates and patterns of erosion on recently uplifted mudstone and limestone rocks at Kaikōura Peninsula, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10394, https://doi.org/10.5194/egusphere-egu21-10394, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
On tectonically active rock coasts, there is a dearth of erosion data documenting how rocks adjust (either fast or slow) in response to marine and subaerial processes immediately after coseismic uplift. Here we report erosion rates and evidence of reshaping of shore platform morphology on intertidal- and previously subtidal- rocks at Kaikōura Peninsula, South Island New Zealand. As a result of the November 2016 Kaikōura 7.8 (Mw) earthquake, platforms around the peninsula were uplifted by ~1.01 m, extended in width, and a 43-year active erosion monitoring campaign was abruptly halted but an opportunity to record how rocks respond to sudden environmental change like tectonics was presented. High-resolution topographic data obtained from quarterly surveys over four years using the micro-erosion meters (MEM) and Structure-from-Motion Multi View Stereo (SfM-MVS) surveys have provided accurate quantitative rates of erosion and visual representation of surface morphologies. MEM erosion data revealed variations in erosion, weathering and deposition rates across lithology, seasons, tidal positions, and platform elevation after the uplift. Four-years post-uplift erosion data shows a resetting of erosion rates and faster rock breakdown on both mudstone and limestone lithologies compared to pre-uplift rates. Over the 4-year period, surface downwearing rates for all platforms was 2.19 mm/yr, a 99.9% increase from a pre-uplift rate of 1.10 mm/yr. Average lowering rates on limestone, hard mudstone and soft mudstone platforms are 1.31 mm/yr, 2.13 mm/yr and 3.60 mm/yr, respectively. Seasonal trends in erosion rates remain unchanged as higher rates are still experienced during summer than winter seasons due to greater periods of higher temperatures and increased wetting and drying cycles. A year after uplift, previously reported across shore variations where erosion rates decreased from inner/landward margins of the platform to the outer/seaward sections disappeared with higher erosion rates fluctuating across all platform sections. Increased lowering rates on limestone rocks at the inner and outer sections were attributed to greater periods of wetting and drying, and loss of biological cover. These initially rapid rates decreased on the seaward sections after 3 years as a result of bioprotection and increased tidal wetting. On one of the harder mudstone rocks, a dramatic increase from a pre-uplift erosion rate of 0.43 mm/yr to 19.23 mm/yr (1-year after uplift) and subsequent decline to 1.54 mm/yr after four years is suggestive of isolated incidents of block detachment and erosion. For the first time, we complement MEM data with available SfM-MVS derived orthomosaics to provide evidence of changing rock morphology and processes such as intense granular disintegration, flaking, algal growth, and boring. On tectonically active rock coasts, the strong fluctuations in erosion rates and platform morphological expressions indicate the actions of not only waves, tides, and weathering processes but also tectonics in shore platform development.
How to cite: Omidiji, J., Stephenson, W., Norton, K., and Dickson, M.: Tectonics and shore platform development: Rates and patterns of erosion on recently uplifted mudstone and limestone rocks at Kaikōura Peninsula, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10394, https://doi.org/10.5194/egusphere-egu21-10394, 2021.
EGU21-10867 | vPICO presentations | GM1.4
The transformation of a steepland river valley following an earthquake-triggered landslide near Kaikōura, NZJon Tunnicliffe, Jamie Howarth, and Chris Massey
In the relatively short and steep catchments of New Zealand’s Alps and Front Range, river systems traverse several process domains, from steep boulder-bed cascades to shallower braided range-front streams. Headwater streams (slope gradient >0.1 m·m-1) typically operate in a state of ‘supply limited’ conditions, where the river’s ability to carry sediment far exceeds the supply of material from upstream. With the catastrophic delivery of 13M m3 of landslide detritus following the 2016 7.8 Mw Kaikōura Earthquake, a tributary of the upper Hapuku River was filled to depths of up to 30 m, as debris spilled 1 km downstream from the delivery point. Nine airborne LiDAR surveys along the 12 km corridor have captured the transformation of the system from step-pool cascade to an unstable aggrading braidplain deposit to a vigorously incising channel, within four years of the event. With this rare window into disequilibrium conditions, we document the dramatic shifts in channel behaviour and dramatic reworking of the debris train following the landslide. There are two distinct phases: (1) a highly dynamic and unstable aggradation phase, with supply from upstream greatly exceeding river transport capacity and (2) exhaustion of supply from upstream and downcutting, maintaining high sediment transport rates through recruitment of material in the valley deposit. With a catchment area of only 3 km2, the upper river has transferred more than 4.2×106 m3 of coarse-grained material in 9 storm events of relatively modest intensity. This sequence of surveys provides an unprecedented picture of dramatic changes to a steepland river system in the aggradation/degradation cycle, which are very seldom captured owing to both the remoteness of such sites and the relative rarity of such events. A temporal picture of the valley sediment budget demonstrates the remarkable capacity of alpine systems to absorb disturbance through storage in the upper reaches, modulating the timing and the sedimentary character of materials being transferred to the reaches downstream. The case study highlights the utility of repeat LiDAR surveys for large-scale process studies and provides insights for assessing residence times of major landslide deliveries following large earthquake events.
How to cite: Tunnicliffe, J., Howarth, J., and Massey, C.: The transformation of a steepland river valley following an earthquake-triggered landslide near Kaikōura, NZ, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10867, https://doi.org/10.5194/egusphere-egu21-10867, 2021.
In the relatively short and steep catchments of New Zealand’s Alps and Front Range, river systems traverse several process domains, from steep boulder-bed cascades to shallower braided range-front streams. Headwater streams (slope gradient >0.1 m·m-1) typically operate in a state of ‘supply limited’ conditions, where the river’s ability to carry sediment far exceeds the supply of material from upstream. With the catastrophic delivery of 13M m3 of landslide detritus following the 2016 7.8 Mw Kaikōura Earthquake, a tributary of the upper Hapuku River was filled to depths of up to 30 m, as debris spilled 1 km downstream from the delivery point. Nine airborne LiDAR surveys along the 12 km corridor have captured the transformation of the system from step-pool cascade to an unstable aggrading braidplain deposit to a vigorously incising channel, within four years of the event. With this rare window into disequilibrium conditions, we document the dramatic shifts in channel behaviour and dramatic reworking of the debris train following the landslide. There are two distinct phases: (1) a highly dynamic and unstable aggradation phase, with supply from upstream greatly exceeding river transport capacity and (2) exhaustion of supply from upstream and downcutting, maintaining high sediment transport rates through recruitment of material in the valley deposit. With a catchment area of only 3 km2, the upper river has transferred more than 4.2×106 m3 of coarse-grained material in 9 storm events of relatively modest intensity. This sequence of surveys provides an unprecedented picture of dramatic changes to a steepland river system in the aggradation/degradation cycle, which are very seldom captured owing to both the remoteness of such sites and the relative rarity of such events. A temporal picture of the valley sediment budget demonstrates the remarkable capacity of alpine systems to absorb disturbance through storage in the upper reaches, modulating the timing and the sedimentary character of materials being transferred to the reaches downstream. The case study highlights the utility of repeat LiDAR surveys for large-scale process studies and provides insights for assessing residence times of major landslide deliveries following large earthquake events.
How to cite: Tunnicliffe, J., Howarth, J., and Massey, C.: The transformation of a steepland river valley following an earthquake-triggered landslide near Kaikōura, NZ, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10867, https://doi.org/10.5194/egusphere-egu21-10867, 2021.
EGU21-11067 | vPICO presentations | GM1.4
Landslides, river incision and environmental change: the Ruzizi gorge in the Kivu RiftToussaint Mugaruka Bibentyo, Antoine Dille, Arthur Depicker, Benoît Smets, Matthias Vanmaercke, Charles Nzolang, Stijn Dewaele, and Olivier Dewitte
The understanding of the interplay between natural and human induced factors in the occurrence of landslides remains poorly constrained in many regions, especially in tropical Africa where data-scarcity is high. In these regions where population growth is significant and causes changes in land use/cover, the need for a sustainable management of the land is on the rise. Here, we aim to unravel the occurrence of landslides in the 40 km-long Ruzizi gorge, a rapidly incising bedrock river in the Kivu Rift in Africa that has seen its landscape disturbed over the last decades by the development of the city of Bukavu (DR Congo). Careful field observations, historical aerial photographs, satellite imagery and archive analysis are combined to produce a multi-temporal inventory of 264 landslides. We show that the lithological context of the gorge and its extremely high incision rate (> 20 mm year-1) during the Holocene explains the presence of a concentration of large landslides (up to 2 km²) of undetermined age (well before the first observations of 1959) whose occurrence is purely natural. They are mostly of the slide type and do not show morphologic patterns of recent activity. The landslides that occurred during the last 60 years are flow-like shallower slope failures of smaller size (up to 0.12 km²) and tend to disappear rather quickly (sometimes within a few years) from the landscape as a result of rapid vegetation growth, land reclamation and (human-induced) soil erosion. They are primarily related to threshold slopes and precipitation plays a frequent role in their onset. However, land use/cover changes also affect their occurrence. This study provides useful information for a more accurate evaluation of the landslide hazard in the area, particularly with respect to the growth of the city of Bukavu that has developed without the consideration of naturally instable slopes. It also stresses the need and added value of building accurate landslide inventories in data-scarce regions.
How to cite: Mugaruka Bibentyo, T., Dille, A., Depicker, A., Smets, B., Vanmaercke, M., Nzolang, C., Dewaele, S., and Dewitte, O.: Landslides, river incision and environmental change: the Ruzizi gorge in the Kivu Rift, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11067, https://doi.org/10.5194/egusphere-egu21-11067, 2021.
The understanding of the interplay between natural and human induced factors in the occurrence of landslides remains poorly constrained in many regions, especially in tropical Africa where data-scarcity is high. In these regions where population growth is significant and causes changes in land use/cover, the need for a sustainable management of the land is on the rise. Here, we aim to unravel the occurrence of landslides in the 40 km-long Ruzizi gorge, a rapidly incising bedrock river in the Kivu Rift in Africa that has seen its landscape disturbed over the last decades by the development of the city of Bukavu (DR Congo). Careful field observations, historical aerial photographs, satellite imagery and archive analysis are combined to produce a multi-temporal inventory of 264 landslides. We show that the lithological context of the gorge and its extremely high incision rate (> 20 mm year-1) during the Holocene explains the presence of a concentration of large landslides (up to 2 km²) of undetermined age (well before the first observations of 1959) whose occurrence is purely natural. They are mostly of the slide type and do not show morphologic patterns of recent activity. The landslides that occurred during the last 60 years are flow-like shallower slope failures of smaller size (up to 0.12 km²) and tend to disappear rather quickly (sometimes within a few years) from the landscape as a result of rapid vegetation growth, land reclamation and (human-induced) soil erosion. They are primarily related to threshold slopes and precipitation plays a frequent role in their onset. However, land use/cover changes also affect their occurrence. This study provides useful information for a more accurate evaluation of the landslide hazard in the area, particularly with respect to the growth of the city of Bukavu that has developed without the consideration of naturally instable slopes. It also stresses the need and added value of building accurate landslide inventories in data-scarce regions.
How to cite: Mugaruka Bibentyo, T., Dille, A., Depicker, A., Smets, B., Vanmaercke, M., Nzolang, C., Dewaele, S., and Dewitte, O.: Landslides, river incision and environmental change: the Ruzizi gorge in the Kivu Rift, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11067, https://doi.org/10.5194/egusphere-egu21-11067, 2021.
EGU21-531 | vPICO presentations | GM1.4
Geomorphic and sedimentary characteristics of ancient Dora Kamiyama rockslide in Tibet Plateau - implications of dynamic process and frictional heatingZongji Yang, Shihao Liu, Liyong Wang, Gang Liu, and Xiaolong Fu
The mechanisms of high-speed and long-runout landslides are mainly reflected in the geomorphological morphology and internal sedimentology of the deposits. The geomorphic and sedimentary characteristics of ancient Dora Kamiyama rockslide in Tibet Plateau was discussed based on field investigation and multidisciplinary tests. The landslide area is divided into three zones: the source area (I), the translation area (II), and the accumulation area (III). Geomorphic features include toreva block, the levee, the transverse ridge, the longitudinal ridge, the hummock and the ridge confined by troughs and the carapace composed of giant blocks were analysed,which are considered as indicators of the dynamic process of the landslide during transport. 3 stages of the rockslide dynamic motion were proposed, including extensional, compressional and radial motions, respectively. Sedimentary features of facies in the rockslide was revealed, including carapace facies, blocky facies, fragmented facies, shear zones, and basal mixed zones, the mineral change process of the rockslide during the movement process and the temperature change of the sliding surface can be obtained based on analyzing the minerals change near the shear zone. The temperature field of the landslide and its movement process can be reconstructed through the temperature change of the shear zone. The results show that frictional heating was generated during complex dynamics interactions. The friction temperature generated by sliding near the fragmented facies was about 870–1470 °C. Based on sedimentary evidence, the dynamic evolution of the rockslide in response to temperature changes were reconstructed based on frictional thermal analysis.
How to cite: Yang, Z., Liu, S., Wang, L., Liu, G., and Fu, X.: Geomorphic and sedimentary characteristics of ancient Dora Kamiyama rockslide in Tibet Plateau - implications of dynamic process and frictional heating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-531, https://doi.org/10.5194/egusphere-egu21-531, 2021.
The mechanisms of high-speed and long-runout landslides are mainly reflected in the geomorphological morphology and internal sedimentology of the deposits. The geomorphic and sedimentary characteristics of ancient Dora Kamiyama rockslide in Tibet Plateau was discussed based on field investigation and multidisciplinary tests. The landslide area is divided into three zones: the source area (I), the translation area (II), and the accumulation area (III). Geomorphic features include toreva block, the levee, the transverse ridge, the longitudinal ridge, the hummock and the ridge confined by troughs and the carapace composed of giant blocks were analysed,which are considered as indicators of the dynamic process of the landslide during transport. 3 stages of the rockslide dynamic motion were proposed, including extensional, compressional and radial motions, respectively. Sedimentary features of facies in the rockslide was revealed, including carapace facies, blocky facies, fragmented facies, shear zones, and basal mixed zones, the mineral change process of the rockslide during the movement process and the temperature change of the sliding surface can be obtained based on analyzing the minerals change near the shear zone. The temperature field of the landslide and its movement process can be reconstructed through the temperature change of the shear zone. The results show that frictional heating was generated during complex dynamics interactions. The friction temperature generated by sliding near the fragmented facies was about 870–1470 °C. Based on sedimentary evidence, the dynamic evolution of the rockslide in response to temperature changes were reconstructed based on frictional thermal analysis.
How to cite: Yang, Z., Liu, S., Wang, L., Liu, G., and Fu, X.: Geomorphic and sedimentary characteristics of ancient Dora Kamiyama rockslide in Tibet Plateau - implications of dynamic process and frictional heating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-531, https://doi.org/10.5194/egusphere-egu21-531, 2021.
EGU21-3593 | vPICO presentations | GM1.4
The Need to Develop Compression and Decompression Data for Geomorphologists to Improve Sediment Volume Estimates from High-Resolution Topographic DataChristopher Gomez
The present contribution is centred on (1) a need of paradigm and methodological shift for transported sediment volumes, due to the advent of point-cloud technologies and (2) an attempt of solution for debris-flow and heterogeneous material.
Point-cloud technologies such as terrestrial and aerial LiDAR and photogrammetrically-based data have broken the inverse correlation between resolution and space-scale. Indeed, defining landforms at a centimeter vertical and horizontal scale, along several tens of kilometers was until very recently a pandora box, which both acquisition technologies and the democratization of computing capacity have allowed scientists to open. Unexpectedly, new challenges and the need to shift some of the traditional paradigms have emerged. In the present contribution, the author asks the question of whether the faithful tandem "topographic change and erosion/deposition" needs a revisit or not. The hypothesis of this question is imported from soil engineering, where questions of compaction and decompaction are essentials (and well understood). In other words, when sediments and soils are being eroded and redeposited, does the relation between erosion and deposition holds when using high-resolution topography? To this first question, the author then proposes one solution (already explored with TLS) using SfM-MVS photogrammetry to measure in-situ the density of heterogenous
Using simple laboratory experiments on different sediments to simulate (a) the effects of compression/decompression, and (b) the effects of self-comminution during transport, the author demonstrates that material fragmentation, and abrasion modifies the shape of the particles and their size resulting in variable bulk-volumes (as defined by the topography) for similar level of deposition energy, and that this volume change even further when the relay of processes are differentiated, resulting in further variation in the topographically measured volumes. In other words, the result show that high-resolution topography and topographical change does not signify high-resolution volumetric change, both in term of bulk and solid-phase volumes. It therefore appears that Geomorphology and Earth-Surface Processes Research need to integrate the use of soil density estimates from field-survey and also in the relay of processes model (i.e. should we expect compaction or decompaction from one type of deposit to another, and is the sediment transport modality expected to modify the shape and size of sediments significantly?).
Finally, the author presents one of the tool he has been working on for environment where compaction and decompaction is important: the transition between rockfalls/debris-flows/pyroclastic-flows and debris-flows, fluviatile flow in heterogeneous media. The author shows how SfM-MVS photogrammetry can be used to replace the sand-cone density estimation method with a higher-fidelity and an estimate of calculated error. Using “reverse-engineering”, this density calculation method combined with high-resolution topography could be used to then estimate and defines the transport modalities of sediments from one location to another.
How to cite: Gomez, C.: The Need to Develop Compression and Decompression Data for Geomorphologists to Improve Sediment Volume Estimates from High-Resolution Topographic Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3593, https://doi.org/10.5194/egusphere-egu21-3593, 2021.
The present contribution is centred on (1) a need of paradigm and methodological shift for transported sediment volumes, due to the advent of point-cloud technologies and (2) an attempt of solution for debris-flow and heterogeneous material.
Point-cloud technologies such as terrestrial and aerial LiDAR and photogrammetrically-based data have broken the inverse correlation between resolution and space-scale. Indeed, defining landforms at a centimeter vertical and horizontal scale, along several tens of kilometers was until very recently a pandora box, which both acquisition technologies and the democratization of computing capacity have allowed scientists to open. Unexpectedly, new challenges and the need to shift some of the traditional paradigms have emerged. In the present contribution, the author asks the question of whether the faithful tandem "topographic change and erosion/deposition" needs a revisit or not. The hypothesis of this question is imported from soil engineering, where questions of compaction and decompaction are essentials (and well understood). In other words, when sediments and soils are being eroded and redeposited, does the relation between erosion and deposition holds when using high-resolution topography? To this first question, the author then proposes one solution (already explored with TLS) using SfM-MVS photogrammetry to measure in-situ the density of heterogenous
Using simple laboratory experiments on different sediments to simulate (a) the effects of compression/decompression, and (b) the effects of self-comminution during transport, the author demonstrates that material fragmentation, and abrasion modifies the shape of the particles and their size resulting in variable bulk-volumes (as defined by the topography) for similar level of deposition energy, and that this volume change even further when the relay of processes are differentiated, resulting in further variation in the topographically measured volumes. In other words, the result show that high-resolution topography and topographical change does not signify high-resolution volumetric change, both in term of bulk and solid-phase volumes. It therefore appears that Geomorphology and Earth-Surface Processes Research need to integrate the use of soil density estimates from field-survey and also in the relay of processes model (i.e. should we expect compaction or decompaction from one type of deposit to another, and is the sediment transport modality expected to modify the shape and size of sediments significantly?).
Finally, the author presents one of the tool he has been working on for environment where compaction and decompaction is important: the transition between rockfalls/debris-flows/pyroclastic-flows and debris-flows, fluviatile flow in heterogeneous media. The author shows how SfM-MVS photogrammetry can be used to replace the sand-cone density estimation method with a higher-fidelity and an estimate of calculated error. Using “reverse-engineering”, this density calculation method combined with high-resolution topography could be used to then estimate and defines the transport modalities of sediments from one location to another.
How to cite: Gomez, C.: The Need to Develop Compression and Decompression Data for Geomorphologists to Improve Sediment Volume Estimates from High-Resolution Topographic Data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3593, https://doi.org/10.5194/egusphere-egu21-3593, 2021.
EGU21-15317 | vPICO presentations | GM1.4
Reconsidering the sediment connectivity and sediment transfer under the influence of hydraulic structures and coal mining in the Jiu river basinGabriela Adina Morosanu and Marta Cristina Jurchescu
The key to an efficient basin management, taking into account both the liquid (river water runoff and its quality) and the solid (sediment sources and delivery) components lies in the way we approach the complex problem of sediment-generating areas in a river basin. This complexity is manifested both through the primary geomorphological processes that contribute to the mobilization of significant amounts of alluvia from the slopes and along the river valleys, and the various environmental and anthropogenic factors that act as restrictors or catalysts of sediment transfer.
In the present study, we aim to analyze the various categories of anthropogenic factors, operating at different spatial scales (local or at subcatchment/river sector level), which contribute, together with the intrinsic geomorphological potential, to the sediment supply or, conversely, to the inhibition of erosion, transport and accumulation processes.
Tracking sediment mobilization, transfer, intermediate storage and final delivery in a lithologically and geomorphologically complex environment, such as the Jiu River Basin (10,070 km2), located in SW Romania, is a difficult task which can become even more challenging when we factor in the contribution of some additional elements of an anthropic nature. In our study area, represented by a Carpathian and Danubian river basin, some of the most significant issues impacting the research include, on the one hand, the existence of reservoirs and dams, the strengthening of anti-flood embankments or the presence of water diversions, to cite only hydrotechnical interventions, or the impact of coal mining on landforms, slope processes and sediment sources, on the other hand. All these factors can act locally or regionally and they can surpass the influence exerted by the natural factors, thus being responsible for the reduction, storage, or, on the contrary, for the acceleration of specific hydro-sedimentary fluxes on certain paths.
In order to connect these two categories of potential factors regulating sediment generation and transfer, the methodological approach consists in evaluating the internal – geomorphic upstream-downstream connectivity in relation/contrast with the disruptive anthropogenic factors. The proposed workflow can be divided in two steps: 1) the identification of the upstream sediment generating areas which are most connected to the downstream delivery/ storage/ accumulation areas (river network and river mouth) by applying the connectivity index (IC) proposed by Cavalli et al. (2013); and 2) the evaluation of potential hotspot areas exhibiting the highest degree of connectivity, as seen through the lens of the additional coupling or decoupling effects induced by the anthropic activities specific to the Jiu river basin: hydraulic structures and coal mining.
Outcome discussions will focus on mapping problematic sediment production, storage and transfer sectors, as evidenced by the impact of hydrotechnical works and artificial landforms from coal mining on the connectivity potential of the Jiu river basin.
How to cite: Morosanu, G. A. and Jurchescu, M. C.: Reconsidering the sediment connectivity and sediment transfer under the influence of hydraulic structures and coal mining in the Jiu river basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15317, https://doi.org/10.5194/egusphere-egu21-15317, 2021.
The key to an efficient basin management, taking into account both the liquid (river water runoff and its quality) and the solid (sediment sources and delivery) components lies in the way we approach the complex problem of sediment-generating areas in a river basin. This complexity is manifested both through the primary geomorphological processes that contribute to the mobilization of significant amounts of alluvia from the slopes and along the river valleys, and the various environmental and anthropogenic factors that act as restrictors or catalysts of sediment transfer.
In the present study, we aim to analyze the various categories of anthropogenic factors, operating at different spatial scales (local or at subcatchment/river sector level), which contribute, together with the intrinsic geomorphological potential, to the sediment supply or, conversely, to the inhibition of erosion, transport and accumulation processes.
Tracking sediment mobilization, transfer, intermediate storage and final delivery in a lithologically and geomorphologically complex environment, such as the Jiu River Basin (10,070 km2), located in SW Romania, is a difficult task which can become even more challenging when we factor in the contribution of some additional elements of an anthropic nature. In our study area, represented by a Carpathian and Danubian river basin, some of the most significant issues impacting the research include, on the one hand, the existence of reservoirs and dams, the strengthening of anti-flood embankments or the presence of water diversions, to cite only hydrotechnical interventions, or the impact of coal mining on landforms, slope processes and sediment sources, on the other hand. All these factors can act locally or regionally and they can surpass the influence exerted by the natural factors, thus being responsible for the reduction, storage, or, on the contrary, for the acceleration of specific hydro-sedimentary fluxes on certain paths.
In order to connect these two categories of potential factors regulating sediment generation and transfer, the methodological approach consists in evaluating the internal – geomorphic upstream-downstream connectivity in relation/contrast with the disruptive anthropogenic factors. The proposed workflow can be divided in two steps: 1) the identification of the upstream sediment generating areas which are most connected to the downstream delivery/ storage/ accumulation areas (river network and river mouth) by applying the connectivity index (IC) proposed by Cavalli et al. (2013); and 2) the evaluation of potential hotspot areas exhibiting the highest degree of connectivity, as seen through the lens of the additional coupling or decoupling effects induced by the anthropic activities specific to the Jiu river basin: hydraulic structures and coal mining.
Outcome discussions will focus on mapping problematic sediment production, storage and transfer sectors, as evidenced by the impact of hydrotechnical works and artificial landforms from coal mining on the connectivity potential of the Jiu river basin.
How to cite: Morosanu, G. A. and Jurchescu, M. C.: Reconsidering the sediment connectivity and sediment transfer under the influence of hydraulic structures and coal mining in the Jiu river basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15317, https://doi.org/10.5194/egusphere-egu21-15317, 2021.
EGU21-8444 | vPICO presentations | GM1.4
Sediment displacement evolution after dam removal in a mountain river (Oioki dam, Leitzaran River)J. Horacio García, Askoa Ibisate, Iban Sánchez-Pinto, Daniel Vázquez-Tarrío, Alfredo Ollero, Xabier Herrero, Josu Ortiz Martínez de Lahidalga, and Jon Beltrán de Lubiano
Bedload sediment transport was monitored from 2016 to 2020 in the Leitzaran River, in a reach affected by the removal of 7-meters high dam (Oioki dam). The removal was accomplished in two phases, the 3 first meters were removed in September 2018 and the second phase (September 2019) involved the removal of the remaining 4 meters. The study area was divided into three subreaches: control (unaffected by the dam), upstream and downstream of the dam. A sample of 300 RFID-tagged stones were seeded every year (100 at each reach).. Prior to this, the grain-size distribution of the surface sediment was characterized using the Wolman method. Then, the grain-size chosen for the tracer stones was distributed according to three Wentworth intervals: that corresponding to the surface d50, d50+1 (immediate upper interval), and d50-1 (immediate lower interval). It was not possible to follow completely, and the lower interval had to be dismissed as the sediment was very small or narrow to insert the tracer.
We conducted an extensive surveying field campaign every summer.
The number of retrieved tracers was relatively high, around 40-70% (considering all field campaigns), although with differences amongst the different sub-reaches. The obtained results were organized by displacements and volumes of sediment moved. The maximum (3,500 meters) and higher mean displacement (~1,550 meters) were registered in the hydrologic year 2019/20. These values are from the upstream reach of the dam and match simultaneously with (i) the whole removal of the dam, and (ii) the period showing a lower discharge (note the critical discharge for the movement of our particles is ~25-30 m3·s-1 (d50 = 64.0≥Ø<90.5 mm); mean discharge and peak flow from 2013 to 2020 were ~5.3 m3·s-1 and ~125.0 m3·s-1, respectively and at the end of the watershed).
We also estimated the bulk bedload volumes during the time spanned by this research and we report how the hydrologic year 2019/20 was the more active in terms of displaced volumes, moving up to 27,500 tons in the upstream reach. In fact, this year also presents the maximum for the downstream reach.
At this moment, besides the raw data of displacements and volumes, our observations highlight how the fact that a copious load of sediment was made available with the dam removal seemed to be more determinant than the magnitude of the flow to get larger tracer displacements.
How to cite: García, J. H., Ibisate, A., Sánchez-Pinto, I., Vázquez-Tarrío, D., Ollero, A., Herrero, X., Ortiz Martínez de Lahidalga, J., and Beltrán de Lubiano, J.: Sediment displacement evolution after dam removal in a mountain river (Oioki dam, Leitzaran River), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8444, https://doi.org/10.5194/egusphere-egu21-8444, 2021.
Bedload sediment transport was monitored from 2016 to 2020 in the Leitzaran River, in a reach affected by the removal of 7-meters high dam (Oioki dam). The removal was accomplished in two phases, the 3 first meters were removed in September 2018 and the second phase (September 2019) involved the removal of the remaining 4 meters. The study area was divided into three subreaches: control (unaffected by the dam), upstream and downstream of the dam. A sample of 300 RFID-tagged stones were seeded every year (100 at each reach).. Prior to this, the grain-size distribution of the surface sediment was characterized using the Wolman method. Then, the grain-size chosen for the tracer stones was distributed according to three Wentworth intervals: that corresponding to the surface d50, d50+1 (immediate upper interval), and d50-1 (immediate lower interval). It was not possible to follow completely, and the lower interval had to be dismissed as the sediment was very small or narrow to insert the tracer.
We conducted an extensive surveying field campaign every summer.
The number of retrieved tracers was relatively high, around 40-70% (considering all field campaigns), although with differences amongst the different sub-reaches. The obtained results were organized by displacements and volumes of sediment moved. The maximum (3,500 meters) and higher mean displacement (~1,550 meters) were registered in the hydrologic year 2019/20. These values are from the upstream reach of the dam and match simultaneously with (i) the whole removal of the dam, and (ii) the period showing a lower discharge (note the critical discharge for the movement of our particles is ~25-30 m3·s-1 (d50 = 64.0≥Ø<90.5 mm); mean discharge and peak flow from 2013 to 2020 were ~5.3 m3·s-1 and ~125.0 m3·s-1, respectively and at the end of the watershed).
We also estimated the bulk bedload volumes during the time spanned by this research and we report how the hydrologic year 2019/20 was the more active in terms of displaced volumes, moving up to 27,500 tons in the upstream reach. In fact, this year also presents the maximum for the downstream reach.
At this moment, besides the raw data of displacements and volumes, our observations highlight how the fact that a copious load of sediment was made available with the dam removal seemed to be more determinant than the magnitude of the flow to get larger tracer displacements.
How to cite: García, J. H., Ibisate, A., Sánchez-Pinto, I., Vázquez-Tarrío, D., Ollero, A., Herrero, X., Ortiz Martínez de Lahidalga, J., and Beltrán de Lubiano, J.: Sediment displacement evolution after dam removal in a mountain river (Oioki dam, Leitzaran River), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8444, https://doi.org/10.5194/egusphere-egu21-8444, 2021.
EGU21-13854 | vPICO presentations | GM1.4
An efficient method for automatic slope unit delineation from a huge regionPengfei Wu and Jintao Liu
EGU21-13289 | vPICO presentations | GM1.4
Weathering zonation within cracks in desert boulders reveals piecemeal crack propagation over geologic timescalesUri Shaanan, Amit Mushkin, Amir Sagy, Monica Rasmussen, and Martha-Cary Eppes
Rock fracturing can be slow and steady, comprising physiochemical processes that involve the chemical breaking of bonds that are weakened in response to local stress loading. Whereas subaerial cracking of surface boulders is universally observed in desert environments, the rates and specific mechanisms that drive crack propagation in such conditions are yet to be completely understood.
Here, we present new field and petrographic observations from mode-1 (tensional) incipient (rocks are not yet split) fractures in alluvial boulders from the hyperarid southern Negev desert (Israel). Over 100 carbonate boulders embedded in a well-developed, 70 ka desert pavement that held visible fractures were forced apart along the incipient cracks. Doing so revealed a systematic recurring tri-zone pattern in crack morphology whose boundaries consistently paralleled the crack propagation front: Zone 1 – A weathered (as evidenced by incipient patina) zone proximal to the boulder surface; Zone 2 – A relatively fresh crack zone partly filled with aeolian particles and salts medial from the boulder up-facing surface; Zone 3 – A chemically altered (as evidenced by petrographic analyses) zone of otherwise intact rock at the crack tip. The occurrence of such micro-morphological crack zonation suggests slow sub-critical crack propagation at sufficiently long geologic timescales that support development of differential weathering within the crack. The petrographic analyses of sections perpendicular to the plane of the crack indicate chemical alteration that precedes the crack propagation in both space and time (i.e., extends in front of the crack tip), also indicates slow piecemeal propagation of the crack. This linkage between chemical weathering processes at the crack tip and slow subcritical propagation of the crack into the boulder provides additional support for first-order control of environmental and climatic conditions on boulder cracking rates, regardless of the physical stress-loading mechanism.
How to cite: Shaanan, U., Mushkin, A., Sagy, A., Rasmussen, M., and Eppes, M.-C.: Weathering zonation within cracks in desert boulders reveals piecemeal crack propagation over geologic timescales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13289, https://doi.org/10.5194/egusphere-egu21-13289, 2021.
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Rock fracturing can be slow and steady, comprising physiochemical processes that involve the chemical breaking of bonds that are weakened in response to local stress loading. Whereas subaerial cracking of surface boulders is universally observed in desert environments, the rates and specific mechanisms that drive crack propagation in such conditions are yet to be completely understood.
Here, we present new field and petrographic observations from mode-1 (tensional) incipient (rocks are not yet split) fractures in alluvial boulders from the hyperarid southern Negev desert (Israel). Over 100 carbonate boulders embedded in a well-developed, 70 ka desert pavement that held visible fractures were forced apart along the incipient cracks. Doing so revealed a systematic recurring tri-zone pattern in crack morphology whose boundaries consistently paralleled the crack propagation front: Zone 1 – A weathered (as evidenced by incipient patina) zone proximal to the boulder surface; Zone 2 – A relatively fresh crack zone partly filled with aeolian particles and salts medial from the boulder up-facing surface; Zone 3 – A chemically altered (as evidenced by petrographic analyses) zone of otherwise intact rock at the crack tip. The occurrence of such micro-morphological crack zonation suggests slow sub-critical crack propagation at sufficiently long geologic timescales that support development of differential weathering within the crack. The petrographic analyses of sections perpendicular to the plane of the crack indicate chemical alteration that precedes the crack propagation in both space and time (i.e., extends in front of the crack tip), also indicates slow piecemeal propagation of the crack. This linkage between chemical weathering processes at the crack tip and slow subcritical propagation of the crack into the boulder provides additional support for first-order control of environmental and climatic conditions on boulder cracking rates, regardless of the physical stress-loading mechanism.
How to cite: Shaanan, U., Mushkin, A., Sagy, A., Rasmussen, M., and Eppes, M.-C.: Weathering zonation within cracks in desert boulders reveals piecemeal crack propagation over geologic timescales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13289, https://doi.org/10.5194/egusphere-egu21-13289, 2021.
EGU21-8416 | vPICO presentations | GM1.4
Calcium-sulfate wedges in the Atacama Desert as indicators for subsurface dynamicsAline Zinelabedin, Benedikt Ritter, Richard Albert, Dominik Brill, Axel Gerdes, Tony Reimann, Svenja Riedesel, and Tibor J. Dunai
Polygonal patterned grounds are common surface expressions of subsurface dynamics in periglacial and Martian environments. In the Periglacial these structures are typically associated with vertically laminated wedges in the subsurface being the product of cryogenic processes. These landscape features similarly occur in arid to hyperarid environments, such as in the Atacama Desert. Due to the salt-dominated soil of the Atacama Desert, haloturbation and salt heave mechanisms control the formation of wedges and polygons under arid conditions. We present x-ray diffraction and x-ray fluorescence analyses of wedges from the central Atacama Desert that contain various calcium-sulfate phases as potential drivers for the wedge-growth activity. The formation of these wedges is connected to varying water activity. Hydration- and dehydration-induced phase transitions of calcium-sulfate phases result in significant volumetric changes in the soils. In combination with crystallisation pressure of (re-)precipitated salts from infiltrated solutions, these processes significantly contribute to the subsurface stress field. The upward stress release is assumed to express in a microtopographic signature of the surface, such as the polygonal patterned ground. In order to investigate the polygon-wedge system under arid conditions, we will present a combination of sedimentological, mineralogical, and geochemical analyses of subsurface wedges from the central Atacama Desert. We also present data constraining the formation age of calcium sulfate-dominated wedges that formed within the El Diablo Formation of Miocene age.
How to cite: Zinelabedin, A., Ritter, B., Albert, R., Brill, D., Gerdes, A., Reimann, T., Riedesel, S., and Dunai, T. J.: Calcium-sulfate wedges in the Atacama Desert as indicators for subsurface dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8416, https://doi.org/10.5194/egusphere-egu21-8416, 2021.
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Polygonal patterned grounds are common surface expressions of subsurface dynamics in periglacial and Martian environments. In the Periglacial these structures are typically associated with vertically laminated wedges in the subsurface being the product of cryogenic processes. These landscape features similarly occur in arid to hyperarid environments, such as in the Atacama Desert. Due to the salt-dominated soil of the Atacama Desert, haloturbation and salt heave mechanisms control the formation of wedges and polygons under arid conditions. We present x-ray diffraction and x-ray fluorescence analyses of wedges from the central Atacama Desert that contain various calcium-sulfate phases as potential drivers for the wedge-growth activity. The formation of these wedges is connected to varying water activity. Hydration- and dehydration-induced phase transitions of calcium-sulfate phases result in significant volumetric changes in the soils. In combination with crystallisation pressure of (re-)precipitated salts from infiltrated solutions, these processes significantly contribute to the subsurface stress field. The upward stress release is assumed to express in a microtopographic signature of the surface, such as the polygonal patterned ground. In order to investigate the polygon-wedge system under arid conditions, we will present a combination of sedimentological, mineralogical, and geochemical analyses of subsurface wedges from the central Atacama Desert. We also present data constraining the formation age of calcium sulfate-dominated wedges that formed within the El Diablo Formation of Miocene age.
How to cite: Zinelabedin, A., Ritter, B., Albert, R., Brill, D., Gerdes, A., Reimann, T., Riedesel, S., and Dunai, T. J.: Calcium-sulfate wedges in the Atacama Desert as indicators for subsurface dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8416, https://doi.org/10.5194/egusphere-egu21-8416, 2021.
GM1.5 – Late-breaking Session: Hazard cascades from source to sink – the Elliot Creek and Chamoli events
EGU21-16587 | vPICO presentations | GM1.5
Extreme mass wasting during 2021 Dhauli Ganga event in the Higher Himalaya: insight from the landscapeAnand Kumar Pandey, Kotluri Sravan Kumar, Virendra Mani Tiwari, Puranchand Rao, Kirsten Cook, Christoff Andermann, Michael Dietze, Marco Pilz, and Niels Hovius
The slope instability and associated mass wasting are among the most efficient surface gradation processes in the bedrock terrain that produce dramatic landscape change and associated hazards. The wedge failure in periglacial Higher Himalaya terrain on 7th February in Chamoli, Uttarakhand (India) produced >1.5 km high rock avalanche, which amalgamated with the glacial debris on the frozen river bed produced massive debris flow along the high gradient Rishi Ganga catchment. The high-velocity debris flow and a surge of high flood led to extensive loss of life and infrastructures and issuing the extreme event flood warning along the Alakananda-Ganga river, despite there was no immediate extreme climatic event. The affected region is the locus of extreme mass wasting events associated with Glacial Lake Outburst Flood (GLOF) and Landslide Lake Outburst Flood (LLOF) in the recent past. We analyzed the landscape to understand its control on the 7th February 2021 Rishi Ganga event and briefly discuss other significant events in the adjoining region e.g. 1893/1970 Gohna Tal/Lake LLOF and 2013-Uttarakhand events in Chamoli, which have significance in understanding the surface processes in Higher Himalayan terrain.
How to cite: Pandey, A. K., Kumar, K. S., Tiwari, V. M., Rao, P., Cook, K., Andermann, C., Dietze, M., Pilz, M., and Hovius, N.: Extreme mass wasting during 2021 Dhauli Ganga event in the Higher Himalaya: insight from the landscape, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16587, https://doi.org/10.5194/egusphere-egu21-16587, 2021.
The slope instability and associated mass wasting are among the most efficient surface gradation processes in the bedrock terrain that produce dramatic landscape change and associated hazards. The wedge failure in periglacial Higher Himalaya terrain on 7th February in Chamoli, Uttarakhand (India) produced >1.5 km high rock avalanche, which amalgamated with the glacial debris on the frozen river bed produced massive debris flow along the high gradient Rishi Ganga catchment. The high-velocity debris flow and a surge of high flood led to extensive loss of life and infrastructures and issuing the extreme event flood warning along the Alakananda-Ganga river, despite there was no immediate extreme climatic event. The affected region is the locus of extreme mass wasting events associated with Glacial Lake Outburst Flood (GLOF) and Landslide Lake Outburst Flood (LLOF) in the recent past. We analyzed the landscape to understand its control on the 7th February 2021 Rishi Ganga event and briefly discuss other significant events in the adjoining region e.g. 1893/1970 Gohna Tal/Lake LLOF and 2013-Uttarakhand events in Chamoli, which have significance in understanding the surface processes in Higher Himalayan terrain.
How to cite: Pandey, A. K., Kumar, K. S., Tiwari, V. M., Rao, P., Cook, K., Andermann, C., Dietze, M., Pilz, M., and Hovius, N.: Extreme mass wasting during 2021 Dhauli Ganga event in the Higher Himalaya: insight from the landscape, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16587, https://doi.org/10.5194/egusphere-egu21-16587, 2021.
EGU21-16591 | vPICO presentations | GM1.5
Exploring the flow evolution of the Chamoli event (Uttarakhand, India) of 7 February 2021: From geomorphological mapping to multi-model computer simulationsMartin Mergili, Ashim Sattar, Johnathan Carrivick, Adam Emmer, Kyle T. Mandli, Mylène Jacquemart, Scott Watson, Matt Westoby, John J. Clague, Umesh K. Haritashya, and Dan H. Shugar
On 7 February 2021, a 25 million m³ rock/ice avalanche in Uttarakhand, northern India, developed into a far-reaching and devastating debris flow/debris flood, which we refer to as the ‘Chamoli event’. Based on an extensive remote sensing-based geomorphological mapping campaign, the key mechanisms and characteristics of this process chain are largely, but not yet fully understood. Numerical mass flow simulations can help confirm or reject hypotheses regarding spatiotemporal aspects of flow evolution, its magnitude and dynamics, and therefore contribute to a better process understanding. More broadly, geomorphological mapping and numerical modelling of the Chamoli event help us to gain insights of the extent to which we are able to accurately simulate complex high-mountain geohazard process cascades. Such an understanding is invaluable for predictive modelling efforts targeted at informing disaster risk reduction strategies.
In the present work, we back-calculate the flow dynamics of the Chamoli event with three state-of-the-art simulation models operating at different levels of complexity: (i) the one-phase mixture model RAMMS; (ii) the two-phase model GeoClaw, and (iii) the three-phase model r.avaflow. Input parameter sets are optimized against detailed reference data such as mapped trimlines and boulder locations, flow velocities and discharges obtained from video recordings, and erosion/deposition patterns derived by differencing pre- and post-event digital terrain models. The main aims of the study are to: (i) better understand the mechanisms of flow evolution of the Chamoli event; (ii) evaluate the level of model complexity that is necessary for accurating reproducing specific known characteristics of the process chain; and (iii) learn more about the sensitivity of model outputs to differences in initial conditions and model parameters, where these remain uncertain. The findings will facilitate the design of predictive modelling campaigns for hazard mapping purposes.
How to cite: Mergili, M., Sattar, A., Carrivick, J., Emmer, A., Mandli, K. T., Jacquemart, M., Watson, S., Westoby, M., Clague, J. J., Haritashya, U. K., and Shugar, D. H.: Exploring the flow evolution of the Chamoli event (Uttarakhand, India) of 7 February 2021: From geomorphological mapping to multi-model computer simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16591, https://doi.org/10.5194/egusphere-egu21-16591, 2021.
On 7 February 2021, a 25 million m³ rock/ice avalanche in Uttarakhand, northern India, developed into a far-reaching and devastating debris flow/debris flood, which we refer to as the ‘Chamoli event’. Based on an extensive remote sensing-based geomorphological mapping campaign, the key mechanisms and characteristics of this process chain are largely, but not yet fully understood. Numerical mass flow simulations can help confirm or reject hypotheses regarding spatiotemporal aspects of flow evolution, its magnitude and dynamics, and therefore contribute to a better process understanding. More broadly, geomorphological mapping and numerical modelling of the Chamoli event help us to gain insights of the extent to which we are able to accurately simulate complex high-mountain geohazard process cascades. Such an understanding is invaluable for predictive modelling efforts targeted at informing disaster risk reduction strategies.
In the present work, we back-calculate the flow dynamics of the Chamoli event with three state-of-the-art simulation models operating at different levels of complexity: (i) the one-phase mixture model RAMMS; (ii) the two-phase model GeoClaw, and (iii) the three-phase model r.avaflow. Input parameter sets are optimized against detailed reference data such as mapped trimlines and boulder locations, flow velocities and discharges obtained from video recordings, and erosion/deposition patterns derived by differencing pre- and post-event digital terrain models. The main aims of the study are to: (i) better understand the mechanisms of flow evolution of the Chamoli event; (ii) evaluate the level of model complexity that is necessary for accurating reproducing specific known characteristics of the process chain; and (iii) learn more about the sensitivity of model outputs to differences in initial conditions and model parameters, where these remain uncertain. The findings will facilitate the design of predictive modelling campaigns for hazard mapping purposes.
How to cite: Mergili, M., Sattar, A., Carrivick, J., Emmer, A., Mandli, K. T., Jacquemart, M., Watson, S., Westoby, M., Clague, J. J., Haritashya, U. K., and Shugar, D. H.: Exploring the flow evolution of the Chamoli event (Uttarakhand, India) of 7 February 2021: From geomorphological mapping to multi-model computer simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16591, https://doi.org/10.5194/egusphere-egu21-16591, 2021.
EGU21-16583 | vPICO presentations | GM1.5
Seismic observations of the 2021 Uttarakhand landslide/debris flow and flood eventsMarco Pilz, Fabrice Cotton, Kristen Cook, Michael Dieze, Niels Hovius, Rajesh Rekapalli, Venkatesh Vempati, Ravi Prakash Singh, N. Purnachandra Rao, Davuluri Srinagesh, and Virendra M. Tiwari
Debris flows and corresponding floods are a significant natural hazard for downstream communities in vulnerable regions, as yet unpredictable triggers and remote source locations might cause dynamics which are difficult to measure and quantify. Continuous observational coverage offered by seismic monitoring is one potential avenue for addressing this problem. Displacement of mass at Earth’s surface generates elastic seismic waves, which carry information about the temporal and spatial variability of the source and which can be recorded by seismometers at high temporal resolution across large spatial scales. Here, we report on seismic observations of the destructive 2021 Uttarakhand (India) debris flow and flood events. By means of a dense regional seismic network, we track and quantify the spatial and temporal evolution of the flood. Using continuous time-stamped seismic observations, a coherent signal of the flood movement is observed in a limited frequency band which can be tracked down the valley during the flood duration. Our analysis highlights potential benefits of using a network-wide seismic monitoring systems.
How to cite: Pilz, M., Cotton, F., Cook, K., Dieze, M., Hovius, N., Rekapalli, R., Vempati, V., Singh, R. P., Rao, N. P., Srinagesh, D., and Tiwari, V. M.: Seismic observations of the 2021 Uttarakhand landslide/debris flow and flood events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16583, https://doi.org/10.5194/egusphere-egu21-16583, 2021.
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Debris flows and corresponding floods are a significant natural hazard for downstream communities in vulnerable regions, as yet unpredictable triggers and remote source locations might cause dynamics which are difficult to measure and quantify. Continuous observational coverage offered by seismic monitoring is one potential avenue for addressing this problem. Displacement of mass at Earth’s surface generates elastic seismic waves, which carry information about the temporal and spatial variability of the source and which can be recorded by seismometers at high temporal resolution across large spatial scales. Here, we report on seismic observations of the destructive 2021 Uttarakhand (India) debris flow and flood events. By means of a dense regional seismic network, we track and quantify the spatial and temporal evolution of the flood. Using continuous time-stamped seismic observations, a coherent signal of the flood movement is observed in a limited frequency band which can be tracked down the valley during the flood duration. Our analysis highlights potential benefits of using a network-wide seismic monitoring systems.
How to cite: Pilz, M., Cotton, F., Cook, K., Dieze, M., Hovius, N., Rekapalli, R., Vempati, V., Singh, R. P., Rao, N. P., Srinagesh, D., and Tiwari, V. M.: Seismic observations of the 2021 Uttarakhand landslide/debris flow and flood events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16583, https://doi.org/10.5194/egusphere-egu21-16583, 2021.
EGU21-16593 | vPICO presentations | GM1.5
Anatomy of a cascading hazard: the flood part of the 7 February Uttarakhand eventMichael Dietze, Himangshu Paul, Anand Kumar Pandey, Rajesh Rekapalli, Puranchand Rao, Srinagesh D., Kirsten L. Cook, Marco Pilz, Niels Hovius, and Virendra Mani Tiwari
The 7 February Chamoli, Uttarakhand singularity imposed a severe geomorphic crisis. While remote sensing imagery quickly identified a major rock avalanche as its origin, there is a fundamental lack in high precision temporal information on the kinetics of this event about when, how, and why it evolved from a slope failure into a channel-confined mass wasting process, and ultimately into a debris laden flood. Furthermore, while the initial rock slide could be detected and located by global seismic networks, it was the flood which caused most of the destruction and fatalities. Yet, that part of the process cascade remained elusive in global seismic data sets.
Here, we present a detailed anatomy of the hazard cascade, with emphasis on the flood part. Using information from a dense seismic network, we explore the limits of detection and constrain its propagation velocity. By jointly inverting two physical models that predict spectral signal properties of floods, we estimate important hydraulic and sediment transport metrics. These information are key for designing any future early warning infrastructure.
How to cite: Dietze, M., Paul, H., Pandey, A. K., Rekapalli, R., Rao, P., D., S., Cook, K. L., Pilz, M., Hovius, N., and Tiwari, V. M.: Anatomy of a cascading hazard: the flood part of the 7 February Uttarakhand event, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16593, https://doi.org/10.5194/egusphere-egu21-16593, 2021.
The 7 February Chamoli, Uttarakhand singularity imposed a severe geomorphic crisis. While remote sensing imagery quickly identified a major rock avalanche as its origin, there is a fundamental lack in high precision temporal information on the kinetics of this event about when, how, and why it evolved from a slope failure into a channel-confined mass wasting process, and ultimately into a debris laden flood. Furthermore, while the initial rock slide could be detected and located by global seismic networks, it was the flood which caused most of the destruction and fatalities. Yet, that part of the process cascade remained elusive in global seismic data sets.
Here, we present a detailed anatomy of the hazard cascade, with emphasis on the flood part. Using information from a dense seismic network, we explore the limits of detection and constrain its propagation velocity. By jointly inverting two physical models that predict spectral signal properties of floods, we estimate important hydraulic and sediment transport metrics. These information are key for designing any future early warning infrastructure.
How to cite: Dietze, M., Paul, H., Pandey, A. K., Rekapalli, R., Rao, P., D., S., Cook, K. L., Pilz, M., Hovius, N., and Tiwari, V. M.: Anatomy of a cascading hazard: the flood part of the 7 February Uttarakhand event, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16593, https://doi.org/10.5194/egusphere-egu21-16593, 2021.
EGU21-16597 | vPICO presentations | GM1.5
Resolving pre-collapse slope motion at the February 2021 Chamoli rock-ice avalanche via feature tracking of optical satellite imageryMaximillian Van Wyk de Vries, Shashank Bhushan, David Shean, Etienne Berthier, César Deschamps-Berger, Simon Gascoin, Mylène Jacquemart, Andreas Kääb, and Dan Shugar
On the 7th of February 2021, a large rock-ice avalanche triggered a debris flow in Chamoli district, Uttarakhand, India, resulting in over 200 dead or missing and widespread infrastructure damage. The rock-ice avalanche originated from a steep, glacierized north-facing slope with a history of instability, most recently a 2016 ice avalanche. In this work, we assess whether the slope exhibited any precursory displacement prior to collapse. We evaluate monthly slope motion over the 2015 and 2021 period through feature tracking of high-resolution optical satellite imagery from Sentinel-2 (10 m Ground Sampling Distance) and PlanetScope (3-4 m Ground Sampling Distance). Assessing slope displacement of the underlying rock is complicated by the presence of glaciers over a portion of the collapse area, which display surface displacements due to internal ice deformation. We overcome this through tracking the motion over ice-free portions of the slide area, and evaluating the spatial pattern of velocity changes in glaciated areas. Preliminary results show that the rock-ice avalanche bloc slipped over 10 m in the 5 years prior to collapse, with particularly rapid slip occurring in the summer of 2017 and 2018. These results provide insight into the precursory conditions of the deadly rock-ice avalanche, and highlight the potential of high-resolution optical satellite image feature tracking for monitoring the stability of high-risk slopes.
How to cite: Van Wyk de Vries, M., Bhushan, S., Shean, D., Berthier, E., Deschamps-Berger, C., Gascoin, S., Jacquemart, M., Kääb, A., and Shugar, D.: Resolving pre-collapse slope motion at the February 2021 Chamoli rock-ice avalanche via feature tracking of optical satellite imagery, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16597, https://doi.org/10.5194/egusphere-egu21-16597, 2021.
On the 7th of February 2021, a large rock-ice avalanche triggered a debris flow in Chamoli district, Uttarakhand, India, resulting in over 200 dead or missing and widespread infrastructure damage. The rock-ice avalanche originated from a steep, glacierized north-facing slope with a history of instability, most recently a 2016 ice avalanche. In this work, we assess whether the slope exhibited any precursory displacement prior to collapse. We evaluate monthly slope motion over the 2015 and 2021 period through feature tracking of high-resolution optical satellite imagery from Sentinel-2 (10 m Ground Sampling Distance) and PlanetScope (3-4 m Ground Sampling Distance). Assessing slope displacement of the underlying rock is complicated by the presence of glaciers over a portion of the collapse area, which display surface displacements due to internal ice deformation. We overcome this through tracking the motion over ice-free portions of the slide area, and evaluating the spatial pattern of velocity changes in glaciated areas. Preliminary results show that the rock-ice avalanche bloc slipped over 10 m in the 5 years prior to collapse, with particularly rapid slip occurring in the summer of 2017 and 2018. These results provide insight into the precursory conditions of the deadly rock-ice avalanche, and highlight the potential of high-resolution optical satellite image feature tracking for monitoring the stability of high-risk slopes.
How to cite: Van Wyk de Vries, M., Bhushan, S., Shean, D., Berthier, E., Deschamps-Berger, C., Gascoin, S., Jacquemart, M., Kääb, A., and Shugar, D.: Resolving pre-collapse slope motion at the February 2021 Chamoli rock-ice avalanche via feature tracking of optical satellite imagery, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16597, https://doi.org/10.5194/egusphere-egu21-16597, 2021.
EGU21-16580 | vPICO presentations | GM1.5
Three-dimensional modelling of Uttarakhand slides using smoothed particle hydrodynamics (SPH)Shuai Li, Hui Tang, Chong Peng, and Hui-Cong An
On 7 February 2021, a massive flood occurred in the river Dhauliganga that damaged two hydroelectric stations, five bridges and trapped 100 to 150 casualties who are feared dead. Some evidence has been indicated that caused by a landslide, an avalanche, or a portion of the Nanda Devi glacier that broke off early in Uttarakhand's Joshimath area Chamoli district. The magnitude of the flood caused by the collapse was so large that it far exceeds the collapse itself. Two potential explanations were proposed to explain: the frictional heating of the avalanche may result in high temperatures in the sliding face, which is sufficient for ice and frozen sediments melting to occur in the path. The high-water content generated debris flows that enhanced the mobility of flowing. Another explanation is that it could be related to a glacial lake outburst flood or a temporary lake that eventually broke through its debris dam and poured down the valley. In any case, the collapse materials hold very high moisture content and fast mobility. In this study, a three-dimensional Smoothed Particle Hydrodynamics (SPH) method is adopted to model the flow-like Uttarakhand slides and to explore the physical processes during this event. The SPH is an adaptive, mesh-free, Lagrangian method that simulates free surfaces, moving interfaces, and large flow deformations. A non-Newtonian debris flow model, the Bingham rheological relationship, was incorporated into the SPH framework to describe source materials' characteristics. Besides, the whole flow processes of the flow-like Uttarakhand slides across the 3D terrain are represented. The time history of the velocity, acceleration, and forces were obtained from modelling to analyze the landslide dynamics.
How to cite: Li, S., Tang, H., Peng, C., and An, H.-C.: Three-dimensional modelling of Uttarakhand slides using smoothed particle hydrodynamics (SPH), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16580, https://doi.org/10.5194/egusphere-egu21-16580, 2021.
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On 7 February 2021, a massive flood occurred in the river Dhauliganga that damaged two hydroelectric stations, five bridges and trapped 100 to 150 casualties who are feared dead. Some evidence has been indicated that caused by a landslide, an avalanche, or a portion of the Nanda Devi glacier that broke off early in Uttarakhand's Joshimath area Chamoli district. The magnitude of the flood caused by the collapse was so large that it far exceeds the collapse itself. Two potential explanations were proposed to explain: the frictional heating of the avalanche may result in high temperatures in the sliding face, which is sufficient for ice and frozen sediments melting to occur in the path. The high-water content generated debris flows that enhanced the mobility of flowing. Another explanation is that it could be related to a glacial lake outburst flood or a temporary lake that eventually broke through its debris dam and poured down the valley. In any case, the collapse materials hold very high moisture content and fast mobility. In this study, a three-dimensional Smoothed Particle Hydrodynamics (SPH) method is adopted to model the flow-like Uttarakhand slides and to explore the physical processes during this event. The SPH is an adaptive, mesh-free, Lagrangian method that simulates free surfaces, moving interfaces, and large flow deformations. A non-Newtonian debris flow model, the Bingham rheological relationship, was incorporated into the SPH framework to describe source materials' characteristics. Besides, the whole flow processes of the flow-like Uttarakhand slides across the 3D terrain are represented. The time history of the velocity, acceleration, and forces were obtained from modelling to analyze the landslide dynamics.
How to cite: Li, S., Tang, H., Peng, C., and An, H.-C.: Three-dimensional modelling of Uttarakhand slides using smoothed particle hydrodynamics (SPH), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16580, https://doi.org/10.5194/egusphere-egu21-16580, 2021.
EGU21-16586 | vPICO presentations | GM1.5
Tracking the sediment plume from the 7th February 2021 Chamoli (Uttarakhand, India) hazard cascadeStuart Dunning, Simon Gascoin, Dan Shugar, and Wolfgang Schwanghart
The 7th February Chamoli hazard cascade originated from a 25 million m³ rock/ice avalanche slope failure that transformed into a destructive, far travelled debris flow / debris flood. There has a been necessarily a significant science focus on the proximal and immediate part of the hazard cascade. Here we report on the larger spatial and temporal scale: the sediment plume that progressed over the following days and weeks along the Ganga (Ganges) River. At the time of submission this was still recognisable over 900 km from the landslide site and had passed through hydro and nuclear power schemes. Beyond the initial plume, which has implications for rapid sedimentation in hydropower schemes and water / aquatic habitat quality, the subsequent (or not) mobilisation of event sediments over future years is a possible medium term chronic-threat to some hydropower projects. We show spectral ‘recipes’ and semi-automated methods for tracking the mass movement sediment plume and quantifying celerity using Sentinel 2 imagery, infilled using high-temporal repeat optical imagery from Planet Labs. data. The plume averaged ~60 km/day and, as expected has begun to slow as the river gradient decreases, as well as becoming less distinctive as some sediment is deposited, and as other sediment-rich water joins the Ganga.
The tracking of sediment plumes from these hazard cascades can be extended over inventories of similar events using both Sentinel 2 and Landsat archives. Such approaches allow us to provide insight into the possibilities of automated detection of hazard cascade sediment plumes to identify previously unknown events from remote source regions, as plumes have a far larger spatial-temporal footprint than the initial event.
How to cite: Dunning, S., Gascoin, S., Shugar, D., and Schwanghart, W.: Tracking the sediment plume from the 7th February 2021 Chamoli (Uttarakhand, India) hazard cascade, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16586, https://doi.org/10.5194/egusphere-egu21-16586, 2021.
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The 7th February Chamoli hazard cascade originated from a 25 million m³ rock/ice avalanche slope failure that transformed into a destructive, far travelled debris flow / debris flood. There has a been necessarily a significant science focus on the proximal and immediate part of the hazard cascade. Here we report on the larger spatial and temporal scale: the sediment plume that progressed over the following days and weeks along the Ganga (Ganges) River. At the time of submission this was still recognisable over 900 km from the landslide site and had passed through hydro and nuclear power schemes. Beyond the initial plume, which has implications for rapid sedimentation in hydropower schemes and water / aquatic habitat quality, the subsequent (or not) mobilisation of event sediments over future years is a possible medium term chronic-threat to some hydropower projects. We show spectral ‘recipes’ and semi-automated methods for tracking the mass movement sediment plume and quantifying celerity using Sentinel 2 imagery, infilled using high-temporal repeat optical imagery from Planet Labs. data. The plume averaged ~60 km/day and, as expected has begun to slow as the river gradient decreases, as well as becoming less distinctive as some sediment is deposited, and as other sediment-rich water joins the Ganga.
The tracking of sediment plumes from these hazard cascades can be extended over inventories of similar events using both Sentinel 2 and Landsat archives. Such approaches allow us to provide insight into the possibilities of automated detection of hazard cascade sediment plumes to identify previously unknown events from remote source regions, as plumes have a far larger spatial-temporal footprint than the initial event.
How to cite: Dunning, S., Gascoin, S., Shugar, D., and Schwanghart, W.: Tracking the sediment plume from the 7th February 2021 Chamoli (Uttarakhand, India) hazard cascade, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16586, https://doi.org/10.5194/egusphere-egu21-16586, 2021.
EGU21-16592 | vPICO presentations | GM1.5
Impact of the Chamoli disaster on flood Plain and water quality along the Himalayan riversSansar Meena, Akshansha Chauhan, Kushanav Bhuyan, and Ramesh P. Singh
The Himalayan rivers are glacier-fed and are vulnerable to devastating flash floods caused by damming of landslides and outbreak of glacial lakes. On 7 February 2021, around 10:30 am IST, a huge block of glacier mass broke from the Nanda Ghunti glacier. It is evident from the multi-temporal satellite imageries from Planet Scope that snow dust deposited in the affected area. During the course of the event, a huge amount of debris along with broken glacial fragments flooded the Rishi Ganga river and washed away the Hydropower plants; Rishi Ganga and Tapovan, more than 71 people were killed, and about 100 people are still missing. Detailed analysis of optical and radar data has been carried out to show the impact of the rockslide, changes in the surface characteristics of the source region, flood plains of the river and water quality of the Himalayan rivers (Alaknanda and Ganga). We have used five different indices Modified Normalized difference water index (MNDWI), Normalized difference vegetation index (NDVI), Enhanced vegetation index (EVI), Normalized difference turbidity Index (NDTI), and Normalized difference chlorophyll index (NDCI), that show pronounced changes in water quality and flood plain at the four different sections of the river. The spectral reflectance and backscattering coefficients derived from high-resolution Planet scope and Sentinel 1 SAR data show characteristics behaviour of the flood plain and water quality. Further, we have also found changes in the water quality of several canals after the Chamoli disaster event as the flood gates were closed to stop the deposit of sediments in the canal.
How to cite: Meena, S., Chauhan, A., Bhuyan, K., and Singh, R. P.: Impact of the Chamoli disaster on flood Plain and water quality along the Himalayan rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16592, https://doi.org/10.5194/egusphere-egu21-16592, 2021.
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The Himalayan rivers are glacier-fed and are vulnerable to devastating flash floods caused by damming of landslides and outbreak of glacial lakes. On 7 February 2021, around 10:30 am IST, a huge block of glacier mass broke from the Nanda Ghunti glacier. It is evident from the multi-temporal satellite imageries from Planet Scope that snow dust deposited in the affected area. During the course of the event, a huge amount of debris along with broken glacial fragments flooded the Rishi Ganga river and washed away the Hydropower plants; Rishi Ganga and Tapovan, more than 71 people were killed, and about 100 people are still missing. Detailed analysis of optical and radar data has been carried out to show the impact of the rockslide, changes in the surface characteristics of the source region, flood plains of the river and water quality of the Himalayan rivers (Alaknanda and Ganga). We have used five different indices Modified Normalized difference water index (MNDWI), Normalized difference vegetation index (NDVI), Enhanced vegetation index (EVI), Normalized difference turbidity Index (NDTI), and Normalized difference chlorophyll index (NDCI), that show pronounced changes in water quality and flood plain at the four different sections of the river. The spectral reflectance and backscattering coefficients derived from high-resolution Planet scope and Sentinel 1 SAR data show characteristics behaviour of the flood plain and water quality. Further, we have also found changes in the water quality of several canals after the Chamoli disaster event as the flood gates were closed to stop the deposit of sediments in the canal.
How to cite: Meena, S., Chauhan, A., Bhuyan, K., and Singh, R. P.: Impact of the Chamoli disaster on flood Plain and water quality along the Himalayan rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16592, https://doi.org/10.5194/egusphere-egu21-16592, 2021.
EGU21-16589 | vPICO presentations | GM1.5
Hydropower in the Himalayan hazardscapeWolfgang Schwanghart, Ugur Öztürk, Sumit Sen, Ankit Agarwal, and Oliver Korup
The 7 February Chamoli flood once again unveiled the vulnerability of Himalayan hydropower. On its destructive path downstream, the flood inflicted the loss of two nearby hydropower projects and damaged at least two more projects further downstream.
The flood is the third in a series of events with severe impact on the Himalayan hydropower sector. Uttarakhand was among the Indian states affected most by the 2013 Indian floods. Heavy rain, snow melt, and a glacial lake outburst flood damaged and partly destroyed more than 20 hydropower projects. The Gorkha Earthquake in 2015 led to damages to >30 projects, leading to a temporary loss of 34% of the hydropower generated in Nepal.
Analysis of these events reveals that neither flood discharge nor ground shaking were the primary processes responsible for the losses. Instead, the majority of damage was caused by geomorphological processes including landslides and rockfall, debris flows and extreme sediment discharges.
Only 20% of the ~500-GW hydropower potential is currently tapped in the Himalayas. This share is likely to increase given the high energy demands in the rapidly growing economies of the Himalayan countries.
With many opportune sites along large rivers being already occupied, there is a trend towards developing hydropower further upstream at higher elevations and closer to glaciated areas.
We argue that these developments and the past events highlight the need for a reappraisal of the Himalayan hazardscape. Risk analysis should increasingly incorporate processes such as glacial lake outburst floods and extreme sediment discharge events, and particularly aim to better understand hazard cascades which originate in glaciated and steep headwater catchments.
How to cite: Schwanghart, W., Öztürk, U., Sen, S., Agarwal, A., and Korup, O.: Hydropower in the Himalayan hazardscape, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16589, https://doi.org/10.5194/egusphere-egu21-16589, 2021.
The 7 February Chamoli flood once again unveiled the vulnerability of Himalayan hydropower. On its destructive path downstream, the flood inflicted the loss of two nearby hydropower projects and damaged at least two more projects further downstream.
The flood is the third in a series of events with severe impact on the Himalayan hydropower sector. Uttarakhand was among the Indian states affected most by the 2013 Indian floods. Heavy rain, snow melt, and a glacial lake outburst flood damaged and partly destroyed more than 20 hydropower projects. The Gorkha Earthquake in 2015 led to damages to >30 projects, leading to a temporary loss of 34% of the hydropower generated in Nepal.
Analysis of these events reveals that neither flood discharge nor ground shaking were the primary processes responsible for the losses. Instead, the majority of damage was caused by geomorphological processes including landslides and rockfall, debris flows and extreme sediment discharges.
Only 20% of the ~500-GW hydropower potential is currently tapped in the Himalayas. This share is likely to increase given the high energy demands in the rapidly growing economies of the Himalayan countries.
With many opportune sites along large rivers being already occupied, there is a trend towards developing hydropower further upstream at higher elevations and closer to glaciated areas.
We argue that these developments and the past events highlight the need for a reappraisal of the Himalayan hazardscape. Risk analysis should increasingly incorporate processes such as glacial lake outburst floods and extreme sediment discharge events, and particularly aim to better understand hazard cascades which originate in glaciated and steep headwater catchments.
How to cite: Schwanghart, W., Öztürk, U., Sen, S., Agarwal, A., and Korup, O.: Hydropower in the Himalayan hazardscape, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16589, https://doi.org/10.5194/egusphere-egu21-16589, 2021.
EGU21-16599 | vPICO presentations | GM1.5
Terrestrial overview of a landslide-tsunami-flood cascade at Elliot Creek, British ColumbiaMarten Geertsema, Brian Menounous, Dan Shugar, Tom Millard, Brent Ward, Göran Ekstrom, John Clague, Patrick Lynett, Jonathan Carrivick, Pierre Friele, Andrew Schaeffer, Davide Donati, Doug Stead, Jennifer Jackson, Bretwood Higman, Chunli Dai, Camille Brillon, Derek Heathfield, Gemma Bullard, Ian Giesbrecht, Katie Hughes, and Mylène Jacquemart
On 28 November 2020, some 18 Mm3 of quartz diorite detached from a steep rock face at the head of Elliot Creek in the southern Coast Mountains of British Columbia. The rock mass fragmented as it descended 1000 m and flowed across a debris-covered glacier. The rock avalanche was recorded on local and distant seismometers, with long-period amplitudes equivalent to a M 4.9 earthquake. Local seismic stations detected several earthquakes of magnitude <2.4 over the minutes and hours preceding the slide, though no causative relationship is yet suggested. Pre-slide optical and radar remote sensing data indicated some slope deformation leading up to failure. More than half of the rock debris entered a 0.6 km2 lake, where it generated a 115 m displacement wave that overtopped the moraine at the far end of the lake. We estimate that some 13.5 Mm3 of water left the lake from the combined impact of the landslide as well as erosion of the dam. The water that left the lake was channelized along Elliot Creek, scouring the valley more than 40 m in some places over a distance of 10 km before depositing debris on a 2 km2 fan in the Southgate River valley. Debris temporarily dammed the river, and turbid water continued down the Southgate River to Bute Inlet, where it produced a 70 km turbidity current and altered turbidity and water chemistry in the inlet for weeks. The landslide followed a century of rapid glacier retreat and thinning that exposed a growing lake basin. The outburst flood extended the damage of the landslide far beyond the limit of the landslide, destroying forest and impacting salmon spawning and rearing habitat. We expect more cascading impacts from landslides in the glacierized mountains of British Columbia as glaciers continue to retreat, exposing water bodies below steep slopes while simultaneously removing buttressing support.
How to cite: Geertsema, M., Menounous, B., Shugar, D., Millard, T., Ward, B., Ekstrom, G., Clague, J., Lynett, P., Carrivick, J., Friele, P., Schaeffer, A., Donati, D., Stead, D., Jackson, J., Higman, B., Dai, C., Brillon, C., Heathfield, D., Bullard, G., Giesbrecht, I., Hughes, K., and Jacquemart, M.: Terrestrial overview of a landslide-tsunami-flood cascade at Elliot Creek, British Columbia , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16599, https://doi.org/10.5194/egusphere-egu21-16599, 2021.
On 28 November 2020, some 18 Mm3 of quartz diorite detached from a steep rock face at the head of Elliot Creek in the southern Coast Mountains of British Columbia. The rock mass fragmented as it descended 1000 m and flowed across a debris-covered glacier. The rock avalanche was recorded on local and distant seismometers, with long-period amplitudes equivalent to a M 4.9 earthquake. Local seismic stations detected several earthquakes of magnitude <2.4 over the minutes and hours preceding the slide, though no causative relationship is yet suggested. Pre-slide optical and radar remote sensing data indicated some slope deformation leading up to failure. More than half of the rock debris entered a 0.6 km2 lake, where it generated a 115 m displacement wave that overtopped the moraine at the far end of the lake. We estimate that some 13.5 Mm3 of water left the lake from the combined impact of the landslide as well as erosion of the dam. The water that left the lake was channelized along Elliot Creek, scouring the valley more than 40 m in some places over a distance of 10 km before depositing debris on a 2 km2 fan in the Southgate River valley. Debris temporarily dammed the river, and turbid water continued down the Southgate River to Bute Inlet, where it produced a 70 km turbidity current and altered turbidity and water chemistry in the inlet for weeks. The landslide followed a century of rapid glacier retreat and thinning that exposed a growing lake basin. The outburst flood extended the damage of the landslide far beyond the limit of the landslide, destroying forest and impacting salmon spawning and rearing habitat. We expect more cascading impacts from landslides in the glacierized mountains of British Columbia as glaciers continue to retreat, exposing water bodies below steep slopes while simultaneously removing buttressing support.
How to cite: Geertsema, M., Menounous, B., Shugar, D., Millard, T., Ward, B., Ekstrom, G., Clague, J., Lynett, P., Carrivick, J., Friele, P., Schaeffer, A., Donati, D., Stead, D., Jackson, J., Higman, B., Dai, C., Brillon, C., Heathfield, D., Bullard, G., Giesbrecht, I., Hughes, K., and Jacquemart, M.: Terrestrial overview of a landslide-tsunami-flood cascade at Elliot Creek, British Columbia , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16599, https://doi.org/10.5194/egusphere-egu21-16599, 2021.
EGU21-16594 | vPICO presentations | GM1.5
Sustained Impact of a Glacial Lake Outburst Flood on Winter Turbidity Regimes across the Land-Ocean Aquatic ContinuumIan Giesbrecht, Suzanne Tank, Justin Del Bel Belluz, and Jennifer Jackson
Rainforest rivers export large quantities of terrestrial materials from watersheds to the coastal ocean, with important implications for local ecosystems and global biogeochemical cycles. However, the impact of episodic disturbance on this process is a critical knowledge gap in our understanding of land-sea connections. Fjords represent a global hotspot for terrestrial carbon burial in marine sediments, yet the relative importance of typical riverine fluxes vs. mass wasting fluxes is uncertain and dynamic. Similarly, mass wasting events can generate both an instantaneous pulse and a sustained shift in the material export regime. Riverine sediment regimes also have important implications for freshwater ecosystems and fisheries resources. A recent mass wasting event in Bute Inlet – Homalco First Nation traditional territory and British Columbia, Canada – presents an important opportunity to quantify the sustained impact of such an infrequent large disturbance on the source-to-sink linkages between glacierized mountains, rivers, and fjords.
On November 28, 2020, a landslide in the headwaters of the Elliot Creek watershed (118 km2) triggered a glacial lake outburst flood (GLOF) that eroded 3 km2 of forested land and exported large volumes of water and terrestrial materials to the lower reaches of the Southgate River watershed (1986 km2) and ultimately to the head of Bute Inlet. Here we assess river and ocean surface turbidity over four winter months following the event, in comparison to pre-event measurements taken across all seasons in recent years. River turbidity was measured on the Southgate River above and below the confluence of Elliot Creek, beginning in December 2020, and at the mouth of the Southgate and nearby Homathko Rivers prior to November 2020. Bute Inlet turbidity was measured (every month to two months) starting in May 2017.
Prior to the GLOF event, Southgate River turbidity ranged from a low of 3.3 ± 0.4 FNU in the winter to a high of 71.4 FNU in the summer meltwater period. Since the event, Southgate River turbidity has been consistently elevated ≥6 times background levels recorded above Elliot Creek. At the extreme, on January 13, 2021, seven weeks after the GLOF, Southgate River mean turbidity (105.2 ± 3.3 FNU) was 32 times the background (3.3 ± 0.4 FNU), equating to a sustained increase in wintertime turbidity that sometimes exceeds the historical summertime peak. Given the typical coupling of turbidity with discharge, we expect further increases in turbidity with the coming freshet of 2021; the first meltwater season following the GLOF. These results suggest the potential for a sustained shift in the seasonal turbidity regime of the Southgate River and the estuarine waters of Bute Inlet. The elevated turbidity signals broader changes to: sediment export and carbon burial, the depth and seasonality of light penetration, river water quality, and spawning habitat quality for anadromous fish. Ongoing monitoring will be used to characterize the duration, dynamics, and potential recovery of elevated turbidity regimes across the land-to-ocean aquatic continuum in Bute Inlet.
How to cite: Giesbrecht, I., Tank, S., Del Bel Belluz, J., and Jackson, J.: Sustained Impact of a Glacial Lake Outburst Flood on Winter Turbidity Regimes across the Land-Ocean Aquatic Continuum, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16594, https://doi.org/10.5194/egusphere-egu21-16594, 2021.
Rainforest rivers export large quantities of terrestrial materials from watersheds to the coastal ocean, with important implications for local ecosystems and global biogeochemical cycles. However, the impact of episodic disturbance on this process is a critical knowledge gap in our understanding of land-sea connections. Fjords represent a global hotspot for terrestrial carbon burial in marine sediments, yet the relative importance of typical riverine fluxes vs. mass wasting fluxes is uncertain and dynamic. Similarly, mass wasting events can generate both an instantaneous pulse and a sustained shift in the material export regime. Riverine sediment regimes also have important implications for freshwater ecosystems and fisheries resources. A recent mass wasting event in Bute Inlet – Homalco First Nation traditional territory and British Columbia, Canada – presents an important opportunity to quantify the sustained impact of such an infrequent large disturbance on the source-to-sink linkages between glacierized mountains, rivers, and fjords.
On November 28, 2020, a landslide in the headwaters of the Elliot Creek watershed (118 km2) triggered a glacial lake outburst flood (GLOF) that eroded 3 km2 of forested land and exported large volumes of water and terrestrial materials to the lower reaches of the Southgate River watershed (1986 km2) and ultimately to the head of Bute Inlet. Here we assess river and ocean surface turbidity over four winter months following the event, in comparison to pre-event measurements taken across all seasons in recent years. River turbidity was measured on the Southgate River above and below the confluence of Elliot Creek, beginning in December 2020, and at the mouth of the Southgate and nearby Homathko Rivers prior to November 2020. Bute Inlet turbidity was measured (every month to two months) starting in May 2017.
Prior to the GLOF event, Southgate River turbidity ranged from a low of 3.3 ± 0.4 FNU in the winter to a high of 71.4 FNU in the summer meltwater period. Since the event, Southgate River turbidity has been consistently elevated ≥6 times background levels recorded above Elliot Creek. At the extreme, on January 13, 2021, seven weeks after the GLOF, Southgate River mean turbidity (105.2 ± 3.3 FNU) was 32 times the background (3.3 ± 0.4 FNU), equating to a sustained increase in wintertime turbidity that sometimes exceeds the historical summertime peak. Given the typical coupling of turbidity with discharge, we expect further increases in turbidity with the coming freshet of 2021; the first meltwater season following the GLOF. These results suggest the potential for a sustained shift in the seasonal turbidity regime of the Southgate River and the estuarine waters of Bute Inlet. The elevated turbidity signals broader changes to: sediment export and carbon burial, the depth and seasonality of light penetration, river water quality, and spawning habitat quality for anadromous fish. Ongoing monitoring will be used to characterize the duration, dynamics, and potential recovery of elevated turbidity regimes across the land-to-ocean aquatic continuum in Bute Inlet.
How to cite: Giesbrecht, I., Tank, S., Del Bel Belluz, J., and Jackson, J.: Sustained Impact of a Glacial Lake Outburst Flood on Winter Turbidity Regimes across the Land-Ocean Aquatic Continuum, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16594, https://doi.org/10.5194/egusphere-egu21-16594, 2021.
EGU21-16595 | vPICO presentations | GM1.5
Effects of extreme events on the morphology of submarine channels: the case of the Elliot hazard cascadeMichael Tilston, Dan H. Shugar, Michael Clare, Maarten Heijnen, Sanem Acikalin, Matthieu Cartigny, Peter Talling, Daniel Parsons, Gwyn Lintern, Cooper Stacey, Stephen Hubbard, Sophie Hage, Daniel Bell, John Hughes Clark, Ian Giesbrecht, Jenifer Jackson, and Brian Menounos
Submarine systems where the canyon head is directly connected to the river mouth arguably provide the best setting for in situ studies of turbidity currents since the sediment supply propelling them arrive in periodic pulses linked to fluvial freshet events. Consequently, the frequency of, and similarity between, the turbidity currents flowing through these systems make it easier for their channel morphology to evolve towards a state of dynamic equilibrium. Therefore, if an extreme event occurs that dramatically alters the system’s sediment supply, it is reasonable to assume that submarine channels will undergo a period of rapid adjustment. This is the present scenario occurring in Bute Inlet following the recent Elliot Creek hazard cascade. Bute Inlet is one of the most actively monitored sites for turbidity currents in the world, and the extensive historical dataset that has been amassed at this site along with the rare Elliot Creek event provides the unique opportunity to study the impacts of extreme allogenic forcing mechanisms on the morphodynamics of submarine channels.
Preliminary measurements indicate that the turbidity in Elliot Creek has increased by ~40x compared to pre-slide measurements, and oceanographic measurements within a few days of the event show very high turbidity in ocean bottom water to a distance of almost 70 km from the delta. While the bathymetric survey since the landslide is so far constrained to the proximal region of the inlet, early results show that channel morphology was rapidly altered. Specifically, the submarine channel fed by Southgate River, which supplied water and sediment from the landslide and glacial outburst flood, was lowered by about 3m across the width of the channel bed. Conversely, the morphology of the channel fed by Homathko River has remained static between the 2020 and 2021 surveys. Below the confluence of these two submarine channels, the cyclic steps that once dominated the bed morphology appear to have been largely infilled by a 1-2m thick drape of sediment along the inner half of the channel bend, whereas the outer banks have laterally eroded by upwards of 50m at some points. This trend of channel widening and lateral migration appear to be propagating down the system. Importantly, the nature of the slide suggests that sediment delivery will remain elevated with respect to background conditions for decades into the future, suggesting that the submarine channel may be in the process of adapting to an entirely new flow regime rather than reacting to a singular extreme flow event.
How to cite: Tilston, M., Shugar, D. H., Clare, M., Heijnen, M., Acikalin, S., Cartigny, M., Talling, P., Parsons, D., Lintern, G., Stacey, C., Hubbard, S., Hage, S., Bell, D., Clark, J. H., Giesbrecht, I., Jackson, J., and Menounos, B.: Effects of extreme events on the morphology of submarine channels: the case of the Elliot hazard cascade, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16595, https://doi.org/10.5194/egusphere-egu21-16595, 2021.
Submarine systems where the canyon head is directly connected to the river mouth arguably provide the best setting for in situ studies of turbidity currents since the sediment supply propelling them arrive in periodic pulses linked to fluvial freshet events. Consequently, the frequency of, and similarity between, the turbidity currents flowing through these systems make it easier for their channel morphology to evolve towards a state of dynamic equilibrium. Therefore, if an extreme event occurs that dramatically alters the system’s sediment supply, it is reasonable to assume that submarine channels will undergo a period of rapid adjustment. This is the present scenario occurring in Bute Inlet following the recent Elliot Creek hazard cascade. Bute Inlet is one of the most actively monitored sites for turbidity currents in the world, and the extensive historical dataset that has been amassed at this site along with the rare Elliot Creek event provides the unique opportunity to study the impacts of extreme allogenic forcing mechanisms on the morphodynamics of submarine channels.
Preliminary measurements indicate that the turbidity in Elliot Creek has increased by ~40x compared to pre-slide measurements, and oceanographic measurements within a few days of the event show very high turbidity in ocean bottom water to a distance of almost 70 km from the delta. While the bathymetric survey since the landslide is so far constrained to the proximal region of the inlet, early results show that channel morphology was rapidly altered. Specifically, the submarine channel fed by Southgate River, which supplied water and sediment from the landslide and glacial outburst flood, was lowered by about 3m across the width of the channel bed. Conversely, the morphology of the channel fed by Homathko River has remained static between the 2020 and 2021 surveys. Below the confluence of these two submarine channels, the cyclic steps that once dominated the bed morphology appear to have been largely infilled by a 1-2m thick drape of sediment along the inner half of the channel bend, whereas the outer banks have laterally eroded by upwards of 50m at some points. This trend of channel widening and lateral migration appear to be propagating down the system. Importantly, the nature of the slide suggests that sediment delivery will remain elevated with respect to background conditions for decades into the future, suggesting that the submarine channel may be in the process of adapting to an entirely new flow regime rather than reacting to a singular extreme flow event.
How to cite: Tilston, M., Shugar, D. H., Clare, M., Heijnen, M., Acikalin, S., Cartigny, M., Talling, P., Parsons, D., Lintern, G., Stacey, C., Hubbard, S., Hage, S., Bell, D., Clark, J. H., Giesbrecht, I., Jackson, J., and Menounos, B.: Effects of extreme events on the morphology of submarine channels: the case of the Elliot hazard cascade, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16595, https://doi.org/10.5194/egusphere-egu21-16595, 2021.
EGU21-16596 | vPICO presentations | GM1.5
A field-scale laboratory to study particulate transport from river source to marine sink: Bute Inlet (Canada)Sophie Hage, Sanem Acikalin, Lewis Bailey, Matthieu Cartigny, Michael Clare, Ye Chen, Valier Galy, Maarten Heijnen, Kate Heerema, Stephen Hubbard, Jennifer Jackson, Gwyn Lintern, Dan Shugar, Stephen Simmons, Cooper Stacey, Peter Talling, Michael Tilston, Daniel Parsons, and Ed Pope
It is often assumed that particles produced on land (e.g., sediment, pollutants and organic matter) are transported through watersheds to a terminal sediment sink at the seashore. However, terrestrial particles can continue their journey offshore via submarine channels, accumulating in abyssal plains of the oceans. Offshore sediment transport processes are key controls on the burial of organic carbon and the distribution of benthic food, yet they are challenging to study due to the difficulty of capturing usually short duration events within large-scale systems at great ocean depths. Fjords are sufficiently small scale to enable their submarine channel systems to be studied from river source to terminal sink on seafloor fans. Bute Inlet is an up to 650 m deep fjord in British Columbia, Canada. The Homathko and Southgate rivers both feed Bute Inlet with freshwater and terrestrial sediment. A large landslide occurred on 28th November 2020, which caused a Glacial-Lake Outburst Flood (GLOF) which breached a moraine-dam and transported huge volumes of material through the Southgate valley and into Bute Inlet. The impact of this recent event on the submarine system in Bute is, for now, poorly constrained but ongoing work is exploring the impact of this major event on the Inlet. Bute Inlet is one of the most studied fjords worldwide, with a range of offshore campaigns that have been conducted during the last seventy years, providing an unprecedented background dataset and thus opportunity to explore what impact a large magnitude, low frequency terrestrial event had on the submarine system. This presentation will provide an overview of the past research conducted on the Bute submarine channel system, under more usual river discharge conditions and compare this background context to the recent GLOF event.
Previous studies have revealed that the floor of the Inlet is characterized by a 40 km long submarine channel formed by submarine avalanches of sediment (turbidity currents) that can be up to 30 m thick and reach velocities of up to 6.5 m/s. Based on time-lapse bathymetric mapping over 10 years, the evolution of this channel is known to be controlled by the fast (100 to 450 m/yr) upstream migration of 5 to 30 m high steps (called knickpoints) in the channel floor. Sediment cores reveal that the channel floor and proximal lobe are dominated by sand and up to 3 % of total organic carbon in the form of young woody debris. Research in Bute Inlet has thus allowed submarine flow processes, seafloor morphology and deposits to be linked in unprecedented detail. Using those past results as a baseline, new data collected after the GLOF will be crucial for testing the impact of high-magnitude catastrophic events on a marine system and the ultimate sink for the terrestrial material. Understanding what impact the GLOF had on the usual seafloor processes has direct implications for the preservation of benthic communities living in the fjord and for the global carbon cycle.
How to cite: Hage, S., Acikalin, S., Bailey, L., Cartigny, M., Clare, M., Chen, Y., Galy, V., Heijnen, M., Heerema, K., Hubbard, S., Jackson, J., Lintern, G., Shugar, D., Simmons, S., Stacey, C., Talling, P., Tilston, M., Parsons, D., and Pope, E.: A field-scale laboratory to study particulate transport from river source to marine sink: Bute Inlet (Canada), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16596, https://doi.org/10.5194/egusphere-egu21-16596, 2021.
It is often assumed that particles produced on land (e.g., sediment, pollutants and organic matter) are transported through watersheds to a terminal sediment sink at the seashore. However, terrestrial particles can continue their journey offshore via submarine channels, accumulating in abyssal plains of the oceans. Offshore sediment transport processes are key controls on the burial of organic carbon and the distribution of benthic food, yet they are challenging to study due to the difficulty of capturing usually short duration events within large-scale systems at great ocean depths. Fjords are sufficiently small scale to enable their submarine channel systems to be studied from river source to terminal sink on seafloor fans. Bute Inlet is an up to 650 m deep fjord in British Columbia, Canada. The Homathko and Southgate rivers both feed Bute Inlet with freshwater and terrestrial sediment. A large landslide occurred on 28th November 2020, which caused a Glacial-Lake Outburst Flood (GLOF) which breached a moraine-dam and transported huge volumes of material through the Southgate valley and into Bute Inlet. The impact of this recent event on the submarine system in Bute is, for now, poorly constrained but ongoing work is exploring the impact of this major event on the Inlet. Bute Inlet is one of the most studied fjords worldwide, with a range of offshore campaigns that have been conducted during the last seventy years, providing an unprecedented background dataset and thus opportunity to explore what impact a large magnitude, low frequency terrestrial event had on the submarine system. This presentation will provide an overview of the past research conducted on the Bute submarine channel system, under more usual river discharge conditions and compare this background context to the recent GLOF event.
Previous studies have revealed that the floor of the Inlet is characterized by a 40 km long submarine channel formed by submarine avalanches of sediment (turbidity currents) that can be up to 30 m thick and reach velocities of up to 6.5 m/s. Based on time-lapse bathymetric mapping over 10 years, the evolution of this channel is known to be controlled by the fast (100 to 450 m/yr) upstream migration of 5 to 30 m high steps (called knickpoints) in the channel floor. Sediment cores reveal that the channel floor and proximal lobe are dominated by sand and up to 3 % of total organic carbon in the form of young woody debris. Research in Bute Inlet has thus allowed submarine flow processes, seafloor morphology and deposits to be linked in unprecedented detail. Using those past results as a baseline, new data collected after the GLOF will be crucial for testing the impact of high-magnitude catastrophic events on a marine system and the ultimate sink for the terrestrial material. Understanding what impact the GLOF had on the usual seafloor processes has direct implications for the preservation of benthic communities living in the fjord and for the global carbon cycle.
How to cite: Hage, S., Acikalin, S., Bailey, L., Cartigny, M., Clare, M., Chen, Y., Galy, V., Heijnen, M., Heerema, K., Hubbard, S., Jackson, J., Lintern, G., Shugar, D., Simmons, S., Stacey, C., Talling, P., Tilston, M., Parsons, D., and Pope, E.: A field-scale laboratory to study particulate transport from river source to marine sink: Bute Inlet (Canada), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16596, https://doi.org/10.5194/egusphere-egu21-16596, 2021.
GM2.7 – Advances in geomorphometry and landform mapping: possibilities, challenges and perspectives
EGU21-8423 | vPICO presentations | GM2.7
A hydrodynamically consistent "slope-area" relationship for analysing fluvial landscape with wide rivers.Thomas Bernard, Philippe Davy, and Dimitri Lague
Landforms and channel networks have long been analysed through co-variation between topographic slope and drainage area, which is derived from easy-to-implement flow routing algorithms (D8 or Dinf) relying on topographic slopes. The slope-area relationship has been successful to identify morphologic regions in landscapes likely reflecting the erosion and transport processes that shape them. But the implicit assumption for using the slope-area relationship is that channels are narrower than the DEM resolution and that, at this scale, the flow is correctly routed. These assumptions are no more valid for very high-resolution DEM (HRDEM, <2 m) that are now widely available with unprecedented level of vertical accuracy (< 20 cm). In wide rivers, the drainage area algorithm puts the total river discharge in one of the pixel of each channel section and let the others with unrealistically low areas. In other words, D8 or Dinf algorithms are not adapted to resolve the lateral extent of rivers.
In this study, we propose a new topographic analysis relying on realistic hydraulic simulations of surface flow. For this, we use a particle-based hydraulic model, Floodos, which solves the 2D shallow water equations, and we present an analysis of the 1m LiDAR DEM of the Elder creek watershed in California, for which channels are up to ten meters wide. By simulating channel flows with water depth, hydraulic slope, specific discharge and bed shear stress, the hydraulic model reveals landscape patterns that are not described by the slope-area relationship. Additionally, the flow model handles very well the small irregularities of the topography.
We introduce new geomorphic descriptors: the hydraulic slope and the specific drainage area (or specific discharge). The catchment organization is then analysed through a new framework called the hydraulic slope-area diagram. This diagram has several benefits over the classical slope-area diagram. It correctly classifies pixels located in the river for a given discharge in the fluvial domain leading to a sharper transition between the colluvial and fluvial domain. The hillslope-to-valley transition is also insensitive to the DEM resolution. Channel width can also be automatically calculated based on a joint analysis of Dinf and 2D shallow water simulation. Finally, the capability to perform the hydraulic slope-area for various discharges brings a richer description of landscape organization by highlighting discharge-dependent regions such as floodplain areas and fluvial terraces.
How to cite: Bernard, T., Davy, P., and Lague, D.: A hydrodynamically consistent "slope-area" relationship for analysing fluvial landscape with wide rivers., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8423, https://doi.org/10.5194/egusphere-egu21-8423, 2021.
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Landforms and channel networks have long been analysed through co-variation between topographic slope and drainage area, which is derived from easy-to-implement flow routing algorithms (D8 or Dinf) relying on topographic slopes. The slope-area relationship has been successful to identify morphologic regions in landscapes likely reflecting the erosion and transport processes that shape them. But the implicit assumption for using the slope-area relationship is that channels are narrower than the DEM resolution and that, at this scale, the flow is correctly routed. These assumptions are no more valid for very high-resolution DEM (HRDEM, <2 m) that are now widely available with unprecedented level of vertical accuracy (< 20 cm). In wide rivers, the drainage area algorithm puts the total river discharge in one of the pixel of each channel section and let the others with unrealistically low areas. In other words, D8 or Dinf algorithms are not adapted to resolve the lateral extent of rivers.
In this study, we propose a new topographic analysis relying on realistic hydraulic simulations of surface flow. For this, we use a particle-based hydraulic model, Floodos, which solves the 2D shallow water equations, and we present an analysis of the 1m LiDAR DEM of the Elder creek watershed in California, for which channels are up to ten meters wide. By simulating channel flows with water depth, hydraulic slope, specific discharge and bed shear stress, the hydraulic model reveals landscape patterns that are not described by the slope-area relationship. Additionally, the flow model handles very well the small irregularities of the topography.
We introduce new geomorphic descriptors: the hydraulic slope and the specific drainage area (or specific discharge). The catchment organization is then analysed through a new framework called the hydraulic slope-area diagram. This diagram has several benefits over the classical slope-area diagram. It correctly classifies pixels located in the river for a given discharge in the fluvial domain leading to a sharper transition between the colluvial and fluvial domain. The hillslope-to-valley transition is also insensitive to the DEM resolution. Channel width can also be automatically calculated based on a joint analysis of Dinf and 2D shallow water simulation. Finally, the capability to perform the hydraulic slope-area for various discharges brings a richer description of landscape organization by highlighting discharge-dependent regions such as floodplain areas and fluvial terraces.
How to cite: Bernard, T., Davy, P., and Lague, D.: A hydrodynamically consistent "slope-area" relationship for analysing fluvial landscape with wide rivers., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8423, https://doi.org/10.5194/egusphere-egu21-8423, 2021.
EGU21-811 | vPICO presentations | GM2.7
Mapping Fluvial Landforms with Deep Similarity LearningPatrice Carbonneau
EGU21-3443 | vPICO presentations | GM2.7
Mapping and statistical procedures applied to extract topographical features of fluvial terraces and erosive surfaces.Juan F. Martinez-Murillo and David Carruana-Herrera
In recent decades, a huge advance in data collection has favoured the study of many questions related to geomorphic processes and associated landforms (Viles, 2016). This increment in data collection let face new questions and develop new methodologies in Geomorphology (Sofia et al., 2020). In this way, geomorphometry is a challenging discipline with the objective of quantify land-surface analysis and extract as well as detect geomorphological elements (Guyon and Elisseeff, 2008). As result, this discipline complement classis geomorphological maps with others extracted from digital elevation models providing land-surface metrics to investigate the full spectrum of geomorphology (Seijmonsbergen et al., 2011).
In this study, we investigate the extraction of topographical features from fluvial terraces and erosive surfaces by means of mapping procedures applied to a digital elevation model (spatial resolution of 5x5 m) using ArcGIS 10.7. This procedure was focussed on the quantification of elements (altitude, slope angle, length, and curvature, exposure) to characterize morphological elements that may define the presence of fluvial terraces as well as erosive surfaces. A Principal Component Analysis was performed to validate that procedure.
The procedure was conducted in two study areas: detection of fluvial terraces from the watershed of Guadalmedina river as well as of erosive surfaces in Sierras Subbéticas Geopark, both areas located in southern Spain.
How to cite: Martinez-Murillo, J. F. and Carruana-Herrera, D.: Mapping and statistical procedures applied to extract topographical features of fluvial terraces and erosive surfaces. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3443, https://doi.org/10.5194/egusphere-egu21-3443, 2021.
In recent decades, a huge advance in data collection has favoured the study of many questions related to geomorphic processes and associated landforms (Viles, 2016). This increment in data collection let face new questions and develop new methodologies in Geomorphology (Sofia et al., 2020). In this way, geomorphometry is a challenging discipline with the objective of quantify land-surface analysis and extract as well as detect geomorphological elements (Guyon and Elisseeff, 2008). As result, this discipline complement classis geomorphological maps with others extracted from digital elevation models providing land-surface metrics to investigate the full spectrum of geomorphology (Seijmonsbergen et al., 2011).
In this study, we investigate the extraction of topographical features from fluvial terraces and erosive surfaces by means of mapping procedures applied to a digital elevation model (spatial resolution of 5x5 m) using ArcGIS 10.7. This procedure was focussed on the quantification of elements (altitude, slope angle, length, and curvature, exposure) to characterize morphological elements that may define the presence of fluvial terraces as well as erosive surfaces. A Principal Component Analysis was performed to validate that procedure.
The procedure was conducted in two study areas: detection of fluvial terraces from the watershed of Guadalmedina river as well as of erosive surfaces in Sierras Subbéticas Geopark, both areas located in southern Spain.
How to cite: Martinez-Murillo, J. F. and Carruana-Herrera, D.: Mapping and statistical procedures applied to extract topographical features of fluvial terraces and erosive surfaces. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3443, https://doi.org/10.5194/egusphere-egu21-3443, 2021.
EGU21-4735 | vPICO presentations | GM2.7
Open source riverscapes: Analyzing the river corridor of the Naryn River in Kyrgyzstan based on open access dataFlorian Betz, Magdalena Lauermann, and Bernd Cyffka
In fluvial geomorphology as well as in freshwater ecology, rivers are commonly seen as nested hierarchical systems functioning over a range of spatial and temporal scales. Thus, for a comprehensive assessment, information on various scales is required. Over the past decade, remote sensing based approaches have become increasingly popular in river science to increase the spatial scale of analysis. However, data-scarce areas have been mostly ignored so far despite the fact that most remaining free flowing – and thus ecologically valuable – rivers worldwide are located in regions characterized by a lack of data sources like LiDAR or even aerial imagery. High resolution satellite data would be able to fill this data gap, but tends to be too costly for large scale applications what limits the ability for comprehensive studies on river systems in such remote areas. This in turn is a limitation for management and conservation of these rivers.
In this contribution, we suggest an approach for river corridor mapping based on open access data only in order to foster large scale geomorphological mapping of river corridors in data-scarce areas. For this aim, we combine advanced terrain analysis with multispectral remote sensing using the SRTM-1 DEM along with Landsat OLI imagery. We take the Naryn River in Kyrgyzstan as an example to demonstrate the potential of these open access data sets to derive a comprehensive set of parameters for characterizing this river corridor. The methods are adapted to the specific characteristics of medium resolution open access data sets and include an innovative, fuzzy logic based approach for riparian zone delineation, longitudinal profile smoothing based on constrained quantile regression and a delineation of the active channel width as needed for specific stream power computation. In addition, an indicator for river dynamics based on Landsat time series is developed. For each derived river corridor parameter, a rigor validation is performed. The results demonstrate, that our open access approach for geomorphological mapping of river corridors is capable to provide results sufficiently accurate to derive reach averaged information. Thus, it is well suited for large scale river characterization in data-scarce regions where otherwise the river corridors would remain largely unexplored from an up-to-date riverscape perspective. Such a characterization might be an entry point for further, more detailed research in selected study reaches and can deliver the required comprehensive background information for a range of topics in river science.
How to cite: Betz, F., Lauermann, M., and Cyffka, B.: Open source riverscapes: Analyzing the river corridor of the Naryn River in Kyrgyzstan based on open access data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4735, https://doi.org/10.5194/egusphere-egu21-4735, 2021.
In fluvial geomorphology as well as in freshwater ecology, rivers are commonly seen as nested hierarchical systems functioning over a range of spatial and temporal scales. Thus, for a comprehensive assessment, information on various scales is required. Over the past decade, remote sensing based approaches have become increasingly popular in river science to increase the spatial scale of analysis. However, data-scarce areas have been mostly ignored so far despite the fact that most remaining free flowing – and thus ecologically valuable – rivers worldwide are located in regions characterized by a lack of data sources like LiDAR or even aerial imagery. High resolution satellite data would be able to fill this data gap, but tends to be too costly for large scale applications what limits the ability for comprehensive studies on river systems in such remote areas. This in turn is a limitation for management and conservation of these rivers.
In this contribution, we suggest an approach for river corridor mapping based on open access data only in order to foster large scale geomorphological mapping of river corridors in data-scarce areas. For this aim, we combine advanced terrain analysis with multispectral remote sensing using the SRTM-1 DEM along with Landsat OLI imagery. We take the Naryn River in Kyrgyzstan as an example to demonstrate the potential of these open access data sets to derive a comprehensive set of parameters for characterizing this river corridor. The methods are adapted to the specific characteristics of medium resolution open access data sets and include an innovative, fuzzy logic based approach for riparian zone delineation, longitudinal profile smoothing based on constrained quantile regression and a delineation of the active channel width as needed for specific stream power computation. In addition, an indicator for river dynamics based on Landsat time series is developed. For each derived river corridor parameter, a rigor validation is performed. The results demonstrate, that our open access approach for geomorphological mapping of river corridors is capable to provide results sufficiently accurate to derive reach averaged information. Thus, it is well suited for large scale river characterization in data-scarce regions where otherwise the river corridors would remain largely unexplored from an up-to-date riverscape perspective. Such a characterization might be an entry point for further, more detailed research in selected study reaches and can deliver the required comprehensive background information for a range of topics in river science.
How to cite: Betz, F., Lauermann, M., and Cyffka, B.: Open source riverscapes: Analyzing the river corridor of the Naryn River in Kyrgyzstan based on open access data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4735, https://doi.org/10.5194/egusphere-egu21-4735, 2021.
EGU21-8771 | vPICO presentations | GM2.7
An open platform version of the Fluvial Corridor Toolbox with new functionalities to map nested floodplain envelops at the network scaleSamuel Dunesme, Christophe Rousson, and Hervé Piégay
Fluvial geomorphology provides an integrative space-time framework to target actions for risk mitigation, water resource preservation, and biodiversity and landscape conservation. Geomorphic data provides support critically important knowledge on stream condition, adjustment processes and sensitivity to change. Multiscale frameworks are needed to organize knowledge into useful usable and usable useful information. To move towards a more river rehabilitation or conservation strategy, a planning effort is needed at the regional or network scale, so called upscaled geomorphology, to provide large spatial datasets and new environmental monitoring facilities. This new emphasis on spatial planning resonates also with the concept of “green infrastructures” as a mean to protect fluvial corridors and identify opportunities to restore lateral connectivity and floodplain functionalities, thus providing ecosystem services such as flood expansion zones or better functioning ecological networks.
The development of a new version of the Fluvial Corridor Toolbox (FCT), following the work done by Alber and Piégay (2011) and Roux et al. (2015), started as an effort to implement port the ArcGIS code to the QGis platform for promoting open science and sharing our tools with river practitioners. The initial version of the FCT provided a spatial framework to produce metrics at a fine scale and a disaggregation-aggregation procedure to delineate floodplain functional units along a channel network. The new version of the FCT has been completely rewritten and incorporates ideas from Nardi et al. (2018) and Clubb et al. (2017) for improving the calculation of riverscape feature heights above the water level and delineate floodplain through the river network. We also borrowed the concept of swath profiles from Hergarten et al. (2014) as the basis of a new raster-based approach to characterize floodplain features on cross-sections. These new functionalities are based on high resolution DEM and landcover data to produce different floodplain envelops. Finally, we implemented tiled processing of very large raster datasets after Barnes (2016, 2017). This new version of the FCT also provides a lightweight framework for developing new processing toolchains/workflows. We successfully processed 5 m resolution landcover data over the entire (French) Rhone basin and used these layers to highlight the FCT interest. The new workflows are suitable for working at large network scale and are reproducible.
Further perspectives include an integration of such data and some FCT functionalities in online regional observatories with a visualization interface showing raw data on cross-sections and long profiles and synthetic patterns at the network scale allowing to compare target reaches with regional references.
How to cite: Dunesme, S., Rousson, C., and Piégay, H.: An open platform version of the Fluvial Corridor Toolbox with new functionalities to map nested floodplain envelops at the network scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8771, https://doi.org/10.5194/egusphere-egu21-8771, 2021.
Fluvial geomorphology provides an integrative space-time framework to target actions for risk mitigation, water resource preservation, and biodiversity and landscape conservation. Geomorphic data provides support critically important knowledge on stream condition, adjustment processes and sensitivity to change. Multiscale frameworks are needed to organize knowledge into useful usable and usable useful information. To move towards a more river rehabilitation or conservation strategy, a planning effort is needed at the regional or network scale, so called upscaled geomorphology, to provide large spatial datasets and new environmental monitoring facilities. This new emphasis on spatial planning resonates also with the concept of “green infrastructures” as a mean to protect fluvial corridors and identify opportunities to restore lateral connectivity and floodplain functionalities, thus providing ecosystem services such as flood expansion zones or better functioning ecological networks.
The development of a new version of the Fluvial Corridor Toolbox (FCT), following the work done by Alber and Piégay (2011) and Roux et al. (2015), started as an effort to implement port the ArcGIS code to the QGis platform for promoting open science and sharing our tools with river practitioners. The initial version of the FCT provided a spatial framework to produce metrics at a fine scale and a disaggregation-aggregation procedure to delineate floodplain functional units along a channel network. The new version of the FCT has been completely rewritten and incorporates ideas from Nardi et al. (2018) and Clubb et al. (2017) for improving the calculation of riverscape feature heights above the water level and delineate floodplain through the river network. We also borrowed the concept of swath profiles from Hergarten et al. (2014) as the basis of a new raster-based approach to characterize floodplain features on cross-sections. These new functionalities are based on high resolution DEM and landcover data to produce different floodplain envelops. Finally, we implemented tiled processing of very large raster datasets after Barnes (2016, 2017). This new version of the FCT also provides a lightweight framework for developing new processing toolchains/workflows. We successfully processed 5 m resolution landcover data over the entire (French) Rhone basin and used these layers to highlight the FCT interest. The new workflows are suitable for working at large network scale and are reproducible.
Further perspectives include an integration of such data and some FCT functionalities in online regional observatories with a visualization interface showing raw data on cross-sections and long profiles and synthetic patterns at the network scale allowing to compare target reaches with regional references.
How to cite: Dunesme, S., Rousson, C., and Piégay, H.: An open platform version of the Fluvial Corridor Toolbox with new functionalities to map nested floodplain envelops at the network scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8771, https://doi.org/10.5194/egusphere-egu21-8771, 2021.
EGU21-5624 | vPICO presentations | GM2.7
A statistical framework to analyse the stratigraphy of glaciofluvial terraces from topographic dataThomas Pollhammer, Bernhard Salcher, Florian Kober, and Gaudenz Deplazes
Alluvial staircase terraces are typical Quaternary features of mid- to high latitude rivers. Their formation is linked to i) repeated events of increased sediment production, triggered by Quaternary climatic fluctuations and ii) tectonic uplift. Accordingly, terraces may act as important terrestrial archives of climatic and geodynamic information. Comprehensive stratigraphic and topographic data qualifies the North Alpine Foreland as an ideal study region. Even though it has been subject to extensive investigations for more than a century consistent, basin wide stratigraphic models have not been proposed for more than a century (Penck and Brückner, 1909). Advances in local stratigraphy created major stratigraphic inconsistencies between the related parts of Switzerland, Germany and Austria.
In an aim to resolve these inconsistences we focus on foreland-wide high-resolution topographic data by investigating syn- and postdepositional signals behind the hypsometry and morphology of tributary terraces to the rivers Rhine and Danube.
By utilizing data from digital elevation models, geologic maps as well as outcrop information, morphostratigraphic analyses are provided via a new toolset within the framework of the software R. Semiautomatic projection of terrace data on 2D profiles allow to perform statistical analysis (based on slope, relative heights, concavity) of river long profiles and terrace-tops. We show that extracted parameters are highly suitable to make quantitative statements on fluvio-, glacio- and geodynamic processes controlling Quaternary terrace formation.
Penck, A., & Brückner, E. (1909). Die Alpen im Eiszeitalter. Leipzig: Tauchnitz.
How to cite: Pollhammer, T., Salcher, B., Kober, F., and Deplazes, G.: A statistical framework to analyse the stratigraphy of glaciofluvial terraces from topographic data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5624, https://doi.org/10.5194/egusphere-egu21-5624, 2021.
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Alluvial staircase terraces are typical Quaternary features of mid- to high latitude rivers. Their formation is linked to i) repeated events of increased sediment production, triggered by Quaternary climatic fluctuations and ii) tectonic uplift. Accordingly, terraces may act as important terrestrial archives of climatic and geodynamic information. Comprehensive stratigraphic and topographic data qualifies the North Alpine Foreland as an ideal study region. Even though it has been subject to extensive investigations for more than a century consistent, basin wide stratigraphic models have not been proposed for more than a century (Penck and Brückner, 1909). Advances in local stratigraphy created major stratigraphic inconsistencies between the related parts of Switzerland, Germany and Austria.
In an aim to resolve these inconsistences we focus on foreland-wide high-resolution topographic data by investigating syn- and postdepositional signals behind the hypsometry and morphology of tributary terraces to the rivers Rhine and Danube.
By utilizing data from digital elevation models, geologic maps as well as outcrop information, morphostratigraphic analyses are provided via a new toolset within the framework of the software R. Semiautomatic projection of terrace data on 2D profiles allow to perform statistical analysis (based on slope, relative heights, concavity) of river long profiles and terrace-tops. We show that extracted parameters are highly suitable to make quantitative statements on fluvio-, glacio- and geodynamic processes controlling Quaternary terrace formation.
Penck, A., & Brückner, E. (1909). Die Alpen im Eiszeitalter. Leipzig: Tauchnitz.
How to cite: Pollhammer, T., Salcher, B., Kober, F., and Deplazes, G.: A statistical framework to analyse the stratigraphy of glaciofluvial terraces from topographic data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5624, https://doi.org/10.5194/egusphere-egu21-5624, 2021.
EGU21-5934 | vPICO presentations | GM2.7
An object method to characterize grainflow morphologyPei Zhang
Grainflow, a fundamental agent moving sediment from the crest to the base of dune surfaces, leaves a temporary geomorphological signature on the slipfaces of aeolian dunes. The grainflow signature reflects the complex morphodynamical interaction between wind-driven sand transport and gravity-driven grainflow on an inclined surface. The purpose of this study is to present a method to objectively and efficiently delineate grainflow boundaries and characterize their morphology features by processing Digital Elevation Models (DEMs) obtained by terrestrial laser scanner in Matlab and ArcGIS. The method allows large numbers of grainflows to be quickly and objectively delineated and extracted from LiDAR data. As an aid tp subsequent analysis, the process avoids the subjective nature of manual measurement, thereby improving the commensurability of different grainflow regimes in both terrestrial and extraterrestrial environments. The results can be compared with the available grainflows morphology characteristics which are manually measured. The method is presented here in the context of analyzing grainflows and related processes on the slipfaces of dunes, but it is applicable over the broader scope of other forms of slope failure and geophysical flows, such as avalanches, snowslides, landslides, and debris flows.
How to cite: Zhang, P.: An object method to characterize grainflow morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5934, https://doi.org/10.5194/egusphere-egu21-5934, 2021.
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Grainflow, a fundamental agent moving sediment from the crest to the base of dune surfaces, leaves a temporary geomorphological signature on the slipfaces of aeolian dunes. The grainflow signature reflects the complex morphodynamical interaction between wind-driven sand transport and gravity-driven grainflow on an inclined surface. The purpose of this study is to present a method to objectively and efficiently delineate grainflow boundaries and characterize their morphology features by processing Digital Elevation Models (DEMs) obtained by terrestrial laser scanner in Matlab and ArcGIS. The method allows large numbers of grainflows to be quickly and objectively delineated and extracted from LiDAR data. As an aid tp subsequent analysis, the process avoids the subjective nature of manual measurement, thereby improving the commensurability of different grainflow regimes in both terrestrial and extraterrestrial environments. The results can be compared with the available grainflows morphology characteristics which are manually measured. The method is presented here in the context of analyzing grainflows and related processes on the slipfaces of dunes, but it is applicable over the broader scope of other forms of slope failure and geophysical flows, such as avalanches, snowslides, landslides, and debris flows.
How to cite: Zhang, P.: An object method to characterize grainflow morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5934, https://doi.org/10.5194/egusphere-egu21-5934, 2021.
EGU21-14945 | vPICO presentations | GM2.7
Machine learning-based grain size mapping from satellite imagesGiulia Marchetti, Simone Bizzi, Barbara Belletti, Barbara Lastoria, Stefano Mariani, Marco Casaioli, Francesco Comiti, and Patrice Carbonneau
A comprehensive understanding of river dynamics requires the quantitative knowledge of the grain size distribution of bed sediments and its variation across multiple temporal and spatial scales. Several techniques are already available for grain size assessment based on field and remotely sensed data. However, the existing methods permit to cover small areas and short time scale, thus the operational measurement of grain size distribution of river bed sediments at the catchment scale remains an open problem. A solution could be the use of satellite images but very limited investigations have been carried out so far on the use of satellite-based sub-pixel mapping of river characteristics relevant to ecohydraulic processes.
In this study, we propose a new approach to retrieve sub-pixel scale grain size classes information from Sentinel 2 imagery building upon a new image-based grain size mapping procedure. Four Italian gravel-bed rivers featuring different morphology were selected to conduct UAV acquisitions and extract ground truth grain size data from the near-ground images, by photo-sieving techniques. We generated grain size maps at the resolution of 2 cm on river bars in each study site by exploiting image texture measurements, and subsequently resampled and co-registered the grain size maps with Sentinel 2 data resolution.
Relationships between the grain sizes measured and the reflectance values in Sentinel 2 imagery - available in 11 bands super resolved at 10 m resolution – were analyzed. Based on these, our first results show statistically significant predictive models (cross validation results: MAE of 3.38 ± 13.4 mm and R2=0.48) by using a machine learning framework (Support Vector Machine) to retrieve grain size classes from reflectance data.
Our proposed approach based on freely available satellite data calibrated by low-cost automated drone technology can provide reasonably accurate estimates of surface grain size for bar sediments in medium to large river channels, over lengths of hundreds of kilometers. Moreover, the proposed methodology is easily replicable to other natural environments where an extensive grain size distribution assessment is crucial to understand geomorphic processes, thus providing a new technique for collecting such precious data and support studies of landscape evolution.
How to cite: Marchetti, G., Bizzi, S., Belletti, B., Lastoria, B., Mariani, S., Casaioli, M., Comiti, F., and Carbonneau, P.: Machine learning-based grain size mapping from satellite images , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14945, https://doi.org/10.5194/egusphere-egu21-14945, 2021.
A comprehensive understanding of river dynamics requires the quantitative knowledge of the grain size distribution of bed sediments and its variation across multiple temporal and spatial scales. Several techniques are already available for grain size assessment based on field and remotely sensed data. However, the existing methods permit to cover small areas and short time scale, thus the operational measurement of grain size distribution of river bed sediments at the catchment scale remains an open problem. A solution could be the use of satellite images but very limited investigations have been carried out so far on the use of satellite-based sub-pixel mapping of river characteristics relevant to ecohydraulic processes.
In this study, we propose a new approach to retrieve sub-pixel scale grain size classes information from Sentinel 2 imagery building upon a new image-based grain size mapping procedure. Four Italian gravel-bed rivers featuring different morphology were selected to conduct UAV acquisitions and extract ground truth grain size data from the near-ground images, by photo-sieving techniques. We generated grain size maps at the resolution of 2 cm on river bars in each study site by exploiting image texture measurements, and subsequently resampled and co-registered the grain size maps with Sentinel 2 data resolution.
Relationships between the grain sizes measured and the reflectance values in Sentinel 2 imagery - available in 11 bands super resolved at 10 m resolution – were analyzed. Based on these, our first results show statistically significant predictive models (cross validation results: MAE of 3.38 ± 13.4 mm and R2=0.48) by using a machine learning framework (Support Vector Machine) to retrieve grain size classes from reflectance data.
Our proposed approach based on freely available satellite data calibrated by low-cost automated drone technology can provide reasonably accurate estimates of surface grain size for bar sediments in medium to large river channels, over lengths of hundreds of kilometers. Moreover, the proposed methodology is easily replicable to other natural environments where an extensive grain size distribution assessment is crucial to understand geomorphic processes, thus providing a new technique for collecting such precious data and support studies of landscape evolution.
How to cite: Marchetti, G., Bizzi, S., Belletti, B., Lastoria, B., Mariani, S., Casaioli, M., Comiti, F., and Carbonneau, P.: Machine learning-based grain size mapping from satellite images , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14945, https://doi.org/10.5194/egusphere-egu21-14945, 2021.
EGU21-2728 | vPICO presentations | GM2.7
Using convolutional neural networks to detect giant landslides in the Patagonian Andean forelandElisabeth Schönfeldt, Tomáš Pánek, Diego Winocur, and Oliver Korup
The Andean foreland of Patagonia features dozens of basaltic plateaus that are spread out from the Argentinean province of Neuquén south to Tierra del Fuego. The plateau margins are undermined by numerous giant slope failures that mostly involved a combination of lateral spreading and rotational sliding, running out up to several kilometres along the plateau margins. However, the overall extent of plateau margins affected by landsliding is still unknown, because manual mapping of such a large area (~500.000 km²) is time-consuming. Therefore, our goal is to test methods that support manual mapping by an automatic and objective detection of giant landslides. All of these landslides share very similar topographic features such as subparallel compression ridges and elongate depressions, distinguishing them in terms of their topographic and optical appearance from surrounding areas (e.g. plains or plateau tops). Using a catalogue of these features, we tested an image classification scheme using convolutional neural networks (CNNs). Our input data consist of Sentinel-2 optical data (20-m resolution) and topographic factors (surface roughness and curvature) acquired from TanDEM-X data (12-m resolution). We applied transfer learning, modifying the pre-existing CNN alexnet to test how well it is able to distinguish different geomorphic features such as unstable terrain from plateau tops or plains. Over 4000 training images were extracted from the Meseta Somuncurá, while the trained algorithm was tested at the Sierra Cuadrada. Both plateaus are part of the Northern Patagonia Massif. Preliminary results show that the modified algorithms performs reasonable and is able to distinguish between giant landslides and other geomorphic features. However, performance strongly depends on the training options of the stochastic gradient descent within the CNN and image quality of the training images, especially the quantity of images and their extracted location with respect to the plateau margin.
How to cite: Schönfeldt, E., Pánek, T., Winocur, D., and Korup, O.: Using convolutional neural networks to detect giant landslides in the Patagonian Andean foreland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2728, https://doi.org/10.5194/egusphere-egu21-2728, 2021.
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The Andean foreland of Patagonia features dozens of basaltic plateaus that are spread out from the Argentinean province of Neuquén south to Tierra del Fuego. The plateau margins are undermined by numerous giant slope failures that mostly involved a combination of lateral spreading and rotational sliding, running out up to several kilometres along the plateau margins. However, the overall extent of plateau margins affected by landsliding is still unknown, because manual mapping of such a large area (~500.000 km²) is time-consuming. Therefore, our goal is to test methods that support manual mapping by an automatic and objective detection of giant landslides. All of these landslides share very similar topographic features such as subparallel compression ridges and elongate depressions, distinguishing them in terms of their topographic and optical appearance from surrounding areas (e.g. plains or plateau tops). Using a catalogue of these features, we tested an image classification scheme using convolutional neural networks (CNNs). Our input data consist of Sentinel-2 optical data (20-m resolution) and topographic factors (surface roughness and curvature) acquired from TanDEM-X data (12-m resolution). We applied transfer learning, modifying the pre-existing CNN alexnet to test how well it is able to distinguish different geomorphic features such as unstable terrain from plateau tops or plains. Over 4000 training images were extracted from the Meseta Somuncurá, while the trained algorithm was tested at the Sierra Cuadrada. Both plateaus are part of the Northern Patagonia Massif. Preliminary results show that the modified algorithms performs reasonable and is able to distinguish between giant landslides and other geomorphic features. However, performance strongly depends on the training options of the stochastic gradient descent within the CNN and image quality of the training images, especially the quantity of images and their extracted location with respect to the plateau margin.
How to cite: Schönfeldt, E., Pánek, T., Winocur, D., and Korup, O.: Using convolutional neural networks to detect giant landslides in the Patagonian Andean foreland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2728, https://doi.org/10.5194/egusphere-egu21-2728, 2021.
EGU21-13635 | vPICO presentations | GM2.7
Landslide detection by machine learning on high-resolution DEMsMihai Niculita
Machine learning algorithms are increasingly used in geosciences for the detection of susceptibility modeling of certain landforms or processes. The increased availability of high-resolution data and the increase of available machine learning algorithms opens up the possibility of creating datasets for the training of models for automatic detection of specific landforms. In this study, we tested the usage of LiDAR DEMs for creating a dataset of labeled images representing shallow single event landslides in order to use them for the detection of other events. The R stat implementation of the keras high-level neural networks API was used to build and test the proposed approach. A 5m LiDAR DEM was cut in 25 by 25 pixels tiles, and the tiles that overlayed shallow single event landslides were labeled accordingly, while the tiles that did not contain landslides were randomly selected to be labeled as non-landslides. The binary classification approach was tested with 255 grey levels elevation images and 255 grey levels shading images, the shading approach giving better results. The presented study case shows the possibility of using machine learning in the landslide detection on high-resolution DEMs.
How to cite: Niculita, M.: Landslide detection by machine learning on high-resolution DEMs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13635, https://doi.org/10.5194/egusphere-egu21-13635, 2021.
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Machine learning algorithms are increasingly used in geosciences for the detection of susceptibility modeling of certain landforms or processes. The increased availability of high-resolution data and the increase of available machine learning algorithms opens up the possibility of creating datasets for the training of models for automatic detection of specific landforms. In this study, we tested the usage of LiDAR DEMs for creating a dataset of labeled images representing shallow single event landslides in order to use them for the detection of other events. The R stat implementation of the keras high-level neural networks API was used to build and test the proposed approach. A 5m LiDAR DEM was cut in 25 by 25 pixels tiles, and the tiles that overlayed shallow single event landslides were labeled accordingly, while the tiles that did not contain landslides were randomly selected to be labeled as non-landslides. The binary classification approach was tested with 255 grey levels elevation images and 255 grey levels shading images, the shading approach giving better results. The presented study case shows the possibility of using machine learning in the landslide detection on high-resolution DEMs.
How to cite: Niculita, M.: Landslide detection by machine learning on high-resolution DEMs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13635, https://doi.org/10.5194/egusphere-egu21-13635, 2021.
EGU21-4296 | vPICO presentations | GM2.7
How to reconstruct geometrical characteristics and failure conditions of an historic atypical complex flow-like landslide: example of the Déboulé of La Ravine de l’Eglise (La Réunion Island, France).Claire Rault, Yannick Thiery, Thomas Dewez, Kahina Reboul, and Bertrand Aunay
The reconstruction of scenarios of historical hazardous landslide and erosion processes is a milestone to understand their formation, and perform an appropriate hazard assessment. Here, we focus on the possible conditions that lead to a dramatic cyclone-induced gullying event on La Reunion volcanic island in the Indian Ocean.
In Cirque de Salazie, the Ravine de l’Eglise is a gully of 720 m long and 40 m wide. It formed in just the few days the cyclone Hyacinthe lasted from 15th of January to 27th of January 1980. Hyacinthe drenched Grand-Ilet with world-record-type rainfalls: 5254 mm in 12 days on Grand-Ilet, with a maximum of 1044 mm in one day. This sudden gullying phenomenon, locally called “Déboulé”, poses a substantial threat to local dwellings and inhabitants. Grasping the conditions that lead to such dramatic process is a pre-requisite to mitigating the risks.
The heterogeneous properties of coarse volcanic materials, the complexity of the structural characteristics of the terrain and its hydrogeology make Déboulé a phenomenon that is difficult to understand and anticipate. As this rare, fast and hazardous cyclonic circumstances process cannot be observed in-situ, scenarios combining physically based hydrogeological and slope stability models are explored to describe conditions to form and propagate a Déboulé. The development of such integrated models requires the description of initial conditions that led to the event (rainfall amount, morphology of the terrain and its mechanical and hydrological characteristics) and also a detailed geometry of the gully to validate the simulation output.
In this communication, we present the methods used (1) to document the geometry of the Déboulé of La Ravine de l’Eglise (2) the morphological and hydrological triggering conditions of this event.
The original and final topography where the Déboulé of la Ravine de l’Eglise occurred was reconstructed with ca. 1/27 000 archive aerial photographs taken before (1978) and after (1984) the cyclone above Grand-Ilet. Using Structure-from-Motion processing on these two sets of archived images, we build historical digital surface models and ortho-photographs to retrieve quantitative metrics of the landscape evolution caused by the cyclone. The mass wasted during the Déboulé is ca. 0.6 Mm3 ± 0.1 Mm3.We also access to the morphology of the area before the event allowing to identify conditions favorable to the initiation of such phenomenon such as closed depressions, lineaments and regressive erosion lining up the future gully and steep slope breaks.
The hydrogeological conditions of Grand-Ilet during Hyacinthe that caused the Déboulé, are simulated using GARDENIA, a BRGM application for lumped hydrologic modelling. The historic water table levels, especially that under Hyacinthe rainfall, are hindcast considering the rainfalls since 1978 and water table measured in a piezometer since 2010. The hindcast water reported on the reconstructed topography of 1978, crosses the bottom of the embankment that collapsed during Hyacinthe.
The reconstructed topographies and the hindcast water level are consistent with field evidences. Our results document and propose for the first time a quantification the geometry of a Déboulé and bring insight for the initiation of such process.
How to cite: Rault, C., Thiery, Y., Dewez, T., Reboul, K., and Aunay, B.: How to reconstruct geometrical characteristics and failure conditions of an historic atypical complex flow-like landslide: example of the Déboulé of La Ravine de l’Eglise (La Réunion Island, France). , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4296, https://doi.org/10.5194/egusphere-egu21-4296, 2021.
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The reconstruction of scenarios of historical hazardous landslide and erosion processes is a milestone to understand their formation, and perform an appropriate hazard assessment. Here, we focus on the possible conditions that lead to a dramatic cyclone-induced gullying event on La Reunion volcanic island in the Indian Ocean.
In Cirque de Salazie, the Ravine de l’Eglise is a gully of 720 m long and 40 m wide. It formed in just the few days the cyclone Hyacinthe lasted from 15th of January to 27th of January 1980. Hyacinthe drenched Grand-Ilet with world-record-type rainfalls: 5254 mm in 12 days on Grand-Ilet, with a maximum of 1044 mm in one day. This sudden gullying phenomenon, locally called “Déboulé”, poses a substantial threat to local dwellings and inhabitants. Grasping the conditions that lead to such dramatic process is a pre-requisite to mitigating the risks.
The heterogeneous properties of coarse volcanic materials, the complexity of the structural characteristics of the terrain and its hydrogeology make Déboulé a phenomenon that is difficult to understand and anticipate. As this rare, fast and hazardous cyclonic circumstances process cannot be observed in-situ, scenarios combining physically based hydrogeological and slope stability models are explored to describe conditions to form and propagate a Déboulé. The development of such integrated models requires the description of initial conditions that led to the event (rainfall amount, morphology of the terrain and its mechanical and hydrological characteristics) and also a detailed geometry of the gully to validate the simulation output.
In this communication, we present the methods used (1) to document the geometry of the Déboulé of La Ravine de l’Eglise (2) the morphological and hydrological triggering conditions of this event.
The original and final topography where the Déboulé of la Ravine de l’Eglise occurred was reconstructed with ca. 1/27 000 archive aerial photographs taken before (1978) and after (1984) the cyclone above Grand-Ilet. Using Structure-from-Motion processing on these two sets of archived images, we build historical digital surface models and ortho-photographs to retrieve quantitative metrics of the landscape evolution caused by the cyclone. The mass wasted during the Déboulé is ca. 0.6 Mm3 ± 0.1 Mm3.We also access to the morphology of the area before the event allowing to identify conditions favorable to the initiation of such phenomenon such as closed depressions, lineaments and regressive erosion lining up the future gully and steep slope breaks.
The hydrogeological conditions of Grand-Ilet during Hyacinthe that caused the Déboulé, are simulated using GARDENIA, a BRGM application for lumped hydrologic modelling. The historic water table levels, especially that under Hyacinthe rainfall, are hindcast considering the rainfalls since 1978 and water table measured in a piezometer since 2010. The hindcast water reported on the reconstructed topography of 1978, crosses the bottom of the embankment that collapsed during Hyacinthe.
The reconstructed topographies and the hindcast water level are consistent with field evidences. Our results document and propose for the first time a quantification the geometry of a Déboulé and bring insight for the initiation of such process.
How to cite: Rault, C., Thiery, Y., Dewez, T., Reboul, K., and Aunay, B.: How to reconstruct geometrical characteristics and failure conditions of an historic atypical complex flow-like landslide: example of the Déboulé of La Ravine de l’Eglise (La Réunion Island, France). , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4296, https://doi.org/10.5194/egusphere-egu21-4296, 2021.
EGU21-14468 | vPICO presentations | GM2.7
HYPSO: a new multiresolution global raster digital elevation model for small-scale terrain mappingTimofey Samsonov
During the last decade a significant progress in methods and techniques of elevation data acquisition has been achieved. With lidar-derived digital elevation models it is now possible to investigate landforms with precision and detail which was never possible before. The resolution of global and continental elevation models is approaching first meters, which enables detailed geomorphometric analysis and mapping in wide spatial extents. At the same time, Earth scientists are interested not only in learning the properties of small landforms, but also in investigating the large regional terrain features, as well as hierarchical properties of terrain structure. For this, small details must be omitted from digital elevation model, and the analyzed dataset is expected to have coarser resolution. Currently available coarse-resolution global digital elevation models such as GMTED2010, GEBCO_2019 and ETOPO1 are characterized by spatial resolution ranging from 7.5” to 1’, which is approximately equal to cell size of 250-2000 m on the equator. Such resolution fits well into the small-scale mapping and analysis context. However, these models have excessive level of detail in relation to their resolution, which is a consequence of the method of their derivation — mainly aggregation and resampling of more detailed data. As a result, terrain maps created using these models, are characterized by lack of generalization, which prevents realistic portray of large terrain forms. To solve the problem, the new high-quality mutiresolution digital elevation model HYPSO has been developed. HYPSO is derived based on GEBCO_2019 model (15” resolution) using the structural generalization, during which the less detailed terrain surface is reconstructed from characteristic stream and watershed lines. HYPSO includes eight levels of detail (LoDs) with resolutions 30”, 1’, 2’, 4’, 8’, 16’, 32’ and 64’ which are suitable for mapping any region on the Earth including the seabed at scales 1:1 000 000 and smaller. The sequence of LoDs is characterized by sequential decrease in detail, which enables production of multiscale maps. Additionally, HYPSO is spatially conflated with river/lake centerlines in popular Natural Earth cartographic database and can be used as a background terrain layer in production of general geographic (base) maps. While the primary purpose of HYPSO is hypsometric mapping, it is also suitable as a data source for performing the geomorphometric analysis aimed at investigating the properties of large terrain landforms, which is demonstrated on several examples.
The study was supported by the Russian Science Foundation grant No. 19-77-10071
How to cite: Samsonov, T.: HYPSO: a new multiresolution global raster digital elevation model for small-scale terrain mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14468, https://doi.org/10.5194/egusphere-egu21-14468, 2021.
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During the last decade a significant progress in methods and techniques of elevation data acquisition has been achieved. With lidar-derived digital elevation models it is now possible to investigate landforms with precision and detail which was never possible before. The resolution of global and continental elevation models is approaching first meters, which enables detailed geomorphometric analysis and mapping in wide spatial extents. At the same time, Earth scientists are interested not only in learning the properties of small landforms, but also in investigating the large regional terrain features, as well as hierarchical properties of terrain structure. For this, small details must be omitted from digital elevation model, and the analyzed dataset is expected to have coarser resolution. Currently available coarse-resolution global digital elevation models such as GMTED2010, GEBCO_2019 and ETOPO1 are characterized by spatial resolution ranging from 7.5” to 1’, which is approximately equal to cell size of 250-2000 m on the equator. Such resolution fits well into the small-scale mapping and analysis context. However, these models have excessive level of detail in relation to their resolution, which is a consequence of the method of their derivation — mainly aggregation and resampling of more detailed data. As a result, terrain maps created using these models, are characterized by lack of generalization, which prevents realistic portray of large terrain forms. To solve the problem, the new high-quality mutiresolution digital elevation model HYPSO has been developed. HYPSO is derived based on GEBCO_2019 model (15” resolution) using the structural generalization, during which the less detailed terrain surface is reconstructed from characteristic stream and watershed lines. HYPSO includes eight levels of detail (LoDs) with resolutions 30”, 1’, 2’, 4’, 8’, 16’, 32’ and 64’ which are suitable for mapping any region on the Earth including the seabed at scales 1:1 000 000 and smaller. The sequence of LoDs is characterized by sequential decrease in detail, which enables production of multiscale maps. Additionally, HYPSO is spatially conflated with river/lake centerlines in popular Natural Earth cartographic database and can be used as a background terrain layer in production of general geographic (base) maps. While the primary purpose of HYPSO is hypsometric mapping, it is also suitable as a data source for performing the geomorphometric analysis aimed at investigating the properties of large terrain landforms, which is demonstrated on several examples.
The study was supported by the Russian Science Foundation grant No. 19-77-10071
How to cite: Samsonov, T.: HYPSO: a new multiresolution global raster digital elevation model for small-scale terrain mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14468, https://doi.org/10.5194/egusphere-egu21-14468, 2021.
EGU21-4976 | vPICO presentations | GM2.7
Semi-automated past landscape visualizations for the Netherlands: solutions to keep national overviews actual and in-syncKim Cohen, Harm-Jan Pierik, Hessel Woolderink, Jelle Moree, and Hugo Cox
Overwhelming amounts of geological and geomorphological data have accumulated over the last ca. 160 years for the Netherlands. Also, the amounts and diversity of digital map products summarizing all this data also have grown overwhelmingly. Combining, updating and synchronizing the various information sources while keeping matters user-friendly is a challenge. We present the current status of our GIS solutions for managing landform age information and performing palaeogeographical analysis utilizing past landscape visualizations (i.e. query-generated map time series).
Our mapping uses so-called base maps connected to landform catalogue database to store information, which are published as open data. Base maps and catalogues are to be kept up-to-date with new actual data through iterative manual revision, and are ‘living’ datasets. For palaeogeographical analysis we query the base maps and recombine subselections using scripts. This generates derived map series in which the information is arranged for the analysis, which independently gets open data status. To allow communal maintenance of the information, we designed interfaces to the landform catalogue databases of our base maps to make them editable in wiki-style (i.e.: ‘non-static open data’).
Attitudes like this are needed to get the most out of accumulating data and overcome integration, actuality and divergence challenges felt by users working with different maps claimed to be based on the same shared body of geodata generated in densely populated lowland countries.
How to cite: Cohen, K., Pierik, H.-J., Woolderink, H., Moree, J., and Cox, H.: Semi-automated past landscape visualizations for the Netherlands: solutions to keep national overviews actual and in-sync, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4976, https://doi.org/10.5194/egusphere-egu21-4976, 2021.
Overwhelming amounts of geological and geomorphological data have accumulated over the last ca. 160 years for the Netherlands. Also, the amounts and diversity of digital map products summarizing all this data also have grown overwhelmingly. Combining, updating and synchronizing the various information sources while keeping matters user-friendly is a challenge. We present the current status of our GIS solutions for managing landform age information and performing palaeogeographical analysis utilizing past landscape visualizations (i.e. query-generated map time series).
Our mapping uses so-called base maps connected to landform catalogue database to store information, which are published as open data. Base maps and catalogues are to be kept up-to-date with new actual data through iterative manual revision, and are ‘living’ datasets. For palaeogeographical analysis we query the base maps and recombine subselections using scripts. This generates derived map series in which the information is arranged for the analysis, which independently gets open data status. To allow communal maintenance of the information, we designed interfaces to the landform catalogue databases of our base maps to make them editable in wiki-style (i.e.: ‘non-static open data’).
Attitudes like this are needed to get the most out of accumulating data and overcome integration, actuality and divergence challenges felt by users working with different maps claimed to be based on the same shared body of geodata generated in densely populated lowland countries.
How to cite: Cohen, K., Pierik, H.-J., Woolderink, H., Moree, J., and Cox, H.: Semi-automated past landscape visualizations for the Netherlands: solutions to keep national overviews actual and in-sync, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4976, https://doi.org/10.5194/egusphere-egu21-4976, 2021.
EGU21-6067 | vPICO presentations | GM2.7
Dunes as palaeo-wind vanes: Investigating palaeowind regimes using semi-automated remote sensing approaches to dunefield mapping and orientation quantificationMaike Nowatzki, Kathryn Fitzsimmons, Hartwig Harder, and Hans-Joachim Rosner
Many dryland regions of the world are at high risk of desertification from combined human land use and anthropogenic climate change. One symptom of desertification is the reactivation of previously stable dunefields. Since morphologies of stable dunes are thought to reflect wind regimes at the time of their formation, the degree to which dune orientation reflects modern winds may be one way to assess changes in wind regimes and the progression of desertification in a region.
Here we investigate the relationship between wind dynamics and desert dune orientation in one region at risk of desertification, southeast Kazakhstan in Central Asia, on the basis of open-source software and open-access datasets. Using Google Earth Engine, we map dunes or interdune spaces within six palaeo-dunefields in the Ili-Balkhash area, by performing a multi-layer object-based image analysis (OBIA) on satellite remote sensing data (Sentinel-2 optical imagery and SRTM digital elevation models). A semi-automated GIS approach is used to undertake data cleansing and the quantification of dominant palaeo-dunefield orientations. The resulting orientation trends are concurrent with the region’s topography: The dunefields within the Ili valley show a narrow, mostly E-W oriented trend concurrent with the course of the valley while the orientation ranges become broader towards the open pre-Balkhash area.
We then predict modern dune orientations by applying the maximum gross bedform-normal transport rule on reanalysed wind data for 2008-2018. This approach by Rubin and Hunter (1987) allows the deduction of sand transport and resulting bedform trends from wind direction frequencies. The predicted modern orientation trends for the dunefields in the Ili-Balkhash area yield only partial consensus with observed palaeo-bedform trends. We therefore propose that modern wind regimes are not exclusively responsible for existing dune morphologies in the region, and that dune orientation may be inherited from earlier wind regimes.
How to cite: Nowatzki, M., Fitzsimmons, K., Harder, H., and Rosner, H.-J.: Dunes as palaeo-wind vanes: Investigating palaeowind regimes using semi-automated remote sensing approaches to dunefield mapping and orientation quantification , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6067, https://doi.org/10.5194/egusphere-egu21-6067, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Many dryland regions of the world are at high risk of desertification from combined human land use and anthropogenic climate change. One symptom of desertification is the reactivation of previously stable dunefields. Since morphologies of stable dunes are thought to reflect wind regimes at the time of their formation, the degree to which dune orientation reflects modern winds may be one way to assess changes in wind regimes and the progression of desertification in a region.
Here we investigate the relationship between wind dynamics and desert dune orientation in one region at risk of desertification, southeast Kazakhstan in Central Asia, on the basis of open-source software and open-access datasets. Using Google Earth Engine, we map dunes or interdune spaces within six palaeo-dunefields in the Ili-Balkhash area, by performing a multi-layer object-based image analysis (OBIA) on satellite remote sensing data (Sentinel-2 optical imagery and SRTM digital elevation models). A semi-automated GIS approach is used to undertake data cleansing and the quantification of dominant palaeo-dunefield orientations. The resulting orientation trends are concurrent with the region’s topography: The dunefields within the Ili valley show a narrow, mostly E-W oriented trend concurrent with the course of the valley while the orientation ranges become broader towards the open pre-Balkhash area.
We then predict modern dune orientations by applying the maximum gross bedform-normal transport rule on reanalysed wind data for 2008-2018. This approach by Rubin and Hunter (1987) allows the deduction of sand transport and resulting bedform trends from wind direction frequencies. The predicted modern orientation trends for the dunefields in the Ili-Balkhash area yield only partial consensus with observed palaeo-bedform trends. We therefore propose that modern wind regimes are not exclusively responsible for existing dune morphologies in the region, and that dune orientation may be inherited from earlier wind regimes.
How to cite: Nowatzki, M., Fitzsimmons, K., Harder, H., and Rosner, H.-J.: Dunes as palaeo-wind vanes: Investigating palaeowind regimes using semi-automated remote sensing approaches to dunefield mapping and orientation quantification , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6067, https://doi.org/10.5194/egusphere-egu21-6067, 2021.
EGU21-6517 | vPICO presentations | GM2.7
Ice sheet unzipping in the mountain-piedmont region of west-central Sweden: complex late-deglaciation of the Scandinavian ice sheetRobin Blomdin, Gustaf Peterson Becher, Colby Smith, Carl Regnéll, Christian Öhrling, and Bradley Goodfellow
Regional-scale glacial geomorphological maps provide important empirical data for reconstructions of former ice sheets, which may serve as analogues for the behaviour of modern ice sheets under climate warming. In particular, the extensive LiDAR-derived record of former ice sheet beds, provides an outstanding archive from which to infer former ice sheet behaviour. The stacking together and analysis of, tens of thousands of individual landforms, based on their spatial coherency, provides a powerful tool to reconstruct ice flow dynamics, temporally evolving ice divide positions and the “unzipping” of ice sheets into separate masses during deglaciation. In this study, we develop a glacial geomorphological dataset focussing on the mountain-piedmont region of Jämtland in west-central Sweden. We focus on this region because it is where the last (Weichselian) ice sheet is believed to have unzipped into separate domes and was inundated by vast ice dammed lakes. Jämtland also records a complex temporal evolution of subglacial processes and was formerly mapped without the benefit of a LiDAR-based elevation model. The dataset was created by mapping in GIS and covers an area of 50 000 km2 and almost 88 000 landforms, including glacial lineations, crag-and-tails, ice marginal moraines, lateral meltwater channels, eskers, and glacial lake shorelines. We use this unique dataset–in terms of spatial density and resolution–and quantitatively analyse cross-cutting relationships to establish a relative ice flow chronology. Our key findings include 1) a previously unmapped landform system, formed by the Early-to-Middle Weichselian westward expansion of a mountain centred ice sheet, and 2) a complex early Holocene deglaciation sequence with ice sheet unzipping occurring in southern and east-central Jämtland. The ice sheet split into a larger sheet retreating northward and a smaller ice sheet remaining southeast of the mountain piedmont. Our results provide new insights into the late deglaciation of the Scandinavian Ice Sheet.
How to cite: Blomdin, R., Peterson Becher, G., Smith, C., Regnéll, C., Öhrling, C., and Goodfellow, B.: Ice sheet unzipping in the mountain-piedmont region of west-central Sweden: complex late-deglaciation of the Scandinavian ice sheet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6517, https://doi.org/10.5194/egusphere-egu21-6517, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Regional-scale glacial geomorphological maps provide important empirical data for reconstructions of former ice sheets, which may serve as analogues for the behaviour of modern ice sheets under climate warming. In particular, the extensive LiDAR-derived record of former ice sheet beds, provides an outstanding archive from which to infer former ice sheet behaviour. The stacking together and analysis of, tens of thousands of individual landforms, based on their spatial coherency, provides a powerful tool to reconstruct ice flow dynamics, temporally evolving ice divide positions and the “unzipping” of ice sheets into separate masses during deglaciation. In this study, we develop a glacial geomorphological dataset focussing on the mountain-piedmont region of Jämtland in west-central Sweden. We focus on this region because it is where the last (Weichselian) ice sheet is believed to have unzipped into separate domes and was inundated by vast ice dammed lakes. Jämtland also records a complex temporal evolution of subglacial processes and was formerly mapped without the benefit of a LiDAR-based elevation model. The dataset was created by mapping in GIS and covers an area of 50 000 km2 and almost 88 000 landforms, including glacial lineations, crag-and-tails, ice marginal moraines, lateral meltwater channels, eskers, and glacial lake shorelines. We use this unique dataset–in terms of spatial density and resolution–and quantitatively analyse cross-cutting relationships to establish a relative ice flow chronology. Our key findings include 1) a previously unmapped landform system, formed by the Early-to-Middle Weichselian westward expansion of a mountain centred ice sheet, and 2) a complex early Holocene deglaciation sequence with ice sheet unzipping occurring in southern and east-central Jämtland. The ice sheet split into a larger sheet retreating northward and a smaller ice sheet remaining southeast of the mountain piedmont. Our results provide new insights into the late deglaciation of the Scandinavian Ice Sheet.
How to cite: Blomdin, R., Peterson Becher, G., Smith, C., Regnéll, C., Öhrling, C., and Goodfellow, B.: Ice sheet unzipping in the mountain-piedmont region of west-central Sweden: complex late-deglaciation of the Scandinavian ice sheet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6517, https://doi.org/10.5194/egusphere-egu21-6517, 2021.
EGU21-5966 | vPICO presentations | GM2.7
Mapping a Duck: Geological Features and Region Definitions on Comet 67P/Churyumov-GerasimenkoBjörn Grieger, Mireia Leon-Dasi, Sebastien Besse, and Michael Küppers
The data from the Rosetta mission enabled the reconstruction of the shape of comet 67P/Churyumov-Gerasimenko (hereafter 67P) and the identification of the terrains and features forming its surface. The highly irregular shape of the comet poses a challenge for the depiction of these geological features on two-dimensional maps. Standard global map projections cannot display the complete surface of 67P because different points on the surface can have the same longitude and latitude. As a consequence, the geological maps published to date are created on top of comet images, making them dependent on the viewing angle and image coverage and resolution.
Here, we make use of the recently published Quincuncial Adaptive Closed Kohonen (QuACK) map. It projects the complete surface of 67P unambiguously onto a square. The QuACK map is topologically equivalent to the Peirce quincuncial projection of the world, which makes it possible to define generalized longitudes and latitudes. These can be used within any global map projection in order to obtain an unambiguous QuACK version.
The mapping of geological features is carried out in three dimensions employing the Small Body Mapping Tool (SBMT). We use images from the OSIRIS Narrow Angle Camera aboard Rosetta which have been projected onto the shape model of the SBMT. The three-dimensional coordinates are then projected onto two-dimensional maps, either in the QuACK map projection or in the QuACK version of the equidistant cylindrical projection. We present individual maps for 17 of the 26 regions of 67P, mostly located in the northern hemisphere. The new maps combine features published in previous studies with newly identified features.
We discuss the distribution of geological features and the characteristics of the regions. In order to align region boundaries with geological features, we propose two modifications of region definitions.
How to cite: Grieger, B., Leon-Dasi, M., Besse, S., and Küppers, M.: Mapping a Duck: Geological Features and Region Definitions on Comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5966, https://doi.org/10.5194/egusphere-egu21-5966, 2021.
The data from the Rosetta mission enabled the reconstruction of the shape of comet 67P/Churyumov-Gerasimenko (hereafter 67P) and the identification of the terrains and features forming its surface. The highly irregular shape of the comet poses a challenge for the depiction of these geological features on two-dimensional maps. Standard global map projections cannot display the complete surface of 67P because different points on the surface can have the same longitude and latitude. As a consequence, the geological maps published to date are created on top of comet images, making them dependent on the viewing angle and image coverage and resolution.
Here, we make use of the recently published Quincuncial Adaptive Closed Kohonen (QuACK) map. It projects the complete surface of 67P unambiguously onto a square. The QuACK map is topologically equivalent to the Peirce quincuncial projection of the world, which makes it possible to define generalized longitudes and latitudes. These can be used within any global map projection in order to obtain an unambiguous QuACK version.
The mapping of geological features is carried out in three dimensions employing the Small Body Mapping Tool (SBMT). We use images from the OSIRIS Narrow Angle Camera aboard Rosetta which have been projected onto the shape model of the SBMT. The three-dimensional coordinates are then projected onto two-dimensional maps, either in the QuACK map projection or in the QuACK version of the equidistant cylindrical projection. We present individual maps for 17 of the 26 regions of 67P, mostly located in the northern hemisphere. The new maps combine features published in previous studies with newly identified features.
We discuss the distribution of geological features and the characteristics of the regions. In order to align region boundaries with geological features, we propose two modifications of region definitions.
How to cite: Grieger, B., Leon-Dasi, M., Besse, S., and Küppers, M.: Mapping a Duck: Geological Features and Region Definitions on Comet 67P/Churyumov-Gerasimenko, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5966, https://doi.org/10.5194/egusphere-egu21-5966, 2021.
EGU21-14031 | vPICO presentations | GM2.7
How morphologic variability, a novel metric derived from supervised landform classification, can offer insights into the processes governing fault scarp morphology in jointed rockCassandra Brigham and Juliet Crider
Fault scarps are steps in the landscape created by surface-rupturing faults. Study of their morphology can supply paleoseismic information, such as the timing and size of past events, but the form of a single fault scarp can show great variability along the length of the scarp, complicating its interpretation. We developed a methodology to quantify this variability: scarp-normal profiles are extracted from point clouds, their shape is automatically classified using a supervised learning algorithm, and these classification results are used to calculate the morphologic variability metric, a measure of the frequency and degree of change in profile form along strike.
Using point clouds derived from structure-from-motion photogrammetry, we computed the morphologic variability along thirteen jointed-bedrock fault scarps from four field sites, located in southwestern Iceland, northern and central California, and southeastern Hawai’i. Quantifiable characteristics such as climate, vegetation, lithology, fault throw, and fracture spacing change either internally along a single scarp or between these four sites.
In an individual scarp, we make pairwise comparisons between measurements of a characteristic and the morphologic variability: a strong correlation between the two indicates that this characteristic is an important driver of scarp form. For example, in the young Icelandic scarps, scarp throw is correlated with morphologic variability, suggesting that the initial slip distribution along a fault contributes to the variability in the profile forms of younger scarps. We also compute the fracture intensity and orientation along the scarps and hypothesize that increased fracture spacing leads to decreased morphologic variability.
To understand variation between sites, we make pairwise comparisons between the average values of morphologic variability of the scarps and site-specific characteristics. For example, maximum scarp throw is negatively correlated with average morphologic variability, suggesting that scarp profile form evolves towards a common morphology as scarps mature.
We show that the morphologic variability metric is a useful tool to understand the agents responsible for changes in scarp form, an essential step in accurately interpreting any paleoseismic information that might be present. Morphologic variability is a metric that can be determined for any other type of linear landform (e.g. coastal bluffs or cross-channel profiles) and our approach of linking morphologic variability to process is applicable to a wide array of geomorphic questions.
How to cite: Brigham, C. and Crider, J.: How morphologic variability, a novel metric derived from supervised landform classification, can offer insights into the processes governing fault scarp morphology in jointed rock , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14031, https://doi.org/10.5194/egusphere-egu21-14031, 2021.
Fault scarps are steps in the landscape created by surface-rupturing faults. Study of their morphology can supply paleoseismic information, such as the timing and size of past events, but the form of a single fault scarp can show great variability along the length of the scarp, complicating its interpretation. We developed a methodology to quantify this variability: scarp-normal profiles are extracted from point clouds, their shape is automatically classified using a supervised learning algorithm, and these classification results are used to calculate the morphologic variability metric, a measure of the frequency and degree of change in profile form along strike.
Using point clouds derived from structure-from-motion photogrammetry, we computed the morphologic variability along thirteen jointed-bedrock fault scarps from four field sites, located in southwestern Iceland, northern and central California, and southeastern Hawai’i. Quantifiable characteristics such as climate, vegetation, lithology, fault throw, and fracture spacing change either internally along a single scarp or between these four sites.
In an individual scarp, we make pairwise comparisons between measurements of a characteristic and the morphologic variability: a strong correlation between the two indicates that this characteristic is an important driver of scarp form. For example, in the young Icelandic scarps, scarp throw is correlated with morphologic variability, suggesting that the initial slip distribution along a fault contributes to the variability in the profile forms of younger scarps. We also compute the fracture intensity and orientation along the scarps and hypothesize that increased fracture spacing leads to decreased morphologic variability.
To understand variation between sites, we make pairwise comparisons between the average values of morphologic variability of the scarps and site-specific characteristics. For example, maximum scarp throw is negatively correlated with average morphologic variability, suggesting that scarp profile form evolves towards a common morphology as scarps mature.
We show that the morphologic variability metric is a useful tool to understand the agents responsible for changes in scarp form, an essential step in accurately interpreting any paleoseismic information that might be present. Morphologic variability is a metric that can be determined for any other type of linear landform (e.g. coastal bluffs or cross-channel profiles) and our approach of linking morphologic variability to process is applicable to a wide array of geomorphic questions.
How to cite: Brigham, C. and Crider, J.: How morphologic variability, a novel metric derived from supervised landform classification, can offer insights into the processes governing fault scarp morphology in jointed rock , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14031, https://doi.org/10.5194/egusphere-egu21-14031, 2021.
EGU21-11959 | vPICO presentations | GM2.7
Bird’s eye view on steep topographyAnne Voigtländer and Stefanie Tofelde
In nadir view, normal to topography, landscapes with gentle slopes and those with steep surfaces look similar. This is due to the projection of a 3D structure onto a 2D plane. In orthophotos and digital elevation models (DEMs) topography is represented in this nadir or bird’s eye perspective. Elevation models of the Earth or planetary surfaces are often represented by gridded cells, each cell assigned with a mean elevation. In geomorphic studies, DEMs are widely used to calculate hillslope angles and surface area. Due to the projection, hillslopes at a steeper angle appear shorter and thus are represented by a smaller fraction of grid cells. Consequently, mean or median hillslope angles are distorted towards gentle slopes. This bias becomes even more obvious when comparing the projected 2D surface area versus the 3D surface area. The ratio by which a 3D surface area is underrepresented in 2D is by the cosine of the slope of the plane. Hence, the degree of area under-representation increases towards steeper slopes. At an angle of 60°, theoretically only half of the 3D surface area would be accounted for in a gridded DEM. And a hillslope at 90° is a no-show in the DEM. But already gentle slopes of 20° to 30° would be under-represented by about 10%. In addition to the under-representation of steep slopes due to the projection, DEM’s spatial resolution amplifies this bias where increasing grid size decreases the representation of steep slopes.
In essence, due to the bird’s eye view, measures of hillslope angle distribution and surface area have a bias disadvantaging steep slopes and skewing our perception towards a (flat) world of gentle slopes. Here we will discuss if and by how much this bias due to the bird’s eye view matters. First, we investigate artificial DEMs of Gaussian hills. We compare slope and surface area values using standard methods of gridded-data analysis to analytical solutions. Second, we investigate the impact of under-representation on a range of natural landscapes. This potential bias favouring gentle landscape elements has several implications for geomorphological interpretation of DEMs, including for example analyses of average erosion rates, landslide distribution or hydrological processes.
How to cite: Voigtländer, A. and Tofelde, S.: Bird’s eye view on steep topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11959, https://doi.org/10.5194/egusphere-egu21-11959, 2021.
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In nadir view, normal to topography, landscapes with gentle slopes and those with steep surfaces look similar. This is due to the projection of a 3D structure onto a 2D plane. In orthophotos and digital elevation models (DEMs) topography is represented in this nadir or bird’s eye perspective. Elevation models of the Earth or planetary surfaces are often represented by gridded cells, each cell assigned with a mean elevation. In geomorphic studies, DEMs are widely used to calculate hillslope angles and surface area. Due to the projection, hillslopes at a steeper angle appear shorter and thus are represented by a smaller fraction of grid cells. Consequently, mean or median hillslope angles are distorted towards gentle slopes. This bias becomes even more obvious when comparing the projected 2D surface area versus the 3D surface area. The ratio by which a 3D surface area is underrepresented in 2D is by the cosine of the slope of the plane. Hence, the degree of area under-representation increases towards steeper slopes. At an angle of 60°, theoretically only half of the 3D surface area would be accounted for in a gridded DEM. And a hillslope at 90° is a no-show in the DEM. But already gentle slopes of 20° to 30° would be under-represented by about 10%. In addition to the under-representation of steep slopes due to the projection, DEM’s spatial resolution amplifies this bias where increasing grid size decreases the representation of steep slopes.
In essence, due to the bird’s eye view, measures of hillslope angle distribution and surface area have a bias disadvantaging steep slopes and skewing our perception towards a (flat) world of gentle slopes. Here we will discuss if and by how much this bias due to the bird’s eye view matters. First, we investigate artificial DEMs of Gaussian hills. We compare slope and surface area values using standard methods of gridded-data analysis to analytical solutions. Second, we investigate the impact of under-representation on a range of natural landscapes. This potential bias favouring gentle landscape elements has several implications for geomorphological interpretation of DEMs, including for example analyses of average erosion rates, landslide distribution or hydrological processes.
How to cite: Voigtländer, A. and Tofelde, S.: Bird’s eye view on steep topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11959, https://doi.org/10.5194/egusphere-egu21-11959, 2021.
EGU21-6620 | vPICO presentations | GM2.7
Evaluating bedrock outcrop mapping algorithms across diverse landscapesBrittany Selander, Suzanne Anderson, and Matthew Rossi
Mapping bedrock outcrops is useful across disciplines, but is challenging in environments where ground surface visibility is obscured. The presence of soil or bedrock affects sediment production and transport, local ecology, and runoff generation. The distribution of bedrock outcrops in an area reflects the interplay between regolith production and sediment removal. Outcrop classification methods from Terrestrial-lidar produce millimeter or centimeter resolution DEMs that are highly successful because lidar penetrates through vegetation to the ground surface. However, data availability at such high resolution is limited, and the associated computational complexity required for identifying outcrop, or other surface features, is often impractical for landscape-scale analysis. Aerial lidar datasets at ~1-m resolution (e.g., moderate resolution) are more widely available and less computationally expensive than higher resolution datasets. With increasing accessibility of moderate resolution surface data, there is a need to develop outcrop classification methods and understand the efficacy of these methods across diverse environments. Our objectives are to present a simplified technique that builds on existing methods, and to examine the success of current outcrop identification methods in a variety of landscapes.
At moderate resolution, the two most cited metrics to differentiate bedrock from soil-mantled surfaces are based on gradient (e.g., DiBiase et al., 2012) or on surface roughness (e.g., Milodowski et al., 2015). We developed a method that simplifies and combines both metrics, and that improves overall accuracy. We applied all three methods to six landscapes in the USA. For each site, we delineated ground truth from high-resolution orthoimagery for 7-10 test patches with visible ground surface, that evenly spanned 0-100% exposed outcrop. Overall accuracy, true positive rate, and false positive rate for each patch were calculated by comparing the ground truth grids to each lidar-derived outcrop grids on a cell-by-cell basis. Metric success was evaluated for each landscape by assessing the mean and distribution of performance measures across patches. Our combined metric had the highest overall accuracy in an arid, horst and graben landscape (Canyonlands National Park, Utah). It also performed well in a vegetated, high sediment load, active volcano (Mount Rainier, Washington), a canyon carved by channel incision (Boulder Canyon, Colorado), and a chaparral mixed bedrock canyon environment (Mission Trails, San Diego, California). All three methods systematically failed for portions of the landscape in glacially carved canyons (Southern Wind River Range, Wyoming) and on terraced sea cliffs (Santa Cruz County, California). These environments have significant outcrop that is both smooth and low gradient, and therefore cannot be identified using a slope or roughness-based algorithm.
Our work highlights the importance of tailoring DEM-based bedrock mapping algorithms to its geomorphic context, and of the need for ground truth. Such data provides the basis for developing more robust methods for error evaluation. In addition, new methods are needed to identify bedrock outcrop from surface DEMs in smooth and low gradient, yet rocky landscapes.
How to cite: Selander, B., Anderson, S., and Rossi, M.: Evaluating bedrock outcrop mapping algorithms across diverse landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6620, https://doi.org/10.5194/egusphere-egu21-6620, 2021.
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Mapping bedrock outcrops is useful across disciplines, but is challenging in environments where ground surface visibility is obscured. The presence of soil or bedrock affects sediment production and transport, local ecology, and runoff generation. The distribution of bedrock outcrops in an area reflects the interplay between regolith production and sediment removal. Outcrop classification methods from Terrestrial-lidar produce millimeter or centimeter resolution DEMs that are highly successful because lidar penetrates through vegetation to the ground surface. However, data availability at such high resolution is limited, and the associated computational complexity required for identifying outcrop, or other surface features, is often impractical for landscape-scale analysis. Aerial lidar datasets at ~1-m resolution (e.g., moderate resolution) are more widely available and less computationally expensive than higher resolution datasets. With increasing accessibility of moderate resolution surface data, there is a need to develop outcrop classification methods and understand the efficacy of these methods across diverse environments. Our objectives are to present a simplified technique that builds on existing methods, and to examine the success of current outcrop identification methods in a variety of landscapes.
At moderate resolution, the two most cited metrics to differentiate bedrock from soil-mantled surfaces are based on gradient (e.g., DiBiase et al., 2012) or on surface roughness (e.g., Milodowski et al., 2015). We developed a method that simplifies and combines both metrics, and that improves overall accuracy. We applied all three methods to six landscapes in the USA. For each site, we delineated ground truth from high-resolution orthoimagery for 7-10 test patches with visible ground surface, that evenly spanned 0-100% exposed outcrop. Overall accuracy, true positive rate, and false positive rate for each patch were calculated by comparing the ground truth grids to each lidar-derived outcrop grids on a cell-by-cell basis. Metric success was evaluated for each landscape by assessing the mean and distribution of performance measures across patches. Our combined metric had the highest overall accuracy in an arid, horst and graben landscape (Canyonlands National Park, Utah). It also performed well in a vegetated, high sediment load, active volcano (Mount Rainier, Washington), a canyon carved by channel incision (Boulder Canyon, Colorado), and a chaparral mixed bedrock canyon environment (Mission Trails, San Diego, California). All three methods systematically failed for portions of the landscape in glacially carved canyons (Southern Wind River Range, Wyoming) and on terraced sea cliffs (Santa Cruz County, California). These environments have significant outcrop that is both smooth and low gradient, and therefore cannot be identified using a slope or roughness-based algorithm.
Our work highlights the importance of tailoring DEM-based bedrock mapping algorithms to its geomorphic context, and of the need for ground truth. Such data provides the basis for developing more robust methods for error evaluation. In addition, new methods are needed to identify bedrock outcrop from surface DEMs in smooth and low gradient, yet rocky landscapes.
How to cite: Selander, B., Anderson, S., and Rossi, M.: Evaluating bedrock outcrop mapping algorithms across diverse landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6620, https://doi.org/10.5194/egusphere-egu21-6620, 2021.
EGU21-7494 | vPICO presentations | GM2.7
Influence of the daylight illumination a weather conditions on Airborne Thermal Infrared Hyperspectral geological mappingStephane Boubanga Tombet, Jean-Philippe Gagnon, Holger Eichstaedt, and Joanne Ho
The use of airborne remote sensing techniques for geological mapping offers many benefits as it allows coverage of large areas in a very efficient way. While hyperspectral imaging from airborne/spaceborne platforms is now a well-established method applied to resolve many geological problems, it has mostly been developed only in the Visible-Near Infrared (VNIR, 0.4–1.0 mm) and Shortwave Infrared (SWIR, 1.0–2.5 mm) regions of the electromagnetic spectrum. However, the reflectance spectral features measured in the VNIR and SWIR spectral ranges are generally overtones and combination bands from fundamental absorption bands at longer wavelengths, such as in the Longwave Infrared (LWIR, 8–12 mm). The single absorption bands in the VNIR and SWIR spectral ranges are often very closely spaced so that the reflectance features measured by common spectrometers in this spectral region are typically broad and/or suffer from strong overlapping, which raises selectivity issues for mineral identification in some cases.
The inherent self-emission associated with LWIR under ambient conditions allows airborne mineral mapping in various weather (cloudy, partly cloudy or clear sky) and illumination (day or night) conditions. For this reason, LWIR often refers to the thermal infrared (TIR) spectral range. Solid targets such as minerals not only emit but also reflect TIR radiation. Since the two phenomena occur simultaneously, they end-up mixed in the radiance measured at the sensor level. The spectral features observed in a TIR spectrum of the sky and the atmosphere mostly correspond to ozone, water vapor, carbon dioxide, methane and nitrous oxide with pretty sharp and narrow features compared with the infrared signature of solid materials such as minerals. The sharp spectral features of atmospheric gases are mixed up with broad minerals features in the collected geological mapping data, to unveil the spectral features associated with minerals from TIR measurements, the respective contributions of self-emission and reflection in the measurement must be «unmixed» and the atmospheric contributions must be compensated. This procedure refers to temperature-emissivity separation (TES). Therefore, to achieve an efficient TES and atmospheric compensation, the collection time and conditions of LWIR airborne hyperspectral data is of importance. Data of a flight mission in Southern Spain collected systematically at different times of the day (morning, mid-day and night) and in different altitudes using the Telops Hyper-Cam airborne system, a passive TIR hyperspectral sensor based on Fourier transform spectroscopy, were analyzed. TES was carried out on the hyperspectral data using two different approaches: a) Telops Reveal FLAASH IR software and b) DIMAP In-scene atmospheric compensation algorithm in order to retrieve thermodynamic temperature map and spectral emissivity data. Spectral analysis of the emissivity data with different mineral mapping methods based on commercial spectral libraries was used to compare results obtained during the different flight times and altitudes using the two post-processing methodologies. The results are discussed in the light of optimizing LWIR-based airborne operations in time and altitude to achieve best results for routine field mineral mapping applications such as in mining, soil science or archaeology, where the spatial analysis of mineral and chemical distribution is essential
How to cite: Boubanga Tombet, S., Gagnon, J.-P., Eichstaedt, H., and Ho, J.: Influence of the daylight illumination a weather conditions on Airborne Thermal Infrared Hyperspectral geological mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7494, https://doi.org/10.5194/egusphere-egu21-7494, 2021.
The use of airborne remote sensing techniques for geological mapping offers many benefits as it allows coverage of large areas in a very efficient way. While hyperspectral imaging from airborne/spaceborne platforms is now a well-established method applied to resolve many geological problems, it has mostly been developed only in the Visible-Near Infrared (VNIR, 0.4–1.0 mm) and Shortwave Infrared (SWIR, 1.0–2.5 mm) regions of the electromagnetic spectrum. However, the reflectance spectral features measured in the VNIR and SWIR spectral ranges are generally overtones and combination bands from fundamental absorption bands at longer wavelengths, such as in the Longwave Infrared (LWIR, 8–12 mm). The single absorption bands in the VNIR and SWIR spectral ranges are often very closely spaced so that the reflectance features measured by common spectrometers in this spectral region are typically broad and/or suffer from strong overlapping, which raises selectivity issues for mineral identification in some cases.
The inherent self-emission associated with LWIR under ambient conditions allows airborne mineral mapping in various weather (cloudy, partly cloudy or clear sky) and illumination (day or night) conditions. For this reason, LWIR often refers to the thermal infrared (TIR) spectral range. Solid targets such as minerals not only emit but also reflect TIR radiation. Since the two phenomena occur simultaneously, they end-up mixed in the radiance measured at the sensor level. The spectral features observed in a TIR spectrum of the sky and the atmosphere mostly correspond to ozone, water vapor, carbon dioxide, methane and nitrous oxide with pretty sharp and narrow features compared with the infrared signature of solid materials such as minerals. The sharp spectral features of atmospheric gases are mixed up with broad minerals features in the collected geological mapping data, to unveil the spectral features associated with minerals from TIR measurements, the respective contributions of self-emission and reflection in the measurement must be «unmixed» and the atmospheric contributions must be compensated. This procedure refers to temperature-emissivity separation (TES). Therefore, to achieve an efficient TES and atmospheric compensation, the collection time and conditions of LWIR airborne hyperspectral data is of importance. Data of a flight mission in Southern Spain collected systematically at different times of the day (morning, mid-day and night) and in different altitudes using the Telops Hyper-Cam airborne system, a passive TIR hyperspectral sensor based on Fourier transform spectroscopy, were analyzed. TES was carried out on the hyperspectral data using two different approaches: a) Telops Reveal FLAASH IR software and b) DIMAP In-scene atmospheric compensation algorithm in order to retrieve thermodynamic temperature map and spectral emissivity data. Spectral analysis of the emissivity data with different mineral mapping methods based on commercial spectral libraries was used to compare results obtained during the different flight times and altitudes using the two post-processing methodologies. The results are discussed in the light of optimizing LWIR-based airborne operations in time and altitude to achieve best results for routine field mineral mapping applications such as in mining, soil science or archaeology, where the spatial analysis of mineral and chemical distribution is essential
How to cite: Boubanga Tombet, S., Gagnon, J.-P., Eichstaedt, H., and Ho, J.: Influence of the daylight illumination a weather conditions on Airborne Thermal Infrared Hyperspectral geological mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7494, https://doi.org/10.5194/egusphere-egu21-7494, 2021.
EGU21-7846 | vPICO presentations | GM2.7
Dealing with uncertainties in assessing geomorphic change. Spatially estimating structure-from-motion precisions using a block-resampling approach.Florian Strohmaier, Jason Goetz, and Sam McColl
Structure-from-Motion – Multi-View Stereo (SfM-MVS) has become a widely used approach in the study of Earth surface processes to reconstruct high-resolution topography (HRT) models. Starting in the early 2010s, it has become a cheap, flexible and user-friendly alternative to aerial/terrestrial laser scanning in geosciences and in change detection analyses in particular. In this context, previous work has dealt with the spatial distribution of error and with appropriately accounting for uncertainty estimates of such models in change detection results. However, error distribution and propagation are still not widely accounted for in standard analyses: Various sources of error result in complex distribution of model precision and accuracy. This poses challenges on study effort and complexity.
In this study, we developed a novel approach for obtaining spatially distributed estimates of precision for SfM-MVS derived digital elevation models (DEM). We applied block resampling to simulate repeatedly surveyed flights. This approach allows us to create multiple independently-resampled image sets that capture the general geometry of the original survey for SfM-MVS reconstruction. In a case study of observing erosion and deposition patterns of a highly active badass gully (Mangatu fluvio–mass movement gully complex, East Coast, NZ) we simulated 20 repeated flights (i.e. images sets) for images acquired from UAVs in 2018 and 2019. The subsequent precisions were used for deriving confidence intervals for sediment budgets. Overall, the precision estimates in open-terrain matched well with previous studies based on repeated surveys (~ <5cm). Weaker precisions were observed in areas of vegetation or where viewing angles could be obstructed by surrounding vegetation. The simulated DEMs, which were based on the mean value for each grid cell across the simulations, were in good agreement with the original reconstructed scene: differences were mainly less than 2 cm for most of the exposed erosion and deposition areas.
We estimated volumetric net change to be within [– 113.07;–101.48]×1000m³ with 95% confidence between April 2018 and April 2019. Gross sediment erosion was [–123.07;–111.73]×1000m³; gross deposition was [8.9;11.7]×1000m³ in the same time frame. This is well within findings of previous studies. However, compared to these, we could substantially improve the precision of uncertainty estimates. While computationally intensive, our method is able to reduce field work compared to similar studies. It additionally has the advantage of computing precisions that account for uncertainties in both SfM and MVS reconstruction algorithms. This means that SfM-MVS precisions can be computed on past surveys given the images were taken with sufficient overlap, as we demonstrated in our case study.
How to cite: Strohmaier, F., Goetz, J., and McColl, S.: Dealing with uncertainties in assessing geomorphic change. Spatially estimating structure-from-motion precisions using a block-resampling approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7846, https://doi.org/10.5194/egusphere-egu21-7846, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Structure-from-Motion – Multi-View Stereo (SfM-MVS) has become a widely used approach in the study of Earth surface processes to reconstruct high-resolution topography (HRT) models. Starting in the early 2010s, it has become a cheap, flexible and user-friendly alternative to aerial/terrestrial laser scanning in geosciences and in change detection analyses in particular. In this context, previous work has dealt with the spatial distribution of error and with appropriately accounting for uncertainty estimates of such models in change detection results. However, error distribution and propagation are still not widely accounted for in standard analyses: Various sources of error result in complex distribution of model precision and accuracy. This poses challenges on study effort and complexity.
In this study, we developed a novel approach for obtaining spatially distributed estimates of precision for SfM-MVS derived digital elevation models (DEM). We applied block resampling to simulate repeatedly surveyed flights. This approach allows us to create multiple independently-resampled image sets that capture the general geometry of the original survey for SfM-MVS reconstruction. In a case study of observing erosion and deposition patterns of a highly active badass gully (Mangatu fluvio–mass movement gully complex, East Coast, NZ) we simulated 20 repeated flights (i.e. images sets) for images acquired from UAVs in 2018 and 2019. The subsequent precisions were used for deriving confidence intervals for sediment budgets. Overall, the precision estimates in open-terrain matched well with previous studies based on repeated surveys (~ <5cm). Weaker precisions were observed in areas of vegetation or where viewing angles could be obstructed by surrounding vegetation. The simulated DEMs, which were based on the mean value for each grid cell across the simulations, were in good agreement with the original reconstructed scene: differences were mainly less than 2 cm for most of the exposed erosion and deposition areas.
We estimated volumetric net change to be within [– 113.07;–101.48]×1000m³ with 95% confidence between April 2018 and April 2019. Gross sediment erosion was [–123.07;–111.73]×1000m³; gross deposition was [8.9;11.7]×1000m³ in the same time frame. This is well within findings of previous studies. However, compared to these, we could substantially improve the precision of uncertainty estimates. While computationally intensive, our method is able to reduce field work compared to similar studies. It additionally has the advantage of computing precisions that account for uncertainties in both SfM and MVS reconstruction algorithms. This means that SfM-MVS precisions can be computed on past surveys given the images were taken with sufficient overlap, as we demonstrated in our case study.
How to cite: Strohmaier, F., Goetz, J., and McColl, S.: Dealing with uncertainties in assessing geomorphic change. Spatially estimating structure-from-motion precisions using a block-resampling approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7846, https://doi.org/10.5194/egusphere-egu21-7846, 2021.
EGU21-8228 | vPICO presentations | GM2.7
Sentinel-1 application to rainfall response and geomorphic mappingStephanie Olen and Bodo Bookhagen
Rainfall is one of the primary geomorphic drivers on Earth’s surface. How a surface responds to rainfall directly impacts erosional, geomorphic, and natural hazard processes. In the absence of vegetation, whether a land surface retains rainfall as soil moisture or whether rainfall is quickly infiltrated or run off is largely a function of geomorphologic and geologic conditions. In this study, we combine a time series of synthetic aperture radar (SAR) backscatter with daily precipitation to analyze the response of arid and semi-arid land surfaces to rainfall from the event to seasonal scale. The study focuses on northwestern Argentina, where we have extensive field knowledge of local geomorphic features, and is implemented using the cloud computing capacities of Google Earth Engine (GEE).
Th Sentinel-1 satellites provide high spatial (10 m) and temporal resolution images of Earth’s surface, irrespective of cloud cover. We created a 3 year time series from 2018 through 2020 of Sentinel-1 sigma-naught (σ0) backscatter from Ground Range Detected (GRD) products available on GEE. Combining the ascending and descending orbits of the Sentinel-1A and -1B satellites into a single time series provides 3 to 6 day temporal resolution in our area of interest. The Global Precipitation Measurement Mission (GPM) was aggregated to daily and monthly precipitation measurements to identify single rainfall events and the seasonal rainfall signal.
The response and recovery of SAR backscatter to individual rainfall events across different land surfaces was calculated over 4 to 6 week periods centered on and following a specific rainfall date, respectively. The temporal trend of the backscatter data in these time windows is calculated for every pixel in the backscatter stack to create a map how the surface responds to a large rainfall event. The location of standing water, increased soil moisture, and high infiltration surfaces are detectable in the response maps. The recovery maps provide a proxy for the rate of drying following the rainfall event.
In the monsoon-dominated region of northwestern Argentina, both precipitation and SAR backscatter show a clear, periodic seasonal signal over our three-year time series. By aggregating all data to monthly resolution, we can calculate pixel-wise linear regressions and correlation coefficients between precipitation and SAR backscatter. Regressions and correlation analysis are done at the resolution of the Sentinel-1 data and are used to identify whether a surface retains soil moisture, has high infiltration, or experiences seasonal standing water or snow cover. Areas dominated by highly weathered granites and sandstones that can retain soil moisture, for example, have strong positive correlation between rainfall and backscatter due to the increased dielectric constant of wet sediment. In contrast, gravel terraces where rainfall can easily infiltrate the surface show little correlation between backscatter and precipitation. The result is a high resolution map characterizing the propensity for soil moisture retention, high infiltration, and standing water and snow cover. Future work will focus on using these relationships to classify geomorphic surfaces across the arid and semi-arid central Andes.
How to cite: Olen, S. and Bookhagen, B.: Sentinel-1 application to rainfall response and geomorphic mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8228, https://doi.org/10.5194/egusphere-egu21-8228, 2021.
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Rainfall is one of the primary geomorphic drivers on Earth’s surface. How a surface responds to rainfall directly impacts erosional, geomorphic, and natural hazard processes. In the absence of vegetation, whether a land surface retains rainfall as soil moisture or whether rainfall is quickly infiltrated or run off is largely a function of geomorphologic and geologic conditions. In this study, we combine a time series of synthetic aperture radar (SAR) backscatter with daily precipitation to analyze the response of arid and semi-arid land surfaces to rainfall from the event to seasonal scale. The study focuses on northwestern Argentina, where we have extensive field knowledge of local geomorphic features, and is implemented using the cloud computing capacities of Google Earth Engine (GEE).
Th Sentinel-1 satellites provide high spatial (10 m) and temporal resolution images of Earth’s surface, irrespective of cloud cover. We created a 3 year time series from 2018 through 2020 of Sentinel-1 sigma-naught (σ0) backscatter from Ground Range Detected (GRD) products available on GEE. Combining the ascending and descending orbits of the Sentinel-1A and -1B satellites into a single time series provides 3 to 6 day temporal resolution in our area of interest. The Global Precipitation Measurement Mission (GPM) was aggregated to daily and monthly precipitation measurements to identify single rainfall events and the seasonal rainfall signal.
The response and recovery of SAR backscatter to individual rainfall events across different land surfaces was calculated over 4 to 6 week periods centered on and following a specific rainfall date, respectively. The temporal trend of the backscatter data in these time windows is calculated for every pixel in the backscatter stack to create a map how the surface responds to a large rainfall event. The location of standing water, increased soil moisture, and high infiltration surfaces are detectable in the response maps. The recovery maps provide a proxy for the rate of drying following the rainfall event.
In the monsoon-dominated region of northwestern Argentina, both precipitation and SAR backscatter show a clear, periodic seasonal signal over our three-year time series. By aggregating all data to monthly resolution, we can calculate pixel-wise linear regressions and correlation coefficients between precipitation and SAR backscatter. Regressions and correlation analysis are done at the resolution of the Sentinel-1 data and are used to identify whether a surface retains soil moisture, has high infiltration, or experiences seasonal standing water or snow cover. Areas dominated by highly weathered granites and sandstones that can retain soil moisture, for example, have strong positive correlation between rainfall and backscatter due to the increased dielectric constant of wet sediment. In contrast, gravel terraces where rainfall can easily infiltrate the surface show little correlation between backscatter and precipitation. The result is a high resolution map characterizing the propensity for soil moisture retention, high infiltration, and standing water and snow cover. Future work will focus on using these relationships to classify geomorphic surfaces across the arid and semi-arid central Andes.
How to cite: Olen, S. and Bookhagen, B.: Sentinel-1 application to rainfall response and geomorphic mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8228, https://doi.org/10.5194/egusphere-egu21-8228, 2021.
EGU21-10837 | vPICO presentations | GM2.7
Integrated reflection seismics, 3D-GPR, leveling, DInSAR to detect and characterize high-risk sinkholes in urban cover evaporite karst. A NE Italian case study.Alice Busetti, Chiara Calligaris, Emanuele Forte, Giulia Areggi, Arianna Mocnik, and Luca Zini
Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in terms of clear identification and mapping considering the anthropic rehash and the presence of man-made structures.
We propose and tested a methodology to identify the subsiding features in an urban area within a cover evaporite karst environment, through an integrated and non-invasive multi-scale approach combining seismic reflection, DInSAR, leveling and full 3D GPR.
The analysis was conducted in a small village in the Tagliamento valley (Friuli Venezia Giulia region, NE Italy) named Quinis, where sinkholes are reported since a long time as well as the hazard linked to their presence: within the years, several houses have been demolished and at present many of them are damaged.
First we applied each methodology independently and after we compared, combined and integrated them to obtain more coherent and cross-validates results. Seismic reflection imagined the covered karst bedrock identifying three depocenters; DInSAR investigation allowed to identify an area with higher vertical velocities; leveling data presented a downward displacement comparable with DInSAR results; 3D GPR, applied here for the first time in the study and characterization of sinkholes, clearly defined shallow sinking features imaging also under a shallow dense pipe network. Combining all the obtained results with accurate field observations we identified and map the highest vulnerable zones.
The final result is the combining of the geophysical, DInSAR and leveling information, while also locating the damaged buildings, the local asphalt pavement breaks or renovation and the buildings which are nowadays demolished, by using vintage photographs and historical maps. The data are consistent, being the most relevant present damages and the demolished building within the zones with higher sinking velocity on the base of both leveling and DInSAR. Geophysically imaged depocenters lie within the most critical area and perfectly correlate with the local pavement damages.
In a complex geological and hydrological framework, as in the study area, a multidisciplinary and multi-scale approach is mandatory to identify and map the zone most affected by sinking phenomena. While punctual data such as borehole stratigraphy, local groundwater level variations with time, extensometers measurements and geotechnical parameters are useful to highlight local hazard due to occurring deformation, the proposed integrated methodology addresses a complete and quantitative assessment of the vulnerability of the area. It’s fundamental, especially in anthropized environments, using different integrated techniques, without forgetting the role of the fieldwork of the geologists who can detect the precursors or already occurred, even elusive, signs of the ongoing or incipient sinking.
How to cite: Busetti, A., Calligaris, C., Forte, E., Areggi, G., Mocnik, A., and Zini, L.: Integrated reflection seismics, 3D-GPR, leveling, DInSAR to detect and characterize high-risk sinkholes in urban cover evaporite karst. A NE Italian case study., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10837, https://doi.org/10.5194/egusphere-egu21-10837, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in terms of clear identification and mapping considering the anthropic rehash and the presence of man-made structures.
We propose and tested a methodology to identify the subsiding features in an urban area within a cover evaporite karst environment, through an integrated and non-invasive multi-scale approach combining seismic reflection, DInSAR, leveling and full 3D GPR.
The analysis was conducted in a small village in the Tagliamento valley (Friuli Venezia Giulia region, NE Italy) named Quinis, where sinkholes are reported since a long time as well as the hazard linked to their presence: within the years, several houses have been demolished and at present many of them are damaged.
First we applied each methodology independently and after we compared, combined and integrated them to obtain more coherent and cross-validates results. Seismic reflection imagined the covered karst bedrock identifying three depocenters; DInSAR investigation allowed to identify an area with higher vertical velocities; leveling data presented a downward displacement comparable with DInSAR results; 3D GPR, applied here for the first time in the study and characterization of sinkholes, clearly defined shallow sinking features imaging also under a shallow dense pipe network. Combining all the obtained results with accurate field observations we identified and map the highest vulnerable zones.
The final result is the combining of the geophysical, DInSAR and leveling information, while also locating the damaged buildings, the local asphalt pavement breaks or renovation and the buildings which are nowadays demolished, by using vintage photographs and historical maps. The data are consistent, being the most relevant present damages and the demolished building within the zones with higher sinking velocity on the base of both leveling and DInSAR. Geophysically imaged depocenters lie within the most critical area and perfectly correlate with the local pavement damages.
In a complex geological and hydrological framework, as in the study area, a multidisciplinary and multi-scale approach is mandatory to identify and map the zone most affected by sinking phenomena. While punctual data such as borehole stratigraphy, local groundwater level variations with time, extensometers measurements and geotechnical parameters are useful to highlight local hazard due to occurring deformation, the proposed integrated methodology addresses a complete and quantitative assessment of the vulnerability of the area. It’s fundamental, especially in anthropized environments, using different integrated techniques, without forgetting the role of the fieldwork of the geologists who can detect the precursors or already occurred, even elusive, signs of the ongoing or incipient sinking.
How to cite: Busetti, A., Calligaris, C., Forte, E., Areggi, G., Mocnik, A., and Zini, L.: Integrated reflection seismics, 3D-GPR, leveling, DInSAR to detect and characterize high-risk sinkholes in urban cover evaporite karst. A NE Italian case study., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10837, https://doi.org/10.5194/egusphere-egu21-10837, 2021.
EGU21-9898 | vPICO presentations | GM2.7
Value added? Comparative estimates of peat basin volumetrics using borehole methods and 3D ground-penetrating radarLuis Rees-Hughes, Natasha Barlow, Adam Booth, Jared West, Tim Grossey, and George Tuckwell
Peatlands have long been recognized as providing a wide range of ecosystem services valuable to humans. In recent decades their role in the global climate and particularly their importance in long-term carbon sequestration has come into focus. Peatlands and peat basins are an important carbon store globally, and are estimated to cover nearly 25% of the Scottish landscape: they constitute a significant carbon stock, but being able to accurately estimate the volume of peat stored in coastal basins, both locally and regionally, remains a time-consuming process. Traditional methods of investigating peat depth and volume involved the measurement of peat to depth of contact with a mineral horizon, such as sand. This process is conducted with a peat depth probe or corer, with the spatial density of measurements varying significantly with basin size. Volumetric assessments based on such measurements therefore require interpolation between control points, leading to unquantifiable errors particularly if the base of peat has significant and unrecorded topography. Geophysical methods, in particular the 3D application of ground-penetrating (GPR), offer a promising solution to improve the accuracy in basin volumetrics.
In this paper, a 3D dataset of 100 MHz GPR data was acquired with a Mala Geosciences Rough Terrain system over a buried Holocene coastal environment near Arisaig, northwest Scotland. 3D surveying involves the acquisition of a suite of parallel GPR profiles, with a small profile separation to capture the full variability of subsurface structure. For this site, a profile was acquired every 0.5 m, over an area of 62 x 32 m. The site is also sampled by 39 boreholes, which record the base of peat between 1-3.2 m depth and indicate a peat volume of 3720 m3. By revealing the true topography of the base of the basin, the GPR data suggest that the borehole-derived volume is overestimated by almost 50%, and instead predict a basin volume of 2529 ± 200 m3. Of this, 2064 ± 200 m3 is classified as organic peat (81.6%) and the remaining 465 ± 200 m3 is marine clay (18.4%). The principal source of error in this estimate is in the constraint of the GPR velocity, required to convert the time-axis of the GPR dataset to depth. This was measured at 0.034 m/ns ± 8%.
The acquisition of 3D GPR data is nonetheless time-consuming and requires precise positional control to locate the GPR antennas and avoid misinterpretation. Nonetheless, sufficient topographic information is captured even if the acquisition had recorded only every 5th GPR profile: for this downsampled dataset, the estimated basin volume is 2490 m3 ± 200 m3 (a difference of only 2.5% from the full 3D dataset). 3D survey methods, therefore, give confidence to a volumetric estimate, but the need for full-resolution 3D sampling can likely be relaxed. However, GPR surveys reveal subsurface variability that would be difficult to reconstruct from a sparse set of borehole observations. Nonetheless, some amount of borehole control is invaluable for validating the GPR data and providing ground-truth control of subsurface structure.
How to cite: Rees-Hughes, L., Barlow, N., Booth, A., West, J., Grossey, T., and Tuckwell, G.: Value added? Comparative estimates of peat basin volumetrics using borehole methods and 3D ground-penetrating radar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9898, https://doi.org/10.5194/egusphere-egu21-9898, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Peatlands have long been recognized as providing a wide range of ecosystem services valuable to humans. In recent decades their role in the global climate and particularly their importance in long-term carbon sequestration has come into focus. Peatlands and peat basins are an important carbon store globally, and are estimated to cover nearly 25% of the Scottish landscape: they constitute a significant carbon stock, but being able to accurately estimate the volume of peat stored in coastal basins, both locally and regionally, remains a time-consuming process. Traditional methods of investigating peat depth and volume involved the measurement of peat to depth of contact with a mineral horizon, such as sand. This process is conducted with a peat depth probe or corer, with the spatial density of measurements varying significantly with basin size. Volumetric assessments based on such measurements therefore require interpolation between control points, leading to unquantifiable errors particularly if the base of peat has significant and unrecorded topography. Geophysical methods, in particular the 3D application of ground-penetrating (GPR), offer a promising solution to improve the accuracy in basin volumetrics.
In this paper, a 3D dataset of 100 MHz GPR data was acquired with a Mala Geosciences Rough Terrain system over a buried Holocene coastal environment near Arisaig, northwest Scotland. 3D surveying involves the acquisition of a suite of parallel GPR profiles, with a small profile separation to capture the full variability of subsurface structure. For this site, a profile was acquired every 0.5 m, over an area of 62 x 32 m. The site is also sampled by 39 boreholes, which record the base of peat between 1-3.2 m depth and indicate a peat volume of 3720 m3. By revealing the true topography of the base of the basin, the GPR data suggest that the borehole-derived volume is overestimated by almost 50%, and instead predict a basin volume of 2529 ± 200 m3. Of this, 2064 ± 200 m3 is classified as organic peat (81.6%) and the remaining 465 ± 200 m3 is marine clay (18.4%). The principal source of error in this estimate is in the constraint of the GPR velocity, required to convert the time-axis of the GPR dataset to depth. This was measured at 0.034 m/ns ± 8%.
The acquisition of 3D GPR data is nonetheless time-consuming and requires precise positional control to locate the GPR antennas and avoid misinterpretation. Nonetheless, sufficient topographic information is captured even if the acquisition had recorded only every 5th GPR profile: for this downsampled dataset, the estimated basin volume is 2490 m3 ± 200 m3 (a difference of only 2.5% from the full 3D dataset). 3D survey methods, therefore, give confidence to a volumetric estimate, but the need for full-resolution 3D sampling can likely be relaxed. However, GPR surveys reveal subsurface variability that would be difficult to reconstruct from a sparse set of borehole observations. Nonetheless, some amount of borehole control is invaluable for validating the GPR data and providing ground-truth control of subsurface structure.
How to cite: Rees-Hughes, L., Barlow, N., Booth, A., West, J., Grossey, T., and Tuckwell, G.: Value added? Comparative estimates of peat basin volumetrics using borehole methods and 3D ground-penetrating radar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9898, https://doi.org/10.5194/egusphere-egu21-9898, 2021.
EGU21-1755 | vPICO presentations | GM2.7
Distribution of monogenetic volcanism along the Cameroon LineChristoph Schmidt, Christian Laag, and Jörn Profe
Volcanic eruptions may constitute a severe threat for local communities and their infrastructure. Important information as to the prediction of future eruption sites and the likelihood of activity can be obtained by analysis of spatio-temporal eruption pattern in an area of interest. The fact that monogenetic volcanoes, unlike polygenetic ones, erupt only once (within a geologically short period) at a certain spot and then volcanic activity jumps to another spot, renders a quantitative, probabilistic assessment of eruptive cycles challenging. In other words, the purely temporal risk assessment relevant for polygenetic volcanism has to be supplemented by a spatial dimension in case of monogenetic volcanic fields to allow for a combined spatio-temporal forecast.
While the eruption history of many stratovolcanoes along the Cameroon Line (CL) in Central Africa is comparatively well studied, only fragmentary data exists on the distribution and timing of monogenetic volcanism (mainly scoria cones and maars), presumably associated with Quaternary timescales. Here, we undertake an initial step in closing this gap and present for the first time a map of monogenetic volcanic features for most parts of the CL. Scoria cones and maars were identified by their characteristic morphologies using a combination of field knowledge, digital elevation models and satellite imagery. More than ~1300 scoria cones and 41 maars were detected and divided into eight monogenetic volcanic fields (MVF), as defined by the convex hull of the outermost vents: Bioko, Mt. Cameroon, Kumba, Tombel Graben (including Mt. Manengouba), Noun, Oku, Adamawa, and Biu (Nigeria). However, due to the rugged topography in the Oku volcanic field and the difficulty of identifying volcanic features remotely, the number of mapped scoria cones appears rather incomplete.
While the delineation of individual MVF bears an inherent subjective moment, statistical analyses of the primary dataset clearly shows that the mean nearest neighbour distance increases from <1 km to ~2 km from the oceanic sector (Bioko, Mt. Cameroon) in the southwest towards the continental part in the northeast (Adamawa, Biu). Correspondingly, the areal density of monogenetic features decreases along this gradient by about one order of magnitude from >0.2 km-2 (southwest) to 0.02 km-2 (northeast). This finding is in general agreement with prior geochronological results, indicating increased Quaternary activity towards the central and oceanic part of the CL (e.g., Njome and de Wit, 2014). Tests for the spatial organization of monogenetic volcanoes using the Geological Image Analysis Software (GIAS, v2; Beggan and Hamilton, 2010) revealed that the vents in all MVF are clustered (98% credible interval), thus allowing inferences to be drawn on the tectonic control of (future) eruption locations.
References
Beggan, C., Hamilton, C.W., 2010. New image processing software for analyzing object size-frequency distributions, geometry, orientation, and spatial distribution. Computers & Geosciences 36, 539-549.
Njome, M.S., de Wit, M.J., 2014. The Cameroon Line: Analysis of an intraplate magmatic province transecting both oceanic and continental lithospheres: Constraints, controversies and models. Earth-Science Reviews 139, 168-194.
How to cite: Schmidt, C., Laag, C., and Profe, J.: Distribution of monogenetic volcanism along the Cameroon Line, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1755, https://doi.org/10.5194/egusphere-egu21-1755, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Volcanic eruptions may constitute a severe threat for local communities and their infrastructure. Important information as to the prediction of future eruption sites and the likelihood of activity can be obtained by analysis of spatio-temporal eruption pattern in an area of interest. The fact that monogenetic volcanoes, unlike polygenetic ones, erupt only once (within a geologically short period) at a certain spot and then volcanic activity jumps to another spot, renders a quantitative, probabilistic assessment of eruptive cycles challenging. In other words, the purely temporal risk assessment relevant for polygenetic volcanism has to be supplemented by a spatial dimension in case of monogenetic volcanic fields to allow for a combined spatio-temporal forecast.
While the eruption history of many stratovolcanoes along the Cameroon Line (CL) in Central Africa is comparatively well studied, only fragmentary data exists on the distribution and timing of monogenetic volcanism (mainly scoria cones and maars), presumably associated with Quaternary timescales. Here, we undertake an initial step in closing this gap and present for the first time a map of monogenetic volcanic features for most parts of the CL. Scoria cones and maars were identified by their characteristic morphologies using a combination of field knowledge, digital elevation models and satellite imagery. More than ~1300 scoria cones and 41 maars were detected and divided into eight monogenetic volcanic fields (MVF), as defined by the convex hull of the outermost vents: Bioko, Mt. Cameroon, Kumba, Tombel Graben (including Mt. Manengouba), Noun, Oku, Adamawa, and Biu (Nigeria). However, due to the rugged topography in the Oku volcanic field and the difficulty of identifying volcanic features remotely, the number of mapped scoria cones appears rather incomplete.
While the delineation of individual MVF bears an inherent subjective moment, statistical analyses of the primary dataset clearly shows that the mean nearest neighbour distance increases from <1 km to ~2 km from the oceanic sector (Bioko, Mt. Cameroon) in the southwest towards the continental part in the northeast (Adamawa, Biu). Correspondingly, the areal density of monogenetic features decreases along this gradient by about one order of magnitude from >0.2 km-2 (southwest) to 0.02 km-2 (northeast). This finding is in general agreement with prior geochronological results, indicating increased Quaternary activity towards the central and oceanic part of the CL (e.g., Njome and de Wit, 2014). Tests for the spatial organization of monogenetic volcanoes using the Geological Image Analysis Software (GIAS, v2; Beggan and Hamilton, 2010) revealed that the vents in all MVF are clustered (98% credible interval), thus allowing inferences to be drawn on the tectonic control of (future) eruption locations.
References
Beggan, C., Hamilton, C.W., 2010. New image processing software for analyzing object size-frequency distributions, geometry, orientation, and spatial distribution. Computers & Geosciences 36, 539-549.
Njome, M.S., de Wit, M.J., 2014. The Cameroon Line: Analysis of an intraplate magmatic province transecting both oceanic and continental lithospheres: Constraints, controversies and models. Earth-Science Reviews 139, 168-194.
How to cite: Schmidt, C., Laag, C., and Profe, J.: Distribution of monogenetic volcanism along the Cameroon Line, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1755, https://doi.org/10.5194/egusphere-egu21-1755, 2021.
EGU21-8763 | vPICO presentations | GM2.7
Reconstructing the initial shape of volcanic islands to quantify long-term coastal erosionRémi Bossis, Vincent Regard, and Sébastien Carretier
The global solid flux from continent to ocean is usually reduced to the input of sediments from rivers, and is estimated at approximately 20 Gt/year. Another input of sediments to ocean is coastal erosion, but this flux is difficult to estimate on a global scale and it is often neglected, perhaps wrongly according to regional studies [1,2]. Most studies attempting to quantify coastal erosion have focused on the coasts of developed countries and are limited to the timescale of decades or less [3]. The difficulty in quantifying long-term coastal erosion is that there are still many uncertainties about the factors controlling coastal erosion on this time scale, and it would be necessary to know the initial geometry of coastlines to calculate an eroded volume.
Volcanic islands, as geomorphological objects, seem to be very good objects of study to remedy these limitations. Indeed, many young volcanic islands are made of only one central edifice with a strong radial symmetry despite its degradation by erosion [4,5]. By knowing the age of an island and by comparing reconstructed shape with current shape, we can calculate a total eroded volume and an integrated average coastal erosion rate on the age of the island. Moreover, due to their geographical, petrological and tectonic diversity, volcanic islands allow to compare the influence of different factors on long-term coastal erosion, such as climate, wave direction and height, rock resistance or vertical movements. Thus, we will be able to prioritize them to propose coastal erosion laws that would applicable to all rocky coasts.
Here we built on previous works that have used aerial geospatial databases to reconstruct the initial shape of these islands [6,7] but we improve this approach by using offshore topographic data to determine the maximum and initial extension of their coasts. From both onshore and offshore topographies, we determine a long-term mean coastal erosion rate and we quantify precisely its uncertainty. Using the example of Corvo Island, in the Azores archipelago, we show how our approach allows us to obtain first estimates of long-term coastal erosion rate around this island.
References
[1] Landemaine V. (2016). Ph.D. thesis, University of Rouen.
[2] Rachold V., Grigoriev M.N., Are F.E., Solomon S., Reimnitz E., Kassens H., Antonow M. (2000). International Journal of Earth Sciences, 89(3), 450-460.
[3] Prémaillon M. (2018). Ph.D. thesis, University of Toulouse.
[4] Karátson D., Favalli M., Tarquini S., Fornaciai A., Wörner G. (2010). Journal of Volcanology and Geothermal Research, 193, 171-181.
[5] Favalli M., Karátson D., Yepes J., NannipierI L. (2014). Geomorphology, 221, 139-149.
[6] Lahitte P., Samper A., Quidelleur X. (2012). Geomorphology, 136, 148-164.
[7] Karátson D., Yepes J., Favalli M., Rodríguez-Peces M.J., Fornaciai A. (2016). Geomorphology, 253, 123-134.
How to cite: Bossis, R., Regard, V., and Carretier, S.: Reconstructing the initial shape of volcanic islands to quantify long-term coastal erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8763, https://doi.org/10.5194/egusphere-egu21-8763, 2021.
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The global solid flux from continent to ocean is usually reduced to the input of sediments from rivers, and is estimated at approximately 20 Gt/year. Another input of sediments to ocean is coastal erosion, but this flux is difficult to estimate on a global scale and it is often neglected, perhaps wrongly according to regional studies [1,2]. Most studies attempting to quantify coastal erosion have focused on the coasts of developed countries and are limited to the timescale of decades or less [3]. The difficulty in quantifying long-term coastal erosion is that there are still many uncertainties about the factors controlling coastal erosion on this time scale, and it would be necessary to know the initial geometry of coastlines to calculate an eroded volume.
Volcanic islands, as geomorphological objects, seem to be very good objects of study to remedy these limitations. Indeed, many young volcanic islands are made of only one central edifice with a strong radial symmetry despite its degradation by erosion [4,5]. By knowing the age of an island and by comparing reconstructed shape with current shape, we can calculate a total eroded volume and an integrated average coastal erosion rate on the age of the island. Moreover, due to their geographical, petrological and tectonic diversity, volcanic islands allow to compare the influence of different factors on long-term coastal erosion, such as climate, wave direction and height, rock resistance or vertical movements. Thus, we will be able to prioritize them to propose coastal erosion laws that would applicable to all rocky coasts.
Here we built on previous works that have used aerial geospatial databases to reconstruct the initial shape of these islands [6,7] but we improve this approach by using offshore topographic data to determine the maximum and initial extension of their coasts. From both onshore and offshore topographies, we determine a long-term mean coastal erosion rate and we quantify precisely its uncertainty. Using the example of Corvo Island, in the Azores archipelago, we show how our approach allows us to obtain first estimates of long-term coastal erosion rate around this island.
References
[1] Landemaine V. (2016). Ph.D. thesis, University of Rouen.
[2] Rachold V., Grigoriev M.N., Are F.E., Solomon S., Reimnitz E., Kassens H., Antonow M. (2000). International Journal of Earth Sciences, 89(3), 450-460.
[3] Prémaillon M. (2018). Ph.D. thesis, University of Toulouse.
[4] Karátson D., Favalli M., Tarquini S., Fornaciai A., Wörner G. (2010). Journal of Volcanology and Geothermal Research, 193, 171-181.
[5] Favalli M., Karátson D., Yepes J., NannipierI L. (2014). Geomorphology, 221, 139-149.
[6] Lahitte P., Samper A., Quidelleur X. (2012). Geomorphology, 136, 148-164.
[7] Karátson D., Yepes J., Favalli M., Rodríguez-Peces M.J., Fornaciai A. (2016). Geomorphology, 253, 123-134.
How to cite: Bossis, R., Regard, V., and Carretier, S.: Reconstructing the initial shape of volcanic islands to quantify long-term coastal erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8763, https://doi.org/10.5194/egusphere-egu21-8763, 2021.
EGU21-2342 | vPICO presentations | GM2.7
Examining the suitability of the geomorphic parameters in generating the Relative Index of Active Tectonics: an example from Himalayan Frontal Thrust, IndiaAashna Tandon and Siddharth Prizomwala
This work emphasizes the efficient use of geomorphic parameters to form a unified index ~ Relative Index of Active Tectonics (RIAT), which has seldom been tested in areas with broader variability in the rate of deformation. This study aims to verify whether the geomorphic parameters can be used efficiently for RIAT to assess the spatial variability in deformation along the fault. The Himalayan Frontal Thrust has been chosen for morphotectonic evaluation owing to its active interplate thrust fault setting. For this purpose, we select vertical uplift sensitive geomorphic parameters viz., Mountain front sinuosity (Smf), Valley floor width-height ratio (Vf), and Steepness index (Ksn), as a primary tool to test the RIAT.
The result of RIAT shows the along-strike variation in response to the varying degree of deformation along the HFT. This is in fine agreement with the available long-term uplift/shortening rates and geodetic rates. Overall examination reveals RIAT being an excellent tool to assess the spatial variability in uplift rates in large tectonically active regions. However, the detailed scrutiny of individual geomorphic parameters reveals that only Vf, and the Ksn index are more responsive and go hand-in-hand with the RIAT variation. Whereas, Smf shows no spatial variation and function as least sensitive to such an investigation. The sensitivity of these individual parameters has implications for studies with similar settings elsewhere when quantitative rates are absent.
How to cite: Tandon, A. and Prizomwala, S.: Examining the suitability of the geomorphic parameters in generating the Relative Index of Active Tectonics: an example from Himalayan Frontal Thrust, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2342, https://doi.org/10.5194/egusphere-egu21-2342, 2021.
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This work emphasizes the efficient use of geomorphic parameters to form a unified index ~ Relative Index of Active Tectonics (RIAT), which has seldom been tested in areas with broader variability in the rate of deformation. This study aims to verify whether the geomorphic parameters can be used efficiently for RIAT to assess the spatial variability in deformation along the fault. The Himalayan Frontal Thrust has been chosen for morphotectonic evaluation owing to its active interplate thrust fault setting. For this purpose, we select vertical uplift sensitive geomorphic parameters viz., Mountain front sinuosity (Smf), Valley floor width-height ratio (Vf), and Steepness index (Ksn), as a primary tool to test the RIAT.
The result of RIAT shows the along-strike variation in response to the varying degree of deformation along the HFT. This is in fine agreement with the available long-term uplift/shortening rates and geodetic rates. Overall examination reveals RIAT being an excellent tool to assess the spatial variability in uplift rates in large tectonically active regions. However, the detailed scrutiny of individual geomorphic parameters reveals that only Vf, and the Ksn index are more responsive and go hand-in-hand with the RIAT variation. Whereas, Smf shows no spatial variation and function as least sensitive to such an investigation. The sensitivity of these individual parameters has implications for studies with similar settings elsewhere when quantitative rates are absent.
How to cite: Tandon, A. and Prizomwala, S.: Examining the suitability of the geomorphic parameters in generating the Relative Index of Active Tectonics: an example from Himalayan Frontal Thrust, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2342, https://doi.org/10.5194/egusphere-egu21-2342, 2021.
EGU21-15843 | vPICO presentations | GM2.7
Morphotectonic assessment in the Tokaj Mountain region (Hungary)Seif Ammar and Gáspár Albert
The Tokaj Mountain is a part of the large Carpathian Volcanic Arc which was active in the Middle-Upper Miocene in this area. It is built up of mainly andesitic and dacitic volcanic-sedimentary sequence which filled up the 1.5-3 km deep tectonic basin between two strike-slip faults: the Hernád Fault (W) and the Bodrog Fault (SE). Though the most tectonically active phase was during the Miocene, minor recent tectonism is observed in the area in the form of rare 2 to 3 M earthquakes. Due to its relatively low activity, the complexity and the thickness of the volcano-sediments, the tectonism and its effect on the recent shape of the mountain was not accurately mapped.
The present study aims to reveal the possible connections between the morphology and the present day stress field of the area. In this regard, several stress field model has been generated with the web based application “Geonuleus” accompanied with morphotectonic statistical analyses of the DEM from the region.
The method is based on the categorization of neotectonic lineaments (faults) by their geodynamic properties using the TPO method (Type-Property-Orientation) naming system for eventually generate the active stress field that reigns the region (Albert et al. 2016). The ALOS Palsar DEM (12.5 m resolution) has been used for the morphotectonic study. During the process, multiple filter have been utilized to eliminate the noise and to highlight lineaments (e.g. directional perpendicular filters). A statistical analysis was done from the lineaments orientation in order to define the general trend and to compare it with the main neotectonic directions and the stress field that have produced them.
The study area concentrated on the western part of the mountain since the detailed geophysical data is available only from that area (Bodor, 2011). The area was subdivided into three region based on the difference of the lithology, the tectonic regime and the topography (northern area, the western side of the Hernád stream and the eastern side of the Hernád stream). The result of the modeling shows a confluence between the two methods (SFM and the morphometry) especially in the western part with a regional N-S stress orientation. In the eastern side the flexure is clearly highlighted by stress trend movement. It is important to report that the model could be enhanced with further detailed data.
From the part of G.A. financial support was provided from the NRDI Fund of Hungary, Thematic Excellence Programme no. TKP2020-NKA-06 (National Challenges Subprogramme) funding scheme.
References:
Albert, G., Barancsuk, Á., & Szentpéteri, K. 2016. Stress field modelling from digital geological map data. Geophysical Research Abstracts, v. 18, EGU2016-14565.
Bodor B. 2011: A Hernád-árok szerkezetföldtani vizsgálata. MSc thesis, Eötvös University, Dept. Regional Geology, 99 p
How to cite: Ammar, S. and Albert, G.: Morphotectonic assessment in the Tokaj Mountain region (Hungary), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15843, https://doi.org/10.5194/egusphere-egu21-15843, 2021.
The Tokaj Mountain is a part of the large Carpathian Volcanic Arc which was active in the Middle-Upper Miocene in this area. It is built up of mainly andesitic and dacitic volcanic-sedimentary sequence which filled up the 1.5-3 km deep tectonic basin between two strike-slip faults: the Hernád Fault (W) and the Bodrog Fault (SE). Though the most tectonically active phase was during the Miocene, minor recent tectonism is observed in the area in the form of rare 2 to 3 M earthquakes. Due to its relatively low activity, the complexity and the thickness of the volcano-sediments, the tectonism and its effect on the recent shape of the mountain was not accurately mapped.
The present study aims to reveal the possible connections between the morphology and the present day stress field of the area. In this regard, several stress field model has been generated with the web based application “Geonuleus” accompanied with morphotectonic statistical analyses of the DEM from the region.
The method is based on the categorization of neotectonic lineaments (faults) by their geodynamic properties using the TPO method (Type-Property-Orientation) naming system for eventually generate the active stress field that reigns the region (Albert et al. 2016). The ALOS Palsar DEM (12.5 m resolution) has been used for the morphotectonic study. During the process, multiple filter have been utilized to eliminate the noise and to highlight lineaments (e.g. directional perpendicular filters). A statistical analysis was done from the lineaments orientation in order to define the general trend and to compare it with the main neotectonic directions and the stress field that have produced them.
The study area concentrated on the western part of the mountain since the detailed geophysical data is available only from that area (Bodor, 2011). The area was subdivided into three region based on the difference of the lithology, the tectonic regime and the topography (northern area, the western side of the Hernád stream and the eastern side of the Hernád stream). The result of the modeling shows a confluence between the two methods (SFM and the morphometry) especially in the western part with a regional N-S stress orientation. In the eastern side the flexure is clearly highlighted by stress trend movement. It is important to report that the model could be enhanced with further detailed data.
From the part of G.A. financial support was provided from the NRDI Fund of Hungary, Thematic Excellence Programme no. TKP2020-NKA-06 (National Challenges Subprogramme) funding scheme.
References:
Albert, G., Barancsuk, Á., & Szentpéteri, K. 2016. Stress field modelling from digital geological map data. Geophysical Research Abstracts, v. 18, EGU2016-14565.
Bodor B. 2011: A Hernád-árok szerkezetföldtani vizsgálata. MSc thesis, Eötvös University, Dept. Regional Geology, 99 p
How to cite: Ammar, S. and Albert, G.: Morphotectonic assessment in the Tokaj Mountain region (Hungary), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15843, https://doi.org/10.5194/egusphere-egu21-15843, 2021.
GM2.8 – Environmental Seismology: Deciphering Earth’s surface processes with seismic methods
EGU21-954 | vPICO presentations | GM2.8
Seismic inversions of large, rapid landslides: what they can and cannot tell us about event dynamicsKate Allstadt, Andrew Mitchell, Liam Toney, David George, and Scott McDougall
Researchers are increasingly incorporating force histories derived from long-period seismic waves into multidisciplinary studies of large, rapid landslides. The force history can provide important information about what happened during failure — information that complements data available from field investigations and remote sensing analyses. It can also provide additional constraints on the dynamics of landslide motion than can be used to validate and/or calibrate numerical landslide models. However, the inversions need to be of high quality and must be interpreted properly. Because this technique is relatively new, we are still discovering how to best conduct inversions to obtain robust results and how to appropriately interpret these results. In this study, we run numerical models of landslides with idealized source and path geometries using two different modeling packages, DAN3D and D-Claw, and we use the model outputs to generate synthetic long-period seismic data. Both models use depth-averaged flow equations over 3D topography, with DAN3D using semi-empirical material rheologies and D-Claw using a two-phase granular and fluid flow approach. To examine the influence of station azimuthal coverage and distance, we synthesize seismic data for a wide range of possible station configurations. We then use these synthetic seismic data to conduct seismic inversions using the recently released open-source Python-based software package, lsforce (https://code.usgs.gov/ghsc/lhp/lsforce). In doing these inversions, we add differing levels and types of noise, vary the inversion options (e.g., frequency range, regularization techniques) and then compare the results to the “known” dynamics of the modeled idealized landslides. We aim to understand common artefacts, limitations, and other potential pitfalls in interpretation, to guide the inversion process in future studies. We repeat this process for idealized landslides of increasing complexity, including multi-part failures, sinuous paths, and gradual versus sudden initiations, to simulate how these characteristics are reflected in the force history and to better understand what level of detail can be constrained from the seismic inversion. This work will help guide researchers to obtain more reliable information about landslide dynamics from seismic inversions in future landslide studies.
How to cite: Allstadt, K., Mitchell, A., Toney, L., George, D., and McDougall, S.: Seismic inversions of large, rapid landslides: what they can and cannot tell us about event dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-954, https://doi.org/10.5194/egusphere-egu21-954, 2021.
Researchers are increasingly incorporating force histories derived from long-period seismic waves into multidisciplinary studies of large, rapid landslides. The force history can provide important information about what happened during failure — information that complements data available from field investigations and remote sensing analyses. It can also provide additional constraints on the dynamics of landslide motion than can be used to validate and/or calibrate numerical landslide models. However, the inversions need to be of high quality and must be interpreted properly. Because this technique is relatively new, we are still discovering how to best conduct inversions to obtain robust results and how to appropriately interpret these results. In this study, we run numerical models of landslides with idealized source and path geometries using two different modeling packages, DAN3D and D-Claw, and we use the model outputs to generate synthetic long-period seismic data. Both models use depth-averaged flow equations over 3D topography, with DAN3D using semi-empirical material rheologies and D-Claw using a two-phase granular and fluid flow approach. To examine the influence of station azimuthal coverage and distance, we synthesize seismic data for a wide range of possible station configurations. We then use these synthetic seismic data to conduct seismic inversions using the recently released open-source Python-based software package, lsforce (https://code.usgs.gov/ghsc/lhp/lsforce). In doing these inversions, we add differing levels and types of noise, vary the inversion options (e.g., frequency range, regularization techniques) and then compare the results to the “known” dynamics of the modeled idealized landslides. We aim to understand common artefacts, limitations, and other potential pitfalls in interpretation, to guide the inversion process in future studies. We repeat this process for idealized landslides of increasing complexity, including multi-part failures, sinuous paths, and gradual versus sudden initiations, to simulate how these characteristics are reflected in the force history and to better understand what level of detail can be constrained from the seismic inversion. This work will help guide researchers to obtain more reliable information about landslide dynamics from seismic inversions in future landslide studies.
How to cite: Allstadt, K., Mitchell, A., Toney, L., George, D., and McDougall, S.: Seismic inversions of large, rapid landslides: what they can and cannot tell us about event dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-954, https://doi.org/10.5194/egusphere-egu21-954, 2021.
EGU21-13572 | vPICO presentations | GM2.8
An efficient physic-based event detection algorithm inspired by music information retrievalReza Dokht Dolatabadi Esfahani, Frank Scherbaum, Fabrice Cotton, and Matthias Ohrnberger
In the last decade, the increasing number and spatial density of seismological stations provide unprecedented opportunities for recording various natural and human-related events in continuous records. Diverse methods have been proposed for event detection, classification, and characterization, but few of them are based on the physical properties of the events. In this study, inspired by music information retrieval methods such as audio fingerprinting, we present a time-efficient event detection method based on capturing the physical properties of seismic signatures such as corner frequency, high-frequency fall-off, and complexity of signature. The zero-crossing rate of the recorded signal is used to estimate the corner frequency, which is the dominant frequency in the velocity domain of record. The high-frequency fall-off can be estimated in the time-frequency spectrogram by finding the frequency below which 75% of the energy of the spectrum is produced. The complexity of the spectrum of the recorded signal is finally represented by a second-order polynomial coefficient fitting the spectrum and capturing the slope of the source spectra. Also, we use the spectral flatness to quantify the noise properties. We validate the proposed procedure to synthetic data generated by the stochastic simulation method. We finally apply the method to real data sets to detect the seismic precursors for the Nuugaatsiaq landslide. We separate the earthquake event and precursory signals because of different corner frequencies and show that the precursory signals started for hours before the main landslide.
How to cite: Dokht Dolatabadi Esfahani, R., Scherbaum, F., Cotton, F., and Ohrnberger, M.: An efficient physic-based event detection algorithm inspired by music information retrieval, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13572, https://doi.org/10.5194/egusphere-egu21-13572, 2021.
In the last decade, the increasing number and spatial density of seismological stations provide unprecedented opportunities for recording various natural and human-related events in continuous records. Diverse methods have been proposed for event detection, classification, and characterization, but few of them are based on the physical properties of the events. In this study, inspired by music information retrieval methods such as audio fingerprinting, we present a time-efficient event detection method based on capturing the physical properties of seismic signatures such as corner frequency, high-frequency fall-off, and complexity of signature. The zero-crossing rate of the recorded signal is used to estimate the corner frequency, which is the dominant frequency in the velocity domain of record. The high-frequency fall-off can be estimated in the time-frequency spectrogram by finding the frequency below which 75% of the energy of the spectrum is produced. The complexity of the spectrum of the recorded signal is finally represented by a second-order polynomial coefficient fitting the spectrum and capturing the slope of the source spectra. Also, we use the spectral flatness to quantify the noise properties. We validate the proposed procedure to synthetic data generated by the stochastic simulation method. We finally apply the method to real data sets to detect the seismic precursors for the Nuugaatsiaq landslide. We separate the earthquake event and precursory signals because of different corner frequencies and show that the precursory signals started for hours before the main landslide.
How to cite: Dokht Dolatabadi Esfahani, R., Scherbaum, F., Cotton, F., and Ohrnberger, M.: An efficient physic-based event detection algorithm inspired by music information retrieval, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13572, https://doi.org/10.5194/egusphere-egu21-13572, 2021.
EGU21-12173 | vPICO presentations | GM2.8
Information on gravitational mass movements obtained from the spectrograms of their seismic signals generatedEmma Surinach and E. Leticia Flores-Márquez
An understanding of the characteristics of a mass movement descending a slope enables us to obtain a better control through models and also to reduce its associated risks. The seismic signals generated by the mass movement are mainly caused by friction of the moving mass on the ground. Most of the studies of the seismic signals use the spectrograms as a complementary information of the signals. Our study seeks to expand the current applications of the spectrograms using the information contained in them. A spectrogram represents the evolution in time of the frequency content of a time series. It can also be read as a 3D representation of amplitude, frequency and time of the seismic signal. The spectrograms of the seismic signals generated by a mass movement that descend a slope and approach a seismic sensor can be divided into sections: SON (Signal ONset), SOV (Signal Over) and SEN (Signal End), depending on whether the gravitational mass movement is approaching the sensor, is on it or is moving away from it.
The method presented here consist of analyzing the spectrogram as an image, applying image processing techniques as “Hough Transform”. This method allows us to obtain quantitative information from the spectrograms. Our aim is to obtain the parameters of the shape of the spectrograms, focused on SON section, to create indicators linked to the evolution of the mass movement, for example the speed. The method is applied to spectrograms of three types of gravitational mass movements: snow avalanches (7), lahars (4), and debris flows (1). The results indicate similarities in the shape of the spectrograms of the different types of mass movement, prevailing, however, the specific characteristics of each type.
How to cite: Surinach, E. and Flores-Márquez, E. L.: Information on gravitational mass movements obtained from the spectrograms of their seismic signals generated, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12173, https://doi.org/10.5194/egusphere-egu21-12173, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
An understanding of the characteristics of a mass movement descending a slope enables us to obtain a better control through models and also to reduce its associated risks. The seismic signals generated by the mass movement are mainly caused by friction of the moving mass on the ground. Most of the studies of the seismic signals use the spectrograms as a complementary information of the signals. Our study seeks to expand the current applications of the spectrograms using the information contained in them. A spectrogram represents the evolution in time of the frequency content of a time series. It can also be read as a 3D representation of amplitude, frequency and time of the seismic signal. The spectrograms of the seismic signals generated by a mass movement that descend a slope and approach a seismic sensor can be divided into sections: SON (Signal ONset), SOV (Signal Over) and SEN (Signal End), depending on whether the gravitational mass movement is approaching the sensor, is on it or is moving away from it.
The method presented here consist of analyzing the spectrogram as an image, applying image processing techniques as “Hough Transform”. This method allows us to obtain quantitative information from the spectrograms. Our aim is to obtain the parameters of the shape of the spectrograms, focused on SON section, to create indicators linked to the evolution of the mass movement, for example the speed. The method is applied to spectrograms of three types of gravitational mass movements: snow avalanches (7), lahars (4), and debris flows (1). The results indicate similarities in the shape of the spectrograms of the different types of mass movement, prevailing, however, the specific characteristics of each type.
How to cite: Surinach, E. and Flores-Márquez, E. L.: Information on gravitational mass movements obtained from the spectrograms of their seismic signals generated, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12173, https://doi.org/10.5194/egusphere-egu21-12173, 2021.
EGU21-3238 | vPICO presentations | GM2.8
Geomorphologically-controlled seismic signals at Mount St. Helens volcanoLuca De Siena, Simona Gabrielli, and Matteo Spagnolo
In volcanoes, topography and shallow morphology can substantially modify seismic signals, tracing anisotropic signatures in the crust's most surficial layers. To better understand the influence of key morphologies, forward modelling of the seismic waveforms is fundamental. Here, we introduce a forward model of the seismic wave equation developed with finite-differences schemes in anisotropic viscoelastic media. The observation of geomorphological features and the surficial geology map of Mount St. Helens are used to reproduce the scattering and anisotropic effects caused by shallow heterogeneity on seismic signals. The main aim is to understand if and to which lengths lateral anisotropic variations in geomorphological features control the generation and propagation of low-frequency seismic signals, focusing especially on the timing of surface-wave enhancement.
The model shows how the geomorphology-derived anisotropy controls the travel times of the horizontally polarized S waves (SH), in particular along with two directions: WNW-ESE, following the trend of a buried fault, and NS, consistent with the main morphological difference between southern (mostly untouched by the 1980 eruption) and northern (collapsed in 1980’s blast) flanks of the volcano. An analysis of the waveforms of a shallow event of 2005 (during the last eruption of Mt. St. Helens), located in the crater, shows how an isotropic model can reproduce the arrival of the SH wave at high frequencies (10 Hz). The introduction of an effective anisotropic medium is necessary to explain the arrivals for stations deployed across the north-northwestern flank of the volcano at lower frequencies (1 Hz and 6 Hz). The heterogeneity in the crater (e.g., the glacier inside the crater covered by a rock-debris layer) can create interfaces made mostly of unconsolidated materials. As also demonstrated by radiative transfer simulation, the crater acts as a primary source of surface waves dominating the seismic signals.
How to cite: De Siena, L., Gabrielli, S., and Spagnolo, M.: Geomorphologically-controlled seismic signals at Mount St. Helens volcano, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3238, https://doi.org/10.5194/egusphere-egu21-3238, 2021.
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Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
In volcanoes, topography and shallow morphology can substantially modify seismic signals, tracing anisotropic signatures in the crust's most surficial layers. To better understand the influence of key morphologies, forward modelling of the seismic waveforms is fundamental. Here, we introduce a forward model of the seismic wave equation developed with finite-differences schemes in anisotropic viscoelastic media. The observation of geomorphological features and the surficial geology map of Mount St. Helens are used to reproduce the scattering and anisotropic effects caused by shallow heterogeneity on seismic signals. The main aim is to understand if and to which lengths lateral anisotropic variations in geomorphological features control the generation and propagation of low-frequency seismic signals, focusing especially on the timing of surface-wave enhancement.
The model shows how the geomorphology-derived anisotropy controls the travel times of the horizontally polarized S waves (SH), in particular along with two directions: WNW-ESE, following the trend of a buried fault, and NS, consistent with the main morphological difference between southern (mostly untouched by the 1980 eruption) and northern (collapsed in 1980’s blast) flanks of the volcano. An analysis of the waveforms of a shallow event of 2005 (during the last eruption of Mt. St. Helens), located in the crater, shows how an isotropic model can reproduce the arrival of the SH wave at high frequencies (10 Hz). The introduction of an effective anisotropic medium is necessary to explain the arrivals for stations deployed across the north-northwestern flank of the volcano at lower frequencies (1 Hz and 6 Hz). The heterogeneity in the crater (e.g., the glacier inside the crater covered by a rock-debris layer) can create interfaces made mostly of unconsolidated materials. As also demonstrated by radiative transfer simulation, the crater acts as a primary source of surface waves dominating the seismic signals.
How to cite: De Siena, L., Gabrielli, S., and Spagnolo, M.: Geomorphologically-controlled seismic signals at Mount St. Helens volcano, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3238, https://doi.org/10.5194/egusphere-egu21-3238, 2021.
EGU21-3763 | vPICO presentations | GM2.8
Multi-phase seismic source imprint of tropical cyclonesLise Retailleau and Lucia Gualtieri
The coupling between the ocean activity driven by winds and the solid Earth generates seismic signals recorded by seismometers worldwide. The 2-10 s period band, known as secondary microseism, represents the largest background seismic wavefield. While moving over the ocean, tropical cyclones generate particularly strong and localized sources of secondary microseisms that are detected remotely by seismic arrays.
We assess and compare the seismic sources of P, SV, and SH waves associated with typhoon Ioke during its extra-tropical transition. To understand their generation mechanisms, we compare the observed multi-phase sources with theoretical sources computed with a numerical ocean wave model, and we assess the influence of the ocean resonance (or ocean site effect) and coastal reflection of ocean waves. We show how the location and lateral extent of the associated seismic source is period- and phase-dependent. This information is crucial for the use of body waves for ambient noise imaging and gives insights about the sea state, complementary to satellite data.
How to cite: Retailleau, L. and Gualtieri, L.: Multi-phase seismic source imprint of tropical cyclones, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3763, https://doi.org/10.5194/egusphere-egu21-3763, 2021.
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The coupling between the ocean activity driven by winds and the solid Earth generates seismic signals recorded by seismometers worldwide. The 2-10 s period band, known as secondary microseism, represents the largest background seismic wavefield. While moving over the ocean, tropical cyclones generate particularly strong and localized sources of secondary microseisms that are detected remotely by seismic arrays.
We assess and compare the seismic sources of P, SV, and SH waves associated with typhoon Ioke during its extra-tropical transition. To understand their generation mechanisms, we compare the observed multi-phase sources with theoretical sources computed with a numerical ocean wave model, and we assess the influence of the ocean resonance (or ocean site effect) and coastal reflection of ocean waves. We show how the location and lateral extent of the associated seismic source is period- and phase-dependent. This information is crucial for the use of body waves for ambient noise imaging and gives insights about the sea state, complementary to satellite data.
How to cite: Retailleau, L. and Gualtieri, L.: Multi-phase seismic source imprint of tropical cyclones, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3763, https://doi.org/10.5194/egusphere-egu21-3763, 2021.
EGU21-6390 | vPICO presentations | GM2.8
Monitoring Rock Slope Instabilities Using Frequency Domain Decomposition Modal AnalysisMauro Häusler, Clotaire Michel, Jan Burjánek, and Donat Fäh
Measuring ambient seismic vibration provides a promising tool to monitor unstable rock slopes due to its independence from actual surface deformations. It is generally observed that the seismic wavefield, arising from ambient vibrations, polarizes perpendicular to open fractures and that unstable slopes exhibit strong wavefield amplifications compared to stable reference sites. Rock slope instabilities dominated by deep persistent fracture sets exhibit normal mode behaviour due to standing wave phenomena within individual compartments of the unstable volume. Techniques to assess such behavior are well established in mechanical and civil engineering to assess the dynamic response and possibly the structural integrity of the structure studied.
We performed enhanced frequency domain decomposition modal analysis on ambient vibration data acquired in real-time on an unstable rock site with a volume larger than 150,000 m3 near Preonzo, Switzerland. We tracked the resonance frequency and normal mode polarization of the first two modes over a period of four years. In addition, we show the development of the modal damping ratio of the fundental mode over time, which is a measure of energy dissipation within and out of the system. We found that the dynamic properties of the rock structure experienced annual variations and that they are primarily controlled by temperature and only secondarily by the exension and closure of large-scale fractures. Even though no large slope failure was observed during the monitoring period, the dataset provides a reference model for ongoing slope monitoring, as the resonance frequency and damping ratio is expected to change significantly prior to failure.
How to cite: Häusler, M., Michel, C., Burjánek, J., and Fäh, D.: Monitoring Rock Slope Instabilities Using Frequency Domain Decomposition Modal Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6390, https://doi.org/10.5194/egusphere-egu21-6390, 2021.
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Measuring ambient seismic vibration provides a promising tool to monitor unstable rock slopes due to its independence from actual surface deformations. It is generally observed that the seismic wavefield, arising from ambient vibrations, polarizes perpendicular to open fractures and that unstable slopes exhibit strong wavefield amplifications compared to stable reference sites. Rock slope instabilities dominated by deep persistent fracture sets exhibit normal mode behaviour due to standing wave phenomena within individual compartments of the unstable volume. Techniques to assess such behavior are well established in mechanical and civil engineering to assess the dynamic response and possibly the structural integrity of the structure studied.
We performed enhanced frequency domain decomposition modal analysis on ambient vibration data acquired in real-time on an unstable rock site with a volume larger than 150,000 m3 near Preonzo, Switzerland. We tracked the resonance frequency and normal mode polarization of the first two modes over a period of four years. In addition, we show the development of the modal damping ratio of the fundental mode over time, which is a measure of energy dissipation within and out of the system. We found that the dynamic properties of the rock structure experienced annual variations and that they are primarily controlled by temperature and only secondarily by the exension and closure of large-scale fractures. Even though no large slope failure was observed during the monitoring period, the dataset provides a reference model for ongoing slope monitoring, as the resonance frequency and damping ratio is expected to change significantly prior to failure.
How to cite: Häusler, M., Michel, C., Burjánek, J., and Fäh, D.: Monitoring Rock Slope Instabilities Using Frequency Domain Decomposition Modal Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6390, https://doi.org/10.5194/egusphere-egu21-6390, 2021.
EGU21-8793 | vPICO presentations | GM2.8
Spatial and temporal variability, triggers and drivers of seismically detected rockfalls in the Reintal catchment, German AlpsAnne Schöpa, Jens Turowski, and Niels Hovius
Rockfalls are a substantial geohazard to human life and infrastructure in mountainous regions but we still lack detailed understanding of when and where rockfalls occur, and which environmental conditions lead to rockfall over diurnal, seasonal and annual timescales. This is due to the fact that direct observations in alpine landscapes are difficult to make and long, high-resolution time series of measurements are rare. Using seismic techniques, we can collect near-complete catalogues of geomorphic events and record their distributions in time and space. This allows studying the interaction of process domains, the role of various rockfall triggers, and lead and lag times with unprecedented detail.
We use the unique six-year long seismic dataset of the Reintal rockfall observatory in the German Alps to detect, classify and locate rockfalls in the Reintal catchment. This rockfall catalogue enables us to analyse the spatial and temporal variability of rockfalls spanning several orders of magnitude in size. We test the hypothesis that variations of rockfall in the Reintal catchment are dominated by seasonal patterns. In combination with weather data, we examine boundary conditions, drivers and triggers of rockfalls in this alpine catchment.
How to cite: Schöpa, A., Turowski, J., and Hovius, N.: Spatial and temporal variability, triggers and drivers of seismically detected rockfalls in the Reintal catchment, German Alps , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8793, https://doi.org/10.5194/egusphere-egu21-8793, 2021.
Rockfalls are a substantial geohazard to human life and infrastructure in mountainous regions but we still lack detailed understanding of when and where rockfalls occur, and which environmental conditions lead to rockfall over diurnal, seasonal and annual timescales. This is due to the fact that direct observations in alpine landscapes are difficult to make and long, high-resolution time series of measurements are rare. Using seismic techniques, we can collect near-complete catalogues of geomorphic events and record their distributions in time and space. This allows studying the interaction of process domains, the role of various rockfall triggers, and lead and lag times with unprecedented detail.
We use the unique six-year long seismic dataset of the Reintal rockfall observatory in the German Alps to detect, classify and locate rockfalls in the Reintal catchment. This rockfall catalogue enables us to analyse the spatial and temporal variability of rockfalls spanning several orders of magnitude in size. We test the hypothesis that variations of rockfall in the Reintal catchment are dominated by seasonal patterns. In combination with weather data, we examine boundary conditions, drivers and triggers of rockfalls in this alpine catchment.
How to cite: Schöpa, A., Turowski, J., and Hovius, N.: Spatial and temporal variability, triggers and drivers of seismically detected rockfalls in the Reintal catchment, German Alps , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8793, https://doi.org/10.5194/egusphere-egu21-8793, 2021.
EGU21-7012 | vPICO presentations | GM2.8
Mapping Groundwater Fluctuations in the Coastal Los Angeles Basin by Seismic InterferometryShujuan Mao, Michel Campillo, Robert van der Hilst, and Albanne Lecointre
Changes in crustal seismic velocity (dv/v) can be monitored continuously in time by interferometry of seismic ambient noise. This approach has been successfully employed to study temporal perturbations in stress fields, rock fractures, and fluids. Here we go one step further with this monitoring technique, by not only detecting the temporal changes but also imaging the inhomogeneous spatial distributions of dv/v. We implement the spatial imaging by leveraging travel-time shifts at successive lag times and solving inverse problems based on coda-wave sensitivity kernels. We then use these space-time observations of dv/v to investigate the groundwater fluctuations in the Coastal Los Angeles (LA) Basin during 2000-2020. Imaging of dv/v demonstrates the spatial patterns of groundwater variations: Seasonal changes are most pronounced within confined zones in Santa Ana Basin and LA Central Basin, whereas the long-term changes extend to a broader area including the unconfined forebay. We further compare dv/v observations with InSAR measurements and find strongly consistent spatial patterns. Compared with surface deformation measurements, dv/v additionally help to characterize the depths of several aquifers in the study area. This real-data application substantiates the validity of our dv/v imaging protocol, and shows the promise of using spatio-temporal dv/v observations to monitor surficial hydrological processes.
How to cite: Mao, S., Campillo, M., van der Hilst, R., and Lecointre, A.: Mapping Groundwater Fluctuations in the Coastal Los Angeles Basin by Seismic Interferometry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7012, https://doi.org/10.5194/egusphere-egu21-7012, 2021.
Changes in crustal seismic velocity (dv/v) can be monitored continuously in time by interferometry of seismic ambient noise. This approach has been successfully employed to study temporal perturbations in stress fields, rock fractures, and fluids. Here we go one step further with this monitoring technique, by not only detecting the temporal changes but also imaging the inhomogeneous spatial distributions of dv/v. We implement the spatial imaging by leveraging travel-time shifts at successive lag times and solving inverse problems based on coda-wave sensitivity kernels. We then use these space-time observations of dv/v to investigate the groundwater fluctuations in the Coastal Los Angeles (LA) Basin during 2000-2020. Imaging of dv/v demonstrates the spatial patterns of groundwater variations: Seasonal changes are most pronounced within confined zones in Santa Ana Basin and LA Central Basin, whereas the long-term changes extend to a broader area including the unconfined forebay. We further compare dv/v observations with InSAR measurements and find strongly consistent spatial patterns. Compared with surface deformation measurements, dv/v additionally help to characterize the depths of several aquifers in the study area. This real-data application substantiates the validity of our dv/v imaging protocol, and shows the promise of using spatio-temporal dv/v observations to monitor surficial hydrological processes.
How to cite: Mao, S., Campillo, M., van der Hilst, R., and Lecointre, A.: Mapping Groundwater Fluctuations in the Coastal Los Angeles Basin by Seismic Interferometry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7012, https://doi.org/10.5194/egusphere-egu21-7012, 2021.
EGU21-3383 | vPICO presentations | GM2.8 | Highlight
Combining Seismology, Hydrogeology and Climatology for Monitoring Karstic Groundwater Reservoirs.Anthony Abi Nader, Julie Albaric, Anais Marchand, Marine Gros, Marc Steinmann, Benjamin Fores, Stefani Vanessa, Benjamin Pohl, Hélène Celle-Jeanton, and Christian Sue
Due to their heterogeneity and inaccessibility, karst aquifers are poorly understood along with their functioning, complex structure and behavior in response to flood events. Conventional methods such as piezometers or other underground equipment give only punctual observations that are not very representative of the functioning of the aquifer at the scale of the catchment basin, nor show spatio-temporal variation that occur along the karst network. The objective of this work is to image the flow of water over time from rainfall to the aquifer outlet in a target catchment basin located in the Jura Mountains near Besançon (Eastern France, Fourbanne site of the 'Jurassic Karst' observatory), which hosts a karstic aquifer monitored since 2014 (Cholet et al. 2017). The approach consists in analyzing jointly seismological, hydrogeological and atmospheric data recorded on the aquifer. The instrumentation comprises 2 permanent seismometers, 2 Conductivity Temperature and Pressure (CTD) probes and 1 rain gauge, which will be completed by 65 seismic nodes, 30 rain gauges and 1 additional CTD for an acquisition period of 4 months. We observe that underground hydrological processes occurring in the aquifer, such as water flow or sediment transport, can be precisely monitored using data from one seismometer installed inside the karst conduit. Furthermore, noise cross-correlation analysis will be carried out to detect seismic velocity variations in the medium induced by fluid saturation changes (Froment, 2011). Several studies have demonstrated that these methods can detect changes in saturation in underground aquifers (Lecocq et al. 2017; Voisin et al., 2017). Accordingly, velocity variation will be correlated with flow velocity, soil water content or even permeability, based on measurements of the volume of water entering the basin and circulating in the karstic network obtained from data collected from the CTDs and rain gauges.
References:
FROMENT B., 2011 – Utilisation du bruit sismique ambiant dans le suivi temporel de structures géologiques. [Grenoble]: École doctorale terre, univers, environnement.
LECOCQ, T., LONGUEVERNE, L., PEDERSEN, H.A., 2017 – Monitoring ground water storage at mesoscale using seismic noise: 30 years of continuous observation and thermo-elastic and hydrological modeling. Sci Rep 7, 14241 (2017). https://doi.org/10.1038/s41598-017-14468-9
VOISIN, C., GUZMAN, M., REFLOCH, A., TARUSELLI, M. and GARAMBOIS, S., 2017 – Groundwater Monitoring with Passive Seismic Interferometry. Journal of Water Resource and Protection, 9, 1414-1427. doi: 10.4236/jwarp.2017.912091.
CHOLET, C., CHARLIER, J.-B., MOUSSA, R., STEINMANN, M., DENIMAL, S., 2017 – Assessing lateral flows and solute transport during floods in a conduit-flow-dominated karst system using the inverse problem for the advection–diffusion equation. Hydrology and Earth System Sciences 21, 3635–3653. https://doi.org/10.5194/hess-21-3635-2017
How to cite: Abi Nader, A., Albaric, J., Marchand, A., Gros, M., Steinmann, M., Fores, B., Vanessa, S., Pohl, B., Celle-Jeanton, H., and Sue, C.: Combining Seismology, Hydrogeology and Climatology for Monitoring Karstic Groundwater Reservoirs., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3383, https://doi.org/10.5194/egusphere-egu21-3383, 2021.
Due to their heterogeneity and inaccessibility, karst aquifers are poorly understood along with their functioning, complex structure and behavior in response to flood events. Conventional methods such as piezometers or other underground equipment give only punctual observations that are not very representative of the functioning of the aquifer at the scale of the catchment basin, nor show spatio-temporal variation that occur along the karst network. The objective of this work is to image the flow of water over time from rainfall to the aquifer outlet in a target catchment basin located in the Jura Mountains near Besançon (Eastern France, Fourbanne site of the 'Jurassic Karst' observatory), which hosts a karstic aquifer monitored since 2014 (Cholet et al. 2017). The approach consists in analyzing jointly seismological, hydrogeological and atmospheric data recorded on the aquifer. The instrumentation comprises 2 permanent seismometers, 2 Conductivity Temperature and Pressure (CTD) probes and 1 rain gauge, which will be completed by 65 seismic nodes, 30 rain gauges and 1 additional CTD for an acquisition period of 4 months. We observe that underground hydrological processes occurring in the aquifer, such as water flow or sediment transport, can be precisely monitored using data from one seismometer installed inside the karst conduit. Furthermore, noise cross-correlation analysis will be carried out to detect seismic velocity variations in the medium induced by fluid saturation changes (Froment, 2011). Several studies have demonstrated that these methods can detect changes in saturation in underground aquifers (Lecocq et al. 2017; Voisin et al., 2017). Accordingly, velocity variation will be correlated with flow velocity, soil water content or even permeability, based on measurements of the volume of water entering the basin and circulating in the karstic network obtained from data collected from the CTDs and rain gauges.
References:
FROMENT B., 2011 – Utilisation du bruit sismique ambiant dans le suivi temporel de structures géologiques. [Grenoble]: École doctorale terre, univers, environnement.
LECOCQ, T., LONGUEVERNE, L., PEDERSEN, H.A., 2017 – Monitoring ground water storage at mesoscale using seismic noise: 30 years of continuous observation and thermo-elastic and hydrological modeling. Sci Rep 7, 14241 (2017). https://doi.org/10.1038/s41598-017-14468-9
VOISIN, C., GUZMAN, M., REFLOCH, A., TARUSELLI, M. and GARAMBOIS, S., 2017 – Groundwater Monitoring with Passive Seismic Interferometry. Journal of Water Resource and Protection, 9, 1414-1427. doi: 10.4236/jwarp.2017.912091.
CHOLET, C., CHARLIER, J.-B., MOUSSA, R., STEINMANN, M., DENIMAL, S., 2017 – Assessing lateral flows and solute transport during floods in a conduit-flow-dominated karst system using the inverse problem for the advection–diffusion equation. Hydrology and Earth System Sciences 21, 3635–3653. https://doi.org/10.5194/hess-21-3635-2017
How to cite: Abi Nader, A., Albaric, J., Marchand, A., Gros, M., Steinmann, M., Fores, B., Vanessa, S., Pohl, B., Celle-Jeanton, H., and Sue, C.: Combining Seismology, Hydrogeology and Climatology for Monitoring Karstic Groundwater Reservoirs., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3383, https://doi.org/10.5194/egusphere-egu21-3383, 2021.
EGU21-6253 | vPICO presentations | GM2.8 | Highlight
Geomorphological impact of storm Alex in the Maritime Alps, France: what can we learn from seismological observations?Małgorzata Chmiel, Maxime Godano, Marco Piantini, Diane Rivet, Jean-Paul Ampuero, Florent Gimbert, Maarten Bakker, Françoise Courboulex, Anthony Sladen, David Ambrois, and Pierre Brigode
On 2-3 October 2020, the Maritime Alps were struck by storm Alex, a violent meteorological event that triggered heavy rainfall in southeast France, more generally referred to as a "Mediterranean Episode". The Mediterranean episode generated cumulative 24-hour rainfall rate locally exceeding yearly averages (>500 mm per 24 hours). The torrential rains triggered hazardous sediment-transporting floods of an intensity never documented in the area causing several casualties, and large infrastructure and economic damage.
Rain and stream gauges’ measurements during the episode are incomplete and highly uncertain due to threshold saturation and destruction of measuring devices, and changes in the stream bed. However, 11 regional seismological stations of the French permanent network recorded continuous ground shaking during and after the episode. Significant ground unrest was generated by the geomorphological phenomena providing additional information on their temporal and spatial dynamics.
Here, we present results of the combined efforts in environmental and crustal seismology to better understand the spatiotemporal dynamics of the sediment-transporting floods and hydrological forcing on the solid Earth during and after the episode. For that, we first analyze seismic power, peak frequency, and dominant noise directions of seismic signals generated by sediment-transporting floods to infer bedload transport dynamics. Moreover, by using template matching we detect 93 small earthquakes that were triggered during the Alex episode exactly in the area where rainfall was maximum. This exceptional seismic swarm is possibly triggered by overpressure due to the water load in karsts, or changes in pore fluid pressure. Our results illustrate that seismological observations allow for better understanding and quantifying of the geomorphological impact of extreme weather phenomena in mountainous settings and the related hydro-geomorphological hazards.
How to cite: Chmiel, M., Godano, M., Piantini, M., Rivet, D., Ampuero, J.-P., Gimbert, F., Bakker, M., Courboulex, F., Sladen, A., Ambrois, D., and Brigode, P.: Geomorphological impact of storm Alex in the Maritime Alps, France: what can we learn from seismological observations?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6253, https://doi.org/10.5194/egusphere-egu21-6253, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
On 2-3 October 2020, the Maritime Alps were struck by storm Alex, a violent meteorological event that triggered heavy rainfall in southeast France, more generally referred to as a "Mediterranean Episode". The Mediterranean episode generated cumulative 24-hour rainfall rate locally exceeding yearly averages (>500 mm per 24 hours). The torrential rains triggered hazardous sediment-transporting floods of an intensity never documented in the area causing several casualties, and large infrastructure and economic damage.
Rain and stream gauges’ measurements during the episode are incomplete and highly uncertain due to threshold saturation and destruction of measuring devices, and changes in the stream bed. However, 11 regional seismological stations of the French permanent network recorded continuous ground shaking during and after the episode. Significant ground unrest was generated by the geomorphological phenomena providing additional information on their temporal and spatial dynamics.
Here, we present results of the combined efforts in environmental and crustal seismology to better understand the spatiotemporal dynamics of the sediment-transporting floods and hydrological forcing on the solid Earth during and after the episode. For that, we first analyze seismic power, peak frequency, and dominant noise directions of seismic signals generated by sediment-transporting floods to infer bedload transport dynamics. Moreover, by using template matching we detect 93 small earthquakes that were triggered during the Alex episode exactly in the area where rainfall was maximum. This exceptional seismic swarm is possibly triggered by overpressure due to the water load in karsts, or changes in pore fluid pressure. Our results illustrate that seismological observations allow for better understanding and quantifying of the geomorphological impact of extreme weather phenomena in mountainous settings and the related hydro-geomorphological hazards.
How to cite: Chmiel, M., Godano, M., Piantini, M., Rivet, D., Ampuero, J.-P., Gimbert, F., Bakker, M., Courboulex, F., Sladen, A., Ambrois, D., and Brigode, P.: Geomorphological impact of storm Alex in the Maritime Alps, France: what can we learn from seismological observations?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6253, https://doi.org/10.5194/egusphere-egu21-6253, 2021.
EGU21-12830 | vPICO presentations | GM2.8
Fluvial Seismology: Case Study of the Contagem River (Brasilia), BrazilHans-Balder Havenith, Yawar Hussain, and Susanne Maciel
Rainfall-induced landslides may pose a significant risk to communities and infrastructures. Such landslides are substantially impacted by the fluvial systems, therefore the continuous monitoring of the seasonal erosive potentials of these rivers are crucial. However, such environmental conditions the direct in-situ investigation is often a challenging task. Therefore, the present study aims at providing a brief overview of the use of ambient seismic noise for the dynamic monitoring of fluvial systems and a discussion about the preliminary results obtained from a Brazilian case study.
Data were acquired with single short-period (2 Hz) seismometers, REFTEK-130 data-logger and GPS lock, in dry and rainy days installed within a seasonal streams in Ribeirão Contagem watershed of the Federal district of Brazil. The pre-processing of ambient noise records include conversion from REFTEK to mini-seed format and saving data in units of velocity after removing the instrumental response. Then, the frequency content (spectrograms, percentiles), waveform characteristics (envelope) and polarization attributes of changes in ambient noise wave-fields induced by bed-load transport and water flow in dry and flooding days are analyzed.
A prominent increase in mean probabilistic power spectral density (PPSD) values are observed during rainy days within a frequency range of 10 Hz to 100 Hz. The polarization analysis shows that most of the recorded energy arrived from the river side. It is concluded that seismic attributes have their relation with the river generated ambient noise and can be used for the remote monitoring of such fluvial systems. Future studies dedicated to the dense surficial and geodetic surveying (also with UAV) are recommend for the detailed quantification of these seasonal river dynamics.
Keywords: Seismic records; bed-loads; spectrograms; percentile; envelope
How to cite: Havenith, H.-B., Hussain, Y., and Maciel, S.: Fluvial Seismology: Case Study of the Contagem River (Brasilia), Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12830, https://doi.org/10.5194/egusphere-egu21-12830, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Rainfall-induced landslides may pose a significant risk to communities and infrastructures. Such landslides are substantially impacted by the fluvial systems, therefore the continuous monitoring of the seasonal erosive potentials of these rivers are crucial. However, such environmental conditions the direct in-situ investigation is often a challenging task. Therefore, the present study aims at providing a brief overview of the use of ambient seismic noise for the dynamic monitoring of fluvial systems and a discussion about the preliminary results obtained from a Brazilian case study.
Data were acquired with single short-period (2 Hz) seismometers, REFTEK-130 data-logger and GPS lock, in dry and rainy days installed within a seasonal streams in Ribeirão Contagem watershed of the Federal district of Brazil. The pre-processing of ambient noise records include conversion from REFTEK to mini-seed format and saving data in units of velocity after removing the instrumental response. Then, the frequency content (spectrograms, percentiles), waveform characteristics (envelope) and polarization attributes of changes in ambient noise wave-fields induced by bed-load transport and water flow in dry and flooding days are analyzed.
A prominent increase in mean probabilistic power spectral density (PPSD) values are observed during rainy days within a frequency range of 10 Hz to 100 Hz. The polarization analysis shows that most of the recorded energy arrived from the river side. It is concluded that seismic attributes have their relation with the river generated ambient noise and can be used for the remote monitoring of such fluvial systems. Future studies dedicated to the dense surficial and geodetic surveying (also with UAV) are recommend for the detailed quantification of these seasonal river dynamics.
Keywords: Seismic records; bed-loads; spectrograms; percentile; envelope
How to cite: Havenith, H.-B., Hussain, Y., and Maciel, S.: Fluvial Seismology: Case Study of the Contagem River (Brasilia), Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12830, https://doi.org/10.5194/egusphere-egu21-12830, 2021.
EGU21-3223 | vPICO presentations | GM2.8
Joint Seismic and Acoustic Signals in a Boulder-Bed Channel along a Bedrock CanyonRon Nativ, Jens Turowski, Jonathan Laronne, Niels Hovius, and Liran Goren
Bedload transport is the dominant fluvial mechanism shaping canyons and constitutes a significant portion of sediments transported from mountains to oceans. Monitoring of bedload flux in bedrock canyons during large magnitude floods remains an outstanding problem in fluvial geomorphology, due to extreme hydraulic conditions and the risk to equipment and human life. Surrogate monitoring methods include the interpretation of seismic and acoustic signals generated by colliding transported grains. Establishing a reliable relationship between seismic and acoustic signals and bedload flux in such floods has hitherto not been attempted. Here we present seismic and acoustic data from two pairs of adjacent channel reaches in the Liwu river, Taiwan, that differ by the concentration of boulders, but otherwise share similar hydraulic conditions and drainage area (~ 60 km2). In each of the paired locations (Shakadang and Baiyang) we have setup a field experiment where seismic sensors and data loggers with a frequency acquisition resolution of 200 Hz, were deployed aside each of the boulder-bed - boulder-free channels. In Baiyang we have also installed a hydrophone, i.e., a microphone submerged in the water column, recording acoustic signals in frequencies up to 16,000 Hz. Our monitoring system recorded a flood during August 2019 where water stage rose from 1 to 3-4 meters within few hours. In the Baiyang stations, bedload transport onset, peak and cessation were resolved through manual listening to audio files recorded by the hydrophone and counting the number of inferred impacts that occurred during one-minute time intervals. The bedload transport event lasted more than 78 hours, peaked in the recession, thus producing a counterclockwise hysteresis between the power of the acoustic signal and the water depth, not observed in the seismic signals. Signals generated by bedload impacts excited the hydrophone at frequencies of 600 to 3000 Hz, and the seismic sensor at the boulder-free stations at 18 to 30 Hz. In contrast, the highest seismic power at the boulder-bed channels peaked at a frequency band of 50 to 80 Hz, which is commonly not associated with bedload nor with water turbulence. The peak in the high frequency bands suggests that boulder-bed channels may differ in how bedload and turbulence are expressed in terms of the seismic content. We hypothesize that the high frequency content may be a combination of (i) small bedload grains colliding onto boulders, and (ii) the coupled effect of enhanced turbulence with the proximity of the seismic station to the channel.
How to cite: Nativ, R., Turowski, J., Laronne, J., Hovius, N., and Goren, L.: Joint Seismic and Acoustic Signals in a Boulder-Bed Channel along a Bedrock Canyon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3223, https://doi.org/10.5194/egusphere-egu21-3223, 2021.
Bedload transport is the dominant fluvial mechanism shaping canyons and constitutes a significant portion of sediments transported from mountains to oceans. Monitoring of bedload flux in bedrock canyons during large magnitude floods remains an outstanding problem in fluvial geomorphology, due to extreme hydraulic conditions and the risk to equipment and human life. Surrogate monitoring methods include the interpretation of seismic and acoustic signals generated by colliding transported grains. Establishing a reliable relationship between seismic and acoustic signals and bedload flux in such floods has hitherto not been attempted. Here we present seismic and acoustic data from two pairs of adjacent channel reaches in the Liwu river, Taiwan, that differ by the concentration of boulders, but otherwise share similar hydraulic conditions and drainage area (~ 60 km2). In each of the paired locations (Shakadang and Baiyang) we have setup a field experiment where seismic sensors and data loggers with a frequency acquisition resolution of 200 Hz, were deployed aside each of the boulder-bed - boulder-free channels. In Baiyang we have also installed a hydrophone, i.e., a microphone submerged in the water column, recording acoustic signals in frequencies up to 16,000 Hz. Our monitoring system recorded a flood during August 2019 where water stage rose from 1 to 3-4 meters within few hours. In the Baiyang stations, bedload transport onset, peak and cessation were resolved through manual listening to audio files recorded by the hydrophone and counting the number of inferred impacts that occurred during one-minute time intervals. The bedload transport event lasted more than 78 hours, peaked in the recession, thus producing a counterclockwise hysteresis between the power of the acoustic signal and the water depth, not observed in the seismic signals. Signals generated by bedload impacts excited the hydrophone at frequencies of 600 to 3000 Hz, and the seismic sensor at the boulder-free stations at 18 to 30 Hz. In contrast, the highest seismic power at the boulder-bed channels peaked at a frequency band of 50 to 80 Hz, which is commonly not associated with bedload nor with water turbulence. The peak in the high frequency bands suggests that boulder-bed channels may differ in how bedload and turbulence are expressed in terms of the seismic content. We hypothesize that the high frequency content may be a combination of (i) small bedload grains colliding onto boulders, and (ii) the coupled effect of enhanced turbulence with the proximity of the seismic station to the channel.
How to cite: Nativ, R., Turowski, J., Laronne, J., Hovius, N., and Goren, L.: Joint Seismic and Acoustic Signals in a Boulder-Bed Channel along a Bedrock Canyon, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3223, https://doi.org/10.5194/egusphere-egu21-3223, 2021.
EGU21-8800 | vPICO presentations | GM2.8
Applying dense seismic array monitoring to locate fluvial processes during floods in a braided river reachMarco Piantini, Florent Gimbert, Maarten Bakker, Alain Recking, and Ugo Nanni
Over the last decade, seismic techniques have provided unique observational constraints on Earth surface processes. In particular, dense seismic array monitoring has recently allowed the detailed investigation of noise sources and their spatiotemporal dynamics. Despite their large potential, these approaches have not yet been applied for the monitoring of fluvial processes. In a context where traditional methods often do not provide data with adequate temporal and spatial resolution, the use of dense arrays could allow the identification and tracking of different sources of river-induced seismic ground vibrations (e.g. turbulence and bedload transport), which would provide insight in river functioning and morphological evolution.
Here, we study the potential of dense seismic array monitoring by analysing data from a 4-month long field survey, which we conducted in summer 2019 along a 600-m long braided reach of the Séveraisse river (French Alps). We installed a network of 40 to 80 seismometers on both river banks, predominantly deployed in 4-seismometer subarrays, and we supplement these seismic observations with flow gauging measurements and time-lapse imagery covering the study area. We present a preliminary analysis that focuses on a high-flow event that occurred at the end of the melt season. During this event, we observe impulsive signals that are coherently detected over the array, and which we interpret as being associated with the bedload transport of clusters of coarse grains. Through phase-delay analysis we are able to locate episodes of motion at high temporal resolution and investigate their spatiotemporal dynamics with respect to river morphology and morphological changes observed from the time-lapse images. Our work demonstrates the unique capability of using dense seismic arrays to better understand the fluvial processes that play an important role in storing and transferring sediments in braided rivers.
How to cite: Piantini, M., Gimbert, F., Bakker, M., Recking, A., and Nanni, U.: Applying dense seismic array monitoring to locate fluvial processes during floods in a braided river reach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8800, https://doi.org/10.5194/egusphere-egu21-8800, 2021.
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Over the last decade, seismic techniques have provided unique observational constraints on Earth surface processes. In particular, dense seismic array monitoring has recently allowed the detailed investigation of noise sources and their spatiotemporal dynamics. Despite their large potential, these approaches have not yet been applied for the monitoring of fluvial processes. In a context where traditional methods often do not provide data with adequate temporal and spatial resolution, the use of dense arrays could allow the identification and tracking of different sources of river-induced seismic ground vibrations (e.g. turbulence and bedload transport), which would provide insight in river functioning and morphological evolution.
Here, we study the potential of dense seismic array monitoring by analysing data from a 4-month long field survey, which we conducted in summer 2019 along a 600-m long braided reach of the Séveraisse river (French Alps). We installed a network of 40 to 80 seismometers on both river banks, predominantly deployed in 4-seismometer subarrays, and we supplement these seismic observations with flow gauging measurements and time-lapse imagery covering the study area. We present a preliminary analysis that focuses on a high-flow event that occurred at the end of the melt season. During this event, we observe impulsive signals that are coherently detected over the array, and which we interpret as being associated with the bedload transport of clusters of coarse grains. Through phase-delay analysis we are able to locate episodes of motion at high temporal resolution and investigate their spatiotemporal dynamics with respect to river morphology and morphological changes observed from the time-lapse images. Our work demonstrates the unique capability of using dense seismic arrays to better understand the fluvial processes that play an important role in storing and transferring sediments in braided rivers.
How to cite: Piantini, M., Gimbert, F., Bakker, M., Recking, A., and Nanni, U.: Applying dense seismic array monitoring to locate fluvial processes during floods in a braided river reach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8800, https://doi.org/10.5194/egusphere-egu21-8800, 2021.
EGU21-4322 | vPICO presentations | GM2.8
Seismic quantification of river flow depth - from the flume to the fieldMaarten Bakker, Florent Gimbert, Michael P. Lamb, and Alain Recking
Seismic measurements are used to study various processes that shape the Alpine landscape, including rock falls, debris flows, bedload transport and turbulent water flow. Here, we focus on the seismic quantification of turbulent flow conditions which is particularly useful for the remote monitoring of channels that are inaccessible (e.g. subglacial conduits) and/or highly dynamic (e.g. actively braiding river reaches). We test a physically-based model (Gimbert et al., 2014) to quantify force spectra generated by turbulent flow in flume experiments performed by Lamb et al. (2017) and subsequently apply the model to estimate river flow depth from continuous seismic measurements in the field.
In the flume, we assess near-bed flow velocity spectra and resulting drag and lift force spectra experienced by particles (D=0.075-0.20 m) on the cobble bed for a wide range of channel gradients (S=0.004-0.3) and submergence levels (h/D50=1-9.6). These measurements are used to test our model, and to quantify wake (interaction) effects and fluid-dynamic admittance on force spectral amplitude. Based on the conservation of turbulent energy in the Kolmogorov inertial subrange, we predict lift and drag force spectra to within ±5 dB rel. N2/Hz (frequency ~10-25 Hz) of the measured values.
We apply the calibrated model to bank-side geophone measurements from an Alpine stream (Séveraisse River, France). Using locally-derived seismic parameters, riverbed particle-size distribution and bed roughness, we can invert for water depth over a range of flow conditions, including flows with bedload transport (bedload transport dominates the seismic signal at higher frequencies). This allows us to monitor changes in flow depth during the course of a high-magnitude flood (October 2019). During the falling limb, the inferred flow depths progressively deviate from independently made water level measurements, indicating local riverbed aggradation of approximately 0.5 m, which is in agreement with post-flood observations. Through insights in near-bed turbulent flow conditions and their seismic signature, we can study flow-bedload transport interactions and the effects of extreme flow events on river morphodynamics.
References
Gimbert, F., Tsai, V. C. & Lamb, M. P. (2014). A physical model for seismic noise generation by turbulent flow in rivers. Journal of Geophysical Research: Earth Surface, 119(10), 2209-2238. http://dx.doi.org/10.1002/2014JF003201
Lamb, M. P., Brun, F. & Fuller, B. M. (2017). Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport. Water Resources Research, 53(9), 7607-7629. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017WR020883
How to cite: Bakker, M., Gimbert, F., Lamb, M. P., and Recking, A.: Seismic quantification of river flow depth - from the flume to the field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4322, https://doi.org/10.5194/egusphere-egu21-4322, 2021.
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Seismic measurements are used to study various processes that shape the Alpine landscape, including rock falls, debris flows, bedload transport and turbulent water flow. Here, we focus on the seismic quantification of turbulent flow conditions which is particularly useful for the remote monitoring of channels that are inaccessible (e.g. subglacial conduits) and/or highly dynamic (e.g. actively braiding river reaches). We test a physically-based model (Gimbert et al., 2014) to quantify force spectra generated by turbulent flow in flume experiments performed by Lamb et al. (2017) and subsequently apply the model to estimate river flow depth from continuous seismic measurements in the field.
In the flume, we assess near-bed flow velocity spectra and resulting drag and lift force spectra experienced by particles (D=0.075-0.20 m) on the cobble bed for a wide range of channel gradients (S=0.004-0.3) and submergence levels (h/D50=1-9.6). These measurements are used to test our model, and to quantify wake (interaction) effects and fluid-dynamic admittance on force spectral amplitude. Based on the conservation of turbulent energy in the Kolmogorov inertial subrange, we predict lift and drag force spectra to within ±5 dB rel. N2/Hz (frequency ~10-25 Hz) of the measured values.
We apply the calibrated model to bank-side geophone measurements from an Alpine stream (Séveraisse River, France). Using locally-derived seismic parameters, riverbed particle-size distribution and bed roughness, we can invert for water depth over a range of flow conditions, including flows with bedload transport (bedload transport dominates the seismic signal at higher frequencies). This allows us to monitor changes in flow depth during the course of a high-magnitude flood (October 2019). During the falling limb, the inferred flow depths progressively deviate from independently made water level measurements, indicating local riverbed aggradation of approximately 0.5 m, which is in agreement with post-flood observations. Through insights in near-bed turbulent flow conditions and their seismic signature, we can study flow-bedload transport interactions and the effects of extreme flow events on river morphodynamics.
References
Gimbert, F., Tsai, V. C. & Lamb, M. P. (2014). A physical model for seismic noise generation by turbulent flow in rivers. Journal of Geophysical Research: Earth Surface, 119(10), 2209-2238. http://dx.doi.org/10.1002/2014JF003201
Lamb, M. P., Brun, F. & Fuller, B. M. (2017). Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport. Water Resources Research, 53(9), 7607-7629. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017WR020883
How to cite: Bakker, M., Gimbert, F., Lamb, M. P., and Recking, A.: Seismic quantification of river flow depth - from the flume to the field, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4322, https://doi.org/10.5194/egusphere-egu21-4322, 2021.
EGU21-4000 | vPICO presentations | GM2.8
Bedload export from an Alpine glacier inferred from seismic methodsDavide Mancini, Michael Dietze, Matthew Jenkin, Floreana Marie Miesen, Tom Müller, and Stuart Nicholas Lane
Environmental seismology is the discipline that uses ambient noise to detect and to measure geomorphic processes. The basic principle relies on the unique seismic signal, in terms of excited frequencies and amplitudes, generated by such processes which is then propagated and recorded to sensors (geophones). Recent developments of this technique are interesting for geomorphology because there is evidence that it can be used to study processes that are rare and difficult to measure, such as bedload transport in rivers. This is of particular importance for quantify bedload flux in proglacial streams. This paper focuses on using this method to quantify bedload export from an Alpine valley glacier. At present, there is no time-continuous measurement of bedload export in such settings. This is because objective measurement of bedload flux is a challenge task for both theoretical and practical reasons. Theoretically, the high variability of bedload transport means that measurements need to be continuous to identify when it happens and with which intensity. Practically, in order to know how to sample the signal through time, you need to know its variance a priori, which is commonly unsteady, and therefore needs to be sampled in order to know how to sample it. Direct manual sampling (e.g. with Helley-Smith samplers) have a serious disadvantage in this sense. Existing indirect methods (e.g. hydrophones and plate geophones) allow collection of continuous data but, at the same time, their installation can be difficult and expensive and they need to be carefully calibrated against manual samplings.
In the present study we used seismic data collected by out-of-stream geophones to infer bedload flux along an entire melt season (June - September) at the Glacier d’Otemma proglacial forefield, south-western Swiss Alps. Raw seismic data were inverted into sediment flux following the methodology developed in Dietze et al. (2019), to produce the first continuous dataset of bedload export from an Alpine glacier. The inversion model has been calibrated using statistical (i.e. sensitivity analysis) and direct (i.e. in situ active seismic survey) approaches.
How to cite: Mancini, D., Dietze, M., Jenkin, M., Miesen, F. M., Müller, T., and Lane, S. N.: Bedload export from an Alpine glacier inferred from seismic methods , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4000, https://doi.org/10.5194/egusphere-egu21-4000, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Environmental seismology is the discipline that uses ambient noise to detect and to measure geomorphic processes. The basic principle relies on the unique seismic signal, in terms of excited frequencies and amplitudes, generated by such processes which is then propagated and recorded to sensors (geophones). Recent developments of this technique are interesting for geomorphology because there is evidence that it can be used to study processes that are rare and difficult to measure, such as bedload transport in rivers. This is of particular importance for quantify bedload flux in proglacial streams. This paper focuses on using this method to quantify bedload export from an Alpine valley glacier. At present, there is no time-continuous measurement of bedload export in such settings. This is because objective measurement of bedload flux is a challenge task for both theoretical and practical reasons. Theoretically, the high variability of bedload transport means that measurements need to be continuous to identify when it happens and with which intensity. Practically, in order to know how to sample the signal through time, you need to know its variance a priori, which is commonly unsteady, and therefore needs to be sampled in order to know how to sample it. Direct manual sampling (e.g. with Helley-Smith samplers) have a serious disadvantage in this sense. Existing indirect methods (e.g. hydrophones and plate geophones) allow collection of continuous data but, at the same time, their installation can be difficult and expensive and they need to be carefully calibrated against manual samplings.
In the present study we used seismic data collected by out-of-stream geophones to infer bedload flux along an entire melt season (June - September) at the Glacier d’Otemma proglacial forefield, south-western Swiss Alps. Raw seismic data were inverted into sediment flux following the methodology developed in Dietze et al. (2019), to produce the first continuous dataset of bedload export from an Alpine glacier. The inversion model has been calibrated using statistical (i.e. sensitivity analysis) and direct (i.e. in situ active seismic survey) approaches.
How to cite: Mancini, D., Dietze, M., Jenkin, M., Miesen, F. M., Müller, T., and Lane, S. N.: Bedload export from an Alpine glacier inferred from seismic methods , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4000, https://doi.org/10.5194/egusphere-egu21-4000, 2021.
EGU21-9738 | vPICO presentations | GM2.8
Seismic characterization of bedload temporal variability in a proglacial Alpine streamVelio Coviello, Michael Engel, Anuschka Buter, Giulia Marchetti, Andrea Andreoli, Ricardo Carrillo, and Francesco Comiti
In mountainous areas, an increasing sediment delivery from glaciers to the channel network has been argued due to the ongoing global warming. However, quantitative estimations of sediment transport in such harsh environments are particularly challenging. A growing number of studies investigate the use of seismic techniques to perform indirect measurements of bedload transport. Seismic methods are attractive, as they can provide continuous recordings without the need of operators. Hydraulic structures equipped with geophone plates are established methods to monitor bedload in mountain rivers, but have the drawback of being expensive to install and to maintain. Seismometers installed along the channel banks have been successfully tested, but they are quite expensive too. Here, we present the application of a low-cost and easy-to-install geophone network to investigate the temporal variability of bedload transport at the snout of an Alpine debris-covered glacier.
Since 2017, we have been monitoring the upper sector of the Sulden/Solda river basin (South Tyrol, Eastern Italian Alps). The upper Sulden basin ranges in elevation between 2225 and 3905 m a.s.l., has a glacier extent of about 7 km² and is characterized by extended glacier forefields feeding the channel network with sediments. During the summer seasons, we deployed three single-component geophones (4.5 Hz) along the proglacial stream draining the Western Sulden glacier, which is heavily debris-covered. The geophones were installed at a distance of few meters from the channel, immediately downstream of the glacier snout. In 2018 and 2019, we performed monthly sampling campaigns of bedload by portable “Bunte” samplers to calibrate the seismic information. Water stage was measured using a submersible pressure transducer and pictures of the monitored area were taken every hour by an automatic camera. Meteorological data were measured at an automatic weather station located at 2825 m a.s.l., operated by the local hydrographic office. All of these complementary data were used to validate the analysis of the seismic signals.
Here, we analyze geophone data collected in the upper Sulden from 2018 to 2020 and we compare the time-frequency seismic information with air temperature and water discharge. Results show how (i) an array of single component geophones installed close to the flow path can detect both daily and longer period bedload fluctuations; (ii) geophone signal mirrors well the daily melt flow cycles, whereas its relationship with flow rate at a monthly scale varies positively, suggesting that bedload supply progressively increases during the season; (iii) there is a strong control exerted by air temperature on bedload transport, as the seismic energy reach maximum values during warm periods, while large variations of bedload rates cannot be explained in terms of differences in water discharge alone. Field evidence and direct bedload sampling campaigns performed after a glacier front collapse (August 2018) and after a small flood event (26 July 2019) confirmed such conclusions. These results prove how seismic techniques can provide precious insights into the dynamics of bedload export from Alpine glaciers.
How to cite: Coviello, V., Engel, M., Buter, A., Marchetti, G., Andreoli, A., Carrillo, R., and Comiti, F.: Seismic characterization of bedload temporal variability in a proglacial Alpine stream, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9738, https://doi.org/10.5194/egusphere-egu21-9738, 2021.
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In mountainous areas, an increasing sediment delivery from glaciers to the channel network has been argued due to the ongoing global warming. However, quantitative estimations of sediment transport in such harsh environments are particularly challenging. A growing number of studies investigate the use of seismic techniques to perform indirect measurements of bedload transport. Seismic methods are attractive, as they can provide continuous recordings without the need of operators. Hydraulic structures equipped with geophone plates are established methods to monitor bedload in mountain rivers, but have the drawback of being expensive to install and to maintain. Seismometers installed along the channel banks have been successfully tested, but they are quite expensive too. Here, we present the application of a low-cost and easy-to-install geophone network to investigate the temporal variability of bedload transport at the snout of an Alpine debris-covered glacier.
Since 2017, we have been monitoring the upper sector of the Sulden/Solda river basin (South Tyrol, Eastern Italian Alps). The upper Sulden basin ranges in elevation between 2225 and 3905 m a.s.l., has a glacier extent of about 7 km² and is characterized by extended glacier forefields feeding the channel network with sediments. During the summer seasons, we deployed three single-component geophones (4.5 Hz) along the proglacial stream draining the Western Sulden glacier, which is heavily debris-covered. The geophones were installed at a distance of few meters from the channel, immediately downstream of the glacier snout. In 2018 and 2019, we performed monthly sampling campaigns of bedload by portable “Bunte” samplers to calibrate the seismic information. Water stage was measured using a submersible pressure transducer and pictures of the monitored area were taken every hour by an automatic camera. Meteorological data were measured at an automatic weather station located at 2825 m a.s.l., operated by the local hydrographic office. All of these complementary data were used to validate the analysis of the seismic signals.
Here, we analyze geophone data collected in the upper Sulden from 2018 to 2020 and we compare the time-frequency seismic information with air temperature and water discharge. Results show how (i) an array of single component geophones installed close to the flow path can detect both daily and longer period bedload fluctuations; (ii) geophone signal mirrors well the daily melt flow cycles, whereas its relationship with flow rate at a monthly scale varies positively, suggesting that bedload supply progressively increases during the season; (iii) there is a strong control exerted by air temperature on bedload transport, as the seismic energy reach maximum values during warm periods, while large variations of bedload rates cannot be explained in terms of differences in water discharge alone. Field evidence and direct bedload sampling campaigns performed after a glacier front collapse (August 2018) and after a small flood event (26 July 2019) confirmed such conclusions. These results prove how seismic techniques can provide precious insights into the dynamics of bedload export from Alpine glaciers.
How to cite: Coviello, V., Engel, M., Buter, A., Marchetti, G., Andreoli, A., Carrillo, R., and Comiti, F.: Seismic characterization of bedload temporal variability in a proglacial Alpine stream, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9738, https://doi.org/10.5194/egusphere-egu21-9738, 2021.
EGU21-12637 | vPICO presentations | GM2.8
Effect of snowfalls on relative seismic velocity changes measured by ambient noise correlationAntoine Guillemot, Alec Van Herwijnen, Laurent Baillet, and Eric Larose
Seismic noise correlation is a broadly used method to monitor the subsurface, in order to detect physical processes into the surveyed medium such changes in rigidity, fluid injection or cracking (1). The influence of several environmental variables on measured seismic observables were studied, such as temperature, groundwater level fluctuations, and freeze-thawing cycles (2). In mountainous, cold temperate and polar sites, the presence of a snowcover can also affect relative seismic velocity changes (dV/V), but this relation is relatively poorly documented and ambiguous (3)(4). In this study, we analyzed raw seismic recordings from a snowy flat field site located above Davos (Switzerland), during one entire winter season (from December 2018 to June 2019). Our goal was to better understand the effect of snowfall and snowmelt events on dV/V measurements through both seismic and meteorological instrumentation.
We identified three snowfall events with a substantial response of dV/V measurements (drops of several percent between 15 and 25 Hz), suggesting a detectable change in elastic properties of the medium due to the additional fresh snow.
To better interpret the measurements, we used a physical model to compute frequency dependent changes in the Rayleigh wave velocity computed before and after the events. Elastic parameters of the ground subsurface were obtained from a seismic refraction survey, whereas snow cover properties were obtained from the snow cover model SNOWPACK. The decrease in dV/V due to a snowfall were well reproduced, with the same order of magnitude than observed values, confirming the importance of the effect of fresh and dry snow on seismic measurements.
We also observed a decrease in dV/V with snowmelt periods, but we were not able to reproduce those changes with our model. Overall, our results highlight the effect of the snowcover on seismic measurements, but more work is needed to accurately model this response, in particular for the presence of liquid water in the snowcover.
References
- (1) Larose, E., Carrière, S., Voisin, C., Bottelin, P., Baillet, L., Guéguen, P., Walter, F., et al. (2015) Environmental seismology: What can we learn on earth surface processes with ambient noise? Journal of Applied Geophysics, 116, 62–74. doi:10.1016/j.jappgeo.2015.02.001
- (2) Le Breton, M., Larose, É., Baillet, L., Bontemps, N. & Guillemot, A. (2020) Landslide Monitoring Using Seismic Ambient Noise Interferometry: Challenges and Applications. Earth-Science Reviews
- (3) Hotovec‐Ellis, A.J., Gomberg, J., Vidale, J.E. & Creager, K.C. (2014) A continuous record of intereruption velocity change at Mount St. Helens from coda wave interferometry. Journal of Geophysical Research: Solid Earth, 119, 2199–2214. doi:10.1002/2013JB010742
- (4) Wang, Q.-Y., Brenguier, F., Campillo, M., Lecointre, A., Takeda, T. & Aoki, Y. (2017) Seasonal Crustal Seismic Velocity Changes Throughout Japan. Journal of Geophysical Research: Solid Earth, 122, 7987–8002. doi:10.1002/2017JB014307
How to cite: Guillemot, A., Van Herwijnen, A., Baillet, L., and Larose, E.: Effect of snowfalls on relative seismic velocity changes measured by ambient noise correlation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12637, https://doi.org/10.5194/egusphere-egu21-12637, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Seismic noise correlation is a broadly used method to monitor the subsurface, in order to detect physical processes into the surveyed medium such changes in rigidity, fluid injection or cracking (1). The influence of several environmental variables on measured seismic observables were studied, such as temperature, groundwater level fluctuations, and freeze-thawing cycles (2). In mountainous, cold temperate and polar sites, the presence of a snowcover can also affect relative seismic velocity changes (dV/V), but this relation is relatively poorly documented and ambiguous (3)(4). In this study, we analyzed raw seismic recordings from a snowy flat field site located above Davos (Switzerland), during one entire winter season (from December 2018 to June 2019). Our goal was to better understand the effect of snowfall and snowmelt events on dV/V measurements through both seismic and meteorological instrumentation.
We identified three snowfall events with a substantial response of dV/V measurements (drops of several percent between 15 and 25 Hz), suggesting a detectable change in elastic properties of the medium due to the additional fresh snow.
To better interpret the measurements, we used a physical model to compute frequency dependent changes in the Rayleigh wave velocity computed before and after the events. Elastic parameters of the ground subsurface were obtained from a seismic refraction survey, whereas snow cover properties were obtained from the snow cover model SNOWPACK. The decrease in dV/V due to a snowfall were well reproduced, with the same order of magnitude than observed values, confirming the importance of the effect of fresh and dry snow on seismic measurements.
We also observed a decrease in dV/V with snowmelt periods, but we were not able to reproduce those changes with our model. Overall, our results highlight the effect of the snowcover on seismic measurements, but more work is needed to accurately model this response, in particular for the presence of liquid water in the snowcover.
References
- (1) Larose, E., Carrière, S., Voisin, C., Bottelin, P., Baillet, L., Guéguen, P., Walter, F., et al. (2015) Environmental seismology: What can we learn on earth surface processes with ambient noise? Journal of Applied Geophysics, 116, 62–74. doi:10.1016/j.jappgeo.2015.02.001
- (2) Le Breton, M., Larose, É., Baillet, L., Bontemps, N. & Guillemot, A. (2020) Landslide Monitoring Using Seismic Ambient Noise Interferometry: Challenges and Applications. Earth-Science Reviews
- (3) Hotovec‐Ellis, A.J., Gomberg, J., Vidale, J.E. & Creager, K.C. (2014) A continuous record of intereruption velocity change at Mount St. Helens from coda wave interferometry. Journal of Geophysical Research: Solid Earth, 119, 2199–2214. doi:10.1002/2013JB010742
- (4) Wang, Q.-Y., Brenguier, F., Campillo, M., Lecointre, A., Takeda, T. & Aoki, Y. (2017) Seasonal Crustal Seismic Velocity Changes Throughout Japan. Journal of Geophysical Research: Solid Earth, 122, 7987–8002. doi:10.1002/2017JB014307
How to cite: Guillemot, A., Van Herwijnen, A., Baillet, L., and Larose, E.: Effect of snowfalls on relative seismic velocity changes measured by ambient noise correlation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12637, https://doi.org/10.5194/egusphere-egu21-12637, 2021.
EGU21-9420 | vPICO presentations | GM2.8 | Highlight
Single-station seismic monitoring of permafrost on Mt. Zugspitze (Germany) over the past 15 yearsFabian Lindner and Joachim Wassermann
Permafrost thawing affects mountain slope stability and can trigger hazardous rock falls. As rising temperatures promote permafrost thawing, spatio-temporal monitoring of long-term and seasonal variations in the perennially frozen rock is therefore crucial in regions with high hazard potential. With various infrastructure in the summit area and population in the close vicinity, Mt. Zugspitze in the German/Austrian Alps is such a site and permafrost has been monitored with temperature logging in boreholes and lapse-time electrical resistivity tomography. Yet, these methods are expensive and laborious, and are limited in their spatial and/or temporal resolution.
Here, we analyze continuous seismic data from a single station deployed at an altitude of 2700 m a.s.l. in a research station, which is separated by roughly 250 m from the permafrost affected ridge of Mt. Zugspitze. Data are available since 2006 (with some gaps) and reveal high-frequency (>1 Hz) anthropogenic noise likely generated by the cable car stations at the summit. We calculate single-station cross-correlations between the different sensor components and investigate temporal coda wave changes by applying the recently introduced wavelet-based cross-spectrum method. This approach provides time series of the travel time relative to the reference stack as a function of frequency and lag time in the correlation functions. In the frequency and lag range of 1-10 Hz and 0.5-5 s respectively, we find various parts in the coda that show clear annual variations and an increasing trend in travel time over the past 15 years of consideration. Converting the travel time variations to seismic velocity variations (assuming homogeneous velocity changes affecting the whole mountain) results in seasonal velocity changes of up to a few percent and on the order of 0.1% decrease per year. Yet, estimated velocity variations do not scale linearly with lag time, which indicates that the medium changes are localized rather than uniform and that the absolute numbers need to be taken with caution. The annual velocity variations are anti-correlated with the temperature record from the summit but delayed by roughly one month.
The phasing of the annual seismic velocity change (relative to the temperature record) is in agreement with a previous study employing lapse-time electrical resistivity tomography. Furthermore, the decreasing trend in seismic velocity happens concurrently with an increasing trend in temperature. The results therefore suggest that the velocity changes are related to seasonal thaw and refreeze and permafrost degradation and thus highlight the potential of seismology for permafrost monitoring. By adding additional receivers and/or a fiber-optic cable for distributed acoustic sensing, hence increasing the spatial resolution, the presented method holds promise for lapse-time imaging of permafrost bodies with high spatio-temporal resolution from passive measurements.
How to cite: Lindner, F. and Wassermann, J.: Single-station seismic monitoring of permafrost on Mt. Zugspitze (Germany) over the past 15 years, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9420, https://doi.org/10.5194/egusphere-egu21-9420, 2021.
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Permafrost thawing affects mountain slope stability and can trigger hazardous rock falls. As rising temperatures promote permafrost thawing, spatio-temporal monitoring of long-term and seasonal variations in the perennially frozen rock is therefore crucial in regions with high hazard potential. With various infrastructure in the summit area and population in the close vicinity, Mt. Zugspitze in the German/Austrian Alps is such a site and permafrost has been monitored with temperature logging in boreholes and lapse-time electrical resistivity tomography. Yet, these methods are expensive and laborious, and are limited in their spatial and/or temporal resolution.
Here, we analyze continuous seismic data from a single station deployed at an altitude of 2700 m a.s.l. in a research station, which is separated by roughly 250 m from the permafrost affected ridge of Mt. Zugspitze. Data are available since 2006 (with some gaps) and reveal high-frequency (>1 Hz) anthropogenic noise likely generated by the cable car stations at the summit. We calculate single-station cross-correlations between the different sensor components and investigate temporal coda wave changes by applying the recently introduced wavelet-based cross-spectrum method. This approach provides time series of the travel time relative to the reference stack as a function of frequency and lag time in the correlation functions. In the frequency and lag range of 1-10 Hz and 0.5-5 s respectively, we find various parts in the coda that show clear annual variations and an increasing trend in travel time over the past 15 years of consideration. Converting the travel time variations to seismic velocity variations (assuming homogeneous velocity changes affecting the whole mountain) results in seasonal velocity changes of up to a few percent and on the order of 0.1% decrease per year. Yet, estimated velocity variations do not scale linearly with lag time, which indicates that the medium changes are localized rather than uniform and that the absolute numbers need to be taken with caution. The annual velocity variations are anti-correlated with the temperature record from the summit but delayed by roughly one month.
The phasing of the annual seismic velocity change (relative to the temperature record) is in agreement with a previous study employing lapse-time electrical resistivity tomography. Furthermore, the decreasing trend in seismic velocity happens concurrently with an increasing trend in temperature. The results therefore suggest that the velocity changes are related to seasonal thaw and refreeze and permafrost degradation and thus highlight the potential of seismology for permafrost monitoring. By adding additional receivers and/or a fiber-optic cable for distributed acoustic sensing, hence increasing the spatial resolution, the presented method holds promise for lapse-time imaging of permafrost bodies with high spatio-temporal resolution from passive measurements.
How to cite: Lindner, F. and Wassermann, J.: Single-station seismic monitoring of permafrost on Mt. Zugspitze (Germany) over the past 15 years, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9420, https://doi.org/10.5194/egusphere-egu21-9420, 2021.
EGU21-6476 | vPICO presentations | GM2.8
The glacier seismo-acoustic monitoring system in the Ukrainian Antarctic Station regionLiudmila Liashchuk, Oleksandr Liashchuk, Vadym Zhukovsky, Yevheniy Karyagin, Yuriy Andrushchenko, and Serhiy Dovbysh
Continuous long-term monitoring of the glacier is not an easy task. For the Woozle Hill ice cap near the Vernadsky Research Station, which is located on Galindez Island (Argentine Islands Archipelago), the task was solved by periodic ice sampling, GNSS measurements, photometry, and the use of GPR in the summer season. Some meteorological parameters were also periodically measured inside the ice cave in the glacier when conditions were favorable. In the past few years, GPR measurements have become more constant, and now they are carried out monthly. For continuous monitoring of the internal stresses of the glacier, we proposed using a network of seismoacoustic mini-arrays located along the perimeter of the glacier. Each array consists of four seismoacoustic sensors arranged in a cross. The length of the line between the extreme sensors reaches 100 meters. Proprietary sensors use an optical system for recording the seismic and infrasonic vibrations. The built-in microcontroller of each sensor transmits the digitized data (16 bit, 100(300) Hz) to the main unit based on the LattePanda, where preprocessing is performed. GPS receiver is also connected here for data synchronization. There is a Wi-Fi module for transmitting data to the collection station. Also, data can be transmitted to the collection station by wires installed on the cable-growth. Power is supplied 220 V through an adapter and a 12V battery. The sensors are waterproof, the rest of the equipment is assembled in a sealed waterproof box. There are three such arrays, in their turn, they form a regular triangle with a side of 700 meters, inside which there is a glacier. The processing consists of detecting signals in each array by the STA / LTA method, followed by correlation processing of the selected data fragment and calculating the azimuth to the signal, wave velocity, period, and amplitude. Also, the isolation of the coherent part of the low-intensity signal at the noise level can be carried out without preliminary STA / LTA detection, using algorithm F-statistics. Correlated interference is clipped in azimuth. The intersection of two or three azimuths allows you to locate the signal source. All parameters of detections with time stamps are recorded in the database and can be further processed using station meteorological data. The system began to be deployed around the glacier in January 2021. The presentation will present the first results of the deployed monitoring system.
How to cite: Liashchuk, L., Liashchuk, O., Zhukovsky, V., Karyagin, Y., Andrushchenko, Y., and Dovbysh, S.: The glacier seismo-acoustic monitoring system in the Ukrainian Antarctic Station region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6476, https://doi.org/10.5194/egusphere-egu21-6476, 2021.
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Continuous long-term monitoring of the glacier is not an easy task. For the Woozle Hill ice cap near the Vernadsky Research Station, which is located on Galindez Island (Argentine Islands Archipelago), the task was solved by periodic ice sampling, GNSS measurements, photometry, and the use of GPR in the summer season. Some meteorological parameters were also periodically measured inside the ice cave in the glacier when conditions were favorable. In the past few years, GPR measurements have become more constant, and now they are carried out monthly. For continuous monitoring of the internal stresses of the glacier, we proposed using a network of seismoacoustic mini-arrays located along the perimeter of the glacier. Each array consists of four seismoacoustic sensors arranged in a cross. The length of the line between the extreme sensors reaches 100 meters. Proprietary sensors use an optical system for recording the seismic and infrasonic vibrations. The built-in microcontroller of each sensor transmits the digitized data (16 bit, 100(300) Hz) to the main unit based on the LattePanda, where preprocessing is performed. GPS receiver is also connected here for data synchronization. There is a Wi-Fi module for transmitting data to the collection station. Also, data can be transmitted to the collection station by wires installed on the cable-growth. Power is supplied 220 V through an adapter and a 12V battery. The sensors are waterproof, the rest of the equipment is assembled in a sealed waterproof box. There are three such arrays, in their turn, they form a regular triangle with a side of 700 meters, inside which there is a glacier. The processing consists of detecting signals in each array by the STA / LTA method, followed by correlation processing of the selected data fragment and calculating the azimuth to the signal, wave velocity, period, and amplitude. Also, the isolation of the coherent part of the low-intensity signal at the noise level can be carried out without preliminary STA / LTA detection, using algorithm F-statistics. Correlated interference is clipped in azimuth. The intersection of two or three azimuths allows you to locate the signal source. All parameters of detections with time stamps are recorded in the database and can be further processed using station meteorological data. The system began to be deployed around the glacier in January 2021. The presentation will present the first results of the deployed monitoring system.
How to cite: Liashchuk, L., Liashchuk, O., Zhukovsky, V., Karyagin, Y., Andrushchenko, Y., and Dovbysh, S.: The glacier seismo-acoustic monitoring system in the Ukrainian Antarctic Station region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6476, https://doi.org/10.5194/egusphere-egu21-6476, 2021.
EGU21-7830 | vPICO presentations | GM2.8
Approach to study the seismicity in the Perunica Glacier, Livingston Island, AntarcticaGergana Georgieva, Liliya Dimitrova, and Dragomir Dragomirov
The seismicity caused by the movement of glaciers was discovered only 30-40 years ago, and it was initially assumed that only glaciers in Greenland create this type of seismicity. Today, a significant part of the earthquakes registered by the Antarctic seismic stations are of glacial origin. In recent years, scientists' interest in studying the seismic activity of glaciers and its relationship to various environmental factors has increased due to the response of the ice mass to climate change.
The interest of studying seismicity of Antarctica has increased in the last decade with installation of a growing number of seismic stations in the region.
In 2015, with the first installation of the LIVV seismic station, Bulgarian seismologists began studying the seismicity of the Perunika Glacier, located on Livingston Island, Antarctica. Between 2015 and 2018, seismic recordings were made only in the astral summer, and from January 2020 the seismic station was installed for year-round operation. The seismic station is located near the glacier.
In this study, an approach to analyze the ice generated events recorded during all working period of the LIVV station is presented. Depending on the source mechanism and therefore the different waveform shapes, several types of icequakes and earthquakes are distinguished.
Registered icequakes are more than 16000. Its duration varies between less than a second and more than a minute. A few events are several minutes long. We have noticed that from 2015 to 2020, the number of glacier events is increasing while its duration is decreasing.
Localization of the ice generated events with duration below 1 s is calculated. In the localization procedure, a velocity model developed for the area of the seismic station is applied. The produced icequake epicenters are grouped in several clusters within the Perunika glacier. The nature of these glacier events are still studying.
Another approach to study the seismic activity of the glacier is carried out by estimating the ambient seismic noise. Frequent and spectral distribution of the power of seismic noise is made over the seismic data recorded during all working periods. It is concluded that the noise sources in the periods around 0.5 s are linked to the dynamic processes in the Perunika Glacier. Some relationship between the change in the noise power in the 0.2-0.6s period band and tidal cycles has been found.
Acknowledgment: The presented study is supported by project: No 70.25-171/22.11.2019 “Study the activity of the Perunika glacier during year-round deployment” funded by the National Center for Polar Studies, Bulgaria.
How to cite: Georgieva, G., Dimitrova, L., and Dragomirov, D.: Approach to study the seismicity in the Perunica Glacier, Livingston Island, Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7830, https://doi.org/10.5194/egusphere-egu21-7830, 2021.
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The seismicity caused by the movement of glaciers was discovered only 30-40 years ago, and it was initially assumed that only glaciers in Greenland create this type of seismicity. Today, a significant part of the earthquakes registered by the Antarctic seismic stations are of glacial origin. In recent years, scientists' interest in studying the seismic activity of glaciers and its relationship to various environmental factors has increased due to the response of the ice mass to climate change.
The interest of studying seismicity of Antarctica has increased in the last decade with installation of a growing number of seismic stations in the region.
In 2015, with the first installation of the LIVV seismic station, Bulgarian seismologists began studying the seismicity of the Perunika Glacier, located on Livingston Island, Antarctica. Between 2015 and 2018, seismic recordings were made only in the astral summer, and from January 2020 the seismic station was installed for year-round operation. The seismic station is located near the glacier.
In this study, an approach to analyze the ice generated events recorded during all working period of the LIVV station is presented. Depending on the source mechanism and therefore the different waveform shapes, several types of icequakes and earthquakes are distinguished.
Registered icequakes are more than 16000. Its duration varies between less than a second and more than a minute. A few events are several minutes long. We have noticed that from 2015 to 2020, the number of glacier events is increasing while its duration is decreasing.
Localization of the ice generated events with duration below 1 s is calculated. In the localization procedure, a velocity model developed for the area of the seismic station is applied. The produced icequake epicenters are grouped in several clusters within the Perunika glacier. The nature of these glacier events are still studying.
Another approach to study the seismic activity of the glacier is carried out by estimating the ambient seismic noise. Frequent and spectral distribution of the power of seismic noise is made over the seismic data recorded during all working periods. It is concluded that the noise sources in the periods around 0.5 s are linked to the dynamic processes in the Perunika Glacier. Some relationship between the change in the noise power in the 0.2-0.6s period band and tidal cycles has been found.
Acknowledgment: The presented study is supported by project: No 70.25-171/22.11.2019 “Study the activity of the Perunika glacier during year-round deployment” funded by the National Center for Polar Studies, Bulgaria.
How to cite: Georgieva, G., Dimitrova, L., and Dragomirov, D.: Approach to study the seismicity in the Perunica Glacier, Livingston Island, Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7830, https://doi.org/10.5194/egusphere-egu21-7830, 2021.
GM2.9 – Dates, Rates and Bytes: Quantifying Geomorphological Processes and Landscape Dynamics
EGU21-3513 | vPICO presentations | GM2.9 | Highlight
Synoptic analysis of globally-distributed data sets of cosmogenic-nuclide exposure agesGreg Balco
This abstract describes a project to make large data sets of cosmogenic-nuclide measurements useable for synoptic global analysis of paleoclimate, glacier change, and landscape change. It is based on the 'ICE-D' (Informal Cosmogenic-nuclide Exposure-age Database), a transparent-middle-layer infrastructure for compiling and storing cosmogenic-nuclide measurements and generating internally consistent exposure-age data. The prototype implementation of this project focuses on a global data set of exposure ages from glacial deposits that are, potentially, useful for synoptic analysis of glacier change and paleoclimate. The aim is to address a number of messy data-management and analysis problems associated with cosmogenic-nuclide data, thus making it possible to apply unbiased, automated quantitative analysis to the entire globally-distributed data set. The presentation will highlight (i) examples of error-tolerant hypothesis testing using this approach; (ii) means of quantifying the importance of the details of cosmogenic-nuclide production-rate calculations to global paleoclimate inferences, and (iii) likewise, approaches to understanding the importance of geomorphic processes and landform evolution to global paleoclimate inferences drawn from exposure-dated landforms.
How to cite: Balco, G.: Synoptic analysis of globally-distributed data sets of cosmogenic-nuclide exposure ages, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3513, https://doi.org/10.5194/egusphere-egu21-3513, 2021.
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This abstract describes a project to make large data sets of cosmogenic-nuclide measurements useable for synoptic global analysis of paleoclimate, glacier change, and landscape change. It is based on the 'ICE-D' (Informal Cosmogenic-nuclide Exposure-age Database), a transparent-middle-layer infrastructure for compiling and storing cosmogenic-nuclide measurements and generating internally consistent exposure-age data. The prototype implementation of this project focuses on a global data set of exposure ages from glacial deposits that are, potentially, useful for synoptic analysis of glacier change and paleoclimate. The aim is to address a number of messy data-management and analysis problems associated with cosmogenic-nuclide data, thus making it possible to apply unbiased, automated quantitative analysis to the entire globally-distributed data set. The presentation will highlight (i) examples of error-tolerant hypothesis testing using this approach; (ii) means of quantifying the importance of the details of cosmogenic-nuclide production-rate calculations to global paleoclimate inferences, and (iii) likewise, approaches to understanding the importance of geomorphic processes and landform evolution to global paleoclimate inferences drawn from exposure-dated landforms.
How to cite: Balco, G.: Synoptic analysis of globally-distributed data sets of cosmogenic-nuclide exposure ages, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3513, https://doi.org/10.5194/egusphere-egu21-3513, 2021.
EGU21-12424 | vPICO presentations | GM2.9
Does lithology control post-orogenic topography and rock erodibility? Insights from Anti-Atlas of MoroccoRomano Clementucci, Paolo Ballato, Lionel Siame, Ahmed Yaaqoub, Abderrahim Essaifi, Laëtitia Leanni, Valery Guillou, and Claudio Faccenna
Rock erodibility plays a central role in setting topographic limits on relief development and is a key parameter in landscape evolution models. However, channel bed erodibility (K) is usually either fixed arbitrary or let varying over a wide range of values (10-12 – 10-3) because it is difficult to estimate. The topography of ancient orogens offers favourable conditions to quantify bedrock erodibility through the stream profile analysis, because the channel steepness is directly related to rock erodibility rather than rock uplift or climate variability.
The Anti-Atlas is a Variscan (Paleozoic) orogen of NW Africa that has not been drifted for long distances over the late Cenozoic and hence has not experienced an extended shift across climatic zones. Furthermore, it is characterized by a well preserved uplifted relict landscape with rather uniform erosion rates since at least the last 120 - 100 Ma. This specific configuration allows studying in detail landscape erosional dynamics and erodibility.
Here, we combine geomorphic analysis of stream profiles with in situ-produced cosmogenic concentrations (10Be) in river sediments, to decipher the surface evolution of the AntiAtlas and the adjacent Siroua Massif. In the Anti-Atlas, the basin-wide denudation rates determined for the relictal part of the landscape range between 5 and 20 m Ma-1, consistent with rates estimated from the volume of volcanics eroded from the Siroua Massif during the last 12 - 10 Ma (10 to 20 m Ma-1). The close agreement of short- and long-term erosion rates suggests a steady state landscape.
Our results demonstrate the main role of rock-type on sustaining post-orogenic landscape. Specifically, we find a striking correlation between erosion rates and normalized channel steepness per different rock-types. This allows estimating the erodibility within a narrower range of values (10-7 - 10-4) as a function of the reference concavity values of the river network.
How to cite: Clementucci, R., Ballato, P., Siame, L., Yaaqoub, A., Essaifi, A., Leanni, L., Guillou, V., and Faccenna, C.: Does lithology control post-orogenic topography and rock erodibility? Insights from Anti-Atlas of Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12424, https://doi.org/10.5194/egusphere-egu21-12424, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Rock erodibility plays a central role in setting topographic limits on relief development and is a key parameter in landscape evolution models. However, channel bed erodibility (K) is usually either fixed arbitrary or let varying over a wide range of values (10-12 – 10-3) because it is difficult to estimate. The topography of ancient orogens offers favourable conditions to quantify bedrock erodibility through the stream profile analysis, because the channel steepness is directly related to rock erodibility rather than rock uplift or climate variability.
The Anti-Atlas is a Variscan (Paleozoic) orogen of NW Africa that has not been drifted for long distances over the late Cenozoic and hence has not experienced an extended shift across climatic zones. Furthermore, it is characterized by a well preserved uplifted relict landscape with rather uniform erosion rates since at least the last 120 - 100 Ma. This specific configuration allows studying in detail landscape erosional dynamics and erodibility.
Here, we combine geomorphic analysis of stream profiles with in situ-produced cosmogenic concentrations (10Be) in river sediments, to decipher the surface evolution of the AntiAtlas and the adjacent Siroua Massif. In the Anti-Atlas, the basin-wide denudation rates determined for the relictal part of the landscape range between 5 and 20 m Ma-1, consistent with rates estimated from the volume of volcanics eroded from the Siroua Massif during the last 12 - 10 Ma (10 to 20 m Ma-1). The close agreement of short- and long-term erosion rates suggests a steady state landscape.
Our results demonstrate the main role of rock-type on sustaining post-orogenic landscape. Specifically, we find a striking correlation between erosion rates and normalized channel steepness per different rock-types. This allows estimating the erodibility within a narrower range of values (10-7 - 10-4) as a function of the reference concavity values of the river network.
How to cite: Clementucci, R., Ballato, P., Siame, L., Yaaqoub, A., Essaifi, A., Leanni, L., Guillou, V., and Faccenna, C.: Does lithology control post-orogenic topography and rock erodibility? Insights from Anti-Atlas of Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12424, https://doi.org/10.5194/egusphere-egu21-12424, 2021.
EGU21-6651 | vPICO presentations | GM2.9
Insight into the sediment dynamics of a high-impact low-frequency mass movement event using single-grain feldspar luminescence in the Pokhara valley, NepalAnna-Maartje de Boer, Wolfgang Schwanghart, Jürgen Mey, Jakob Wallinga, Basanta Raj Adhikari, and Tony Reimann
Mass movements play an important role in landscape evolution of high mountain areas such as the Himalayas. Yet, establishing numerical age control and reconstructing transport dynamics of past events is challenging. To fill this research gap, we investigated the potential of Optically Stimulated Luminescence (OSL) dating and tracing methods. OSL dating analyses of Himalayan sediments is extremely challenging due to two main reasons: i) the OSL sensitivity of quartz, typically the mineral of choice for dating sediments younger than 100 ka, is poor, and ii) highly turbid conditions during mass movement transport hamper sufficient OSL signal resetting prior to deposition which eventually results in age overestimation. In this study, we aim to bring OSL dating to the test in an extremely challenging environment. First, we assess the applicability of single-grain feldspar dating of mass movement deposits in the Pokhara valley, Nepal. Second, we exploit the poor bleaching mechanisms to get insight into the sediment dynamics of this paleo-mass movement through bleaching proxies. The Pokhara valley is a unique setting for our case-study, considering the availability of an extensive independent radiocarbon dataset (Schwanghart et al., 2016) as a geochronological benchmark.
Single-grain infrared stimulated luminescence signals were measured at 50°C (IRSL50) and post-infrared infrared stimulated luminescence signals at 150°C (pIRIR-150). As expected, results show that the IRSL50 signal is better bleached than the pIRIR150 signal. A bootstrapped Minimum Age Model (bMAM) is applied to retrieve the youngest subpopulation to estimate the palaeodose. However, burial ages calculated based on this palaeodose overestimate the radiocarbon ages by an average factor of ~8 (IRSL50) and ~35 (pIRIR150). This shows that dating of the Pokhara Formation with our single-grain approach was not successful. Large inheritances in combination with the scatter in the single-grain dose distributions show that the sediments have been transported prior to deposition under extreme limited light exposure which corresponds well with the highly turbid nature of the sediment laden flood and debris flows that emplaced the Pokhara Formation.
To investigate the sediment transport dynamics in more detail we studied three bleaching proxies: the percentage of grains in saturation (2D0 criteria), percentage of well-bleached grains (2σ range of bMAM-De) and the overdispersion (OD). Neither of the three bleaching proxies indicate a spatial relationship with run-out distances of the mass movement deposits. We interpret this as virtual absence of bleaching during transport, which reflects the catastrophic nature of the event. While single-grain feldspar dating did not provide reliable burial ages of the Pokhara mass movement deposits, our approach has great potential to provide insight in sediment transport dynamics of high-impact low-frequency mass movement events in mountainous region.
References
Schwanghart, W., Bernhardt, A., Stolle, A., Hoelzmann, P., Adhikari, B. R., Andermann, C., ... & Korup, O. (2016). Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya. Science, 351(6269), 147-150.
How to cite: de Boer, A.-M., Schwanghart, W., Mey, J., Wallinga, J., Raj Adhikari, B., and Reimann, T.: Insight into the sediment dynamics of a high-impact low-frequency mass movement event using single-grain feldspar luminescence in the Pokhara valley, Nepal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6651, https://doi.org/10.5194/egusphere-egu21-6651, 2021.
Mass movements play an important role in landscape evolution of high mountain areas such as the Himalayas. Yet, establishing numerical age control and reconstructing transport dynamics of past events is challenging. To fill this research gap, we investigated the potential of Optically Stimulated Luminescence (OSL) dating and tracing methods. OSL dating analyses of Himalayan sediments is extremely challenging due to two main reasons: i) the OSL sensitivity of quartz, typically the mineral of choice for dating sediments younger than 100 ka, is poor, and ii) highly turbid conditions during mass movement transport hamper sufficient OSL signal resetting prior to deposition which eventually results in age overestimation. In this study, we aim to bring OSL dating to the test in an extremely challenging environment. First, we assess the applicability of single-grain feldspar dating of mass movement deposits in the Pokhara valley, Nepal. Second, we exploit the poor bleaching mechanisms to get insight into the sediment dynamics of this paleo-mass movement through bleaching proxies. The Pokhara valley is a unique setting for our case-study, considering the availability of an extensive independent radiocarbon dataset (Schwanghart et al., 2016) as a geochronological benchmark.
Single-grain infrared stimulated luminescence signals were measured at 50°C (IRSL50) and post-infrared infrared stimulated luminescence signals at 150°C (pIRIR-150). As expected, results show that the IRSL50 signal is better bleached than the pIRIR150 signal. A bootstrapped Minimum Age Model (bMAM) is applied to retrieve the youngest subpopulation to estimate the palaeodose. However, burial ages calculated based on this palaeodose overestimate the radiocarbon ages by an average factor of ~8 (IRSL50) and ~35 (pIRIR150). This shows that dating of the Pokhara Formation with our single-grain approach was not successful. Large inheritances in combination with the scatter in the single-grain dose distributions show that the sediments have been transported prior to deposition under extreme limited light exposure which corresponds well with the highly turbid nature of the sediment laden flood and debris flows that emplaced the Pokhara Formation.
To investigate the sediment transport dynamics in more detail we studied three bleaching proxies: the percentage of grains in saturation (2D0 criteria), percentage of well-bleached grains (2σ range of bMAM-De) and the overdispersion (OD). Neither of the three bleaching proxies indicate a spatial relationship with run-out distances of the mass movement deposits. We interpret this as virtual absence of bleaching during transport, which reflects the catastrophic nature of the event. While single-grain feldspar dating did not provide reliable burial ages of the Pokhara mass movement deposits, our approach has great potential to provide insight in sediment transport dynamics of high-impact low-frequency mass movement events in mountainous region.
References
Schwanghart, W., Bernhardt, A., Stolle, A., Hoelzmann, P., Adhikari, B. R., Andermann, C., ... & Korup, O. (2016). Repeated catastrophic valley infill following medieval earthquakes in the Nepal Himalaya. Science, 351(6269), 147-150.
How to cite: de Boer, A.-M., Schwanghart, W., Mey, J., Wallinga, J., Raj Adhikari, B., and Reimann, T.: Insight into the sediment dynamics of a high-impact low-frequency mass movement event using single-grain feldspar luminescence in the Pokhara valley, Nepal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6651, https://doi.org/10.5194/egusphere-egu21-6651, 2021.
EGU21-289 | vPICO presentations | GM2.9
Un-mixing the effect of post-depositional tillage turbation on OSL age-depth data through measurements and numerical simulationsMarijn van der Meij, Arnaud Temme, Mark Verhoeven, and Tony Reimann
Agricultural systems are subject to severe land degradation, because anthropogenic erosion processes, such as tillage erosion, substantially increase erosion rates compared to natural settings. Optically Stimulated Luminescence (OSL) dating is often used to measure the age of depositional layers to quantify rates of landscape change. OSL dating in agricultural systems is however challenging, because the deposits are reworked in the tillage layer even long after their moment of deposition. This post-depositional mixing resets the built-up luminescence signal, which causes an offset between the apparent OSL ages and the actual deposition ages.
In this study we illustrate the effect of post-depositional mixing on geochronological OSL age-depth data from northeastern Germany and we developed tools to un-mix depositional and post-depositional ages. We analyzed 32 OSL samples from five locations in a kettle hole to reconstruct spatial and temporal deposition patterns. We were able to correct our chronologies for post-depositional mixing by tillage by accounting for (pre-)historical plough regimes. Next to these empirical data, we also modified a Soil-Landscape Evolution Model called Lorica to numerically simulate the effect of post-depositional mixing on depositional ages. This combination of measurements and simulations enabled us to constrain the spatial and temporal effects of post-depositional mixing on OSL age-depth data more accurately. This is an important step towards getting a better grip on the dynamics of agricultural landscapes including the associated dates and rates.
How to cite: van der Meij, M., Temme, A., Verhoeven, M., and Reimann, T.: Un-mixing the effect of post-depositional tillage turbation on OSL age-depth data through measurements and numerical simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-289, https://doi.org/10.5194/egusphere-egu21-289, 2021.
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Agricultural systems are subject to severe land degradation, because anthropogenic erosion processes, such as tillage erosion, substantially increase erosion rates compared to natural settings. Optically Stimulated Luminescence (OSL) dating is often used to measure the age of depositional layers to quantify rates of landscape change. OSL dating in agricultural systems is however challenging, because the deposits are reworked in the tillage layer even long after their moment of deposition. This post-depositional mixing resets the built-up luminescence signal, which causes an offset between the apparent OSL ages and the actual deposition ages.
In this study we illustrate the effect of post-depositional mixing on geochronological OSL age-depth data from northeastern Germany and we developed tools to un-mix depositional and post-depositional ages. We analyzed 32 OSL samples from five locations in a kettle hole to reconstruct spatial and temporal deposition patterns. We were able to correct our chronologies for post-depositional mixing by tillage by accounting for (pre-)historical plough regimes. Next to these empirical data, we also modified a Soil-Landscape Evolution Model called Lorica to numerically simulate the effect of post-depositional mixing on depositional ages. This combination of measurements and simulations enabled us to constrain the spatial and temporal effects of post-depositional mixing on OSL age-depth data more accurately. This is an important step towards getting a better grip on the dynamics of agricultural landscapes including the associated dates and rates.
How to cite: van der Meij, M., Temme, A., Verhoeven, M., and Reimann, T.: Un-mixing the effect of post-depositional tillage turbation on OSL age-depth data through measurements and numerical simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-289, https://doi.org/10.5194/egusphere-egu21-289, 2021.
EGU21-1721 | vPICO presentations | GM2.9
Luminescence sensitivity of German loess: indicators of source variabilityKathryn Fitzsimmons, Peter Fischer, Zoran Peric, Maike Nowatzki, Susanne Lindauer, and Andreas Vött
Loess – a homogeneous, predominantly silt-sized aeolian sediment – has long been recognised as a valuable terrestrial record of past environmental conditions. Loess deposits drape some 10% of the Earth’s land surface, accumulating almost continuously in some regions. Most aeolian dust is thought not to travel far, often deriving from fine-grained material transported by rivers from glaciated regions. The provenance of loess sediment is inferred from the trajectories of atmospheric circulation systems and how these may have changed in intensity and influence over a region through time. The most frequently used techniques for correlating aeolian dust deposits with likely source areas, including bulk geochemistry, age distributions of detrital zircons, and Sr-Nd isotope ratios in clays, remain limited in the information they may provide about loess provenance. Since loess is dominated by silicate minerals – namely, quartz and feldspars – it is advantageous to explore their potential as indicators of source changes within loess-paleosol sequences (LPS). Increasingly, researchers have been exploring variations in the luminescence characteristics of sedimentary quartz and feldspar as possible provenance tools. Of a range of approaches so far applied, luminescence sensitivity is the quickest to measure and provides a means to rapidly assess potential changes in sediment source down LPS.
Luminescence sensitivity – the signal intensity per absorbed radiation dose – arises from the efficiency of charge traffic between traps and luminescence centres within a crystalline framework. In a sedimentary context, sensitivity is the product of interplay between source lithology and the history of the mineral in question. Consequently, shifts in sediment provenance may be observed through variations in luminescence sensitivity down LPS. Despite the presence of thick loess deposits across Europe, however, this approach has yet to be tested on this continent.
Here we undertake an empirical investigation of the luminescence sensitivity characteristics of quartz and feldspar from different grain-size fractions at the Schwalbenberg LPS in the German Rhine valley. The Schwalbenberg LPS has recently been shown to respond to variability in Atlantic-driven climate oscillations in fine detail; it follows, therefore, that changes in source will likely be recorded in its sediments. We test the potential of luminescence sensitivity as an indicator of changes in sediment source through time, comparing samples from a 30 m core (REM3) spanning the last full glacial cycle, with samples of oxygen isotope stage (OIS) 3-2 age exposed within a c. 6 m profile on the southern margins of the deposit. The temporal overlap of the two localities during OIS3 enables comparison of luminescence characteristics with respect to possible provenance during that timeframe; we find an inverse relationship between quartz and feldspar sensitivity, as well as variability in sensitivity between different quartz grain sizes. There is some indication that feldspar sensitivity increases during periods of soil formation down the core. These observations may suggest source variability over millennial timescales.
How to cite: Fitzsimmons, K., Fischer, P., Peric, Z., Nowatzki, M., Lindauer, S., and Vött, A.: Luminescence sensitivity of German loess: indicators of source variability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1721, https://doi.org/10.5194/egusphere-egu21-1721, 2021.
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Loess – a homogeneous, predominantly silt-sized aeolian sediment – has long been recognised as a valuable terrestrial record of past environmental conditions. Loess deposits drape some 10% of the Earth’s land surface, accumulating almost continuously in some regions. Most aeolian dust is thought not to travel far, often deriving from fine-grained material transported by rivers from glaciated regions. The provenance of loess sediment is inferred from the trajectories of atmospheric circulation systems and how these may have changed in intensity and influence over a region through time. The most frequently used techniques for correlating aeolian dust deposits with likely source areas, including bulk geochemistry, age distributions of detrital zircons, and Sr-Nd isotope ratios in clays, remain limited in the information they may provide about loess provenance. Since loess is dominated by silicate minerals – namely, quartz and feldspars – it is advantageous to explore their potential as indicators of source changes within loess-paleosol sequences (LPS). Increasingly, researchers have been exploring variations in the luminescence characteristics of sedimentary quartz and feldspar as possible provenance tools. Of a range of approaches so far applied, luminescence sensitivity is the quickest to measure and provides a means to rapidly assess potential changes in sediment source down LPS.
Luminescence sensitivity – the signal intensity per absorbed radiation dose – arises from the efficiency of charge traffic between traps and luminescence centres within a crystalline framework. In a sedimentary context, sensitivity is the product of interplay between source lithology and the history of the mineral in question. Consequently, shifts in sediment provenance may be observed through variations in luminescence sensitivity down LPS. Despite the presence of thick loess deposits across Europe, however, this approach has yet to be tested on this continent.
Here we undertake an empirical investigation of the luminescence sensitivity characteristics of quartz and feldspar from different grain-size fractions at the Schwalbenberg LPS in the German Rhine valley. The Schwalbenberg LPS has recently been shown to respond to variability in Atlantic-driven climate oscillations in fine detail; it follows, therefore, that changes in source will likely be recorded in its sediments. We test the potential of luminescence sensitivity as an indicator of changes in sediment source through time, comparing samples from a 30 m core (REM3) spanning the last full glacial cycle, with samples of oxygen isotope stage (OIS) 3-2 age exposed within a c. 6 m profile on the southern margins of the deposit. The temporal overlap of the two localities during OIS3 enables comparison of luminescence characteristics with respect to possible provenance during that timeframe; we find an inverse relationship between quartz and feldspar sensitivity, as well as variability in sensitivity between different quartz grain sizes. There is some indication that feldspar sensitivity increases during periods of soil formation down the core. These observations may suggest source variability over millennial timescales.
How to cite: Fitzsimmons, K., Fischer, P., Peric, Z., Nowatzki, M., Lindauer, S., and Vött, A.: Luminescence sensitivity of German loess: indicators of source variability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1721, https://doi.org/10.5194/egusphere-egu21-1721, 2021.
EGU21-4514 | vPICO presentations | GM2.9
Imprint of landscape dynamics in the luminescence signal of fluvial sediments (Rangitikei River, NZ)Anne Guyez, Stephane Bonnet, Tony Reimann, Sébastien Carretier, and Jakob Wallinga
Enlightenment of sediments pathways and storage patterns within river systems is critical to apprehend sediment transfer at the Earth’s surface and landscape response to tectonics and climate. Because direct tracing methods (painted, fluorescent or magnetic sediments) are of limited use in terms of their analytical resolution in time and space, alternative physico-chemical methods suitable for larger spatial-temporal scales have been developed (e.g. cosmogenic isotope, detrital thermochronology, isotopic geochemistry, etc). The study of the natural luminescence of sediment particles is emerging for this purpose and seems promising for providing new information complementary to existing methods. This method is based on the quartz/feldspar grains ability to store energy while buried below the Earth’s surface and to emit lumen with light exposure. Some recent studies have used this property to solve geomorphological questions regarding particle fluxes in soil or fluvial systems (Reimann et al., 2017; Sawakuchi et al., 2018) and to quantify rock exhumation (e.g. Herman et al., 2010). Here, we present an experimental testing of an innovative single-grain luminescence-based approach on feldspars. Focusing alongstream the Rangitikei River (RR), New Zealand, we carried out analysis on both modern sediment and Holocene terraces deposits.
We based our analysis on two complementarians proxies, the paleodose estimated using the bootstrapped minimum age model (Cunningham and Wallinga, 2012) and the percentage of grains eroded from bedrock and re-deposited in the river without signal resetting, i.e. saturated grains. We document changes in the luminescence signature of fluvial sediments while the RR evolves in response to uplift and climate change; from a late Pleistocene-early Holocene braided system to a Holocene incising canyon that subsequently widen. This allows us to appraise temporal changes in the alongstream contribution of canyon flanks landsides to sediment supply to the river. Overall, we show that distinct landscape dynamics gives distinct luminescence signatures.
How to cite: Guyez, A., Bonnet, S., Reimann, T., Carretier, S., and Wallinga, J.: Imprint of landscape dynamics in the luminescence signal of fluvial sediments (Rangitikei River, NZ), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4514, https://doi.org/10.5194/egusphere-egu21-4514, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Enlightenment of sediments pathways and storage patterns within river systems is critical to apprehend sediment transfer at the Earth’s surface and landscape response to tectonics and climate. Because direct tracing methods (painted, fluorescent or magnetic sediments) are of limited use in terms of their analytical resolution in time and space, alternative physico-chemical methods suitable for larger spatial-temporal scales have been developed (e.g. cosmogenic isotope, detrital thermochronology, isotopic geochemistry, etc). The study of the natural luminescence of sediment particles is emerging for this purpose and seems promising for providing new information complementary to existing methods. This method is based on the quartz/feldspar grains ability to store energy while buried below the Earth’s surface and to emit lumen with light exposure. Some recent studies have used this property to solve geomorphological questions regarding particle fluxes in soil or fluvial systems (Reimann et al., 2017; Sawakuchi et al., 2018) and to quantify rock exhumation (e.g. Herman et al., 2010). Here, we present an experimental testing of an innovative single-grain luminescence-based approach on feldspars. Focusing alongstream the Rangitikei River (RR), New Zealand, we carried out analysis on both modern sediment and Holocene terraces deposits.
We based our analysis on two complementarians proxies, the paleodose estimated using the bootstrapped minimum age model (Cunningham and Wallinga, 2012) and the percentage of grains eroded from bedrock and re-deposited in the river without signal resetting, i.e. saturated grains. We document changes in the luminescence signature of fluvial sediments while the RR evolves in response to uplift and climate change; from a late Pleistocene-early Holocene braided system to a Holocene incising canyon that subsequently widen. This allows us to appraise temporal changes in the alongstream contribution of canyon flanks landsides to sediment supply to the river. Overall, we show that distinct landscape dynamics gives distinct luminescence signatures.
How to cite: Guyez, A., Bonnet, S., Reimann, T., Carretier, S., and Wallinga, J.: Imprint of landscape dynamics in the luminescence signal of fluvial sediments (Rangitikei River, NZ), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4514, https://doi.org/10.5194/egusphere-egu21-4514, 2021.
EGU21-6721 | vPICO presentations | GM2.9
Reconstructing aeolian transport processes using luminescence and electron spin resonance characteristics of quartz grains: A case study from the Ili basin, SE KazakhstanAditi Krishna Dave, Alida Timar-Gabor, Johan De Grave, Dimitri Vandenberghe, Saida Nigmatova, and Kathryn E. Fitzsimmons
The entrainment, transport and deposition of wind-blown (aeolian) sediments is vital to our understanding of the links between the resulting depositional landforms and climate dynamics in a region. The nature of aeolian processes has varied over Quaternary timescales, and is dependent on changing sediment supply, existing topography and climatic parameters such as wind strength and moisture availability, at local to supra-regional spatial scales [1]. Hence, in order to understand long-term interactions between aeolian-dominated landscapes and climate, there is a need to investigate the mechanisms driving wind-blown processes. In this context, the Ili basin of southeast Kazakhstan, with its extensive piedmont loess deposits and desert dunefields, provides an excellent case study for investigating aeolian earth-surface processes and their links to climate.
Quartz is one of the most abundant and robust minerals on the earth’s surface. The lattice defects and impurities in quartz provides a potential provenancing tool, which can be probed by luminescence and electron spin resonance (ESR) techniques [2,3]. Here we investigate the luminescence sensitivity and ESR signature of various paramagnetic centres (E’, peroxy and [AlO4]0) in quartz of different grain sizes from Pleistocene loess, as well as from surface sediments and rocks collected from various depositional and potential source contexts across the Ili basin. We observe significant difference between fine and coarse grain quartz samples from various depositional settings which highlights the difference in entrainment and transport processes for different grain sizes. Our observations allow us to assess the validity of hypothesised aeolian depositional models as well as the more recent back-trajectory models for dust transport [1] in the region, thus, establishing an empirical understanding of modern aeolian earth-surface processes. Based on these results, we extend our understanding of modern processes to investigate past aeolian dynamics. Our data provides first empirical insights into the origin of fine-grained sediments along the piedmont and what these can tell us about climate dynamics in Central Asia.
References:
[1] Fitzsimmons, K.E., Nowatski, M., Dave, A.K., Harder, H., 2019. Intersections between wind regimes, topography and sediment supply: perspectives from aeolian landforms in Central Asia. Palaeogeography, Palaeoclimatology, Palaeoecology 540, 109-531.
[2] Gray., H.J., Jain, M., Sawakuchi, A.O, Mahan, S.A., Tucker, G.E. 2019. Luminescence as a Sediment Tracer and Provenance Tool. Reviews of Geophysics 57 (3), 987-1017
[3] Toyoda, S., Nagashima, K., Yamamoto, Y., 2016. ESR signals in quartz: Applications to provenance research – A review. Quaternary International 397, 258-266.
How to cite: Dave, A. K., Timar-Gabor, A., De Grave, J., Vandenberghe, D., Nigmatova, S., and Fitzsimmons, K. E.: Reconstructing aeolian transport processes using luminescence and electron spin resonance characteristics of quartz grains: A case study from the Ili basin, SE Kazakhstan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6721, https://doi.org/10.5194/egusphere-egu21-6721, 2021.
The entrainment, transport and deposition of wind-blown (aeolian) sediments is vital to our understanding of the links between the resulting depositional landforms and climate dynamics in a region. The nature of aeolian processes has varied over Quaternary timescales, and is dependent on changing sediment supply, existing topography and climatic parameters such as wind strength and moisture availability, at local to supra-regional spatial scales [1]. Hence, in order to understand long-term interactions between aeolian-dominated landscapes and climate, there is a need to investigate the mechanisms driving wind-blown processes. In this context, the Ili basin of southeast Kazakhstan, with its extensive piedmont loess deposits and desert dunefields, provides an excellent case study for investigating aeolian earth-surface processes and their links to climate.
Quartz is one of the most abundant and robust minerals on the earth’s surface. The lattice defects and impurities in quartz provides a potential provenancing tool, which can be probed by luminescence and electron spin resonance (ESR) techniques [2,3]. Here we investigate the luminescence sensitivity and ESR signature of various paramagnetic centres (E’, peroxy and [AlO4]0) in quartz of different grain sizes from Pleistocene loess, as well as from surface sediments and rocks collected from various depositional and potential source contexts across the Ili basin. We observe significant difference between fine and coarse grain quartz samples from various depositional settings which highlights the difference in entrainment and transport processes for different grain sizes. Our observations allow us to assess the validity of hypothesised aeolian depositional models as well as the more recent back-trajectory models for dust transport [1] in the region, thus, establishing an empirical understanding of modern aeolian earth-surface processes. Based on these results, we extend our understanding of modern processes to investigate past aeolian dynamics. Our data provides first empirical insights into the origin of fine-grained sediments along the piedmont and what these can tell us about climate dynamics in Central Asia.
References:
[1] Fitzsimmons, K.E., Nowatski, M., Dave, A.K., Harder, H., 2019. Intersections between wind regimes, topography and sediment supply: perspectives from aeolian landforms in Central Asia. Palaeogeography, Palaeoclimatology, Palaeoecology 540, 109-531.
[2] Gray., H.J., Jain, M., Sawakuchi, A.O, Mahan, S.A., Tucker, G.E. 2019. Luminescence as a Sediment Tracer and Provenance Tool. Reviews of Geophysics 57 (3), 987-1017
[3] Toyoda, S., Nagashima, K., Yamamoto, Y., 2016. ESR signals in quartz: Applications to provenance research – A review. Quaternary International 397, 258-266.
How to cite: Dave, A. K., Timar-Gabor, A., De Grave, J., Vandenberghe, D., Nigmatova, S., and Fitzsimmons, K. E.: Reconstructing aeolian transport processes using luminescence and electron spin resonance characteristics of quartz grains: A case study from the Ili basin, SE Kazakhstan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6721, https://doi.org/10.5194/egusphere-egu21-6721, 2021.
EGU21-1714 | vPICO presentations | GM2.9
Investigations on different measurement protocols of E` paramagnetic defect centres in quartz for provenance studiesAlida Timar-Gabor, Aditi Dave, Zuzanna Kabacińska, and Kathryn Fitzsimmons
The sediment-routing concept [1] aims to integrate tectonic fluxes and climatically driven erosion, an approach that is at the core of modern studies into Earth-surface processes. The concept relies on the potential to track individual mineral grains from source to sink. Provenance studies are instrumental in this respect; until recently, almost all of these have focussed on accessory minerals. By contrast, the durability and abundance of quartz ensures that parent rocks containing quartz are represented by detrital quartz in their daughter sediment. Even the purest quartz crystal contains a vast number of point defects, which may be either intrinsic or due to impurities. Some of these defects remain unchanged under ionising radiation bombardment by natural environmental radioactivity, while others are transformed, generally in the form of charge trapping. Based on the dynamics of some of these radiation-sensitive defects under irradiation, quartz is frequently used for dating by luminescence or electron spin resonance (ESR). Another, less explored, application of these defects is the fingerprinting of sediment sources. For provenance applications to be successful, sedimentary quartz signals used should match the corresponding signals of quartz from the host rocks: they should remain unchanged during transport and/or weathering processes.
Here we conduct an exploratory study on fine (4-11 μm) quartz from loess from Central Asia (Kazakhstan and Tajikistan), a region dominated by westerly air transport. These study sites were chosen since recent studies based on geochemical fingerprinting, grain-size modelling and meteorological reanalysis suggest the contribution from different source areas [2,3]. We investigate the signature of E’ (≡Si·, an unpaired electron at an oxygen vacancy site) and peroxy intrinsic defect centers (≡Si-O-O·and ≡Si–O· non-bridging oxygen) using ESR, by measuring both quartz grains extracted from both untreated samples, and from samples irradiated to 2000 Gy and subsequently heated to 10 min at 350 °C (as suggested by Toyoda and others [4]). By investigating the dose response of these signals, with and without the application of thermal treatments, we conclude that natural E` signals hold great promise for provenance studies, thus considerably simplifying the currently used measurement protocols. We observe a significant difference between the E’ and peroxy signals between the Kazakh and Tajik samples, which is in tune with the hypothesis that the two loess sites derive from different dust sources.
References
1. Allen, P.A., 2008. From landscapes into geological history. Nature 451, 274-276.
2. Li, Y., Song, Y., Fitzsimmons, K., Chen, X., Wang, Q., Sun, H., Zhang, Z., 2018. New evidence for the provenance and formation of loess deposits in the Ili river basin, Arid Central Asia. Aeolian Research 35, 1-8.
3. Li, Y., Song, Y., Kaskaoutis, D.G., Chen, X., Mamadjanov, Y., Tan, L., 2019. Atmospheric dust dynamics in southern Central Asia: Implications for buildup of Tajikistan loess sediments. Atmospheric Research 229, 74-85.
4. Toyoda, S., 2011. The E1` centre in natural quartz: its formation and applications to dating and provenance reserarches. Geochronometria, 38 (3), 242-248.
How to cite: Timar-Gabor, A., Dave, A., Kabacińska, Z., and Fitzsimmons, K.: Investigations on different measurement protocols of E` paramagnetic defect centres in quartz for provenance studies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1714, https://doi.org/10.5194/egusphere-egu21-1714, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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The sediment-routing concept [1] aims to integrate tectonic fluxes and climatically driven erosion, an approach that is at the core of modern studies into Earth-surface processes. The concept relies on the potential to track individual mineral grains from source to sink. Provenance studies are instrumental in this respect; until recently, almost all of these have focussed on accessory minerals. By contrast, the durability and abundance of quartz ensures that parent rocks containing quartz are represented by detrital quartz in their daughter sediment. Even the purest quartz crystal contains a vast number of point defects, which may be either intrinsic or due to impurities. Some of these defects remain unchanged under ionising radiation bombardment by natural environmental radioactivity, while others are transformed, generally in the form of charge trapping. Based on the dynamics of some of these radiation-sensitive defects under irradiation, quartz is frequently used for dating by luminescence or electron spin resonance (ESR). Another, less explored, application of these defects is the fingerprinting of sediment sources. For provenance applications to be successful, sedimentary quartz signals used should match the corresponding signals of quartz from the host rocks: they should remain unchanged during transport and/or weathering processes.
Here we conduct an exploratory study on fine (4-11 μm) quartz from loess from Central Asia (Kazakhstan and Tajikistan), a region dominated by westerly air transport. These study sites were chosen since recent studies based on geochemical fingerprinting, grain-size modelling and meteorological reanalysis suggest the contribution from different source areas [2,3]. We investigate the signature of E’ (≡Si·, an unpaired electron at an oxygen vacancy site) and peroxy intrinsic defect centers (≡Si-O-O·and ≡Si–O· non-bridging oxygen) using ESR, by measuring both quartz grains extracted from both untreated samples, and from samples irradiated to 2000 Gy and subsequently heated to 10 min at 350 °C (as suggested by Toyoda and others [4]). By investigating the dose response of these signals, with and without the application of thermal treatments, we conclude that natural E` signals hold great promise for provenance studies, thus considerably simplifying the currently used measurement protocols. We observe a significant difference between the E’ and peroxy signals between the Kazakh and Tajik samples, which is in tune with the hypothesis that the two loess sites derive from different dust sources.
References
1. Allen, P.A., 2008. From landscapes into geological history. Nature 451, 274-276.
2. Li, Y., Song, Y., Fitzsimmons, K., Chen, X., Wang, Q., Sun, H., Zhang, Z., 2018. New evidence for the provenance and formation of loess deposits in the Ili river basin, Arid Central Asia. Aeolian Research 35, 1-8.
3. Li, Y., Song, Y., Kaskaoutis, D.G., Chen, X., Mamadjanov, Y., Tan, L., 2019. Atmospheric dust dynamics in southern Central Asia: Implications for buildup of Tajikistan loess sediments. Atmospheric Research 229, 74-85.
4. Toyoda, S., 2011. The E1` centre in natural quartz: its formation and applications to dating and provenance reserarches. Geochronometria, 38 (3), 242-248.
How to cite: Timar-Gabor, A., Dave, A., Kabacińska, Z., and Fitzsimmons, K.: Investigations on different measurement protocols of E` paramagnetic defect centres in quartz for provenance studies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1714, https://doi.org/10.5194/egusphere-egu21-1714, 2021.
EGU21-6630 | vPICO presentations | GM2.9
Deciphering Past Desert-Margin Dynamics in Matmata, TunisiaSebastian Kreutzer, Sascha Meszner, Christoph Schmidt, Tobias Lauer, Melanie Bartz, Mathieu Duval, Moncef Bouaziz, Christopher-Bastian Roettig, Ulrich Hambach, and Dominik Faust
The terrestrial dust archives around Matmata (Tunisia) are unique in their morphological setting and grain-size composition (cf. Faust et al., 2020a, b). Located in front of the Grand Erg’s parlour in a critical zone at the northern edge of the Saharan desert, up to 35 m thick plateau-like loess accumulations cover pre-existing landscapes. In conjunction with intercalated palaeosols, the sandy loess, or rather loess like sediment records, tapped fluctuations in aeolian dynamics related to rapid and large-impact climate boundary shifts. Some of them may have severely threatened local ancient cultures, and future changes may put modern settlements and agriculture projects in this region at risk. Palaeolandscape reconstruction, supported by reliable chronologies, helps us to chart the past landscape, assess today's dynamics, and maybe predict possible future scenarios.
The ‘desert-loess’ records around Matmata seem to engulf a wide temporal range back to Marine Isotope Stage (MIS) 9. Trapped charge dating techniques, such as luminescence and electron spin resonance (ESR) dating, are versatile tools to decipher the timing of past landscape changes. However, for archives such as the one in the neighbourhood of Matmata, conventional luminescence methods (e.g., optically stimulated luminescence, OSL) exceed reported temporal limits. Kreutzer et al. (2018) have convincingly shown that a multi-method approach, using infrared radiofluorescence (IR-RF) and OSL in conjunction with ESR dating, has good potential to tackle long-term landscape dynamics. Our contribution reports first trapped charge dating results from Matmata in Tunisia. We provide preliminary luminescence (IR-RF, OSL) and ESR dating results from seven different sites and discuss the challenges encountered during our methodological work. Finally, we attempt to link our findings to regional climate fluctuations and drainage alterations observed for the large endorheic salt lakes in the Matmata plateau's close purlieu.
References
Faust, D., Kreutzer, S., Trigui, Y., Pachtmann, M., Mettig, G., Bouaziz, M., Recio Espejo, J.M., Diaz del Olmo, F., Schmidt, C., Lauer, T., Rezek, Z., Fülling, A., Meszner, S., 2020a. New findings of Middle Stone Age lithic artifacts from the Matmata loess region in southern Tunisia. E&G Quaternary Sci. J. 69, 55–58. doi:10.5194/egqsj-69-55-2020
Faust, D., Pachtmann, M., Mettig, G., Seidel, P., Bouaziz, M., Recio Espejo, J.M., Diaz del Olmo, F., Roettig, C.-B., Kreutzer, S., Hambach, U., Meszner, S., 2020b. Sandy soils in silty loess: the loess system of Matmata (Tunisia). Quaternaire 31, 175–186. doi:10.4000/quaternaire.14217
Kreutzer, S., Duval, M., Bartz, M., Bertran, P., Bosq, M., Eynaud, F., Verdin, F., Mercier, N., 2018. Deciphering long-term coastal dynamics using IR-RF and ESR dating: A case study from Médoc, south-West France. Quaternary Geochronology 48, 108–120. doi:10.1016/j.quageo.2018.09.005
How to cite: Kreutzer, S., Meszner, S., Schmidt, C., Lauer, T., Bartz, M., Duval, M., Bouaziz, M., Roettig, C.-B., Hambach, U., and Faust, D.: Deciphering Past Desert-Margin Dynamics in Matmata, Tunisia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6630, https://doi.org/10.5194/egusphere-egu21-6630, 2021.
The terrestrial dust archives around Matmata (Tunisia) are unique in their morphological setting and grain-size composition (cf. Faust et al., 2020a, b). Located in front of the Grand Erg’s parlour in a critical zone at the northern edge of the Saharan desert, up to 35 m thick plateau-like loess accumulations cover pre-existing landscapes. In conjunction with intercalated palaeosols, the sandy loess, or rather loess like sediment records, tapped fluctuations in aeolian dynamics related to rapid and large-impact climate boundary shifts. Some of them may have severely threatened local ancient cultures, and future changes may put modern settlements and agriculture projects in this region at risk. Palaeolandscape reconstruction, supported by reliable chronologies, helps us to chart the past landscape, assess today's dynamics, and maybe predict possible future scenarios.
The ‘desert-loess’ records around Matmata seem to engulf a wide temporal range back to Marine Isotope Stage (MIS) 9. Trapped charge dating techniques, such as luminescence and electron spin resonance (ESR) dating, are versatile tools to decipher the timing of past landscape changes. However, for archives such as the one in the neighbourhood of Matmata, conventional luminescence methods (e.g., optically stimulated luminescence, OSL) exceed reported temporal limits. Kreutzer et al. (2018) have convincingly shown that a multi-method approach, using infrared radiofluorescence (IR-RF) and OSL in conjunction with ESR dating, has good potential to tackle long-term landscape dynamics. Our contribution reports first trapped charge dating results from Matmata in Tunisia. We provide preliminary luminescence (IR-RF, OSL) and ESR dating results from seven different sites and discuss the challenges encountered during our methodological work. Finally, we attempt to link our findings to regional climate fluctuations and drainage alterations observed for the large endorheic salt lakes in the Matmata plateau's close purlieu.
References
Faust, D., Kreutzer, S., Trigui, Y., Pachtmann, M., Mettig, G., Bouaziz, M., Recio Espejo, J.M., Diaz del Olmo, F., Schmidt, C., Lauer, T., Rezek, Z., Fülling, A., Meszner, S., 2020a. New findings of Middle Stone Age lithic artifacts from the Matmata loess region in southern Tunisia. E&G Quaternary Sci. J. 69, 55–58. doi:10.5194/egqsj-69-55-2020
Faust, D., Pachtmann, M., Mettig, G., Seidel, P., Bouaziz, M., Recio Espejo, J.M., Diaz del Olmo, F., Roettig, C.-B., Kreutzer, S., Hambach, U., Meszner, S., 2020b. Sandy soils in silty loess: the loess system of Matmata (Tunisia). Quaternaire 31, 175–186. doi:10.4000/quaternaire.14217
Kreutzer, S., Duval, M., Bartz, M., Bertran, P., Bosq, M., Eynaud, F., Verdin, F., Mercier, N., 2018. Deciphering long-term coastal dynamics using IR-RF and ESR dating: A case study from Médoc, south-West France. Quaternary Geochronology 48, 108–120. doi:10.1016/j.quageo.2018.09.005
How to cite: Kreutzer, S., Meszner, S., Schmidt, C., Lauer, T., Bartz, M., Duval, M., Bouaziz, M., Roettig, C.-B., Hambach, U., and Faust, D.: Deciphering Past Desert-Margin Dynamics in Matmata, Tunisia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6630, https://doi.org/10.5194/egusphere-egu21-6630, 2021.
EGU21-9067 | vPICO presentations | GM2.9
How many grains do we need for tracer thermochronology?Andrea Madella, Christoph Glotzbach, and Todd A. Ehlers
Detrital tracer thermochronology exploits the relationship between bedrock thermochronometric ages and elevation to study spatial variations of upstream erosion from the distribution of detrital grain ages. If ages increase linearly with elevation and analytical uncertainties are negligible, spatially uniform erosion is expected to yield a detrital age distribution that mirrors the catchment’s hypsometric curve. Alternatively, a mismatch between detrital and hypsometric distributions may indicate non-uniform erosion within a catchment. For studies of this sort, measured age populations rarely exceed 100 grains, because applying thermochronology is time consuming and expensive. With such limited sample sizes, discerning between two detrital age distributions produced by different catchment erosion scenarios may be statistically impossible with high confidence. However, there is no established method to quantify the sample-size-dependent uncertainty inherent to detrital tracer thermochronology. Here, we investigate how sample size affects the uncertainty of detrital age distributions and how such uncertainty affects the ability to uniquely infer the erosional pattern of the upstream area. We developed a new tool to consistently report confidence levels as a function of sample size and case-specific variables. The proposed tool will be made available as open-source script along with test data. Testing the hypothesized erosion scenarios will help tracer thermochronologists define the minimum sample size (i.e. number of grain ages) to answer their specific scientific question with high level of statistical confidence. Alternatively, in cases of unavoidable small sample size, the related confidence level can be quantified.
How to cite: Madella, A., Glotzbach, C., and Ehlers, T. A.: How many grains do we need for tracer thermochronology?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9067, https://doi.org/10.5194/egusphere-egu21-9067, 2021.
Detrital tracer thermochronology exploits the relationship between bedrock thermochronometric ages and elevation to study spatial variations of upstream erosion from the distribution of detrital grain ages. If ages increase linearly with elevation and analytical uncertainties are negligible, spatially uniform erosion is expected to yield a detrital age distribution that mirrors the catchment’s hypsometric curve. Alternatively, a mismatch between detrital and hypsometric distributions may indicate non-uniform erosion within a catchment. For studies of this sort, measured age populations rarely exceed 100 grains, because applying thermochronology is time consuming and expensive. With such limited sample sizes, discerning between two detrital age distributions produced by different catchment erosion scenarios may be statistically impossible with high confidence. However, there is no established method to quantify the sample-size-dependent uncertainty inherent to detrital tracer thermochronology. Here, we investigate how sample size affects the uncertainty of detrital age distributions and how such uncertainty affects the ability to uniquely infer the erosional pattern of the upstream area. We developed a new tool to consistently report confidence levels as a function of sample size and case-specific variables. The proposed tool will be made available as open-source script along with test data. Testing the hypothesized erosion scenarios will help tracer thermochronologists define the minimum sample size (i.e. number of grain ages) to answer their specific scientific question with high level of statistical confidence. Alternatively, in cases of unavoidable small sample size, the related confidence level can be quantified.
How to cite: Madella, A., Glotzbach, C., and Ehlers, T. A.: How many grains do we need for tracer thermochronology?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9067, https://doi.org/10.5194/egusphere-egu21-9067, 2021.
EGU21-13071 | vPICO presentations | GM2.9
Effect of rock strength on exhumation and the thermochronologic record: The south-central Colorado exampleSabrina Kainz, Lon Abbott, Rebecca Flowers, and James Metcalf
Past work has used the Southern Rocky Mountains (SRM) in the U.S. state of Colorado to illustrate the important role that rock strength plays in the histories recorded by the apatite fission track (AFT) and apatite (U-Th)/He (AHe) low-temperature thermochronometers (Flowers & Ehlers, 2018). The SRM were initially raised during the Laramide Orogeny, ca. 70-45 Ma, but consensus exists that the region also experienced a later, post-Laramide exhumation event. Flowers & Ehlers (2018) pointed to the low erosion potential of the Precambrian crystalline basement rocks that crop out in most SRM ranges as a primary reason for the abundance of 55-70 Ma “Laramide” AFT and AHe dates in the region, compared to a paucity of younger dates that would presumably be produced through erosion triggered by the post-Laramide exhumation event. South-central Colorado offers a test of this hypothesis, due to lateral variations in rock erodibility provided by the presence here of both sedimentary and crystalline Laramide ranges and adjacent sedimentary basins. The combination of our ongoing AHe study with previous south-central Colorado AFT and AHe work reveals kilometer-scale post-Laramide (Oligo-Miocene) exhumation has occurred in areas that possess thick sedimentary rock sequences whereas exhumation has been negligible where crystalline basement comprises the land surface.
South-central Colorado’s Sangre de Cristo Mountains consist of an imbricate stack of thrust sheets composed of Permian sedimentary rock. About 30 km farther east stand the Wet Mountains, another Laramide range – but one composed of Precambrian basement rock. The Raton Basin, a SRM foreland basin filled with 2 km of synorogenic fill underlain by a thick sequence of marine shale, lies south and east of the two ranges. The Wet Mountains thus form a peninsula of strong crystalline rock surrounded by more erodible sedimentary rocks to the west, south, and east.
Our study and that of Landman (2018) records at least 2 km of erosion in the Raton Basin east and south of the Wet Mountains since 25 Ma. Lindsey et al (1986) obtained 24-15 Ma AFT dates from the Paleozoic sedimentary rocks of the Sangre de Cristo Mountains, demonstrating that kilometer-scale Oligo-Miocene exhumation occurred just west of the Wet Mountains. By contrast, Kelley and Chapin (2004) obtained only pre-Laramide AFT ages between 228-110 Ma for 17 samples of Precambrian basement from the crest of the Wet Mountains. A 32 Ma ash flow tuff unconformably overlies Precambrian basement on Greenhorn Mountain, the Wet Mountains’ highest and southernmost peak. Its presence reinforces the conclusion, based on the AFT dates, that Oligo-Miocene erosion of the Wet Mountain massif has been minimal simultaneous with kilometer-scale exhumation to the west, south, and east. These results illustrate the important role that rock strength plays in determining the dates recorded in low-temperature thermochronologic studies.
How to cite: Kainz, S., Abbott, L., Flowers, R., and Metcalf, J.: Effect of rock strength on exhumation and the thermochronologic record: The south-central Colorado example, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13071, https://doi.org/10.5194/egusphere-egu21-13071, 2021.
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Past work has used the Southern Rocky Mountains (SRM) in the U.S. state of Colorado to illustrate the important role that rock strength plays in the histories recorded by the apatite fission track (AFT) and apatite (U-Th)/He (AHe) low-temperature thermochronometers (Flowers & Ehlers, 2018). The SRM were initially raised during the Laramide Orogeny, ca. 70-45 Ma, but consensus exists that the region also experienced a later, post-Laramide exhumation event. Flowers & Ehlers (2018) pointed to the low erosion potential of the Precambrian crystalline basement rocks that crop out in most SRM ranges as a primary reason for the abundance of 55-70 Ma “Laramide” AFT and AHe dates in the region, compared to a paucity of younger dates that would presumably be produced through erosion triggered by the post-Laramide exhumation event. South-central Colorado offers a test of this hypothesis, due to lateral variations in rock erodibility provided by the presence here of both sedimentary and crystalline Laramide ranges and adjacent sedimentary basins. The combination of our ongoing AHe study with previous south-central Colorado AFT and AHe work reveals kilometer-scale post-Laramide (Oligo-Miocene) exhumation has occurred in areas that possess thick sedimentary rock sequences whereas exhumation has been negligible where crystalline basement comprises the land surface.
South-central Colorado’s Sangre de Cristo Mountains consist of an imbricate stack of thrust sheets composed of Permian sedimentary rock. About 30 km farther east stand the Wet Mountains, another Laramide range – but one composed of Precambrian basement rock. The Raton Basin, a SRM foreland basin filled with 2 km of synorogenic fill underlain by a thick sequence of marine shale, lies south and east of the two ranges. The Wet Mountains thus form a peninsula of strong crystalline rock surrounded by more erodible sedimentary rocks to the west, south, and east.
Our study and that of Landman (2018) records at least 2 km of erosion in the Raton Basin east and south of the Wet Mountains since 25 Ma. Lindsey et al (1986) obtained 24-15 Ma AFT dates from the Paleozoic sedimentary rocks of the Sangre de Cristo Mountains, demonstrating that kilometer-scale Oligo-Miocene exhumation occurred just west of the Wet Mountains. By contrast, Kelley and Chapin (2004) obtained only pre-Laramide AFT ages between 228-110 Ma for 17 samples of Precambrian basement from the crest of the Wet Mountains. A 32 Ma ash flow tuff unconformably overlies Precambrian basement on Greenhorn Mountain, the Wet Mountains’ highest and southernmost peak. Its presence reinforces the conclusion, based on the AFT dates, that Oligo-Miocene erosion of the Wet Mountain massif has been minimal simultaneous with kilometer-scale exhumation to the west, south, and east. These results illustrate the important role that rock strength plays in determining the dates recorded in low-temperature thermochronologic studies.
How to cite: Kainz, S., Abbott, L., Flowers, R., and Metcalf, J.: Effect of rock strength on exhumation and the thermochronologic record: The south-central Colorado example, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13071, https://doi.org/10.5194/egusphere-egu21-13071, 2021.
EGU21-2608 | vPICO presentations | GM2.9
Double dating (U–Pb and (U–Th)/He) of detrital zircon from the Gonfolite Group (European Alps) and implications for the lag-time approach to detrital thermochronologyMarco G. Malusà, Owen A. Anfinson, and Daniel F. Stockli
Detrital thermochronologic analyses are increasingly employed to develop quantitative models of landscape evolution and constrain rates of exhumation due to erosion. Crucial for this kind of application is a correct discrimination between thermochronologic ages that record cooling due to exhumation, i.e., the motion of parent rocks towards Earth’s surface, and thermochronologic ages that record cooling independent from exhumation, as expected for example in volcanic and shallow-level plutonic rocks. A suitable approach for the identification of magmatic crystallization ages is provided by double dating, which combines for example U–Pb and (U–Th)/He analyses of the same mineral grain. Magmatic zircon crystallized from volcanic or shallow-level plutonic rocks should display identical U–Pb and (U–Th)/He (ZHe) ages within error, because of rapid magma crystallization in the upper crust where country rocks are at temperatures cooler than the partial retention zone of the ZHe system. Conversely, zircon grains crystallized at greater depth and recording cooling during exhumation should display ZHe ages younger than the corresponding U–Pb ages. These latter ZHe ages may constrain the long-term exhumation history of the source rocks according to the lag-time approach, provided that a range of assumptions are properly evaluated (e.g., Malusà and Fitzgerald 2020). Here, we explore the possibility that detrital zircon grains yielding ZHe ages younger than the corresponding U–Pb ages may record country-rock cooling within a contact aureole rather than exhumation. To tackle this issue, we applied a double-dating approach including U-Pb and ZHe analyses to samples of the Gonfolite Group exposed south of the European Alps. The Gonfolite Group largely derives from erosion of the Bergell volcano-plutonic complex and adjacent country rocks, and its mineral-age stratigraphy is extremely well constrained (Malusà et al. 2011, 2016). Analyses were performed in the UTChron Geochronology Facility at University of Texas at Austin. For U-Pb LA-ICPMS depth-profile analysis, all detrital zircon grains were mounted without polishing, which allowed for subsequent ZHe analysis on the same grains. Zircon for ZHe analyses were selected among those not derived from the Bergell complex or other Periadriatic magmatic rocks, as constrained by their U-Pb age. We found that ca 40% of double-dated grains, despite yielding a ZHe age younger than their U-Pb age, likely record cooling within the Bergell contact aureole, not exhumation. These findings have major implications for a correct application of the lag-time approach to detrital thermochronology and underline the importance of a well-constrained mineral-age stratigraphy for a reliable geologic interpretation.
Malusà MG, Villa IM, Vezzoli G, Garzanti E (2011) Earth Planet Sci Lett 301(1-2), 324-336
Malusà MG, Anfinson OA, Dafov LN, Stockli DF (2016) Geology 44(2), 155-158
Malusà MG, Fitzgerald, PG (2020) Earth-Sci Rev 201, 103074
How to cite: Malusà, M. G., Anfinson, O. A., and Stockli, D. F.: Double dating (U–Pb and (U–Th)/He) of detrital zircon from the Gonfolite Group (European Alps) and implications for the lag-time approach to detrital thermochronology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2608, https://doi.org/10.5194/egusphere-egu21-2608, 2021.
Detrital thermochronologic analyses are increasingly employed to develop quantitative models of landscape evolution and constrain rates of exhumation due to erosion. Crucial for this kind of application is a correct discrimination between thermochronologic ages that record cooling due to exhumation, i.e., the motion of parent rocks towards Earth’s surface, and thermochronologic ages that record cooling independent from exhumation, as expected for example in volcanic and shallow-level plutonic rocks. A suitable approach for the identification of magmatic crystallization ages is provided by double dating, which combines for example U–Pb and (U–Th)/He analyses of the same mineral grain. Magmatic zircon crystallized from volcanic or shallow-level plutonic rocks should display identical U–Pb and (U–Th)/He (ZHe) ages within error, because of rapid magma crystallization in the upper crust where country rocks are at temperatures cooler than the partial retention zone of the ZHe system. Conversely, zircon grains crystallized at greater depth and recording cooling during exhumation should display ZHe ages younger than the corresponding U–Pb ages. These latter ZHe ages may constrain the long-term exhumation history of the source rocks according to the lag-time approach, provided that a range of assumptions are properly evaluated (e.g., Malusà and Fitzgerald 2020). Here, we explore the possibility that detrital zircon grains yielding ZHe ages younger than the corresponding U–Pb ages may record country-rock cooling within a contact aureole rather than exhumation. To tackle this issue, we applied a double-dating approach including U-Pb and ZHe analyses to samples of the Gonfolite Group exposed south of the European Alps. The Gonfolite Group largely derives from erosion of the Bergell volcano-plutonic complex and adjacent country rocks, and its mineral-age stratigraphy is extremely well constrained (Malusà et al. 2011, 2016). Analyses were performed in the UTChron Geochronology Facility at University of Texas at Austin. For U-Pb LA-ICPMS depth-profile analysis, all detrital zircon grains were mounted without polishing, which allowed for subsequent ZHe analysis on the same grains. Zircon for ZHe analyses were selected among those not derived from the Bergell complex or other Periadriatic magmatic rocks, as constrained by their U-Pb age. We found that ca 40% of double-dated grains, despite yielding a ZHe age younger than their U-Pb age, likely record cooling within the Bergell contact aureole, not exhumation. These findings have major implications for a correct application of the lag-time approach to detrital thermochronology and underline the importance of a well-constrained mineral-age stratigraphy for a reliable geologic interpretation.
Malusà MG, Villa IM, Vezzoli G, Garzanti E (2011) Earth Planet Sci Lett 301(1-2), 324-336
Malusà MG, Anfinson OA, Dafov LN, Stockli DF (2016) Geology 44(2), 155-158
Malusà MG, Fitzgerald, PG (2020) Earth-Sci Rev 201, 103074
How to cite: Malusà, M. G., Anfinson, O. A., and Stockli, D. F.: Double dating (U–Pb and (U–Th)/He) of detrital zircon from the Gonfolite Group (European Alps) and implications for the lag-time approach to detrital thermochronology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2608, https://doi.org/10.5194/egusphere-egu21-2608, 2021.
EGU21-10288 | vPICO presentations | GM2.9
Cenozoic reshaping of the Barents Shelf: Influence of erosion, sedimentation, and glaciationSergei Medvedev, Jan Inge Faleide, and Ebbe Hartz
Morphology evolution of the Barents Shelf is a key question in understanding how erosion and glaciation reshape the face of the Earth. The Cenozoic history is a subject of a longstanding debate in the Barents realm, in part, due to decades of petroleum exploration in the region. We address here the whole-region study of the influence of a set of mechanisms and factors on the erosion and sedimentation estimations. Several local studies along the edges of the Barents shelf enlighten the relation between sediments accumulated off-shelf and amount of erosion in the adjacent areas. There are only few studies of the entire Barents region but precision of these studies is limited due to uneven distribution of measurements and uncertainties in paleo-conditions. We compare the masses of sediments accumulated along the edges of the Barents shelf with erosion predicted in Henriksen et al. (2011) and estimate that erosion is significantly overestimated. Local corrections to this erosional model do not bring balance close. The major part of the erosional estimate is based on seismic methods and well logs reflecting sedimentary rock’s compaction changes caused by (now partly removed) load from above. This load, however, may be caused not by eroded material alone, but also by ice cap during the glacial cycles. Reduction of erosional estimates by accounting for ice load bring balance between existing erosional model and accumulated sediments close. We also model the glacial erosion using the numerical approach erosion backward in time (Medvedev et al., 2018). The method was modified for this study to account for difference in the lateral length scale of on- and off-shore erosion and flexural isostasy. We compare this erosional model with estimated masses of glacial-induced sediments off-shelf the Barents Sea. The results performed for a range of controlling parameters show that the Barents shelf was mainly submarine at the beginning of glaciation.
Henriksen, E., Bjørnseth, H., Hals, T., Heide, T., Kiryukhina, T., Kløvjan, O., Larssen, G., Ryseth, A., Rønning, K., and Sollid, K., 2011, Uplift and erosion of the greater Barents Sea: impact on prospectivity and petroleum systems. Geological Society, London, Memoirs 35, 271-281.
Medvedev, S., Hartz, E. H., and Faleide, J. I., 2018, Erosion-driven vertical motions of the circum Arctic: Comparative analysis of modern topography. Journal of Geodynamics 119, 62-81.
How to cite: Medvedev, S., Faleide, J. I., and Hartz, E.: Cenozoic reshaping of the Barents Shelf: Influence of erosion, sedimentation, and glaciation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10288, https://doi.org/10.5194/egusphere-egu21-10288, 2021.
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Morphology evolution of the Barents Shelf is a key question in understanding how erosion and glaciation reshape the face of the Earth. The Cenozoic history is a subject of a longstanding debate in the Barents realm, in part, due to decades of petroleum exploration in the region. We address here the whole-region study of the influence of a set of mechanisms and factors on the erosion and sedimentation estimations. Several local studies along the edges of the Barents shelf enlighten the relation between sediments accumulated off-shelf and amount of erosion in the adjacent areas. There are only few studies of the entire Barents region but precision of these studies is limited due to uneven distribution of measurements and uncertainties in paleo-conditions. We compare the masses of sediments accumulated along the edges of the Barents shelf with erosion predicted in Henriksen et al. (2011) and estimate that erosion is significantly overestimated. Local corrections to this erosional model do not bring balance close. The major part of the erosional estimate is based on seismic methods and well logs reflecting sedimentary rock’s compaction changes caused by (now partly removed) load from above. This load, however, may be caused not by eroded material alone, but also by ice cap during the glacial cycles. Reduction of erosional estimates by accounting for ice load bring balance between existing erosional model and accumulated sediments close. We also model the glacial erosion using the numerical approach erosion backward in time (Medvedev et al., 2018). The method was modified for this study to account for difference in the lateral length scale of on- and off-shore erosion and flexural isostasy. We compare this erosional model with estimated masses of glacial-induced sediments off-shelf the Barents Sea. The results performed for a range of controlling parameters show that the Barents shelf was mainly submarine at the beginning of glaciation.
Henriksen, E., Bjørnseth, H., Hals, T., Heide, T., Kiryukhina, T., Kløvjan, O., Larssen, G., Ryseth, A., Rønning, K., and Sollid, K., 2011, Uplift and erosion of the greater Barents Sea: impact on prospectivity and petroleum systems. Geological Society, London, Memoirs 35, 271-281.
Medvedev, S., Hartz, E. H., and Faleide, J. I., 2018, Erosion-driven vertical motions of the circum Arctic: Comparative analysis of modern topography. Journal of Geodynamics 119, 62-81.
How to cite: Medvedev, S., Faleide, J. I., and Hartz, E.: Cenozoic reshaping of the Barents Shelf: Influence of erosion, sedimentation, and glaciation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10288, https://doi.org/10.5194/egusphere-egu21-10288, 2021.
GM2.10 – Advances in modelling of erosion processes, sediment dynamics, and landscape evolution
EGU21-2843 | vPICO presentations | GM2.10
Using GeoWEPP model, high-resolution 3D models and ground-based survey to detect sedimentation changes and morphological adjustments in an ephemeral streamCarmelo Conesa-García, Alberto Martínez-Salvador, Francisco Martínez-Capel, Carlos Puig-Mengual, Pedro Pérez-Cutillas, Demetrio A. Zema, and Giuseppe Bombino
The ephemeral streams, which drain steep and metamorphic catchments, experience rapid and torrential runoff with high sediment loads. These processes cause important morphological changes in the channels. This work proposes a methodological approach to verify the change patterns in the magnitude and frequency of the hydrological events that geomorphologically model this type of channels. A gravel-bed ephemeral stream, the Rambla de la Azohía, located in the coastal area of the Betic Mountains (southeastern Spain), has been chosen as a study case for the method validation. This approach focuses first on relationships between peak discharges and sediment budgets measured at checkpoints for specific events from 2018 to 2020 and then runoff data and sediment yields obtained using the GeoWEPP model for the same cases after calibration/validation. Water depths and concentrations of suspended sediment recorded during the events of 2018 and 2019 were used for model calibration and validation, respectively. For the calibration stage, a sensitivity analysis was carried out in order to detect the parameters that most influence the model output and are, therefore, suitable for calibration. Finally, the results obtained in the calibration and validation periods were evaluated using the Nash-Sutcliffe efficiency (NS) and percent bias (PBIAS). Values of NS and PBIAS equal to 0.86 and 7.81%, respectively, were found in the calibration period, while these indices were 0.81 and -4.1% in the validation period. All these values confirm the model’s capacity to simulate peak flow and erosion in the experimental conditions. Topographical variations and sediment budgets, verified combining high-resolution digital terrain models (HRDTMs) with ortophotographs and point clouds dated in 2018, 2019 and 2020, and ground-based surveys, were analyzed in relation to changes in discharge in order to determine geomorphic flow thresholds. According to these thresholds, three classes of morphological adjustments were defined: 1. global changes caused by discharges over the bankfull depth; 2. large alterations at the bankfull stage driven by a noticeable vertical bed accretion and lateral erosion; 3. moderate adjustments during sub-bankfull flows that are able to modify alluvial bars; and 4. minor events, in which the accretion of these bars ceases and shallow scouring and washing actions prevail. These geomorphic thresholds were then applied to the complete series of discharges simulated using GeoWEPP at the event scale during the period 1997-2019. The results revealed a significant increase in the number of events that are capable to produce bed aggradation and bank erosion. This research was funded by FEDER / Spanish Ministry of Science, Innovation and Universities - State Research Agency (AEI) / Projects CGL2017-84625- C2-1-R and CGL2017-84625-C2-2-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
How to cite: Conesa-García, C., Martínez-Salvador, A., Martínez-Capel, F., Puig-Mengual, C., Pérez-Cutillas, P., Zema, D. A., and Bombino, G.: Using GeoWEPP model, high-resolution 3D models and ground-based survey to detect sedimentation changes and morphological adjustments in an ephemeral stream, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2843, https://doi.org/10.5194/egusphere-egu21-2843, 2021.
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The ephemeral streams, which drain steep and metamorphic catchments, experience rapid and torrential runoff with high sediment loads. These processes cause important morphological changes in the channels. This work proposes a methodological approach to verify the change patterns in the magnitude and frequency of the hydrological events that geomorphologically model this type of channels. A gravel-bed ephemeral stream, the Rambla de la Azohía, located in the coastal area of the Betic Mountains (southeastern Spain), has been chosen as a study case for the method validation. This approach focuses first on relationships between peak discharges and sediment budgets measured at checkpoints for specific events from 2018 to 2020 and then runoff data and sediment yields obtained using the GeoWEPP model for the same cases after calibration/validation. Water depths and concentrations of suspended sediment recorded during the events of 2018 and 2019 were used for model calibration and validation, respectively. For the calibration stage, a sensitivity analysis was carried out in order to detect the parameters that most influence the model output and are, therefore, suitable for calibration. Finally, the results obtained in the calibration and validation periods were evaluated using the Nash-Sutcliffe efficiency (NS) and percent bias (PBIAS). Values of NS and PBIAS equal to 0.86 and 7.81%, respectively, were found in the calibration period, while these indices were 0.81 and -4.1% in the validation period. All these values confirm the model’s capacity to simulate peak flow and erosion in the experimental conditions. Topographical variations and sediment budgets, verified combining high-resolution digital terrain models (HRDTMs) with ortophotographs and point clouds dated in 2018, 2019 and 2020, and ground-based surveys, were analyzed in relation to changes in discharge in order to determine geomorphic flow thresholds. According to these thresholds, three classes of morphological adjustments were defined: 1. global changes caused by discharges over the bankfull depth; 2. large alterations at the bankfull stage driven by a noticeable vertical bed accretion and lateral erosion; 3. moderate adjustments during sub-bankfull flows that are able to modify alluvial bars; and 4. minor events, in which the accretion of these bars ceases and shallow scouring and washing actions prevail. These geomorphic thresholds were then applied to the complete series of discharges simulated using GeoWEPP at the event scale during the period 1997-2019. The results revealed a significant increase in the number of events that are capable to produce bed aggradation and bank erosion. This research was funded by FEDER / Spanish Ministry of Science, Innovation and Universities - State Research Agency (AEI) / Projects CGL2017-84625- C2-1-R and CGL2017-84625-C2-2-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
How to cite: Conesa-García, C., Martínez-Salvador, A., Martínez-Capel, F., Puig-Mengual, C., Pérez-Cutillas, P., Zema, D. A., and Bombino, G.: Using GeoWEPP model, high-resolution 3D models and ground-based survey to detect sedimentation changes and morphological adjustments in an ephemeral stream, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2843, https://doi.org/10.5194/egusphere-egu21-2843, 2021.
EGU21-957 | vPICO presentations | GM2.10
Chasing sand: evolution of the surface and subsurface drainage of the Sinkhole Plain, Central Kentucky Karst, USARachel Bosch and Dylan Ward
This work extends the established geochronology of the Mammoth Cave region, Kentucky, USA, spatially and temporally, to infer evolution of the karst landscape and to consider the shifting drainage basins of the Barren River and the Green River in relation to regional drainage rearrangements. Previous studies have focused on the Mammoth Cave System and used cosmogenic radionuclide dating to link the incision history of the Green River and the Cave as far back as 3.25 Ma. We posit that prior to the wide-spread karstification that produced Mammoth Cave, drainage consisted of a purely fluvial stream network flow on the youngest clastic rocks. When this caprock was breached, carbonate dissolution ensued and the system transitioned to fluviokarst. Relict large trunk passages that originated at that time can be found in features such as Prewitts Knob, Bald Knob, and Huckleberry Knob. We intend to use sediments and speleothems collected from Crystal Onyx Cave in Prewitts Knob to constrain the age of this stage of karst development and to provide an estimate of the long-term erosion rate of the Sinkhole Plain surrounding the knob. These relict trunks were also used for cave stream profile reconstruction in combination with the east-west trending uvalas and sets of steep, deep sinkholes. We interpret that paleodrainage as having been west-flowing into the Barren River which then served as regional base level. Thus, we infer that as the rivers incised, this drainage was pirated to the north and began flowing to the Green River. The system then evolved into a more mature karst, large conduits near the surface collapsed, and dissected the landscape into isolated depressions. The collapsed limestone formed red soil and the sandstone produced angular clasts scattered throughout that soil. The retreating Chester Cuesta, marking the boundary between the Sinkhole Plain and the sandstone-capped Chester Upland, eroded most rapidly where limestone was exposed to the surface and more slowly where it was sandstone-capped leaving abandoned isolated cave trunk passage segments in remnant knobs. The results of this work have implications for understanding timescales of the evolution of karst systems in unconfined carbonate sequences as well as the interaction of karst areas with the transience in drainage networks.
How to cite: Bosch, R. and Ward, D.: Chasing sand: evolution of the surface and subsurface drainage of the Sinkhole Plain, Central Kentucky Karst, USA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-957, https://doi.org/10.5194/egusphere-egu21-957, 2021.
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This work extends the established geochronology of the Mammoth Cave region, Kentucky, USA, spatially and temporally, to infer evolution of the karst landscape and to consider the shifting drainage basins of the Barren River and the Green River in relation to regional drainage rearrangements. Previous studies have focused on the Mammoth Cave System and used cosmogenic radionuclide dating to link the incision history of the Green River and the Cave as far back as 3.25 Ma. We posit that prior to the wide-spread karstification that produced Mammoth Cave, drainage consisted of a purely fluvial stream network flow on the youngest clastic rocks. When this caprock was breached, carbonate dissolution ensued and the system transitioned to fluviokarst. Relict large trunk passages that originated at that time can be found in features such as Prewitts Knob, Bald Knob, and Huckleberry Knob. We intend to use sediments and speleothems collected from Crystal Onyx Cave in Prewitts Knob to constrain the age of this stage of karst development and to provide an estimate of the long-term erosion rate of the Sinkhole Plain surrounding the knob. These relict trunks were also used for cave stream profile reconstruction in combination with the east-west trending uvalas and sets of steep, deep sinkholes. We interpret that paleodrainage as having been west-flowing into the Barren River which then served as regional base level. Thus, we infer that as the rivers incised, this drainage was pirated to the north and began flowing to the Green River. The system then evolved into a more mature karst, large conduits near the surface collapsed, and dissected the landscape into isolated depressions. The collapsed limestone formed red soil and the sandstone produced angular clasts scattered throughout that soil. The retreating Chester Cuesta, marking the boundary between the Sinkhole Plain and the sandstone-capped Chester Upland, eroded most rapidly where limestone was exposed to the surface and more slowly where it was sandstone-capped leaving abandoned isolated cave trunk passage segments in remnant knobs. The results of this work have implications for understanding timescales of the evolution of karst systems in unconfined carbonate sequences as well as the interaction of karst areas with the transience in drainage networks.
How to cite: Bosch, R. and Ward, D.: Chasing sand: evolution of the surface and subsurface drainage of the Sinkhole Plain, Central Kentucky Karst, USA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-957, https://doi.org/10.5194/egusphere-egu21-957, 2021.
EGU21-7520 | vPICO presentations | GM2.10
Mapping debris-flow channels in the southern Central Andes using high-resolution topographic dataAriane Mueting, Bodo Bookhagen, and Manfred R. Strecker
Resolving Earth’s surface at the meter scale is essential for an improved understanding of topographic signatures generated by debris-flow activity in high-relief mountainous terrains. Here, we explore the applicability and potential of digital elevation models (DEMs) derived from stereo-photogrammetry for debris-flow detection in the southern Central Andes of NW Argentina. Our analysis relies on a high-resolution (3 m) DEM created from SPOT-7 tri-stereo satellite data. We carefully validated DEM quality with ~5000 differential GPS points for an area of 245 km² in the Quebrada del Toro basin within the Eastern Cordillera.
We build upon previous work that suggests that debris flows have a distinct signature in the drainage area and slope framework: debris-flow channels exhibit a nearly constant slope (no channel curvature), while channels dominated by fluvial transport processes show a negative power-law behavior in log-log space. Drainage-area approaches in geomorphic analysis are fast and efficient tools to distinguish signatures of debris-flow and fluvial transport processes, yet they might introduce an averaging bias because upstream areas are analyzed jointly.
For a more precise localization and assessment of debris-flow activity, we evaluate topographic signatures of individual channels. We present a new approach that relies on connected components of similar slope that can be attributed to different transport regimes. Debris-flow activity reflects particularly steep segments of medium connected-component lengths in small drainage areas. The spatial occurrence and lengths of these segments are controlled by geologic and lithologic boundary conditions and we find that the highest debris-flow activity corresponds with steep slopes in areas documented Quaternary tectonic activity and the exposure of pervasively fractured bedrock. Comparing our results to topographic signatures of the corresponding catchments in log-log space, we show that individual channel approaches allow to better detect intra-catchment variability. These are imperative for understanding erosion and sediment-transport processes in the river channel. Since high-resolution data are needed to reliably resolve debris-flow channels, our meter-scale DEMs greatly improve the localization and prediction of debris-flow activity. Thus, for evaluations of recurring hazardous debris-flow activity in extensive, remote, and sparsely vegetated mountainous landscapes, stereo-photogrammetry presents a very suitable and cost-efficient alternative to airborne lidar data.
How to cite: Mueting, A., Bookhagen, B., and Strecker, M. R.: Mapping debris-flow channels in the southern Central Andes using high-resolution topographic data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7520, https://doi.org/10.5194/egusphere-egu21-7520, 2021.
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Resolving Earth’s surface at the meter scale is essential for an improved understanding of topographic signatures generated by debris-flow activity in high-relief mountainous terrains. Here, we explore the applicability and potential of digital elevation models (DEMs) derived from stereo-photogrammetry for debris-flow detection in the southern Central Andes of NW Argentina. Our analysis relies on a high-resolution (3 m) DEM created from SPOT-7 tri-stereo satellite data. We carefully validated DEM quality with ~5000 differential GPS points for an area of 245 km² in the Quebrada del Toro basin within the Eastern Cordillera.
We build upon previous work that suggests that debris flows have a distinct signature in the drainage area and slope framework: debris-flow channels exhibit a nearly constant slope (no channel curvature), while channels dominated by fluvial transport processes show a negative power-law behavior in log-log space. Drainage-area approaches in geomorphic analysis are fast and efficient tools to distinguish signatures of debris-flow and fluvial transport processes, yet they might introduce an averaging bias because upstream areas are analyzed jointly.
For a more precise localization and assessment of debris-flow activity, we evaluate topographic signatures of individual channels. We present a new approach that relies on connected components of similar slope that can be attributed to different transport regimes. Debris-flow activity reflects particularly steep segments of medium connected-component lengths in small drainage areas. The spatial occurrence and lengths of these segments are controlled by geologic and lithologic boundary conditions and we find that the highest debris-flow activity corresponds with steep slopes in areas documented Quaternary tectonic activity and the exposure of pervasively fractured bedrock. Comparing our results to topographic signatures of the corresponding catchments in log-log space, we show that individual channel approaches allow to better detect intra-catchment variability. These are imperative for understanding erosion and sediment-transport processes in the river channel. Since high-resolution data are needed to reliably resolve debris-flow channels, our meter-scale DEMs greatly improve the localization and prediction of debris-flow activity. Thus, for evaluations of recurring hazardous debris-flow activity in extensive, remote, and sparsely vegetated mountainous landscapes, stereo-photogrammetry presents a very suitable and cost-efficient alternative to airborne lidar data.
How to cite: Mueting, A., Bookhagen, B., and Strecker, M. R.: Mapping debris-flow channels in the southern Central Andes using high-resolution topographic data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7520, https://doi.org/10.5194/egusphere-egu21-7520, 2021.
EGU21-8569 | vPICO presentations | GM2.10 | Highlight
Evaluating the stability and evolution of a proposed post mining landform.Welivitiyage Don Dimuth Prasad Welivitiya, Garry Willgoose, and Gregory Hancock
Evaluating the future stability and land denudation rates of natural or anthropogenic landforms is paramount for sustainable land use practices. Landform evolution models can be powerful tools in this endeavour. In this study we used the well-established landform evolution model SIBERIA and the newly developed coupled soilscape-landform evolution model SSSPAM to simulate the evolution of a proposed post mining landform. SIBERIA uses a cellular digital elevation model to simulate annual average fluvial and diffusive erosion on landforms using annual average precipitation. However it does not simulate the soil profile evolution on the evolving landform. The new SSSPAM coupled soilscape-landform evolution model has the ability to assess the overall erosion rates of catchment scale landforms either using short term precipitation events, variable precipitation or time averaged precipitation rates. In addition, SSSPAM is able to simulate the evolution of the soil profile of the evolving landform using pedogenetic processes such as physical weathering and armouring.
To assess the reliability of SSSPAM, model predictions at 100 and 10000 years were compared with SIBERIA predictions at the same times. During the long term (10000yr) simulation the effect of armouring and weathering on the landform evolution was also assessed. The results obtained from these different simulations were compared and contrasted. Comparison of the short term simulations revealed that SSSPAM results compare well with the simulation results of the more established SIBERIA model. Long term simulation showed that SSSPAM simulation results also compares well with SIBERIA simulations while the erosion rates predicted by both models are close to the land denudation rates measured in the field. The soil profile characteristics and channel forms simulated by SSSPAM long term simulations were examined using several landform cross-sections. This analyses revealed that SSSPAM produces deep incised channels with very low soil thickness in upper reaches of the catchment and shallow channels with relatively thick soil layers in the lower reaches of the catchment. These SSSPAM simulated channels match well with the channel forms and distribution of bedrock channels and alluvial channels observed in the field. The analysis of the catchment cross-sections also showed that SSSPAM is capable of reproducing complex subsurface soil evolution and stratification and spatial variability of soil profile characteristics typically observed in the field.
How to cite: Welivitiya, W. D. D. P., Willgoose, G., and Hancock, G.: Evaluating the stability and evolution of a proposed post mining landform., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8569, https://doi.org/10.5194/egusphere-egu21-8569, 2021.
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Evaluating the future stability and land denudation rates of natural or anthropogenic landforms is paramount for sustainable land use practices. Landform evolution models can be powerful tools in this endeavour. In this study we used the well-established landform evolution model SIBERIA and the newly developed coupled soilscape-landform evolution model SSSPAM to simulate the evolution of a proposed post mining landform. SIBERIA uses a cellular digital elevation model to simulate annual average fluvial and diffusive erosion on landforms using annual average precipitation. However it does not simulate the soil profile evolution on the evolving landform. The new SSSPAM coupled soilscape-landform evolution model has the ability to assess the overall erosion rates of catchment scale landforms either using short term precipitation events, variable precipitation or time averaged precipitation rates. In addition, SSSPAM is able to simulate the evolution of the soil profile of the evolving landform using pedogenetic processes such as physical weathering and armouring.
To assess the reliability of SSSPAM, model predictions at 100 and 10000 years were compared with SIBERIA predictions at the same times. During the long term (10000yr) simulation the effect of armouring and weathering on the landform evolution was also assessed. The results obtained from these different simulations were compared and contrasted. Comparison of the short term simulations revealed that SSSPAM results compare well with the simulation results of the more established SIBERIA model. Long term simulation showed that SSSPAM simulation results also compares well with SIBERIA simulations while the erosion rates predicted by both models are close to the land denudation rates measured in the field. The soil profile characteristics and channel forms simulated by SSSPAM long term simulations were examined using several landform cross-sections. This analyses revealed that SSSPAM produces deep incised channels with very low soil thickness in upper reaches of the catchment and shallow channels with relatively thick soil layers in the lower reaches of the catchment. These SSSPAM simulated channels match well with the channel forms and distribution of bedrock channels and alluvial channels observed in the field. The analysis of the catchment cross-sections also showed that SSSPAM is capable of reproducing complex subsurface soil evolution and stratification and spatial variability of soil profile characteristics typically observed in the field.
How to cite: Welivitiya, W. D. D. P., Willgoose, G., and Hancock, G.: Evaluating the stability and evolution of a proposed post mining landform., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8569, https://doi.org/10.5194/egusphere-egu21-8569, 2021.
EGU21-8558 | vPICO presentations | GM2.10
Using Landscape Evolution Models to assess the long-term erosional stability of tailings damsGreg Hancock
Tailings are a by product of mining and the processing of minerals. Tailings are generally highly erodible as they have a fine particle size. They can also contain elevated concentrations of unwanted minerals and process chemicals. Consequently, if released to the environment they can be a significant environmental problem. There have been several high profile cases which have highlighted the human and environmental risk of tailings. A common way to manage tailings is to store them in ‘tailings dams’ where they will remain in perpetuity. There has been little investigation of the long-term erosional behaviour of a tailings dams. Computer based Landscape Evolution Models (LEMs) can provide insight into these new geomorphological entities. LEMS provide information on erosion rates, type of erosion and where erosion is likely to occur and can provide guidance on long-term behaviour. Here a LEM is used to assess tailings dam designs using a range of different surface covers and climates. The modelling and methods here provide a template for tailings dam assessment at other sites globally. The methods here will improve tailings dam design and reduce environmental risk.
How to cite: Hancock, G.: Using Landscape Evolution Models to assess the long-term erosional stability of tailings dams, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8558, https://doi.org/10.5194/egusphere-egu21-8558, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Tailings are a by product of mining and the processing of minerals. Tailings are generally highly erodible as they have a fine particle size. They can also contain elevated concentrations of unwanted minerals and process chemicals. Consequently, if released to the environment they can be a significant environmental problem. There have been several high profile cases which have highlighted the human and environmental risk of tailings. A common way to manage tailings is to store them in ‘tailings dams’ where they will remain in perpetuity. There has been little investigation of the long-term erosional behaviour of a tailings dams. Computer based Landscape Evolution Models (LEMs) can provide insight into these new geomorphological entities. LEMS provide information on erosion rates, type of erosion and where erosion is likely to occur and can provide guidance on long-term behaviour. Here a LEM is used to assess tailings dam designs using a range of different surface covers and climates. The modelling and methods here provide a template for tailings dam assessment at other sites globally. The methods here will improve tailings dam design and reduce environmental risk.
How to cite: Hancock, G.: Using Landscape Evolution Models to assess the long-term erosional stability of tailings dams, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8558, https://doi.org/10.5194/egusphere-egu21-8558, 2021.
EGU21-12271 | vPICO presentations | GM2.10
Modelling soil organic matter at long-time and landscape scales.Benjamin Bruneau, Benoit Chauveau, and Julien Coatléven
Understanding and simulating the soil organic matter had become a key challenge to better predict the landscape dynamic and its evolution. Although numerical modelling developments already integrate soil organic matter to improve agricultural practices at field or plot scales, additional work needs to be carried out to describe the landscape evolution over hundreds to thousands of years.
We aim to identify and quantify the processes associated to organic matter cycle that take part in landscape long-term evolution. We complete a reference sediment transport model designed for large scale evolution by adding some physical considerations relative to organic matter behaviour. The main developments concern:
- Organic matter productivity and its export to soils
- Organic matter evolution and degradation along soil profile and during transport
- Rock and regolith compartments with different lithologies and compositions
- Weathering and erosion
In this presentation, we explore the strengths and limits of this model designed to address a wide variety of questions in various settings. We also discuss the results and assess the validity of this approach considering availability of long-term sedimentary records.
How to cite: Bruneau, B., Chauveau, B., and Coatléven, J.: Modelling soil organic matter at long-time and landscape scales., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12271, https://doi.org/10.5194/egusphere-egu21-12271, 2021.
Understanding and simulating the soil organic matter had become a key challenge to better predict the landscape dynamic and its evolution. Although numerical modelling developments already integrate soil organic matter to improve agricultural practices at field or plot scales, additional work needs to be carried out to describe the landscape evolution over hundreds to thousands of years.
We aim to identify and quantify the processes associated to organic matter cycle that take part in landscape long-term evolution. We complete a reference sediment transport model designed for large scale evolution by adding some physical considerations relative to organic matter behaviour. The main developments concern:
- Organic matter productivity and its export to soils
- Organic matter evolution and degradation along soil profile and during transport
- Rock and regolith compartments with different lithologies and compositions
- Weathering and erosion
In this presentation, we explore the strengths and limits of this model designed to address a wide variety of questions in various settings. We also discuss the results and assess the validity of this approach considering availability of long-term sedimentary records.
How to cite: Bruneau, B., Chauveau, B., and Coatléven, J.: Modelling soil organic matter at long-time and landscape scales., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12271, https://doi.org/10.5194/egusphere-egu21-12271, 2021.
EGU21-15976 | vPICO presentations | GM2.10
Towards a dynamic approach of sequences of coral reef terracesAnne-Morwenn Pastier, Luca Malatesta, Kimberly Huppert, and Denovan Chauveau
Sequences of coral reef terraces result from the interplay between biogenic and clastic sedimentary production, relative sea level (RSL) variations, wave erosion and tectonic forcing. Reefal sequences are gold standard proxies for paleo-sea level and tectonic reconstructions, but their contribution is usually restricted to a bijective approach, correlating the single elevation and age of their inner edge to single sea level stands or coseismic offsets, and reciprocally. The increase of available data, such as coral datings and high resolution topography revealed major deviations from this bijective approach (corals from a single MIS on several terraces, and conversely, or MIS highstands not represented in a sequence).
The Cape Laundi sequence, Sumba island, Indonesia, demonstrates such deviations, with outcrops of corals from MIS 5e on as many as three terraces instead of a single terrace as commonly expected. A preliminar numerical model of coral reef terrace profile has been developed, integrating reef growth, wave erosion, RSL variations and tectonic deformation. The interplay between reef growth rate, tectonic displacements and RSL variations provides a plausible explanation for these numerous occurrences. The low growth rate of this reef appears to prevent coral from saturating the accommodation space generated during sea level transgression, leading to the preservation of drowned platforms and reefal construction of similar age during regressions.
Preliminary results from numerical modeling reveal complex feedbacks between the processes shaping these morphologies. Tectonic deformation has a major influence on reef development, by favoring reef preservation at high uplift rates and controlling the available accommodation space for reef growth.. By taking into account the numerous feedbacks controlling reef morphology, we can investigate the significance of RSL variations, continuous and punctual rock uplift, biogenic activity, and clastic inputs on coral terrace morphology and chronostratigraphy. Our approach can bring crucial constraints to the rates and frequency of RSL variations. To do so, we further develop our numerical model in order to provide more robust insights on the controls of reefal sequences morphologies.
How to cite: Pastier, A.-M., Malatesta, L., Huppert, K., and Chauveau, D.: Towards a dynamic approach of sequences of coral reef terraces, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15976, https://doi.org/10.5194/egusphere-egu21-15976, 2021.
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Sequences of coral reef terraces result from the interplay between biogenic and clastic sedimentary production, relative sea level (RSL) variations, wave erosion and tectonic forcing. Reefal sequences are gold standard proxies for paleo-sea level and tectonic reconstructions, but their contribution is usually restricted to a bijective approach, correlating the single elevation and age of their inner edge to single sea level stands or coseismic offsets, and reciprocally. The increase of available data, such as coral datings and high resolution topography revealed major deviations from this bijective approach (corals from a single MIS on several terraces, and conversely, or MIS highstands not represented in a sequence).
The Cape Laundi sequence, Sumba island, Indonesia, demonstrates such deviations, with outcrops of corals from MIS 5e on as many as three terraces instead of a single terrace as commonly expected. A preliminar numerical model of coral reef terrace profile has been developed, integrating reef growth, wave erosion, RSL variations and tectonic deformation. The interplay between reef growth rate, tectonic displacements and RSL variations provides a plausible explanation for these numerous occurrences. The low growth rate of this reef appears to prevent coral from saturating the accommodation space generated during sea level transgression, leading to the preservation of drowned platforms and reefal construction of similar age during regressions.
Preliminary results from numerical modeling reveal complex feedbacks between the processes shaping these morphologies. Tectonic deformation has a major influence on reef development, by favoring reef preservation at high uplift rates and controlling the available accommodation space for reef growth.. By taking into account the numerous feedbacks controlling reef morphology, we can investigate the significance of RSL variations, continuous and punctual rock uplift, biogenic activity, and clastic inputs on coral terrace morphology and chronostratigraphy. Our approach can bring crucial constraints to the rates and frequency of RSL variations. To do so, we further develop our numerical model in order to provide more robust insights on the controls of reefal sequences morphologies.
How to cite: Pastier, A.-M., Malatesta, L., Huppert, K., and Chauveau, D.: Towards a dynamic approach of sequences of coral reef terraces, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15976, https://doi.org/10.5194/egusphere-egu21-15976, 2021.
EGU21-607 | vPICO presentations | GM2.10
Steady-state valley width revealed by alluvial terrace sequencesStefanie Tofelde, Aaron Bufe, and Jens M. Turowski
Lateral erosion by rivers drives valley widening and controls valley-bottom width. The current lack of a comprehensive valley-widening model complicates the reproduction of the full range of valley shapes that we find in nature as well as the prediction of valley evolution under different climatic and tectonic boundary conditions. Field data have shown that water discharge and valley wall lithology control lateral erosion rates. However, order-of magnitude variations in valley width formed in uniform lithology and under similar discharge conditions suggest additional, so far unquantified controls on valley width.
Fluvial terrace sequences offer an opportunity to study valley-width evolution under comparable discharge and lithologic conditions. Alluvial terraces are composed of flat surfaces and steep walls carved into previously deposited river sediments. They form where a river alternates between phases of lateral valley widening by lateral planation and vertical incision and terrace formation. In order to form an entire terrace staircase, such alternations have to repeat and many Quaternary terrace staircases are interpreted to be driven by cyclic climate changes. Because Quaternary climate cycles have had comparable amplitudes and durations, individual surfaces in paired climate-driven terrace sequences preserve the widths of valleys that have formed under similar discharge conditions, lithologies and over comparable time-intervals. We use a global compilation of 16 climatically formed alluvial terrace sequences to investigate controls on valley width.
Between 90 and 99% of the variance in valley width can be explained by a linear relationship of the width with the total valley depth. Hence, at least one of the missing controls on valley width must scale (close to) linearly with valley depth. Ruling-out a preservation bias and a number of parameters that are unrelated to valley depth, we propose a model that relates valley width to a competition between the sediment supplied from valley walls and the river’s capacity to rework sediment, such that a lateral sediment-flux steady state is reached. According to our model the valley width-depth relationship is controlled by (1) the horizontal hillslope-erosion rate, (2) the lateral sediment-transport capacity of the river and (3) the valley-width which forms in the absence of lateral-sediment input. Hence, the model allows to predict valley width when all of the above parameters are quantified in the field. Alternatively, any of the three parameters can be predicted when valley width is measured. The new model is able to reproduce the first-order trend observed in terrace-derived valley widths and it can explain the evolution of paired terrace sequences, which has so far been a major challenge.
How to cite: Tofelde, S., Bufe, A., and Turowski, J. M.: Steady-state valley width revealed by alluvial terrace sequences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-607, https://doi.org/10.5194/egusphere-egu21-607, 2021.
Lateral erosion by rivers drives valley widening and controls valley-bottom width. The current lack of a comprehensive valley-widening model complicates the reproduction of the full range of valley shapes that we find in nature as well as the prediction of valley evolution under different climatic and tectonic boundary conditions. Field data have shown that water discharge and valley wall lithology control lateral erosion rates. However, order-of magnitude variations in valley width formed in uniform lithology and under similar discharge conditions suggest additional, so far unquantified controls on valley width.
Fluvial terrace sequences offer an opportunity to study valley-width evolution under comparable discharge and lithologic conditions. Alluvial terraces are composed of flat surfaces and steep walls carved into previously deposited river sediments. They form where a river alternates between phases of lateral valley widening by lateral planation and vertical incision and terrace formation. In order to form an entire terrace staircase, such alternations have to repeat and many Quaternary terrace staircases are interpreted to be driven by cyclic climate changes. Because Quaternary climate cycles have had comparable amplitudes and durations, individual surfaces in paired climate-driven terrace sequences preserve the widths of valleys that have formed under similar discharge conditions, lithologies and over comparable time-intervals. We use a global compilation of 16 climatically formed alluvial terrace sequences to investigate controls on valley width.
Between 90 and 99% of the variance in valley width can be explained by a linear relationship of the width with the total valley depth. Hence, at least one of the missing controls on valley width must scale (close to) linearly with valley depth. Ruling-out a preservation bias and a number of parameters that are unrelated to valley depth, we propose a model that relates valley width to a competition between the sediment supplied from valley walls and the river’s capacity to rework sediment, such that a lateral sediment-flux steady state is reached. According to our model the valley width-depth relationship is controlled by (1) the horizontal hillslope-erosion rate, (2) the lateral sediment-transport capacity of the river and (3) the valley-width which forms in the absence of lateral-sediment input. Hence, the model allows to predict valley width when all of the above parameters are quantified in the field. Alternatively, any of the three parameters can be predicted when valley width is measured. The new model is able to reproduce the first-order trend observed in terrace-derived valley widths and it can explain the evolution of paired terrace sequences, which has so far been a major challenge.
How to cite: Tofelde, S., Bufe, A., and Turowski, J. M.: Steady-state valley width revealed by alluvial terrace sequences, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-607, https://doi.org/10.5194/egusphere-egu21-607, 2021.
EGU21-12835 | vPICO presentations | GM2.10
Autogenic knickpoints initiation related to downstream river width dynamic: Experimental approach.Léopold de Lavaissière, Stéphane Bonnet, and Philippe Davy
Upward propagation of knickpoints is known to reflect landscape disequilibrium in response to changes in boundary conditions such as tectonics, climate or base-level. However, it is suggested that some knickpoints may also form autogenically, solely from river system intrinsic process. Genesis and dynamics of such autogenic knickpoints were explored here through basin-scaled experimental modeling. The experiment consists on a 1.00 x 0.55 m box filled with silica grains, where one of the short sides goes down steadily as constant base-level fall while homogenous precipitation is applied on top of the surface. The experimental topography is digitized on a 5 min step basis to produce 1 mm squared grid DEMs thereafter used to extract hydraulic information such as water depth, water discharge and shear stress with the hydrodynamic model Floodos (Davy et al., 2017).
We present here results from three experiments performed with similar precipitation rate but different rates of base-level fall. For the three experiments, knickpoints regularly initiate near catchment’s outlet and propagate through landscapes throughout the duration of experiments, despite steady boundary conditions. We show that their initiation near the outlet occurs from cycles in river narrowing/widening. River narrowing leads to an increase in shear stress and a knickpoint initiation. Once the knickpoint propagate upward, the river widens and the shear stress decreases, down to a new cycle of river narrowing, increasing shear stress and knickpoint initiation. We also show that the propagation rate of such autogenic knickpoints is not consistent with a stream power-based model, as it does not decrease monotonously through the experimental landscape. We propose a new model of knickpoints generation and propagation related to downstream river width dynamic that highlights the need to better consider and understand autogenic processes in landscapes and surface process models.
Davy, P., Croissant, T., Lague, D., 2017. A precipiton method to calculate river hydrodynamics, with applications to flood prediction, landscape evolution models, and braiding instabilities: A Precipiton Method for River Dynamics. Journal of Geophysical Research: Earth Surface 122, 1491–1512.
How to cite: de Lavaissière, L., Bonnet, S., and Davy, P.: Autogenic knickpoints initiation related to downstream river width dynamic: Experimental approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12835, https://doi.org/10.5194/egusphere-egu21-12835, 2021.
Upward propagation of knickpoints is known to reflect landscape disequilibrium in response to changes in boundary conditions such as tectonics, climate or base-level. However, it is suggested that some knickpoints may also form autogenically, solely from river system intrinsic process. Genesis and dynamics of such autogenic knickpoints were explored here through basin-scaled experimental modeling. The experiment consists on a 1.00 x 0.55 m box filled with silica grains, where one of the short sides goes down steadily as constant base-level fall while homogenous precipitation is applied on top of the surface. The experimental topography is digitized on a 5 min step basis to produce 1 mm squared grid DEMs thereafter used to extract hydraulic information such as water depth, water discharge and shear stress with the hydrodynamic model Floodos (Davy et al., 2017).
We present here results from three experiments performed with similar precipitation rate but different rates of base-level fall. For the three experiments, knickpoints regularly initiate near catchment’s outlet and propagate through landscapes throughout the duration of experiments, despite steady boundary conditions. We show that their initiation near the outlet occurs from cycles in river narrowing/widening. River narrowing leads to an increase in shear stress and a knickpoint initiation. Once the knickpoint propagate upward, the river widens and the shear stress decreases, down to a new cycle of river narrowing, increasing shear stress and knickpoint initiation. We also show that the propagation rate of such autogenic knickpoints is not consistent with a stream power-based model, as it does not decrease monotonously through the experimental landscape. We propose a new model of knickpoints generation and propagation related to downstream river width dynamic that highlights the need to better consider and understand autogenic processes in landscapes and surface process models.
Davy, P., Croissant, T., Lague, D., 2017. A precipiton method to calculate river hydrodynamics, with applications to flood prediction, landscape evolution models, and braiding instabilities: A Precipiton Method for River Dynamics. Journal of Geophysical Research: Earth Surface 122, 1491–1512.
How to cite: de Lavaissière, L., Bonnet, S., and Davy, P.: Autogenic knickpoints initiation related to downstream river width dynamic: Experimental approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12835, https://doi.org/10.5194/egusphere-egu21-12835, 2021.
EGU21-9984 | vPICO presentations | GM2.10
Influence of discharge variability on denudation rates and relief : example from the south-eastern margin of the Massif Central, FranceClement Desormeaux, Vincent Godard, Dimitri Lague, Lucilla Benedetti, Jules Fleury, and Guilaume Duclaux
The evolution of continental relief results from the combined action of tectonic and climatic forcings. These processes do not act continuously but often through punctual events (earthquakes, major floods, landslides) whose integrated action over time (100 Kyr to Myr) leads to the formation of landscapes. The distribution of these extreme events is often described by statistical functions involving power-law relationships between frequency and magnitude, which, coupled with the non-linearity of the geomorphological response and threshold effects for the activation of erosion agents, leads to a complex and often poorly understood relief dynamics.
Studying the influence of discharge variability helps to better constrain river incision and long-term relief evolution. The south-eastern margin of the Massif Central (France) is a very interesting target for such investigations because it presents episodes of very intense precipitation focused on the relief resulting in marked differences in the statistical discharges distributions across the landscape. Some theoretical river incision models incorporate such variability (Lague et al., 2005) but they have been confronted with real data only in a limited number of cases (DiBiase et al., 2011; Scherler et al., 2017; Campfort et al., 2020). Here we test these models in the Massif Central area and in particular on Cévennes, Ardèche and Margeride mountains by quantifying denudation rates using cosmogenic nuclides (10Be), characterizing discharges variability and performing morphological analysis on longitudinal rivers profiles.
The analysis of 326 river gauging stations allow us to observe a strong gradient in discharge variability from the external SE border to the interior of the Massif Central. The 10Be concentrations measured from river sediments in 36 catchments imply a large variation of denudation rates between 29 mm/kyr and 126 mm/kyr. We compare these denudation rates with the spatial distribution of mean annual precipitations, local relief, slope and concavity index, and also integrate all the observations in the frame of a stochastic threshold incision model. Our results confirm the complex model predictions of non-linear relationships between mean denudation rates and the channel steepness index and their dependence on hydrological variability and run-off.
key-words : extreme events, stochastic threshold incision model, denudation rates, discharge variability, morphometric parameters, Massif Central
How to cite: Desormeaux, C., Godard, V., Lague, D., Benedetti, L., Fleury, J., and Duclaux, G.: Influence of discharge variability on denudation rates and relief : example from the south-eastern margin of the Massif Central, France, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9984, https://doi.org/10.5194/egusphere-egu21-9984, 2021.
The evolution of continental relief results from the combined action of tectonic and climatic forcings. These processes do not act continuously but often through punctual events (earthquakes, major floods, landslides) whose integrated action over time (100 Kyr to Myr) leads to the formation of landscapes. The distribution of these extreme events is often described by statistical functions involving power-law relationships between frequency and magnitude, which, coupled with the non-linearity of the geomorphological response and threshold effects for the activation of erosion agents, leads to a complex and often poorly understood relief dynamics.
Studying the influence of discharge variability helps to better constrain river incision and long-term relief evolution. The south-eastern margin of the Massif Central (France) is a very interesting target for such investigations because it presents episodes of very intense precipitation focused on the relief resulting in marked differences in the statistical discharges distributions across the landscape. Some theoretical river incision models incorporate such variability (Lague et al., 2005) but they have been confronted with real data only in a limited number of cases (DiBiase et al., 2011; Scherler et al., 2017; Campfort et al., 2020). Here we test these models in the Massif Central area and in particular on Cévennes, Ardèche and Margeride mountains by quantifying denudation rates using cosmogenic nuclides (10Be), characterizing discharges variability and performing morphological analysis on longitudinal rivers profiles.
The analysis of 326 river gauging stations allow us to observe a strong gradient in discharge variability from the external SE border to the interior of the Massif Central. The 10Be concentrations measured from river sediments in 36 catchments imply a large variation of denudation rates between 29 mm/kyr and 126 mm/kyr. We compare these denudation rates with the spatial distribution of mean annual precipitations, local relief, slope and concavity index, and also integrate all the observations in the frame of a stochastic threshold incision model. Our results confirm the complex model predictions of non-linear relationships between mean denudation rates and the channel steepness index and their dependence on hydrological variability and run-off.
key-words : extreme events, stochastic threshold incision model, denudation rates, discharge variability, morphometric parameters, Massif Central
How to cite: Desormeaux, C., Godard, V., Lague, D., Benedetti, L., Fleury, J., and Duclaux, G.: Influence of discharge variability on denudation rates and relief : example from the south-eastern margin of the Massif Central, France, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9984, https://doi.org/10.5194/egusphere-egu21-9984, 2021.
EGU21-8271 | vPICO presentations | GM2.10
Progressive landscape transformation from a fluvial to a glacial topographyMoritz Liebl, Jörg Robl, David Egholm, Günther Prasicek, Kurt Stüwe, Gerit Gradwohl, and Stefan Hergarten
Mid-latitude mountain ranges such as the Eastern Alps are characterized by a strong topographic imprint of Pleistocene glaciations. The characteristic geometry of glacial landforms has been quantified in various ways, but studies about the evolution of glacial landscape metrics are lacking. However, such information is needed to interpret the evolutionary state of glacial topography.
By employing a landscape evolution model for cold climate processes, we trace the fluvial-to-glacial transformation of a synthetic landscape. Our simulations inspired by alpine glaciations of mid-latitude mountain ranges with peaks and ridges towering above the glacier network lead to a general increase in relief. This is expressed as the formation of overdeepened valleys with steepened flanks. Overdeepening starts at the glacier front and progressively extends upstream with ongoing glacial erosion.
The topographic signature of the progressively transforming landscape is characterized by an increase of mean channel slopes and its variance. However, above the steep flanks, the initial fluvial topography is persisting. Whereas the initial fluvial mountain range is characterized by a monotonic increase of channel slope with elevation, a transition from increasing to decreasing channel slope with elevation emerges above the equilibrium line altitude where (tributary-)headwalls transition to ridges and summits. This turning point and a high slope variance becomes progressively distinctive with ongoing glacial occupation.
By comparing landscape metrics derived from model time series with those of the Eastern Alps, we found that the temporal transition observed in our numerical experiments occur as spatial transition from the fully glaciated western to a minorly glaciated eastern part of the Alps. Thus, slope-elevation plots serve as a diagnostic tool for interpreting the glacial - fluvial influence in mountain landscapes. However, catchments of the unglaciated part of the Eastern Alps show also turning points in their slope-elevation distributions, but the variance of slope is significantly smaller at all elevation levels, when compared to the glaciated part.
How to cite: Liebl, M., Robl, J., Egholm, D., Prasicek, G., Stüwe, K., Gradwohl, G., and Hergarten, S.: Progressive landscape transformation from a fluvial to a glacial topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8271, https://doi.org/10.5194/egusphere-egu21-8271, 2021.
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Mid-latitude mountain ranges such as the Eastern Alps are characterized by a strong topographic imprint of Pleistocene glaciations. The characteristic geometry of glacial landforms has been quantified in various ways, but studies about the evolution of glacial landscape metrics are lacking. However, such information is needed to interpret the evolutionary state of glacial topography.
By employing a landscape evolution model for cold climate processes, we trace the fluvial-to-glacial transformation of a synthetic landscape. Our simulations inspired by alpine glaciations of mid-latitude mountain ranges with peaks and ridges towering above the glacier network lead to a general increase in relief. This is expressed as the formation of overdeepened valleys with steepened flanks. Overdeepening starts at the glacier front and progressively extends upstream with ongoing glacial erosion.
The topographic signature of the progressively transforming landscape is characterized by an increase of mean channel slopes and its variance. However, above the steep flanks, the initial fluvial topography is persisting. Whereas the initial fluvial mountain range is characterized by a monotonic increase of channel slope with elevation, a transition from increasing to decreasing channel slope with elevation emerges above the equilibrium line altitude where (tributary-)headwalls transition to ridges and summits. This turning point and a high slope variance becomes progressively distinctive with ongoing glacial occupation.
By comparing landscape metrics derived from model time series with those of the Eastern Alps, we found that the temporal transition observed in our numerical experiments occur as spatial transition from the fully glaciated western to a minorly glaciated eastern part of the Alps. Thus, slope-elevation plots serve as a diagnostic tool for interpreting the glacial - fluvial influence in mountain landscapes. However, catchments of the unglaciated part of the Eastern Alps show also turning points in their slope-elevation distributions, but the variance of slope is significantly smaller at all elevation levels, when compared to the glaciated part.
How to cite: Liebl, M., Robl, J., Egholm, D., Prasicek, G., Stüwe, K., Gradwohl, G., and Hergarten, S.: Progressive landscape transformation from a fluvial to a glacial topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8271, https://doi.org/10.5194/egusphere-egu21-8271, 2021.
EGU21-9392 | vPICO presentations | GM2.10
Dynamic modelling framework to track sediment provenance and solve lakes in long-term landscape evolution modelsBoris Gailleton, Luca Malatesta, Jean Braun, and Guillaume Cordonnier
Many laws have been developed to describe the different aspects of landscape evolution at large spatial and temporal scales. Natural landscapes have heterogeneous properties (lithologies, climates, tectonics, etc.) that are associated with multiple coexisting processes. In turn, this can demand different mathematical expressions to model landscape evolution as a function of time and or space. Landscape Evolution Models are mostly designed to facilitate the combination of different landscape-wide laws in a plug-and-play way and many frameworks are being developed in this aim. However, most current frameworks cannot capture important landscape processes such as lake dynamics and full sediment tracing because they are optimized for speed and handle fluxes separately. Several processes require information from more than the immediate neighboring cells within a time step and demand an integrated knowledge from the entire upstream trajectory. Lakes for example require knowledge of all upstream water and sediment fluxes to be filled. These can only be known if all the laws controlling those have been processed. Tackling these situation with a grid logic requires substantial amount of numerical refactoring from existing models.
We present an alternative method to tackle landscape evolution modelling in heterogeneous landscapes with a framework inspired from Lagrangian and cellular automaton methods. Our framework only relies on the assumption that upstream nodes needs to be processed before the downstream ones, including lakes with outlets, in order to process all selected governing equations on a pixel-to-pixel basis. This way, we ensure that the true content of sediment and water fluxes can be known and tracked at any points. We first utilise graph theory to (i) find the most comprehensive path to reroute water through depressions and (ii) determine a generic multiple flow topological order (any node is processed after all potential upstream ones). Particles that register and track all fluxes simultaneously can then "roll" on the landscape and merge between each other while interacting with the grid.
This formulation makes possible a number of generic features. (i) The laws can be dynamically adapted to the environment (e.g. switching from single to multiple flow function of water content, adapting erodibility function of the sediment composition and quantity), (ii) Depressions can be explicitly managed, filled (or not) and separated from the rest of the landscape (e.g. sedimentation or evaporation in lakes) as a function function of inputted fluxes and parameters, (iii) full provenance, transport time, and deposition tracking as the particle can always keep in memory where the fluxes are from and in what proportions. In this contribution, we demonstrate the impact the importance of considering these additional elements in landscape evolution. In particular, lake dynamic can significantly impact the long-term signal propagation from source to sink.
How to cite: Gailleton, B., Malatesta, L., Braun, J., and Cordonnier, G.: Dynamic modelling framework to track sediment provenance and solve lakes in long-term landscape evolution models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9392, https://doi.org/10.5194/egusphere-egu21-9392, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Many laws have been developed to describe the different aspects of landscape evolution at large spatial and temporal scales. Natural landscapes have heterogeneous properties (lithologies, climates, tectonics, etc.) that are associated with multiple coexisting processes. In turn, this can demand different mathematical expressions to model landscape evolution as a function of time and or space. Landscape Evolution Models are mostly designed to facilitate the combination of different landscape-wide laws in a plug-and-play way and many frameworks are being developed in this aim. However, most current frameworks cannot capture important landscape processes such as lake dynamics and full sediment tracing because they are optimized for speed and handle fluxes separately. Several processes require information from more than the immediate neighboring cells within a time step and demand an integrated knowledge from the entire upstream trajectory. Lakes for example require knowledge of all upstream water and sediment fluxes to be filled. These can only be known if all the laws controlling those have been processed. Tackling these situation with a grid logic requires substantial amount of numerical refactoring from existing models.
We present an alternative method to tackle landscape evolution modelling in heterogeneous landscapes with a framework inspired from Lagrangian and cellular automaton methods. Our framework only relies on the assumption that upstream nodes needs to be processed before the downstream ones, including lakes with outlets, in order to process all selected governing equations on a pixel-to-pixel basis. This way, we ensure that the true content of sediment and water fluxes can be known and tracked at any points. We first utilise graph theory to (i) find the most comprehensive path to reroute water through depressions and (ii) determine a generic multiple flow topological order (any node is processed after all potential upstream ones). Particles that register and track all fluxes simultaneously can then "roll" on the landscape and merge between each other while interacting with the grid.
This formulation makes possible a number of generic features. (i) The laws can be dynamically adapted to the environment (e.g. switching from single to multiple flow function of water content, adapting erodibility function of the sediment composition and quantity), (ii) Depressions can be explicitly managed, filled (or not) and separated from the rest of the landscape (e.g. sedimentation or evaporation in lakes) as a function function of inputted fluxes and parameters, (iii) full provenance, transport time, and deposition tracking as the particle can always keep in memory where the fluxes are from and in what proportions. In this contribution, we demonstrate the impact the importance of considering these additional elements in landscape evolution. In particular, lake dynamic can significantly impact the long-term signal propagation from source to sink.
How to cite: Gailleton, B., Malatesta, L., Braun, J., and Cordonnier, G.: Dynamic modelling framework to track sediment provenance and solve lakes in long-term landscape evolution models, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9392, https://doi.org/10.5194/egusphere-egu21-9392, 2021.
EGU21-10554 | vPICO presentations | GM2.10
Investigating the Response of Tectonic Loading in the Himalayas on the Peripheral Forebulge through Drainage Network AnalysisParv Kasana, Vimal Singh, and Rahul Devrani
Drainage divide migration is a conspicuous natural process through which a landscape evolves. In response to a forced climatic and tectonic disturbance, susceptible river networks transfer the transient signals to the entire river basin, which results in an incision or aggradation. The Himalayan orogeny and subduction of the Indian plate have resulted in an upward flexure in the Indian lithosphere known as a peripheral forebulge. A forebulge can flexurally uplift and migrate following the variation in tectonic load. The emergence of the central Indian plateau is a consequence of the upwarping of the Indian lithosphere (Bilham et al. 2003). In this work, we are trying to assess the drainage network dynamics between the Narmada and Ganga river systems, which drain the uplifted central Indian plateau. We have calculated the Chi(χ) metrics, steepness index (Ksn), knickpoints for the channels in the study area. We have generated Topographic swath profiles to analyze the topographic variations on the plateau. It has been observed from the results that the rivers in the study area lack dynamic equilibrium, and river capturing is an evident response to the perturbations. Our analysis shows that the Narmada River tributaries are gaining drainage area and aggressing Northwards by capturing adjacent Ganga river tributaries. The field observations show a variation in the surface slope and presence of knickpoints (waterfalls) along the "aggressor" drainages. We propose a model to show a correlation between the tectonic loading of Himalayas, movement of forebulge, and its feedback to the river systems present on the forebulge.
How to cite: Kasana, P., Singh, V., and Devrani, R.: Investigating the Response of Tectonic Loading in the Himalayas on the Peripheral Forebulge through Drainage Network Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10554, https://doi.org/10.5194/egusphere-egu21-10554, 2021.
Drainage divide migration is a conspicuous natural process through which a landscape evolves. In response to a forced climatic and tectonic disturbance, susceptible river networks transfer the transient signals to the entire river basin, which results in an incision or aggradation. The Himalayan orogeny and subduction of the Indian plate have resulted in an upward flexure in the Indian lithosphere known as a peripheral forebulge. A forebulge can flexurally uplift and migrate following the variation in tectonic load. The emergence of the central Indian plateau is a consequence of the upwarping of the Indian lithosphere (Bilham et al. 2003). In this work, we are trying to assess the drainage network dynamics between the Narmada and Ganga river systems, which drain the uplifted central Indian plateau. We have calculated the Chi(χ) metrics, steepness index (Ksn), knickpoints for the channels in the study area. We have generated Topographic swath profiles to analyze the topographic variations on the plateau. It has been observed from the results that the rivers in the study area lack dynamic equilibrium, and river capturing is an evident response to the perturbations. Our analysis shows that the Narmada River tributaries are gaining drainage area and aggressing Northwards by capturing adjacent Ganga river tributaries. The field observations show a variation in the surface slope and presence of knickpoints (waterfalls) along the "aggressor" drainages. We propose a model to show a correlation between the tectonic loading of Himalayas, movement of forebulge, and its feedback to the river systems present on the forebulge.
How to cite: Kasana, P., Singh, V., and Devrani, R.: Investigating the Response of Tectonic Loading in the Himalayas on the Peripheral Forebulge through Drainage Network Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10554, https://doi.org/10.5194/egusphere-egu21-10554, 2021.
EGU21-8875 | vPICO presentations | GM2.10
3D lithological structure in a steady state model drives divide migrationEmma Graf, Simon Mudd, Florian Kober, Angela Landgraf, and Andreas Ludwig
Predicting future relief is a longstanding challenge in the field of geomorphology. Past denudation and incision rates can be reconstructed and modelled from field data such as thermochronometers, cosmogenic nuclides or optically stimulated luminescence, whereas future rates are then, by definition, fully unknown. Predicting future landscape evolution is further complicated by the dynamic nature of drainage networks, as well as the necessity of constraining properties such as erodibility in order to make sensible predictions. One of the few constraints available for future landscape properties is the underground stratigraphy imaged by wells or geophysical methods. The 3D rock structure will eventually be exhumed and can be utilised to constrain the future states of model simulations.
In this contribution, we present a landscape evolution model capable of ingesting 3D lithologic information and adapting to alternative channel networks, and demonstrate it using a study area in the Swiss Jura Mountains. The model calculates local relief using steady state solutions of the stream power incision model, and also quantifies hillslope relief using a very simple critical slope gradient where hillslope angles are set to a critical value on pixels that have a small drainage area. Further, drainage divides are allowed to migrate to minimize sharp breaks in relief across drainage divides.
We calibrate the values of erodibility, K, for each lithological unit by extracting ranges of apparent K value from the present-day landscape based on drainage area and gradient along the drainage network. This is then further refined by i) using a Monte Carlo approach to create combinations of K based on these ranges, and ii) comparing the real and model landscape for each combination with the aim to minimise the difference between the two. We then run selected model simulations of future base level fall and potential drainage reorganisation events, highlighting the effects of i.) spatially variable erodibility and ii.) lateral changes of the main channel axis on divide migration.
How to cite: Graf, E., Mudd, S., Kober, F., Landgraf, A., and Ludwig, A.: 3D lithological structure in a steady state model drives divide migration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8875, https://doi.org/10.5194/egusphere-egu21-8875, 2021.
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Predicting future relief is a longstanding challenge in the field of geomorphology. Past denudation and incision rates can be reconstructed and modelled from field data such as thermochronometers, cosmogenic nuclides or optically stimulated luminescence, whereas future rates are then, by definition, fully unknown. Predicting future landscape evolution is further complicated by the dynamic nature of drainage networks, as well as the necessity of constraining properties such as erodibility in order to make sensible predictions. One of the few constraints available for future landscape properties is the underground stratigraphy imaged by wells or geophysical methods. The 3D rock structure will eventually be exhumed and can be utilised to constrain the future states of model simulations.
In this contribution, we present a landscape evolution model capable of ingesting 3D lithologic information and adapting to alternative channel networks, and demonstrate it using a study area in the Swiss Jura Mountains. The model calculates local relief using steady state solutions of the stream power incision model, and also quantifies hillslope relief using a very simple critical slope gradient where hillslope angles are set to a critical value on pixels that have a small drainage area. Further, drainage divides are allowed to migrate to minimize sharp breaks in relief across drainage divides.
We calibrate the values of erodibility, K, for each lithological unit by extracting ranges of apparent K value from the present-day landscape based on drainage area and gradient along the drainage network. This is then further refined by i) using a Monte Carlo approach to create combinations of K based on these ranges, and ii) comparing the real and model landscape for each combination with the aim to minimise the difference between the two. We then run selected model simulations of future base level fall and potential drainage reorganisation events, highlighting the effects of i.) spatially variable erodibility and ii.) lateral changes of the main channel axis on divide migration.
How to cite: Graf, E., Mudd, S., Kober, F., Landgraf, A., and Ludwig, A.: 3D lithological structure in a steady state model drives divide migration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8875, https://doi.org/10.5194/egusphere-egu21-8875, 2021.
EGU21-9758 | vPICO presentations | GM2.10
Climatic and Biotic Controls on Topographic Asymmetry at the Global ScaleTaylor Smith and Bodo Bookhagen
Insolation differences play a primary role in controlling microclimate and vegetation cover, which together influence the development of topography. Topographic asymmetry (TA), or slope differences between terrain aspects, has been well documented in small-scale, field-based, and modeling studies. Here we combine a suite of environmental (e.g., vegetation, temperature, solar insolation) and topographic (e.g., elevation, drainage network) data to explore the driving mechanisms and markers of TA on a global scale. Using a novel empirical TA analysis method, we find that (1) steeper terrain has higher TA magnitudes, (2) globally, pole-facing terrain is on average steeper than equator-facing terrain, especially in mid-latitude, tectonically quiescent, and vegetated landscapes, and (3) high-elevation and low-temperature regions tend to have terrain steepened towards the equator. We further show that there are distinct differences in climate and vegetation cover across terrain aspects, and that TA is reflected in the size and form of fluvial drainage networks. Our work supports the argument that insolation asymmetries engender differences in local microclimates and vegetation on opposing terrain aspects, which broadly encourage the development of asymmetric topography across a range of lithologic, tectonic, geomorphic, and climatic settings.
How to cite: Smith, T. and Bookhagen, B.: Climatic and Biotic Controls on Topographic Asymmetry at the Global Scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9758, https://doi.org/10.5194/egusphere-egu21-9758, 2021.
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Insolation differences play a primary role in controlling microclimate and vegetation cover, which together influence the development of topography. Topographic asymmetry (TA), or slope differences between terrain aspects, has been well documented in small-scale, field-based, and modeling studies. Here we combine a suite of environmental (e.g., vegetation, temperature, solar insolation) and topographic (e.g., elevation, drainage network) data to explore the driving mechanisms and markers of TA on a global scale. Using a novel empirical TA analysis method, we find that (1) steeper terrain has higher TA magnitudes, (2) globally, pole-facing terrain is on average steeper than equator-facing terrain, especially in mid-latitude, tectonically quiescent, and vegetated landscapes, and (3) high-elevation and low-temperature regions tend to have terrain steepened towards the equator. We further show that there are distinct differences in climate and vegetation cover across terrain aspects, and that TA is reflected in the size and form of fluvial drainage networks. Our work supports the argument that insolation asymmetries engender differences in local microclimates and vegetation on opposing terrain aspects, which broadly encourage the development of asymmetric topography across a range of lithologic, tectonic, geomorphic, and climatic settings.
How to cite: Smith, T. and Bookhagen, B.: Climatic and Biotic Controls on Topographic Asymmetry at the Global Scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9758, https://doi.org/10.5194/egusphere-egu21-9758, 2021.
GM2.11 – From historical images to modern high resolution topography: methods and applications in geosciences
EGU21-13196 | vPICO presentations | GM2.11 | Highlight
Historical Structure From Motion (HSfM): Automated production of high-resolution DEMs from historical aerial photography for long-term geodetic change analysisFriedrich Knuth, David Shean, and Shashank Bhushan
Mountain glaciers have lost significant mass over the past century in response to a globally warming climate. However, on interannual to decadal time scales, many glaciers in Western North America show periods of both advance and retreat. To better understand these systems and their sensitivity to climate forcing, we are generating regional records of glacier surface elevation change from scanned historical film photographs acquired between the 1950s to 1990s. Our results will help constrain projections of future glacier change under different climate scenarios, as well as impacts on downstream water resources and geohazard risk.
Historical image pre-processing and manual ground control point (GCP) selection are time-intensive bottlenecks during traditional SfM processing workflows. We developed an automated photogrammetry processing pipeline (HSfM) to systematically process large archives of vertical aerial film photographs and generate sub-meter resolution digital elevation models (DEMs), without manual GCP selection. We present several case studies for glaciers in the Western North America using photos from the USGS North American Glacier Aerial Photography (NAGAP) and Earth Explorer Aerial Photography Single Frame archives, which differ in terms of available image overlap, survey area extent, and terrain characteristics. Absolute vertical accuracy of <0.5-1.0 m is achieved through iterative closest point (ICP) co-registration over stable bare-ground surfaces between the historical DEMs and modern high-resolution satellite or lidar reference DEMs. We demonstrate the potential for these new DEM records to quantify geodetic glacier mass balance and geomorphological change including moraine deposition, moraine degradation, and sediment redistribution in proglacial areas.
How to cite: Knuth, F., Shean, D., and Bhushan, S.: Historical Structure From Motion (HSfM): Automated production of high-resolution DEMs from historical aerial photography for long-term geodetic change analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13196, https://doi.org/10.5194/egusphere-egu21-13196, 2021.
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Mountain glaciers have lost significant mass over the past century in response to a globally warming climate. However, on interannual to decadal time scales, many glaciers in Western North America show periods of both advance and retreat. To better understand these systems and their sensitivity to climate forcing, we are generating regional records of glacier surface elevation change from scanned historical film photographs acquired between the 1950s to 1990s. Our results will help constrain projections of future glacier change under different climate scenarios, as well as impacts on downstream water resources and geohazard risk.
Historical image pre-processing and manual ground control point (GCP) selection are time-intensive bottlenecks during traditional SfM processing workflows. We developed an automated photogrammetry processing pipeline (HSfM) to systematically process large archives of vertical aerial film photographs and generate sub-meter resolution digital elevation models (DEMs), without manual GCP selection. We present several case studies for glaciers in the Western North America using photos from the USGS North American Glacier Aerial Photography (NAGAP) and Earth Explorer Aerial Photography Single Frame archives, which differ in terms of available image overlap, survey area extent, and terrain characteristics. Absolute vertical accuracy of <0.5-1.0 m is achieved through iterative closest point (ICP) co-registration over stable bare-ground surfaces between the historical DEMs and modern high-resolution satellite or lidar reference DEMs. We demonstrate the potential for these new DEM records to quantify geodetic glacier mass balance and geomorphological change including moraine deposition, moraine degradation, and sediment redistribution in proglacial areas.
How to cite: Knuth, F., Shean, D., and Bhushan, S.: Historical Structure From Motion (HSfM): Automated production of high-resolution DEMs from historical aerial photography for long-term geodetic change analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13196, https://doi.org/10.5194/egusphere-egu21-13196, 2021.
EGU21-139 | vPICO presentations | GM2.11
Using repeat oblique aerial photography and satellite imagery to detect glacial change in the Cordillera Vilcanota, Peru, since 1931Ulrich Kamp, Karina Yager, Elise Arnett, Krysten Bowen, Kate Truitt, Anton Seimon, Tracie Seimon, and Alvaro Ivanoff
Terrestrial and aerial image analysis has proven to be a valuable survey method for documenting terrestrial landscape change related to, for example, biodiversity, urbanization, and environmental services such as land vegetation or forest cover and use, glacier extent, and water resources. Historical oblique aerial photographs offer exceptional opportunities to extend the observational record beyond the period covered by traditional nadir aerial surveys and satellite imagery. Here we apply these methods in the Cordillera Vilcanota of Southern Peru, home to the largest high alpine lake, Sibinacocha, in the Andes, a primary source of the Amazon River. The Shippee-Johnson aerial expedition of 1931 produced oblique photographs of glaciated peaks of the Cordillera Vilcanota. To determine the extent of glacial loss, we compared the 1931 glacier extents with more recent ones derived from satellite imagery analyses using Agisoft Metashape and Pixcavator. The identification of the flight camera positions from 1931 proved to be challenging, since the original photographs come with only rudimentary information. For three test glaciers, the Metashape analysis showed a glacier recession of between 50% and 95% from 1931 to 2018. Preliminary Pixcavator analysis results demonstrated a area decrease of 62% at two glacier termini between 1931 and 2020. Future studies will include repeating the oblique aerial photographs across the Vilcanota and other Andean mountain ranges, and also include ground truth and UAS imagery analysis.
How to cite: Kamp, U., Yager, K., Arnett, E., Bowen, K., Truitt, K., Seimon, A., Seimon, T., and Ivanoff, A.: Using repeat oblique aerial photography and satellite imagery to detect glacial change in the Cordillera Vilcanota, Peru, since 1931, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-139, https://doi.org/10.5194/egusphere-egu21-139, 2021.
Terrestrial and aerial image analysis has proven to be a valuable survey method for documenting terrestrial landscape change related to, for example, biodiversity, urbanization, and environmental services such as land vegetation or forest cover and use, glacier extent, and water resources. Historical oblique aerial photographs offer exceptional opportunities to extend the observational record beyond the period covered by traditional nadir aerial surveys and satellite imagery. Here we apply these methods in the Cordillera Vilcanota of Southern Peru, home to the largest high alpine lake, Sibinacocha, in the Andes, a primary source of the Amazon River. The Shippee-Johnson aerial expedition of 1931 produced oblique photographs of glaciated peaks of the Cordillera Vilcanota. To determine the extent of glacial loss, we compared the 1931 glacier extents with more recent ones derived from satellite imagery analyses using Agisoft Metashape and Pixcavator. The identification of the flight camera positions from 1931 proved to be challenging, since the original photographs come with only rudimentary information. For three test glaciers, the Metashape analysis showed a glacier recession of between 50% and 95% from 1931 to 2018. Preliminary Pixcavator analysis results demonstrated a area decrease of 62% at two glacier termini between 1931 and 2020. Future studies will include repeating the oblique aerial photographs across the Vilcanota and other Andean mountain ranges, and also include ground truth and UAS imagery analysis.
How to cite: Kamp, U., Yager, K., Arnett, E., Bowen, K., Truitt, K., Seimon, A., Seimon, T., and Ivanoff, A.: Using repeat oblique aerial photography and satellite imagery to detect glacial change in the Cordillera Vilcanota, Peru, since 1931, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-139, https://doi.org/10.5194/egusphere-egu21-139, 2021.
EGU21-1476 | vPICO presentations | GM2.11
Development of slope-type debris flows regarding frequencies and magnitudes based on aerial images since 1947 in Horlachtal, AustriaJakob Rom, Florian Haas, Tobias Heckmann, Moritz Altmann, Fabian Fleischer, Camillo Ressl, and Michael Becht
The future development of debris flow processes regarding frequency and magnitude in terms of climate change is currently the subject of intensive research. One reason for this is that datasets that extend over decades are often incomplete and biased towards high magnitude events based on the poor data availability in text records, for example.
Within this study, we investigate the development of slope-type debris flows in Horlachtal, a small catchment (~ 55 km²) within the Stubai Alps, Austria. Here, aerial images are available from 2018 back to 1947, which enables the creation of orthoimages. These allow a detailed mapping of debris flow processes even with smaller magnitudes. The resulting large dataset of debris flow process zones from 1947 to 2018 (10 time steps) can give some hints about the development of the frequencies of slope-type debris flows for the last 71 years. Due to their high spatial resolution and accuracy, two LiDAR datasets from 2006 and 2017 were used to calculate the volumes of debris flow deposits and thus the magnitude of debris flows within this time. Using a volume-area relationship on the base of the LiDAR data, we are able to estimate the volumes of debris flow deposits even for the older time steps, which can give an idea of changes in the magnitude of debris flow deposits for the last 71 years.
The results show a highly active time period between 1990 and 2010 as well as a high number of debris flows between 1953 and 1974. An increasing trend in numbers per year and volume per year is recognizable, but some uncertainties remain due to mapping issues, which include resolution of aerial images, shadow effects, snow cover etc.
How to cite: Rom, J., Haas, F., Heckmann, T., Altmann, M., Fleischer, F., Ressl, C., and Becht, M.: Development of slope-type debris flows regarding frequencies and magnitudes based on aerial images since 1947 in Horlachtal, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1476, https://doi.org/10.5194/egusphere-egu21-1476, 2021.
The future development of debris flow processes regarding frequency and magnitude in terms of climate change is currently the subject of intensive research. One reason for this is that datasets that extend over decades are often incomplete and biased towards high magnitude events based on the poor data availability in text records, for example.
Within this study, we investigate the development of slope-type debris flows in Horlachtal, a small catchment (~ 55 km²) within the Stubai Alps, Austria. Here, aerial images are available from 2018 back to 1947, which enables the creation of orthoimages. These allow a detailed mapping of debris flow processes even with smaller magnitudes. The resulting large dataset of debris flow process zones from 1947 to 2018 (10 time steps) can give some hints about the development of the frequencies of slope-type debris flows for the last 71 years. Due to their high spatial resolution and accuracy, two LiDAR datasets from 2006 and 2017 were used to calculate the volumes of debris flow deposits and thus the magnitude of debris flows within this time. Using a volume-area relationship on the base of the LiDAR data, we are able to estimate the volumes of debris flow deposits even for the older time steps, which can give an idea of changes in the magnitude of debris flow deposits for the last 71 years.
The results show a highly active time period between 1990 and 2010 as well as a high number of debris flows between 1953 and 1974. An increasing trend in numbers per year and volume per year is recognizable, but some uncertainties remain due to mapping issues, which include resolution of aerial images, shadow effects, snow cover etc.
How to cite: Rom, J., Haas, F., Heckmann, T., Altmann, M., Fleischer, F., Ressl, C., and Becht, M.: Development of slope-type debris flows regarding frequencies and magnitudes based on aerial images since 1947 in Horlachtal, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1476, https://doi.org/10.5194/egusphere-egu21-1476, 2021.
EGU21-2791 | vPICO presentations | GM2.11
Structure-from-Motion applied to historical aerial photographs: parameter variability and application on landslide cyclonic evolution on France's La Réunion Island, Indian OceanThomas JB Dewez, Claire Rault, and Bertrand Aunay
Geographical Surveys now distribute online their historical aerial photographs. The batches of digital images, holding the appearance and relief of the forever gone landscape, can be processed with automated Structure-from-Motion (SFM) photogrammetric pipelines. Are the results trustworthy? In this communication, we report the results of exploratory tests performed with Agisoft Metashape on sets of 1978, ~1/27.000, vertical aerial photographs from IGN-France over la Réunion volcanic island in the Indian Ocean. Georeferencing deliberately used ground control points and check points collected on IGN's web mapping portal. Validation was obtained from lidar and photogrammetric acquisition of 2015.
First, our results show that scanned photographs do not strictly map camera coordinates to image coordinates from one file to the next. Photos are slightly shifted and rotated on each scan. The photogrammetric assumption of a single camera per batch of images is thus violated. A preprocessing step, automated with Python, locates fiducials, computes camera principal point, rotates and crops the image file to a unique image reference frame. This feature is absent from Agisoft Metashape when fiducial coordinates are unknown.
Second, in the photogrammetric pipeline, camera calibration parameters are deduced from matched sparse points. The sensitivity of the "align" function was explored. The smallest RMS errors were ±7.03m for 11 ground-control points and ±5.45m for 9 independent check points when setting Align quality to "high" and a 4-parameters camera model using focal length (f), eccentricity (cx, cy), one radial distortion parameter (K1). A higher number of parameters delivered no accuracy improvement and correlated parameters. Intensive random sampling of sparse points subsets conducted to stable estimates of focal length and eccentricity. Improving the robustness of focal length determination would require additional, oblique photographs, which was not the spirit of historical survey design and were never acquired in past surveys.
Third, collecting ground control points on https://geoportail.gouv.fr resulted in digital surface model elevation accuracy within +/- 3.34m (Median Absolute Deviation). Validation was computed on a 2015 lidar digital terrain model at 5m resolution on stable grounds. Scanning artefacts, probably due to variable scanning velocity of the digitizing head, introduced elevation variation stripes in Difference of DEM (DoD), parallel to the scanner direction. This pattern limits the detection of geomorphologically meaningful differences.
Fourth, a DoD between 2015-1978 for the Cirque de Salazie, in the north-east of La Réunion Island, highlighted landsliding masses active some time during the last 37 years and 13 cyclones. Beyond this proof of concept, archive aerial photographs in La Réunion go back until 1949 and covered the island twenty times. This time scale offers a welcome hindsight when producing landslide risk mitigation maps.
This work was published in open-access in
Rault, C., Dewez, T. J. B., and Aunay, B., 2020, Structure-from-Motion processing of aerial archive photographs: sensitivity analyses pave the way for quantifying geomorphological changes since 1978 in la Réunion island, ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci., V-2-2020, 773–780, https://doi.org/10.5194/isprs-annals-V-2-2020-773-2020, 2020.
How to cite: Dewez, T. J., Rault, C., and Aunay, B.: Structure-from-Motion applied to historical aerial photographs: parameter variability and application on landslide cyclonic evolution on France's La Réunion Island, Indian Ocean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2791, https://doi.org/10.5194/egusphere-egu21-2791, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Geographical Surveys now distribute online their historical aerial photographs. The batches of digital images, holding the appearance and relief of the forever gone landscape, can be processed with automated Structure-from-Motion (SFM) photogrammetric pipelines. Are the results trustworthy? In this communication, we report the results of exploratory tests performed with Agisoft Metashape on sets of 1978, ~1/27.000, vertical aerial photographs from IGN-France over la Réunion volcanic island in the Indian Ocean. Georeferencing deliberately used ground control points and check points collected on IGN's web mapping portal. Validation was obtained from lidar and photogrammetric acquisition of 2015.
First, our results show that scanned photographs do not strictly map camera coordinates to image coordinates from one file to the next. Photos are slightly shifted and rotated on each scan. The photogrammetric assumption of a single camera per batch of images is thus violated. A preprocessing step, automated with Python, locates fiducials, computes camera principal point, rotates and crops the image file to a unique image reference frame. This feature is absent from Agisoft Metashape when fiducial coordinates are unknown.
Second, in the photogrammetric pipeline, camera calibration parameters are deduced from matched sparse points. The sensitivity of the "align" function was explored. The smallest RMS errors were ±7.03m for 11 ground-control points and ±5.45m for 9 independent check points when setting Align quality to "high" and a 4-parameters camera model using focal length (f), eccentricity (cx, cy), one radial distortion parameter (K1). A higher number of parameters delivered no accuracy improvement and correlated parameters. Intensive random sampling of sparse points subsets conducted to stable estimates of focal length and eccentricity. Improving the robustness of focal length determination would require additional, oblique photographs, which was not the spirit of historical survey design and were never acquired in past surveys.
Third, collecting ground control points on https://geoportail.gouv.fr resulted in digital surface model elevation accuracy within +/- 3.34m (Median Absolute Deviation). Validation was computed on a 2015 lidar digital terrain model at 5m resolution on stable grounds. Scanning artefacts, probably due to variable scanning velocity of the digitizing head, introduced elevation variation stripes in Difference of DEM (DoD), parallel to the scanner direction. This pattern limits the detection of geomorphologically meaningful differences.
Fourth, a DoD between 2015-1978 for the Cirque de Salazie, in the north-east of La Réunion Island, highlighted landsliding masses active some time during the last 37 years and 13 cyclones. Beyond this proof of concept, archive aerial photographs in La Réunion go back until 1949 and covered the island twenty times. This time scale offers a welcome hindsight when producing landslide risk mitigation maps.
This work was published in open-access in
Rault, C., Dewez, T. J. B., and Aunay, B., 2020, Structure-from-Motion processing of aerial archive photographs: sensitivity analyses pave the way for quantifying geomorphological changes since 1978 in la Réunion island, ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci., V-2-2020, 773–780, https://doi.org/10.5194/isprs-annals-V-2-2020-773-2020, 2020.
How to cite: Dewez, T. J., Rault, C., and Aunay, B.: Structure-from-Motion applied to historical aerial photographs: parameter variability and application on landslide cyclonic evolution on France's La Réunion Island, Indian Ocean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2791, https://doi.org/10.5194/egusphere-egu21-2791, 2021.
EGU21-2952 | vPICO presentations | GM2.11
Below the Mosul Dam Lake. Geomorphological reconstruction of historical fluvial pattern of the Tigris RiverLuca Forti, Andrea Pezzotta, Eleonora Regattieri, Guido Stefano Mariani, Filippo Brandolini, and Andrea Zerboni
Located along the Tigris River in the Kurdistan Region of Iraq (KRI), the Mosul Dam reservoir is the second biggest dam of the Near East, and represents an important water storage for local human activities. The Dam was built between 1981 and 1988 north of the village of Eski Mosul; along this part of the Tigris River several archaeological sites were inundated. Analysis of historical images derived from Declassified Corona satellite acquired between December 1967 and August 1968 reveals seasonal changes of the Tigris riverbed, shifting across the hydrological year from meandering to anastomosing. The geomorphological mapping was carried out on the December 1967 and. in August 1968, Corona images were taken, in order to estimate the modification of several fluvial geomorphological elements such as floodplain and point, middle and longitudinal bars. Here, such evidence is compared with Landsat data collected between the 1990ies and today, in order to detect the first phases of filling of the basin and the control of inherited Tigris channel belt over the reservoir. Moreover, we also noticed an influence of the ancient Tigris course on is recent insertion into the lake. Our work permitted to reconstruct the ancient fluvial landscape below the Mosul Dam Lake, and its evolution in response to seasonal variation of the discharge.
How to cite: Forti, L., Pezzotta, A., Regattieri, E., Mariani, G. S., Brandolini, F., and Zerboni, A.: Below the Mosul Dam Lake. Geomorphological reconstruction of historical fluvial pattern of the Tigris River , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2952, https://doi.org/10.5194/egusphere-egu21-2952, 2021.
Located along the Tigris River in the Kurdistan Region of Iraq (KRI), the Mosul Dam reservoir is the second biggest dam of the Near East, and represents an important water storage for local human activities. The Dam was built between 1981 and 1988 north of the village of Eski Mosul; along this part of the Tigris River several archaeological sites were inundated. Analysis of historical images derived from Declassified Corona satellite acquired between December 1967 and August 1968 reveals seasonal changes of the Tigris riverbed, shifting across the hydrological year from meandering to anastomosing. The geomorphological mapping was carried out on the December 1967 and. in August 1968, Corona images were taken, in order to estimate the modification of several fluvial geomorphological elements such as floodplain and point, middle and longitudinal bars. Here, such evidence is compared with Landsat data collected between the 1990ies and today, in order to detect the first phases of filling of the basin and the control of inherited Tigris channel belt over the reservoir. Moreover, we also noticed an influence of the ancient Tigris course on is recent insertion into the lake. Our work permitted to reconstruct the ancient fluvial landscape below the Mosul Dam Lake, and its evolution in response to seasonal variation of the discharge.
How to cite: Forti, L., Pezzotta, A., Regattieri, E., Mariani, G. S., Brandolini, F., and Zerboni, A.: Below the Mosul Dam Lake. Geomorphological reconstruction of historical fluvial pattern of the Tigris River , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2952, https://doi.org/10.5194/egusphere-egu21-2952, 2021.
EGU21-16371 | vPICO presentations | GM2.11
Using historical aerial imagery to assess multidecadal kinematics and elevation changes. Application to mountain permafrost in the French Alps.Diego Cusicanqui, Antoine Rabatel, Xavier Bodin, Christian Vincent, Emmanuel Thibert, Pierre Allain Duvillard, and André Revil
Glacial and periglacial environments are highly sensitive to climate change, even more in mountain areas where warming is faster and, as a consequence, perennial features of the cryosphere like glaciers and permafrost have been fast evolving in the last decades. In the European Alps, glaciers retreat and permafrost thawing have led to the destabilization of mountain slopes, threatening human infrastructures and inhabitants. The observation of such changes at decadal scales is often limited to sparse in situ observations.
Here, we present three study cases of mountain permafrost sites based on a multidisciplinary approach over almost seven decades. The goal is to investigate and quantify morphodynamic changes and understand the causes of these evolutions. We used stereo-photogrammetry techniques to generate orthophotos and (DEMs) from historical aerial images (available, in France since 1940s). From this, we produced diachronic comparison of DEMs to quantify vertical surface changes, as well as feature tracking techniques of multi-temporal digital orthophotos for estimating horizontal displacement rates. Locally, high-resolution datasets (i.e. LiDAR surveys, UAV acquisitions and Pléiades stereo imagery) were also exploited to improve the quality of photogrammetric products. In addition, we combine these results with geophysics (ERT and GPR) to estimate the ice content, geomorphological surveys to describe the complex environments and the relationship with climatic forcing.
The first study case is the Laurichard rock glacier, where we were able to quantify changes of emergence velocities, fluxes, and volume. Together with an acceleration of surface velocity, important surface lowering have been found over the period 1952-2019, with a striking spatiotemporal reversal of volume balance.
The second study site is the Tignes glacial and periglacial complex, where the changes of thermokarstic lakes surface were quantified. The results suggest that drainage probably affects the presence and the evolution of the largest thermorkarst. Here too, a significant ice loss was found on the central channel concomitant to an increase in surface velocities.
The third study site is the Chauvet glacial and periglacial complex where several historical outburst floods are recorded during the 20th century, likely related to the permafrost degradation, the presence of thermokarstic lakes, and an intra-glacial channel. The lateral convergence of ice flow, due to the terrain subsidence caused by the intense melting, may cause the closure of the channel with a subsequent refill of the thermokarstic depression and finally a new catastrophic event.
Our results highlight the important value of historical aerial photography for having a longer perspective on the evolution of the high mountain cryosphere, thanks to accurate quantification of pluri-annual changes of volume and surface velocity. For instance, we could evidence : (1) a speed-up of the horizontal displacements since the 1990s in comparison with the previous decades; (2) an important surface lowering related to various melting processes (ice-core, thermokarst) for the three study sites; (3) relationships between the observed evolution and the contemporaneous climate warming, with a long-term evolution controlled by the warming of the ground and short-term changes that may relate to snow or precipitation or to the activity of the glacial-periglacial landforms.
How to cite: Cusicanqui, D., Rabatel, A., Bodin, X., Vincent, C., Thibert, E., Duvillard, P. A., and Revil, A.: Using historical aerial imagery to assess multidecadal kinematics and elevation changes. Application to mountain permafrost in the French Alps., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16371, https://doi.org/10.5194/egusphere-egu21-16371, 2021.
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Glacial and periglacial environments are highly sensitive to climate change, even more in mountain areas where warming is faster and, as a consequence, perennial features of the cryosphere like glaciers and permafrost have been fast evolving in the last decades. In the European Alps, glaciers retreat and permafrost thawing have led to the destabilization of mountain slopes, threatening human infrastructures and inhabitants. The observation of such changes at decadal scales is often limited to sparse in situ observations.
Here, we present three study cases of mountain permafrost sites based on a multidisciplinary approach over almost seven decades. The goal is to investigate and quantify morphodynamic changes and understand the causes of these evolutions. We used stereo-photogrammetry techniques to generate orthophotos and (DEMs) from historical aerial images (available, in France since 1940s). From this, we produced diachronic comparison of DEMs to quantify vertical surface changes, as well as feature tracking techniques of multi-temporal digital orthophotos for estimating horizontal displacement rates. Locally, high-resolution datasets (i.e. LiDAR surveys, UAV acquisitions and Pléiades stereo imagery) were also exploited to improve the quality of photogrammetric products. In addition, we combine these results with geophysics (ERT and GPR) to estimate the ice content, geomorphological surveys to describe the complex environments and the relationship with climatic forcing.
The first study case is the Laurichard rock glacier, where we were able to quantify changes of emergence velocities, fluxes, and volume. Together with an acceleration of surface velocity, important surface lowering have been found over the period 1952-2019, with a striking spatiotemporal reversal of volume balance.
The second study site is the Tignes glacial and periglacial complex, where the changes of thermokarstic lakes surface were quantified. The results suggest that drainage probably affects the presence and the evolution of the largest thermorkarst. Here too, a significant ice loss was found on the central channel concomitant to an increase in surface velocities.
The third study site is the Chauvet glacial and periglacial complex where several historical outburst floods are recorded during the 20th century, likely related to the permafrost degradation, the presence of thermokarstic lakes, and an intra-glacial channel. The lateral convergence of ice flow, due to the terrain subsidence caused by the intense melting, may cause the closure of the channel with a subsequent refill of the thermokarstic depression and finally a new catastrophic event.
Our results highlight the important value of historical aerial photography for having a longer perspective on the evolution of the high mountain cryosphere, thanks to accurate quantification of pluri-annual changes of volume and surface velocity. For instance, we could evidence : (1) a speed-up of the horizontal displacements since the 1990s in comparison with the previous decades; (2) an important surface lowering related to various melting processes (ice-core, thermokarst) for the three study sites; (3) relationships between the observed evolution and the contemporaneous climate warming, with a long-term evolution controlled by the warming of the ground and short-term changes that may relate to snow or precipitation or to the activity of the glacial-periglacial landforms.
How to cite: Cusicanqui, D., Rabatel, A., Bodin, X., Vincent, C., Thibert, E., Duvillard, P. A., and Revil, A.: Using historical aerial imagery to assess multidecadal kinematics and elevation changes. Application to mountain permafrost in the French Alps., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16371, https://doi.org/10.5194/egusphere-egu21-16371, 2021.
EGU21-5046 | vPICO presentations | GM2.11 | Highlight
Experiences from a Virtual Mapathon for collaborative Georeferencing of historical terrestrial Images in Alpine regionsSebastian Mikolka-Flöry, Tobias Heckmann, Michael Becht, and Norbert Pfeifer
Historical terrestrial images for identification, documentation, and especially the quantification of change in the alpine landscape are a largely unused source. Metric exploitation requires estimating the unknown camera parameters (camera location, angular attitude, and focal length) by photogrammetric resection. This is a challenging task, especially the identification of ground control points in mountainous terrain is time consuming and requires experience. Furthermore, due to the limited field of view of single images only small areas are captured. Hence, despite their possibility to provide quantitative information from more than one hundred years ago, integrating information from these historical images into subsequent analysis is often avoided.
Enabling their usage requires suitable software as well as users willing to engage in the challenge of image orientation. To facilitate this, a virtual Mapathon was organized, inviting participants to collaboratively orient historical images of the Val Martell (Italy) in the Ortler Alps. The participants from varying geoscience backgrounds (e.g. Botany, Climatology, Geomorphology, Glaciology, Hydrology) had little experience in photogrammetry prior to the Mapathon. Nevertheless, within one day nearly 100 images were oriented by 20 participants. The Mapathon was organized as a video conference using a web-based 3D image orientation software linked to an image database. Sessions with the whole group and in small teams alternated. Working in small teams stimulated internal discussions, promoting the understanding and success of each participant. Feedback received from the participants shows that the Mapathon helped overcoming the initial problem of getting started. Furthermore, the gained knowledge allows the participants to work with historical terrestrial images on their own in the future.
The set of oriented historical images created within the Mapathon further underlines the potential of historical terrestrial images. Due to the availability of numerous oriented images, the limited fields of view of individual images can be combined, allowing the documentation of changes for larger areas. With the calculation of the viewshed for each image, the image database can not only be queried by metadata, but more importantly by location and spatial coverage. Especially the possibility to search for images capturing a certain region of interest will encourage scientists to include historical terrestrial images into their analysis.
How to cite: Mikolka-Flöry, S., Heckmann, T., Becht, M., and Pfeifer, N.: Experiences from a Virtual Mapathon for collaborative Georeferencing of historical terrestrial Images in Alpine regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5046, https://doi.org/10.5194/egusphere-egu21-5046, 2021.
Historical terrestrial images for identification, documentation, and especially the quantification of change in the alpine landscape are a largely unused source. Metric exploitation requires estimating the unknown camera parameters (camera location, angular attitude, and focal length) by photogrammetric resection. This is a challenging task, especially the identification of ground control points in mountainous terrain is time consuming and requires experience. Furthermore, due to the limited field of view of single images only small areas are captured. Hence, despite their possibility to provide quantitative information from more than one hundred years ago, integrating information from these historical images into subsequent analysis is often avoided.
Enabling their usage requires suitable software as well as users willing to engage in the challenge of image orientation. To facilitate this, a virtual Mapathon was organized, inviting participants to collaboratively orient historical images of the Val Martell (Italy) in the Ortler Alps. The participants from varying geoscience backgrounds (e.g. Botany, Climatology, Geomorphology, Glaciology, Hydrology) had little experience in photogrammetry prior to the Mapathon. Nevertheless, within one day nearly 100 images were oriented by 20 participants. The Mapathon was organized as a video conference using a web-based 3D image orientation software linked to an image database. Sessions with the whole group and in small teams alternated. Working in small teams stimulated internal discussions, promoting the understanding and success of each participant. Feedback received from the participants shows that the Mapathon helped overcoming the initial problem of getting started. Furthermore, the gained knowledge allows the participants to work with historical terrestrial images on their own in the future.
The set of oriented historical images created within the Mapathon further underlines the potential of historical terrestrial images. Due to the availability of numerous oriented images, the limited fields of view of individual images can be combined, allowing the documentation of changes for larger areas. With the calculation of the viewshed for each image, the image database can not only be queried by metadata, but more importantly by location and spatial coverage. Especially the possibility to search for images capturing a certain region of interest will encourage scientists to include historical terrestrial images into their analysis.
How to cite: Mikolka-Flöry, S., Heckmann, T., Becht, M., and Pfeifer, N.: Experiences from a Virtual Mapathon for collaborative Georeferencing of historical terrestrial Images in Alpine regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5046, https://doi.org/10.5194/egusphere-egu21-5046, 2021.
EGU21-11925 | vPICO presentations | GM2.11
Colorisation of archival aerial imagery using deep learningRyusei Ishii, Patrice Carbonneau, and Hitoshi Miyamoto
Archival imagery dating back to the mid-twentieth century holds information that pre-dates urban expansion and the worst impacts of climate change. In this research, we examine deep learning colorisation methods applied to historical aerial images in Japan. Specifically, we attempt to colorize monochrome images of river basins by applying the method of Neural Style Transfer (NST). First, we created RGB orthomosaics (1m) for reaches of 3 Japanese rivers, the Kurobe, Ishikari, and Kinu rivers. From the orthomosaics, we extract 60 thousand image tiles of `100 x100` pixels in order to train the CNN used in NST. The Image tiles were classified into 6 classes: urban, river, forest, tree, grass, and paddy field. Second, we use the VGG16 model pre-trained on ImageNet data in a transfer learning approach where we freeze a variable number of layers. We fine-tuned the training epochs, learning rate, and frozen layers in VGG16 in order to derive the optimal CNN used in NST. The fine tuning resulted in the F-measure accuracy of 0.961, 0.947, and 0.917 for the freeze layer in 7,11,15, respectively. Third, we colorize monochrome aerial images by the NST with the retrained model weights. Here used RGB images for 7 Japanese rivers and the corresponding grayscale versions to evaluate the present NST colorization performance. The RMSE between the RGB and resultant colorized images showed the best performance with the model parameters of lower content layer (6), shallower freeze layer (7), and larger style/content weighting ratio (1.0 x10⁵). The NST hyperparameter analysis indicated that the colorized images became rougher when the content layer selected deeper in the VGG model. This is because the deeper the layer, the more features were extracted from the original image. It was also confirmed that the Kurobe and Ishikari rivers indicated higher accuracy in colorisation. It might come from the fact that the training dataset of the fine tuning was extracted from these river images. Finally, we colorized historical monochrome images of Kurobe river with the best NST parameters, resulting in quality high enough compared with the RGB images. The result indicated that the fine tuning of the NST model could achieve high performance to proceed further land cover classification in future research work.
How to cite: Ishii, R., Carbonneau, P., and Miyamoto, H.: Colorisation of archival aerial imagery using deep learning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11925, https://doi.org/10.5194/egusphere-egu21-11925, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Archival imagery dating back to the mid-twentieth century holds information that pre-dates urban expansion and the worst impacts of climate change. In this research, we examine deep learning colorisation methods applied to historical aerial images in Japan. Specifically, we attempt to colorize monochrome images of river basins by applying the method of Neural Style Transfer (NST). First, we created RGB orthomosaics (1m) for reaches of 3 Japanese rivers, the Kurobe, Ishikari, and Kinu rivers. From the orthomosaics, we extract 60 thousand image tiles of `100 x100` pixels in order to train the CNN used in NST. The Image tiles were classified into 6 classes: urban, river, forest, tree, grass, and paddy field. Second, we use the VGG16 model pre-trained on ImageNet data in a transfer learning approach where we freeze a variable number of layers. We fine-tuned the training epochs, learning rate, and frozen layers in VGG16 in order to derive the optimal CNN used in NST. The fine tuning resulted in the F-measure accuracy of 0.961, 0.947, and 0.917 for the freeze layer in 7,11,15, respectively. Third, we colorize monochrome aerial images by the NST with the retrained model weights. Here used RGB images for 7 Japanese rivers and the corresponding grayscale versions to evaluate the present NST colorization performance. The RMSE between the RGB and resultant colorized images showed the best performance with the model parameters of lower content layer (6), shallower freeze layer (7), and larger style/content weighting ratio (1.0 x10⁵). The NST hyperparameter analysis indicated that the colorized images became rougher when the content layer selected deeper in the VGG model. This is because the deeper the layer, the more features were extracted from the original image. It was also confirmed that the Kurobe and Ishikari rivers indicated higher accuracy in colorisation. It might come from the fact that the training dataset of the fine tuning was extracted from these river images. Finally, we colorized historical monochrome images of Kurobe river with the best NST parameters, resulting in quality high enough compared with the RGB images. The result indicated that the fine tuning of the NST model could achieve high performance to proceed further land cover classification in future research work.
How to cite: Ishii, R., Carbonneau, P., and Miyamoto, H.: Colorisation of archival aerial imagery using deep learning, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11925, https://doi.org/10.5194/egusphere-egu21-11925, 2021.
EGU21-11843 | vPICO presentations | GM2.11
Object-based image segmentation in photogrammetry for cartographic useBéla Kovács, Márton Pál, and Fanni Vörös
The use of aerial photography in topography has started in the first decades of the 20th century. Remote sensed data have become indispensable for cartographers and GIS staff when doing large-scale mapping: especially topographic, orienteering and thematic maps. The use of UAVs (unmanned aerial vehicles) for this purpose has also become widespread for some years. Various drones and sensors (RGB, multispectral and hyperspectral) with many specifications are used to capture and process the physical properties of an examined area. In parallel with the development of the hardware, new software solutions are emerging to visualize and analyse photogrammetric material: a large set of algorithms with different approaches are available for image processing.
Our study focuses on the large-scale topographic mapping of vegetation and land cover. Most traditional analogue and digital maps use these layers either for background or highlighted thematic purposes. We propose to use the theory of OBIA – Object-based Image Analysis to differentiate cover types. This method involves pixels to be grouped into larger polygon units based on either spectral or other variables (e.g. elevation, aspect, curvature in case of DEMs). The neighbours of initial seed points are examined whether they should be added to the region according to the similarity of their attributes. Using OBIA, different land cover types (trees, grass, soils, bare rock surfaces) can be distinguished either with supervised or unsupervised classification – depending on the purposes of the analyst. Our base data were high-resolution RGB and multispectral images (with 5 bands).
Following this methodology, not only elevation data (e.g. shaded relief or vector contour lines) can be derived from UAV imagery but vector land cover data are available for cartographers and GIS analysts. As the number of distinct land cover groups is free to choose, even quite complex thematic layers can be produced. These layers can serve as subjects of further analyses or for cartographic visualization.
BK is supported by Application Domain Specific Highly Reliable IT Solutions” project has been implemented with the support provided from the National Research, Development and Innovation Fund of Hungary, financed under the Thematic Excellence Programme TKP2020-NKA-06 (National Challenges Subprogramme) funding scheme.
MP and FV are supported by EFOP-3.6.3-VEKOP-16-2017-00001: Talent Management in Autonomous Vehicle Control Technologies – The Project is financed by the Hungarian Government and co-financed by the European Social Fund.
How to cite: Kovács, B., Pál, M., and Vörös, F.: Object-based image segmentation in photogrammetry for cartographic use, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11843, https://doi.org/10.5194/egusphere-egu21-11843, 2021.
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The use of aerial photography in topography has started in the first decades of the 20th century. Remote sensed data have become indispensable for cartographers and GIS staff when doing large-scale mapping: especially topographic, orienteering and thematic maps. The use of UAVs (unmanned aerial vehicles) for this purpose has also become widespread for some years. Various drones and sensors (RGB, multispectral and hyperspectral) with many specifications are used to capture and process the physical properties of an examined area. In parallel with the development of the hardware, new software solutions are emerging to visualize and analyse photogrammetric material: a large set of algorithms with different approaches are available for image processing.
Our study focuses on the large-scale topographic mapping of vegetation and land cover. Most traditional analogue and digital maps use these layers either for background or highlighted thematic purposes. We propose to use the theory of OBIA – Object-based Image Analysis to differentiate cover types. This method involves pixels to be grouped into larger polygon units based on either spectral or other variables (e.g. elevation, aspect, curvature in case of DEMs). The neighbours of initial seed points are examined whether they should be added to the region according to the similarity of their attributes. Using OBIA, different land cover types (trees, grass, soils, bare rock surfaces) can be distinguished either with supervised or unsupervised classification – depending on the purposes of the analyst. Our base data were high-resolution RGB and multispectral images (with 5 bands).
Following this methodology, not only elevation data (e.g. shaded relief or vector contour lines) can be derived from UAV imagery but vector land cover data are available for cartographers and GIS analysts. As the number of distinct land cover groups is free to choose, even quite complex thematic layers can be produced. These layers can serve as subjects of further analyses or for cartographic visualization.
BK is supported by Application Domain Specific Highly Reliable IT Solutions” project has been implemented with the support provided from the National Research, Development and Innovation Fund of Hungary, financed under the Thematic Excellence Programme TKP2020-NKA-06 (National Challenges Subprogramme) funding scheme.
MP and FV are supported by EFOP-3.6.3-VEKOP-16-2017-00001: Talent Management in Autonomous Vehicle Control Technologies – The Project is financed by the Hungarian Government and co-financed by the European Social Fund.
How to cite: Kovács, B., Pál, M., and Vörös, F.: Object-based image segmentation in photogrammetry for cartographic use, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11843, https://doi.org/10.5194/egusphere-egu21-11843, 2021.
EGU21-6012 | vPICO presentations | GM2.11
Geomorphological evolution of ephemeral rivers through historical and UAVs imagesAskoa Ibisate, Alfredo Ollero, J. Horacio García, Josu Ortiz Martínez de Lahidalga, Ana Sáenz de Olazagoitia, Yilena Hermoso, Carmelo Conesa-García, and Alvaro Gómez-Gutiérrez
Ephemeral rivers hydromorphological processes are intermittent and many times of fast response. Therefore they remain still quite unknown. The geomorphological mapping of river forms and geomorphological units is a useful tool to recognize the evolution, changes and the response of river adjustments of hydrological events.
A diachronic geomorphological mapping has been done in some ephemeral rivers located in Ebro basin, Segura basin and Calabrian ephemeral rivers. We are presenting the specific results of six reaches distributed by the Ebro basin (Tudela, Reajo, Alpartir, Cariñena, Valcodo, Sosa and Seco). The first historical aerial image is that of the American Flight B of 1956-57, another of the mid 80’s, the last official ortophotography available (around 2017), and a specific flight with an unmanned aerial vehicle (UAV) done during the winter of 2019. An altimetry correction has been performed on the first two images.
Different categories have been identified within the channel (active channel, principal channel and secondary channel), the sediment bars (vegetated, scant vegetated and non-active paleo-bars), the deposits coming from bank failures or tributaries, rocky areas, exhumed old sediment areas, consolidated or unconsolidated granular bed. The categories were mapped at different scales depending on the image quality (for example, from ≤ 1/300 scale of the UAV to ≤ 1/1,000 scale of the American flight).
This evolutionary cartography allows comparing the geomorphology of each river reach among different dates, considering the different resolution of the images and its limitations (i.e. previously, the results were unified to compare among them), and relating to the fluvial processes and changes on the river and basin.
This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities—State Research Agency (AEI) /Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
How to cite: Ibisate, A., Ollero, A., García, J. H., Ortiz Martínez de Lahidalga, J., Sáenz de Olazagoitia, A., Hermoso, Y., Conesa-García, C., and Gómez-Gutiérrez, A.: Geomorphological evolution of ephemeral rivers through historical and UAVs images, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6012, https://doi.org/10.5194/egusphere-egu21-6012, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Ephemeral rivers hydromorphological processes are intermittent and many times of fast response. Therefore they remain still quite unknown. The geomorphological mapping of river forms and geomorphological units is a useful tool to recognize the evolution, changes and the response of river adjustments of hydrological events.
A diachronic geomorphological mapping has been done in some ephemeral rivers located in Ebro basin, Segura basin and Calabrian ephemeral rivers. We are presenting the specific results of six reaches distributed by the Ebro basin (Tudela, Reajo, Alpartir, Cariñena, Valcodo, Sosa and Seco). The first historical aerial image is that of the American Flight B of 1956-57, another of the mid 80’s, the last official ortophotography available (around 2017), and a specific flight with an unmanned aerial vehicle (UAV) done during the winter of 2019. An altimetry correction has been performed on the first two images.
Different categories have been identified within the channel (active channel, principal channel and secondary channel), the sediment bars (vegetated, scant vegetated and non-active paleo-bars), the deposits coming from bank failures or tributaries, rocky areas, exhumed old sediment areas, consolidated or unconsolidated granular bed. The categories were mapped at different scales depending on the image quality (for example, from ≤ 1/300 scale of the UAV to ≤ 1/1,000 scale of the American flight).
This evolutionary cartography allows comparing the geomorphology of each river reach among different dates, considering the different resolution of the images and its limitations (i.e. previously, the results were unified to compare among them), and relating to the fluvial processes and changes on the river and basin.
This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities—State Research Agency (AEI) /Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
How to cite: Ibisate, A., Ollero, A., García, J. H., Ortiz Martínez de Lahidalga, J., Sáenz de Olazagoitia, A., Hermoso, Y., Conesa-García, C., and Gómez-Gutiérrez, A.: Geomorphological evolution of ephemeral rivers through historical and UAVs images, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6012, https://doi.org/10.5194/egusphere-egu21-6012, 2021.
EGU21-12007 | vPICO presentations | GM2.11
Short-term Glacial Dynamics Detection of a Maritime Glacier in Southeastern Tibetan Plateau using Cost-effective UAV and Rapid Photogrammetry TechniquesShuyang Xu and Ping Fu
Glacier mechanical ablation, such as ice calving, collapsing and flaking, plays a significant role in amplifying glacier recession. Mechanical ablation, as a non-linear response to climatic changes, caused by structural instabilities are mainly attributed to interactions of water-ice/glacier, which could be strengthened by the enhanced meltwater runoffs when rain season meets with ablation season. Similar to water-terminating glaciers, ice calving (or large-scale ice collapsing) events have happened in land-terminating glaciers in the southeastern Tibetan Plateau such as Hailuogou (HLG) glacier. However, other than ice calving events with water involved and dry calving events, ice calving of HLG glacier is roughly in the middle state between them. Previous studies have shown that HLG glacier have maintained negative mass balance in recent years with sustaining retreat, accompanied by mechanical ice loss events. Seven field trips to HLG glacier were conducted from 2017 to 2020 (concentrated from June to November). A cost-effective Unmanned Aerial Vehicle (UAV; DJI Mavic Pro) was used to capture images from ice fall to glacier terminus. Agisoft Metashape Pro was used to produce dense point cloud, digital surface model and ortho-images, etc. Results indicate that, under the intense interactions of water-ice/glacier, glacier terminus has been retreating continually, the terminal ice cliffs have gone through a succession of structural changes, the proglacial river have diverted several times, and the position of subglacial channel outlet had multi-times shifts accompanied with the periodic occurrences of terminal ice cave. The surrounding glacial landscapes have been altered accordingly such as the increasing runoffs from glacier river, the narrowing glacier ice fall, upward invasions by periglacial vegetation, and etc. The combination of repeated UAV mapping and rapidly streamlined terrain reconstruction technique provides a cost-effective option for short-term monitoring of glacier dynamics, especially for more precise detection on mechanical ablation, compared with datasets from commercial satellites.
How to cite: Xu, S. and Fu, P.: Short-term Glacial Dynamics Detection of a Maritime Glacier in Southeastern Tibetan Plateau using Cost-effective UAV and Rapid Photogrammetry Techniques, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12007, https://doi.org/10.5194/egusphere-egu21-12007, 2021.
Glacier mechanical ablation, such as ice calving, collapsing and flaking, plays a significant role in amplifying glacier recession. Mechanical ablation, as a non-linear response to climatic changes, caused by structural instabilities are mainly attributed to interactions of water-ice/glacier, which could be strengthened by the enhanced meltwater runoffs when rain season meets with ablation season. Similar to water-terminating glaciers, ice calving (or large-scale ice collapsing) events have happened in land-terminating glaciers in the southeastern Tibetan Plateau such as Hailuogou (HLG) glacier. However, other than ice calving events with water involved and dry calving events, ice calving of HLG glacier is roughly in the middle state between them. Previous studies have shown that HLG glacier have maintained negative mass balance in recent years with sustaining retreat, accompanied by mechanical ice loss events. Seven field trips to HLG glacier were conducted from 2017 to 2020 (concentrated from June to November). A cost-effective Unmanned Aerial Vehicle (UAV; DJI Mavic Pro) was used to capture images from ice fall to glacier terminus. Agisoft Metashape Pro was used to produce dense point cloud, digital surface model and ortho-images, etc. Results indicate that, under the intense interactions of water-ice/glacier, glacier terminus has been retreating continually, the terminal ice cliffs have gone through a succession of structural changes, the proglacial river have diverted several times, and the position of subglacial channel outlet had multi-times shifts accompanied with the periodic occurrences of terminal ice cave. The surrounding glacial landscapes have been altered accordingly such as the increasing runoffs from glacier river, the narrowing glacier ice fall, upward invasions by periglacial vegetation, and etc. The combination of repeated UAV mapping and rapidly streamlined terrain reconstruction technique provides a cost-effective option for short-term monitoring of glacier dynamics, especially for more precise detection on mechanical ablation, compared with datasets from commercial satellites.
How to cite: Xu, S. and Fu, P.: Short-term Glacial Dynamics Detection of a Maritime Glacier in Southeastern Tibetan Plateau using Cost-effective UAV and Rapid Photogrammetry Techniques, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12007, https://doi.org/10.5194/egusphere-egu21-12007, 2021.
EGU21-14844 | vPICO presentations | GM2.11
Rock glacier deformation using an Unmanned Aerial Vehicle (UAV) with RTK GNSS capabilitySebastián Vivero and Christophe Lambiel
In high alpine geomorphological research, different technologies are increasingly used to describe and monitor mass movements such as rock glaciers. Among them, the combination of Unmanned Aerial Vehicle (UAV) systems and Structure from Motion (SfM) techniques is gaining continuous interest due to rapid technological developments. In this study, we test the capability of repeated UAV surveys to accurately survey rock glacier deformation in the Lac des Vaux area, Valais Alps. The studied landform is located on a typical anthropic alpine environment in the Swiss Alps, where ski facilities and alpine tracks are a commonplace. A DJI Phantom 4 RTK UAV was flown twice in September 2019 and September 2020 to cover an area of about 0.25 km2 with nearly 1000 images each time. Differential corrections using a Virtual Reference Station (VRS) provided image geotags with centimetre-level accurate 3-D coordinates, thereby allowing dispensing with ground control. High-resolution orthomosaics and high-density point clouds are derived from the UAV-RTK surveys using a standard SfM processing workflow. The corresponding point clouds' accuracy was evaluated and adjusted based on stable terrain, reducing the 3-D alignment errors to a mean of 0.02 m. Elevation changes and surface kinematics in the rock glacier complex and its margins were quantified using point cloud operations and image correlation techniques. The results indicate that the landform has at least eight different lobes with mean velocities ranging between 0.1 and 1.3 m yr-1. The high-resolution analysis also permitted identifying moving lobes without morphological expression and small thermokarst depressions on the ski slope structure that traverses the rock glacier's active zone. Without relying on ground control, our approach achieves horizontal and vertical accuracies nearly as good as monitoring techniques using more traditional differential GNSS devices.
How to cite: Vivero, S. and Lambiel, C.: Rock glacier deformation using an Unmanned Aerial Vehicle (UAV) with RTK GNSS capability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14844, https://doi.org/10.5194/egusphere-egu21-14844, 2021.
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In high alpine geomorphological research, different technologies are increasingly used to describe and monitor mass movements such as rock glaciers. Among them, the combination of Unmanned Aerial Vehicle (UAV) systems and Structure from Motion (SfM) techniques is gaining continuous interest due to rapid technological developments. In this study, we test the capability of repeated UAV surveys to accurately survey rock glacier deformation in the Lac des Vaux area, Valais Alps. The studied landform is located on a typical anthropic alpine environment in the Swiss Alps, where ski facilities and alpine tracks are a commonplace. A DJI Phantom 4 RTK UAV was flown twice in September 2019 and September 2020 to cover an area of about 0.25 km2 with nearly 1000 images each time. Differential corrections using a Virtual Reference Station (VRS) provided image geotags with centimetre-level accurate 3-D coordinates, thereby allowing dispensing with ground control. High-resolution orthomosaics and high-density point clouds are derived from the UAV-RTK surveys using a standard SfM processing workflow. The corresponding point clouds' accuracy was evaluated and adjusted based on stable terrain, reducing the 3-D alignment errors to a mean of 0.02 m. Elevation changes and surface kinematics in the rock glacier complex and its margins were quantified using point cloud operations and image correlation techniques. The results indicate that the landform has at least eight different lobes with mean velocities ranging between 0.1 and 1.3 m yr-1. The high-resolution analysis also permitted identifying moving lobes without morphological expression and small thermokarst depressions on the ski slope structure that traverses the rock glacier's active zone. Without relying on ground control, our approach achieves horizontal and vertical accuracies nearly as good as monitoring techniques using more traditional differential GNSS devices.
How to cite: Vivero, S. and Lambiel, C.: Rock glacier deformation using an Unmanned Aerial Vehicle (UAV) with RTK GNSS capability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14844, https://doi.org/10.5194/egusphere-egu21-14844, 2021.
EGU21-7166 | vPICO presentations | GM2.11
Mapping of Quaternary river terrace landforms with Unmanned Aerial Vehicle (UAV): A case study in the Sakarya River, NW TurkeyEbubekir Karakoca and Levent Uncu
River systems are areas that respond most rapidly to regional and / or local tectonic movements, with global climate changes and general basement fluctuations that occurred during the Quaternary period. The most important geomorphological units where these events can be observed are terrace systems, which are the result of deposition and erosion processes. In fluvial geomorphology research on terrace systems, modern technological innovations are used as well as conventional field methods. Especially low-cost Unmanned Aerial Vehicles (UAV) and modern photogrammetry methods are preferred because they both provide detailed and precise identification of terraces and high resolution topography outputs in spatial and temporal terms.
This study aims to put a comprehensive mapping of the terrace systems observed in an area of 1.27 km² around Gemiciköy (Bilecik Province), which is located in the middle part of the Sakarya River valley, the largest river in Northwest Anatolia. Accordingly, we used the Structure from Motion (SfM) method which is based on photogrammetric principles and UAV. During the study, 582 images taken from a height of 100 m and having 80% overlap in line with the flight plans by using the DJI Mavic Mini UAV model were evaluated in Agisoft Metashape Professional software. With the use of image processing algorithms, the dense point cloud was first obtained, and then the orthomosaic and digital surface model with 3.29 cm resolution was produced. Two terrace levels (+10 m and +19 m) detected with digital surface modeling, and these were verified by stratigraphic and sedimentological observations made in the field.
As a result, low-cost UAV technologies are quite useful in terms of providing more detailed monitoring, mapping and analysis of river environments, together with the production of sensitive and high resolution topography data required in modern fluvial geomorphology research.
How to cite: Karakoca, E. and Uncu, L.: Mapping of Quaternary river terrace landforms with Unmanned Aerial Vehicle (UAV): A case study in the Sakarya River, NW Turkey, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7166, https://doi.org/10.5194/egusphere-egu21-7166, 2021.
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River systems are areas that respond most rapidly to regional and / or local tectonic movements, with global climate changes and general basement fluctuations that occurred during the Quaternary period. The most important geomorphological units where these events can be observed are terrace systems, which are the result of deposition and erosion processes. In fluvial geomorphology research on terrace systems, modern technological innovations are used as well as conventional field methods. Especially low-cost Unmanned Aerial Vehicles (UAV) and modern photogrammetry methods are preferred because they both provide detailed and precise identification of terraces and high resolution topography outputs in spatial and temporal terms.
This study aims to put a comprehensive mapping of the terrace systems observed in an area of 1.27 km² around Gemiciköy (Bilecik Province), which is located in the middle part of the Sakarya River valley, the largest river in Northwest Anatolia. Accordingly, we used the Structure from Motion (SfM) method which is based on photogrammetric principles and UAV. During the study, 582 images taken from a height of 100 m and having 80% overlap in line with the flight plans by using the DJI Mavic Mini UAV model were evaluated in Agisoft Metashape Professional software. With the use of image processing algorithms, the dense point cloud was first obtained, and then the orthomosaic and digital surface model with 3.29 cm resolution was produced. Two terrace levels (+10 m and +19 m) detected with digital surface modeling, and these were verified by stratigraphic and sedimentological observations made in the field.
As a result, low-cost UAV technologies are quite useful in terms of providing more detailed monitoring, mapping and analysis of river environments, together with the production of sensitive and high resolution topography data required in modern fluvial geomorphology research.
How to cite: Karakoca, E. and Uncu, L.: Mapping of Quaternary river terrace landforms with Unmanned Aerial Vehicle (UAV): A case study in the Sakarya River, NW Turkey, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7166, https://doi.org/10.5194/egusphere-egu21-7166, 2021.
GM2.12 – Novel applications and technique developments of cosmogenic nuclides
EGU21-5346 | vPICO presentations | GM2.12
Can 14C-10Be detect transient patterns of denudation ? Application to the French Massif Central.Sebastien J.P. Lenard, Maarten Lupker, Irene Schimmelpfennig, Vincent Godard, Clement Desormeaux, Negar Haghipour, Lukas Wacker, Georges Aumaître, Karim Keddadouche, and Didier L. Bourles
Denudation rates are routinely derived from concentrations of terrestrial in situ produced cosmogenic nuclides (TCN), particularly from 10Be concentrations in river sand. Denudation rates are calculated assuming that they remain steady throughout the integration time scale of the TCN. However, such an assumption is possibly unverified in settings with negligible tectonics, where rates typically range from 10 to 100 mm/ky. In those settings, the TCN conveys a signal that integrates denudation over a time span longer than a few thousand years. The signal may include periods when anthropogenic and climatic forcing on denudation was distinct from modern times. For instance, agricultural practices were limited before 6,000 years B.P. and climatic conditions were colder and drier before 10,000 years B.P. A variable forcing may produce variable and transient denudation rates. In that case, the assumption of steady denudation rates is invalid, and their derivation may introduce a bias.
To detect transient landscapes and resolve such a bias, we can take advantage of the different sensitivity of the 14C and 10Be TCNs to recent and short-term changes in surface denudation. In situ 14C is more sensitive than 10Be to such changes, because of a shorter half-life (5,700 y compared to 1.4 My). This potential application of coupled 14C - 10Be measurements has recently been discussed in several theoretical studies (Hippe, 2017; Mudd, 2017; Skov et al., 2019). Despite the improvement of 14C extraction lines and measurement facilities (Hippe et al., 2009; Lupker et al., 2019), sensitivity tests remain limited on natural cases (Hippe et al., 2012).
Here, we propose assessing this new application by in situ 14C - 10Be measurements on river sand from the Cevennes and the Monts Margeride within the Variscan Massif Central in France. With an average elevation of ~700 m, this mountain range presents an asymmetrical topography, composed of a low-relief surface reaching 1,700 m, and bordered by a gently sloping flank to the west and a steep escarpment to the southeast, along the Cevennes fault. This escarpment receives frequent and seasonal extreme precipitation events (300-700 mm in 48h) on its southeast flank.
The range is subject to very limited seismic activity and appears relevant for an application of the 14C-10Be couple. Basins are rich in quartz and have homogeneous lithology. The recent paleoclimatic context is well constrained, with substantial climatic variations but with limited Pleistocene glaciations (e.g. Fauquette et al., 1999; Magny et al., 2003; Mayewski et al., 2004). The Massif Central is subject to active erosion processes, without major contribution from stochastic events such as landslides. Denudation rates are in the range of the theoretical study of Skov et al. 2019 (Schaller et al. 2001; Molliex et al. 2016; Olivetti et al. 2016; Desormeaux et al., 2021) and several studies have suggested transient denudation patterns (Schaller et al. 2001; Olivetti et al. 2016). With our new measurements, we will verify whether the 14C-10Be couple has sufficient resolution to detect such transience in natural cases.
How to cite: Lenard, S. J. P., Lupker, M., Schimmelpfennig, I., Godard, V., Desormeaux, C., Haghipour, N., Wacker, L., Aumaître, G., Keddadouche, K., and Bourles, D. L.: Can 14C-10Be detect transient patterns of denudation ? Application to the French Massif Central., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5346, https://doi.org/10.5194/egusphere-egu21-5346, 2021.
Denudation rates are routinely derived from concentrations of terrestrial in situ produced cosmogenic nuclides (TCN), particularly from 10Be concentrations in river sand. Denudation rates are calculated assuming that they remain steady throughout the integration time scale of the TCN. However, such an assumption is possibly unverified in settings with negligible tectonics, where rates typically range from 10 to 100 mm/ky. In those settings, the TCN conveys a signal that integrates denudation over a time span longer than a few thousand years. The signal may include periods when anthropogenic and climatic forcing on denudation was distinct from modern times. For instance, agricultural practices were limited before 6,000 years B.P. and climatic conditions were colder and drier before 10,000 years B.P. A variable forcing may produce variable and transient denudation rates. In that case, the assumption of steady denudation rates is invalid, and their derivation may introduce a bias.
To detect transient landscapes and resolve such a bias, we can take advantage of the different sensitivity of the 14C and 10Be TCNs to recent and short-term changes in surface denudation. In situ 14C is more sensitive than 10Be to such changes, because of a shorter half-life (5,700 y compared to 1.4 My). This potential application of coupled 14C - 10Be measurements has recently been discussed in several theoretical studies (Hippe, 2017; Mudd, 2017; Skov et al., 2019). Despite the improvement of 14C extraction lines and measurement facilities (Hippe et al., 2009; Lupker et al., 2019), sensitivity tests remain limited on natural cases (Hippe et al., 2012).
Here, we propose assessing this new application by in situ 14C - 10Be measurements on river sand from the Cevennes and the Monts Margeride within the Variscan Massif Central in France. With an average elevation of ~700 m, this mountain range presents an asymmetrical topography, composed of a low-relief surface reaching 1,700 m, and bordered by a gently sloping flank to the west and a steep escarpment to the southeast, along the Cevennes fault. This escarpment receives frequent and seasonal extreme precipitation events (300-700 mm in 48h) on its southeast flank.
The range is subject to very limited seismic activity and appears relevant for an application of the 14C-10Be couple. Basins are rich in quartz and have homogeneous lithology. The recent paleoclimatic context is well constrained, with substantial climatic variations but with limited Pleistocene glaciations (e.g. Fauquette et al., 1999; Magny et al., 2003; Mayewski et al., 2004). The Massif Central is subject to active erosion processes, without major contribution from stochastic events such as landslides. Denudation rates are in the range of the theoretical study of Skov et al. 2019 (Schaller et al. 2001; Molliex et al. 2016; Olivetti et al. 2016; Desormeaux et al., 2021) and several studies have suggested transient denudation patterns (Schaller et al. 2001; Olivetti et al. 2016). With our new measurements, we will verify whether the 14C-10Be couple has sufficient resolution to detect such transience in natural cases.
How to cite: Lenard, S. J. P., Lupker, M., Schimmelpfennig, I., Godard, V., Desormeaux, C., Haghipour, N., Wacker, L., Aumaître, G., Keddadouche, K., and Bourles, D. L.: Can 14C-10Be detect transient patterns of denudation ? Application to the French Massif Central., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5346, https://doi.org/10.5194/egusphere-egu21-5346, 2021.
EGU21-10051 | vPICO presentations | GM2.12
Detecting transience in slow evolution landscapes using cosmogenic nuclides and high resolution morphometryVincent Godard, Andre Salgado, Lionel Siame, Jules Fleury, and Aster Team
Transient evolution and adjustment to changing tectonic and climatic boundary conditions is an essential attribute of landscapes. We present a new approach to detect and quantify transience in slow erosion landscapes over 100 ka timescales. We compare curvature and cosmogenic nuclides measurements (10Be and 26Al) at hilltop sites with predictions of hillslope diffusion theory, in the slowly evolving quartzitic Serra do Cipó range in SE Brazil, and we observe a distinctive signature of an acceleration of denudation. The timing of this increase cannot be unequivocally associated with a single climatic event but is consistent with climatically-modulated important fluctuations in precipitation and erosion in this area during Middle and Late Pleistocene.
How to cite: Godard, V., Salgado, A., Siame, L., Fleury, J., and Team, A.: Detecting transience in slow evolution landscapes using cosmogenic nuclides and high resolution morphometry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10051, https://doi.org/10.5194/egusphere-egu21-10051, 2021.
Transient evolution and adjustment to changing tectonic and climatic boundary conditions is an essential attribute of landscapes. We present a new approach to detect and quantify transience in slow erosion landscapes over 100 ka timescales. We compare curvature and cosmogenic nuclides measurements (10Be and 26Al) at hilltop sites with predictions of hillslope diffusion theory, in the slowly evolving quartzitic Serra do Cipó range in SE Brazil, and we observe a distinctive signature of an acceleration of denudation. The timing of this increase cannot be unequivocally associated with a single climatic event but is consistent with climatically-modulated important fluctuations in precipitation and erosion in this area during Middle and Late Pleistocene.
How to cite: Godard, V., Salgado, A., Siame, L., Fleury, J., and Team, A.: Detecting transience in slow evolution landscapes using cosmogenic nuclides and high resolution morphometry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10051, https://doi.org/10.5194/egusphere-egu21-10051, 2021.
EGU21-5643 | vPICO presentations | GM2.12
Early Pleistocene complex cut-and-fill sequences in the AlpsCatharina Dieleman, Marcus Christl, Christof Vockenhuber, Philip Gautschi, and Naki Akçar
Deckenschotter (Cover Gravels in German) are Quaternary glacio-fluvial gravels, which unconformably overlie Tertiary Molasse or Mesozoic bedrock in the Northern Alpine Foreland. They comprise also the evidence of the Early Pleistocene glaciations. A significant phase of incision separated them into Höhere Deckenschotter (HDS: Higher Cover Gravels) and Tiefere Deckenschotter (TDS: Lower Cover Gravels) based on their topography. How the landscape evolved during Deckenschotter times is still not fully understood. The new cosmogenic nuclide chronology suggests that HDS deposited around 2 Ma and TDS around 1 Ma. In addition, 2 Ma old Deckenschotter are located at the same topographic elevation as the 1 Ma ones at Irchel (Canton of Zurich). This, indeed, points to cut-and-fill sequences and challenges the chronology based on the morphostratigraphy.
The aim of this study is to reconstruct the drainage patterns, base level changes, and thus the landscape evolution in the northern Alpine Foreland during the Early Pleistocene. Therefore, we focused on three Deckenschotter sites at Irchel and one in the area around Lake Constance. Sediments at these sites were analysed in detail to reveal their provenance, transport mechanism, depositional environment, and paleoflow regimes. Their chronology was established by isochron-burial dating. Our results indicate that the analysed sediments were transported from the Central and eastern Central Alps as well as from the Molasse to the foreland first by glaciers and then by rivers. They are deposited in a glacio-fluvial environment in the vicinity of a glacier. Based on the reconstructed chronology in this study and published cosmogenic nuclide ages, we propose that Deckenschotter are cut-and-fill sequences accumulated in three pulses between 2.5 Ma and 1 Ma. This cut-and-fill system implies that the regional base level was relatively constant during the Early Pleistocene. In addition, the depositional environment of Deckenschotter shows the presence of glaciers in the foreland. The 2.5 Ma old gravels, therefore, document the first advance of glaciers onto the Alpine Foreland. This seems to be synchronous with a first onset of glaciations on the northern hemisphere, which is assumed to occur at around 2.7 Ma.
How to cite: Dieleman, C., Christl, M., Vockenhuber, C., Gautschi, P., and Akçar, N.: Early Pleistocene complex cut-and-fill sequences in the Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5643, https://doi.org/10.5194/egusphere-egu21-5643, 2021.
Deckenschotter (Cover Gravels in German) are Quaternary glacio-fluvial gravels, which unconformably overlie Tertiary Molasse or Mesozoic bedrock in the Northern Alpine Foreland. They comprise also the evidence of the Early Pleistocene glaciations. A significant phase of incision separated them into Höhere Deckenschotter (HDS: Higher Cover Gravels) and Tiefere Deckenschotter (TDS: Lower Cover Gravels) based on their topography. How the landscape evolved during Deckenschotter times is still not fully understood. The new cosmogenic nuclide chronology suggests that HDS deposited around 2 Ma and TDS around 1 Ma. In addition, 2 Ma old Deckenschotter are located at the same topographic elevation as the 1 Ma ones at Irchel (Canton of Zurich). This, indeed, points to cut-and-fill sequences and challenges the chronology based on the morphostratigraphy.
The aim of this study is to reconstruct the drainage patterns, base level changes, and thus the landscape evolution in the northern Alpine Foreland during the Early Pleistocene. Therefore, we focused on three Deckenschotter sites at Irchel and one in the area around Lake Constance. Sediments at these sites were analysed in detail to reveal their provenance, transport mechanism, depositional environment, and paleoflow regimes. Their chronology was established by isochron-burial dating. Our results indicate that the analysed sediments were transported from the Central and eastern Central Alps as well as from the Molasse to the foreland first by glaciers and then by rivers. They are deposited in a glacio-fluvial environment in the vicinity of a glacier. Based on the reconstructed chronology in this study and published cosmogenic nuclide ages, we propose that Deckenschotter are cut-and-fill sequences accumulated in three pulses between 2.5 Ma and 1 Ma. This cut-and-fill system implies that the regional base level was relatively constant during the Early Pleistocene. In addition, the depositional environment of Deckenschotter shows the presence of glaciers in the foreland. The 2.5 Ma old gravels, therefore, document the first advance of glaciers onto the Alpine Foreland. This seems to be synchronous with a first onset of glaciations on the northern hemisphere, which is assumed to occur at around 2.7 Ma.
How to cite: Dieleman, C., Christl, M., Vockenhuber, C., Gautschi, P., and Akçar, N.: Early Pleistocene complex cut-and-fill sequences in the Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5643, https://doi.org/10.5194/egusphere-egu21-5643, 2021.
EGU21-12374 | vPICO presentations | GM2.12
Delving deeper into cosmogenic 26Al-10Be isochron-burial dating of Swiss Deckenschotter depositsEwelina Broś, Florian Kober, Susan Ivy-Ochs, Reto Grischott, Marcus Christl, Christof Vockenhuber, Colin Maden, and Hans-Arno Synal
The oldest Quaternary deposits of the Swiss Northern Alpine Foreland are found on numerous hilltops, up to 300 m above the current valley bottoms. These Deckenschotter deposits consist mainly of glaciofluvial sediments intercalated with glacial sediments. Traditionally, the Deckenschotter are divided into two units: Höhere Deckenschotter (HDS – Higher Deckenschotter) and Tiefere Deckenschotter (TDS – Lower Deckenschotter). Elevation differences between the two suggest a phase of 100-150 m of incision (Graf, 2009).
Knowledge of their age of deposition is necessary for understanding the long-term landscape evolution as well as for assessing the long-term safety of the planned deep geological repository for nuclear waste in northern Switzerland (NTB 14-01, 2014). In this study, the method of isochron-burial dating was implemented to address the question of the age of the Deckenschotter. We aim to reconstruct the chronology of the alternating deposition and incision of the gravel units in the Northern Alpine Foreland. Our focus is placed on similar and complementary Deckenschotter sites located in the Northern Alpine Foreland in crucial locations in order to establish sound long-term landscape evolution scenarios. One of these is a former gravel pit, Feusi, situated in the southern slope of the hill chain called ‘Egg’ or ‘Schliniker Platten’, north of the village Oberweningen. The outcrop comprises several gravel units intercalated with glacigenic diamict layer in the upper part. Previous age estimates with the isochron-burial dating method indicate an age of 1.1 ± 0.2 Ma for the diamict layer (NAB 19-025, 2020). Knudsen et al. (2020) reported an age of 0.93 ± 0.13 Ma for the same layer based on a slightly different age calculation approach.
We sampled the lowermost accessible horizon, the Egg Schotter, of the Feusi outcrop at an altitude of ~580 m a.s.l. This horizon is located close to the base of the outcrop, just a few meters above the contact with the underlying Molasse and in a clear stratigraphic position, 20 m below the previously dated diamict. Study of the lowermost unit will allow us to temporally examine the earliest phases of Deckenschotter accumulation. Weathering horizons in the gravel layers overlying the Egg Schotter suggests periodic subaerial exposure. Therefore, the total time contained in the sediment package is difficult to estimate. Having two horizons dated at different depth in the same outcrop may provide insight into the timespan hidden between the deposition and weathering of different gravel layers. Indications of the timespan of HDS activity could be further gleaned by comparing to the age from the glacigenic sediment. In order to achieve this, eight clast samples of quartz-rich lithologies, of various shapes and sizes were collected in the Egg Schotter and processed for isochron-burial dating. The cosmogenic nuclides 10Be and 26Al were extracted and measured with the new MILEA accelerator at the accelerator mass spectrometry facility, ETH Zurich. The first results of this study will be presented.
Graf, H.R. 2009: Quaternary Science Journal 58, 12–53
Nagra, NTB 14-01, 2014
Nagra, NAB 19-025, 2020
Knudsen, M.F. et al. 2020. Earth and Planetary Science Letters, 549, 116491
How to cite: Broś, E., Kober, F., Ivy-Ochs, S., Grischott, R., Christl, M., Vockenhuber, C., Maden, C., and Synal, H.-A.: Delving deeper into cosmogenic 26Al-10Be isochron-burial dating of Swiss Deckenschotter deposits, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12374, https://doi.org/10.5194/egusphere-egu21-12374, 2021.
The oldest Quaternary deposits of the Swiss Northern Alpine Foreland are found on numerous hilltops, up to 300 m above the current valley bottoms. These Deckenschotter deposits consist mainly of glaciofluvial sediments intercalated with glacial sediments. Traditionally, the Deckenschotter are divided into two units: Höhere Deckenschotter (HDS – Higher Deckenschotter) and Tiefere Deckenschotter (TDS – Lower Deckenschotter). Elevation differences between the two suggest a phase of 100-150 m of incision (Graf, 2009).
Knowledge of their age of deposition is necessary for understanding the long-term landscape evolution as well as for assessing the long-term safety of the planned deep geological repository for nuclear waste in northern Switzerland (NTB 14-01, 2014). In this study, the method of isochron-burial dating was implemented to address the question of the age of the Deckenschotter. We aim to reconstruct the chronology of the alternating deposition and incision of the gravel units in the Northern Alpine Foreland. Our focus is placed on similar and complementary Deckenschotter sites located in the Northern Alpine Foreland in crucial locations in order to establish sound long-term landscape evolution scenarios. One of these is a former gravel pit, Feusi, situated in the southern slope of the hill chain called ‘Egg’ or ‘Schliniker Platten’, north of the village Oberweningen. The outcrop comprises several gravel units intercalated with glacigenic diamict layer in the upper part. Previous age estimates with the isochron-burial dating method indicate an age of 1.1 ± 0.2 Ma for the diamict layer (NAB 19-025, 2020). Knudsen et al. (2020) reported an age of 0.93 ± 0.13 Ma for the same layer based on a slightly different age calculation approach.
We sampled the lowermost accessible horizon, the Egg Schotter, of the Feusi outcrop at an altitude of ~580 m a.s.l. This horizon is located close to the base of the outcrop, just a few meters above the contact with the underlying Molasse and in a clear stratigraphic position, 20 m below the previously dated diamict. Study of the lowermost unit will allow us to temporally examine the earliest phases of Deckenschotter accumulation. Weathering horizons in the gravel layers overlying the Egg Schotter suggests periodic subaerial exposure. Therefore, the total time contained in the sediment package is difficult to estimate. Having two horizons dated at different depth in the same outcrop may provide insight into the timespan hidden between the deposition and weathering of different gravel layers. Indications of the timespan of HDS activity could be further gleaned by comparing to the age from the glacigenic sediment. In order to achieve this, eight clast samples of quartz-rich lithologies, of various shapes and sizes were collected in the Egg Schotter and processed for isochron-burial dating. The cosmogenic nuclides 10Be and 26Al were extracted and measured with the new MILEA accelerator at the accelerator mass spectrometry facility, ETH Zurich. The first results of this study will be presented.
Graf, H.R. 2009: Quaternary Science Journal 58, 12–53
Nagra, NTB 14-01, 2014
Nagra, NAB 19-025, 2020
Knudsen, M.F. et al. 2020. Earth and Planetary Science Letters, 549, 116491
How to cite: Broś, E., Kober, F., Ivy-Ochs, S., Grischott, R., Christl, M., Vockenhuber, C., Maden, C., and Synal, H.-A.: Delving deeper into cosmogenic 26Al-10Be isochron-burial dating of Swiss Deckenschotter deposits, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12374, https://doi.org/10.5194/egusphere-egu21-12374, 2021.
EGU21-14848 | vPICO presentations | GM2.12
P-PINI: a new inversion method for sediment-burial datingJesper Nørgaard, John Jansen, Stephanie Neuhuber, Zsófia Ruszkizcay-Rüdiger, Sandra Braumann, Markus Feibig, Philipp Häuselmann, and Mads Faurschou Knudsen
For sediment-burial dating with a cosmogenic nuclide pair, the isochron burial method performs well provided that the sediment source has undergone (1) steady erosion and (2) continuous exposure to cosmic rays. These conditions exert important limitations on applications of the method. And yet, in mountainous fluvial and glacial landscapes, it is commonly found that the source area has experienced landsliding or glacial quarrying (i.e., non-steady erosion), and/or intermittent sediment storage or burial beneath glaciers (i.e., discontinuous exposure). As well as breaching the assumptions of the isochron method, such processes tend to yield low nuclide concentrations in the sample, which further limits its workability.
Here we present a more flexible method that accommodates complex, non-steady pre-burial erosion and exposure histories: conditions that exclude the isochron burial method. P-PINI (Particle Pathway Inversion of Nuclide Inventories) is a Monte Carlo-based inversion model that employs a source-to-sink approach for estimating the depositional age of fluvial and glaciogenic sediments. This method has been successfully applied to the Deckenschotter in the northern Alpine foreland (see Knudsen et al. 2020, Earth & Planetary Science Letters 549, 116491). As with the isochron burial method, P-PINI exploits an ensemble of paired nuclide (e.g., 10Be-26Al) concentrations measured in different samples from the same depth in a sedimentary sequence. But unlike the isochron method, P-PINI applies a stochastic approach to simulate a wide range of possible pre-depositional exposure and erosion histories for each individual sample. These different pre-burial histories (unique to each sample) are then integrated with the constraint that all samples share a common burial history at the sink. Where cosmogenic nuclide data (or other chronometric data, e.g., OSL) are available for multiple sites, Bayesian inference modelling can impose a priori relative age constraints, or estimates on the maximum duration of sediment storage.
In this presentation, we extend P-PINI to explore how sediment storage and reworking (i.e., a range of burial depths and durations) between source and sink affects burial age estimates. Significant intermediate storage is characteristic of large river systems, such as the Danube River. Using cosmogenic 10Be-26Al concentrations measured in fluvial gravels at Gänserndorf and Schlosshof, two terraces along the Danube River in the Vienna Basin (Braumann et al., 2019. Quat. Int. 509. 87-102), we examine how the burial ages at these two sites are a function of the pre-burial history experienced by the samples.
How to cite: Nørgaard, J., Jansen, J., Neuhuber, S., Ruszkizcay-Rüdiger, Z., Braumann, S., Feibig, M., Häuselmann, P., and Faurschou Knudsen, M.: P-PINI: a new inversion method for sediment-burial dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14848, https://doi.org/10.5194/egusphere-egu21-14848, 2021.
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For sediment-burial dating with a cosmogenic nuclide pair, the isochron burial method performs well provided that the sediment source has undergone (1) steady erosion and (2) continuous exposure to cosmic rays. These conditions exert important limitations on applications of the method. And yet, in mountainous fluvial and glacial landscapes, it is commonly found that the source area has experienced landsliding or glacial quarrying (i.e., non-steady erosion), and/or intermittent sediment storage or burial beneath glaciers (i.e., discontinuous exposure). As well as breaching the assumptions of the isochron method, such processes tend to yield low nuclide concentrations in the sample, which further limits its workability.
Here we present a more flexible method that accommodates complex, non-steady pre-burial erosion and exposure histories: conditions that exclude the isochron burial method. P-PINI (Particle Pathway Inversion of Nuclide Inventories) is a Monte Carlo-based inversion model that employs a source-to-sink approach for estimating the depositional age of fluvial and glaciogenic sediments. This method has been successfully applied to the Deckenschotter in the northern Alpine foreland (see Knudsen et al. 2020, Earth & Planetary Science Letters 549, 116491). As with the isochron burial method, P-PINI exploits an ensemble of paired nuclide (e.g., 10Be-26Al) concentrations measured in different samples from the same depth in a sedimentary sequence. But unlike the isochron method, P-PINI applies a stochastic approach to simulate a wide range of possible pre-depositional exposure and erosion histories for each individual sample. These different pre-burial histories (unique to each sample) are then integrated with the constraint that all samples share a common burial history at the sink. Where cosmogenic nuclide data (or other chronometric data, e.g., OSL) are available for multiple sites, Bayesian inference modelling can impose a priori relative age constraints, or estimates on the maximum duration of sediment storage.
In this presentation, we extend P-PINI to explore how sediment storage and reworking (i.e., a range of burial depths and durations) between source and sink affects burial age estimates. Significant intermediate storage is characteristic of large river systems, such as the Danube River. Using cosmogenic 10Be-26Al concentrations measured in fluvial gravels at Gänserndorf and Schlosshof, two terraces along the Danube River in the Vienna Basin (Braumann et al., 2019. Quat. Int. 509. 87-102), we examine how the burial ages at these two sites are a function of the pre-burial history experienced by the samples.
How to cite: Nørgaard, J., Jansen, J., Neuhuber, S., Ruszkizcay-Rüdiger, Z., Braumann, S., Feibig, M., Häuselmann, P., and Faurschou Knudsen, M.: P-PINI: a new inversion method for sediment-burial dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14848, https://doi.org/10.5194/egusphere-egu21-14848, 2021.
EGU21-13808 | vPICO presentations | GM2.12
Applicability of the authigenic 10 Be/ 9 Be dating to deltaic deposits: Preliminary results from the Slanicul de Buzau section, Pliocene, Romania.Kishan Aherwar, Michal Šujan, Katarína Šarinová, Régis Braucher, Arjan de Leeuw, Andrej Chyba, and Aster Team
EGU21-12406 | vPICO presentations | GM2.12
Applicability and challenges for the authigenic 10Be/9Be dating as revealed by studies from the Pannonian Basin realmMichal Šujan, Régis Braucher, Michal Kováč, Kishan Aherwar, Imre Magyar, Zsófia Ruszkiczay-Rüdiger, Andrej Chyba, Orsolya Sztanó, Dániel Botka, Klement Fordinál, Matúš Tibenský, Peter Joniak, Samuel Rybár, and Bernhard Salcher and the AsterTeam
Bourlès et al. (1989: Geochim. Cosmochim. Acta) suggested that authigenic 10Be/9Be ratio could provide a geochronological tool to date deposition of clay-bearing sediment settled in a water column up to 14 Ma old. It is based on ratio of atmospheric cosmogenic radionuclide 10Be delivered to depositional environments by precipitation and stable 9Be extracted from rock massifs by chemical weathering. Determination of the initial 10Be/9Be ratio is essential for efficient application of the dating and may vary spatially as well as in time due to changes in drainage basins, depositional environments, climate, and other factors. The potential of the authigenic 10Be/9Be dating was evaluated during last years in the Pannonian Basin realm, located in Central Europe. This contribution summarizes successful applications as well as discovered problems and challenges, which motivate the ongoing research.
Two initial 10Be/9Be ratios were established from Holocene alluvial and lacustrine clays in the Danube Basin (Šujan et al., 2016: Glob. Planet. Change). The dating was applied to shallow to deep-water sediments deposited in Lake Pannon within the Danube Basin, and helped to constrain paleogeographic changes in the age range of 11.6–3 Ma. Application of the method to the post-rift alluvial succession with high subsidence rates of 50–400 m/Ma in the range of ~9.5–6.0 Ma yielded data consistent with other geochronological proxies (Šujan et al., 2020: Sed. Geol.; Joniak et al., 2020: Palaeo3). The fast accumulation and tectonic quiescence likely provided stable environmental conditions favorable for the dating method applicability.
Lacustrine and deltaic deposits of Lake Pannon were analyzed from cores of Paks boreholes in the central part of the Pannonian Basin. The resulting authigenic 10Be/9Be ages are generally in agreement with magnetostratigraphic age constraints correlated using seismic stratigraphy (Magyar et al., 2019: Földt. Közl.). Outliers with relative enrichment of 10Be appear in most distal facies, where low terrestrial 9Be input is expected.
A study of turbidite deposits from the Transylvanian Basin allowed to compare the established lacustrine initial 10Be/9Be with a ratio independently calculated from Ar/Ar dated horizon (Botka et al., 2019: Austrian J. Earth. Sci.). Majority of samples provided a good fit with other age proxies, while one sedimentary interval exhibits twofold increase of 10Be/9Be probably indicating variability in the environmental conditions (Baranyi et al., 2021: Rev. Palaeobot. Palyn.).
An order of magnitude higher authigenic 10Be/9Be comparing to the established initial ratios were obtained from supposed early Pleistocene sediments from the locality Sollenau in the Vienna Basin. The visual appearance implies, that secondary pedogenic processes might be responsible for a post-depositional input of 10Be (Willenbring, von Blanckenburg, 2010: Earth. Sci. Rev.). Another case of high 10Be/9Be preventing age calculation was observed in a Pleistocene alluvial environment with intense loess input.
An ongoing research aims to determine the effects of changes in depositional process, sediment source proximity and provenance on the applicability of the dating method. This research was financially supported by the Slovak Research and Development Agency under contract APVV-16-0121 and by the Hungarian National Research, Development and Innovation Office under contract NKFIH-116618.
How to cite: Šujan, M., Braucher, R., Kováč, M., Aherwar, K., Magyar, I., Ruszkiczay-Rüdiger, Z., Chyba, A., Sztanó, O., Botka, D., Fordinál, K., Tibenský, M., Joniak, P., Rybár, S., and Salcher, B. and the AsterTeam: Applicability and challenges for the authigenic 10Be/9Be dating as revealed by studies from the Pannonian Basin realm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12406, https://doi.org/10.5194/egusphere-egu21-12406, 2021.
Please decide on your access
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Bourlès et al. (1989: Geochim. Cosmochim. Acta) suggested that authigenic 10Be/9Be ratio could provide a geochronological tool to date deposition of clay-bearing sediment settled in a water column up to 14 Ma old. It is based on ratio of atmospheric cosmogenic radionuclide 10Be delivered to depositional environments by precipitation and stable 9Be extracted from rock massifs by chemical weathering. Determination of the initial 10Be/9Be ratio is essential for efficient application of the dating and may vary spatially as well as in time due to changes in drainage basins, depositional environments, climate, and other factors. The potential of the authigenic 10Be/9Be dating was evaluated during last years in the Pannonian Basin realm, located in Central Europe. This contribution summarizes successful applications as well as discovered problems and challenges, which motivate the ongoing research.
Two initial 10Be/9Be ratios were established from Holocene alluvial and lacustrine clays in the Danube Basin (Šujan et al., 2016: Glob. Planet. Change). The dating was applied to shallow to deep-water sediments deposited in Lake Pannon within the Danube Basin, and helped to constrain paleogeographic changes in the age range of 11.6–3 Ma. Application of the method to the post-rift alluvial succession with high subsidence rates of 50–400 m/Ma in the range of ~9.5–6.0 Ma yielded data consistent with other geochronological proxies (Šujan et al., 2020: Sed. Geol.; Joniak et al., 2020: Palaeo3). The fast accumulation and tectonic quiescence likely provided stable environmental conditions favorable for the dating method applicability.
Lacustrine and deltaic deposits of Lake Pannon were analyzed from cores of Paks boreholes in the central part of the Pannonian Basin. The resulting authigenic 10Be/9Be ages are generally in agreement with magnetostratigraphic age constraints correlated using seismic stratigraphy (Magyar et al., 2019: Földt. Közl.). Outliers with relative enrichment of 10Be appear in most distal facies, where low terrestrial 9Be input is expected.
A study of turbidite deposits from the Transylvanian Basin allowed to compare the established lacustrine initial 10Be/9Be with a ratio independently calculated from Ar/Ar dated horizon (Botka et al., 2019: Austrian J. Earth. Sci.). Majority of samples provided a good fit with other age proxies, while one sedimentary interval exhibits twofold increase of 10Be/9Be probably indicating variability in the environmental conditions (Baranyi et al., 2021: Rev. Palaeobot. Palyn.).
An order of magnitude higher authigenic 10Be/9Be comparing to the established initial ratios were obtained from supposed early Pleistocene sediments from the locality Sollenau in the Vienna Basin. The visual appearance implies, that secondary pedogenic processes might be responsible for a post-depositional input of 10Be (Willenbring, von Blanckenburg, 2010: Earth. Sci. Rev.). Another case of high 10Be/9Be preventing age calculation was observed in a Pleistocene alluvial environment with intense loess input.
An ongoing research aims to determine the effects of changes in depositional process, sediment source proximity and provenance on the applicability of the dating method. This research was financially supported by the Slovak Research and Development Agency under contract APVV-16-0121 and by the Hungarian National Research, Development and Innovation Office under contract NKFIH-116618.
How to cite: Šujan, M., Braucher, R., Kováč, M., Aherwar, K., Magyar, I., Ruszkiczay-Rüdiger, Z., Chyba, A., Sztanó, O., Botka, D., Fordinál, K., Tibenský, M., Joniak, P., Rybár, S., and Salcher, B. and the AsterTeam: Applicability and challenges for the authigenic 10Be/9Be dating as revealed by studies from the Pannonian Basin realm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12406, https://doi.org/10.5194/egusphere-egu21-12406, 2021.
EGU21-14132 | vPICO presentations | GM2.12
A tale of two bogs - new 10Be production rates from UK and NZ calibrated by basal 14C agesDavid Fink, Philip Hughes, Reka Fulop, Klaus Wilcken, Patrick Adams, Craig Woodward, James Shulmeister, Toshiyuki Fujioka, and Peter Ryan
Cosmogenic production rates (PRs) are the essential conversion factor between AMS cosmogenic concentrations and absolute exposure ages. The accuracy of cosmogenic glacial chronologies and reliability in their comparison to other paleoclimate systems is largely contingent on the precision and accuracy of the adopted production rate. This is particularly critical in determining past glacial geochronologies at the scale of millennial temporal resolution. Most PR calibrations are carried out at deglaciation sites where radiocarbon provides the independent chronometric control usually based on 14C ages in basal sediments or varves from lake or bog cores which is assumed to represent the minimum age for glacial retreat. Under these conditions and hence provide PRs as maximum values. Given that today most AMS facilities can deliver 10-Be, 26-Al and 36-Cl data with total analytical errors less than 2% ( for 10 ka exposure), the precision of a PR remains largely dependent on the error in the independent chronology and accuracy of AMS standards. The history over the past 20 years of the ever-decreasing value of SLHL 10-Be cosmogenic spallation PRs from initial estimates of about 7 atoms/g/a to the current ‘accepted‘ (global average) values of ~4 atoms/g/a, is an interesting story in itself and demonstrates the complexity in such determinations.
Over the past few years new web-based calculators are now available to calculate uniformly new production rates from either new data or combinations of any set of published data (CRONUS-Earth, CRONUS-UW, CosmoCalc, ICE-D, CREp). This delivers a means by which new production rates can be seamlessly integrated and compared using identical constants, methods and statistics that were used to generate (currently accepted) global average or regional production rates.
For the British Isles, there are a number of 10-Be reference sites that give PRs (Lm scheme) between 3.89±3% atoms/g/a (Putnam, QG, v50, 2019) to 4.20±1% atoms/g/a (Small, JQS, v30, 2015) which convert to 3.95 and 4.28, respectively, using datasets in the ICE-D calculator). This difference in 10-Be spallation PRs has recently raised some debate and challenges for the timing of the local-LGM and demise of the British Ice Sheet. This work provides a new British Isles site specific 10Be PR from the Arenig Mountains in North Wales where radiocarbon dating of basal sediments from a bog core associated with a series of nearby cirque moraines provides independent age control. Similarly in the South Island of New Zealand, the current accepted 10Be PR is 3.76±2% (Putnam, QG 2009; converts to 3.94±1% using ICE-D) and is the only available PR that is used for these southern hemispheric glacial sites. This work provides a new Australasian site specific 10Be PR from Arthurs Pass retreat moraines where radiocarbon dating of basal sediments from three cores extracted from a bog impounded by the moraine provides independent age control.
How to cite: Fink, D., Hughes, P., Fulop, R., Wilcken, K., Adams, P., Woodward, C., Shulmeister, J., Fujioka, T., and Ryan, P.: A tale of two bogs - new 10Be production rates from UK and NZ calibrated by basal 14C ages , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14132, https://doi.org/10.5194/egusphere-egu21-14132, 2021.
Cosmogenic production rates (PRs) are the essential conversion factor between AMS cosmogenic concentrations and absolute exposure ages. The accuracy of cosmogenic glacial chronologies and reliability in their comparison to other paleoclimate systems is largely contingent on the precision and accuracy of the adopted production rate. This is particularly critical in determining past glacial geochronologies at the scale of millennial temporal resolution. Most PR calibrations are carried out at deglaciation sites where radiocarbon provides the independent chronometric control usually based on 14C ages in basal sediments or varves from lake or bog cores which is assumed to represent the minimum age for glacial retreat. Under these conditions and hence provide PRs as maximum values. Given that today most AMS facilities can deliver 10-Be, 26-Al and 36-Cl data with total analytical errors less than 2% ( for 10 ka exposure), the precision of a PR remains largely dependent on the error in the independent chronology and accuracy of AMS standards. The history over the past 20 years of the ever-decreasing value of SLHL 10-Be cosmogenic spallation PRs from initial estimates of about 7 atoms/g/a to the current ‘accepted‘ (global average) values of ~4 atoms/g/a, is an interesting story in itself and demonstrates the complexity in such determinations.
Over the past few years new web-based calculators are now available to calculate uniformly new production rates from either new data or combinations of any set of published data (CRONUS-Earth, CRONUS-UW, CosmoCalc, ICE-D, CREp). This delivers a means by which new production rates can be seamlessly integrated and compared using identical constants, methods and statistics that were used to generate (currently accepted) global average or regional production rates.
For the British Isles, there are a number of 10-Be reference sites that give PRs (Lm scheme) between 3.89±3% atoms/g/a (Putnam, QG, v50, 2019) to 4.20±1% atoms/g/a (Small, JQS, v30, 2015) which convert to 3.95 and 4.28, respectively, using datasets in the ICE-D calculator). This difference in 10-Be spallation PRs has recently raised some debate and challenges for the timing of the local-LGM and demise of the British Ice Sheet. This work provides a new British Isles site specific 10Be PR from the Arenig Mountains in North Wales where radiocarbon dating of basal sediments from a bog core associated with a series of nearby cirque moraines provides independent age control. Similarly in the South Island of New Zealand, the current accepted 10Be PR is 3.76±2% (Putnam, QG 2009; converts to 3.94±1% using ICE-D) and is the only available PR that is used for these southern hemispheric glacial sites. This work provides a new Australasian site specific 10Be PR from Arthurs Pass retreat moraines where radiocarbon dating of basal sediments from three cores extracted from a bog impounded by the moraine provides independent age control.
How to cite: Fink, D., Hughes, P., Fulop, R., Wilcken, K., Adams, P., Woodward, C., Shulmeister, J., Fujioka, T., and Ryan, P.: A tale of two bogs - new 10Be production rates from UK and NZ calibrated by basal 14C ages , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14132, https://doi.org/10.5194/egusphere-egu21-14132, 2021.
EGU21-16090 | vPICO presentations | GM2.12
Current stability to improve AMS precision for cosmogenic 10Be applicationsAna Carracedo Plumed, Derek Fabel, and Richard Shanks
With the present AMS 10Be uncertainties (~2% best case scenario) and the increasing need for more precise cosmogenic 10Be data it has become imperative to improve AMS measurements. Precision depends on counting statistics which in turn depend on ion beam current stability and sample longevity. The ion beam currents are dependent on the metal matrix in which BeO is dispersed; the matrix:BeO ratio; homogeneity of the mixture and the packing of the AMS cathode. We aim to understand the effect of cathode homogeneity in generating stable beam currents. We have performed a series of experiments using different metal matrices (Nb, Ag, Fe) in different forms (solid and in solution). The metals have been added to different stages of the sample precipitation process and both BeO and Be(OH)2 have been pressed into AMS cathodes and analysed at SUERC. We will discuss results of these experiments and introduce an innovative use of polyoxometalates (molibdanate and niobate) to create a homogeneous compound that has the potential to generate stable ion beam currents from sputter ion sources.
How to cite: Carracedo Plumed, A., Fabel, D., and Shanks, R.: Current stability to improve AMS precision for cosmogenic 10Be applications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16090, https://doi.org/10.5194/egusphere-egu21-16090, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
With the present AMS 10Be uncertainties (~2% best case scenario) and the increasing need for more precise cosmogenic 10Be data it has become imperative to improve AMS measurements. Precision depends on counting statistics which in turn depend on ion beam current stability and sample longevity. The ion beam currents are dependent on the metal matrix in which BeO is dispersed; the matrix:BeO ratio; homogeneity of the mixture and the packing of the AMS cathode. We aim to understand the effect of cathode homogeneity in generating stable beam currents. We have performed a series of experiments using different metal matrices (Nb, Ag, Fe) in different forms (solid and in solution). The metals have been added to different stages of the sample precipitation process and both BeO and Be(OH)2 have been pressed into AMS cathodes and analysed at SUERC. We will discuss results of these experiments and introduce an innovative use of polyoxometalates (molibdanate and niobate) to create a homogeneous compound that has the potential to generate stable ion beam currents from sputter ion sources.
How to cite: Carracedo Plumed, A., Fabel, D., and Shanks, R.: Current stability to improve AMS precision for cosmogenic 10Be applications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16090, https://doi.org/10.5194/egusphere-egu21-16090, 2021.
EGU21-10247 | vPICO presentations | GM2.12
Cosmogenic 3He in detrital Pt-alloy grains: tracing the accumulation of critical metalsOlga Yakubovich, Finlay Stuart, Alexander Mochalov, and Roman Palamarchuk
The application of cosmogenic noble gases (3He and 21Ne) in detrital grains to quantify sediment transport rates and storage timescales is largely undeveloped. We have previously shown that cosmogenic He can be measured in single grains (Yakubovich et al. 2019). The low He diffusion rate and the chemical and/or physical robustness of metal alloys (eg Au, Ag, Cu, Pt, Fe) means the technique has potential to determine how critical metals accumulate at the Earth surface. In an effort to determine how long detrital Pt-alloy grains spend travelling to placer deposits we have measured cosmogenic3He concentrations in 60 (0.5–7 mg) grains of isoferroplatinum (Pt3Fe) from the world largest alluvial Pt placer deposits in the Kondyor-Uorgalan rivers in Khabarovsk region, and the Is-Turinsk and Nyas’ma river systems in Middle Urals, Russia.
In both systems, there are no significant cosmogenic 3He in the grains from the low order streams that drain the source rock. 3Hecosconcentrations in Pt grains from distant placers (30 km) varies in order of magnitude from 0.3 to 30 x 107at g-1in grains in Uorgalan river, 5 to 40 x 107at g-1in Glubokinskoe placer deposit (Is river) and 20 to 70 x 107at g-1in the Generalka deposit (Nyas’ma river). Converting this to surface residence times (P = 25 at g y-1, Yakubovich et al., 2019) yields model exposure durations of0.1–10, 3–20 and 13–38 Myr for grains from the Uorgalan, Glubokinskoe and Generalka deposits respectively. Assuming that all grains were extracted from shielded locations this exposure ages indicate the total time of transport and residence of the grains on river bed surface prior to final deposition.
Pt grains are added to the river system constantly. If we assume that the average transport conditions are essentially identical for all grains, then the difference between the maximum and minimum exposure ages within the same location indicates the total duration of placer supply from the source rock. For the Urals it is equal for 17–25 Myr, while for Kondyor-Uorgalan placer it is 10 Myr. This is in a good agreement with geological observations. Within Kondyor-Uorgalan placer deposit the age of the alluvium varies from Neogene to Quaternary, while in the Urals Pt-bearing Jurassic, Neogene and Quaternary fluvial sediments are distinguished within the placers.
Paleo peneplain surfaces are established nearby the Kondyor massif and pre-date the most productive platinum sands. Several stages of peneplenisation are evident in the Urals from thick weathering crusts. The exposure ages indicate10’s million-year scale of transport/deposition histories of detrital Pt alloys, which might result of multiple redeposition of material during long term accumulation of cosmogenic 3He during peneplenisation.
Yakubovich O., Stuart F.M., Nesterenok A. and Carracedo A. (2019). Chem. Geol. 517, 22-33.
How to cite: Yakubovich, O., Stuart, F., Mochalov, A., and Palamarchuk, R.: Cosmogenic 3He in detrital Pt-alloy grains: tracing the accumulation of critical metals, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10247, https://doi.org/10.5194/egusphere-egu21-10247, 2021.
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The application of cosmogenic noble gases (3He and 21Ne) in detrital grains to quantify sediment transport rates and storage timescales is largely undeveloped. We have previously shown that cosmogenic He can be measured in single grains (Yakubovich et al. 2019). The low He diffusion rate and the chemical and/or physical robustness of metal alloys (eg Au, Ag, Cu, Pt, Fe) means the technique has potential to determine how critical metals accumulate at the Earth surface. In an effort to determine how long detrital Pt-alloy grains spend travelling to placer deposits we have measured cosmogenic3He concentrations in 60 (0.5–7 mg) grains of isoferroplatinum (Pt3Fe) from the world largest alluvial Pt placer deposits in the Kondyor-Uorgalan rivers in Khabarovsk region, and the Is-Turinsk and Nyas’ma river systems in Middle Urals, Russia.
In both systems, there are no significant cosmogenic 3He in the grains from the low order streams that drain the source rock. 3Hecosconcentrations in Pt grains from distant placers (30 km) varies in order of magnitude from 0.3 to 30 x 107at g-1in grains in Uorgalan river, 5 to 40 x 107at g-1in Glubokinskoe placer deposit (Is river) and 20 to 70 x 107at g-1in the Generalka deposit (Nyas’ma river). Converting this to surface residence times (P = 25 at g y-1, Yakubovich et al., 2019) yields model exposure durations of0.1–10, 3–20 and 13–38 Myr for grains from the Uorgalan, Glubokinskoe and Generalka deposits respectively. Assuming that all grains were extracted from shielded locations this exposure ages indicate the total time of transport and residence of the grains on river bed surface prior to final deposition.
Pt grains are added to the river system constantly. If we assume that the average transport conditions are essentially identical for all grains, then the difference between the maximum and minimum exposure ages within the same location indicates the total duration of placer supply from the source rock. For the Urals it is equal for 17–25 Myr, while for Kondyor-Uorgalan placer it is 10 Myr. This is in a good agreement with geological observations. Within Kondyor-Uorgalan placer deposit the age of the alluvium varies from Neogene to Quaternary, while in the Urals Pt-bearing Jurassic, Neogene and Quaternary fluvial sediments are distinguished within the placers.
Paleo peneplain surfaces are established nearby the Kondyor massif and pre-date the most productive platinum sands. Several stages of peneplenisation are evident in the Urals from thick weathering crusts. The exposure ages indicate10’s million-year scale of transport/deposition histories of detrital Pt alloys, which might result of multiple redeposition of material during long term accumulation of cosmogenic 3He during peneplenisation.
Yakubovich O., Stuart F.M., Nesterenok A. and Carracedo A. (2019). Chem. Geol. 517, 22-33.
How to cite: Yakubovich, O., Stuart, F., Mochalov, A., and Palamarchuk, R.: Cosmogenic 3He in detrital Pt-alloy grains: tracing the accumulation of critical metals, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10247, https://doi.org/10.5194/egusphere-egu21-10247, 2021.
EGU21-15013 | vPICO presentations | GM2.12
Understanding 21Ne inventories in Precambrian basement below the Great Unconformity in EstoniaAdrian M. Hall, Fin Stuart, Kalle Kirsimae, and Peeter Somelar
Stable cosmogenic Ne isotopes are widely used to determine the erosion rate of slowly-eroding land surfaces through the Cenozoic. Constraining erosion and surface exposure back in Earth history remains a challenge largely due to the presence of Ne isotopes generated by natural decay processes over the lifetime of rocks. Prospects are best when cosmogenic nuclide production has been significant and nucleogenic Ne production is low and can be quantified. We have explored the limits of palaeo-cosmogenic Ne in one of the Earth’s most extensive erosion surfaces, the late Precambrian Great Unconformity in Estonia. Here deep kaolinitic saprolites formed on Baltica prior to the deposition of Late Ediacaran quartz sandstones. On the basis of geochemical mass balance the duration of saprolite development is estimated to be of the order of a few Myr.
Borehole F163 samples a section through still-buried weathered unconformity that includes a saprolite surface consistent with negligible erosion during the marine transgression. Samples from the unconformity have 21Ne concentrations (>108 atoms/g) that are significantly higher than shielded samples from >20 m below the unconformity. This difference is borne out by Ne isotope composition, and leads to the tanatalising prospect that Precambrian cosmogenic Ne is present in the saprolite. Using modern 21Ne production rates the palaeosols appear to record a few million years irradiation. This is broadly consistent with geochemical estimates of saprolite development. Samples from the uppermost preserved part of the weathering profile in borehole F231 have low 21Ne concentrations that are indistinguishable from deeper in the rock profile. This would require profile truncation or the redeposition of weathered material. The borehole is located on the western flank of an uplifted basement block rising ca 130 m above the typical Precambrian basement level in the area and likely that the thick regolith contains material eroded from the uplifted basement units. Clearly these are early days and quantifying surface exposure in deep time will require effort in field as well as the lab.
How to cite: Hall, A. M., Stuart, F., Kirsimae, K., and Somelar, P.: Understanding 21Ne inventories in Precambrian basement below the Great Unconformity in Estonia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15013, https://doi.org/10.5194/egusphere-egu21-15013, 2021.
Stable cosmogenic Ne isotopes are widely used to determine the erosion rate of slowly-eroding land surfaces through the Cenozoic. Constraining erosion and surface exposure back in Earth history remains a challenge largely due to the presence of Ne isotopes generated by natural decay processes over the lifetime of rocks. Prospects are best when cosmogenic nuclide production has been significant and nucleogenic Ne production is low and can be quantified. We have explored the limits of palaeo-cosmogenic Ne in one of the Earth’s most extensive erosion surfaces, the late Precambrian Great Unconformity in Estonia. Here deep kaolinitic saprolites formed on Baltica prior to the deposition of Late Ediacaran quartz sandstones. On the basis of geochemical mass balance the duration of saprolite development is estimated to be of the order of a few Myr.
Borehole F163 samples a section through still-buried weathered unconformity that includes a saprolite surface consistent with negligible erosion during the marine transgression. Samples from the unconformity have 21Ne concentrations (>108 atoms/g) that are significantly higher than shielded samples from >20 m below the unconformity. This difference is borne out by Ne isotope composition, and leads to the tanatalising prospect that Precambrian cosmogenic Ne is present in the saprolite. Using modern 21Ne production rates the palaeosols appear to record a few million years irradiation. This is broadly consistent with geochemical estimates of saprolite development. Samples from the uppermost preserved part of the weathering profile in borehole F231 have low 21Ne concentrations that are indistinguishable from deeper in the rock profile. This would require profile truncation or the redeposition of weathered material. The borehole is located on the western flank of an uplifted basement block rising ca 130 m above the typical Precambrian basement level in the area and likely that the thick regolith contains material eroded from the uplifted basement units. Clearly these are early days and quantifying surface exposure in deep time will require effort in field as well as the lab.
How to cite: Hall, A. M., Stuart, F., Kirsimae, K., and Somelar, P.: Understanding 21Ne inventories in Precambrian basement below the Great Unconformity in Estonia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15013, https://doi.org/10.5194/egusphere-egu21-15013, 2021.
GM3.17 – Processes and timescales of sediment production, transport, and deposition from source to sink.
EGU21-12536 | vPICO presentations | GM3.17
Rapidly eroding hilltops are surprisingly smooth: ridgetop curvature varies with the square root of erosion rateSimon M. Mudd, Emmanuel J. Gabet, Ryan W. Wood, Stuart W. D. Grieve, Steven A. Binnie, and Tibor J. Dunai
The shape of soil-mantled hillslopes is typically attributed to erosion rate and the transport efficiency of the various processes that contribute to soil creep. While climate is generally hypothesized to have an important influence on soil creep rates, a lack of uniformity in the measurement of transport efficiency has been an obstacle to evaluating the controls on this important landscape parameter. We addressed this problem by compiling a data set in which the transport efficiency has been calculated using a single method, the analysis of hilltop curvatures using 1-m LiDAR data, and the erosion rates have also been determined via a single method, in-situ cosmogenic 10Be concentrations. Moreover, to control for lithology, we chose sites that are only underlain by resistant bedrock. The sites span a range of erosion rates (6 – 1373 mm/kyr), annual precipitation (31 – 320 cm/yr), and aridity index (0.08 – 1.38). Surprisingly, we find that hilltop curvature varies with the square root of erosion rate, whereas previous studies predict a linear relationship. In addition, we find that the inferred transport coefficient also varies with the square root of erosion rate but is insensitive to climate. We explore various mechanisms that might link the transport coefficient to the erosion rate and conclude that present theory regarding soil-mantled hillslopes is unable to explain our results and is, therefore, incomplete. Finally, we tentatively suggest that bedrock processes may be responsible for the shape of hillslope profiles at our sites.
How to cite: Mudd, S. M., Gabet, E. J., Wood, R. W., Grieve, S. W. D., Binnie, S. A., and Dunai, T. J.: Rapidly eroding hilltops are surprisingly smooth: ridgetop curvature varies with the square root of erosion rate , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12536, https://doi.org/10.5194/egusphere-egu21-12536, 2021.
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The shape of soil-mantled hillslopes is typically attributed to erosion rate and the transport efficiency of the various processes that contribute to soil creep. While climate is generally hypothesized to have an important influence on soil creep rates, a lack of uniformity in the measurement of transport efficiency has been an obstacle to evaluating the controls on this important landscape parameter. We addressed this problem by compiling a data set in which the transport efficiency has been calculated using a single method, the analysis of hilltop curvatures using 1-m LiDAR data, and the erosion rates have also been determined via a single method, in-situ cosmogenic 10Be concentrations. Moreover, to control for lithology, we chose sites that are only underlain by resistant bedrock. The sites span a range of erosion rates (6 – 1373 mm/kyr), annual precipitation (31 – 320 cm/yr), and aridity index (0.08 – 1.38). Surprisingly, we find that hilltop curvature varies with the square root of erosion rate, whereas previous studies predict a linear relationship. In addition, we find that the inferred transport coefficient also varies with the square root of erosion rate but is insensitive to climate. We explore various mechanisms that might link the transport coefficient to the erosion rate and conclude that present theory regarding soil-mantled hillslopes is unable to explain our results and is, therefore, incomplete. Finally, we tentatively suggest that bedrock processes may be responsible for the shape of hillslope profiles at our sites.
How to cite: Mudd, S. M., Gabet, E. J., Wood, R. W., Grieve, S. W. D., Binnie, S. A., and Dunai, T. J.: Rapidly eroding hilltops are surprisingly smooth: ridgetop curvature varies with the square root of erosion rate , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12536, https://doi.org/10.5194/egusphere-egu21-12536, 2021.
EGU21-839 | vPICO presentations | GM3.17 | Highlight
From the Landslide to the Mangrove; Coupling Sediment Supply Pulses and River Sediment Deposits in the context of Climate Change in Thailand.Jerome Curoy, Raymond Ward, and John Barlow
In Thailand landslides and flooding are two major natural disasters affecting more than 11 million people living in coastal provinces. Such events have significant human and economic impacts. For example, in 1988, landslides resulted in 373 deaths and caused up to US$80 million in damage (Tanavud, 2008); in 2011, floods and landslides affected more than two million people and killed 53 across Southern Thailand with a village of about 100 households being buried by one large slide (EarthObservatory, 2021). Landslides in the Krabi province in Thailand are predominantly shallow and rainfall-induced, they also represent the main source of sediment pulses for coastal environments such as mangroves and beaches. This study aims at investigating the link between sediment availability from 3 river catchments in the province of Krabi in Southern Thailand and sedimentation rate evolution in mangroves directly downstream in order to understand coastal the sediment shortages and therefore coastal erosion in that area.
Landslide inventories were evaluated using high resolution imagery (<10m) such as aerial photographs, Theos and EO-1 satellite imagery, Google Earth historical tool covering a time period from 2007 to present. Calculations of the surface areas and volumes of landslides was calculated in ArcMap using the formulae developed by Larsen et al. (2010). Landslide erosion was modelled using an approach based upon the negative power law scaling properties of rockfall magnitude–frequency distribution to establish total volumes of sediment for specific years or seasons.
Core samples taken in the mangroves near the river mouths were used to identify markers of landslide events and associated sediment cascades based on grain size distribution and 137Cs dating.
Preliminary results show sedimentation rates in the mangroves from 0.9 to 2 mm/year since 1963 and sediment volumes made available to transport from 0.3 to 68300 m3/year since 2007 across the 3 catchments.
Grain size analysis shows variations of the D50 and the sorting coefficient throughout the sediment recording indicators of landslides and high intensity rainfall events.
How to cite: Curoy, J., Ward, R., and Barlow, J.: From the Landslide to the Mangrove; Coupling Sediment Supply Pulses and River Sediment Deposits in the context of Climate Change in Thailand., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-839, https://doi.org/10.5194/egusphere-egu21-839, 2021.
In Thailand landslides and flooding are two major natural disasters affecting more than 11 million people living in coastal provinces. Such events have significant human and economic impacts. For example, in 1988, landslides resulted in 373 deaths and caused up to US$80 million in damage (Tanavud, 2008); in 2011, floods and landslides affected more than two million people and killed 53 across Southern Thailand with a village of about 100 households being buried by one large slide (EarthObservatory, 2021). Landslides in the Krabi province in Thailand are predominantly shallow and rainfall-induced, they also represent the main source of sediment pulses for coastal environments such as mangroves and beaches. This study aims at investigating the link between sediment availability from 3 river catchments in the province of Krabi in Southern Thailand and sedimentation rate evolution in mangroves directly downstream in order to understand coastal the sediment shortages and therefore coastal erosion in that area.
Landslide inventories were evaluated using high resolution imagery (<10m) such as aerial photographs, Theos and EO-1 satellite imagery, Google Earth historical tool covering a time period from 2007 to present. Calculations of the surface areas and volumes of landslides was calculated in ArcMap using the formulae developed by Larsen et al. (2010). Landslide erosion was modelled using an approach based upon the negative power law scaling properties of rockfall magnitude–frequency distribution to establish total volumes of sediment for specific years or seasons.
Core samples taken in the mangroves near the river mouths were used to identify markers of landslide events and associated sediment cascades based on grain size distribution and 137Cs dating.
Preliminary results show sedimentation rates in the mangroves from 0.9 to 2 mm/year since 1963 and sediment volumes made available to transport from 0.3 to 68300 m3/year since 2007 across the 3 catchments.
Grain size analysis shows variations of the D50 and the sorting coefficient throughout the sediment recording indicators of landslides and high intensity rainfall events.
How to cite: Curoy, J., Ward, R., and Barlow, J.: From the Landslide to the Mangrove; Coupling Sediment Supply Pulses and River Sediment Deposits in the context of Climate Change in Thailand., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-839, https://doi.org/10.5194/egusphere-egu21-839, 2021.
EGU21-7389 | vPICO presentations | GM3.17
Downstream evolution of grain size in extremely mobile post-earthquake debris flows, ChinaErin L. Harvey, Tristram C. Hales, Daniel E. J. Hobley, Xuanmei Fan, Jie Liu, Qiang Xu, and Runqiu Huang
Large, catchment transitioning debris flows are an important mechanism for transporting sediment from hillslopes into higher order channels. Extremely large flows can exceed volumes of 109 m3, however even flows with volumes of ~103 m3 can lead to fatalities and extensive damage. Few processes transport a wider range of grain sizes than debris flows, which can transport grains from clays to 10 m boulders. While the structure of debris flows can often be inferred by their deposits, the range of grain sizes presents a challenge for their interpretation. Debris flow grain size distributions can be used to constrain debris flow runout due to their effect on excess pore pressure dissipation. Currently, there is limited data available for the entire grain size distribution of debris flow deposits in the field.
We constrained the entire grain size distribution for two extremely large (>1 km in length) post-earthquake debris flows in Sichuan Province, China. These debris flows were triggered in August 2019 after an extreme rainfall event occurred close to the epicentre of the 2008 Wenchuan earthquake. We sampled the debris flows in November 2019 at intervals of 200 m and 500 m, respectively. At each site, we used a combination of field and laboratory sieving to obtain the coarse and fine fraction for both the surface and subsurface. We dug 1 m x 1 m x 0.5 m pits, excavating each layer at 10 cm depth increments. We sieved these increments into five size fractions in the field, including < 1 cm. We sieved 1 kg of the <1 cm fraction in the laboratory to estimate the distribution of the finest grains. The coarse surface fraction was then independently constrained using photogrammetry. Preliminary results for one debris flow show that the distribution of fine grains (~<4 mm) is consistent both laterally and vertically across the runout. This suggests that the processes occurring vertically and laterally during deposition result in the consistent distribution of fines.
How to cite: Harvey, E. L., Hales, T. C., Hobley, D. E. J., Fan, X., Liu, J., Xu, Q., and Huang, R.: Downstream evolution of grain size in extremely mobile post-earthquake debris flows, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7389, https://doi.org/10.5194/egusphere-egu21-7389, 2021.
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Large, catchment transitioning debris flows are an important mechanism for transporting sediment from hillslopes into higher order channels. Extremely large flows can exceed volumes of 109 m3, however even flows with volumes of ~103 m3 can lead to fatalities and extensive damage. Few processes transport a wider range of grain sizes than debris flows, which can transport grains from clays to 10 m boulders. While the structure of debris flows can often be inferred by their deposits, the range of grain sizes presents a challenge for their interpretation. Debris flow grain size distributions can be used to constrain debris flow runout due to their effect on excess pore pressure dissipation. Currently, there is limited data available for the entire grain size distribution of debris flow deposits in the field.
We constrained the entire grain size distribution for two extremely large (>1 km in length) post-earthquake debris flows in Sichuan Province, China. These debris flows were triggered in August 2019 after an extreme rainfall event occurred close to the epicentre of the 2008 Wenchuan earthquake. We sampled the debris flows in November 2019 at intervals of 200 m and 500 m, respectively. At each site, we used a combination of field and laboratory sieving to obtain the coarse and fine fraction for both the surface and subsurface. We dug 1 m x 1 m x 0.5 m pits, excavating each layer at 10 cm depth increments. We sieved these increments into five size fractions in the field, including < 1 cm. We sieved 1 kg of the <1 cm fraction in the laboratory to estimate the distribution of the finest grains. The coarse surface fraction was then independently constrained using photogrammetry. Preliminary results for one debris flow show that the distribution of fine grains (~<4 mm) is consistent both laterally and vertically across the runout. This suggests that the processes occurring vertically and laterally during deposition result in the consistent distribution of fines.
How to cite: Harvey, E. L., Hales, T. C., Hobley, D. E. J., Fan, X., Liu, J., Xu, Q., and Huang, R.: Downstream evolution of grain size in extremely mobile post-earthquake debris flows, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7389, https://doi.org/10.5194/egusphere-egu21-7389, 2021.
EGU21-9575 | vPICO presentations | GM3.17
Suspended sediment and discharge dynamics across multiple spatial and temporal scales in a glaciated alpine environment: the case of the upper Ötztal, AustriaLena Katharina Schmidt, Till Francke, Theresa Blume, Johannes Schöber, Daniel Pfurtscheller, Stefan Achleitner, and Axel Bronstert
High alpine areas are affected disproportionately by global warming and are thus found to be in a transient state. This causes accelerating glacial retreat, which can have severe impacts on discharge and potentially sediment dynamics. Possible effects include changes in water quantities and hydrograph timing as well as changing sediment source areas and the associated magnitude and timing of transport capacities. In turn, the resulting changes in water and sediment supplies and timing have the potential to severely impact downstream ecosystems and infrastructure.
An essential step towards estimating the effects of future changes and developing sustainable management strategies is to quantify the behavior in the past and present. We therefore used the excellent data availability of discharge and suspended sediment concentrations in our study area in the upper Ötztal in Tyrol, Austria, to make such an assessment. We study discharge and suspended sediment concentrations, which have been monitored at three gauges and for a minimum of seven years in the case of the youngest gauge. The resulting nested catchment setup, with catchment sizes ranging between 98 km² and 785 km², allows us to learn about discharge and sediment fluxes and their spatial distribution, thus allowing us to quantify the relative importance of the glaciated areas as compared to the lower-lying catchment areas. It also allows us to study the temporal dynamics, such as the seasonal timing of the peaks and their interannual differences. In turn, the nested catchments allows us to investigate the spatial variability of these temporal dynamics.
The results confirm the high specific sediment yields for alpine catchments in the order of 10³ t/km² per year and higher yields in areas with higher glacier cover as well as a very pronounced seasonality.
How to cite: Schmidt, L. K., Francke, T., Blume, T., Schöber, J., Pfurtscheller, D., Achleitner, S., and Bronstert, A.: Suspended sediment and discharge dynamics across multiple spatial and temporal scales in a glaciated alpine environment: the case of the upper Ötztal, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9575, https://doi.org/10.5194/egusphere-egu21-9575, 2021.
High alpine areas are affected disproportionately by global warming and are thus found to be in a transient state. This causes accelerating glacial retreat, which can have severe impacts on discharge and potentially sediment dynamics. Possible effects include changes in water quantities and hydrograph timing as well as changing sediment source areas and the associated magnitude and timing of transport capacities. In turn, the resulting changes in water and sediment supplies and timing have the potential to severely impact downstream ecosystems and infrastructure.
An essential step towards estimating the effects of future changes and developing sustainable management strategies is to quantify the behavior in the past and present. We therefore used the excellent data availability of discharge and suspended sediment concentrations in our study area in the upper Ötztal in Tyrol, Austria, to make such an assessment. We study discharge and suspended sediment concentrations, which have been monitored at three gauges and for a minimum of seven years in the case of the youngest gauge. The resulting nested catchment setup, with catchment sizes ranging between 98 km² and 785 km², allows us to learn about discharge and sediment fluxes and their spatial distribution, thus allowing us to quantify the relative importance of the glaciated areas as compared to the lower-lying catchment areas. It also allows us to study the temporal dynamics, such as the seasonal timing of the peaks and their interannual differences. In turn, the nested catchments allows us to investigate the spatial variability of these temporal dynamics.
The results confirm the high specific sediment yields for alpine catchments in the order of 10³ t/km² per year and higher yields in areas with higher glacier cover as well as a very pronounced seasonality.
How to cite: Schmidt, L. K., Francke, T., Blume, T., Schöber, J., Pfurtscheller, D., Achleitner, S., and Bronstert, A.: Suspended sediment and discharge dynamics across multiple spatial and temporal scales in a glaciated alpine environment: the case of the upper Ötztal, Austria, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9575, https://doi.org/10.5194/egusphere-egu21-9575, 2021.
EGU21-12056 | vPICO presentations | GM3.17
Few floods govern decades of suspended sediment flux in German upland riversJan Henrik Blöthe and Thomas Hoffmann
Sediment yield from lowland rivers around the globe is often dominated by suspended sediment that also acts as a carrier for pollutants and contaminants. Achieving a deeper understanding of the suspended sediment dynamics is important for river management, but often complicated by short or discontinuous time-series and scattered surveying locations. However, suspended sediment transport is highly variable in space and time, calling for decadal observations that reflect this variability. Here we make use of >130,000 measurements on water discharge (Q) and suspended sediment concentration (SSC) from twelve stations that drain large parts of the central German uplands, to investigate the spatiotemporal variability in suspended sediment flux.
The data has been collected during working days between 1965 and 2018 in context of the suspended sediment monitoring conducted by the Federal Waterways and Shipping Administration (WSV). The contributing catchments of the twelve monitoring stations range between 2500 and 22000 km2 and cover observation periods between 27 and 53 years.
Despite roughly similar topographic and climatic conditions, average specific (suspended) sediment yield (SSY) varies between ~6 and ~29 t km2 yr-1. Highest specific yields are observed for those catchments that drain the escarpment of the Swabian cuesta landscape. Even more pronounced than the spatial variability is the interannual variability in sediment yield, with SSY for very wet years exceeding SSY for dry years more than tenfold. Separating the hydrograph into base-flow and event-flow components, we find that sediment export during event-flows accounts for 60 to 85% of the long-term SSY, with individual floods accounting for more than 90% of the annual sediment export. We conclude that high specific (suspended) sediment yields in the central German uplands are conditioned by rapidly responding catchments (i.e. large fraction of event-flow contribution) with highly erodible lithologies of the Swabian cuesta landscapes.
How to cite: Blöthe, J. H. and Hoffmann, T.: Few floods govern decades of suspended sediment flux in German upland rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12056, https://doi.org/10.5194/egusphere-egu21-12056, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Sediment yield from lowland rivers around the globe is often dominated by suspended sediment that also acts as a carrier for pollutants and contaminants. Achieving a deeper understanding of the suspended sediment dynamics is important for river management, but often complicated by short or discontinuous time-series and scattered surveying locations. However, suspended sediment transport is highly variable in space and time, calling for decadal observations that reflect this variability. Here we make use of >130,000 measurements on water discharge (Q) and suspended sediment concentration (SSC) from twelve stations that drain large parts of the central German uplands, to investigate the spatiotemporal variability in suspended sediment flux.
The data has been collected during working days between 1965 and 2018 in context of the suspended sediment monitoring conducted by the Federal Waterways and Shipping Administration (WSV). The contributing catchments of the twelve monitoring stations range between 2500 and 22000 km2 and cover observation periods between 27 and 53 years.
Despite roughly similar topographic and climatic conditions, average specific (suspended) sediment yield (SSY) varies between ~6 and ~29 t km2 yr-1. Highest specific yields are observed for those catchments that drain the escarpment of the Swabian cuesta landscape. Even more pronounced than the spatial variability is the interannual variability in sediment yield, with SSY for very wet years exceeding SSY for dry years more than tenfold. Separating the hydrograph into base-flow and event-flow components, we find that sediment export during event-flows accounts for 60 to 85% of the long-term SSY, with individual floods accounting for more than 90% of the annual sediment export. We conclude that high specific (suspended) sediment yields in the central German uplands are conditioned by rapidly responding catchments (i.e. large fraction of event-flow contribution) with highly erodible lithologies of the Swabian cuesta landscapes.
How to cite: Blöthe, J. H. and Hoffmann, T.: Few floods govern decades of suspended sediment flux in German upland rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12056, https://doi.org/10.5194/egusphere-egu21-12056, 2021.
EGU21-15401 | vPICO presentations | GM3.17
Temporal and spatial dynamic of suspended sediments fluxes and sources and morphological evolution of the bed in the middle Loire riverBrahim Hichem Belbal, Nicole Goutal, Germain Antoine, and Olivier Cerdan
The middle Loire riverbed, after its confluence with Allier, is characterised by a morphology of alternate bars more or less vegetated and possesses riverbank flood protections. The suspended particulate matter (SPM) fluxes are therefore originated from these two catchment areas that drain the eastern and southern parts of the Massif Central. The temporal dynamics of the SPM fluxes are very variable, both on an interannual scale and on the scale of a flood event. Furthermore, SPM fluxes also present high spatial heterogeneities as they are governed by complex processes of production (erosion) and transfer (storage/remobilisation). The Loire river plays an important role in supporting the French energy production by providing cooling water to several Nuclear Power Plants (NPP). However, the cooling systems of the NPPs on the middle Loire are exposed to the risk of silting. In order to ensure a safe management of water intakes and prevent the industrial risks arising from sediment transport, it is therefore imperative to understand the spatio-temporal dynamic of sediment production and transfer.
In this context, the objective of this thesis work is to provide keys to improve sediment management of the river between the two NPPs of Belleville and Dampierre. In a first place, the river flow and SPM data available at the upstream NPP of Belleville will be analysed in order to understand the temporal variations of the incoming SPM fluxes. In a second phase, a soil erosion and hydrological model will be implemented to understand the production processes in the upstream catchments. This second part will allow to determine the interactions of the SPM inputs in the river with the morphodynamics of the bed of the Loire between the two stations. We will present the methodology that has been designed to apprehend these two phases and the first results of the river SPM temporal dynamic at the Belleville NPP station.
How to cite: Belbal, B. H., Goutal, N., Antoine, G., and Cerdan, O.: Temporal and spatial dynamic of suspended sediments fluxes and sources and morphological evolution of the bed in the middle Loire river, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15401, https://doi.org/10.5194/egusphere-egu21-15401, 2021.
The middle Loire riverbed, after its confluence with Allier, is characterised by a morphology of alternate bars more or less vegetated and possesses riverbank flood protections. The suspended particulate matter (SPM) fluxes are therefore originated from these two catchment areas that drain the eastern and southern parts of the Massif Central. The temporal dynamics of the SPM fluxes are very variable, both on an interannual scale and on the scale of a flood event. Furthermore, SPM fluxes also present high spatial heterogeneities as they are governed by complex processes of production (erosion) and transfer (storage/remobilisation). The Loire river plays an important role in supporting the French energy production by providing cooling water to several Nuclear Power Plants (NPP). However, the cooling systems of the NPPs on the middle Loire are exposed to the risk of silting. In order to ensure a safe management of water intakes and prevent the industrial risks arising from sediment transport, it is therefore imperative to understand the spatio-temporal dynamic of sediment production and transfer.
In this context, the objective of this thesis work is to provide keys to improve sediment management of the river between the two NPPs of Belleville and Dampierre. In a first place, the river flow and SPM data available at the upstream NPP of Belleville will be analysed in order to understand the temporal variations of the incoming SPM fluxes. In a second phase, a soil erosion and hydrological model will be implemented to understand the production processes in the upstream catchments. This second part will allow to determine the interactions of the SPM inputs in the river with the morphodynamics of the bed of the Loire between the two stations. We will present the methodology that has been designed to apprehend these two phases and the first results of the river SPM temporal dynamic at the Belleville NPP station.
How to cite: Belbal, B. H., Goutal, N., Antoine, G., and Cerdan, O.: Temporal and spatial dynamic of suspended sediments fluxes and sources and morphological evolution of the bed in the middle Loire river, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15401, https://doi.org/10.5194/egusphere-egu21-15401, 2021.
EGU21-12666 | vPICO presentations | GM3.17
Long-term temporal structure analysis of sediment fluxes in the Upper Changjiang (Yangtze River) using a wavelet transformationNoelia Garijo, Carmelo Juez, Marwan Hassan, and Estela Nadal-Romero
Temporal fluctuations of suspended sediment fluxes are highly related with the flow and sediment regime of river networks. Flow dynamics are mainly triggered by climatic forces. Conversely, sediment regime is majorly controlled by land cover/land use changes and by human infrastructures (e.g. dams). Resulting sediment fluxes thus show a non-linear and non-stationary nature. The wavelet transformation technique emerges as a skilful tool capable of dealing with this type of data. It allows to distinguish within the full spectrum of time-scales, those which are dominant and thus govern the overall trend of the time-series. Furthermore, the temporal multiresolution wavelet technique allows to accurately denoise the discharge and SSC time-series, filtering out the high frequency intermittent physical processes which are superimposed on the main signal. In this research, we analyse a long-term dataset of discharge and sediment fluxes time-series for the Upper Changjiang (Yangtze River, China).
How to cite: Garijo, N., Juez, C., Hassan, M., and Nadal-Romero, E.: Long-term temporal structure analysis of sediment fluxes in the Upper Changjiang (Yangtze River) using a wavelet transformation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12666, https://doi.org/10.5194/egusphere-egu21-12666, 2021.
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Temporal fluctuations of suspended sediment fluxes are highly related with the flow and sediment regime of river networks. Flow dynamics are mainly triggered by climatic forces. Conversely, sediment regime is majorly controlled by land cover/land use changes and by human infrastructures (e.g. dams). Resulting sediment fluxes thus show a non-linear and non-stationary nature. The wavelet transformation technique emerges as a skilful tool capable of dealing with this type of data. It allows to distinguish within the full spectrum of time-scales, those which are dominant and thus govern the overall trend of the time-series. Furthermore, the temporal multiresolution wavelet technique allows to accurately denoise the discharge and SSC time-series, filtering out the high frequency intermittent physical processes which are superimposed on the main signal. In this research, we analyse a long-term dataset of discharge and sediment fluxes time-series for the Upper Changjiang (Yangtze River, China).
How to cite: Garijo, N., Juez, C., Hassan, M., and Nadal-Romero, E.: Long-term temporal structure analysis of sediment fluxes in the Upper Changjiang (Yangtze River) using a wavelet transformation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12666, https://doi.org/10.5194/egusphere-egu21-12666, 2021.
EGU21-5200 | vPICO presentations | GM3.17
Delayed sedimentary grainsSebastien Carretier, Laure Guerit, Rebekah Harries, Vincent Regard, Pierre Maffre, Stéphane Bonnet, Sandrine Choy, and Marcelo Farías
River sediment grains are transported and stored episodically in different reservoirs (terraces, alluvial fans, foreland basin, etc.). The residence time of sediment grains in each reservoir has important implications for the paleo-environmental interpretation established from these grains, and their stratigraphic record, as well as for soil contamination, when these grains come from contaminated sources. The recycling of old sediments, via erosion of an old reservoir (e.g. foreland basin erosion), is a known problem. What is less well recognised is that the recycling of a minority of very old grains can strongly bias the average residence time of a grain population deposited in a stratum. In this case, the time-dependent paleo-environmental properties of a population of grains, such as the degree of weathering, or the concentration of cosmogenic isotopes, can then be biased. Several lines of evidence for this phenomenon, inherent to fluvial transport processes, have emerged, though reconstructing the residence time distribution of a grain population over long times (>>ka) remains a challenge. Using a landscape evolution model coupled with grain transport, we show that at the scale of a piedmont, grains can remain several hundred ka before being evacuated. At the scale of a river in Northern Chile, we used the concentration of 10Be in individual pebbles to show that some pebbles remain stored for several tens of ka before being evacuated to the river outlet. In addition, the distribution of residence times can also provide information on the nature of the diffusive processes that control the fluxes of exported sediment. These results suggest that the characterisation of grain-by-grain properties in a grain population can not only help to avoid possible interpretation biases but also provide constraints for models of long-term fluvial sediment outfluxes.
How to cite: Carretier, S., Guerit, L., Harries, R., Regard, V., Maffre, P., Bonnet, S., Choy, S., and Farías, M.: Delayed sedimentary grains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5200, https://doi.org/10.5194/egusphere-egu21-5200, 2021.
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River sediment grains are transported and stored episodically in different reservoirs (terraces, alluvial fans, foreland basin, etc.). The residence time of sediment grains in each reservoir has important implications for the paleo-environmental interpretation established from these grains, and their stratigraphic record, as well as for soil contamination, when these grains come from contaminated sources. The recycling of old sediments, via erosion of an old reservoir (e.g. foreland basin erosion), is a known problem. What is less well recognised is that the recycling of a minority of very old grains can strongly bias the average residence time of a grain population deposited in a stratum. In this case, the time-dependent paleo-environmental properties of a population of grains, such as the degree of weathering, or the concentration of cosmogenic isotopes, can then be biased. Several lines of evidence for this phenomenon, inherent to fluvial transport processes, have emerged, though reconstructing the residence time distribution of a grain population over long times (>>ka) remains a challenge. Using a landscape evolution model coupled with grain transport, we show that at the scale of a piedmont, grains can remain several hundred ka before being evacuated. At the scale of a river in Northern Chile, we used the concentration of 10Be in individual pebbles to show that some pebbles remain stored for several tens of ka before being evacuated to the river outlet. In addition, the distribution of residence times can also provide information on the nature of the diffusive processes that control the fluxes of exported sediment. These results suggest that the characterisation of grain-by-grain properties in a grain population can not only help to avoid possible interpretation biases but also provide constraints for models of long-term fluvial sediment outfluxes.
How to cite: Carretier, S., Guerit, L., Harries, R., Regard, V., Maffre, P., Bonnet, S., Choy, S., and Farías, M.: Delayed sedimentary grains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5200, https://doi.org/10.5194/egusphere-egu21-5200, 2021.
EGU21-5834 | vPICO presentations | GM3.17
Quantitative Sediment Storage Chronology Associated with European Colonization of the Mid-Atlantic U.S. and its Application to Watershed Scale Sediment RoutingJames Pizzuto
As sediment is carried through watersheds, it may be stored in floodplains and other alluvial deposits, remaining in place for hundreds to millions of years before being remobilized and transported farther downstream. Sediment routing models based on reservoir theory can account for time-varying sediment storage and predict lags in sediment delivery imposed by sediment storage, but observational data are needed to construct and validate these models. Because of the long timescales involved, direct observations are rarely useful, but stratigraphic observations coupled with sediment dating techniques can be used to quantify the amount of sediment stored through time and its associated age and storage (or transit) time distributions. To illustrate this approach, a meta-analysis of published geologic data is used to quantify river corridor storage through time associated with European colonization of the mid-Atlantic U.S. The history of floodplain growth from Holocene to the present is summarized by empirical distributions extracted from stratigraphic data; distributions were sampled to create thousands of synthetic age-depth curves. Deposits predating European colonization range in age from >18,000 yrs. to 225 yrs. B.P. and with a median thickness of 40% of the total accumulation; sedimentation rates for these deposits are low (median = 0.06 cm/yr). The median thickness of sediments deposited between 1750 and 1900 (“legacy sediments”) comprises 36% of the total; the median accumulation rate of legacy sediments is 0.32 cm/yr. The median thickness of sediments deposited after 1950 represents 11% of total accumulation, and the median contemporary sedimentation rate of 0.26 cm/yr is statistically indistinguishable from that of legacy sediments. Synthetic vertical sequences can be recast as age distributions, and when combined with geomorphic mapping and assessment of patterns of erosion through time, as storage time distributions as well. Age and storage time distributions at 1000 yrs. B.P., in 1900 A.D., and at present are highly variable, and could be represented by many different mathematical functions, though averaged data appear to be heavy-tailed. Records of mass accumulation through time and the present and past age and storage time distributions provide useful summaries of the history of sediment storage, and can be used to calibrate and verify watershed scale sediment routing models over millennial timescales.
How to cite: Pizzuto, J.: Quantitative Sediment Storage Chronology Associated with European Colonization of the Mid-Atlantic U.S. and its Application to Watershed Scale Sediment Routing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5834, https://doi.org/10.5194/egusphere-egu21-5834, 2021.
As sediment is carried through watersheds, it may be stored in floodplains and other alluvial deposits, remaining in place for hundreds to millions of years before being remobilized and transported farther downstream. Sediment routing models based on reservoir theory can account for time-varying sediment storage and predict lags in sediment delivery imposed by sediment storage, but observational data are needed to construct and validate these models. Because of the long timescales involved, direct observations are rarely useful, but stratigraphic observations coupled with sediment dating techniques can be used to quantify the amount of sediment stored through time and its associated age and storage (or transit) time distributions. To illustrate this approach, a meta-analysis of published geologic data is used to quantify river corridor storage through time associated with European colonization of the mid-Atlantic U.S. The history of floodplain growth from Holocene to the present is summarized by empirical distributions extracted from stratigraphic data; distributions were sampled to create thousands of synthetic age-depth curves. Deposits predating European colonization range in age from >18,000 yrs. to 225 yrs. B.P. and with a median thickness of 40% of the total accumulation; sedimentation rates for these deposits are low (median = 0.06 cm/yr). The median thickness of sediments deposited between 1750 and 1900 (“legacy sediments”) comprises 36% of the total; the median accumulation rate of legacy sediments is 0.32 cm/yr. The median thickness of sediments deposited after 1950 represents 11% of total accumulation, and the median contemporary sedimentation rate of 0.26 cm/yr is statistically indistinguishable from that of legacy sediments. Synthetic vertical sequences can be recast as age distributions, and when combined with geomorphic mapping and assessment of patterns of erosion through time, as storage time distributions as well. Age and storage time distributions at 1000 yrs. B.P., in 1900 A.D., and at present are highly variable, and could be represented by many different mathematical functions, though averaged data appear to be heavy-tailed. Records of mass accumulation through time and the present and past age and storage time distributions provide useful summaries of the history of sediment storage, and can be used to calibrate and verify watershed scale sediment routing models over millennial timescales.
How to cite: Pizzuto, J.: Quantitative Sediment Storage Chronology Associated with European Colonization of the Mid-Atlantic U.S. and its Application to Watershed Scale Sediment Routing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5834, https://doi.org/10.5194/egusphere-egu21-5834, 2021.
EGU21-1703 | vPICO presentations | GM3.17
Downstream grain-size changes using PebbleCounts in the south-central Andes: Relations to channel steepness and SAR observationsBenjamin Purinton and Bodo Bookhagen
Grain-size data are imperative for understanding erosional and fining processes in steep terrain as rivers are the primary conduits for sediment transport. However, collecting hundreds of pebble measurements at multiple channel bed survey sites in steep and dynamic high-mountain river settings remains a challenging roadblock in studying downstream variations in grain-size. Using PebbleCounts (https://github.com/UP-RS-ESP/PebbleCounts), we survey large (~1,000+ m2) channel cross sections and measure thousands of grains per survey to build robust grain-size distributions in the Quebrada del Toro, Northwest Argentina. Because of imagery resolution considerations, we only examine the grain sizes in the ≥ 2.5 cm fraction of the distribution. We gather measurements via a careful counting and validation process to constrain uncertainties, which highlights the dominant over- and under-segmentation errors that occur in PebbleCounts in this challenging geographic setting. Despite uncertainties, we are able to study downstream changes in grain-size percentiles at seven survey sites along a 100-km stretch of the trunk stream, which traverses a steep topographic and environmental gradient. We find that only the upper-most percentiles (≥ 95th) are sensitive, whereas the 50th and 84th percentiles show little downstream variability in this rapidly eroding catchment. In particular, we note a strong relation between increases in these upper percentiles and the along-channel junctions with large, oversteepened tributaries, where extreme channel steepness reaches are > 200 m0.8 (θ=0.4). Furthermore, independent spaceborne synthetic aperture radar (SAR) coherence and amplitude observations show clear relations to mass transfer and channel bed roughness changes, which also relate to the grain-size variability that we find.
How to cite: Purinton, B. and Bookhagen, B.: Downstream grain-size changes using PebbleCounts in the south-central Andes: Relations to channel steepness and SAR observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1703, https://doi.org/10.5194/egusphere-egu21-1703, 2021.
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Grain-size data are imperative for understanding erosional and fining processes in steep terrain as rivers are the primary conduits for sediment transport. However, collecting hundreds of pebble measurements at multiple channel bed survey sites in steep and dynamic high-mountain river settings remains a challenging roadblock in studying downstream variations in grain-size. Using PebbleCounts (https://github.com/UP-RS-ESP/PebbleCounts), we survey large (~1,000+ m2) channel cross sections and measure thousands of grains per survey to build robust grain-size distributions in the Quebrada del Toro, Northwest Argentina. Because of imagery resolution considerations, we only examine the grain sizes in the ≥ 2.5 cm fraction of the distribution. We gather measurements via a careful counting and validation process to constrain uncertainties, which highlights the dominant over- and under-segmentation errors that occur in PebbleCounts in this challenging geographic setting. Despite uncertainties, we are able to study downstream changes in grain-size percentiles at seven survey sites along a 100-km stretch of the trunk stream, which traverses a steep topographic and environmental gradient. We find that only the upper-most percentiles (≥ 95th) are sensitive, whereas the 50th and 84th percentiles show little downstream variability in this rapidly eroding catchment. In particular, we note a strong relation between increases in these upper percentiles and the along-channel junctions with large, oversteepened tributaries, where extreme channel steepness reaches are > 200 m0.8 (θ=0.4). Furthermore, independent spaceborne synthetic aperture radar (SAR) coherence and amplitude observations show clear relations to mass transfer and channel bed roughness changes, which also relate to the grain-size variability that we find.
How to cite: Purinton, B. and Bookhagen, B.: Downstream grain-size changes using PebbleCounts in the south-central Andes: Relations to channel steepness and SAR observations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1703, https://doi.org/10.5194/egusphere-egu21-1703, 2021.
EGU21-12844 | vPICO presentations | GM3.17
Exploring the relationship between organic deposition resulting from marshes and autogenic scales in deltaic stratigraphyJose Silvestre, Kelly Sanks, Sam Zapp, Dutt Ripul, John Shaw, and Kyle Straub
Many deltas contain extensive marshes, typically defined as laterally extensive, low energy settings tied to a narrow elevation window around sea level. Biological activity in marshes results in in-situ organic sediment accumulation that has the potential to be stored in the sedimentary record. However, it is unclear how marshes interact with channels that transport the clastic sediment and typically control autogenic stratigraphic architecture. We present results from a physical experiment designed to explore the coupled evolution of marshes and deltas over geologic timescales. In the experiment, deltaic channels self-organized due to constant input rates of water and clastic sediment that experience constant long-term accommodation production through sea-level rise. A low bulk density kaolinite clay was deposited on the delta-top following rules developed by the ecology community for in-situ organic production. The kaolinite clay serves as a proxy for the in-situ organic sediments in overbank regions. As such, the autogenic processes of the clastic transport system, which influence elevation relative to sea-level, also exert a control on the scales of preserved organic-rich strata. We quantify the fraction of the organic sediment proxy in the fluvio-deltaic deposit to define a transfer function between the accumulation of organic sediment and its preservation beneath the morphodynamically active layer. We also use synthetic stratigraphy and images of the preserved strata to characterize the spatial arrangements of organic strata, and the influence of marshes on the resulting arrangement of channel bodies. Initial findings suggest that the thickest seams are located near the mean shoreline but extend significant distances from this location due to autogenic shoreline transgressions and regressions. Quantifying these trends will inform our understanding of how in-situ organic sediment accumulation influences clastic transport systems and the structure of deltaic stratigraphy.
How to cite: Silvestre, J., Sanks, K., Zapp, S., Ripul, D., Shaw, J., and Straub, K.: Exploring the relationship between organic deposition resulting from marshes and autogenic scales in deltaic stratigraphy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12844, https://doi.org/10.5194/egusphere-egu21-12844, 2021.
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Many deltas contain extensive marshes, typically defined as laterally extensive, low energy settings tied to a narrow elevation window around sea level. Biological activity in marshes results in in-situ organic sediment accumulation that has the potential to be stored in the sedimentary record. However, it is unclear how marshes interact with channels that transport the clastic sediment and typically control autogenic stratigraphic architecture. We present results from a physical experiment designed to explore the coupled evolution of marshes and deltas over geologic timescales. In the experiment, deltaic channels self-organized due to constant input rates of water and clastic sediment that experience constant long-term accommodation production through sea-level rise. A low bulk density kaolinite clay was deposited on the delta-top following rules developed by the ecology community for in-situ organic production. The kaolinite clay serves as a proxy for the in-situ organic sediments in overbank regions. As such, the autogenic processes of the clastic transport system, which influence elevation relative to sea-level, also exert a control on the scales of preserved organic-rich strata. We quantify the fraction of the organic sediment proxy in the fluvio-deltaic deposit to define a transfer function between the accumulation of organic sediment and its preservation beneath the morphodynamically active layer. We also use synthetic stratigraphy and images of the preserved strata to characterize the spatial arrangements of organic strata, and the influence of marshes on the resulting arrangement of channel bodies. Initial findings suggest that the thickest seams are located near the mean shoreline but extend significant distances from this location due to autogenic shoreline transgressions and regressions. Quantifying these trends will inform our understanding of how in-situ organic sediment accumulation influences clastic transport systems and the structure of deltaic stratigraphy.
How to cite: Silvestre, J., Sanks, K., Zapp, S., Ripul, D., Shaw, J., and Straub, K.: Exploring the relationship between organic deposition resulting from marshes and autogenic scales in deltaic stratigraphy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12844, https://doi.org/10.5194/egusphere-egu21-12844, 2021.
EGU21-13122 * | vPICO presentations | GM3.17 | Highlight
Tectonic influence of Large Igneous Provinces on source-to-sink systems, the case study of Shetland during the Palaeocene - Preliminary resultsLucas Albanese Valore, Christian Haug Eide, and Tor Oftedal Sømme
The source-to-sink approach to sedimentology has become an increasingly valuable approach for addressing how external and internal forcing mechanisms are tied together in time and space. Processes that are initiated deep within the lower mantle can eventually propagate and affect shallow crustal sedimentary systems. This is important to predict the presence of reservoirs in areas of little data, and to interpret the sedimentary record in terms of climate and tectonic settings during deposition. To address this issue, we will study the Early Palaeogene succession of the East Shetland Platform in the North Sea, which was deposited during the emplacement of the Icelandic Plume. The plume’s activity is hypothesized to be the cause of a major uplift cycle in the continental source areas, which is coeval to a sharp increase in sedimentation rates recorded in the East Shetland Platform during the Palaeocene. However, this relationship is still in need of accurate constraints derived from data with better spatial and temporal resolution, particularly due to overlapping climatic and tectonic controls, regional-to-local variations in sediment supply systems and overall gaps in the sedimentary record. This correlation can benefit from high-quality 3D seismic data on the platform, especially due to an exceptional preservation of shelf-edge geometries that are absent elsewhere. Using different 3D and 2D seismic surveys, well data and biostratigraphic data from the Shetland Platform and the North Sea, we will quantify sediment volumes supplied through time. The observed sediment volumes will be investigated using models of dynamic topography, plume activity and paleoclimatic data to closely relate supplied volumes to changes in relief, catchment geometries, precipitation and other key forcing parameters. Ultimately, we aim to investigate the relative influence of both tectonics and climate, as both long term (mantle dynamics) and short term (Palaeocene-Eocene Thermal Maximum) have been interpreted to play an important role in this system.
How to cite: Albanese Valore, L., Haug Eide, C., and Oftedal Sømme, T.: Tectonic influence of Large Igneous Provinces on source-to-sink systems, the case study of Shetland during the Palaeocene - Preliminary results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13122, https://doi.org/10.5194/egusphere-egu21-13122, 2021.
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The source-to-sink approach to sedimentology has become an increasingly valuable approach for addressing how external and internal forcing mechanisms are tied together in time and space. Processes that are initiated deep within the lower mantle can eventually propagate and affect shallow crustal sedimentary systems. This is important to predict the presence of reservoirs in areas of little data, and to interpret the sedimentary record in terms of climate and tectonic settings during deposition. To address this issue, we will study the Early Palaeogene succession of the East Shetland Platform in the North Sea, which was deposited during the emplacement of the Icelandic Plume. The plume’s activity is hypothesized to be the cause of a major uplift cycle in the continental source areas, which is coeval to a sharp increase in sedimentation rates recorded in the East Shetland Platform during the Palaeocene. However, this relationship is still in need of accurate constraints derived from data with better spatial and temporal resolution, particularly due to overlapping climatic and tectonic controls, regional-to-local variations in sediment supply systems and overall gaps in the sedimentary record. This correlation can benefit from high-quality 3D seismic data on the platform, especially due to an exceptional preservation of shelf-edge geometries that are absent elsewhere. Using different 3D and 2D seismic surveys, well data and biostratigraphic data from the Shetland Platform and the North Sea, we will quantify sediment volumes supplied through time. The observed sediment volumes will be investigated using models of dynamic topography, plume activity and paleoclimatic data to closely relate supplied volumes to changes in relief, catchment geometries, precipitation and other key forcing parameters. Ultimately, we aim to investigate the relative influence of both tectonics and climate, as both long term (mantle dynamics) and short term (Palaeocene-Eocene Thermal Maximum) have been interpreted to play an important role in this system.
How to cite: Albanese Valore, L., Haug Eide, C., and Oftedal Sømme, T.: Tectonic influence of Large Igneous Provinces on source-to-sink systems, the case study of Shetland during the Palaeocene - Preliminary results, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13122, https://doi.org/10.5194/egusphere-egu21-13122, 2021.
EGU21-12221 | vPICO presentations | GM3.17
Clinoform growth and sediment flux of Late Cenozoic Yinggehai and Qiongdongnan shelf margins, Northern South China SeaSi Chen, Hua Wang, Jianghao Ma, Tianhao Gong, and Zhenghong Yu
This study discusses the sedimentary flux, and sedimentary system source tracking on the shelf margins of Yinggehai (YGH) and Qiongdongnan (QDN) Basins, Northern South China Sea. The shelf margin clinoforms of YGH and QDN Basins, have grown since the Late Cenozoic (10.5 Ma), which generated more than 4 km-thick shelf prism above the T40 surface. By using the core, well drilling data, 2D and 3D seismic surveys, this study aims to: ① demonstrate the geometry morphology and architecture of the clinoforms, while the shelf margin trajectory (including the shelf-edge trajectory and toe of slope trajectory) showing down-flatting and rising patterns where the progradation and aggradation happened through the vertical evolution; ② estimate sediment supply values, load volumes, and their changes since the Late Cenozoic, predict ratio of the sediment flux across shelf-edge during their dynamic processes; ③ investigate the contradiction and correlation among the phenomena that sediments show distinctly increasing in flux, decreasing in grain size, and response delay of flux rate peak since 2-4 Ma. The preliminary results show that the vertical sediment accumulation rate increased significantly across the entire YGH and QDN Basin margin system after 2.4 Ma, with a marked increase in mud content that likely caused by long‐distance, alongshore currents with high content of mud during the Pleistocene. Furthermore, laterally, the estimated total sediment flux onto the margin shows a dramatic decline from west to east while moving away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east of QDN Basin margin. The Late Cenozoic shelf margin growth, with its overall increased sediment flux, responded to global, high‐frequency transgressive‐regressive climate cycles during a falling global sea level and gradual cooling temperature in this icehouse period.
How to cite: Chen, S., Wang, H., Ma, J., Gong, T., and Yu, Z.: Clinoform growth and sediment flux of Late Cenozoic Yinggehai and Qiongdongnan shelf margins, Northern South China Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12221, https://doi.org/10.5194/egusphere-egu21-12221, 2021.
This study discusses the sedimentary flux, and sedimentary system source tracking on the shelf margins of Yinggehai (YGH) and Qiongdongnan (QDN) Basins, Northern South China Sea. The shelf margin clinoforms of YGH and QDN Basins, have grown since the Late Cenozoic (10.5 Ma), which generated more than 4 km-thick shelf prism above the T40 surface. By using the core, well drilling data, 2D and 3D seismic surveys, this study aims to: ① demonstrate the geometry morphology and architecture of the clinoforms, while the shelf margin trajectory (including the shelf-edge trajectory and toe of slope trajectory) showing down-flatting and rising patterns where the progradation and aggradation happened through the vertical evolution; ② estimate sediment supply values, load volumes, and their changes since the Late Cenozoic, predict ratio of the sediment flux across shelf-edge during their dynamic processes; ③ investigate the contradiction and correlation among the phenomena that sediments show distinctly increasing in flux, decreasing in grain size, and response delay of flux rate peak since 2-4 Ma. The preliminary results show that the vertical sediment accumulation rate increased significantly across the entire YGH and QDN Basin margin system after 2.4 Ma, with a marked increase in mud content that likely caused by long‐distance, alongshore currents with high content of mud during the Pleistocene. Furthermore, laterally, the estimated total sediment flux onto the margin shows a dramatic decline from west to east while moving away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east of QDN Basin margin. The Late Cenozoic shelf margin growth, with its overall increased sediment flux, responded to global, high‐frequency transgressive‐regressive climate cycles during a falling global sea level and gradual cooling temperature in this icehouse period.
How to cite: Chen, S., Wang, H., Ma, J., Gong, T., and Yu, Z.: Clinoform growth and sediment flux of Late Cenozoic Yinggehai and Qiongdongnan shelf margins, Northern South China Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12221, https://doi.org/10.5194/egusphere-egu21-12221, 2021.
EGU21-12600 | vPICO presentations | GM3.17
A Source to Sink Approach to the North Sea Fan Pleistocene Glacial SedimentsAurora Machado Garcia, Ivar Midtkandal, Benjamin Bellwald, and Ingrid Margareta Anell
Trough mouth fans are large depocentres forming the ultimate sinks in glacial source-to-sink systems. Their architecture, sedimentological aspects (origin and processes) and their role as paleoclimatic archives are essential components in improving our understanding of Pleistocene and ongoing climate changes. For many years, these depocentres were thought to be dominated by debris flows accumulated in front of ice streams located at the shelf break. However, recent studies have shown that meltwater plays a major role in bringing sediment to the most distal parts of these fans, especially in lower latitudes. The North Sea Trough Mouth Fan encompasses ~110,000 km2 with water depths of up to 3500 m. It has received sediments throughout the Quaternary, with increased sedimentation rates in the last 1.1 Ma when the Norwegian Channel Ice Stream was active. Recent insight of the fan shows that meltwater turbidites play a major role in sediment delivery to the continental slope and deep-sea basin. The results could entail distinct morphologies for mid-latitude and high-latitude fans. As a result of glacial erosion and the absence of clear imprints of ice sheets on the paleo-shelves, studying trough mouth fan deposits becomes paramount in understanding glacial-interglacial cycles. This project will assess the source-to-sink parameters of the last glaciation (Weichselian) at the North Sea Fan, elucidating the dominant marine and terrestrial processes that led to the studied sedimentary sequences. High-resolution 2D and 3D seismic data, core, volumetric and numerical modeling data will be assimilated to establish a source-to-sink model for the target interval. These results will contribute to the knowledge of how glaciations affect surface mass redistribution, directly affecting the landscape dynamics and sediment routing from Fennoscandia via the North Sea to the slopes and deep basin. Sediment production will be evaluated, assessing whether it increases during the glaciation or if observed higher sedimentation rates are a result of enhanced sediment transport. This project is a part of the Marie Sklodowska-Curie Innovative Training Networks “S2S – Future: Signal propagation in source to sink for the future of the Earth resources and energy” and will further advance how trough mouth flans are highly dynamic areas where sediment transport, dispersal, remobilization and deposition take place, and serve as excellent proxies to the dynamics of glacial pulses in the hinterland.
How to cite: Machado Garcia, A., Midtkandal, I., Bellwald, B., and Anell, I. M.: A Source to Sink Approach to the North Sea Fan Pleistocene Glacial Sediments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12600, https://doi.org/10.5194/egusphere-egu21-12600, 2021.
Trough mouth fans are large depocentres forming the ultimate sinks in glacial source-to-sink systems. Their architecture, sedimentological aspects (origin and processes) and their role as paleoclimatic archives are essential components in improving our understanding of Pleistocene and ongoing climate changes. For many years, these depocentres were thought to be dominated by debris flows accumulated in front of ice streams located at the shelf break. However, recent studies have shown that meltwater plays a major role in bringing sediment to the most distal parts of these fans, especially in lower latitudes. The North Sea Trough Mouth Fan encompasses ~110,000 km2 with water depths of up to 3500 m. It has received sediments throughout the Quaternary, with increased sedimentation rates in the last 1.1 Ma when the Norwegian Channel Ice Stream was active. Recent insight of the fan shows that meltwater turbidites play a major role in sediment delivery to the continental slope and deep-sea basin. The results could entail distinct morphologies for mid-latitude and high-latitude fans. As a result of glacial erosion and the absence of clear imprints of ice sheets on the paleo-shelves, studying trough mouth fan deposits becomes paramount in understanding glacial-interglacial cycles. This project will assess the source-to-sink parameters of the last glaciation (Weichselian) at the North Sea Fan, elucidating the dominant marine and terrestrial processes that led to the studied sedimentary sequences. High-resolution 2D and 3D seismic data, core, volumetric and numerical modeling data will be assimilated to establish a source-to-sink model for the target interval. These results will contribute to the knowledge of how glaciations affect surface mass redistribution, directly affecting the landscape dynamics and sediment routing from Fennoscandia via the North Sea to the slopes and deep basin. Sediment production will be evaluated, assessing whether it increases during the glaciation or if observed higher sedimentation rates are a result of enhanced sediment transport. This project is a part of the Marie Sklodowska-Curie Innovative Training Networks “S2S – Future: Signal propagation in source to sink for the future of the Earth resources and energy” and will further advance how trough mouth flans are highly dynamic areas where sediment transport, dispersal, remobilization and deposition take place, and serve as excellent proxies to the dynamics of glacial pulses in the hinterland.
How to cite: Machado Garcia, A., Midtkandal, I., Bellwald, B., and Anell, I. M.: A Source to Sink Approach to the North Sea Fan Pleistocene Glacial Sediments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12600, https://doi.org/10.5194/egusphere-egu21-12600, 2021.
EGU21-12391 | vPICO presentations | GM3.17
Geochemical/isotope characterization of sediments from the Great Indian Desert, TharRohan Bhattacharyya and Satinder Pal Singh
The Great Indian Desert, Thar is a natural source of the atmospheric mineral dust burden over India and nearby landmasses/seas and regulates the regional climate and ecosystem health. However, the limited geochemical/isotope data of Thar sediments from the source region in Rajasthan restrict their source delineation and implication for characterization of the Thar dust signatures. For this purpose, we have measured major, trace, and rare-earth elemental concentrations, and radiogenic Sr and Nd isotope compositions in 51 surface sediment samples collected over a wide area from the Thar Desert, Rajasthan. The geochemical data reveals a low degree of the chemical index of alteration (CIA ~43–54), a quartz dilution of major oxides, and depletion of heavy minerals such as zircons. The UCC normalized spider diagram, as well as La/Yb–Eu anomaly plot, reveal that the Thar surface sediments collected in this study are geochemically similar to that of a sedimentary sequence from the Luni River originating from the Aravalli mountains. The 87Sr/86Sr and εNd of Thar sediments overlap with the reported values for the Indus delta and Luni river sediments but are distinctly different from those of the Ghaggar river sediments. Thus, the sediment contribution from the Indus delta cannot be completely ruled out, while the Ghaggar sediment contributions are minimum. Furthermore, the radiogenic isotope compositions of the decarbonated Thar sediments are strikingly contrasting to the reported values for silicate fractions of eolian deposits in northwestern India. These differences could be due to grain size effects during the dust production/transport or local sediment contributions to the eolian deposits.
How to cite: Bhattacharyya, R. and Singh, S. P.: Geochemical/isotope characterization of sediments from the Great Indian Desert, Thar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12391, https://doi.org/10.5194/egusphere-egu21-12391, 2021.
The Great Indian Desert, Thar is a natural source of the atmospheric mineral dust burden over India and nearby landmasses/seas and regulates the regional climate and ecosystem health. However, the limited geochemical/isotope data of Thar sediments from the source region in Rajasthan restrict their source delineation and implication for characterization of the Thar dust signatures. For this purpose, we have measured major, trace, and rare-earth elemental concentrations, and radiogenic Sr and Nd isotope compositions in 51 surface sediment samples collected over a wide area from the Thar Desert, Rajasthan. The geochemical data reveals a low degree of the chemical index of alteration (CIA ~43–54), a quartz dilution of major oxides, and depletion of heavy minerals such as zircons. The UCC normalized spider diagram, as well as La/Yb–Eu anomaly plot, reveal that the Thar surface sediments collected in this study are geochemically similar to that of a sedimentary sequence from the Luni River originating from the Aravalli mountains. The 87Sr/86Sr and εNd of Thar sediments overlap with the reported values for the Indus delta and Luni river sediments but are distinctly different from those of the Ghaggar river sediments. Thus, the sediment contribution from the Indus delta cannot be completely ruled out, while the Ghaggar sediment contributions are minimum. Furthermore, the radiogenic isotope compositions of the decarbonated Thar sediments are strikingly contrasting to the reported values for silicate fractions of eolian deposits in northwestern India. These differences could be due to grain size effects during the dust production/transport or local sediment contributions to the eolian deposits.
How to cite: Bhattacharyya, R. and Singh, S. P.: Geochemical/isotope characterization of sediments from the Great Indian Desert, Thar, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12391, https://doi.org/10.5194/egusphere-egu21-12391, 2021.
EGU21-1095 | vPICO presentations | GM3.17
Recycling of Sahara desert sand, a comprehensive provenance study approach.Guido Pastore, Thomas Baird, Pieter Vermeesch, Alberto Resentini, and Eduardo Garzanti
The Sahara is by far the largest hot desert on Earth. Its composite structure includes large dune fields hosted in sedimentary basins separated by elevated areas exposing the roots of Precambrian orogens or created by recent intraplate volcanism. Such an heterogeneity of landscapes and geological formations is contrasted by a remarkably homogeneous composition of dune sand, consisting almost everywhere of quartz and durable minerals such as zircon, tourmaline, and rutile.
We here present the first comprehensive provenance study of the Sahara Desert using a combination of multiple provenance proxies such as bulk-petrography, heavy-mineral, and detrital-zircon U–Pb geochronology. A set of statistical tools including Multidimensional Scaling, Correspondence Analysis, Individual Difference Scaling, and General Procrustes Analysis was applied to discriminate among sample groups with the purpose to reveal meaningful compositional patterns and infer sediment transport pathways on a geological scale.
Saharan dune fields are, with a few local exceptions, composed of pure quartz with very poor heavy-mineral suites dominated by durable zircon, tourmaline, and rutile. Some more feldspars, amphibole, epidote, garnet, or staurolite occur closer to basement exposures, and carbonate grains, clinopyroxene and olivine near a basaltic field in Libya. Relatively varied compositions also characterize sand along the Nile Valley and the southern front of the Anti-Atlas fold belt in Morocco. Otherwise, from the Sahel to the Mediterranean Sea and from the Nile River to the Atlantic Ocean, sand consists nearly exclusively of quartz and durable minerals. These have been concentrated through multiple cycles of erosion, deposition, and diagenesis during the long period of relative tectonic quiescence that followed the Neoproterozoic Pan-African orogeny, the last episode of major crustal growth in the region. The principal ultimate source of recycled sand is held to be represented by the thick blanket of quartz-rich sandstones that were deposited in the Cambro-Ordovician from the newly formed Arabian-Nubian Shield in the east to Mauritania in the west.
The composition and homogeneity of Saharan dune sand reflects similar generative processes and source rocks, and extensive recycling repeated through geological time after the end of the Neoproterozoic, which zircon-age spectra indicate as the last major event of crustal growth in the region. The geographic zircon-age distribution in daughter sands thus chiefly reflects the zircon-age distribution in parent sandstones, and hence sediment dispersal systems existing at those times rather than present wind patterns. This leads to the coclusion that, provenance studies based on detrital-zircon ages, the assumption that observed age patterns reflect transport pathways existing at the time of deposition rather than inheritance from even multiple and remote landscapes of the past thus needs to be carefully investigated and convincingly demonstrated rather than implicitly assumed.
How to cite: Pastore, G., Baird, T., Vermeesch, P., Resentini, A., and Garzanti, E.: Recycling of Sahara desert sand, a comprehensive provenance study approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1095, https://doi.org/10.5194/egusphere-egu21-1095, 2021.
The Sahara is by far the largest hot desert on Earth. Its composite structure includes large dune fields hosted in sedimentary basins separated by elevated areas exposing the roots of Precambrian orogens or created by recent intraplate volcanism. Such an heterogeneity of landscapes and geological formations is contrasted by a remarkably homogeneous composition of dune sand, consisting almost everywhere of quartz and durable minerals such as zircon, tourmaline, and rutile.
We here present the first comprehensive provenance study of the Sahara Desert using a combination of multiple provenance proxies such as bulk-petrography, heavy-mineral, and detrital-zircon U–Pb geochronology. A set of statistical tools including Multidimensional Scaling, Correspondence Analysis, Individual Difference Scaling, and General Procrustes Analysis was applied to discriminate among sample groups with the purpose to reveal meaningful compositional patterns and infer sediment transport pathways on a geological scale.
Saharan dune fields are, with a few local exceptions, composed of pure quartz with very poor heavy-mineral suites dominated by durable zircon, tourmaline, and rutile. Some more feldspars, amphibole, epidote, garnet, or staurolite occur closer to basement exposures, and carbonate grains, clinopyroxene and olivine near a basaltic field in Libya. Relatively varied compositions also characterize sand along the Nile Valley and the southern front of the Anti-Atlas fold belt in Morocco. Otherwise, from the Sahel to the Mediterranean Sea and from the Nile River to the Atlantic Ocean, sand consists nearly exclusively of quartz and durable minerals. These have been concentrated through multiple cycles of erosion, deposition, and diagenesis during the long period of relative tectonic quiescence that followed the Neoproterozoic Pan-African orogeny, the last episode of major crustal growth in the region. The principal ultimate source of recycled sand is held to be represented by the thick blanket of quartz-rich sandstones that were deposited in the Cambro-Ordovician from the newly formed Arabian-Nubian Shield in the east to Mauritania in the west.
The composition and homogeneity of Saharan dune sand reflects similar generative processes and source rocks, and extensive recycling repeated through geological time after the end of the Neoproterozoic, which zircon-age spectra indicate as the last major event of crustal growth in the region. The geographic zircon-age distribution in daughter sands thus chiefly reflects the zircon-age distribution in parent sandstones, and hence sediment dispersal systems existing at those times rather than present wind patterns. This leads to the coclusion that, provenance studies based on detrital-zircon ages, the assumption that observed age patterns reflect transport pathways existing at the time of deposition rather than inheritance from even multiple and remote landscapes of the past thus needs to be carefully investigated and convincingly demonstrated rather than implicitly assumed.
How to cite: Pastore, G., Baird, T., Vermeesch, P., Resentini, A., and Garzanti, E.: Recycling of Sahara desert sand, a comprehensive provenance study approach., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1095, https://doi.org/10.5194/egusphere-egu21-1095, 2021.
EGU21-12133 | vPICO presentations | GM3.17
A new way to predict sediment production and deposition: integrated Source to Sink maps at pluri-basins-scaleAlexandre Ortiz, Charlotte Fillon, Eric Lasseur, Justine Briais, Francois Guillocheau, Paul Bessin, Guillaume Baby, Julien Baptiste, Jessica Uzel, Cécile Robin, Sylvain Calassou, Sébastien Catelltort, and Giunluca Frasca
The knowledge acquired on the exhumation of the Pyrenean chain and the evolution of the adjacent foreland basins makes this Alpine-type domain a good laboratory to better constrain a full sediment routing system in a compressive context and to apprehend the driving processes controlling the sediment routing in space and time. This integrated approach aims at enhancing our basin mastering approach as well as improving our predictions of reservoir properties for oil and gas exploration and storage.
This Source-to-Sink study seeks to understand the evolution of sedimentary routing from the Source (orogenic relief, craton, basin recycling) through the transfer zone (peripheral or internal to the basin) to the final sink (flexural basin, deep turbiditic margin). Within the framework of this new cartography, we propose to compile the available and newly acquired data from the S2S project (TOTAL, BRGM), over the entire peri-Pyrenean domain. We produced large scale quantitative and qualitative maps and wheeler diagrams to better observe and interpret the tectonic, climatic and surface processes impacts of the SRS behavior.
The maps include kinematic reconstructions of the Iberian-European-Mediterranean system, restored sequential cross-sections, history/magnitude of exhumation by thermochronology, source tracking, characterization of weathering and erosion surfaces, synthesis of the major structural accidents activity, paleogeographic reconstructions, analysis of sedimentary geometries and transport directions as well as the quantification of volumes preserved in the basins. Their interpretation is combined with a time representation along the routing system, linking classical basin wheeler diagram representation to source erosion and lithologies to obtain a continuous view on the sediment journey.
The time steps chosen for these 5 maps account for the different stages of tectono-sedimentary evolution of the peri-Pyrenean system at the early-orogenic, syn-orogenic and post-orogenic stages. The compilations carried out compare exhumed domains and sedimentation zones in terms of fluxes and volumes and make it possible to map the routing systems and discuss the drivers for the surface evolution during the construction/destruction cycle of an orogen.
Research work financed and carried out as part of the BRGM-TOTAL Source-to-Sink program
How to cite: Ortiz, A., Fillon, C., Lasseur, E., Briais, J., Guillocheau, F., Bessin, P., Baby, G., Baptiste, J., Uzel, J., Robin, C., Calassou, S., Catelltort, S., and Frasca, G.: A new way to predict sediment production and deposition: integrated Source to Sink maps at pluri-basins-scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12133, https://doi.org/10.5194/egusphere-egu21-12133, 2021.
The knowledge acquired on the exhumation of the Pyrenean chain and the evolution of the adjacent foreland basins makes this Alpine-type domain a good laboratory to better constrain a full sediment routing system in a compressive context and to apprehend the driving processes controlling the sediment routing in space and time. This integrated approach aims at enhancing our basin mastering approach as well as improving our predictions of reservoir properties for oil and gas exploration and storage.
This Source-to-Sink study seeks to understand the evolution of sedimentary routing from the Source (orogenic relief, craton, basin recycling) through the transfer zone (peripheral or internal to the basin) to the final sink (flexural basin, deep turbiditic margin). Within the framework of this new cartography, we propose to compile the available and newly acquired data from the S2S project (TOTAL, BRGM), over the entire peri-Pyrenean domain. We produced large scale quantitative and qualitative maps and wheeler diagrams to better observe and interpret the tectonic, climatic and surface processes impacts of the SRS behavior.
The maps include kinematic reconstructions of the Iberian-European-Mediterranean system, restored sequential cross-sections, history/magnitude of exhumation by thermochronology, source tracking, characterization of weathering and erosion surfaces, synthesis of the major structural accidents activity, paleogeographic reconstructions, analysis of sedimentary geometries and transport directions as well as the quantification of volumes preserved in the basins. Their interpretation is combined with a time representation along the routing system, linking classical basin wheeler diagram representation to source erosion and lithologies to obtain a continuous view on the sediment journey.
The time steps chosen for these 5 maps account for the different stages of tectono-sedimentary evolution of the peri-Pyrenean system at the early-orogenic, syn-orogenic and post-orogenic stages. The compilations carried out compare exhumed domains and sedimentation zones in terms of fluxes and volumes and make it possible to map the routing systems and discuss the drivers for the surface evolution during the construction/destruction cycle of an orogen.
Research work financed and carried out as part of the BRGM-TOTAL Source-to-Sink program
How to cite: Ortiz, A., Fillon, C., Lasseur, E., Briais, J., Guillocheau, F., Bessin, P., Baby, G., Baptiste, J., Uzel, J., Robin, C., Calassou, S., Catelltort, S., and Frasca, G.: A new way to predict sediment production and deposition: integrated Source to Sink maps at pluri-basins-scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12133, https://doi.org/10.5194/egusphere-egu21-12133, 2021.
EGU21-2430 | vPICO presentations | GM3.17
Seasonal variations in the origin of river sediments (Baker River, Chile): A pre-requisite for climate and hydrological reconstructionsBenjamin Amann, Sebastien Bertrand, Camila Alvarez Garreton, and Brian Reid
How to cite: Amann, B., Bertrand, S., Alvarez Garreton, C., and Reid, B.: Seasonal variations in the origin of river sediments (Baker River, Chile): A pre-requisite for climate and hydrological reconstructions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2430, https://doi.org/10.5194/egusphere-egu21-2430, 2021.
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How to cite: Amann, B., Bertrand, S., Alvarez Garreton, C., and Reid, B.: Seasonal variations in the origin of river sediments (Baker River, Chile): A pre-requisite for climate and hydrological reconstructions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2430, https://doi.org/10.5194/egusphere-egu21-2430, 2021.
EGU21-9296 | vPICO presentations | GM3.17
Impact of climatic step-changes on source-to-sink systems: Petrographic changes across the Permian-Triassic changes on the Finnmark Platform, Barents Sea, N NorwayMelanie Kling, Hallgeir Sirevaag, Emmanuelle Pucéat, and Christian Haug Eide
The emplacement of the Siberian Traps Large Igneous Province around the Permian–Triassic boundary significantly affected both climate and depositional environments across the world. Known long term consequences of this event are (I) global warming, (II) increased continental weathering, (III) oceanic stagnation and acidification and (IV) mass extinction. These effects have the potential to strongly alter signals from source-to-sink systems in terms of petrography, sediment volumes and geochemistry. The Barents Sea Basin is an excellent area to investigate the response of source-to-sink systems to such climatic changes because it contains a continuous record of sediments deposited before, during and after the Permian-Triassic event, and because this interval is sampled in several exploration wells.
The goal of this project is to investigate how the Triassic climatic changes were expressed in source-to-sink systems, mainly using techniques such as facies analysis, petrograpy, mudstone geochemistry and sediment volumes. Herein we present preliminary results mainly from sandstone petrology. On the Finnmark Plattform, the upper Permian strata of the Røye Formation contains spiculitic mudstones and limestones with sparse sandstones. These are overlain by mudstones, interbedded turbidites and prograding deltas of the Lower Triassic. In order to determine how the signal from the catchment changed to the great climatic changes, it is of high importance to examine changes within provenance and sediment volumes across the P-T boundary.
I wish to give this presentation as a poster
How to cite: Kling, M., Sirevaag, H., Pucéat, E., and Eide, C. H.: Impact of climatic step-changes on source-to-sink systems: Petrographic changes across the Permian-Triassic changes on the Finnmark Platform, Barents Sea, N Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9296, https://doi.org/10.5194/egusphere-egu21-9296, 2021.
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The emplacement of the Siberian Traps Large Igneous Province around the Permian–Triassic boundary significantly affected both climate and depositional environments across the world. Known long term consequences of this event are (I) global warming, (II) increased continental weathering, (III) oceanic stagnation and acidification and (IV) mass extinction. These effects have the potential to strongly alter signals from source-to-sink systems in terms of petrography, sediment volumes and geochemistry. The Barents Sea Basin is an excellent area to investigate the response of source-to-sink systems to such climatic changes because it contains a continuous record of sediments deposited before, during and after the Permian-Triassic event, and because this interval is sampled in several exploration wells.
The goal of this project is to investigate how the Triassic climatic changes were expressed in source-to-sink systems, mainly using techniques such as facies analysis, petrograpy, mudstone geochemistry and sediment volumes. Herein we present preliminary results mainly from sandstone petrology. On the Finnmark Plattform, the upper Permian strata of the Røye Formation contains spiculitic mudstones and limestones with sparse sandstones. These are overlain by mudstones, interbedded turbidites and prograding deltas of the Lower Triassic. In order to determine how the signal from the catchment changed to the great climatic changes, it is of high importance to examine changes within provenance and sediment volumes across the P-T boundary.
I wish to give this presentation as a poster
How to cite: Kling, M., Sirevaag, H., Pucéat, E., and Eide, C. H.: Impact of climatic step-changes on source-to-sink systems: Petrographic changes across the Permian-Triassic changes on the Finnmark Platform, Barents Sea, N Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9296, https://doi.org/10.5194/egusphere-egu21-9296, 2021.
EGU21-15369 | vPICO presentations | GM3.17
Late Quaternary Climate Variability Constrains River Incision and Aggradation in the Spiti Valley, Western HimalayaBodo Bookhagen, Manfred Strecker, Samuel Niedermann, and Rasmus Thiede
The intensity of the Asian summer-monsoon circulation varies over decadal to millennial timescales and impacts surface processes, terrestrial environments, and marine sediment records. The duration and magnitude of this climatic forcing on erosion processes varies, depending on duration and intensity of the climatic events, as well as on the tectonic and geomorphologic preconditioning of the landscape. In this study, we focus on a region in the transition zone between continuous and episodic monsoon impacts: the Spiti River, the largest tributary (12x103 km2 ) to the Sutlej River in the western Himalaya. The river valley is located in the northern lee of the Himalayan orographic barrier in a presently arid environment. The Spiti Valley has received significant precipitation during intensified monsoon periods during the late Pleistocene and Holocene and thus constitutes an ideal location to evaluate effects of episodic moisture transport into an arid, high-relief mountainous region.
Here we present 21 new surface-exposure ages of fluvial-fill terraces combined with previously published data to quantify temporal patterns in river incision and erosion rates. Our data include catchment-wide erosion rates and in-situ cosmogenic nuclide ages derived from 10Be, 26Al, and 21Ne and document that terrace formation (i.e., terrace abandonment) occurred during intensified monsoon phases at ∼100 ka, ∼65 ka, ∼43 ka, and ∼12 ka, although dating uncertainties prevent the calculation of exact correlation between monsoonal strength and terrace formation. We show that incision into Late Pleistocene valley fills that integrate over several cut-and-fill cycles at 105 y are comparable to exhumation rates determined from thermochronology studies averaging over 10^6 y in that area. We argue that the limiting factor for sediment removal and river incision on shorter, millennial timescales is due to large bedrock landslides that impounded the river network and formed transient sedimentary basins lasting for 103 -104 years. We suggest a feedback process between sediment removal and landsliding, where large landsliding predominantly occurs when the transiently-stored valley fills have been carved out, leading to exposed valley bottoms, bedrock erosion, lateral scouring of rivers, and ultimately to the over-steepening of hillslopes. We suggest that Late Quaternary climatic variability is the main forcing factor in filling and evacuating transiently stored sediments in high mountain ranges and thus plays a direct role in controlling bedrock incision.
How to cite: Bookhagen, B., Strecker, M., Niedermann, S., and Thiede, R.: Late Quaternary Climate Variability Constrains River Incision and Aggradation in the Spiti Valley, Western Himalaya, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15369, https://doi.org/10.5194/egusphere-egu21-15369, 2021.
The intensity of the Asian summer-monsoon circulation varies over decadal to millennial timescales and impacts surface processes, terrestrial environments, and marine sediment records. The duration and magnitude of this climatic forcing on erosion processes varies, depending on duration and intensity of the climatic events, as well as on the tectonic and geomorphologic preconditioning of the landscape. In this study, we focus on a region in the transition zone between continuous and episodic monsoon impacts: the Spiti River, the largest tributary (12x103 km2 ) to the Sutlej River in the western Himalaya. The river valley is located in the northern lee of the Himalayan orographic barrier in a presently arid environment. The Spiti Valley has received significant precipitation during intensified monsoon periods during the late Pleistocene and Holocene and thus constitutes an ideal location to evaluate effects of episodic moisture transport into an arid, high-relief mountainous region.
Here we present 21 new surface-exposure ages of fluvial-fill terraces combined with previously published data to quantify temporal patterns in river incision and erosion rates. Our data include catchment-wide erosion rates and in-situ cosmogenic nuclide ages derived from 10Be, 26Al, and 21Ne and document that terrace formation (i.e., terrace abandonment) occurred during intensified monsoon phases at ∼100 ka, ∼65 ka, ∼43 ka, and ∼12 ka, although dating uncertainties prevent the calculation of exact correlation between monsoonal strength and terrace formation. We show that incision into Late Pleistocene valley fills that integrate over several cut-and-fill cycles at 105 y are comparable to exhumation rates determined from thermochronology studies averaging over 10^6 y in that area. We argue that the limiting factor for sediment removal and river incision on shorter, millennial timescales is due to large bedrock landslides that impounded the river network and formed transient sedimentary basins lasting for 103 -104 years. We suggest a feedback process between sediment removal and landsliding, where large landsliding predominantly occurs when the transiently-stored valley fills have been carved out, leading to exposed valley bottoms, bedrock erosion, lateral scouring of rivers, and ultimately to the over-steepening of hillslopes. We suggest that Late Quaternary climatic variability is the main forcing factor in filling and evacuating transiently stored sediments in high mountain ranges and thus plays a direct role in controlling bedrock incision.
How to cite: Bookhagen, B., Strecker, M., Niedermann, S., and Thiede, R.: Late Quaternary Climate Variability Constrains River Incision and Aggradation in the Spiti Valley, Western Himalaya, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15369, https://doi.org/10.5194/egusphere-egu21-15369, 2021.
GM4.13 – Denudation, land cover dynamics and sedimentary source-to-sink fluxes under changing climate and anthropogenic impacts
EGU21-2320 * | vPICO presentations | GM4.13 | Highlight
Denudation, global change and the AnthropoceneAntonio Cendrero, Juan Remondo, and Luis Forte
Changes occurred in denudation/sedimentation processes (understood here as the transfer of solid materials from one place of the earth’s surface to another, by different agents) in the latter part of the Holocene, mainly the last couple of centuries, are examined, trying to estimate rates and assess the role of human and natural agents. Three issues are addressed here, on the basis of some case studies: slope movements and their contribution to denudation and relief evolution; “technological denudation” due to human activities; general evolution of sediment accumulation (consequence of denudation).
Analyses of materials transfer by, and frequency of, slope movements in N Spain have shown the importance of human influence already in Neolithic times, and more so after the Industrial Revolution. Significant increases have been observed since the middle of last century and slope movements seem to be in some cases the main factor of relief evolution.
Human activities related to urban-industrial development, infrastructure and mining activities represent an important “human geomorphic footprint” (expressed as volume of materials displaced or area occupied by new “anthropogeoforms”; yearly total or per capita). If the materials thus moved were evenly distributed over all emerged lands they could be presently equivalent to a >1 mm a-1 (“technological”) denudation. As this is the consequence of growing population, technological and economic development, it will probably intensify with time.
Sedimentation rates directly determined (Pb-210, Cs-137) in a number of estuaries, lakes and reservoirs show in general a clear increase since early 20th century, particularly after its middle. Compilation and analysis of sedimentation rates in a variety of sedimentation environments in different regions of the world, since late 19th century, also show, with almost no exception, a similar trend. Comparison with rainfall evolution does not explain the changes observed. However, indicators of the intensity of human activity, especially GDP (Gross Domestic Product; total, not per capita; strongly related to our capacity to transform land), show a good similarity with sedimentation rates trends. This indicator also shows a close correlation with geomorphic disasters frequency (another manifestation of the general intensification of geomorphic processes).
On the basis of the information gathered and results presented, some tentative conclusions are proposed. It appears that presently humans are, by far, the main denudation agent. Direct and indirect transfer of rock, soil and sediment by human activities could be one order of magnitude greater than by natural agents. The rates of some geomorphic processes seem to have experienced a significant acceleration (about tenfold?) in less than a century, due to land surface transformation rather than to climate change. This “great geomorphic acceleration” represents a part of the “Great Acceleration” occurred after mid-twentieth century. Global geomorphic change (independent of climate change) should thus be considered as one of the characteristics of the Anthropocene, for which the end of World War II would indeed be an appropriate starting date.
How to cite: Cendrero, A., Remondo, J., and Forte, L.: Denudation, global change and the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2320, https://doi.org/10.5194/egusphere-egu21-2320, 2021.
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Changes occurred in denudation/sedimentation processes (understood here as the transfer of solid materials from one place of the earth’s surface to another, by different agents) in the latter part of the Holocene, mainly the last couple of centuries, are examined, trying to estimate rates and assess the role of human and natural agents. Three issues are addressed here, on the basis of some case studies: slope movements and their contribution to denudation and relief evolution; “technological denudation” due to human activities; general evolution of sediment accumulation (consequence of denudation).
Analyses of materials transfer by, and frequency of, slope movements in N Spain have shown the importance of human influence already in Neolithic times, and more so after the Industrial Revolution. Significant increases have been observed since the middle of last century and slope movements seem to be in some cases the main factor of relief evolution.
Human activities related to urban-industrial development, infrastructure and mining activities represent an important “human geomorphic footprint” (expressed as volume of materials displaced or area occupied by new “anthropogeoforms”; yearly total or per capita). If the materials thus moved were evenly distributed over all emerged lands they could be presently equivalent to a >1 mm a-1 (“technological”) denudation. As this is the consequence of growing population, technological and economic development, it will probably intensify with time.
Sedimentation rates directly determined (Pb-210, Cs-137) in a number of estuaries, lakes and reservoirs show in general a clear increase since early 20th century, particularly after its middle. Compilation and analysis of sedimentation rates in a variety of sedimentation environments in different regions of the world, since late 19th century, also show, with almost no exception, a similar trend. Comparison with rainfall evolution does not explain the changes observed. However, indicators of the intensity of human activity, especially GDP (Gross Domestic Product; total, not per capita; strongly related to our capacity to transform land), show a good similarity with sedimentation rates trends. This indicator also shows a close correlation with geomorphic disasters frequency (another manifestation of the general intensification of geomorphic processes).
On the basis of the information gathered and results presented, some tentative conclusions are proposed. It appears that presently humans are, by far, the main denudation agent. Direct and indirect transfer of rock, soil and sediment by human activities could be one order of magnitude greater than by natural agents. The rates of some geomorphic processes seem to have experienced a significant acceleration (about tenfold?) in less than a century, due to land surface transformation rather than to climate change. This “great geomorphic acceleration” represents a part of the “Great Acceleration” occurred after mid-twentieth century. Global geomorphic change (independent of climate change) should thus be considered as one of the characteristics of the Anthropocene, for which the end of World War II would indeed be an appropriate starting date.
How to cite: Cendrero, A., Remondo, J., and Forte, L.: Denudation, global change and the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2320, https://doi.org/10.5194/egusphere-egu21-2320, 2021.
EGU21-13921 | vPICO presentations | GM4.13 | Highlight
A triumvirate of peat landslides: A transdisciplinary approach for a not-so-natural- hazard in Ireland.Mary Bourke, Rob Halpin, Catherine Farrell, Michael Long, and John Connolly
Landslides are traditionally viewed through geomorphological, ecological, geophysical, and hydrological lenses, often taking a multi-disciplinary approach. More recently, there have been calls for a different approach- one that acknowledges the increasing importance of socio-environmental stresses that can also affect slope instability. For Ireland, environmental stresses in peatlands are connected to the utilisation of land as a resource that is linked to commercia development, and indeed, towards supporting financial investment in rural areas by various governments, e.g., peat mining, agricultural grazing, afforestation, and wind farm construction.
Weather conditions in Ireland during the 2020 summer and autumn were unusually dry and warm, followed by intense summer storms and longer duration rainfalls. These antecedent conditions are known to increase susceptibility to landslides, especially in organic (peat) soils. Three slope failures in peat occurred in 2020: one in June in Co. Leitrim and two in November in Co. Kerry and Co. Donegal. Landslide susceptibility ratings for all sites were in the lower range.
We adopt a transdisciplinary approach in a study of these three peat landslides and bring together the disciplinary expertise of engineering, geomorphology, hydrology, ecology and land-use.
These three sites provide an opportunity to better constrain the physical properties of peat for comparison with other ecologically similar sites, an area of research that is still developing. In addition, we focus on understanding the altered drainage (hydrology) and the recovery (through natural revegetation and succession) of these sites.
We call for the assessment of the hazard to more fully include the feedback that exists through the connectivity of landscape systems (e.g., colluvial, fluvial and lacustrine/marine). In addition, we recommend that peat landslides be evaluated over extended timescales, beyond the immediate impacts to capture longer-term (secondary) effects on water and ecology in general as well as human enterprise. An inclusion of an analysis of the historical and modern land-use and management of peatland areas in the uplands of Ireland brings the study towards a fuller appreciation of the factors that increase peatland hazard.
Our transdisciplinary approach ensures that the ‘real’ hazard types and levels are identified, particularly in the context of an increasing population expansion, changes in land use and trends in the climate scenario for Ireland.
How to cite: Bourke, M., Halpin, R., Farrell, C., Long, M., and Connolly, J.: A triumvirate of peat landslides: A transdisciplinary approach for a not-so-natural- hazard in Ireland., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13921, https://doi.org/10.5194/egusphere-egu21-13921, 2021.
Landslides are traditionally viewed through geomorphological, ecological, geophysical, and hydrological lenses, often taking a multi-disciplinary approach. More recently, there have been calls for a different approach- one that acknowledges the increasing importance of socio-environmental stresses that can also affect slope instability. For Ireland, environmental stresses in peatlands are connected to the utilisation of land as a resource that is linked to commercia development, and indeed, towards supporting financial investment in rural areas by various governments, e.g., peat mining, agricultural grazing, afforestation, and wind farm construction.
Weather conditions in Ireland during the 2020 summer and autumn were unusually dry and warm, followed by intense summer storms and longer duration rainfalls. These antecedent conditions are known to increase susceptibility to landslides, especially in organic (peat) soils. Three slope failures in peat occurred in 2020: one in June in Co. Leitrim and two in November in Co. Kerry and Co. Donegal. Landslide susceptibility ratings for all sites were in the lower range.
We adopt a transdisciplinary approach in a study of these three peat landslides and bring together the disciplinary expertise of engineering, geomorphology, hydrology, ecology and land-use.
These three sites provide an opportunity to better constrain the physical properties of peat for comparison with other ecologically similar sites, an area of research that is still developing. In addition, we focus on understanding the altered drainage (hydrology) and the recovery (through natural revegetation and succession) of these sites.
We call for the assessment of the hazard to more fully include the feedback that exists through the connectivity of landscape systems (e.g., colluvial, fluvial and lacustrine/marine). In addition, we recommend that peat landslides be evaluated over extended timescales, beyond the immediate impacts to capture longer-term (secondary) effects on water and ecology in general as well as human enterprise. An inclusion of an analysis of the historical and modern land-use and management of peatland areas in the uplands of Ireland brings the study towards a fuller appreciation of the factors that increase peatland hazard.
Our transdisciplinary approach ensures that the ‘real’ hazard types and levels are identified, particularly in the context of an increasing population expansion, changes in land use and trends in the climate scenario for Ireland.
How to cite: Bourke, M., Halpin, R., Farrell, C., Long, M., and Connolly, J.: A triumvirate of peat landslides: A transdisciplinary approach for a not-so-natural- hazard in Ireland., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13921, https://doi.org/10.5194/egusphere-egu21-13921, 2021.
EGU21-13380 | vPICO presentations | GM4.13
Characteristics, distribution and susceptibility of natural and human-induced landslides in a tropical mountainous region: the Rift flank west of Lake Kivu (DR Congo)Jean-Claude Maki Mateso, Charles Bielders, Elise Monsieurs, Arthur Depicker, Benoît Smets, Théophile Tambala, Luc Bagalwa Mateso, and Olivier Dewitte
Tropical mountainous regions are often identified as landslide hotspots with particularly vulnerable populations. Whereas both natural (e.g., rainfall, lithology) and anthropogenic (e.g., deforestation, mining) factors are expected to be involved in landslide occurrence, the relative importance of such factors remains poorly documented. The objective of this study is to understand the role played by natural and anthropogenic factors in the occurrence of landslides in the Rift Flank west of Lake Kivu in DR Congo. First, we inventoried 2856 landslides of various types using Google Earth imagery, high resolution topographic data, historical aerial photographs from1950’sand intense field surveys. We made a distinction between old and recent deep-seated landslides, shallow landslides and mining-related landslides. The difference in susceptibility patterns and in size distributions between old and recent deep-seated landslides indicates that natural factors contributing to their occurrence were either different or changed over time. The shallow landslides are all recent. The susceptibility analysis shows that their regional pattern is mainly controlled by forest dynamics and the presence of roads. The occurrence of shallow landslides in forest areas, i.e. in natural environments, strongly increases with slope gradient. In areas with similar topographic conditions where deforestation has occurred since the 1950’s, shallow landslides are more frequent, but of smaller size. This size reduction is attributed to the decrease of regolith cohesion due to forest loss, which allows a smaller minimum critical area for landsliding. In areas that were already deforested in 1950’s, shallow landslides are less frequent, larger, and occur on less steep slopes. This suggests a combined role between regolith availability and soil management practices that influence erosion and water infiltration. Landslides associated with mining activities are larger than shallow landslides but smaller than the recent deep-seated instabilities. They are not well predicted by the susceptibility models, showing that they respond to environmental factors that are not present under natural conditions. This research highlights the importance of human activities on the occurrence of landslides and the need to consider this context when studying hillslope instability patterns in regions under anthropic pressure.
Keywords: landslide processes, multi-temporal inventory, historical deforestation, mining and quarrying, susceptibility assessment, Africa
How to cite: Maki Mateso, J.-C., Bielders, C., Monsieurs, E., Depicker, A., Smets, B., Tambala, T., Bagalwa Mateso, L., and Dewitte, O.: Characteristics, distribution and susceptibility of natural and human-induced landslides in a tropical mountainous region: the Rift flank west of Lake Kivu (DR Congo), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13380, https://doi.org/10.5194/egusphere-egu21-13380, 2021.
Tropical mountainous regions are often identified as landslide hotspots with particularly vulnerable populations. Whereas both natural (e.g., rainfall, lithology) and anthropogenic (e.g., deforestation, mining) factors are expected to be involved in landslide occurrence, the relative importance of such factors remains poorly documented. The objective of this study is to understand the role played by natural and anthropogenic factors in the occurrence of landslides in the Rift Flank west of Lake Kivu in DR Congo. First, we inventoried 2856 landslides of various types using Google Earth imagery, high resolution topographic data, historical aerial photographs from1950’sand intense field surveys. We made a distinction between old and recent deep-seated landslides, shallow landslides and mining-related landslides. The difference in susceptibility patterns and in size distributions between old and recent deep-seated landslides indicates that natural factors contributing to their occurrence were either different or changed over time. The shallow landslides are all recent. The susceptibility analysis shows that their regional pattern is mainly controlled by forest dynamics and the presence of roads. The occurrence of shallow landslides in forest areas, i.e. in natural environments, strongly increases with slope gradient. In areas with similar topographic conditions where deforestation has occurred since the 1950’s, shallow landslides are more frequent, but of smaller size. This size reduction is attributed to the decrease of regolith cohesion due to forest loss, which allows a smaller minimum critical area for landsliding. In areas that were already deforested in 1950’s, shallow landslides are less frequent, larger, and occur on less steep slopes. This suggests a combined role between regolith availability and soil management practices that influence erosion and water infiltration. Landslides associated with mining activities are larger than shallow landslides but smaller than the recent deep-seated instabilities. They are not well predicted by the susceptibility models, showing that they respond to environmental factors that are not present under natural conditions. This research highlights the importance of human activities on the occurrence of landslides and the need to consider this context when studying hillslope instability patterns in regions under anthropic pressure.
Keywords: landslide processes, multi-temporal inventory, historical deforestation, mining and quarrying, susceptibility assessment, Africa
How to cite: Maki Mateso, J.-C., Bielders, C., Monsieurs, E., Depicker, A., Smets, B., Tambala, T., Bagalwa Mateso, L., and Dewitte, O.: Characteristics, distribution and susceptibility of natural and human-induced landslides in a tropical mountainous region: the Rift flank west of Lake Kivu (DR Congo), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13380, https://doi.org/10.5194/egusphere-egu21-13380, 2021.
EGU21-10551 | vPICO presentations | GM4.13
Does Vegetation Really Affect Earthquake-Induced Landslides? Preliminary Analysis of Worldwide DatabaseRasis Putra Ritonga, Takashi Gomi, Roy C. Sidle, Kenta Koyanagi, Yohei Arata, and Rozaqqa Noviandi
Vegetation is one of key factors controlling landslide occurrence, including frequency, size, and depth. Both horizontal and vertical root networks have important roles in stabilizing hillslopes. For instance, landslide density can be moderated by dense and deep tree root reinforcement below the potential soil slip surfaces. Landslide size can be reduced by extended dense and thick tree root networks, providing cohesive and lateral hillslope reinforcement. Vegetation conditions such as density and composition also alter the landslide occurrence because they are linked to root network density and strength, which are affected by different biogeoclimatic conditions. These findings regarding landslide-vegetation interactions were mostly based on rainfall-induced landslide cases. Preliminary, but yet to be confirmed, findings in Eastern Iburi Earthquake-Induced Landslides (EIL) showed that lateral root reinforcement might moderate the size of landslide scars in forested areas compared to logged areas. Therefore, our primary objective was to examine the effect of different vegetation composition on EIL based on global data and supplemental analysis.
Our global database of EIL was compiled for a 20-yr period using a literature review and GIS analysis. Documented landslides were restricted to shallow mass movements with depths approximately less than 3 m. For vegetation-related analysis, we used Net Primary Production (NPP) and Leaf Area Index (LAI) derived from MODIS-Terra satellite images. Twenty-seven EIL cases were recorded in our database occurring from 2002 to 2018. Among these, 26% of the total cases occurred in Japan, followed by 18% for both in China and New Zealand. Based on climate types, 22% of total EIL cases occurred in temperate oceanic climate (Cfb) dominated by New Zealand EIL cases, and 15% cases occurred in humid subtropical climate region (Cfa), such as Japan. Moreover, 7% cases occurred in tropical rainforests (Af) and 7% cases in hot desserts climate regions (BWh). Among the 27 recorded cases of EIL, we selected eight EIL cases based on biomass classes, which are low (0-2 gC/m2/day), moderate (3-5 gC/m2/day), and high (>5 gC/m2/day). A power-law cumulative-area distribution of landslide areas showed that low biomass sites had the largest landslides (11,000 m2), followed by moderate biomass (3000 m2), and high biomass (200-3000 m2) with the smallest landslides, possibly associated with the density of vegetation. In low biomass regions, the average LAI was 1.8 m2/m2, which was three times lower compared to regions with higher biomass. This indicates that in regions with sparse vegetation, slope reinforcement by dense lateral root networks was minimal. Future research is focusing on compiling information on landslide scars and root depth to assess the effects of vegetation density and vertical root reinforcement on landslide characteristics in each biomass class.
How to cite: Ritonga, R. P., Gomi, T., Sidle, R. C., Koyanagi, K., Arata, Y., and Noviandi, R.: Does Vegetation Really Affect Earthquake-Induced Landslides? Preliminary Analysis of Worldwide Database, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10551, https://doi.org/10.5194/egusphere-egu21-10551, 2021.
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You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Vegetation is one of key factors controlling landslide occurrence, including frequency, size, and depth. Both horizontal and vertical root networks have important roles in stabilizing hillslopes. For instance, landslide density can be moderated by dense and deep tree root reinforcement below the potential soil slip surfaces. Landslide size can be reduced by extended dense and thick tree root networks, providing cohesive and lateral hillslope reinforcement. Vegetation conditions such as density and composition also alter the landslide occurrence because they are linked to root network density and strength, which are affected by different biogeoclimatic conditions. These findings regarding landslide-vegetation interactions were mostly based on rainfall-induced landslide cases. Preliminary, but yet to be confirmed, findings in Eastern Iburi Earthquake-Induced Landslides (EIL) showed that lateral root reinforcement might moderate the size of landslide scars in forested areas compared to logged areas. Therefore, our primary objective was to examine the effect of different vegetation composition on EIL based on global data and supplemental analysis.
Our global database of EIL was compiled for a 20-yr period using a literature review and GIS analysis. Documented landslides were restricted to shallow mass movements with depths approximately less than 3 m. For vegetation-related analysis, we used Net Primary Production (NPP) and Leaf Area Index (LAI) derived from MODIS-Terra satellite images. Twenty-seven EIL cases were recorded in our database occurring from 2002 to 2018. Among these, 26% of the total cases occurred in Japan, followed by 18% for both in China and New Zealand. Based on climate types, 22% of total EIL cases occurred in temperate oceanic climate (Cfb) dominated by New Zealand EIL cases, and 15% cases occurred in humid subtropical climate region (Cfa), such as Japan. Moreover, 7% cases occurred in tropical rainforests (Af) and 7% cases in hot desserts climate regions (BWh). Among the 27 recorded cases of EIL, we selected eight EIL cases based on biomass classes, which are low (0-2 gC/m2/day), moderate (3-5 gC/m2/day), and high (>5 gC/m2/day). A power-law cumulative-area distribution of landslide areas showed that low biomass sites had the largest landslides (11,000 m2), followed by moderate biomass (3000 m2), and high biomass (200-3000 m2) with the smallest landslides, possibly associated with the density of vegetation. In low biomass regions, the average LAI was 1.8 m2/m2, which was three times lower compared to regions with higher biomass. This indicates that in regions with sparse vegetation, slope reinforcement by dense lateral root networks was minimal. Future research is focusing on compiling information on landslide scars and root depth to assess the effects of vegetation density and vertical root reinforcement on landslide characteristics in each biomass class.
How to cite: Ritonga, R. P., Gomi, T., Sidle, R. C., Koyanagi, K., Arata, Y., and Noviandi, R.: Does Vegetation Really Affect Earthquake-Induced Landslides? Preliminary Analysis of Worldwide Database, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10551, https://doi.org/10.5194/egusphere-egu21-10551, 2021.
EGU21-1564 | vPICO presentations | GM4.13
Multi-staged development of landslide slope after extreme hydro-meteorological event in 1997 (Beskid Wyspowy Mts, Polish Flysch Carpathians)Joanna Caputa, Zuzanna Babicka, and Elżbieta Gorczyca
The study is focused on a multi-staged development of slopes affected by landslides in Beskid Wyspowy Mountains, Polish Flysch Carpathians. The role of extreme 1997 hydro-meteorological event as well as successive events in years 1998-2017 in landslide triggering was particularly taken into account.
The flysch Carpathians are characterized by large percentage of an area affected by landslides. Landslides occupy 30-70% of slopes in this area. Meanwhile, this region has high population density (approx. 130 people per km2), which combined with low inclination of slopes encourages people for settlement and agricultural land-use on slopes, including landslide slopes.
Development of slopes in flysch Carpathians is currently progressing mainly during extreme hydro-meteorological events. One of the most significant events took place in 1997 and it was unique one in terms of both the rainfall total and its intensity. After this event approximately 20,000 landslides were created or reactivated in the Polish Carpathians.
Six slope sections ranging from the foot to the top of the ridge were selected for the research. All these sections were transformed by landslides during the 1997 event. They are all located in the Beskid Wyspowy Mts., which is one of the regions most affected by landslides in Polish Flysch Carpathians in 1997.
The degree of activation of landslide slopes in 1997 and thereafter was defined based on field research and the analysis of DTM and orthophotomaps. A number of parameters of the relief of activated landslides were analyzed in detail, including: their slope, network of drainage. Later these parameters were compared to the relief parameters in inactivated parts of landslides.
In one of the studied slope sections no landslides older than 1997 were detected. In other studied slope sections older landslides were present, covering up to 65% of the section’s area. The rejuvenation of landslides covered from 8 to 26% of the area of landslides existing before 1997. Main landslide activity was the formation of numerous secondary scarps, fissures and a fresh accumulation zones of colluvia. Most of landslides that occurred in 1997 occurred within the older landslide forms. As a result, the total area of the slopes affected by landslides increased by only 1.0-1.7% of the studied slopes’ area.
The further development of the landslide slopes in the period 1997-2017 was investigated. Precipitation events occurring during that period, especially in 1998, 2001, 2010 2014, were analyzed in terms of their efficiency in transformation of the studied landslides. The changes in land use in activated parts of landslides were also analyzed. It was found that there was a significant increase in forest cover of 13-52% in activated parts of the landslides in 2017 compared to 1997. An increase in the diversity of the relief of landslide slopes and a greater mosaic of land use, especially a decrease in agricultural land for the benefit of the forest were found.
How to cite: Caputa, J., Babicka, Z., and Gorczyca, E.: Multi-staged development of landslide slope after extreme hydro-meteorological event in 1997 (Beskid Wyspowy Mts, Polish Flysch Carpathians) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1564, https://doi.org/10.5194/egusphere-egu21-1564, 2021.
The study is focused on a multi-staged development of slopes affected by landslides in Beskid Wyspowy Mountains, Polish Flysch Carpathians. The role of extreme 1997 hydro-meteorological event as well as successive events in years 1998-2017 in landslide triggering was particularly taken into account.
The flysch Carpathians are characterized by large percentage of an area affected by landslides. Landslides occupy 30-70% of slopes in this area. Meanwhile, this region has high population density (approx. 130 people per km2), which combined with low inclination of slopes encourages people for settlement and agricultural land-use on slopes, including landslide slopes.
Development of slopes in flysch Carpathians is currently progressing mainly during extreme hydro-meteorological events. One of the most significant events took place in 1997 and it was unique one in terms of both the rainfall total and its intensity. After this event approximately 20,000 landslides were created or reactivated in the Polish Carpathians.
Six slope sections ranging from the foot to the top of the ridge were selected for the research. All these sections were transformed by landslides during the 1997 event. They are all located in the Beskid Wyspowy Mts., which is one of the regions most affected by landslides in Polish Flysch Carpathians in 1997.
The degree of activation of landslide slopes in 1997 and thereafter was defined based on field research and the analysis of DTM and orthophotomaps. A number of parameters of the relief of activated landslides were analyzed in detail, including: their slope, network of drainage. Later these parameters were compared to the relief parameters in inactivated parts of landslides.
In one of the studied slope sections no landslides older than 1997 were detected. In other studied slope sections older landslides were present, covering up to 65% of the section’s area. The rejuvenation of landslides covered from 8 to 26% of the area of landslides existing before 1997. Main landslide activity was the formation of numerous secondary scarps, fissures and a fresh accumulation zones of colluvia. Most of landslides that occurred in 1997 occurred within the older landslide forms. As a result, the total area of the slopes affected by landslides increased by only 1.0-1.7% of the studied slopes’ area.
The further development of the landslide slopes in the period 1997-2017 was investigated. Precipitation events occurring during that period, especially in 1998, 2001, 2010 2014, were analyzed in terms of their efficiency in transformation of the studied landslides. The changes in land use in activated parts of landslides were also analyzed. It was found that there was a significant increase in forest cover of 13-52% in activated parts of the landslides in 2017 compared to 1997. An increase in the diversity of the relief of landslide slopes and a greater mosaic of land use, especially a decrease in agricultural land for the benefit of the forest were found.
How to cite: Caputa, J., Babicka, Z., and Gorczyca, E.: Multi-staged development of landslide slope after extreme hydro-meteorological event in 1997 (Beskid Wyspowy Mts, Polish Flysch Carpathians) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1564, https://doi.org/10.5194/egusphere-egu21-1564, 2021.
EGU21-756 | vPICO presentations | GM4.13
Inferring the effect of individual trees on slope stability in New Zealand’s pastoral hill countryRaphael Spiekermann, Sam McColl, Ian Fuller, John Dymond, Lucy Burkitt, and Hugh Smith
Silvopastoralism in New Zealand’s highly erodible hill country is an important form of erosion and sediment control. Despite a long history in improving sustainable land management and soil conservation since the enactment of the Soil Conservation and Rivers Control Act 1941, there has been little quantitative work to establish the effectiveness of space-planted trees in reducing shallow landslide erosion at farm to landscape scales. This is largely due to the lack of spatially explicit data on individual trees and their influence on slope stability. Therefore, it is difficult to determine the extent to which plantings have targeted slopes susceptible to landslide erosion. Furthermore, root data collection for multiple species and age classes is very time-consuming and costly, which limits the development of root reinforcement models for different species and partly explains the paucity of quantitative data on the effectiveness of space-planted trees.
We present an empirical approach that aims to fill the gap in scale between 1) physical models that integrated root reinforcement data of individual trees into slope stability models and 2) landslide susceptibility modelling at regional scale using land cover data. First, we delineate individual tree crowns (ITCs) at landscape scale and classify into dominant species classes found in New Zealand’s pastoral hill country. The resulting rural tree species classification achieved an overall accuracy of 92.6% based on 9,200 samples that were collected from two farms within the study area. We then present a spatially explicit tree influence model for each species class developed by means of inductive inference. The tree influence models represent the combined hydrological and mechanical influence of trees on slopes, which is inferred through the spatial relationship between individual trees and landslide erosion. The resulting tree influence models largely agree with the shape and distribution of existing physical root reinforcement models.
Of exotic species that were planted for erosion and sediment control, poplars (Populus spp.) and willows (Salix spp.) make up 51% (109,000 trees) in pastoral hill country at a mean density of 3.2 trees/ha. This large number of poplars and willows reflects the efforts made by landowners and soil conservators over several decades to mitigate erosion processes and adopt more sustainable land management practices. In line with previous studies, poplars and willows have the greatest contribution to slope stability with an average maximum effective distance of 20 m. Yet, native kānuka (Kunzea spp.) is the most abundant woody vegetation species in pastoral hill country within the study area, with an average of 24.1 stems per ha (sph), providing an important soil conservation function. A large proportion (56% or 212.5 km2) of pastoral hill-country in the study area remains untreated, i.e. has no added soil shear strength due to the presence of trees. The tree influence models presented in this study can be integrated into landslide susceptibility modelling in silvopastoral/agroforestry landscapes to both quantify the reduction in landslide susceptibility achieved and support targeted erosion and sediment mitigation plans.
How to cite: Spiekermann, R., McColl, S., Fuller, I., Dymond, J., Burkitt, L., and Smith, H.: Inferring the effect of individual trees on slope stability in New Zealand’s pastoral hill country, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-756, https://doi.org/10.5194/egusphere-egu21-756, 2021.
Silvopastoralism in New Zealand’s highly erodible hill country is an important form of erosion and sediment control. Despite a long history in improving sustainable land management and soil conservation since the enactment of the Soil Conservation and Rivers Control Act 1941, there has been little quantitative work to establish the effectiveness of space-planted trees in reducing shallow landslide erosion at farm to landscape scales. This is largely due to the lack of spatially explicit data on individual trees and their influence on slope stability. Therefore, it is difficult to determine the extent to which plantings have targeted slopes susceptible to landslide erosion. Furthermore, root data collection for multiple species and age classes is very time-consuming and costly, which limits the development of root reinforcement models for different species and partly explains the paucity of quantitative data on the effectiveness of space-planted trees.
We present an empirical approach that aims to fill the gap in scale between 1) physical models that integrated root reinforcement data of individual trees into slope stability models and 2) landslide susceptibility modelling at regional scale using land cover data. First, we delineate individual tree crowns (ITCs) at landscape scale and classify into dominant species classes found in New Zealand’s pastoral hill country. The resulting rural tree species classification achieved an overall accuracy of 92.6% based on 9,200 samples that were collected from two farms within the study area. We then present a spatially explicit tree influence model for each species class developed by means of inductive inference. The tree influence models represent the combined hydrological and mechanical influence of trees on slopes, which is inferred through the spatial relationship between individual trees and landslide erosion. The resulting tree influence models largely agree with the shape and distribution of existing physical root reinforcement models.
Of exotic species that were planted for erosion and sediment control, poplars (Populus spp.) and willows (Salix spp.) make up 51% (109,000 trees) in pastoral hill country at a mean density of 3.2 trees/ha. This large number of poplars and willows reflects the efforts made by landowners and soil conservators over several decades to mitigate erosion processes and adopt more sustainable land management practices. In line with previous studies, poplars and willows have the greatest contribution to slope stability with an average maximum effective distance of 20 m. Yet, native kānuka (Kunzea spp.) is the most abundant woody vegetation species in pastoral hill country within the study area, with an average of 24.1 stems per ha (sph), providing an important soil conservation function. A large proportion (56% or 212.5 km2) of pastoral hill-country in the study area remains untreated, i.e. has no added soil shear strength due to the presence of trees. The tree influence models presented in this study can be integrated into landslide susceptibility modelling in silvopastoral/agroforestry landscapes to both quantify the reduction in landslide susceptibility achieved and support targeted erosion and sediment mitigation plans.
How to cite: Spiekermann, R., McColl, S., Fuller, I., Dymond, J., Burkitt, L., and Smith, H.: Inferring the effect of individual trees on slope stability in New Zealand’s pastoral hill country, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-756, https://doi.org/10.5194/egusphere-egu21-756, 2021.
EGU21-12624 | vPICO presentations | GM4.13
Dendrogeomorphic reconstruction of debris-flow activity in Mazeri Valley, Greater Caucasus, GeorgiaOlimpiu Pop, Daniel Germain, Ionela-Georgiana Gavrilǎ, and Mariam Elizbarashvili
The Mazeri Valley in the Greater Caucasus (Georgia) is characterized by a highly dynamic landscape with several active mass-wasting processes. The spatial and temporal dynamics of these geomorphic processes have, over time, resulted in the formation of large cones and fans. In this context, the coupling between the hillslope and the channel plays a fundamental role in controlling the catchment sediment dynamics. The sediment produced at higher altitudes on hillslopes may occasionally reach the debris-flow channel network, and downstream propagation may have significant effects on the fluvial environment and create potential hazards for the resident population, tourists and infrastructures. In this study, we aim to better understand sediment fluxes in the mountain headwater stream in the Mazeri Valley. In this regard, a tree-ring-based chronology of the debris-flow activity on a large cone was created, to shed light on sediment connectivity and better understand the coupling between the main debris-flow channel and the bedload of Dolra river. The 161 disturbed trees sampled allowed to reconstruct a minimum of 12 significant debris-flow events over the last 65 years, with all of these events involving possible sediment input into the stream system of the Dolra river. These successional events, with a return interval of 5.4 years, have partially destabilized the fluvial system and locally induced a switch in the channel style to a braided channel. Although the cone studied is not directly located in a proglacial environment, its geomorphological dynamics remain highly dependent on water and sediment inputs from upstream, giving the presence of retreating glaciers and then paraglacial conditions at high altitude. The ongoing glacial retreat and increased climate variability will certainly lead to a massive output of sediments at high altitude, favoring an increase in geomorphic activity in the area. Many other fan and cone complexes are present in the Mazeri Valley, as well as in other adjacent valleys, and there are no documentations regarding their dynamics (e.g., typology, nature and source areas of hillslope processes, their coupling with channelized sediment-water flows, frequency–magnitude relationships). In this regard, we expect that the present pioneering study in this area will encourage more researches to investigate sediment fluxes for a better land use and preservation of water in Georgia under climate change.
Cette étude représente une contribution pour le projet « Impact du changement climatique sur les glaciers et les risques associés dans le Caucase Géorgien - IMPCLIM », financé par l’Agence Universitaire de la Francophonie (AUF) et le Ministère pour la Recherche et l'Innovation de Roumanie (MRI) à travers l'Institut Roumain de Physique Atomique (IFA).
How to cite: Pop, O., Germain, D., Gavrilǎ, I.-G., and Elizbarashvili, M.: Dendrogeomorphic reconstruction of debris-flow activity in Mazeri Valley, Greater Caucasus, Georgia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12624, https://doi.org/10.5194/egusphere-egu21-12624, 2021.
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The Mazeri Valley in the Greater Caucasus (Georgia) is characterized by a highly dynamic landscape with several active mass-wasting processes. The spatial and temporal dynamics of these geomorphic processes have, over time, resulted in the formation of large cones and fans. In this context, the coupling between the hillslope and the channel plays a fundamental role in controlling the catchment sediment dynamics. The sediment produced at higher altitudes on hillslopes may occasionally reach the debris-flow channel network, and downstream propagation may have significant effects on the fluvial environment and create potential hazards for the resident population, tourists and infrastructures. In this study, we aim to better understand sediment fluxes in the mountain headwater stream in the Mazeri Valley. In this regard, a tree-ring-based chronology of the debris-flow activity on a large cone was created, to shed light on sediment connectivity and better understand the coupling between the main debris-flow channel and the bedload of Dolra river. The 161 disturbed trees sampled allowed to reconstruct a minimum of 12 significant debris-flow events over the last 65 years, with all of these events involving possible sediment input into the stream system of the Dolra river. These successional events, with a return interval of 5.4 years, have partially destabilized the fluvial system and locally induced a switch in the channel style to a braided channel. Although the cone studied is not directly located in a proglacial environment, its geomorphological dynamics remain highly dependent on water and sediment inputs from upstream, giving the presence of retreating glaciers and then paraglacial conditions at high altitude. The ongoing glacial retreat and increased climate variability will certainly lead to a massive output of sediments at high altitude, favoring an increase in geomorphic activity in the area. Many other fan and cone complexes are present in the Mazeri Valley, as well as in other adjacent valleys, and there are no documentations regarding their dynamics (e.g., typology, nature and source areas of hillslope processes, their coupling with channelized sediment-water flows, frequency–magnitude relationships). In this regard, we expect that the present pioneering study in this area will encourage more researches to investigate sediment fluxes for a better land use and preservation of water in Georgia under climate change.
Cette étude représente une contribution pour le projet « Impact du changement climatique sur les glaciers et les risques associés dans le Caucase Géorgien - IMPCLIM », financé par l’Agence Universitaire de la Francophonie (AUF) et le Ministère pour la Recherche et l'Innovation de Roumanie (MRI) à travers l'Institut Roumain de Physique Atomique (IFA).
How to cite: Pop, O., Germain, D., Gavrilǎ, I.-G., and Elizbarashvili, M.: Dendrogeomorphic reconstruction of debris-flow activity in Mazeri Valley, Greater Caucasus, Georgia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12624, https://doi.org/10.5194/egusphere-egu21-12624, 2021.
EGU21-11015 | vPICO presentations | GM4.13 | Highlight
Road Construction and Rainfall as Landslide Triggers in the Rio Lucma Catchment, Eastern Cordillera Blanca, PeruLorena Abad, Daniel Hölbling, and Adam Emmer
Extensive road construction works were recently undertaken in the remote eastern part of the Peruvian Cordillera Blanca, aiming at better connecting isolated mountain communities with regional administrative centres. In the Río Lucma catchment, approximately 47 km of roads were constructed between 2015 and 2018, triggering several landslides that affected an approximate area of 32 ha. We identified and characterised these landslides by combining field mapping, visual interpretation and semi-automated analysis of satellite imagery (PlanetScope and RapidEye-2), and analysis of rainfall data from two stations of the Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI). We investigated in detail three specific areas of interest, where we identified, delineated, and described 56 landslides. We classified the landslides in relation to their position to the road as: landslides downslope the roads (48.2%), complex landslides crossing the roads (46.4 %), and landslides onto the road (5.3%). According to the type of movement, we found that the slide-type movement (60.7%) prevails over the flow-type movement (39.3%). Timewise, we found that 75% of landslides were observed on satellite imagery simultaneously with road construction work, while the remaining 25% were identified between one week and seven months after the roads had been constructed. We analysed lagged cumulative rainfall data against the occurrence of these subsequent landslides, determining that a two-week rainfall accumulation can act as triggering factor of landslides after road construction work. In general, 51% of the landslides were observed during the wet season (November to April) while 41.1% occurred during El Niño–Southern Oscillation (ENSO) strong cool phase or “La Niña” period. We observed that the majority of mapped landslides were directly (e.g., landslides resulting from slope undercutting) or indirectly associated with road constructions (e.g., rainfall-induced landslides resulting from a combination of extreme precipitation over slopes with decreased stability) and that the road constructions also may set preconditions for subsequent rainfall-triggered landslides.
How to cite: Abad, L., Hölbling, D., and Emmer, A.: Road Construction and Rainfall as Landslide Triggers in the Rio Lucma Catchment, Eastern Cordillera Blanca, Peru, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11015, https://doi.org/10.5194/egusphere-egu21-11015, 2021.
Extensive road construction works were recently undertaken in the remote eastern part of the Peruvian Cordillera Blanca, aiming at better connecting isolated mountain communities with regional administrative centres. In the Río Lucma catchment, approximately 47 km of roads were constructed between 2015 and 2018, triggering several landslides that affected an approximate area of 32 ha. We identified and characterised these landslides by combining field mapping, visual interpretation and semi-automated analysis of satellite imagery (PlanetScope and RapidEye-2), and analysis of rainfall data from two stations of the Servicio Nacional de Meteorología e Hidrología del Perú (SENAMHI). We investigated in detail three specific areas of interest, where we identified, delineated, and described 56 landslides. We classified the landslides in relation to their position to the road as: landslides downslope the roads (48.2%), complex landslides crossing the roads (46.4 %), and landslides onto the road (5.3%). According to the type of movement, we found that the slide-type movement (60.7%) prevails over the flow-type movement (39.3%). Timewise, we found that 75% of landslides were observed on satellite imagery simultaneously with road construction work, while the remaining 25% were identified between one week and seven months after the roads had been constructed. We analysed lagged cumulative rainfall data against the occurrence of these subsequent landslides, determining that a two-week rainfall accumulation can act as triggering factor of landslides after road construction work. In general, 51% of the landslides were observed during the wet season (November to April) while 41.1% occurred during El Niño–Southern Oscillation (ENSO) strong cool phase or “La Niña” period. We observed that the majority of mapped landslides were directly (e.g., landslides resulting from slope undercutting) or indirectly associated with road constructions (e.g., rainfall-induced landslides resulting from a combination of extreme precipitation over slopes with decreased stability) and that the road constructions also may set preconditions for subsequent rainfall-triggered landslides.
How to cite: Abad, L., Hölbling, D., and Emmer, A.: Road Construction and Rainfall as Landslide Triggers in the Rio Lucma Catchment, Eastern Cordillera Blanca, Peru, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11015, https://doi.org/10.5194/egusphere-egu21-11015, 2021.
EGU21-118 | vPICO presentations | GM4.13
Does the trail matters? - In search of the environmental impact of hiking trails on the hillslope runoff.Piotr Kopyść
Background: In the late 20th century great advancement was made in the field of hiking trail studies. The main concerns for these trails are susceptibility to soil erosion and dynamic landform changes in their nearest area. The impacts of the trails for vegetation were also studied with trampling and soil exposure being the most destructive. Today, With the higher and higher resolution for digital terrain models being available and advanced simulation algorithms and computing, it is possible to perform advanced modeling of a hillslope runoff.
The aim: The aim of these studies is to determine the impact of hiking trails on hillslope water runoff by comparison of the water discharge values during simulated precipitation events.
Method: The comparison is made possible, with the use of digital terrain modeling to create hillslope with and without a hiking trail, in its pre-erosion state. Both models then are subject to Simulated Water Erosion (SiMWE) based on the Monte Carlo simulation method. The algorithm is implemented in an open-source GRASS GIS program in the form of r.sim.water and r.sim.sediment modules. Exemplary hillslopes also present different scenarios based on the trail to slope alignment angle (0° - 22°; 22,1° - 45°; 45,1° - 67° and 67,1° - 90°).
During the session a case study area of a suburban mountain range within Kielce city (Poland) will be introduced, together with the results of simulation values and their spatial distribution for the exemplary hillslopes. With it, the role of the hiking trail and its environmental impact on water runoff will be better understood and easier to predict.
How to cite: Kopyść, P.: Does the trail matters? - In search of the environmental impact of hiking trails on the hillslope runoff., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-118, https://doi.org/10.5194/egusphere-egu21-118, 2021.
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Background: In the late 20th century great advancement was made in the field of hiking trail studies. The main concerns for these trails are susceptibility to soil erosion and dynamic landform changes in their nearest area. The impacts of the trails for vegetation were also studied with trampling and soil exposure being the most destructive. Today, With the higher and higher resolution for digital terrain models being available and advanced simulation algorithms and computing, it is possible to perform advanced modeling of a hillslope runoff.
The aim: The aim of these studies is to determine the impact of hiking trails on hillslope water runoff by comparison of the water discharge values during simulated precipitation events.
Method: The comparison is made possible, with the use of digital terrain modeling to create hillslope with and without a hiking trail, in its pre-erosion state. Both models then are subject to Simulated Water Erosion (SiMWE) based on the Monte Carlo simulation method. The algorithm is implemented in an open-source GRASS GIS program in the form of r.sim.water and r.sim.sediment modules. Exemplary hillslopes also present different scenarios based on the trail to slope alignment angle (0° - 22°; 22,1° - 45°; 45,1° - 67° and 67,1° - 90°).
During the session a case study area of a suburban mountain range within Kielce city (Poland) will be introduced, together with the results of simulation values and their spatial distribution for the exemplary hillslopes. With it, the role of the hiking trail and its environmental impact on water runoff will be better understood and easier to predict.
How to cite: Kopyść, P.: Does the trail matters? - In search of the environmental impact of hiking trails on the hillslope runoff., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-118, https://doi.org/10.5194/egusphere-egu21-118, 2021.
EGU21-130 | vPICO presentations | GM4.13 | Highlight
Fluvial sediment fluxes response to modern climate change and human activities in the Tibetan Plateau and its marginsDongfeng Li, Xixi Lu, and Ting Zhang
Sediment flux in cold environments is a crucial proxy to link glacial, periglacial, and fluvial systems and highly relevant to hydropower operation, water quality, and the riverine carbon cycle. However, the long-term impacts of climate change and multiple human activities on sediment flux changes in cold environments remain insufficiently investigated due to the lack of monitoring and the complexity of the sediment cascade. Here we examine the multi-decadal changes in the in-situ observed fluvial sediment fluxes from two types of basins, namely, pristine basins and disturbed basins, in the Tibetan Plateau and its margins. The results show that the fluvial sediment fluxes in the pristine Tuotuohe headwater have substantially increased over the past three decades (i.e., a net increase of 135% from 1985–1997 to 1998–2017) due to the warming and wetting climate. We also quantify the relative impacts of air temperature and precipitation on the increases in the sediment fluxes with a novel attribution approach and finds that climate warming and intensified glacier-snow-permafrost melting is the primary cause of the increased sediment fluxes in the pristine cold environment (Tuotuohe headwater), with precipitation increase and its associated pluvial processes being the secondary driver. By contrast, the sediment fluxes in the downstream disturbed Jinsha River (southeastern margin of the Tibetan Plateau) exhibit a net increase of 42% from 1966-1984 to 1985-2010 mainly due to human activities such as deforestation and mineral extraction (contribution of 82%) and secondly because of climate change (contribution of 18%). Then the sediment fluxes dropped by 76% during the period of 2011-2015 because of the operations of six cascade reservoirs since 2010. In an expected warming and wetting climate for the region, we predict that the sediment fluxes in the pristine headwaters of the Tibetan Plateau will continue to increase throughout the 21st century, but the rising sediment fluxes from the Tibetan Plateau would be mostly trapped in its marginal reservoirs.
Overall, this work has provided the sedimentary evidence of modern climate change through robust observational sediment flux data over multiple decades. It demonstrates that sediment fluxes in pristine cold environments are more sensitive to air temperature and thermal-driven geomorphic processes than to precipitation and pluvial-driven processes. It also provides a guide to assess the relative impacts of human activities and climate change on fluvial sediment flux changes and has significant implications for water resources stakeholders to better design and manage the hydropower dams in a changing climate. Such findings may also have implications for other cold environments such as the Arctic, Antarctic, and other high mountainous basins.
Furthermore, this research is under the project of "Water and Sediment Fluxes Response to Climate Change in the Headwater Rivers of Asian Highlands" (supported by the IPCC and the Cuomo Foundation) and the project of "Sediment Load Responses to Climate Change in High Mountain Asia" (supported by the Ministry of Education of Singapore). Part of the results are also published in Li et al., 2018 Geomorphology, Li et al., 2020 Geophysical Research Letters, and Li et al., 2021 Water Resources Research.
How to cite: Li, D., Lu, X., and Zhang, T.: Fluvial sediment fluxes response to modern climate change and human activities in the Tibetan Plateau and its margins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-130, https://doi.org/10.5194/egusphere-egu21-130, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Sediment flux in cold environments is a crucial proxy to link glacial, periglacial, and fluvial systems and highly relevant to hydropower operation, water quality, and the riverine carbon cycle. However, the long-term impacts of climate change and multiple human activities on sediment flux changes in cold environments remain insufficiently investigated due to the lack of monitoring and the complexity of the sediment cascade. Here we examine the multi-decadal changes in the in-situ observed fluvial sediment fluxes from two types of basins, namely, pristine basins and disturbed basins, in the Tibetan Plateau and its margins. The results show that the fluvial sediment fluxes in the pristine Tuotuohe headwater have substantially increased over the past three decades (i.e., a net increase of 135% from 1985–1997 to 1998–2017) due to the warming and wetting climate. We also quantify the relative impacts of air temperature and precipitation on the increases in the sediment fluxes with a novel attribution approach and finds that climate warming and intensified glacier-snow-permafrost melting is the primary cause of the increased sediment fluxes in the pristine cold environment (Tuotuohe headwater), with precipitation increase and its associated pluvial processes being the secondary driver. By contrast, the sediment fluxes in the downstream disturbed Jinsha River (southeastern margin of the Tibetan Plateau) exhibit a net increase of 42% from 1966-1984 to 1985-2010 mainly due to human activities such as deforestation and mineral extraction (contribution of 82%) and secondly because of climate change (contribution of 18%). Then the sediment fluxes dropped by 76% during the period of 2011-2015 because of the operations of six cascade reservoirs since 2010. In an expected warming and wetting climate for the region, we predict that the sediment fluxes in the pristine headwaters of the Tibetan Plateau will continue to increase throughout the 21st century, but the rising sediment fluxes from the Tibetan Plateau would be mostly trapped in its marginal reservoirs.
Overall, this work has provided the sedimentary evidence of modern climate change through robust observational sediment flux data over multiple decades. It demonstrates that sediment fluxes in pristine cold environments are more sensitive to air temperature and thermal-driven geomorphic processes than to precipitation and pluvial-driven processes. It also provides a guide to assess the relative impacts of human activities and climate change on fluvial sediment flux changes and has significant implications for water resources stakeholders to better design and manage the hydropower dams in a changing climate. Such findings may also have implications for other cold environments such as the Arctic, Antarctic, and other high mountainous basins.
Furthermore, this research is under the project of "Water and Sediment Fluxes Response to Climate Change in the Headwater Rivers of Asian Highlands" (supported by the IPCC and the Cuomo Foundation) and the project of "Sediment Load Responses to Climate Change in High Mountain Asia" (supported by the Ministry of Education of Singapore). Part of the results are also published in Li et al., 2018 Geomorphology, Li et al., 2020 Geophysical Research Letters, and Li et al., 2021 Water Resources Research.
How to cite: Li, D., Lu, X., and Zhang, T.: Fluvial sediment fluxes response to modern climate change and human activities in the Tibetan Plateau and its margins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-130, https://doi.org/10.5194/egusphere-egu21-130, 2021.
EGU21-5397 | vPICO presentations | GM4.13
Cascading processes of the Vaia storm in the italian Rio Cordon mountain catchmentGiacomo Pellegrini, Riccardo Rainato, Lorenzo Martini, Luca Mao, and Lorenzo Picco
Mountain basins can be affected by Large Infrequent Disturbances (LIDs) that have the power of changing their forest cover and morphological settings, and supplying high amounts of sediments to river networks. The resulting cascading processes are often underestimated although their understanding would improve river management strategies. The recent improvements in the field of sediment transport monitoring and analysis allow to gather a deeper understanding of these long-lasting and complex chains of processes, especially in mountain streams. This contribution aims at investigating the suspended sediment transport exhibited by two recent (summer-autumn 2020) over-bankfull (> 2.3 m3/s) flood events occurred in the Rio Cordon, an alpine basin (5 km2) strongly altered by the Vaia storm (October 2018). This LID blew down 139 trees along the main active channel that were removed by local forest operations after the event, leaving exposed banks and increasing the availability of fine sediment. Two water quality sondes were placed upstream and downstream the windthrow affected area (WAA) to monitor the Suspended Sediment Load (SSL) and quantify the contribution of the WAA in supplying sediments. Water discharge and suspended sediment transport were continuously measured by the two instrumentations, while water samples and direct discharge measurements (salt dilution method) were taken to derive rating curves and calibrate the turbidity meters. Results show that the early September 2020 event (Qmax=2.67 m3/s) produced a SSL = 39.27 t and a SSL increase of +5% between the downstream and upstream cross-section. To this, it was also registered a +44% variation of SS maximum concentration (SSC g/l) which can be ascribed to the contribution of the WWA. The event of October 2020 (Qmax=3.05 m3/s) instead, registered a SSL of 179.22 t and a SSL and SSCmax variation of +334% and +81%, respectively. The preliminary results suggest that the SS is not related to the water discharge but for this reason, further analysis and data collection will be made, also considering rainfall data. However, the ongoing monitoring of this area represents a suitable and promising approach for understanding the cascading processes on the SS dynamics in a mountain basin affected by a LID.
How to cite: Pellegrini, G., Rainato, R., Martini, L., Mao, L., and Picco, L.: Cascading processes of the Vaia storm in the italian Rio Cordon mountain catchment , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5397, https://doi.org/10.5194/egusphere-egu21-5397, 2021.
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Mountain basins can be affected by Large Infrequent Disturbances (LIDs) that have the power of changing their forest cover and morphological settings, and supplying high amounts of sediments to river networks. The resulting cascading processes are often underestimated although their understanding would improve river management strategies. The recent improvements in the field of sediment transport monitoring and analysis allow to gather a deeper understanding of these long-lasting and complex chains of processes, especially in mountain streams. This contribution aims at investigating the suspended sediment transport exhibited by two recent (summer-autumn 2020) over-bankfull (> 2.3 m3/s) flood events occurred in the Rio Cordon, an alpine basin (5 km2) strongly altered by the Vaia storm (October 2018). This LID blew down 139 trees along the main active channel that were removed by local forest operations after the event, leaving exposed banks and increasing the availability of fine sediment. Two water quality sondes were placed upstream and downstream the windthrow affected area (WAA) to monitor the Suspended Sediment Load (SSL) and quantify the contribution of the WAA in supplying sediments. Water discharge and suspended sediment transport were continuously measured by the two instrumentations, while water samples and direct discharge measurements (salt dilution method) were taken to derive rating curves and calibrate the turbidity meters. Results show that the early September 2020 event (Qmax=2.67 m3/s) produced a SSL = 39.27 t and a SSL increase of +5% between the downstream and upstream cross-section. To this, it was also registered a +44% variation of SS maximum concentration (SSC g/l) which can be ascribed to the contribution of the WWA. The event of October 2020 (Qmax=3.05 m3/s) instead, registered a SSL of 179.22 t and a SSL and SSCmax variation of +334% and +81%, respectively. The preliminary results suggest that the SS is not related to the water discharge but for this reason, further analysis and data collection will be made, also considering rainfall data. However, the ongoing monitoring of this area represents a suitable and promising approach for understanding the cascading processes on the SS dynamics in a mountain basin affected by a LID.
How to cite: Pellegrini, G., Rainato, R., Martini, L., Mao, L., and Picco, L.: Cascading processes of the Vaia storm in the italian Rio Cordon mountain catchment , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5397, https://doi.org/10.5194/egusphere-egu21-5397, 2021.
EGU21-1201 | vPICO presentations | GM4.13
Disturbances in coarse bedload transport in a formerly glaciated catchmentEliza Płaczkowska, Kazimierz Krzemień, Elżbieta Gorczyca, Anna Bojarczuk, and Mirosław Żelazny
Dynamics of bedload transport increases with an increase of hydrologic parameters, i.e. stream power, water velocity and discharge. In mountain stream channels, these parameters increase in the downstream direction, and therefore the dynamics of bedload transport increase down the channel. This pattern may become altered temporarily or over long periods of time due to local extreme events or human impact. Here, we identify disturbances in bedload transport in the formerly glaciated catchment located in the Western Tatras in Poland. We then determine the role of disturbances in system connectivity and sediment transfer. Bedload transport measurements in the Chochołowski catchment were performed in the period 1975 to 2018. The said process occurred as many as triggered up to several times a year. However bedload became activated along the entire length of the channel system (10.5 km) every 2 to 5 years when the stream discharge exceeded 10 m3 s-1. The distance of bedload movement during such events was between 12 m in headwaters and over 100 m in the lower reach. In such situations, bedload dynamics increased downstream, and stream power was sufficient to overcome local barriers (i.e. boulder and log steps). Downstream increases in bedload dynamics was disturbed and inverted by sudden snowmelt and locally heavy rainfall. These types of events caused the dynamics of bedload transport to be up to 320% greater in the upper part of the studied catchment and to decline in the downstream direction over a distance of 7 km to yield an attenuation effect. The same pattern was observed in local tributaries where the dynamics of bedload transport were 200% higher in the upper part and attenuation was observed along a distance of 1.5 km in the downstream direction. All events of this type cause seasonal disturbances in bedload transport. However, the greatest effect on bedload dynamics was produced by natural deforestation. A 16% decrease in forest cover causes a fluvial system disequilibrium manifested in an intensification of hydro-geomorphologic processes and formation of new landforms.
How to cite: Płaczkowska, E., Krzemień, K., Gorczyca, E., Bojarczuk, A., and Żelazny, M.: Disturbances in coarse bedload transport in a formerly glaciated catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1201, https://doi.org/10.5194/egusphere-egu21-1201, 2021.
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Dynamics of bedload transport increases with an increase of hydrologic parameters, i.e. stream power, water velocity and discharge. In mountain stream channels, these parameters increase in the downstream direction, and therefore the dynamics of bedload transport increase down the channel. This pattern may become altered temporarily or over long periods of time due to local extreme events or human impact. Here, we identify disturbances in bedload transport in the formerly glaciated catchment located in the Western Tatras in Poland. We then determine the role of disturbances in system connectivity and sediment transfer. Bedload transport measurements in the Chochołowski catchment were performed in the period 1975 to 2018. The said process occurred as many as triggered up to several times a year. However bedload became activated along the entire length of the channel system (10.5 km) every 2 to 5 years when the stream discharge exceeded 10 m3 s-1. The distance of bedload movement during such events was between 12 m in headwaters and over 100 m in the lower reach. In such situations, bedload dynamics increased downstream, and stream power was sufficient to overcome local barriers (i.e. boulder and log steps). Downstream increases in bedload dynamics was disturbed and inverted by sudden snowmelt and locally heavy rainfall. These types of events caused the dynamics of bedload transport to be up to 320% greater in the upper part of the studied catchment and to decline in the downstream direction over a distance of 7 km to yield an attenuation effect. The same pattern was observed in local tributaries where the dynamics of bedload transport were 200% higher in the upper part and attenuation was observed along a distance of 1.5 km in the downstream direction. All events of this type cause seasonal disturbances in bedload transport. However, the greatest effect on bedload dynamics was produced by natural deforestation. A 16% decrease in forest cover causes a fluvial system disequilibrium manifested in an intensification of hydro-geomorphologic processes and formation of new landforms.
How to cite: Płaczkowska, E., Krzemień, K., Gorczyca, E., Bojarczuk, A., and Żelazny, M.: Disturbances in coarse bedload transport in a formerly glaciated catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1201, https://doi.org/10.5194/egusphere-egu21-1201, 2021.
EGU21-10041 | vPICO presentations | GM4.13
Spatial variation in sediment fluxes along the western slopes of the Peruvian AndesMiluska Rosas Barturen, Veerle Vanacker, François Clapuyt, and Willem Viveen
Knowledge of sediment production mechanisms and their potential controlling factors contributes to our understanding of geomorphological processes. Previous studies highlighted the link between sediment yield and anthropogenic (e.g. agricultural practices) and natural factors (e.g. climate, topography, river runoff, lithology and vegetation cover). The rugged western slopes of the Peruvian Andes shows different climate regimes with arid climates and desertic vegetation in the south and tropical climates and abundant vegetation in the north. In this region, agricultural and water regulation projects are concentrated.
However, the number of studies on sediment yield and its controlling factors are limited along the Peruvian Andes. Most studies on the western slopes have focused on the Northern part of Peru and showed a 3 to 60 times increase of sediment yield during El Niño (ENSO) events compared to normal years. The storm events rapidly mobilized sediment that was accumulated in the mountain and piedmont areas during dry normal years. In the central part of Peru where the main reservoirs, irrigation systems, and water supply plants are located, few studies were realized. They concluded that the relation between sediment production and both environmental and anthropogenic controlling factors needs to be further explored.
In this study, we identify the spatial patterns of sediment yield along the western slopes of the Peruvian Andes and analyze the main environmental controlling factors. Our study presents data on sediment yield of 20 catchments. The data contains information on suspended sediment load from gauging stations, reservoir sedimentation and water turbidity. We used satellite-based data to derive topographic information (SRTM v.3 DEM by NASA), daily precipitation covering the period 1981 to 2016 (PISCO product by Senamhi), daily discharge covering 1970 to 2020 (GloFAS-ERA5 global river dataset), lithological strength (global lithological map GLiM), and vegetative cover (MODIS Land cover type product). Our first results show a significant influence of the lithology, maximum discharge and topographic relief on sediment yield. The results of the analyses for the Peruvian Andes will be compared with previous studies in the Northern and Southern Andes.
How to cite: Rosas Barturen, M., Vanacker, V., Clapuyt, F., and Viveen, W.: Spatial variation in sediment fluxes along the western slopes of the Peruvian Andes , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10041, https://doi.org/10.5194/egusphere-egu21-10041, 2021.
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Knowledge of sediment production mechanisms and their potential controlling factors contributes to our understanding of geomorphological processes. Previous studies highlighted the link between sediment yield and anthropogenic (e.g. agricultural practices) and natural factors (e.g. climate, topography, river runoff, lithology and vegetation cover). The rugged western slopes of the Peruvian Andes shows different climate regimes with arid climates and desertic vegetation in the south and tropical climates and abundant vegetation in the north. In this region, agricultural and water regulation projects are concentrated.
However, the number of studies on sediment yield and its controlling factors are limited along the Peruvian Andes. Most studies on the western slopes have focused on the Northern part of Peru and showed a 3 to 60 times increase of sediment yield during El Niño (ENSO) events compared to normal years. The storm events rapidly mobilized sediment that was accumulated in the mountain and piedmont areas during dry normal years. In the central part of Peru where the main reservoirs, irrigation systems, and water supply plants are located, few studies were realized. They concluded that the relation between sediment production and both environmental and anthropogenic controlling factors needs to be further explored.
In this study, we identify the spatial patterns of sediment yield along the western slopes of the Peruvian Andes and analyze the main environmental controlling factors. Our study presents data on sediment yield of 20 catchments. The data contains information on suspended sediment load from gauging stations, reservoir sedimentation and water turbidity. We used satellite-based data to derive topographic information (SRTM v.3 DEM by NASA), daily precipitation covering the period 1981 to 2016 (PISCO product by Senamhi), daily discharge covering 1970 to 2020 (GloFAS-ERA5 global river dataset), lithological strength (global lithological map GLiM), and vegetative cover (MODIS Land cover type product). Our first results show a significant influence of the lithology, maximum discharge and topographic relief on sediment yield. The results of the analyses for the Peruvian Andes will be compared with previous studies in the Northern and Southern Andes.
How to cite: Rosas Barturen, M., Vanacker, V., Clapuyt, F., and Viveen, W.: Spatial variation in sediment fluxes along the western slopes of the Peruvian Andes , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10041, https://doi.org/10.5194/egusphere-egu21-10041, 2021.
EGU21-729 | vPICO presentations | GM4.13
Natural and anthropogenic drivers of denudation and sedimentary source-to-sink fluxes in the boreal mountain basin of lake Selbusjøen in central NorwayAchim A. Beylich and Katja Laute
Denudation, including both chemical and mechanical processes, is of high relevance for landscape development and the transfer of solutes and sediments from headwater systems through main stem of drainage basin systems into sinks like lakes or the sea. Denudation is controlled by a range of environmental drivers and is in most environments and landscapes worldwide significantly affected by anthropogenic activities.
In the boreal mountain environment of central Norway the regulated lake Selbusjøen, situated at ca. 160 m a.s.l. with an area of 58 km2 and connecting the upstream main mountain river Nea and the downstream main river Nidelva, forms a significant sink for sediments being transferred from its drainage basin area of in total 2876 km2. The significant sediment trapping efficiency of lake Selbusjøen is causing a sediment deficit and locally increased fluvial erosion and down-cutting in the downstream river Nidelva which drains into the Trondheim fjord.
This ongoing GFL research on natural and anthropogenic drivers and the spatiotemporal variability of contemporary chemical and mechanical fluvial denudation rates and sedimentary source-to-sink fluxes in the boreal mountain basin of lake Selbusjøen is based on statistical analyses of high-resolution meteorological data, detailed field and remotely sensed mapping, computing of morphometric catchment parameters, and year-round process geomorphological field work. Geomorphological field work includes detailed field observations, repeated photographic documentations of selected stream channel stretches and slope surface areas, and field monitoring and frequent measurements with snow, rain water, stream-water and bedload samplings for the analysis of solute and suspended sediment concentrations and the study of atmospheric solute inputs, and the quantification of fluvial solute and sediment transport. Field work is carried out in 25 defined catchments/drainage areas draining into Selbusjøen. The selected catchment/drainage area systems are all characterized by large surface areas with a nearly closed and continuous vegetation cover mostly composed of boreal forests and bogs, and represent a range of different catchment sizes, catchment morphometries, orientations/aspects, and sediment sources and availabilities. In addition, different types and intensities of anthropogenic impact like, e.g., agriculture, forestry and modifications of natural stream channels (e.g., dams, steps, bank protection) and channel discharge for water power purposes are found in various catchments.
Runoff is occurring year-round and the natural runoff regime is clearly nival. Most fluvial transport is occurring during peak-runoff events generated by snowmelt, rainfall events or combinations of snowmelt and rainfall. Altogether, chemical denudation is moderate but dominates clearly over mechanical fluvial denudation. Both chemical and mechanical fluvial denudation show a significant spatial variability which can be related to the varying characteristics of the selected catchment/drainage area systems. Agriculture and forestry are generally increasing mechanical fluvial denudation rates whereas anthropogenic stream channel and channel discharge modifications are leading to reduced fluvial bedload transport rates into lake Selbusjøen. Ongoing and accelerated climate change with the related changes of the current wind, temperature and precipitation regimes are expected to increase both chemical and mechanical fluvial denudation and sediment transport rates into lake Selbusjøen, particularly in the surface areas that have been modified by anthropogenic activities.
How to cite: Beylich, A. A. and Laute, K.: Natural and anthropogenic drivers of denudation and sedimentary source-to-sink fluxes in the boreal mountain basin of lake Selbusjøen in central Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-729, https://doi.org/10.5194/egusphere-egu21-729, 2021.
Denudation, including both chemical and mechanical processes, is of high relevance for landscape development and the transfer of solutes and sediments from headwater systems through main stem of drainage basin systems into sinks like lakes or the sea. Denudation is controlled by a range of environmental drivers and is in most environments and landscapes worldwide significantly affected by anthropogenic activities.
In the boreal mountain environment of central Norway the regulated lake Selbusjøen, situated at ca. 160 m a.s.l. with an area of 58 km2 and connecting the upstream main mountain river Nea and the downstream main river Nidelva, forms a significant sink for sediments being transferred from its drainage basin area of in total 2876 km2. The significant sediment trapping efficiency of lake Selbusjøen is causing a sediment deficit and locally increased fluvial erosion and down-cutting in the downstream river Nidelva which drains into the Trondheim fjord.
This ongoing GFL research on natural and anthropogenic drivers and the spatiotemporal variability of contemporary chemical and mechanical fluvial denudation rates and sedimentary source-to-sink fluxes in the boreal mountain basin of lake Selbusjøen is based on statistical analyses of high-resolution meteorological data, detailed field and remotely sensed mapping, computing of morphometric catchment parameters, and year-round process geomorphological field work. Geomorphological field work includes detailed field observations, repeated photographic documentations of selected stream channel stretches and slope surface areas, and field monitoring and frequent measurements with snow, rain water, stream-water and bedload samplings for the analysis of solute and suspended sediment concentrations and the study of atmospheric solute inputs, and the quantification of fluvial solute and sediment transport. Field work is carried out in 25 defined catchments/drainage areas draining into Selbusjøen. The selected catchment/drainage area systems are all characterized by large surface areas with a nearly closed and continuous vegetation cover mostly composed of boreal forests and bogs, and represent a range of different catchment sizes, catchment morphometries, orientations/aspects, and sediment sources and availabilities. In addition, different types and intensities of anthropogenic impact like, e.g., agriculture, forestry and modifications of natural stream channels (e.g., dams, steps, bank protection) and channel discharge for water power purposes are found in various catchments.
Runoff is occurring year-round and the natural runoff regime is clearly nival. Most fluvial transport is occurring during peak-runoff events generated by snowmelt, rainfall events or combinations of snowmelt and rainfall. Altogether, chemical denudation is moderate but dominates clearly over mechanical fluvial denudation. Both chemical and mechanical fluvial denudation show a significant spatial variability which can be related to the varying characteristics of the selected catchment/drainage area systems. Agriculture and forestry are generally increasing mechanical fluvial denudation rates whereas anthropogenic stream channel and channel discharge modifications are leading to reduced fluvial bedload transport rates into lake Selbusjøen. Ongoing and accelerated climate change with the related changes of the current wind, temperature and precipitation regimes are expected to increase both chemical and mechanical fluvial denudation and sediment transport rates into lake Selbusjøen, particularly in the surface areas that have been modified by anthropogenic activities.
How to cite: Beylich, A. A. and Laute, K.: Natural and anthropogenic drivers of denudation and sedimentary source-to-sink fluxes in the boreal mountain basin of lake Selbusjøen in central Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-729, https://doi.org/10.5194/egusphere-egu21-729, 2021.
EGU21-16058 | vPICO presentations | GM4.13
Spatial distribution of denudation processes in BhutanMałgorzata Mazurek, Zbigniew Zwoliński, and Przemysław Niedzielski
Bhutan, being a Himalayan mountain country, extends ca. 305 km from west to east and 145 km from south to north, covering an area of 47,000 km2. Bhutanese Himalaya mountains are divided into three latitudinal belts from south to north: the sub-Himalayas or Himalayan foothills (up to 1,500 m in altitude), the inner Himalayas or middle ranges with flat valleys (from 1,500 to 4,500 m), and the Great Himalayas of high mountains (about 4 500 m). The Black Mountain Range, stretching longitudinally, divides this country into the eastern and western parts. The belt system of landforms is closely related to the geological structure. In the north, metamorphic and crystalline rocks (mainly gneisses and granites) dominate, while in the south there are sedimentary rocks associated with the molasse-like sediments in the Siwalik range. The distribution of precipitation from approx. 500 mm in the north to 5000 mm in the south of the country relates to this geological and morphological belt system. The main rivers flow longitudinally and have perpendicular tributaries. The digital elevation model of Bhutan was analysed geomorphometrically and, on this basis, places with high potential mechanical denudation were identified. The most evident manifestation of this denudation are numerous landslides occurring on the valley slopes. These landslides, especially in the monsoons period, deliver enormous amounts of landslide material to the valley bottoms, and most often directly to the river channels. The landslide material in the form of fluvial material is further transported along the rivers and deposited in the foreland of the Himalayas. After the summer monsoon period, water samples were collected in selected rivers. The collected water samples were subjected to hydrochemical analyzes. The studied river waters in the middle part of the country are characterized by low mineralization. The obtained results allow for a preliminary characterization of the spatial diversification of the denudation potential of Bhutan's river waters. Referring to the physiographic division of Bhutan, it can be confirmed that the middle zones, meridional ridges and valleys of this country are characterized by low chemical denudation and high mechanical denudation, while the southern tips of the country Front Hills and Piedmont are dominated by accumulation processes due to a significant reduction in river gradient.
How to cite: Mazurek, M., Zwoliński, Z., and Niedzielski, P.: Spatial distribution of denudation processes in Bhutan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16058, https://doi.org/10.5194/egusphere-egu21-16058, 2021.
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Bhutan, being a Himalayan mountain country, extends ca. 305 km from west to east and 145 km from south to north, covering an area of 47,000 km2. Bhutanese Himalaya mountains are divided into three latitudinal belts from south to north: the sub-Himalayas or Himalayan foothills (up to 1,500 m in altitude), the inner Himalayas or middle ranges with flat valleys (from 1,500 to 4,500 m), and the Great Himalayas of high mountains (about 4 500 m). The Black Mountain Range, stretching longitudinally, divides this country into the eastern and western parts. The belt system of landforms is closely related to the geological structure. In the north, metamorphic and crystalline rocks (mainly gneisses and granites) dominate, while in the south there are sedimentary rocks associated with the molasse-like sediments in the Siwalik range. The distribution of precipitation from approx. 500 mm in the north to 5000 mm in the south of the country relates to this geological and morphological belt system. The main rivers flow longitudinally and have perpendicular tributaries. The digital elevation model of Bhutan was analysed geomorphometrically and, on this basis, places with high potential mechanical denudation were identified. The most evident manifestation of this denudation are numerous landslides occurring on the valley slopes. These landslides, especially in the monsoons period, deliver enormous amounts of landslide material to the valley bottoms, and most often directly to the river channels. The landslide material in the form of fluvial material is further transported along the rivers and deposited in the foreland of the Himalayas. After the summer monsoon period, water samples were collected in selected rivers. The collected water samples were subjected to hydrochemical analyzes. The studied river waters in the middle part of the country are characterized by low mineralization. The obtained results allow for a preliminary characterization of the spatial diversification of the denudation potential of Bhutan's river waters. Referring to the physiographic division of Bhutan, it can be confirmed that the middle zones, meridional ridges and valleys of this country are characterized by low chemical denudation and high mechanical denudation, while the southern tips of the country Front Hills and Piedmont are dominated by accumulation processes due to a significant reduction in river gradient.
How to cite: Mazurek, M., Zwoliński, Z., and Niedzielski, P.: Spatial distribution of denudation processes in Bhutan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16058, https://doi.org/10.5194/egusphere-egu21-16058, 2021.
EGU21-13140 | vPICO presentations | GM4.13
Fire-induced catchment erosion on a depleted soil system from GeoWEPP and RUSLE models, Santa Olga, ChileVioleta Tolorza, Dagoberto Poblete, Virginia I. González, Mauricio Zambrano-Bigiarini, Julián Cabezas, and Mauricio Galleguillos
The recent increase in frequency and extent of severe wildfires in South-Central Chile is degrading the already eroded soils of the Coastal Cordillera. Spatially explicit quantification of erosion triggered by that disturbances may reveal useful information for soil conservation and land planning purposes, which is especially relevant in drinking-water catchments. We compared estimations of water erosion using a process-based and an empirical modeling approaches in a small (173 ha) burned drinking water catchment. To this end, we implemented the GeoWEPP process-based model and the RUSLE empirical approach for different scenarios of wildfire severity using remote sensing, in situ soil and hydro-meteorological data (2001-2019). Individual Hydrologic Response Units resulted in very low erosion rates in GeoWEPP respect to RUSLE, while both simulations represent low erosion rates respect to observations reported for other latitudes of the Coastal Cordillera. Those low erosion rates could be explained by low rainfall erosivity and high critical shear stress, which in turn is a consequence of soil compaction. The spatial variations of the modeled sediment yields (2001-2019) were associated both to the wildfire and to the land management at hillslopes, which involves clear cut timber harvest at most forest plantations areas. A better quantification of those erosion processes is necessary to improve the understanding of the evolution of Chilean forestry landscape, in order to prioritize efforts for soil conservation and ecosystem restoration.
How to cite: Tolorza, V., Poblete, D., González, V. I., Zambrano-Bigiarini, M., Cabezas, J., and Galleguillos, M.: Fire-induced catchment erosion on a depleted soil system from GeoWEPP and RUSLE models, Santa Olga, Chile, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13140, https://doi.org/10.5194/egusphere-egu21-13140, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The recent increase in frequency and extent of severe wildfires in South-Central Chile is degrading the already eroded soils of the Coastal Cordillera. Spatially explicit quantification of erosion triggered by that disturbances may reveal useful information for soil conservation and land planning purposes, which is especially relevant in drinking-water catchments. We compared estimations of water erosion using a process-based and an empirical modeling approaches in a small (173 ha) burned drinking water catchment. To this end, we implemented the GeoWEPP process-based model and the RUSLE empirical approach for different scenarios of wildfire severity using remote sensing, in situ soil and hydro-meteorological data (2001-2019). Individual Hydrologic Response Units resulted in very low erosion rates in GeoWEPP respect to RUSLE, while both simulations represent low erosion rates respect to observations reported for other latitudes of the Coastal Cordillera. Those low erosion rates could be explained by low rainfall erosivity and high critical shear stress, which in turn is a consequence of soil compaction. The spatial variations of the modeled sediment yields (2001-2019) were associated both to the wildfire and to the land management at hillslopes, which involves clear cut timber harvest at most forest plantations areas. A better quantification of those erosion processes is necessary to improve the understanding of the evolution of Chilean forestry landscape, in order to prioritize efforts for soil conservation and ecosystem restoration.
How to cite: Tolorza, V., Poblete, D., González, V. I., Zambrano-Bigiarini, M., Cabezas, J., and Galleguillos, M.: Fire-induced catchment erosion on a depleted soil system from GeoWEPP and RUSLE models, Santa Olga, Chile, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13140, https://doi.org/10.5194/egusphere-egu21-13140, 2021.
EGU21-3312 | vPICO presentations | GM4.13
Disentangling the effect of past and present agroforestry practices in modifying landscapes of Mediterranean mountainsIvan Lizaga, Leticia Gaspar, Borja Latorre, and Ana Navas
Soil erosion and sediment delivery to rivers are important drivers for land degradation and environmental change in mountain agroecosystems. These factors are especially severe in areas affected by intermittent heavy rainfalls after dry periods, and human practices such as deforestation or clearcutting practices. Many Mediterranean mountain environments underwent conversion of rangelands into croplands during the previous centuries increasing the risk of erosion. After land abandonment the process was gradually reversed during the middle of the 20thcentury, allowing the recovery of natural land cover and reduced soil erosion rates. To further control the high erosion rates, several afforestation programs introduced pine forests at the headwater of most Mediterranean mountain catchments transforming the landscape by terracing and reducing the sediment connectivity. However, nowadays, forests’ different management could lead to high erosion rates and subsequent landscape modifications. To understand the possible effect of these practices together with the current agricultural management, we have combined the strength of empirical data and spatially distributed modelling. Surface soil samples from different land uses were collected in a representative catchment at the foot of Santo Domingo range at the border of the central Ebro River valley. The study catchment was mostly cultivated at the beginning of the 19th century but changed to rangeland and pine afforestation in the last 50 years. The remaining croplands are predominated by rainfed agriculture that leaves soils mostly unprotected from June to January when erosive storms occur. The main land uses are croplands, pine afforestation, scrubland and Mediterranean forest.
In this study, we propose an ensemble technique composed of 137Cs derived soil redistribution rates as specific point values and as a calibration tool for the widely used WaTEM/SEDEM sediment delivery model. Thus, by the use of ground truth and modelled data we aim to i) apply the WaTEM/SEDEM model at the catchment scale and calibrate it with 137Cs derived soil redistribution rates for finding an optimal set of input parameters; ii) examine the effect of clearcutting and agricultural practices on the total erosion; iii) compare the modelled results with recently calculated sediment apportionments by using the sediment fingerprinting technique.
Our findings highlight the use of spatially distributed models combined with 137Cs derived rates as a powerful tool to understand the driving factors of soil erosion in the last decades and to delineate the hotspot areas that could suffer high erosion if subjected to certain management practices.
How to cite: Lizaga, I., Gaspar, L., Latorre, B., and Navas, A.: Disentangling the effect of past and present agroforestry practices in modifying landscapes of Mediterranean mountains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3312, https://doi.org/10.5194/egusphere-egu21-3312, 2021.
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Soil erosion and sediment delivery to rivers are important drivers for land degradation and environmental change in mountain agroecosystems. These factors are especially severe in areas affected by intermittent heavy rainfalls after dry periods, and human practices such as deforestation or clearcutting practices. Many Mediterranean mountain environments underwent conversion of rangelands into croplands during the previous centuries increasing the risk of erosion. After land abandonment the process was gradually reversed during the middle of the 20thcentury, allowing the recovery of natural land cover and reduced soil erosion rates. To further control the high erosion rates, several afforestation programs introduced pine forests at the headwater of most Mediterranean mountain catchments transforming the landscape by terracing and reducing the sediment connectivity. However, nowadays, forests’ different management could lead to high erosion rates and subsequent landscape modifications. To understand the possible effect of these practices together with the current agricultural management, we have combined the strength of empirical data and spatially distributed modelling. Surface soil samples from different land uses were collected in a representative catchment at the foot of Santo Domingo range at the border of the central Ebro River valley. The study catchment was mostly cultivated at the beginning of the 19th century but changed to rangeland and pine afforestation in the last 50 years. The remaining croplands are predominated by rainfed agriculture that leaves soils mostly unprotected from June to January when erosive storms occur. The main land uses are croplands, pine afforestation, scrubland and Mediterranean forest.
In this study, we propose an ensemble technique composed of 137Cs derived soil redistribution rates as specific point values and as a calibration tool for the widely used WaTEM/SEDEM sediment delivery model. Thus, by the use of ground truth and modelled data we aim to i) apply the WaTEM/SEDEM model at the catchment scale and calibrate it with 137Cs derived soil redistribution rates for finding an optimal set of input parameters; ii) examine the effect of clearcutting and agricultural practices on the total erosion; iii) compare the modelled results with recently calculated sediment apportionments by using the sediment fingerprinting technique.
Our findings highlight the use of spatially distributed models combined with 137Cs derived rates as a powerful tool to understand the driving factors of soil erosion in the last decades and to delineate the hotspot areas that could suffer high erosion if subjected to certain management practices.
How to cite: Lizaga, I., Gaspar, L., Latorre, B., and Navas, A.: Disentangling the effect of past and present agroforestry practices in modifying landscapes of Mediterranean mountains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3312, https://doi.org/10.5194/egusphere-egu21-3312, 2021.
EGU21-12149 | vPICO presentations | GM4.13
Landslide dams acting as sediment traps: Example of the lake Hintersee, Berchtesgadener Land, south-eastern GermanyThomas Hauthaler, Anne-Laure Argentin, Jörg Robl, Günther Prasicek, Daniel Hölbling, Stefan Hergarten, Lorena Abad, and Zahra Dabiri
Landslide dams occur when a landslide deposits in the riverbed and stop the river flow, creating lakes. They act as big sediments traps that modify the sediment flux in the whole catchment. By changing the sediment load, the dams change the erosion rates upstream and downstream. Although most landslide-dammed lakes are ephemeral, some stay in place and disappear only when they have been filled with sediments. We study the Hintersee lake in the Berchtesgadener Land, Germany, and aim to determine the sediment budget of the infilled lake and the dam duration before breaching. This landslide dam formed 3520 years BP from a rockslide of 15-18 x 106 m3. We propose to reproduce the formation of the Hintersee landslide dam and its infilling using different scenarios. We first use a 1 m resolution digital elevation model to rebuild the valley floor before the rockslide event, three different rockslide source areas and the landslide dam shape before fluvial incision. We apply the Gerris shallow water flow solver to simulate the landslide runout and to recreate the landslide dam deposition characteristics from the different source topographies and several Voellmy rheologies. We choose the best-fitting scenario to assess a sediment budget of the Hintersee landslide-dammed lake.
How to cite: Hauthaler, T., Argentin, A.-L., Robl, J., Prasicek, G., Hölbling, D., Hergarten, S., Abad, L., and Dabiri, Z.: Landslide dams acting as sediment traps: Example of the lake Hintersee, Berchtesgadener Land, south-eastern Germany , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12149, https://doi.org/10.5194/egusphere-egu21-12149, 2021.
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Landslide dams occur when a landslide deposits in the riverbed and stop the river flow, creating lakes. They act as big sediments traps that modify the sediment flux in the whole catchment. By changing the sediment load, the dams change the erosion rates upstream and downstream. Although most landslide-dammed lakes are ephemeral, some stay in place and disappear only when they have been filled with sediments. We study the Hintersee lake in the Berchtesgadener Land, Germany, and aim to determine the sediment budget of the infilled lake and the dam duration before breaching. This landslide dam formed 3520 years BP from a rockslide of 15-18 x 106 m3. We propose to reproduce the formation of the Hintersee landslide dam and its infilling using different scenarios. We first use a 1 m resolution digital elevation model to rebuild the valley floor before the rockslide event, three different rockslide source areas and the landslide dam shape before fluvial incision. We apply the Gerris shallow water flow solver to simulate the landslide runout and to recreate the landslide dam deposition characteristics from the different source topographies and several Voellmy rheologies. We choose the best-fitting scenario to assess a sediment budget of the Hintersee landslide-dammed lake.
How to cite: Hauthaler, T., Argentin, A.-L., Robl, J., Prasicek, G., Hölbling, D., Hergarten, S., Abad, L., and Dabiri, Z.: Landslide dams acting as sediment traps: Example of the lake Hintersee, Berchtesgadener Land, south-eastern Germany , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12149, https://doi.org/10.5194/egusphere-egu21-12149, 2021.
EGU21-12236 | vPICO presentations | GM4.13
Hydrosedimentary connectivity in a disturbed forested catchment: toward a temporally dynamic index of connectivityMaxime Maltais, Timothée Jautzy, and Thomas Buffin-Bélanger
Hydrosedimentary connectivity refers to the potential fluxes of water and sediment moving throughout a catchment. In forested catchments, these fluxes are altered by anthropogenic and natural disturbances. In this study, we modelled the interannual spatiotemporal evolution of hydrosedimentary connectivity influenced by forest cover change over the last four decades in the Mont-Louis catchment, a snow-dominated mountainous catchment in eastern Canada, which had 62% of its total surface affected by forest disturbances (mainly logging, but also wildfires and diseases) between 1979 and 2017. Using a geomorphometric index of connectivity (IC) and a historical forest cover database, we produced one IC map per year that considered anthropogenic and natural disturbances affecting the forest cover of the studied catchment. To account for vegetation recovery, forest disturbances were weighted with local hydrological recovery rates. Over the four decades, the mean IC of the Mont-Louis catchment dramatically increased by 35% in response to different types of disturbances. The spatial evolution of IC over the whole catchment and at the sub-catchment scale revealed that disturbance location has a strong influence on hydrosedimentary connectivity to the main channel. Our results also highlight the sharp contrast between IC computed from topography-based impedance to those computed from vegetation-based impedance. Forest disturbances appear to connect hillslopes with the hydrological network by producing pathways for sediment and water. The proposed reproducible framework might be used as a tool to assess and predict the potential impact of harvesting on rivers morphological dynamics and eventually preventing damage to fish habitat and sensitive river reaches.
How to cite: Maltais, M., Jautzy, T., and Buffin-Bélanger, T.: Hydrosedimentary connectivity in a disturbed forested catchment: toward a temporally dynamic index of connectivity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12236, https://doi.org/10.5194/egusphere-egu21-12236, 2021.
Hydrosedimentary connectivity refers to the potential fluxes of water and sediment moving throughout a catchment. In forested catchments, these fluxes are altered by anthropogenic and natural disturbances. In this study, we modelled the interannual spatiotemporal evolution of hydrosedimentary connectivity influenced by forest cover change over the last four decades in the Mont-Louis catchment, a snow-dominated mountainous catchment in eastern Canada, which had 62% of its total surface affected by forest disturbances (mainly logging, but also wildfires and diseases) between 1979 and 2017. Using a geomorphometric index of connectivity (IC) and a historical forest cover database, we produced one IC map per year that considered anthropogenic and natural disturbances affecting the forest cover of the studied catchment. To account for vegetation recovery, forest disturbances were weighted with local hydrological recovery rates. Over the four decades, the mean IC of the Mont-Louis catchment dramatically increased by 35% in response to different types of disturbances. The spatial evolution of IC over the whole catchment and at the sub-catchment scale revealed that disturbance location has a strong influence on hydrosedimentary connectivity to the main channel. Our results also highlight the sharp contrast between IC computed from topography-based impedance to those computed from vegetation-based impedance. Forest disturbances appear to connect hillslopes with the hydrological network by producing pathways for sediment and water. The proposed reproducible framework might be used as a tool to assess and predict the potential impact of harvesting on rivers morphological dynamics and eventually preventing damage to fish habitat and sensitive river reaches.
How to cite: Maltais, M., Jautzy, T., and Buffin-Bélanger, T.: Hydrosedimentary connectivity in a disturbed forested catchment: toward a temporally dynamic index of connectivity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12236, https://doi.org/10.5194/egusphere-egu21-12236, 2021.
EGU21-2499 | vPICO presentations | GM4.13
The effects of the storm Gloria in Catalonia: The value of quick-response geological inventories as a tool for risk managementMarta González, Maria Jesus Micheo, Jordi Pinyol, Maria Rosa Carles, Eulàlia Pi, Miquel Vila, and Antoni Roca
The storm Gloria was an exceptional episode of east storm occurred in the north and east of Spain from Sunday 19th to Thursday 23rd of January 2020. The impact was especially strong in the Mediterranean coast, causing the overflow of some rivers, abundant slope movements, cuts in the road and rail network, isolation of populations, and huge damage on the coastline. It was classified as historical, not only because of the multiplicity of phenomena (wind, rain, snow, and waves) that happened simultaneously, but also because of the extension, affecting the entire Catalan territory. In order to have an overview of the effects of the storm in Catalonia, the Institut Cartogràfic i Geològic of Catalonia has carried out a quick response report (González et. Al., 2020), which has consisted of an inventory of the geomorphological impact and its consequences. The work carried out includes the production of post-event orthoimages of the coastal strip and some fluvial courses, a post-event field survey during the days immediately after, and a compilation of the information published in the media between 01/20/2020 and 02/18/2020. Also, a data collection campaign through online forms sent by email has been carried out, which provides more information of the sea gale effects, and validates and complete the preliminary inventory of slope movements. Thus, an inventory of slope movements has been obtained with a total of 352 documented landslides throughout the Catalan territory. In addition, a geomorphological mapping with the changes associated to river dynamics has been carried out, in two of the most affected sectors in NE Catalonia: the lower section of the Tordera river and the lower section of Ter river. This 1: 5 000 scale cartography, identify geomorphological elements from fluvial dynamics (active fluvial channels during the flood, active flood plain, erosion scarps of river banks, flow direction lines) and from coastal dynamics (washoverfans, coastal erosion and new creation stream-mouth bars). Finally, based on the analysis of the data collected, an estimate has been made of the impact that the storm Gloria has had on the territory, and how it has affected the different municipalities, in terms of damages and economic losses. The results of this quick response report allow (i) to have a geomorphological record of the storm extent in the short term, (ii) to provide basic information for the management and recovery of river areas, and (iii) to propose new strategies for geological risk management, among others.
How to cite: González, M., Micheo, M. J., Pinyol, J., Carles, M. R., Pi, E., Vila, M., and Roca, A.: The effects of the storm Gloria in Catalonia: The value of quick-response geological inventories as a tool for risk management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2499, https://doi.org/10.5194/egusphere-egu21-2499, 2021.
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The storm Gloria was an exceptional episode of east storm occurred in the north and east of Spain from Sunday 19th to Thursday 23rd of January 2020. The impact was especially strong in the Mediterranean coast, causing the overflow of some rivers, abundant slope movements, cuts in the road and rail network, isolation of populations, and huge damage on the coastline. It was classified as historical, not only because of the multiplicity of phenomena (wind, rain, snow, and waves) that happened simultaneously, but also because of the extension, affecting the entire Catalan territory. In order to have an overview of the effects of the storm in Catalonia, the Institut Cartogràfic i Geològic of Catalonia has carried out a quick response report (González et. Al., 2020), which has consisted of an inventory of the geomorphological impact and its consequences. The work carried out includes the production of post-event orthoimages of the coastal strip and some fluvial courses, a post-event field survey during the days immediately after, and a compilation of the information published in the media between 01/20/2020 and 02/18/2020. Also, a data collection campaign through online forms sent by email has been carried out, which provides more information of the sea gale effects, and validates and complete the preliminary inventory of slope movements. Thus, an inventory of slope movements has been obtained with a total of 352 documented landslides throughout the Catalan territory. In addition, a geomorphological mapping with the changes associated to river dynamics has been carried out, in two of the most affected sectors in NE Catalonia: the lower section of the Tordera river and the lower section of Ter river. This 1: 5 000 scale cartography, identify geomorphological elements from fluvial dynamics (active fluvial channels during the flood, active flood plain, erosion scarps of river banks, flow direction lines) and from coastal dynamics (washoverfans, coastal erosion and new creation stream-mouth bars). Finally, based on the analysis of the data collected, an estimate has been made of the impact that the storm Gloria has had on the territory, and how it has affected the different municipalities, in terms of damages and economic losses. The results of this quick response report allow (i) to have a geomorphological record of the storm extent in the short term, (ii) to provide basic information for the management and recovery of river areas, and (iii) to propose new strategies for geological risk management, among others.
How to cite: González, M., Micheo, M. J., Pinyol, J., Carles, M. R., Pi, E., Vila, M., and Roca, A.: The effects of the storm Gloria in Catalonia: The value of quick-response geological inventories as a tool for risk management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2499, https://doi.org/10.5194/egusphere-egu21-2499, 2021.
GM4.15 – Erosion, Weathering, and Sediment Transport in Mountain Landscapes
EGU21-2007 | vPICO presentations | GM4.15
Spatial and Temporal Variability in Suspended Sediment Yield for two tropical mountain catchments draining into the Southern Ethiopian Rift Valley.Tilahun Alemayehu Kasaye, Guchie Gulie, Margaret Chen, and Gert Verstraeten
Complex terrain tropical mountainous catchments are typically characterized by intense rainfall events, flash floods and high erosion rates with large variability over short distances. Whilst these processes are known, little quantitative information on the spatiotemporal variability in suspended sediment yield (SY) of African tropical mountain environments is available. Here, we provide such data for two catchments in the Southern Ethiopian Rift Valley characterised by annual rainfall of 700 to 1000 mm concentrated in the rainy season from April to October. In total 6 gauging stations were installed along Elgo (298 km²) and Shafe (191 km²) rivers which have their headwaters in the Gamo Highlands (max. elevation 3500 m) and run into the rift valley lakes of Chamo (1107 m) and Abaya (1169 m), respectively. For each river, a gauging station was installed where they enter the lakes as well as at the apex of extensive alluvial fans that developed in the graben lowlands, enabling to quantify the buffering capacity of the fans. For Elgo, two extra stations in the highlands were installed to monitor downstream changes in SY. At all stations, discharge (Q) was measured at 10-min resolution using a pressure diver during in 2018-2019. Additionally, 1542 samples were taken to measure the suspended sediment concentration (SSC), and these were used to establish sediment rating curves in order to calculate total suspended SY from the continuous discharge records. Observed SSC varies between 0.04 and 111.48 g/l for discharges ranging between 0.005 and 227.20 m³/s, whereas annual SY varies between 1133 and 6373 t/km²/year. Both SSC and SY values are in line with those reported for other highland rivers in Ethiopia and in line with SY values for other tropical mountain catchments in the world. A strong temporal variability in SSC and SY is observed and can be explained mainly due to changes in hillslope sediment supply throughout the seasons. Peak sediment transport is mostly concentrated in the first two months (May to June) of the rainy seasons accounting for about 60% of the total SY of the season. At the start of the rainy season, topsoil is loose because of tillage operations that prepare the soil for cultivation. Furthermore, vegetation cover is at its lowest value. Throughout the rainy season, vegetation cover increases and hence soil erosion and sediment yield declines. Comparing the SY of the various gauging stations shows that total sediment load increases in downstream direction, up to the apex of the alluvial fans. Whereas agricultural top soil erosion is most important in the upper parts of the landscape, gully erosion and river bank erosion also contribute much sediment in downstream direction. However, total suspended SY delivered to the lake-based gauging stations is 32 to 53% lower compared to the total suspended SY measured at the gauging station situated near the apex of the alluvial fans. This implies that a significant proportion of the sediment load is buffered by the fans and points to an important dis-connectivity between eroding mountains and rift valley lakes.
How to cite: Alemayehu Kasaye, T., Gulie, G., Chen, M., and Verstraeten, G.: Spatial and Temporal Variability in Suspended Sediment Yield for two tropical mountain catchments draining into the Southern Ethiopian Rift Valley., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2007, https://doi.org/10.5194/egusphere-egu21-2007, 2021.
Complex terrain tropical mountainous catchments are typically characterized by intense rainfall events, flash floods and high erosion rates with large variability over short distances. Whilst these processes are known, little quantitative information on the spatiotemporal variability in suspended sediment yield (SY) of African tropical mountain environments is available. Here, we provide such data for two catchments in the Southern Ethiopian Rift Valley characterised by annual rainfall of 700 to 1000 mm concentrated in the rainy season from April to October. In total 6 gauging stations were installed along Elgo (298 km²) and Shafe (191 km²) rivers which have their headwaters in the Gamo Highlands (max. elevation 3500 m) and run into the rift valley lakes of Chamo (1107 m) and Abaya (1169 m), respectively. For each river, a gauging station was installed where they enter the lakes as well as at the apex of extensive alluvial fans that developed in the graben lowlands, enabling to quantify the buffering capacity of the fans. For Elgo, two extra stations in the highlands were installed to monitor downstream changes in SY. At all stations, discharge (Q) was measured at 10-min resolution using a pressure diver during in 2018-2019. Additionally, 1542 samples were taken to measure the suspended sediment concentration (SSC), and these were used to establish sediment rating curves in order to calculate total suspended SY from the continuous discharge records. Observed SSC varies between 0.04 and 111.48 g/l for discharges ranging between 0.005 and 227.20 m³/s, whereas annual SY varies between 1133 and 6373 t/km²/year. Both SSC and SY values are in line with those reported for other highland rivers in Ethiopia and in line with SY values for other tropical mountain catchments in the world. A strong temporal variability in SSC and SY is observed and can be explained mainly due to changes in hillslope sediment supply throughout the seasons. Peak sediment transport is mostly concentrated in the first two months (May to June) of the rainy seasons accounting for about 60% of the total SY of the season. At the start of the rainy season, topsoil is loose because of tillage operations that prepare the soil for cultivation. Furthermore, vegetation cover is at its lowest value. Throughout the rainy season, vegetation cover increases and hence soil erosion and sediment yield declines. Comparing the SY of the various gauging stations shows that total sediment load increases in downstream direction, up to the apex of the alluvial fans. Whereas agricultural top soil erosion is most important in the upper parts of the landscape, gully erosion and river bank erosion also contribute much sediment in downstream direction. However, total suspended SY delivered to the lake-based gauging stations is 32 to 53% lower compared to the total suspended SY measured at the gauging station situated near the apex of the alluvial fans. This implies that a significant proportion of the sediment load is buffered by the fans and points to an important dis-connectivity between eroding mountains and rift valley lakes.
How to cite: Alemayehu Kasaye, T., Gulie, G., Chen, M., and Verstraeten, G.: Spatial and Temporal Variability in Suspended Sediment Yield for two tropical mountain catchments draining into the Southern Ethiopian Rift Valley., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2007, https://doi.org/10.5194/egusphere-egu21-2007, 2021.
EGU21-16067 | vPICO presentations | GM4.15
How does the suspended sediment yield change in the North Caucasus during the Anthropocene?Anatoly Tsyplenkov and Valentin Golosov
Processes linked to climate change and intensified anthropogenic pressure influence the environment, the hydrology and by extent the denudation processes in the Caucasus mountain belt. Quantitative assessments of sediment fluxes and their temporal evolution in this mountain region required for various environmental and engineering purposes, including the planning and maintenance of water reservoirs and other structures. This paper presents an analysis of the suspended sediment load data from almost 40 gauging stations located in the mountain part of the Terek river basin (North Caucasus, Russia). The collected dataset include river basins with various glacier cover (0%-20%) and human impact. All river basins show consistent decreases in mean annual suspended sediment load (SSL, kg/s) up to 1–2% per year during 1925–2018 (according to Mann-Kendall test). The cumulative deviation curve of the mean annual SSL for the last 60 years indicates that SSL has increased significantly from ca. 1970-1980 to 1990-2000 for the most North Caucasus rivers. However, after the 2000s mean annual values of the SSL show a stable decrease in all observed rivers. Possible mechanisms of observed changes are discussed. This study provides the data on climate-related changes in the sediment yield for a previously not investigated region.
How to cite: Tsyplenkov, A. and Golosov, V.: How does the suspended sediment yield change in the North Caucasus during the Anthropocene?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16067, https://doi.org/10.5194/egusphere-egu21-16067, 2021.
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Processes linked to climate change and intensified anthropogenic pressure influence the environment, the hydrology and by extent the denudation processes in the Caucasus mountain belt. Quantitative assessments of sediment fluxes and their temporal evolution in this mountain region required for various environmental and engineering purposes, including the planning and maintenance of water reservoirs and other structures. This paper presents an analysis of the suspended sediment load data from almost 40 gauging stations located in the mountain part of the Terek river basin (North Caucasus, Russia). The collected dataset include river basins with various glacier cover (0%-20%) and human impact. All river basins show consistent decreases in mean annual suspended sediment load (SSL, kg/s) up to 1–2% per year during 1925–2018 (according to Mann-Kendall test). The cumulative deviation curve of the mean annual SSL for the last 60 years indicates that SSL has increased significantly from ca. 1970-1980 to 1990-2000 for the most North Caucasus rivers. However, after the 2000s mean annual values of the SSL show a stable decrease in all observed rivers. Possible mechanisms of observed changes are discussed. This study provides the data on climate-related changes in the sediment yield for a previously not investigated region.
How to cite: Tsyplenkov, A. and Golosov, V.: How does the suspended sediment yield change in the North Caucasus during the Anthropocene?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16067, https://doi.org/10.5194/egusphere-egu21-16067, 2021.
EGU21-12062 | vPICO presentations | GM4.15 | Highlight
Quantitative evaluation of human and climate forcing on erosion over the last 2000 years in northern ItalyWilliam Rapuc, Julien Bouchez, Pierre Sabatier, Kim Genuite, Jérôme Poulenard, Jérôme Gaillardet, and Fabien Arnaud
Soil erosion is one of the main environmental threats affecting the Critical Zone (CZ) and thus ecosystem services and human societies. This represents an emerging concern considered as one of the geosciences/society central issues. Through time, the physical erosion is linked to both, precipitation amounts induced by climate fluctuations, and the evolution of vegetation cover and land-use. Understanding these forcing factors is key to improve our management of this resource, especially in mountainous areas where CZ erosion is highest. Only studies combining large spatial and temporal approaches allow to assess the effect of these forcing factors on soil erosion rates. Here, we apply a retrospective approach based on lake sediments to reconstruct the long-term evolution of erosion in Alpine landscapes. Lake Iseo located in northern Italy at the downstream end of the Val Camonica acts as a natural sink for all the erosion products from a large watershed (1777 km²). This watershed is representative of the southern Italian Alps, where Holocene human activity and climate fluctuations are well known. The approach combines a source-to-sink method, using isotopic geochemistry (εNd, 87Sr/86Sr), with a multiproxy study of a lacustrine sediment section covering the last 2000 years. The applied methodology allows us to disentangle the role of climate and land use as erosion forcing factors through their differential impact on the various rock types present in the watershed. Indeed, the high-altitudinal part of the Val Camonica, the erosion of which is dominated by glacier advances and retreats, presents isotopic signature different from those of the sedimentary rocks located in the lower part of the watershed, where both human activities and precipitations impacted erosion through time. A chronicle of glacial erosion over the last 2000 years was produced. Once the climatic trend was highlighted, the signal of erosion of sedimentary rocks was investigated to understand the influence of humans. From the Roman Period to the Industrial Age several period of deforestation and increased human pressure were documented. The past sediment yield inferred for sedimentary rocks exhibits the highest values (> 80 t.km-2.yr-1) at periods of intense human practices. Hence, since the late Roman Period, human activities seem to be the dominant forcing factor of the physical erosion in mountainous environment of northern Italy. This study presents the first reconstruction through time of sediment yield derived from lake sediment associated with sediment sources identification and quantitative evaluation of the erosion forcing factors.
How to cite: Rapuc, W., Bouchez, J., Sabatier, P., Genuite, K., Poulenard, J., Gaillardet, J., and Arnaud, F.: Quantitative evaluation of human and climate forcing on erosion over the last 2000 years in northern Italy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12062, https://doi.org/10.5194/egusphere-egu21-12062, 2021.
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Soil erosion is one of the main environmental threats affecting the Critical Zone (CZ) and thus ecosystem services and human societies. This represents an emerging concern considered as one of the geosciences/society central issues. Through time, the physical erosion is linked to both, precipitation amounts induced by climate fluctuations, and the evolution of vegetation cover and land-use. Understanding these forcing factors is key to improve our management of this resource, especially in mountainous areas where CZ erosion is highest. Only studies combining large spatial and temporal approaches allow to assess the effect of these forcing factors on soil erosion rates. Here, we apply a retrospective approach based on lake sediments to reconstruct the long-term evolution of erosion in Alpine landscapes. Lake Iseo located in northern Italy at the downstream end of the Val Camonica acts as a natural sink for all the erosion products from a large watershed (1777 km²). This watershed is representative of the southern Italian Alps, where Holocene human activity and climate fluctuations are well known. The approach combines a source-to-sink method, using isotopic geochemistry (εNd, 87Sr/86Sr), with a multiproxy study of a lacustrine sediment section covering the last 2000 years. The applied methodology allows us to disentangle the role of climate and land use as erosion forcing factors through their differential impact on the various rock types present in the watershed. Indeed, the high-altitudinal part of the Val Camonica, the erosion of which is dominated by glacier advances and retreats, presents isotopic signature different from those of the sedimentary rocks located in the lower part of the watershed, where both human activities and precipitations impacted erosion through time. A chronicle of glacial erosion over the last 2000 years was produced. Once the climatic trend was highlighted, the signal of erosion of sedimentary rocks was investigated to understand the influence of humans. From the Roman Period to the Industrial Age several period of deforestation and increased human pressure were documented. The past sediment yield inferred for sedimentary rocks exhibits the highest values (> 80 t.km-2.yr-1) at periods of intense human practices. Hence, since the late Roman Period, human activities seem to be the dominant forcing factor of the physical erosion in mountainous environment of northern Italy. This study presents the first reconstruction through time of sediment yield derived from lake sediment associated with sediment sources identification and quantitative evaluation of the erosion forcing factors.
How to cite: Rapuc, W., Bouchez, J., Sabatier, P., Genuite, K., Poulenard, J., Gaillardet, J., and Arnaud, F.: Quantitative evaluation of human and climate forcing on erosion over the last 2000 years in northern Italy, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12062, https://doi.org/10.5194/egusphere-egu21-12062, 2021.
EGU21-2913 | vPICO presentations | GM4.15
Sediment export in marly badland catchments controlled by frost cracking intensity, Draix-Bléone CZO, SE FranceColine Ariagno, Caroline Le Bouteiller, Peter Van der Beek, and Sébastien Klotz
At the interface between the lithosphere and the atmosphere, the critical zone records the complex interactions between erosion, climate, geologic substrate and life, and can be directly monitored. The sparsely vegetated, steep marly badland catchments of the Draix-Bléone Critical Zone Observatory (CZO), SE France are characterised by high quantities of exported sediment and rapid morphologic changes. Characterizing and understanding the physical weathering processes in this area are key to predict the temporal variability of regolith production and sediment flux, as well as their evolution under changing climate conditions.
Long data records collected in the Draix-Bléone CZO allow analysing long-term regolith dynamics and climatic control on sediment export. Although widely accepted as the first order control, rainfall variability does not fully explain the observed yearly variability in sediment export, suggesting that regolith production and its controls may contribute to the observed pattern of sediment export. Within the several factors that can influence marls weathering (soil moisture, density, chemical weathering), this study focuses on continuous temperature data, recorded at different locations over multiple years, and aims to highlight the role of frost cracking in regolith production. Several proxies for frost cracking intensity have been calculated from these data and compared to the sediment export anomalies, with careful consideration of field data quality. Our initial results suggest that frost-cracking processes have a significant impact on catchment sediment response and should be taken into account when building a predictive model of sediment export from these catchments under a changing climate.
How to cite: Ariagno, C., Le Bouteiller, C., Van der Beek, P., and Klotz, S.: Sediment export in marly badland catchments controlled by frost cracking intensity, Draix-Bléone CZO, SE France, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2913, https://doi.org/10.5194/egusphere-egu21-2913, 2021.
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At the interface between the lithosphere and the atmosphere, the critical zone records the complex interactions between erosion, climate, geologic substrate and life, and can be directly monitored. The sparsely vegetated, steep marly badland catchments of the Draix-Bléone Critical Zone Observatory (CZO), SE France are characterised by high quantities of exported sediment and rapid morphologic changes. Characterizing and understanding the physical weathering processes in this area are key to predict the temporal variability of regolith production and sediment flux, as well as their evolution under changing climate conditions.
Long data records collected in the Draix-Bléone CZO allow analysing long-term regolith dynamics and climatic control on sediment export. Although widely accepted as the first order control, rainfall variability does not fully explain the observed yearly variability in sediment export, suggesting that regolith production and its controls may contribute to the observed pattern of sediment export. Within the several factors that can influence marls weathering (soil moisture, density, chemical weathering), this study focuses on continuous temperature data, recorded at different locations over multiple years, and aims to highlight the role of frost cracking in regolith production. Several proxies for frost cracking intensity have been calculated from these data and compared to the sediment export anomalies, with careful consideration of field data quality. Our initial results suggest that frost-cracking processes have a significant impact on catchment sediment response and should be taken into account when building a predictive model of sediment export from these catchments under a changing climate.
How to cite: Ariagno, C., Le Bouteiller, C., Van der Beek, P., and Klotz, S.: Sediment export in marly badland catchments controlled by frost cracking intensity, Draix-Bléone CZO, SE France, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2913, https://doi.org/10.5194/egusphere-egu21-2913, 2021.
EGU21-3121 | vPICO presentations | GM4.15
Topographic controls on frost and thermal weathering processes and implications for rockwall erosionDaniel Draebing and Till Mayer
Mechanical weathering by freezing and thermal processes are influenced by climate. Topography modulates this climatic influence due to altitudinal decrease of temperature, modifying insolation due to rockwall aspects and insulation by snow cover. In this study, we (i) quantify rock fracture damage in the field, (ii) monitor rock surface temperature and snow cover, (iii) model frost weathering processes, (iv) quantify fracture kinematics and (v) assess how these processes contribute to rockwall erosion. For this purpose, we conducted measurements on rockwalls with different aspects along an altitudinal gradient ranging from 2,500 to 3,200 m in the Hungerli Valley, Swiss Alps, between 2016 and 2019.
(i) The geology of the Hungerli Valley comprises schisty quartz slate with inclusions of aplite and amphibolite. We conducted Rock Mass Strength (RMS) measurements and used fracture spacing and uniaxial compressive strength (UCS) measurements as proxies for mechanical weathering. RMS ranges from 62 to 77 for schisty quartz slate rockwalls, up to 73 for aplite and 74 for amphibolite. Fracture spacing and UCS reflect lithological differences of the catchment area suggesting a geological control on weathering efficacy.
(ii) Rock surface temperatures (RST) were monitored using temperature loggers. RST decreases with elevation from 2,500 to 2,900 m, however, increases again at 3,150 m potentially due to higher insolation on ridges. Snow cover duration shows a similar altitudinal trend. Due to aspect, RSTs are 2 to 4 °C warmer on south facing rockwalls with significant shorter snow cover period.
(iii) We used measured RST to drive frost cracking models by Walder and Hallet (1985) and Rempel et al. (2016). Both models show near surface frost weathering at lower altitudes, which should results in lower UCS. The models show significantly higher frost cracking at higher altitudes with peaks at rock depths between 0.5 and 2 m suggesting a higher fracture spacing.
(iv) Rockwalls between 2,500 and 2,900 m were equipped with crackmeters and show higher daily temperature changes and crack deformation at lower altitudes or south facing aspects due to higher insolation compared to higher located rockwalls. Seasonal crack displacement depends on dipping of monitored blocks and is controlled by both thermal and cryogenic processes (Draebing, 2020).
(v) In summary, low-altitudinal rockwalls show a higher weathering at the surface due to a combination of thermal processes and near surface frost weathering resulting in release of small blocks and lower erosion rates. In contrast, rockwalls at higher altitudes reveal higher seasonal thermal changes propagating deeper into the rock in combination with frost cracking in higher depths, which results in larger blocks and higher erosion rates.
Draebing, D.: Identification of rock and fracture kinematics in high Alpine rockwalls under the influence of altitude, Earth Surf. Dynam. Discuss., 1-31, 2020.
Rempel, A. W., Marshall, J. A., & Roering, J. J.: Modeling relative frost weathering rates at geomorphic scales. Earth and Planetary Science Letters, 453, 87-95, 2016.
Walder, J., and Hallet, B.: A Theoretical-model of the fracture of rock during freezing, Geological Society of America Bulletin, 96, 336-346, 1985.
How to cite: Draebing, D. and Mayer, T.: Topographic controls on frost and thermal weathering processes and implications for rockwall erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3121, https://doi.org/10.5194/egusphere-egu21-3121, 2021.
Mechanical weathering by freezing and thermal processes are influenced by climate. Topography modulates this climatic influence due to altitudinal decrease of temperature, modifying insolation due to rockwall aspects and insulation by snow cover. In this study, we (i) quantify rock fracture damage in the field, (ii) monitor rock surface temperature and snow cover, (iii) model frost weathering processes, (iv) quantify fracture kinematics and (v) assess how these processes contribute to rockwall erosion. For this purpose, we conducted measurements on rockwalls with different aspects along an altitudinal gradient ranging from 2,500 to 3,200 m in the Hungerli Valley, Swiss Alps, between 2016 and 2019.
(i) The geology of the Hungerli Valley comprises schisty quartz slate with inclusions of aplite and amphibolite. We conducted Rock Mass Strength (RMS) measurements and used fracture spacing and uniaxial compressive strength (UCS) measurements as proxies for mechanical weathering. RMS ranges from 62 to 77 for schisty quartz slate rockwalls, up to 73 for aplite and 74 for amphibolite. Fracture spacing and UCS reflect lithological differences of the catchment area suggesting a geological control on weathering efficacy.
(ii) Rock surface temperatures (RST) were monitored using temperature loggers. RST decreases with elevation from 2,500 to 2,900 m, however, increases again at 3,150 m potentially due to higher insolation on ridges. Snow cover duration shows a similar altitudinal trend. Due to aspect, RSTs are 2 to 4 °C warmer on south facing rockwalls with significant shorter snow cover period.
(iii) We used measured RST to drive frost cracking models by Walder and Hallet (1985) and Rempel et al. (2016). Both models show near surface frost weathering at lower altitudes, which should results in lower UCS. The models show significantly higher frost cracking at higher altitudes with peaks at rock depths between 0.5 and 2 m suggesting a higher fracture spacing.
(iv) Rockwalls between 2,500 and 2,900 m were equipped with crackmeters and show higher daily temperature changes and crack deformation at lower altitudes or south facing aspects due to higher insolation compared to higher located rockwalls. Seasonal crack displacement depends on dipping of monitored blocks and is controlled by both thermal and cryogenic processes (Draebing, 2020).
(v) In summary, low-altitudinal rockwalls show a higher weathering at the surface due to a combination of thermal processes and near surface frost weathering resulting in release of small blocks and lower erosion rates. In contrast, rockwalls at higher altitudes reveal higher seasonal thermal changes propagating deeper into the rock in combination with frost cracking in higher depths, which results in larger blocks and higher erosion rates.
Draebing, D.: Identification of rock and fracture kinematics in high Alpine rockwalls under the influence of altitude, Earth Surf. Dynam. Discuss., 1-31, 2020.
Rempel, A. W., Marshall, J. A., & Roering, J. J.: Modeling relative frost weathering rates at geomorphic scales. Earth and Planetary Science Letters, 453, 87-95, 2016.
Walder, J., and Hallet, B.: A Theoretical-model of the fracture of rock during freezing, Geological Society of America Bulletin, 96, 336-346, 1985.
How to cite: Draebing, D. and Mayer, T.: Topographic controls on frost and thermal weathering processes and implications for rockwall erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3121, https://doi.org/10.5194/egusphere-egu21-3121, 2021.
EGU21-528 | vPICO presentations | GM4.15
Cooling joints of granite as a structural cause of the tors and boulder fields of graniteMasahiro Chigira and Yasuto Hirata
Typical cooling joints of granite have been believed to be orthogonal, and characteristic topography of granitic rocks like tors and boulder fields are interpreted in combination with the cooling joints and weathering. However, most of the previous studies were performed by the observation on the ground, and the 3D observation of cooling joints and the topographic features was not sufficient. We observed tors and boulder fields of granitic rocks using UAV and 3D modelling and found that columnar joints are typical for the granite that forms tors and that boulder fields are the accumulations of rock columns as well as boulders made by the spheroidal weathering of rock columns. Tors we observed were Mt. Kinabalu of Borneo, Mt. Mizugaki, Mt. Jizo, Mt. Gozaisho, Mt. Konze and 5 other locations in Japan. We observed that tors consist of polygonal rock columns with undulating joints, more irregularly shaped than the columnar joints of volcanic rocks. The cross-sectional areas of rock columns varied from 1 to 130 m^2, much larger than typical rock columns of volcanic rocks. The rock columns of granite are typically polygonal dipyramids, of which shapes may be dependent on the cooling history of granite. Boulder fields we observed was the Kui boulder fields in Hiroshima. We found that the boulder field is the accumulation of prismatic rock columns as well as rounded rock boulders. The prismatic rock columns had basal cross-sectional areas of 0.8 m^2 on average. The rock columns had chamfering cracks at corners, which are assumed to be made during cooling and to form preliminary outlines of core stones. Core stones had surface crusts or rindlets, which exfoliate and leave more rounded core stones.
Rainstorm-induced landslides of weathered granite reflect weathering styles of granite: Landslides that occurred recently in Japan had three types, landslides of loosened layers of decomposed granite (or micro-sheeted granite), landslides of core-stone bearing materials, and landslides of saprolite. Landslides with core-stones were particularly destructive because of their inertia. Potential sites of such landslides could be predicted using columnar joints in fresh rocks as a clue.
How to cite: Chigira, M. and Hirata, Y.: Cooling joints of granite as a structural cause of the tors and boulder fields of granite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-528, https://doi.org/10.5194/egusphere-egu21-528, 2021.
Typical cooling joints of granite have been believed to be orthogonal, and characteristic topography of granitic rocks like tors and boulder fields are interpreted in combination with the cooling joints and weathering. However, most of the previous studies were performed by the observation on the ground, and the 3D observation of cooling joints and the topographic features was not sufficient. We observed tors and boulder fields of granitic rocks using UAV and 3D modelling and found that columnar joints are typical for the granite that forms tors and that boulder fields are the accumulations of rock columns as well as boulders made by the spheroidal weathering of rock columns. Tors we observed were Mt. Kinabalu of Borneo, Mt. Mizugaki, Mt. Jizo, Mt. Gozaisho, Mt. Konze and 5 other locations in Japan. We observed that tors consist of polygonal rock columns with undulating joints, more irregularly shaped than the columnar joints of volcanic rocks. The cross-sectional areas of rock columns varied from 1 to 130 m^2, much larger than typical rock columns of volcanic rocks. The rock columns of granite are typically polygonal dipyramids, of which shapes may be dependent on the cooling history of granite. Boulder fields we observed was the Kui boulder fields in Hiroshima. We found that the boulder field is the accumulation of prismatic rock columns as well as rounded rock boulders. The prismatic rock columns had basal cross-sectional areas of 0.8 m^2 on average. The rock columns had chamfering cracks at corners, which are assumed to be made during cooling and to form preliminary outlines of core stones. Core stones had surface crusts or rindlets, which exfoliate and leave more rounded core stones.
Rainstorm-induced landslides of weathered granite reflect weathering styles of granite: Landslides that occurred recently in Japan had three types, landslides of loosened layers of decomposed granite (or micro-sheeted granite), landslides of core-stone bearing materials, and landslides of saprolite. Landslides with core-stones were particularly destructive because of their inertia. Potential sites of such landslides could be predicted using columnar joints in fresh rocks as a clue.
How to cite: Chigira, M. and Hirata, Y.: Cooling joints of granite as a structural cause of the tors and boulder fields of granite, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-528, https://doi.org/10.5194/egusphere-egu21-528, 2021.
EGU21-5908 | vPICO presentations | GM4.15
High alpine rock-wall retreat rates over millennia through thermo-cryogenic pre-conditioned rock fall (Mt. Eiger, Switzerland)David Mair, Alessandro Lechmann, Romain Delunel, Serdar Yeşilyurt, Dmitry Tikhomirov, Christof Vockenhuber, Marcus Christl, Naki Akçar, and Fritz Schlunegger
Rock fall processes of various size and magnitude control retreat rates of high alpine rock-walls. For millennial time scales, these retreat rates can be quantified in-situ from concentrations of cosmogenic nuclides along bedrock depth profiles (Mair et al., 2019). We measured cosmogenic 36Cl and 10Be along several such profiles at Mt Eiger in the Central Swiss Alps to study the local rock-wall retreat on this time scale (Mair et al., 2019; 2020). The resulting spatial pattern shows that rock-wall retreat rates are low (0.5 to 0.6 ± 0.1 mm/yr) in the higher region of the NW rock-wall, in contrast to both the lower part of the NW rock-wall and the SE face, where rates are high (1.7 ± 0.4 to 3.5 ± 1.4 mm/yr). We link these retreat rates to differences in local temperature conditions, because the patterns of faults and fractures and the lithology of the bedrock are similar at all sites, and thermo-cryogenic processes are known to weaken the bedrock through fracturing, thereby preconditioning the occurrence of rock fall (e.g., Draebing and Krautblatter, 2019). However, it is still unclear how effective and at which rate individual thermo-cryogenic processes contribute to the preconditioning through fracturing. Therefore, we investigate several processes and estimate the probability of bedrock fracturing through the employment of a theoretical frost-cracking model, which predicts cracking intensity from ice segregation. The model results infer a low efficiency in the higher region of the NW rock-wall, but a relatively high one in the lower section of the NW wall and on the SE rock face of Mt. Eiger. Although the model is rather generic, the results disclose a significant control of temperature conditions on the erosional processes and rates. Furthermore, temperature conditions for the last millennia have been similar to present day conditions, as our reconstructions disclose, therefore the cosmogenic-nuclide-based long-term differences in rock-wall retreat rates predominantly stem from large contrasts in the microclimate between the NW and SE walls of Mt. Eiger. Accordingly, the site-specific differences in microclimate conditions could explain the lower retreat rates in the upper part of the NW rock-wall and the rapid retreat in the SW face and in the lower part of the NW rock face.
References
Draebing, D. and Krautblatter, M.: The Efficacy of Frost Weathering Processes in Alpine Rockwalls, Geophys. Res. Lett., 46, 6516–6524, doi:10.1029/2019GL081981, 2019.
Mair, D., Lechmann, A., Yesilyurt, S., Tikhomirov, D., Delunel, R., Vockenhuber, C., Akçar, N. and Schlunegger, F.: Fast long-term denudation rate of steep alpine headwalls inferred from cosmogenic 36Cl depth profiles, Sci. Rep., 9, 11023, doi:10.1038/s41598-019-46969-0, 2019.
Mair, D., Lechmann, A., Delunel, R., Yeşilyurt, S., Tikhomirov, D., Vockenhuber, C., Christl, M., Akçar, N. and Schlunegger, F.: The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland), Earth Surf. Dyn., 8, 637–659, doi:10.5194/esurf-8-637-2020, 2020.
How to cite: Mair, D., Lechmann, A., Delunel, R., Yeşilyurt, S., Tikhomirov, D., Vockenhuber, C., Christl, M., Akçar, N., and Schlunegger, F.: High alpine rock-wall retreat rates over millennia through thermo-cryogenic pre-conditioned rock fall (Mt. Eiger, Switzerland), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5908, https://doi.org/10.5194/egusphere-egu21-5908, 2021.
Rock fall processes of various size and magnitude control retreat rates of high alpine rock-walls. For millennial time scales, these retreat rates can be quantified in-situ from concentrations of cosmogenic nuclides along bedrock depth profiles (Mair et al., 2019). We measured cosmogenic 36Cl and 10Be along several such profiles at Mt Eiger in the Central Swiss Alps to study the local rock-wall retreat on this time scale (Mair et al., 2019; 2020). The resulting spatial pattern shows that rock-wall retreat rates are low (0.5 to 0.6 ± 0.1 mm/yr) in the higher region of the NW rock-wall, in contrast to both the lower part of the NW rock-wall and the SE face, where rates are high (1.7 ± 0.4 to 3.5 ± 1.4 mm/yr). We link these retreat rates to differences in local temperature conditions, because the patterns of faults and fractures and the lithology of the bedrock are similar at all sites, and thermo-cryogenic processes are known to weaken the bedrock through fracturing, thereby preconditioning the occurrence of rock fall (e.g., Draebing and Krautblatter, 2019). However, it is still unclear how effective and at which rate individual thermo-cryogenic processes contribute to the preconditioning through fracturing. Therefore, we investigate several processes and estimate the probability of bedrock fracturing through the employment of a theoretical frost-cracking model, which predicts cracking intensity from ice segregation. The model results infer a low efficiency in the higher region of the NW rock-wall, but a relatively high one in the lower section of the NW wall and on the SE rock face of Mt. Eiger. Although the model is rather generic, the results disclose a significant control of temperature conditions on the erosional processes and rates. Furthermore, temperature conditions for the last millennia have been similar to present day conditions, as our reconstructions disclose, therefore the cosmogenic-nuclide-based long-term differences in rock-wall retreat rates predominantly stem from large contrasts in the microclimate between the NW and SE walls of Mt. Eiger. Accordingly, the site-specific differences in microclimate conditions could explain the lower retreat rates in the upper part of the NW rock-wall and the rapid retreat in the SW face and in the lower part of the NW rock face.
References
Draebing, D. and Krautblatter, M.: The Efficacy of Frost Weathering Processes in Alpine Rockwalls, Geophys. Res. Lett., 46, 6516–6524, doi:10.1029/2019GL081981, 2019.
Mair, D., Lechmann, A., Yesilyurt, S., Tikhomirov, D., Delunel, R., Vockenhuber, C., Akçar, N. and Schlunegger, F.: Fast long-term denudation rate of steep alpine headwalls inferred from cosmogenic 36Cl depth profiles, Sci. Rep., 9, 11023, doi:10.1038/s41598-019-46969-0, 2019.
Mair, D., Lechmann, A., Delunel, R., Yeşilyurt, S., Tikhomirov, D., Vockenhuber, C., Christl, M., Akçar, N. and Schlunegger, F.: The role of frost cracking in local denudation of steep Alpine rockwalls over millennia (Eiger, Switzerland), Earth Surf. Dyn., 8, 637–659, doi:10.5194/esurf-8-637-2020, 2020.
How to cite: Mair, D., Lechmann, A., Delunel, R., Yeşilyurt, S., Tikhomirov, D., Vockenhuber, C., Christl, M., Akçar, N., and Schlunegger, F.: High alpine rock-wall retreat rates over millennia through thermo-cryogenic pre-conditioned rock fall (Mt. Eiger, Switzerland), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5908, https://doi.org/10.5194/egusphere-egu21-5908, 2021.
EGU21-16253 | vPICO presentations | GM4.15
Impacts of climatic seasonality on weathering of rock-cut structures at Lalibela, EthiopiaBlen Taye and Heather Viles
Weathering of rock-cut structures exposed to the environment is strongly influenced by fluctuations in climatic variables. Both macro and microclimate data are needed to identify key weathering types and rates likely to affect rock-cut structures in a specific region. The aim of this paper is to study the macro and micro climatic conditions affecting the rock-cut churches in Lalibela, Ethiopia to determine how the climate influences weathering at this site. Macro climate data collected over a 26-year period and microclimate data monitored on the north, east, south and west walls at one of the churches in the Lalibela church complex (Bete Mariam) are used to make these assessments. Microclimate data was monitored during the long rains (Kiremt), short rains (Belg) and dry (Bega) seasons in 2018 and 2019. The results showed a high seasonal variation in macro climatic conditions like rainfall and ambient relative humidity. The micro climatic (rock surface) conditions also tended to vary seasonally. The diurnal range of rock surface temperature during Bega varied significantly depending on which cardinal directions the walls were facing, with south and west facing walls having high diurnal thermal ranges. The influence of aspect was less pronounced in Belg and Kiremt, but cloud cover played an important role in varying the range of diurnal thermal and humidity cycles from day to day during these seasons. These climate trends are likely to cause seasonal variations in wetting and drying cycles, deep wetting, increased time of wetness and thermal cycling. These wetting/drying and heating/cooling characteristics affect weathering processes. During Kiremt, biological weathering, salt weathering and clay swelling are more likely to occur than in Belg and Bega. High diurnal thermal ranges in Bega are likely to cause thermal fatigue in this season. This is the first paper to address the macro and micro climatic trends that influence rock weathering at the rock-cut churches in Lalibela. The results of this study also have implications for rock-cut structures in northern Ethiopia having similar environmental conditions as Lalibela.
How to cite: Taye, B. and Viles, H.: Impacts of climatic seasonality on weathering of rock-cut structures at Lalibela, Ethiopia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16253, https://doi.org/10.5194/egusphere-egu21-16253, 2021.
Weathering of rock-cut structures exposed to the environment is strongly influenced by fluctuations in climatic variables. Both macro and microclimate data are needed to identify key weathering types and rates likely to affect rock-cut structures in a specific region. The aim of this paper is to study the macro and micro climatic conditions affecting the rock-cut churches in Lalibela, Ethiopia to determine how the climate influences weathering at this site. Macro climate data collected over a 26-year period and microclimate data monitored on the north, east, south and west walls at one of the churches in the Lalibela church complex (Bete Mariam) are used to make these assessments. Microclimate data was monitored during the long rains (Kiremt), short rains (Belg) and dry (Bega) seasons in 2018 and 2019. The results showed a high seasonal variation in macro climatic conditions like rainfall and ambient relative humidity. The micro climatic (rock surface) conditions also tended to vary seasonally. The diurnal range of rock surface temperature during Bega varied significantly depending on which cardinal directions the walls were facing, with south and west facing walls having high diurnal thermal ranges. The influence of aspect was less pronounced in Belg and Kiremt, but cloud cover played an important role in varying the range of diurnal thermal and humidity cycles from day to day during these seasons. These climate trends are likely to cause seasonal variations in wetting and drying cycles, deep wetting, increased time of wetness and thermal cycling. These wetting/drying and heating/cooling characteristics affect weathering processes. During Kiremt, biological weathering, salt weathering and clay swelling are more likely to occur than in Belg and Bega. High diurnal thermal ranges in Bega are likely to cause thermal fatigue in this season. This is the first paper to address the macro and micro climatic trends that influence rock weathering at the rock-cut churches in Lalibela. The results of this study also have implications for rock-cut structures in northern Ethiopia having similar environmental conditions as Lalibela.
How to cite: Taye, B. and Viles, H.: Impacts of climatic seasonality on weathering of rock-cut structures at Lalibela, Ethiopia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16253, https://doi.org/10.5194/egusphere-egu21-16253, 2021.
EGU21-9221 | vPICO presentations | GM4.15
Co-variation of silicate, carbonate, and sulphide weathering drives release of CO2 with erosionAaron Bufe, Niels Hovius, Robert Emberson, Jeremy K.C. Rugenstein, Albert Galy, Hima J. Hassenruck-Gudipati, and Jui-Ming Chang
The supply of fresh minerals to Earth’s surface by erosion is thought to modulate global climate by removing atmospheric carbon dioxide (CO2) through silicate weathering. In turn, weathering of accessory carbonate and sulfide minerals is a geologically-relevant CO2 source, which may dampen or reverse the effect of silicate weathering on climate. Although these weathering pathways commonly operate side by side, we lack quantitative constraints on their co-evolution across erosion-rate gradients. Using stream-water chemistry across a 3 order-of-magnitude erosion-rate gradient in shales and sandstones of southern Taiwan, here, we demonstrate that silicate, sulfide, and carbonate weathering are linked: Increasing sulfide oxidation generates sulfuric acid and boosts carbonate solubility whereas silicate weathering kinetics remain constant or even decline, perhaps due to buffering of the pH by carbonates. On timescales shorter than marine sulfide compensation, CO2 emission rates from weathering in rapidly-eroding terrain are more than twice the CO2 sequestration rates in slow-eroding terrain. On longer timescales, CO2 emissions are compensated, but CO2 sequestration rates do not increase with erosion, in contrast to assumptions in carbon cycle models. We posit that these patterns are broadly applicable to many Cenozoic mountain ranges that expose dominantly siliciclastic metasediments.
How to cite: Bufe, A., Hovius, N., Emberson, R., Rugenstein, J. K. C., Galy, A., Hassenruck-Gudipati, H. J., and Chang, J.-M.: Co-variation of silicate, carbonate, and sulphide weathering drives release of CO2 with erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9221, https://doi.org/10.5194/egusphere-egu21-9221, 2021.
The supply of fresh minerals to Earth’s surface by erosion is thought to modulate global climate by removing atmospheric carbon dioxide (CO2) through silicate weathering. In turn, weathering of accessory carbonate and sulfide minerals is a geologically-relevant CO2 source, which may dampen or reverse the effect of silicate weathering on climate. Although these weathering pathways commonly operate side by side, we lack quantitative constraints on their co-evolution across erosion-rate gradients. Using stream-water chemistry across a 3 order-of-magnitude erosion-rate gradient in shales and sandstones of southern Taiwan, here, we demonstrate that silicate, sulfide, and carbonate weathering are linked: Increasing sulfide oxidation generates sulfuric acid and boosts carbonate solubility whereas silicate weathering kinetics remain constant or even decline, perhaps due to buffering of the pH by carbonates. On timescales shorter than marine sulfide compensation, CO2 emission rates from weathering in rapidly-eroding terrain are more than twice the CO2 sequestration rates in slow-eroding terrain. On longer timescales, CO2 emissions are compensated, but CO2 sequestration rates do not increase with erosion, in contrast to assumptions in carbon cycle models. We posit that these patterns are broadly applicable to many Cenozoic mountain ranges that expose dominantly siliciclastic metasediments.
How to cite: Bufe, A., Hovius, N., Emberson, R., Rugenstein, J. K. C., Galy, A., Hassenruck-Gudipati, H. J., and Chang, J.-M.: Co-variation of silicate, carbonate, and sulphide weathering drives release of CO2 with erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9221, https://doi.org/10.5194/egusphere-egu21-9221, 2021.
EGU21-14281 | vPICO presentations | GM4.15
Massif-wide denudation of the Vosges Mountains (NE France) inferred from in situ 10Be concentrations in stream sedimentsTimothée Jautzy, Gilles Rixhon, Régis Braucher, Laurent Schmitt, and Aster Team*
The Vosges Mountains in NE France belong to the belt of Variscan massifs located in the foreland of the Alps. Despite its rather limited extension barely reaching 6000 km², this range of low mountains peaking at ~1425 m presents three contrasting primary characteristics. Firstly, a bipartite N-S subdivision can be achieved based on the geological basement: whereas the southern part, traditionally referred to as the crystalline Vosges, is composed of a mosaic of Palaeozoic rocks, including igneous (mostly intrusive and secondarily extrusive), metamorphic, and sedimentary rocks, the northern part is much more homogeneous given its Triassic sandstone cover (“sandstone Vosges”). Secondly, a clear E-W topographic gradient characterises the mountain range. By contrast to the steep hillslopes and elevation drops regularly exceeding 600 m (sometimes reaching 900-1000 m) between the summits and the valley floors on the eastern side (Alsace; south-western border of the Upper Rhine Graben, URG), the western side exhibits more gently-sloping hillslopes along with a longer extension (Lorraine; eastern border of the Parisian Basin). This results from the sharp E-W contrast in Late Cenozoic tectonic activity between sustained subsidence in the URG to the east and weak rock uplift characterising the Parisian Basin to the west. Finally, the imprint left by Quaternary climatic fluctuations yielded a N-S gradient: whereas the southern part (roughly covering 80-90% of the crystalline Vosges) hosted abundant valley glaciers and still bears traces of significant glacial erosion (cirques and U-shaped valleys), the northern part (mostly the sandstone Vosges) was void of ice cover.
In spite of these advantageous characteristics, very little is known about the Quaternary evolution of the massif, in particular regarding the long-term interactions between denudation, lithological control, climatic forcing and tectonic activity. Against this background, this contribution aims to present the first data of long-term, massif-wide denudation. Modern stream sediments from 21 river catchments of different size draining the whole massif were thus sampled for in situ 10Be concentration measurements at the outlet of their mountainous reach. Catchment-wide denudation rates inferred from cosmogenic 10Be will be combined with the analysis of morphometric parameters and structural connectivity resulting from the processing of a high-resolution DEM (5 m). Catchment selection was operated according to the threefold subdivision above: i.e. heterogeneous vs homogenous petrography, tectonically-active eastern side vs “quiescent” western side and glaciated vs unglaciated catchments. We thus test the main hypothesis that the four NE, NW, SE, SW quarters of the Vosges massif shall be characterised by contrasting denudation rates, reflecting the respective role played by the controlling factors on long-term denudation. To our knowledge, this contribution is the first attempt to quantify denudation at the massif scale of a European low mountain range. This is especially relevant as long-term landscape evolution in the Variscan belt, by contrast to the numerous works focusing on denudation in high-mountains ranges (e.g. the Alps), has been regularly disregarded in recent geomorphological studies.
*Georges Aumaître, Didier L. Bourlès and Karim Keddadouche
How to cite: Jautzy, T., Rixhon, G., Braucher, R., Schmitt, L., and Team*, A.: Massif-wide denudation of the Vosges Mountains (NE France) inferred from in situ 10Be concentrations in stream sediments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14281, https://doi.org/10.5194/egusphere-egu21-14281, 2021.
The Vosges Mountains in NE France belong to the belt of Variscan massifs located in the foreland of the Alps. Despite its rather limited extension barely reaching 6000 km², this range of low mountains peaking at ~1425 m presents three contrasting primary characteristics. Firstly, a bipartite N-S subdivision can be achieved based on the geological basement: whereas the southern part, traditionally referred to as the crystalline Vosges, is composed of a mosaic of Palaeozoic rocks, including igneous (mostly intrusive and secondarily extrusive), metamorphic, and sedimentary rocks, the northern part is much more homogeneous given its Triassic sandstone cover (“sandstone Vosges”). Secondly, a clear E-W topographic gradient characterises the mountain range. By contrast to the steep hillslopes and elevation drops regularly exceeding 600 m (sometimes reaching 900-1000 m) between the summits and the valley floors on the eastern side (Alsace; south-western border of the Upper Rhine Graben, URG), the western side exhibits more gently-sloping hillslopes along with a longer extension (Lorraine; eastern border of the Parisian Basin). This results from the sharp E-W contrast in Late Cenozoic tectonic activity between sustained subsidence in the URG to the east and weak rock uplift characterising the Parisian Basin to the west. Finally, the imprint left by Quaternary climatic fluctuations yielded a N-S gradient: whereas the southern part (roughly covering 80-90% of the crystalline Vosges) hosted abundant valley glaciers and still bears traces of significant glacial erosion (cirques and U-shaped valleys), the northern part (mostly the sandstone Vosges) was void of ice cover.
In spite of these advantageous characteristics, very little is known about the Quaternary evolution of the massif, in particular regarding the long-term interactions between denudation, lithological control, climatic forcing and tectonic activity. Against this background, this contribution aims to present the first data of long-term, massif-wide denudation. Modern stream sediments from 21 river catchments of different size draining the whole massif were thus sampled for in situ 10Be concentration measurements at the outlet of their mountainous reach. Catchment-wide denudation rates inferred from cosmogenic 10Be will be combined with the analysis of morphometric parameters and structural connectivity resulting from the processing of a high-resolution DEM (5 m). Catchment selection was operated according to the threefold subdivision above: i.e. heterogeneous vs homogenous petrography, tectonically-active eastern side vs “quiescent” western side and glaciated vs unglaciated catchments. We thus test the main hypothesis that the four NE, NW, SE, SW quarters of the Vosges massif shall be characterised by contrasting denudation rates, reflecting the respective role played by the controlling factors on long-term denudation. To our knowledge, this contribution is the first attempt to quantify denudation at the massif scale of a European low mountain range. This is especially relevant as long-term landscape evolution in the Variscan belt, by contrast to the numerous works focusing on denudation in high-mountains ranges (e.g. the Alps), has been regularly disregarded in recent geomorphological studies.
*Georges Aumaître, Didier L. Bourlès and Karim Keddadouche
How to cite: Jautzy, T., Rixhon, G., Braucher, R., Schmitt, L., and Team*, A.: Massif-wide denudation of the Vosges Mountains (NE France) inferred from in situ 10Be concentrations in stream sediments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14281, https://doi.org/10.5194/egusphere-egu21-14281, 2021.
EGU21-3278 | vPICO presentations | GM4.15
An auspicious landscape: Quantifying transient glacial incision in the Patagonian Andes from ~6 Ma to presentChelsea Willett, Keith Ma, Mark Brandon, Jeremy Hourigan, Elizabeth Christeleit, and David Shuster
The topography, climate, and geology of the central Patagonian Andes provide an auspicious natural laboratory to track long-term rates of erosion in a dynamic mountainous landscape. Herein, we report a mountain-scale record of erosion rates in the central Patagonian Andes from >10 million years (Ma) ago to present, which covers the transition from a fluvial to alpine glaciated landscape. Apatite (U-Th)/He ages of 72 granitic cobbles from alpine glacial deposits show slow erosion before ~6 Ma ago, followed by a two- to three-fold increase in the spatially averaged erosion rate of the source region after the onset of alpine glaciations and a 15-fold increase in the top 25% of the distribution. This transition is followed by a pronounced decrease in erosion rates over the past ~3 Ma. We ascribe the pulse of fast erosion to local deepening and widening of valleys, which are characteristic features of alpine glaciated landscapes. The subsequent decline in local erosion rates may represent a return toward a balance between rock uplift and erosion.
How to cite: Willett, C., Ma, K., Brandon, M., Hourigan, J., Christeleit, E., and Shuster, D.: An auspicious landscape: Quantifying transient glacial incision in the Patagonian Andes from ~6 Ma to present, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3278, https://doi.org/10.5194/egusphere-egu21-3278, 2021.
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The topography, climate, and geology of the central Patagonian Andes provide an auspicious natural laboratory to track long-term rates of erosion in a dynamic mountainous landscape. Herein, we report a mountain-scale record of erosion rates in the central Patagonian Andes from >10 million years (Ma) ago to present, which covers the transition from a fluvial to alpine glaciated landscape. Apatite (U-Th)/He ages of 72 granitic cobbles from alpine glacial deposits show slow erosion before ~6 Ma ago, followed by a two- to three-fold increase in the spatially averaged erosion rate of the source region after the onset of alpine glaciations and a 15-fold increase in the top 25% of the distribution. This transition is followed by a pronounced decrease in erosion rates over the past ~3 Ma. We ascribe the pulse of fast erosion to local deepening and widening of valleys, which are characteristic features of alpine glaciated landscapes. The subsequent decline in local erosion rates may represent a return toward a balance between rock uplift and erosion.
How to cite: Willett, C., Ma, K., Brandon, M., Hourigan, J., Christeleit, E., and Shuster, D.: An auspicious landscape: Quantifying transient glacial incision in the Patagonian Andes from ~6 Ma to present, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3278, https://doi.org/10.5194/egusphere-egu21-3278, 2021.
EGU21-6571 * | vPICO presentations | GM4.15 | Highlight
Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climateDuna Roda-Boluda, Taylor Schildgen, Hella Wittmann-Oelze, Stefanie Tofelde, Aaron Bufe, Jeff Prancevic, and Niels Hovius
The Southern Alps of New Zealand are the expression of the oblique convergence between the Pacific and Australian plates, which move at a relative velocity of nearly 40 mm/yr. This convergence is accommodated by the range-bounding Alpine Fault, with a strike-slip component of ~30-40 mm/yr, and a shortening component normal to the fault of ~8-10 mm/yr. While strike-slip rates seem to be fairly constant along the Alpine Fault, throw rates appear to vary considerably, and whether the locus of maximum exhumation is located near the fault, at the main drainage divide, or part-way between, is still debated. These uncertainties stem from very limited data characterizing vertical deformation rates along and across the Southern Alps. Thermochronology has constrained the Southern Alps exhumation history since the Miocene, but Quaternary exhumation is hard to resolve precisely due to the very high exhumation rates. Likewise, GPS surveys estimate a vertical uplift of ~5 mm/yr, but integrate only over ~10 yr timescales and are restricted to one transect across the range.
To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new 10Be catchment-averaged erosion rates from 20 catchments along the western side of the range. Catchment-averaged erosion rates span an order of magnitude, between ~0.8 and >10 mm/yr, but we find that erosion rates of >10 mm/yr, a value often quoted in the literature as representative for the entire range, are very localized. Moreover, erosion rates decrease sharply north of the intersection with the Marlborough Fault System, suggesting substantial slip partitioning. These 10Be catchment-averaged erosion rates integrate, on average, over the last ~300 yrs. Considering that the last earthquake on the Alpine Fault was in 1717, these rates are representative of inter-seismic erosion. Lake sedimentation rates and coseismic landslide modelling suggest that long-term (~103 yrs) erosion rates over a full seismic cycle could be ~40% greater than our inter-seismic erosion rates. If we assume steady state topography, such a scaling of our 10Be erosion rate estimates can be used to estimate rock uplift rates in the Southern Alps. Finally, we find that erosion, and hence potentially exhumation, does not seem to be localized at a particular distance from the fault, as some tectonic and provenance studies have suggested. Instead, we find that superimposed on the primary tectonic control, there is an elevation/temperature control on erosion rates, which is probably transient and related to frost-cracking and glacial retreat.
Our results highlight the potential for 10Be catchment-averaged erosion rates to provide insights into the magnitude and distribution of tectonic deformation rates, and the limitations that arise from transient erosion controls related to the seismic cycle and climate-modulated surface processes.
How to cite: Roda-Boluda, D., Schildgen, T., Wittmann-Oelze, H., Tofelde, S., Bufe, A., Prancevic, J., and Hovius, N.: Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6571, https://doi.org/10.5194/egusphere-egu21-6571, 2021.
The Southern Alps of New Zealand are the expression of the oblique convergence between the Pacific and Australian plates, which move at a relative velocity of nearly 40 mm/yr. This convergence is accommodated by the range-bounding Alpine Fault, with a strike-slip component of ~30-40 mm/yr, and a shortening component normal to the fault of ~8-10 mm/yr. While strike-slip rates seem to be fairly constant along the Alpine Fault, throw rates appear to vary considerably, and whether the locus of maximum exhumation is located near the fault, at the main drainage divide, or part-way between, is still debated. These uncertainties stem from very limited data characterizing vertical deformation rates along and across the Southern Alps. Thermochronology has constrained the Southern Alps exhumation history since the Miocene, but Quaternary exhumation is hard to resolve precisely due to the very high exhumation rates. Likewise, GPS surveys estimate a vertical uplift of ~5 mm/yr, but integrate only over ~10 yr timescales and are restricted to one transect across the range.
To obtain insights into the Quaternary distribution and rates of exhumation of the western Southern Alps, we use new 10Be catchment-averaged erosion rates from 20 catchments along the western side of the range. Catchment-averaged erosion rates span an order of magnitude, between ~0.8 and >10 mm/yr, but we find that erosion rates of >10 mm/yr, a value often quoted in the literature as representative for the entire range, are very localized. Moreover, erosion rates decrease sharply north of the intersection with the Marlborough Fault System, suggesting substantial slip partitioning. These 10Be catchment-averaged erosion rates integrate, on average, over the last ~300 yrs. Considering that the last earthquake on the Alpine Fault was in 1717, these rates are representative of inter-seismic erosion. Lake sedimentation rates and coseismic landslide modelling suggest that long-term (~103 yrs) erosion rates over a full seismic cycle could be ~40% greater than our inter-seismic erosion rates. If we assume steady state topography, such a scaling of our 10Be erosion rate estimates can be used to estimate rock uplift rates in the Southern Alps. Finally, we find that erosion, and hence potentially exhumation, does not seem to be localized at a particular distance from the fault, as some tectonic and provenance studies have suggested. Instead, we find that superimposed on the primary tectonic control, there is an elevation/temperature control on erosion rates, which is probably transient and related to frost-cracking and glacial retreat.
Our results highlight the potential for 10Be catchment-averaged erosion rates to provide insights into the magnitude and distribution of tectonic deformation rates, and the limitations that arise from transient erosion controls related to the seismic cycle and climate-modulated surface processes.
How to cite: Roda-Boluda, D., Schildgen, T., Wittmann-Oelze, H., Tofelde, S., Bufe, A., Prancevic, J., and Hovius, N.: Erosion rates of the New Zealand Southern Alps reflect long-term tectonics and transient climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6571, https://doi.org/10.5194/egusphere-egu21-6571, 2021.
EGU21-3439 | vPICO presentations | GM4.15
Buffering of interglacial landscape evolution due to reduced sediment transport during glacial periods in BhutanLarissa de Palézieux, Kerry Leith, and Simon Loew
Fluvial systems provide a primary means of sediment transport in alpine environments. This transport potential is regulated by precipitation, a fundamental contributor to stream power. Here, we investigate the legacy of reduced sediment transport capacity during dryer glacial intervals to fundamentally affect the diverse long-term evolution of 2 alpine catchments in the NW of Bhutan. The landscape in this region is characterized by three distinct geomorphic domains including transport-limited alluvial plains in the Inner Valleys, detachment-limited regimes in narrow valleys with steep hillslopes and high relief, and glacially overprinted low-relief landscapes at the foot of the High Himalayan peaks. The two major drainage basins, the Wong Chhu basin in the West and the Puna Tsang Chhu basin in the East, both traverse these geomorphic domains, yet show marked differences in their river profiles, with the alluvial plain of the Wong basin located 1000 m higher than the Puna Tsang Chhu basin.
The characteristic difference in elevation and extent of the alluvial infill between the two main basins of NW Bhutan, points to a systematic difference in relative erosional efficacy. For the effects of baselevel fall due to differential uplift on the Himalayan rangefront to be expressed as increased erosional potential in the High Himalaya, sediment deposited in alluvial planes of the Inner Valleys during low stream power glacial periods must first be evacuated during interglacial intervals. Through a combination of geomorphological mapping and chi analysis of river profiles, we demonstrate that while post-glacial incision today is approaching the upper limit of the alluvial plain in the Puna Tsang Chhu (and can therefore drive bedrock incision through much of a ~40 kYr interglacial interval), the present-day erosional limit in the Wang Chhu is less than half-way through the alluvial fill in the Wang Chhu. It is therefore unlikely rivers in the Wang Chhu have been able to access bedrock or propagate the effects of baselevel fall to the upper extents of the catchment since the mid-Pleistocene transition (MPT).
The evolution of the fluvial system appears to be reflected in rock mass weathering and hillslope evolution throughout the study area. Engineering geological descriptions of rock mass properties, in particular weathering, recorded at 295 sites over a period of 8 weeks in the region closely associated with alluvial valleys demonstrates a range of weathering grades from fresh rock to residual soil. A progressive increase in weathering degree with increasing elevation above river channels is evident in both catchments, indicating the signal reflects the time since active fluvial erosion ceased (as opposed to a pre-existing rock mass property). We observe higher degrees of weathering in the Puna Tsang Chhu valley, corresponding to the more humid climate in this valley supporting more rapid bedrock weathering. This more efficient transition from rock to soil at lower elevations may hint at a positive feedback in which despite indications of an additional 1000 m of cumulative incision since the MPT, hillslopes have evolved to erode at a rate which approaches that of fluvial incision.
How to cite: de Palézieux, L., Leith, K., and Loew, S.: Buffering of interglacial landscape evolution due to reduced sediment transport during glacial periods in Bhutan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3439, https://doi.org/10.5194/egusphere-egu21-3439, 2021.
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Fluvial systems provide a primary means of sediment transport in alpine environments. This transport potential is regulated by precipitation, a fundamental contributor to stream power. Here, we investigate the legacy of reduced sediment transport capacity during dryer glacial intervals to fundamentally affect the diverse long-term evolution of 2 alpine catchments in the NW of Bhutan. The landscape in this region is characterized by three distinct geomorphic domains including transport-limited alluvial plains in the Inner Valleys, detachment-limited regimes in narrow valleys with steep hillslopes and high relief, and glacially overprinted low-relief landscapes at the foot of the High Himalayan peaks. The two major drainage basins, the Wong Chhu basin in the West and the Puna Tsang Chhu basin in the East, both traverse these geomorphic domains, yet show marked differences in their river profiles, with the alluvial plain of the Wong basin located 1000 m higher than the Puna Tsang Chhu basin.
The characteristic difference in elevation and extent of the alluvial infill between the two main basins of NW Bhutan, points to a systematic difference in relative erosional efficacy. For the effects of baselevel fall due to differential uplift on the Himalayan rangefront to be expressed as increased erosional potential in the High Himalaya, sediment deposited in alluvial planes of the Inner Valleys during low stream power glacial periods must first be evacuated during interglacial intervals. Through a combination of geomorphological mapping and chi analysis of river profiles, we demonstrate that while post-glacial incision today is approaching the upper limit of the alluvial plain in the Puna Tsang Chhu (and can therefore drive bedrock incision through much of a ~40 kYr interglacial interval), the present-day erosional limit in the Wang Chhu is less than half-way through the alluvial fill in the Wang Chhu. It is therefore unlikely rivers in the Wang Chhu have been able to access bedrock or propagate the effects of baselevel fall to the upper extents of the catchment since the mid-Pleistocene transition (MPT).
The evolution of the fluvial system appears to be reflected in rock mass weathering and hillslope evolution throughout the study area. Engineering geological descriptions of rock mass properties, in particular weathering, recorded at 295 sites over a period of 8 weeks in the region closely associated with alluvial valleys demonstrates a range of weathering grades from fresh rock to residual soil. A progressive increase in weathering degree with increasing elevation above river channels is evident in both catchments, indicating the signal reflects the time since active fluvial erosion ceased (as opposed to a pre-existing rock mass property). We observe higher degrees of weathering in the Puna Tsang Chhu valley, corresponding to the more humid climate in this valley supporting more rapid bedrock weathering. This more efficient transition from rock to soil at lower elevations may hint at a positive feedback in which despite indications of an additional 1000 m of cumulative incision since the MPT, hillslopes have evolved to erode at a rate which approaches that of fluvial incision.
How to cite: de Palézieux, L., Leith, K., and Loew, S.: Buffering of interglacial landscape evolution due to reduced sediment transport during glacial periods in Bhutan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3439, https://doi.org/10.5194/egusphere-egu21-3439, 2021.
EGU21-8508 | vPICO presentations | GM4.15
Approach for analyzing landslide and torrential flow hazard conditions in relation to landscape evolution in the northern Colombian AndesKarolina Naranjo Bedoya, Edier Aristizábal, Daniel Hölbling, John García, Asaf Aguilar, and David Ortiz
Colombia is an equatorial country located in the northwestern corner of South America with characteristic and complex climatic and geologic settings, which contribute to a great diversity of landforms in the Colombian Andes. 65% of the Colombian population is concentrated in this mountainous terrain, where landslides and torrential flows are common. These natural hazards led to several tragic events over time. Their occurrence is favored by a very dynamic landscape made up of weak and highly weathered materials and affected by tectonic stress. In this study, we aim to gain a better understanding of morphometric control on the occurrence of landslides and torrential flows through process geomorphology and information derived from Digital Elevation Models (DEMs). Several morphometric indices related to drainage network, basin geometry, drainage texture, relief characteristics, asymmetry factor and others were calculated over 168 drainage basins in the northern Colombian Andes. We used quantitative geomorphology to find patterns of anomalies associated with landscape evolution and the occurrence of landslides and torrential flows. Understanding morphodynamics from morphogenesis is important to assess landslide and torrential flow hazard conditions in relation to landscape characteristics and evolution, to support hazard assessment, and consequently to reduce human and economic losses.
Keywords: Landslide, torrential flow, morphometric indices, mountainous terrains.
How to cite: Naranjo Bedoya, K., Aristizábal, E., Hölbling, D., García, J., Aguilar, A., and Ortiz, D.: Approach for analyzing landslide and torrential flow hazard conditions in relation to landscape evolution in the northern Colombian Andes , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8508, https://doi.org/10.5194/egusphere-egu21-8508, 2021.
Colombia is an equatorial country located in the northwestern corner of South America with characteristic and complex climatic and geologic settings, which contribute to a great diversity of landforms in the Colombian Andes. 65% of the Colombian population is concentrated in this mountainous terrain, where landslides and torrential flows are common. These natural hazards led to several tragic events over time. Their occurrence is favored by a very dynamic landscape made up of weak and highly weathered materials and affected by tectonic stress. In this study, we aim to gain a better understanding of morphometric control on the occurrence of landslides and torrential flows through process geomorphology and information derived from Digital Elevation Models (DEMs). Several morphometric indices related to drainage network, basin geometry, drainage texture, relief characteristics, asymmetry factor and others were calculated over 168 drainage basins in the northern Colombian Andes. We used quantitative geomorphology to find patterns of anomalies associated with landscape evolution and the occurrence of landslides and torrential flows. Understanding morphodynamics from morphogenesis is important to assess landslide and torrential flow hazard conditions in relation to landscape characteristics and evolution, to support hazard assessment, and consequently to reduce human and economic losses.
Keywords: Landslide, torrential flow, morphometric indices, mountainous terrains.
How to cite: Naranjo Bedoya, K., Aristizábal, E., Hölbling, D., García, J., Aguilar, A., and Ortiz, D.: Approach for analyzing landslide and torrential flow hazard conditions in relation to landscape evolution in the northern Colombian Andes , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8508, https://doi.org/10.5194/egusphere-egu21-8508, 2021.
EGU21-15605 | vPICO presentations | GM4.15
Analysis of controlling factors on boulder production on the hillslopes of the upper Bhote Koshi catchment, NepalBenedetta Dini and Georgina L. Bennett
Landslides from mountainous bedrock hillslopes often contain boulders, the presence of which has been shown to influence landscape evolution by altering hillslope geomorphic processes and river erosion. Furthermore, the presence in various proportions of large grain sizes on hillslopes can amplify both landslide and flood hazards in largely unquantified ways. Boulders can have an immediate destructive potential on properties and infrastructure and can hinder response and recovery by blocking access routes, posing a challenge for removal. On entering the river network, they might have far reaching effects if remobilised in high flows, damaging or destroying key infrastructure such as hydropower plants and inducing significant knock-on effects on local economies. A fundamental step towards quantification of increased hazard potential is the understanding environmental controls on boulder production. Despite their potential to enhance hazard, the probability of large boulders being produced within different landslide types has not been directly accounted for in landslide hazard mapping.
Our study focuses on the upper Bhote Koshi catchment, northeast of Kathmandu (Nepal), characterised by extreme topographic gradients, seismicity and monsoonal climate, and subjected to frequent landslides and floods. This, coupled with increased population pressure and infrastructure growth, makes the area prone to natural disasters.
We used high resolution optical imagery to map more than 11300 boulders and analysed this large dataset in combination with lithology and topography, and well as structural and landslide data, to investigate controls on boulder production and grain size distributions in different lithological, structural and geomorphic settings of the landscape.
Lithology appears to exert a significant influence on boulder sizes, with statistically significantly larger boulders observed in crystalline rocks of the Higher Himalaya Sequence than in metasedimentary rocks of the Lesser Himalaya Sequence. We also observe that the spacing of the most pervasive fracture set, parallel to foliation, influences boulder size distributions in some lithologies, whilst other dominant regional fracture sets appear not to strongly correlate with mapped boulder sizes.
Although recent studies have shown the importance of structural control on boulder sizes, our large dataset reveals that for complex, high-relief landscapes, with high erosion rates, fracture characteristics do not fully explain grain size distribution.
The type of processes involved in boulder production and transport on slopes, before reaching the river network, also appears to exert a control over grain size distributions and boulder density, with rockfall processes appearing to be responsible for producing boulders with largest sizes as opposed to rockslides, where the high energy and mode of transport is likely associated with increased fragmentation.
Analysing lithological and structural characteristics alone may not be sufficient to explain the observed distribution and would thus only give a limited insight in the enhanced hazard levels posed by boulders across different sectors of a landscape and other factors, such as distance from source and mode of transport at shorter temporal scales, must be taken into account.
How to cite: Dini, B. and Bennett, G. L.: Analysis of controlling factors on boulder production on the hillslopes of the upper Bhote Koshi catchment, Nepal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15605, https://doi.org/10.5194/egusphere-egu21-15605, 2021.
Landslides from mountainous bedrock hillslopes often contain boulders, the presence of which has been shown to influence landscape evolution by altering hillslope geomorphic processes and river erosion. Furthermore, the presence in various proportions of large grain sizes on hillslopes can amplify both landslide and flood hazards in largely unquantified ways. Boulders can have an immediate destructive potential on properties and infrastructure and can hinder response and recovery by blocking access routes, posing a challenge for removal. On entering the river network, they might have far reaching effects if remobilised in high flows, damaging or destroying key infrastructure such as hydropower plants and inducing significant knock-on effects on local economies. A fundamental step towards quantification of increased hazard potential is the understanding environmental controls on boulder production. Despite their potential to enhance hazard, the probability of large boulders being produced within different landslide types has not been directly accounted for in landslide hazard mapping.
Our study focuses on the upper Bhote Koshi catchment, northeast of Kathmandu (Nepal), characterised by extreme topographic gradients, seismicity and monsoonal climate, and subjected to frequent landslides and floods. This, coupled with increased population pressure and infrastructure growth, makes the area prone to natural disasters.
We used high resolution optical imagery to map more than 11300 boulders and analysed this large dataset in combination with lithology and topography, and well as structural and landslide data, to investigate controls on boulder production and grain size distributions in different lithological, structural and geomorphic settings of the landscape.
Lithology appears to exert a significant influence on boulder sizes, with statistically significantly larger boulders observed in crystalline rocks of the Higher Himalaya Sequence than in metasedimentary rocks of the Lesser Himalaya Sequence. We also observe that the spacing of the most pervasive fracture set, parallel to foliation, influences boulder size distributions in some lithologies, whilst other dominant regional fracture sets appear not to strongly correlate with mapped boulder sizes.
Although recent studies have shown the importance of structural control on boulder sizes, our large dataset reveals that for complex, high-relief landscapes, with high erosion rates, fracture characteristics do not fully explain grain size distribution.
The type of processes involved in boulder production and transport on slopes, before reaching the river network, also appears to exert a control over grain size distributions and boulder density, with rockfall processes appearing to be responsible for producing boulders with largest sizes as opposed to rockslides, where the high energy and mode of transport is likely associated with increased fragmentation.
Analysing lithological and structural characteristics alone may not be sufficient to explain the observed distribution and would thus only give a limited insight in the enhanced hazard levels posed by boulders across different sectors of a landscape and other factors, such as distance from source and mode of transport at shorter temporal scales, must be taken into account.
How to cite: Dini, B. and Bennett, G. L.: Analysis of controlling factors on boulder production on the hillslopes of the upper Bhote Koshi catchment, Nepal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15605, https://doi.org/10.5194/egusphere-egu21-15605, 2021.
EGU21-10795 | vPICO presentations | GM4.15
Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strengthOdin Marc, Jens Turowski, and Patrick Meunier
How to cite: Marc, O., Turowski, J., and Meunier, P.: Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10795, https://doi.org/10.5194/egusphere-egu21-10795, 2021.
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How to cite: Marc, O., Turowski, J., and Meunier, P.: Controls on the grain size distribution of landslides in Taiwan: the influence of drop height, scar depth and bedrock strength, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10795, https://doi.org/10.5194/egusphere-egu21-10795, 2021.
EGU21-16062 | vPICO presentations | GM4.15
The spatial variability of landslide occurrences and transported sediments induced by the 2018 Hokkaido Eastern Iburi earthquake, JapanYohei Arata, Takashi Gomi, Rasis Putra Ritonga, and Roy C. Sidle
The spatial variability of landslides and associated sediment deposits induced by earthquakes alters both short- and long-term sediment dynamics in watersheds. Linkages between landslide occurrence and sediment accumulations within channels are important for evaluating spatial and temporal dynamics of sediment from headwaters to downstream. To evaluate spatial variability of landslides, we examined landslide-area density (LAD: landslide area divided by watershed area) in different sub-watersheds (areas 0.01 to 4.4 km2) of Habiugawa watershed (40 km2), which was affected by the 2018 Hokkaido Eastern Iburi earthquake, Japan. The watershed is located 13 km north of the epicenter and is covered by secondary conifer and deciduous forest. The topography is hilly associated with long-term landform development by paleo-glacial erosion. Altitude ranges from 30 to 440 m; mean hillslope and channel gradients are 30° and 10°, respectively. Landslides mostly occurred at depths from 1 to 2 m below pumice layers formed by the Mt. Tarumae eruption 9000 yr ago (Ta-d), with total soil depths from 2 to 3 m. The 0.5 m LiDAR-based DEM and 0.2 m post-earthquake orthophotos were used to calculate LAD by GIS analysis. To examine spatial variability of in-channel sediment deposited by landslides, we used deposit-length ratio (DLR: total length of sediment accumulations within channels divided by total channel length within sub-watersheds). Sediment deposition in channels was assessed as rough surface topography by DEM and orthophotos.
We identified 2941 landslides: mean area=1620 m2; range from 20 to 34710 m2. LAD in the entire Habiugawa watershed was 0.12 km2 km-2, which is high compared to the other earthquake-induced landslides (e.g., Wenchuan earthquake: 0.03 km2 km-2). Sub-watersheds < 0.1 km2 had wide ranges in LADs (0.0 to 0.8 km2 km-2), while sub-watersheds from 0.1 to 0.5 km2 ranged from 0.2 to 0.5. Sub-watersheds > 0.5 km2 had LADs from 0.1 to 0.3. Seventy-four percent of small watersheds (< 0.5 km2) with high LADs (> 0.3) also had high sediment accumulations within gentle channels (DLR ≥ 0.8). This suggests that poorly mobilized sediments that initiate in headwaters rapidly deposit in channels. Conversely, the other small watersheds (26%) had lower sediment accumulation within steeper channels (DLR < 0.8), suggesting that these high-mobilized sediments traveled longer and were evacuated from watersheds to some extent. Such differences in sediment mobility in small sub-watersheds (< 0.5 km2) may cause sporadic sediment accumulations within channels of larger watersheds (> 0.5 km2). Our findings suggest that geomorphic features of watersheds associated with long-term legacies of geomorphic evolution possibly affect the spatial variability of landslide occurrence and the associated in-channel sediment accumulation induced by the earthquake.
How to cite: Arata, Y., Gomi, T., Ritonga, R. P., and Sidle, R. C.: The spatial variability of landslide occurrences and transported sediments induced by the 2018 Hokkaido Eastern Iburi earthquake, Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16062, https://doi.org/10.5194/egusphere-egu21-16062, 2021.
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The spatial variability of landslides and associated sediment deposits induced by earthquakes alters both short- and long-term sediment dynamics in watersheds. Linkages between landslide occurrence and sediment accumulations within channels are important for evaluating spatial and temporal dynamics of sediment from headwaters to downstream. To evaluate spatial variability of landslides, we examined landslide-area density (LAD: landslide area divided by watershed area) in different sub-watersheds (areas 0.01 to 4.4 km2) of Habiugawa watershed (40 km2), which was affected by the 2018 Hokkaido Eastern Iburi earthquake, Japan. The watershed is located 13 km north of the epicenter and is covered by secondary conifer and deciduous forest. The topography is hilly associated with long-term landform development by paleo-glacial erosion. Altitude ranges from 30 to 440 m; mean hillslope and channel gradients are 30° and 10°, respectively. Landslides mostly occurred at depths from 1 to 2 m below pumice layers formed by the Mt. Tarumae eruption 9000 yr ago (Ta-d), with total soil depths from 2 to 3 m. The 0.5 m LiDAR-based DEM and 0.2 m post-earthquake orthophotos were used to calculate LAD by GIS analysis. To examine spatial variability of in-channel sediment deposited by landslides, we used deposit-length ratio (DLR: total length of sediment accumulations within channels divided by total channel length within sub-watersheds). Sediment deposition in channels was assessed as rough surface topography by DEM and orthophotos.
We identified 2941 landslides: mean area=1620 m2; range from 20 to 34710 m2. LAD in the entire Habiugawa watershed was 0.12 km2 km-2, which is high compared to the other earthquake-induced landslides (e.g., Wenchuan earthquake: 0.03 km2 km-2). Sub-watersheds < 0.1 km2 had wide ranges in LADs (0.0 to 0.8 km2 km-2), while sub-watersheds from 0.1 to 0.5 km2 ranged from 0.2 to 0.5. Sub-watersheds > 0.5 km2 had LADs from 0.1 to 0.3. Seventy-four percent of small watersheds (< 0.5 km2) with high LADs (> 0.3) also had high sediment accumulations within gentle channels (DLR ≥ 0.8). This suggests that poorly mobilized sediments that initiate in headwaters rapidly deposit in channels. Conversely, the other small watersheds (26%) had lower sediment accumulation within steeper channels (DLR < 0.8), suggesting that these high-mobilized sediments traveled longer and were evacuated from watersheds to some extent. Such differences in sediment mobility in small sub-watersheds (< 0.5 km2) may cause sporadic sediment accumulations within channels of larger watersheds (> 0.5 km2). Our findings suggest that geomorphic features of watersheds associated with long-term legacies of geomorphic evolution possibly affect the spatial variability of landslide occurrence and the associated in-channel sediment accumulation induced by the earthquake.
How to cite: Arata, Y., Gomi, T., Ritonga, R. P., and Sidle, R. C.: The spatial variability of landslide occurrences and transported sediments induced by the 2018 Hokkaido Eastern Iburi earthquake, Japan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16062, https://doi.org/10.5194/egusphere-egu21-16062, 2021.
EGU21-3143 | vPICO presentations | GM4.15
A prototype, high-resolution multi-temporal landslide inventory for the Sillaro River basin, Northern ApenninesSharon Pittau, Giovanna Daniele, Marco Pizziolo, and Francesco Brardinoni
In mountain environments, landslides are dominant geomorphic processes of sediment transfer and as such, they play a fundamental role in landscape evolution and sediment management at the watershed scale. While monitoring of landslide dynamics at the scale of the single slope failure provides precious site-specific information, an appraisal of landslide-driven sediment dynamics at more representative spatial scales is rarely pursued. In this context, the compilation of multi-temporal, high-resolution landslide inventory represents a challenging but critical task.
In the Emilia-Romagna region (Italy), landslides cover about the 24% of the hilly and mountain areas within the Northern Apennines. Here, the most common types of landslides are earth slides and earthflows that mainly involve the terrain of clay Ligurian Units and usually are the re-activations of preexisting mass movements. Since the mid ’80, the Geological Survey of Emilia-Romagna Region (RER) has started compiling and updating a region-wide landslide inventory, which includes all movement types, as well as both active (n = 44,377) and dormant (n = 36,608) landforms. The inventory update is customarily performed in selected areas, mainly where landslides have created damages or pose risk to infrastructures, or where ad hoc land planning is needed. In this context, a systematic multi-temporal approach that could provide robust information on landslide occurrence and recurrence is missing.
To address this gap, in this contribution we propose a multi-temporal inventory prototype, which includes a set of attributes aimed at characterizing landslide sediment transfer across decades. The prototype is developed in the mountain portion of the Sillaro River basin (139 km2). The basin is chiefly underlain by argillites of the Ligurian domain, where earth slide and earthflow activity is pervasive.
The compilation of the multi-temporal landslide inventory is conducted through visual inspection of 10 sequential aerial photo sets (1954, 1969, 1976, 1985-88, 1996, 2000, 2006, 2008, 2011, and 2014), as well as Google Earth satellite imagery (2016 and 2018). In particular, each landslide polygon encloses the total disturbed area, which includes initiation, transport and deposition zones. Polygon planimetric changes are then recorded across sequential photosets. In this way, it is possible to record recurring landslide movements.
Landslide planimetric geometry includes length, width, and area. Landslide attributes include movement type, photo year of occurrence, morphologic position at initiation (source), and sediment delivery target (sink). Subsequently, for each landslide we subdivide total disturbed area into initiation-transport and deposition polygons. For recurring landslides, we note whether the movement involved: (i) the whole landslide body or only part of it; (ii) headscarp migration; and (iii) advance of the landslide terminus. Finally, we note whether the landslide deposition zone displayed headward incision by means of gully development and/or revegetation.
This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.
How to cite: Pittau, S., Daniele, G., Pizziolo, M., and Brardinoni, F.: A prototype, high-resolution multi-temporal landslide inventory for the Sillaro River basin, Northern Apennines, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3143, https://doi.org/10.5194/egusphere-egu21-3143, 2021.
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In mountain environments, landslides are dominant geomorphic processes of sediment transfer and as such, they play a fundamental role in landscape evolution and sediment management at the watershed scale. While monitoring of landslide dynamics at the scale of the single slope failure provides precious site-specific information, an appraisal of landslide-driven sediment dynamics at more representative spatial scales is rarely pursued. In this context, the compilation of multi-temporal, high-resolution landslide inventory represents a challenging but critical task.
In the Emilia-Romagna region (Italy), landslides cover about the 24% of the hilly and mountain areas within the Northern Apennines. Here, the most common types of landslides are earth slides and earthflows that mainly involve the terrain of clay Ligurian Units and usually are the re-activations of preexisting mass movements. Since the mid ’80, the Geological Survey of Emilia-Romagna Region (RER) has started compiling and updating a region-wide landslide inventory, which includes all movement types, as well as both active (n = 44,377) and dormant (n = 36,608) landforms. The inventory update is customarily performed in selected areas, mainly where landslides have created damages or pose risk to infrastructures, or where ad hoc land planning is needed. In this context, a systematic multi-temporal approach that could provide robust information on landslide occurrence and recurrence is missing.
To address this gap, in this contribution we propose a multi-temporal inventory prototype, which includes a set of attributes aimed at characterizing landslide sediment transfer across decades. The prototype is developed in the mountain portion of the Sillaro River basin (139 km2). The basin is chiefly underlain by argillites of the Ligurian domain, where earth slide and earthflow activity is pervasive.
The compilation of the multi-temporal landslide inventory is conducted through visual inspection of 10 sequential aerial photo sets (1954, 1969, 1976, 1985-88, 1996, 2000, 2006, 2008, 2011, and 2014), as well as Google Earth satellite imagery (2016 and 2018). In particular, each landslide polygon encloses the total disturbed area, which includes initiation, transport and deposition zones. Polygon planimetric changes are then recorded across sequential photosets. In this way, it is possible to record recurring landslide movements.
Landslide planimetric geometry includes length, width, and area. Landslide attributes include movement type, photo year of occurrence, morphologic position at initiation (source), and sediment delivery target (sink). Subsequently, for each landslide we subdivide total disturbed area into initiation-transport and deposition polygons. For recurring landslides, we note whether the movement involved: (i) the whole landslide body or only part of it; (ii) headscarp migration; and (iii) advance of the landslide terminus. Finally, we note whether the landslide deposition zone displayed headward incision by means of gully development and/or revegetation.
This work, as part of the projects BEDFLOW and BEFLOW PLUS, is partially funded by Fondazione Cassa di Risparmio in Bologna.
How to cite: Pittau, S., Daniele, G., Pizziolo, M., and Brardinoni, F.: A prototype, high-resolution multi-temporal landslide inventory for the Sillaro River basin, Northern Apennines, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3143, https://doi.org/10.5194/egusphere-egu21-3143, 2021.
GM4.16 – (Dis)connectivity in hydro-geomorphic systems: emerging concepts and their applications
EGU21-1143 | vPICO presentations | GM4.16
Connected or disconnected: functioning and management of (dis)connectivity in fluvial systems.Janet Hooke
Connectivity provides a powerful framework for analysis of fluvial system functioning at a range of scales but identification of disconnectivity and application to management presents challenges. Three stages of evaluation are suggested, depending on the purpose of study and aims of management, and on the underlying strategy and approach. An overall premise of management is assumed of working with nature and allowing or enabling the system to function as sustainably as possible.
The first stage entails identification of the connectivity status and the disconnectors in the system. This includes analysis of what is being disconnected (water, fine sediment, coarse sediment, pollutants), under what conditions and when the disconnector operates, and the types and locations of disconnector. Various methods can be used but present modelling has deficiencies and requires field validation. That presents challenges in recognition of disconnectors across a range of spatial and temporal scales, but recommended strategies are discussed.
A second stage for management is to analyse to what extent the present functioning is influenced and controlled by human actions, such as land use and structures, and how it departs from a more natural or less disturbed functioning. This can then provide a platform for developing a strategy that amends past disturbances and moves the functioning towards identified management goals. However, these goals can differ and may be in conflict for different components of the same system. For example, for many ecological restoration goals the strategy may be to remove disconnectors such as dams and weirs, to allow greater connectivity of species, e.g. fish. On the other hand, if the problem to be addressed is the increased soil erosion or flooding caused by human disturbance then the goal may be to increase the disconnectivity and reduce fluxes through the system. Our research has proposed that use of vegetation is a sustainable and adaptable method of fulfilling this goal, and discusses how analysis of connectivity and identification of key points for disconnection allows the development of spatial strategies for management.
How to cite: Hooke, J.: Connected or disconnected: functioning and management of (dis)connectivity in fluvial systems., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1143, https://doi.org/10.5194/egusphere-egu21-1143, 2021.
Connectivity provides a powerful framework for analysis of fluvial system functioning at a range of scales but identification of disconnectivity and application to management presents challenges. Three stages of evaluation are suggested, depending on the purpose of study and aims of management, and on the underlying strategy and approach. An overall premise of management is assumed of working with nature and allowing or enabling the system to function as sustainably as possible.
The first stage entails identification of the connectivity status and the disconnectors in the system. This includes analysis of what is being disconnected (water, fine sediment, coarse sediment, pollutants), under what conditions and when the disconnector operates, and the types and locations of disconnector. Various methods can be used but present modelling has deficiencies and requires field validation. That presents challenges in recognition of disconnectors across a range of spatial and temporal scales, but recommended strategies are discussed.
A second stage for management is to analyse to what extent the present functioning is influenced and controlled by human actions, such as land use and structures, and how it departs from a more natural or less disturbed functioning. This can then provide a platform for developing a strategy that amends past disturbances and moves the functioning towards identified management goals. However, these goals can differ and may be in conflict for different components of the same system. For example, for many ecological restoration goals the strategy may be to remove disconnectors such as dams and weirs, to allow greater connectivity of species, e.g. fish. On the other hand, if the problem to be addressed is the increased soil erosion or flooding caused by human disturbance then the goal may be to increase the disconnectivity and reduce fluxes through the system. Our research has proposed that use of vegetation is a sustainable and adaptable method of fulfilling this goal, and discusses how analysis of connectivity and identification of key points for disconnection allows the development of spatial strategies for management.
How to cite: Hooke, J.: Connected or disconnected: functioning and management of (dis)connectivity in fluvial systems., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1143, https://doi.org/10.5194/egusphere-egu21-1143, 2021.
EGU21-9274 | vPICO presentations | GM4.16
Do Beaver Dam Analogues Really Mimic Beaver Dams?Cherie Westbrook and David Cooper
Beavers profoundly alter streams by building dams. Beaver dams change how water, sediment, nutrients and energy flow through stream corridors enhancing both habitat diversity and landscape connectivity. Humans are captivated by learning from nature and trying to mimic it, especially in human-degraded environments. There is considerable eagerness for using beaver dam analogues (BDAs), also called simulated beaver structures, as low-tech, low cost solutions for restoring the functioning of degraded streams where beavers are not present and cannot survive. The use of BDAs in stream enhancement projects, especially in the western United States, is outpacing the research, leading to questions about whether BDAs do, in fact, yield similar ecosystem-scale effects as natural beaver dams. We review the different names used for BDAs, discuss the many ways these structures can be built and how different types function, and how they compare to real beaver dams. We conclude the talk by exploring what we can expect from various types of BDAs in the short and long term and whether these structures can lead to stream and riparian zone restoration that can facilitate the return of beavers.
How to cite: Westbrook, C. and Cooper, D.: Do Beaver Dam Analogues Really Mimic Beaver Dams?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9274, https://doi.org/10.5194/egusphere-egu21-9274, 2021.
Beavers profoundly alter streams by building dams. Beaver dams change how water, sediment, nutrients and energy flow through stream corridors enhancing both habitat diversity and landscape connectivity. Humans are captivated by learning from nature and trying to mimic it, especially in human-degraded environments. There is considerable eagerness for using beaver dam analogues (BDAs), also called simulated beaver structures, as low-tech, low cost solutions for restoring the functioning of degraded streams where beavers are not present and cannot survive. The use of BDAs in stream enhancement projects, especially in the western United States, is outpacing the research, leading to questions about whether BDAs do, in fact, yield similar ecosystem-scale effects as natural beaver dams. We review the different names used for BDAs, discuss the many ways these structures can be built and how different types function, and how they compare to real beaver dams. We conclude the talk by exploring what we can expect from various types of BDAs in the short and long term and whether these structures can lead to stream and riparian zone restoration that can facilitate the return of beavers.
How to cite: Westbrook, C. and Cooper, D.: Do Beaver Dam Analogues Really Mimic Beaver Dams?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9274, https://doi.org/10.5194/egusphere-egu21-9274, 2021.
EGU21-4180 | vPICO presentations | GM4.16
Evaluating the dynamic hydrological connectivity of a coastal wetland: an application of connectivity response unit (CRU) approach on Chilika Lagoon, Odisha, IndiaUnnati Patel, Manudeo Singh, and Rajiv Sinha
Chilika is a large brackish water lagoon in the eastern coast of India and received the distinction of a Ramsar wetland in 1971. It was put under ‘The Montreux Record’ in 1993 because of large scale degradation, but the remarkable restoration activities led to regaining its Ramsar status in 2002. The Chilika receives an influx of saline water from the Bay of Bengal and that of freshwater from the terrestrial systems from its catchment as well as from a distributary channel of Mahanadi River. Having these two very different types of water influx is a characteristic feature of this wetland which defines its biophysical as well as hydrogeomorphic attributes. There are at least three connectivity-related factors controlling the physical attributes of Chilika Lagoon – its connectivity with the sea, the lagoon-catchment connectivity, and lagoon-river connectivity. In the present work, we have assessed the lagoon-catchment hydrological connectivity for 30 years (1990-2020) by calculating connectivity indices (IC) annually. Using the Connectivity Response Unit (CRU) approach, we evaluated the dynamic hydrological connectivity of the lagoon with its catchment as well. The ICs are calculated as a function of topographic and land-cover factors. Since grasslands and shrubs are the primary land-cover in the catchment, we used NDVI to model the vegetation-induced impedance to the hydrological connectivity. The algebraic sum (IC_sum) of the IC values of each pixel of the catchment in a given year was used to compare the overall connectivity at the inter-annual scale. Since connectivity increases with increasing IC values, a higher IC_sum represents a relatively higher hydrological connectivity. The IC_sum is showing a strong decreasing trend with time, which implies that the overall hydrological connectivity of the lagoon with its catchment is decreasing since the 1990s. Further, the CRU assessment has demarcated the specific regions of the catchment which are showing dynamicity in the hydrological connectivity. As expected, the CRUs with high connectivity potential are in proximity to the lagoon. Nevertheless, there are large patches of CRUs with increasing connectivity in the distal parts of the catchment as well. A total of 13.5% area of the catchment is showing either high or increasing connectivity pattern, however, an overwhelming 67.6% of the catchment is exhibiting either low or decreasing connectivity pattern. In 14% area of the catchment, the connectivity was high in the past, but it is diminishing with time, whereas in 20% of the catchment, the low connectivity is intensifying. The changing lagoon-catchment hydrological connectivity is expected to impact the biophysical and hydrogeomorphic characteristics of the Chilika wetland by impacting the freshwater inflows in a brackish water lagoon such as the Chilika, and therefore, this is an important management consideration for the wetland.
How to cite: Patel, U., Singh, M., and Sinha, R.: Evaluating the dynamic hydrological connectivity of a coastal wetland: an application of connectivity response unit (CRU) approach on Chilika Lagoon, Odisha, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4180, https://doi.org/10.5194/egusphere-egu21-4180, 2021.
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Chilika is a large brackish water lagoon in the eastern coast of India and received the distinction of a Ramsar wetland in 1971. It was put under ‘The Montreux Record’ in 1993 because of large scale degradation, but the remarkable restoration activities led to regaining its Ramsar status in 2002. The Chilika receives an influx of saline water from the Bay of Bengal and that of freshwater from the terrestrial systems from its catchment as well as from a distributary channel of Mahanadi River. Having these two very different types of water influx is a characteristic feature of this wetland which defines its biophysical as well as hydrogeomorphic attributes. There are at least three connectivity-related factors controlling the physical attributes of Chilika Lagoon – its connectivity with the sea, the lagoon-catchment connectivity, and lagoon-river connectivity. In the present work, we have assessed the lagoon-catchment hydrological connectivity for 30 years (1990-2020) by calculating connectivity indices (IC) annually. Using the Connectivity Response Unit (CRU) approach, we evaluated the dynamic hydrological connectivity of the lagoon with its catchment as well. The ICs are calculated as a function of topographic and land-cover factors. Since grasslands and shrubs are the primary land-cover in the catchment, we used NDVI to model the vegetation-induced impedance to the hydrological connectivity. The algebraic sum (IC_sum) of the IC values of each pixel of the catchment in a given year was used to compare the overall connectivity at the inter-annual scale. Since connectivity increases with increasing IC values, a higher IC_sum represents a relatively higher hydrological connectivity. The IC_sum is showing a strong decreasing trend with time, which implies that the overall hydrological connectivity of the lagoon with its catchment is decreasing since the 1990s. Further, the CRU assessment has demarcated the specific regions of the catchment which are showing dynamicity in the hydrological connectivity. As expected, the CRUs with high connectivity potential are in proximity to the lagoon. Nevertheless, there are large patches of CRUs with increasing connectivity in the distal parts of the catchment as well. A total of 13.5% area of the catchment is showing either high or increasing connectivity pattern, however, an overwhelming 67.6% of the catchment is exhibiting either low or decreasing connectivity pattern. In 14% area of the catchment, the connectivity was high in the past, but it is diminishing with time, whereas in 20% of the catchment, the low connectivity is intensifying. The changing lagoon-catchment hydrological connectivity is expected to impact the biophysical and hydrogeomorphic characteristics of the Chilika wetland by impacting the freshwater inflows in a brackish water lagoon such as the Chilika, and therefore, this is an important management consideration for the wetland.
How to cite: Patel, U., Singh, M., and Sinha, R.: Evaluating the dynamic hydrological connectivity of a coastal wetland: an application of connectivity response unit (CRU) approach on Chilika Lagoon, Odisha, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4180, https://doi.org/10.5194/egusphere-egu21-4180, 2021.
EGU21-4306 | vPICO presentations | GM4.16
Unravelling sediment connectivity during an extreme event in an Alpine catchmentVittoria Scorpio, Marco Cavalli, Francesco Comiti, and Stefan Steger
This work presents the results of the basin-scale analysis of sediment connectivity between hillslopes and the main channel during an extreme event in a mountain catchment. The Stolla basin (South Tyrol, Italy) was affected by a high-magnitude event in August 2017, during which the channel experienced widening and bed level changes and more than 600 debris flows, and landslides occurred in the basin.
Hillslope and channel processes were mapped and characterized by using geomorphological analysis of orthophotos and pre- and post-event Digital Terrain Models (DTMs). Mass wasting process connectivity was derived by combining field survey evidence and GIS analysis. The coupling between the debris flows and landslides and the main channel was also evaluated by applying the Index of sediment connectivity (IC) by Cavalli et al. (2013). Binary logistic regression and the receiver operating characteristic curve was used to define thresholds that allow to discriminate connected from disconnected debris flows and landslides, based on IC values with respect to the main channel of the Stolla stream.
First results indicate that the Stolla’s post-event channel width was up to five times the pre-event width. Channel widening occurred mainly through bank erosions, removals of riparian vegetation and over bank depositions. Widening appeared to be accompanied by channel bed aggradation up to 1 m or incision up to -2 m. Depending on the morphological characteristics of the channel and of the valley, sediments were eroded from the banks, from the bed or were delivered by connected debris flows, landslides, and toe erosion processes. Statistical analyses indicate a high efficiency of the logistic regression model and the associated threshold to separate connected from disconnected debris flows and landslides using the IC as a predictor variable.
How to cite: Scorpio, V., Cavalli, M., Comiti, F., and Steger, S.: Unravelling sediment connectivity during an extreme event in an Alpine catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4306, https://doi.org/10.5194/egusphere-egu21-4306, 2021.
This work presents the results of the basin-scale analysis of sediment connectivity between hillslopes and the main channel during an extreme event in a mountain catchment. The Stolla basin (South Tyrol, Italy) was affected by a high-magnitude event in August 2017, during which the channel experienced widening and bed level changes and more than 600 debris flows, and landslides occurred in the basin.
Hillslope and channel processes were mapped and characterized by using geomorphological analysis of orthophotos and pre- and post-event Digital Terrain Models (DTMs). Mass wasting process connectivity was derived by combining field survey evidence and GIS analysis. The coupling between the debris flows and landslides and the main channel was also evaluated by applying the Index of sediment connectivity (IC) by Cavalli et al. (2013). Binary logistic regression and the receiver operating characteristic curve was used to define thresholds that allow to discriminate connected from disconnected debris flows and landslides, based on IC values with respect to the main channel of the Stolla stream.
First results indicate that the Stolla’s post-event channel width was up to five times the pre-event width. Channel widening occurred mainly through bank erosions, removals of riparian vegetation and over bank depositions. Widening appeared to be accompanied by channel bed aggradation up to 1 m or incision up to -2 m. Depending on the morphological characteristics of the channel and of the valley, sediments were eroded from the banks, from the bed or were delivered by connected debris flows, landslides, and toe erosion processes. Statistical analyses indicate a high efficiency of the logistic regression model and the associated threshold to separate connected from disconnected debris flows and landslides using the IC as a predictor variable.
How to cite: Scorpio, V., Cavalli, M., Comiti, F., and Steger, S.: Unravelling sediment connectivity during an extreme event in an Alpine catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4306, https://doi.org/10.5194/egusphere-egu21-4306, 2021.
EGU21-5004 | vPICO presentations | GM4.16
Surface runoff connectivity across scales: revisiting three simulation studiesDaniel Caviedes-Voullième, Ilhan Özgen-Xian, and Christoph Hinz
Surface runoff (dis)connectivity manifests across scales, spawning from different spatial flow patterns, which are dominated by both topography (structural connectivity) and hydrodynamics (dynamic connectivity). How the connectivity builds and evolves throughout rainfall events is integrated into observable hydrological signatures (namely, hydrographs and water balance).
In this contribution we explore the connectivity properties of runoff generation processes across spatial scales. We revisit three case studies of runoff generation during rainfall, numerically simulated by solving shallow-water equations. This approach provides a full description of the hydrodynamic flow fields, allowing to study both the connectivity properties, as well as the domain-integrated hydrological signatures (namely, hydrographs) that build up in response to flow phenomena.
We discuss and link the runoff generation processes arising from (i) runoff generation at the plot scale (20 m2 at cm resolution) with explicit microtopographies, (ii) runoff generation at the hillslope or first-order catchment scale with overland and (ephemeral) rill flows in the Hühnerwasser experimental catchment (4000 m2 at m resolution), and (iii) runoff generation at the catchment scale in the Lower Triangle catchment (15 km2 at m resolution).
The detailed study of runoff generation dynamics highlights the needs to use time-evolving connectivity metrics, which are particularly useful to understand spatiotemporal model output. We computed the number of disconnected flooded clusters (and Euler characteristic) as the main connectivity metric.
The results of the three different systems suggest similar qualitative behaviours of connectivity across scales, from plot to catchment scales, and therefore also offer the possible use of connectivity to understand how fluxes are re-scaled across the landscape, and as a multiscale indicator of hydrological function. The relationship between the connectivity response at a given scale (e.g., plot) and the hydrological signature observed at the next larger scale (e.g., hillslope) may lead into a hierarchical relationship of connectivities and signatures, in which the time-continuous nature of the connectivity signal may give rise to non-linear and threshold behaviours in the larger scale signature.
Additionally, in the context of assessing model quality, connectivity is a feature of the natural system which models (and modellers) should strive to ensure. In this sense, we argue that model formulations, meshing (including resolution/topology and preprocessing/smoothing of the terrain model) and parameterisations should be evaluated not only using integrated signatures (e.g., water balance, hydrographs) or point data (water depth, velocities) but also using (dis)connectivity metrics. In this way, it is possible to evaluate to which extent a model and its setup can simulate natural flow paths and landscape functions.
How to cite: Caviedes-Voullième, D., Özgen-Xian, I., and Hinz, C.: Surface runoff connectivity across scales: revisiting three simulation studies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5004, https://doi.org/10.5194/egusphere-egu21-5004, 2021.
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Surface runoff (dis)connectivity manifests across scales, spawning from different spatial flow patterns, which are dominated by both topography (structural connectivity) and hydrodynamics (dynamic connectivity). How the connectivity builds and evolves throughout rainfall events is integrated into observable hydrological signatures (namely, hydrographs and water balance).
In this contribution we explore the connectivity properties of runoff generation processes across spatial scales. We revisit three case studies of runoff generation during rainfall, numerically simulated by solving shallow-water equations. This approach provides a full description of the hydrodynamic flow fields, allowing to study both the connectivity properties, as well as the domain-integrated hydrological signatures (namely, hydrographs) that build up in response to flow phenomena.
We discuss and link the runoff generation processes arising from (i) runoff generation at the plot scale (20 m2 at cm resolution) with explicit microtopographies, (ii) runoff generation at the hillslope or first-order catchment scale with overland and (ephemeral) rill flows in the Hühnerwasser experimental catchment (4000 m2 at m resolution), and (iii) runoff generation at the catchment scale in the Lower Triangle catchment (15 km2 at m resolution).
The detailed study of runoff generation dynamics highlights the needs to use time-evolving connectivity metrics, which are particularly useful to understand spatiotemporal model output. We computed the number of disconnected flooded clusters (and Euler characteristic) as the main connectivity metric.
The results of the three different systems suggest similar qualitative behaviours of connectivity across scales, from plot to catchment scales, and therefore also offer the possible use of connectivity to understand how fluxes are re-scaled across the landscape, and as a multiscale indicator of hydrological function. The relationship between the connectivity response at a given scale (e.g., plot) and the hydrological signature observed at the next larger scale (e.g., hillslope) may lead into a hierarchical relationship of connectivities and signatures, in which the time-continuous nature of the connectivity signal may give rise to non-linear and threshold behaviours in the larger scale signature.
Additionally, in the context of assessing model quality, connectivity is a feature of the natural system which models (and modellers) should strive to ensure. In this sense, we argue that model formulations, meshing (including resolution/topology and preprocessing/smoothing of the terrain model) and parameterisations should be evaluated not only using integrated signatures (e.g., water balance, hydrographs) or point data (water depth, velocities) but also using (dis)connectivity metrics. In this way, it is possible to evaluate to which extent a model and its setup can simulate natural flow paths and landscape functions.
How to cite: Caviedes-Voullième, D., Özgen-Xian, I., and Hinz, C.: Surface runoff connectivity across scales: revisiting three simulation studies, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5004, https://doi.org/10.5194/egusphere-egu21-5004, 2021.
EGU21-5265 | vPICO presentations | GM4.16
Connectivity of floodplains in Germany – which floodplain extent is relevant?Stephanie Natho
Floodplains are transitional ecosystems, rich in biodiversity, endangered and adapted to inundation by floods. Flood magnitude, hydrologic connectivity and elevation define the extent of an active floodplain. In past centuries, active floodplains in Germany were reduced by up to 90% of their original size – in terms of the area that is statistically inundated at least once every 100 years. But, does this area reflect the area relevant for floodplain ecosystems and for evaluating their functioning and the services they provide? Analyzing two scenarios of Flood Hazard Maps (FHM), a German-wide comparison including 78 rivers was carried out to quantify the extent of floods with statistical occurrence intervals of 5 to 25 years, so-called ‘frequent floods’ (T-frequent), and intervals of 100 years, or ‘medium floods’ (T-medium), as well as selected characteristics. The comparison was carried out on the river (basin) level, and based on hydrological catchments. By additionally analyzing measured discharges of relevant gauges from the past 20 years, real inundation was quantified. As a result, even in exceptional wet years these ‘frequent floods’ occur for a few days per year or not at all. The extent of the two FHM scenarios differs for most areas: Only at 13% of gauging units was the T-frequent inundation extent similar to that of T-medium. Furthermore, within T-medium the land use of arable land doubles and that of urban areas more than doubles, showing how disconnected the T-medium floodplain is in many parts. On the other hand, 25% of grasslands are Natura 2000 meadows occurring within the borders of T-frequent but only 6% are Natura 2000 meadows outside these borders, indicating the effect of connectivity and thus inundation, making these habitats valuable in terms of biodiversity mainly in T-frequent. This study provides evidence that, especially for regulatory services like water purification, water retention and climate mitigation, T-frequent might be more suitable for consideration. With more frequent flooding, less intensively used areas are connected more often, holding back water, nutrients and sediments – in addition to comparatively more areas relevant for nature conservation. For flood protection and also as a refuge for flora and fauna and for connection of habitats, of course the extent of disastrous 100-yr floods are important.
How to cite: Natho, S.: Connectivity of floodplains in Germany – which floodplain extent is relevant?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5265, https://doi.org/10.5194/egusphere-egu21-5265, 2021.
Floodplains are transitional ecosystems, rich in biodiversity, endangered and adapted to inundation by floods. Flood magnitude, hydrologic connectivity and elevation define the extent of an active floodplain. In past centuries, active floodplains in Germany were reduced by up to 90% of their original size – in terms of the area that is statistically inundated at least once every 100 years. But, does this area reflect the area relevant for floodplain ecosystems and for evaluating their functioning and the services they provide? Analyzing two scenarios of Flood Hazard Maps (FHM), a German-wide comparison including 78 rivers was carried out to quantify the extent of floods with statistical occurrence intervals of 5 to 25 years, so-called ‘frequent floods’ (T-frequent), and intervals of 100 years, or ‘medium floods’ (T-medium), as well as selected characteristics. The comparison was carried out on the river (basin) level, and based on hydrological catchments. By additionally analyzing measured discharges of relevant gauges from the past 20 years, real inundation was quantified. As a result, even in exceptional wet years these ‘frequent floods’ occur for a few days per year or not at all. The extent of the two FHM scenarios differs for most areas: Only at 13% of gauging units was the T-frequent inundation extent similar to that of T-medium. Furthermore, within T-medium the land use of arable land doubles and that of urban areas more than doubles, showing how disconnected the T-medium floodplain is in many parts. On the other hand, 25% of grasslands are Natura 2000 meadows occurring within the borders of T-frequent but only 6% are Natura 2000 meadows outside these borders, indicating the effect of connectivity and thus inundation, making these habitats valuable in terms of biodiversity mainly in T-frequent. This study provides evidence that, especially for regulatory services like water purification, water retention and climate mitigation, T-frequent might be more suitable for consideration. With more frequent flooding, less intensively used areas are connected more often, holding back water, nutrients and sediments – in addition to comparatively more areas relevant for nature conservation. For flood protection and also as a refuge for flora and fauna and for connection of habitats, of course the extent of disastrous 100-yr floods are important.
How to cite: Natho, S.: Connectivity of floodplains in Germany – which floodplain extent is relevant?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5265, https://doi.org/10.5194/egusphere-egu21-5265, 2021.
EGU21-7287 | vPICO presentations | GM4.16
Overland flow (dis)connectivity in a new vineyard under steep slope conditions in the Spanish Pyrenees: Effect of DEM resolution and terrain preparationManuel López-Vicente, Joaquín Montenegro-Rodríguez, María del Carmen Antolín, and Yolanda Gogorcena
The ability of identifying –based on numerical analysis– disconnected areas –in terms of overland flow pathways– depends on the digital elevation model (DEM) resolution, type of flow accumulation algorithm and DEM accuracy. On the other hand, tillage practices (in lowlands) and terrain preparation (at any slope gradient) may condition the occurrence of permanent/ temporal disconnected areas. In this study, the effect of DEM resolution and the presence of a drainage ditch and forest trails on the number, location and characteristics of disconnected areas is evaluated in a steep (mean slope gradient of 29%) farmland area of the Spanish Pyrenees. A new vineyard plantation (3785 m2 and 5120 m2 including the transit area; espalier system) and its upslope drainage area are evaluated. This site is located near Barbenuta village (Huesca province), at high elevation (1184-1260 m a.s.l.). Abandoned terraced fields and patches of natural vegetation (trees and shrubs) occupy the upslope area, where several forest trails cross from east to west. To protect soil against water soil erosion, farmers built a drainage ditch (total length of 137 m; ca. 0.30 m width; ca. 0.15 m depth) upslope the vineyard boundary, which minimizes runoff entrance into the field. A professional drone (senseFly© eBee X) was used to obtain –after point cloud processing– Structure-from-Motion (SfM)-derived DEMs at different spatial resolution, namely: 1, 0.5, 0.2, 0.1 and 0.05 m. We used combined information of the DEMs before and after filling the local sinks. As expected, the number (n=34, 341, 1079, 1272 and 1907) and size (mean=500, 60, 21, 18 and 12 m2; median=68, 15, 5, 4 and 2 m2; σ=920, 178, 69, 71 and 49 m2) of sub-basins increased and decreased, respectively, with decreasing the pixel size, due to fractal geometry and higher influence of micro-topography components (e.g. soil roughness, random local sinks) –higher ratios of 'residual topography (σ of slope) / pixel size': 0.2 (at coarser resolution), 1.8, 20.3, 113.6 and 636.8 (at finer resolution)–. The total area also varied with the different DEMs: 17010, 20514, 22398, 22852 and 22807 m2. The number (n=21, 292, 903, 928 and 1283) and area (41, 143, 118, 58 and 44 m2) of disconnected areas increased and decreased, respectively, with decreasing the pixel size, representing 0.24%, 0.70%, 0.53%, 0.25% and 0.19% of the total drainage area. Similar differences were observed in other topographic metrics like the drainage-boundary perimeter and maximum flow length. These results prove the impossibility of defining a unique overland flow pattern. Further research should be focused on the role of runoff depth and how the effect of man-made landscape elements (drainage ditch, forest trail) and practices (tillage) on disconnectivity may depend on rainfall depth and intensity, and indirectly on plant growth.
How to cite: López-Vicente, M., Montenegro-Rodríguez, J., Antolín, M. C., and Gogorcena, Y.: Overland flow (dis)connectivity in a new vineyard under steep slope conditions in the Spanish Pyrenees: Effect of DEM resolution and terrain preparation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7287, https://doi.org/10.5194/egusphere-egu21-7287, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The ability of identifying –based on numerical analysis– disconnected areas –in terms of overland flow pathways– depends on the digital elevation model (DEM) resolution, type of flow accumulation algorithm and DEM accuracy. On the other hand, tillage practices (in lowlands) and terrain preparation (at any slope gradient) may condition the occurrence of permanent/ temporal disconnected areas. In this study, the effect of DEM resolution and the presence of a drainage ditch and forest trails on the number, location and characteristics of disconnected areas is evaluated in a steep (mean slope gradient of 29%) farmland area of the Spanish Pyrenees. A new vineyard plantation (3785 m2 and 5120 m2 including the transit area; espalier system) and its upslope drainage area are evaluated. This site is located near Barbenuta village (Huesca province), at high elevation (1184-1260 m a.s.l.). Abandoned terraced fields and patches of natural vegetation (trees and shrubs) occupy the upslope area, where several forest trails cross from east to west. To protect soil against water soil erosion, farmers built a drainage ditch (total length of 137 m; ca. 0.30 m width; ca. 0.15 m depth) upslope the vineyard boundary, which minimizes runoff entrance into the field. A professional drone (senseFly© eBee X) was used to obtain –after point cloud processing– Structure-from-Motion (SfM)-derived DEMs at different spatial resolution, namely: 1, 0.5, 0.2, 0.1 and 0.05 m. We used combined information of the DEMs before and after filling the local sinks. As expected, the number (n=34, 341, 1079, 1272 and 1907) and size (mean=500, 60, 21, 18 and 12 m2; median=68, 15, 5, 4 and 2 m2; σ=920, 178, 69, 71 and 49 m2) of sub-basins increased and decreased, respectively, with decreasing the pixel size, due to fractal geometry and higher influence of micro-topography components (e.g. soil roughness, random local sinks) –higher ratios of 'residual topography (σ of slope) / pixel size': 0.2 (at coarser resolution), 1.8, 20.3, 113.6 and 636.8 (at finer resolution)–. The total area also varied with the different DEMs: 17010, 20514, 22398, 22852 and 22807 m2. The number (n=21, 292, 903, 928 and 1283) and area (41, 143, 118, 58 and 44 m2) of disconnected areas increased and decreased, respectively, with decreasing the pixel size, representing 0.24%, 0.70%, 0.53%, 0.25% and 0.19% of the total drainage area. Similar differences were observed in other topographic metrics like the drainage-boundary perimeter and maximum flow length. These results prove the impossibility of defining a unique overland flow pattern. Further research should be focused on the role of runoff depth and how the effect of man-made landscape elements (drainage ditch, forest trail) and practices (tillage) on disconnectivity may depend on rainfall depth and intensity, and indirectly on plant growth.
How to cite: López-Vicente, M., Montenegro-Rodríguez, J., Antolín, M. C., and Gogorcena, Y.: Overland flow (dis)connectivity in a new vineyard under steep slope conditions in the Spanish Pyrenees: Effect of DEM resolution and terrain preparation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7287, https://doi.org/10.5194/egusphere-egu21-7287, 2021.
EGU21-8668 | vPICO presentations | GM4.16
A dynamic, network scale sediment (dis)connectivity model to reconstruct historical sediment transfers and river reach sediment budgetsMarco Tangi, Simone Bizzi, Kirstie Fryirs, and Andrea Castelletti
Sediment transport and connectivity are key factors for the functioning of fluvial eco-systems, and variations to these drivers deeply affect the geomorphology of the river system. Given that lags often occur in river systems, these changes may appear displaced in time and space from the disturbances that generated them. Modelling sediment (dis)connectivity and its reaction to anthropic pressures with a network-scale perspective is thus necessary to increase the understanding of river processes, to quantify real impacts and estimate future evolutionary trajectories. The CASCADE model (Schmitt et al., 2016) is a sediment connectivity model developed to address this type of research question: it combines concepts of network modelling with empirical sediment transport formulas to quantitatively describe sediment (dis)connectivity in river networks.
In this work, we present a new version of the CASCADE model which expands on the original model by featuring a dynamic simulation of sediment transport processes in the network (D-CASCADE). This new framework describes sediment connectivity in term of transfer rates through space and time. It takes into consideration multiple factors that can affect sediment transport, such as spatial and temporal variations in water discharge and river geomorphological features (i.e., river gradient and width), different sediment grainsizes, sediment entraining and deposition from and in the river bed and interactions between materials coming from different sources.
We apply the new D-CASCADE on the Bega River, New South Wales, Australia, which due to anthropic alterations post European colonization after 1850 including large-scale deforestation, removal of riparian vegetation and swamp drainage, has experienced significant alteration to the character and behaviour of streams, widespread channel erosion and massive sediment mobilization (Fryirs and Brierley, 2001). Our objective is to reproduce the historical sediment transfers that occurred across the network and associated river reach sediment budgets. First, we reconstructed the pre-settlement geomorphic features of the river network and the past hydrology from historical observations and expert-based reconstruction, and then modelled the sediment transport processes in the network in the last two centuries introducing the different drivers of change observed historically in the proper chronological sequence. Due to the uncertainty in the reconstruction of the historical conditions, multiple scenarios have been used.
The D-CASCADE model successfully reproduces the timing and magnitude of the major sediment transfers of the last two centuries in the Bega River network from headwaters swamps to lowland river reaches and associated channel geomorphic adjustments. Using the knowledge acquired by these historical simulations, the model was also applied to provide estimations on future trajectories of sediment transport and sediment budgets at the river reach scale.
With this research, we demonstrate the potential of the new D-CASCADE model to simulate and quantify at the network-scale sediment transport events generating information on sediment budget transfers from a single event to historical trajectories of the last centuries. Such knowledge paves the way to aid predictions of future impacts of basin-scale management measures and can support decision-making when designing sediment management strategies or river restoration initiatives.
How to cite: Tangi, M., Bizzi, S., Fryirs, K., and Castelletti, A.: A dynamic, network scale sediment (dis)connectivity model to reconstruct historical sediment transfers and river reach sediment budgets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8668, https://doi.org/10.5194/egusphere-egu21-8668, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Sediment transport and connectivity are key factors for the functioning of fluvial eco-systems, and variations to these drivers deeply affect the geomorphology of the river system. Given that lags often occur in river systems, these changes may appear displaced in time and space from the disturbances that generated them. Modelling sediment (dis)connectivity and its reaction to anthropic pressures with a network-scale perspective is thus necessary to increase the understanding of river processes, to quantify real impacts and estimate future evolutionary trajectories. The CASCADE model (Schmitt et al., 2016) is a sediment connectivity model developed to address this type of research question: it combines concepts of network modelling with empirical sediment transport formulas to quantitatively describe sediment (dis)connectivity in river networks.
In this work, we present a new version of the CASCADE model which expands on the original model by featuring a dynamic simulation of sediment transport processes in the network (D-CASCADE). This new framework describes sediment connectivity in term of transfer rates through space and time. It takes into consideration multiple factors that can affect sediment transport, such as spatial and temporal variations in water discharge and river geomorphological features (i.e., river gradient and width), different sediment grainsizes, sediment entraining and deposition from and in the river bed and interactions between materials coming from different sources.
We apply the new D-CASCADE on the Bega River, New South Wales, Australia, which due to anthropic alterations post European colonization after 1850 including large-scale deforestation, removal of riparian vegetation and swamp drainage, has experienced significant alteration to the character and behaviour of streams, widespread channel erosion and massive sediment mobilization (Fryirs and Brierley, 2001). Our objective is to reproduce the historical sediment transfers that occurred across the network and associated river reach sediment budgets. First, we reconstructed the pre-settlement geomorphic features of the river network and the past hydrology from historical observations and expert-based reconstruction, and then modelled the sediment transport processes in the network in the last two centuries introducing the different drivers of change observed historically in the proper chronological sequence. Due to the uncertainty in the reconstruction of the historical conditions, multiple scenarios have been used.
The D-CASCADE model successfully reproduces the timing and magnitude of the major sediment transfers of the last two centuries in the Bega River network from headwaters swamps to lowland river reaches and associated channel geomorphic adjustments. Using the knowledge acquired by these historical simulations, the model was also applied to provide estimations on future trajectories of sediment transport and sediment budgets at the river reach scale.
With this research, we demonstrate the potential of the new D-CASCADE model to simulate and quantify at the network-scale sediment transport events generating information on sediment budget transfers from a single event to historical trajectories of the last centuries. Such knowledge paves the way to aid predictions of future impacts of basin-scale management measures and can support decision-making when designing sediment management strategies or river restoration initiatives.
How to cite: Tangi, M., Bizzi, S., Fryirs, K., and Castelletti, A.: A dynamic, network scale sediment (dis)connectivity model to reconstruct historical sediment transfers and river reach sediment budgets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8668, https://doi.org/10.5194/egusphere-egu21-8668, 2021.
EGU21-9636 | vPICO presentations | GM4.16
Geomorphological numerical modelling of woody dams in CAESAR-LisfloodJosh Wolstenholme, Christopher Skinner, David Milan, and Daniel Parsons
Natural flood management (NFM) promotes the sustainable enhancement of natural fluvial processes to reduce flooding (SEPA, 2015; Wilkinson et al., 2019), and is increasingly popular for use by community groups, contractors and governments (Kay et al., 2019). Reintroduction of wood to a river channel is a popular form of NFM often achieved through seeding natural logjams, or with an emphasis on engineering through installing woody dams (WDs). WDs are currently installed or being installed in catchments in an effort to reduce flood risk, through hydrograph attenuation, increase biodiversity and improve geomorphic heterogeneity (Wenzel et al., 2014; Burgess-Gamble et al., 2017; Grabowski et al., 2019). A further objective is to emulate the effect of natural wood found in river channels by partially, or completely, blocking the channel to accelerate the recruitment of natural wood as part of the natural wood cycle (Addy & Wilkinson, 2016).
There is a growing body of evidence supporting the benefits of NFM, however, the hydrogeomorphic effects of WDs are less well understood (Dadson et al., 2017). There is little scientific underpinning concerning the long-term impact of these features upon hydrogeomorphology at reach and catchment-scales. Very few numerically based studies consider the influence of sediment transport on WDs, and how changes in local bed morphology influence their effectiveness. Most NFM research to date has focused upon modelling the effectiveness of local NFM measures in small catchments (<10 km2) (Dadson et al., 2017), with less work evident at larger spatial and temporal scales (Kay et al., 2019; Wilkinson et al., 2019).
There is a need for a verified tool that is able to represent WDs accounting for geomorphic processes and interactions between the dams and morphodynamics, different design specifications of dams, and changing efficacy due to geomorphic evolution. We present the new CAESAR-Lisflood (Coulthard et al., 2013) “Working with Natural Processes” toolkit, capable of representing WDs across a digital experimental environment. Global sensitivity testing was conducted using the Morris method (Morris, 1991) to assess the sensitivity of five aspects of the toolkit, and their potentially influences on geomorphology and flood risk reduction.
How to cite: Wolstenholme, J., Skinner, C., Milan, D., and Parsons, D.: Geomorphological numerical modelling of woody dams in CAESAR-Lisflood, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9636, https://doi.org/10.5194/egusphere-egu21-9636, 2021.
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Natural flood management (NFM) promotes the sustainable enhancement of natural fluvial processes to reduce flooding (SEPA, 2015; Wilkinson et al., 2019), and is increasingly popular for use by community groups, contractors and governments (Kay et al., 2019). Reintroduction of wood to a river channel is a popular form of NFM often achieved through seeding natural logjams, or with an emphasis on engineering through installing woody dams (WDs). WDs are currently installed or being installed in catchments in an effort to reduce flood risk, through hydrograph attenuation, increase biodiversity and improve geomorphic heterogeneity (Wenzel et al., 2014; Burgess-Gamble et al., 2017; Grabowski et al., 2019). A further objective is to emulate the effect of natural wood found in river channels by partially, or completely, blocking the channel to accelerate the recruitment of natural wood as part of the natural wood cycle (Addy & Wilkinson, 2016).
There is a growing body of evidence supporting the benefits of NFM, however, the hydrogeomorphic effects of WDs are less well understood (Dadson et al., 2017). There is little scientific underpinning concerning the long-term impact of these features upon hydrogeomorphology at reach and catchment-scales. Very few numerically based studies consider the influence of sediment transport on WDs, and how changes in local bed morphology influence their effectiveness. Most NFM research to date has focused upon modelling the effectiveness of local NFM measures in small catchments (<10 km2) (Dadson et al., 2017), with less work evident at larger spatial and temporal scales (Kay et al., 2019; Wilkinson et al., 2019).
There is a need for a verified tool that is able to represent WDs accounting for geomorphic processes and interactions between the dams and morphodynamics, different design specifications of dams, and changing efficacy due to geomorphic evolution. We present the new CAESAR-Lisflood (Coulthard et al., 2013) “Working with Natural Processes” toolkit, capable of representing WDs across a digital experimental environment. Global sensitivity testing was conducted using the Morris method (Morris, 1991) to assess the sensitivity of five aspects of the toolkit, and their potentially influences on geomorphology and flood risk reduction.
How to cite: Wolstenholme, J., Skinner, C., Milan, D., and Parsons, D.: Geomorphological numerical modelling of woody dams in CAESAR-Lisflood, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9636, https://doi.org/10.5194/egusphere-egu21-9636, 2021.
EGU21-13534 | vPICO presentations | GM4.16
Effect of small impediments on channel morphology – intermittent rivers in Brazilian drylands.André Branco and Jonas Souza
Land use on rural drylands has as its occupation process developing a hydric security and transportations infrastructure system. Dryland tropical systems present fluvial hydrological regime controlled by precipitation inputs, with few or none springs, showing ephemeral and intermittent rivers. Floodway crossings are a widespread infrastructure, on the countryside road network, to cross small creeks, especially intermittent and ephemeral rivers during the rainy seasons. Floodways are concrete or rock block structure, with or without culverts, that allows the river flow goes through or over it. They are part of a set of small longitudinal impediments, like small earth dams and check-dams, and can significantly impact the connectivity, notably by the high density of these impediments on rural areas. This research analysed the effect of floodways crossing on longitudinal connectivity of intermittent small rivers, focusing on morphological and sedimentological impacts in Brazilian Dryland. We analysed four floodways crossing with culverts installed on sandbed intermittent rivers, with upstream catchment are from 10 Km² to 130 Km². The analyses were based on rainfall data, lateral and longitudinal topographic profiles, generate by UAV surveys; and sedimentological samples of upstream and downstream of each structure. The Effective Catchment Area (ECA) was the first step to understand that several dams, and other longitudinal disconnect elements, decrease the ECA sharply, from 2 Km² to 38 Km² of the floodways analysed. Consequently, it affects the magnitude and frequency of water and especially sediment that reaches the floodway crossings. The results reveal the increase of upstream local base level, affecting 500 to 1000 meters, and coarse sediment retention, which is 1.7 to 3.6 times the standard percentage of very coarse sand and gravel. The retained sediment can be re-worked (reconnect) by extreme rainfall/discharges events, recurrence 0,22/year, and when the silting surface reaches the culvert level. The evolution of the upstream silting process is controlled not only by construction age but also by ECA spatiality and changes, and frequency and magnitude of rainfall/discharges events. The results discussion enabled developing an evolution model based on four stages: Installation, Adaptation, Coexistence, and Silting up. The Installation stage is the building process that locally deconfigures the channel morphology and, sometimes, inserts unfamiliar materials on channels. The Adaptation Stage starts with the first flow events that recreate a channel morphology but affected by the floodway, with the beginning of enhanced upstream sedimentation and downstream erosion. The Coexistence stage the disconnectivity effect is evident with the upstream sedimentation moving upstream. The downstream erosion creates a pool, expanding the floodway/riverbed height gap, and progressively increasing the vertical incision downstream. Lastly, when the sedimentation reaches the culvert level or the floodway, sediment retention decreases, and most of the transported sediment overpass the impediment. The frequency and magnitude of flow events control the time to progress through each stage, remembering the ECA analysis importance over space and time. This proposed model that still on initial development stage can help the integrative environmental management on areas impacted by widespread small longitudinal impediments.
How to cite: Branco, A. and Souza, J.: Effect of small impediments on channel morphology – intermittent rivers in Brazilian drylands., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13534, https://doi.org/10.5194/egusphere-egu21-13534, 2021.
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Land use on rural drylands has as its occupation process developing a hydric security and transportations infrastructure system. Dryland tropical systems present fluvial hydrological regime controlled by precipitation inputs, with few or none springs, showing ephemeral and intermittent rivers. Floodway crossings are a widespread infrastructure, on the countryside road network, to cross small creeks, especially intermittent and ephemeral rivers during the rainy seasons. Floodways are concrete or rock block structure, with or without culverts, that allows the river flow goes through or over it. They are part of a set of small longitudinal impediments, like small earth dams and check-dams, and can significantly impact the connectivity, notably by the high density of these impediments on rural areas. This research analysed the effect of floodways crossing on longitudinal connectivity of intermittent small rivers, focusing on morphological and sedimentological impacts in Brazilian Dryland. We analysed four floodways crossing with culverts installed on sandbed intermittent rivers, with upstream catchment are from 10 Km² to 130 Km². The analyses were based on rainfall data, lateral and longitudinal topographic profiles, generate by UAV surveys; and sedimentological samples of upstream and downstream of each structure. The Effective Catchment Area (ECA) was the first step to understand that several dams, and other longitudinal disconnect elements, decrease the ECA sharply, from 2 Km² to 38 Km² of the floodways analysed. Consequently, it affects the magnitude and frequency of water and especially sediment that reaches the floodway crossings. The results reveal the increase of upstream local base level, affecting 500 to 1000 meters, and coarse sediment retention, which is 1.7 to 3.6 times the standard percentage of very coarse sand and gravel. The retained sediment can be re-worked (reconnect) by extreme rainfall/discharges events, recurrence 0,22/year, and when the silting surface reaches the culvert level. The evolution of the upstream silting process is controlled not only by construction age but also by ECA spatiality and changes, and frequency and magnitude of rainfall/discharges events. The results discussion enabled developing an evolution model based on four stages: Installation, Adaptation, Coexistence, and Silting up. The Installation stage is the building process that locally deconfigures the channel morphology and, sometimes, inserts unfamiliar materials on channels. The Adaptation Stage starts with the first flow events that recreate a channel morphology but affected by the floodway, with the beginning of enhanced upstream sedimentation and downstream erosion. The Coexistence stage the disconnectivity effect is evident with the upstream sedimentation moving upstream. The downstream erosion creates a pool, expanding the floodway/riverbed height gap, and progressively increasing the vertical incision downstream. Lastly, when the sedimentation reaches the culvert level or the floodway, sediment retention decreases, and most of the transported sediment overpass the impediment. The frequency and magnitude of flow events control the time to progress through each stage, remembering the ECA analysis importance over space and time. This proposed model that still on initial development stage can help the integrative environmental management on areas impacted by widespread small longitudinal impediments.
How to cite: Branco, A. and Souza, J.: Effect of small impediments on channel morphology – intermittent rivers in Brazilian drylands., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13534, https://doi.org/10.5194/egusphere-egu21-13534, 2021.
EGU21-13885 | vPICO presentations | GM4.16
Relationship between sediment connectivity and debris flow in a mountain catchmentBruno Henrique Abatti, Franciele Zanandrea, Leonardo Rodolfo Paul, and Gean Paulo Michel
The hillslope-channel coupling has a fundamental role in sediment control of a catchment, especially when the catchment is prone to mass movements. Debris flow is a type of mass movements that provides an important sediment contribution to a channel, which is influenced by hillslope-channel coupling degree. This coupling can be represented by the connectivity, a concept utilized as an approach to many queries regarding water and/or sediment transport through methodologies which relates a river with its drainage area. In this regard, this study addresses the representation of debris flow in terms of connectivity. We applied a debris flow computational modelling (DFM) and an index of connectivity (IC) in Mascarada catchment, south Brazil, where hundreds of mass movements were triggered in 2017, to evaluate the potential, limitations and capacity of IC to represent patterns of mass movements’ connectivity. The IC is calculated for each cell of the catchment’s digital elevation model (DEM) (horizontal resolution of 1 m) in relation to the drainage network. Therefore, the IC represents the lateral connectivity (hillslope-channel) and its capacity to mobilize sediment to the channel. The DFM utilizes the Multiple Flow Direction to distribute volumes of a fluid with a determined kinematic viscosity through a slope, originated from initiation areas with a depth pre-determined by the user. The model utilizes uniform and steady flow solutions for Newtonian fluid, considering a rectangular channel. The DFM simulated the observed debris flow reasonably well, with an accuracy of 68%. However, since the simulation reached the channel and carried the volumes beyond the observed debris flow scar, it presented an overestimation area of 65%. When relation the simulated debris flow paths with the IC, we observed a superposition between those paths and high IC values. Also, the results showed a pixel-by-pixel positive linear correlation between high flow depths (representing convergence of flow) and IC, with values varying from 0,1 and 0,5. Only one of the nine simulated debris flow did not reach the channel and it had the lowest mean IC value along its flow path. Simulated debris flow that reached the channel showed high hillslope-channel connectivity, denoting the important role of high magnitude sediment transport events in sediment connectivity. Therefore, the IC was capable to represent and indicate patterns of debris flow that reached the channel. Though, the results also indicated that IC must be carefully interpreted when employed to understand debris flow and related processes – some areas have high fluid depth due to low connectivity, but others have high depth in response of convergence of flow due to highly connected areas. In this regard, an integration of connectivity and debris flow modelling tools can by an important step to understand sediment connectivity and to represent patterns of high magnitude mass movements events.
How to cite: Abatti, B. H., Zanandrea, F., Paul, L. R., and Michel, G. P.: Relationship between sediment connectivity and debris flow in a mountain catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13885, https://doi.org/10.5194/egusphere-egu21-13885, 2021.
The hillslope-channel coupling has a fundamental role in sediment control of a catchment, especially when the catchment is prone to mass movements. Debris flow is a type of mass movements that provides an important sediment contribution to a channel, which is influenced by hillslope-channel coupling degree. This coupling can be represented by the connectivity, a concept utilized as an approach to many queries regarding water and/or sediment transport through methodologies which relates a river with its drainage area. In this regard, this study addresses the representation of debris flow in terms of connectivity. We applied a debris flow computational modelling (DFM) and an index of connectivity (IC) in Mascarada catchment, south Brazil, where hundreds of mass movements were triggered in 2017, to evaluate the potential, limitations and capacity of IC to represent patterns of mass movements’ connectivity. The IC is calculated for each cell of the catchment’s digital elevation model (DEM) (horizontal resolution of 1 m) in relation to the drainage network. Therefore, the IC represents the lateral connectivity (hillslope-channel) and its capacity to mobilize sediment to the channel. The DFM utilizes the Multiple Flow Direction to distribute volumes of a fluid with a determined kinematic viscosity through a slope, originated from initiation areas with a depth pre-determined by the user. The model utilizes uniform and steady flow solutions for Newtonian fluid, considering a rectangular channel. The DFM simulated the observed debris flow reasonably well, with an accuracy of 68%. However, since the simulation reached the channel and carried the volumes beyond the observed debris flow scar, it presented an overestimation area of 65%. When relation the simulated debris flow paths with the IC, we observed a superposition between those paths and high IC values. Also, the results showed a pixel-by-pixel positive linear correlation between high flow depths (representing convergence of flow) and IC, with values varying from 0,1 and 0,5. Only one of the nine simulated debris flow did not reach the channel and it had the lowest mean IC value along its flow path. Simulated debris flow that reached the channel showed high hillslope-channel connectivity, denoting the important role of high magnitude sediment transport events in sediment connectivity. Therefore, the IC was capable to represent and indicate patterns of debris flow that reached the channel. Though, the results also indicated that IC must be carefully interpreted when employed to understand debris flow and related processes – some areas have high fluid depth due to low connectivity, but others have high depth in response of convergence of flow due to highly connected areas. In this regard, an integration of connectivity and debris flow modelling tools can by an important step to understand sediment connectivity and to represent patterns of high magnitude mass movements events.
How to cite: Abatti, B. H., Zanandrea, F., Paul, L. R., and Michel, G. P.: Relationship between sediment connectivity and debris flow in a mountain catchment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13885, https://doi.org/10.5194/egusphere-egu21-13885, 2021.
EGU21-14018 | vPICO presentations | GM4.16 | Highlight
Impact assessment of structural barriers and flow regulation on the Ganga River morphology and ecologyGaurav Kailash Sonkar and Kumar Gaurav
The Ganga-Brahmaputra river system in the Himalayan Foreland supports diverse aquatic fauna. Decades of flow regulation through dams and barrages have affected their habitat suitability. To evaluate the impacts of large barrages on the morphology and habitat ecology we studied two different reaches (middle and lower) of the Ganga River. These reaches are the habitat of the endangered Ganga River dolphin (Platanista gangetica). In a reach in the middle Ganga between Bijnor and Narora barrage, a reported rise in dolphin population has been documented. In contrast, near the Farakka barrage in the lower reach of the Ganga River, a significant decline in the dolphin population has been observed.
We use Corona and time-series Landsat satellite images along with flow discharge data to assess the morphological and ecological impact of the barrages. In middle Ganga, the dolphin habitat is isolated between the Bijnor and Narora barrage where the minimum flow is available throughout the year for the dolphins to thrive. On the other hand, in the lower Ganga, contrasting impacts are observed in the proximity (upstream/downstream) of the Farakka barrage. In the downstream, reduction in water (by one-third in the pre-monsoon discharge) and sediment discharge has decoupled the channel belt to its floodplain resulting in a loss of lateral connectivity. The presence of minimum flow between the Bijnor and Narora barrage has aided the dolphin population rise while the loss of lateral connectivity and excess siltation at the Farakka barrage has made the river reach unsuitable for habitation.
How to cite: Sonkar, G. K. and Gaurav, K.: Impact assessment of structural barriers and flow regulation on the Ganga River morphology and ecology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14018, https://doi.org/10.5194/egusphere-egu21-14018, 2021.
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The Ganga-Brahmaputra river system in the Himalayan Foreland supports diverse aquatic fauna. Decades of flow regulation through dams and barrages have affected their habitat suitability. To evaluate the impacts of large barrages on the morphology and habitat ecology we studied two different reaches (middle and lower) of the Ganga River. These reaches are the habitat of the endangered Ganga River dolphin (Platanista gangetica). In a reach in the middle Ganga between Bijnor and Narora barrage, a reported rise in dolphin population has been documented. In contrast, near the Farakka barrage in the lower reach of the Ganga River, a significant decline in the dolphin population has been observed.
We use Corona and time-series Landsat satellite images along with flow discharge data to assess the morphological and ecological impact of the barrages. In middle Ganga, the dolphin habitat is isolated between the Bijnor and Narora barrage where the minimum flow is available throughout the year for the dolphins to thrive. On the other hand, in the lower Ganga, contrasting impacts are observed in the proximity (upstream/downstream) of the Farakka barrage. In the downstream, reduction in water (by one-third in the pre-monsoon discharge) and sediment discharge has decoupled the channel belt to its floodplain resulting in a loss of lateral connectivity. The presence of minimum flow between the Bijnor and Narora barrage has aided the dolphin population rise while the loss of lateral connectivity and excess siltation at the Farakka barrage has made the river reach unsuitable for habitation.
How to cite: Sonkar, G. K. and Gaurav, K.: Impact assessment of structural barriers and flow regulation on the Ganga River morphology and ecology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14018, https://doi.org/10.5194/egusphere-egu21-14018, 2021.
EGU21-14040 | vPICO presentations | GM4.16
Applicability of connectivity concept for disaster management and hazard mitigationManudeo Narayan Singh, Shobhit Singh, Arnab Laha, and Kanchan Mishra
The concept of geomorphic connectivity is being widely used since last two decades to understand and explain the various earth surface processes and dynamics. Its applicability to understand inter- and cross-scale process-response systems is now well established. In the present work, we have evaluated the applicability of the geomorphic connectivity framework (Singh et al., 2020, ESPL) for managing and mitigating various geological hazards. For an effective hazard mitigation and management planning, we need to know (a) source of hazard, (b) hazard propagation pathways, (c) probable affected areas, and (d) identification of escape routes/pathways. The connectivity concept can be effectively utilised to satisfy aforementioned requirements. For example, sediment and hydrological connectivity can be used to evaluate the potential pathways, identify sources and affected areas, and to assess return periods of fluvial-related hazards such as debris flow and riverine flash floods. Similarly, the potential sites of landslide, stream congestions (and hence, flash flood)- can be identified by evaluating the channel-slope sediment connectivity and longitudinal hydrological connectivity. The concept of landscape connectivity can play a pivotal role in understanding the forest fire probabilities by evaluating the connectivity between various fire-prone patches of forests, fuel, and the spatial positions of fire-breaking landscape patches. Based on connectivity concepts, the potential paths of forest fire propagation can be demarcated in advance and can play a crucial role in forest fire mitigation. Other than identifying the risk-prone zones with respect to various hazards, connectivity concept can also be used to plan evacuation routes as well. Therefore, we propose that the geomorphic connectivity framework can be a robust tool to manage and mitigate various geological hazards.
How to cite: Singh, M. N., Singh, S., Laha, A., and Mishra, K.: Applicability of connectivity concept for disaster management and hazard mitigation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14040, https://doi.org/10.5194/egusphere-egu21-14040, 2021.
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The concept of geomorphic connectivity is being widely used since last two decades to understand and explain the various earth surface processes and dynamics. Its applicability to understand inter- and cross-scale process-response systems is now well established. In the present work, we have evaluated the applicability of the geomorphic connectivity framework (Singh et al., 2020, ESPL) for managing and mitigating various geological hazards. For an effective hazard mitigation and management planning, we need to know (a) source of hazard, (b) hazard propagation pathways, (c) probable affected areas, and (d) identification of escape routes/pathways. The connectivity concept can be effectively utilised to satisfy aforementioned requirements. For example, sediment and hydrological connectivity can be used to evaluate the potential pathways, identify sources and affected areas, and to assess return periods of fluvial-related hazards such as debris flow and riverine flash floods. Similarly, the potential sites of landslide, stream congestions (and hence, flash flood)- can be identified by evaluating the channel-slope sediment connectivity and longitudinal hydrological connectivity. The concept of landscape connectivity can play a pivotal role in understanding the forest fire probabilities by evaluating the connectivity between various fire-prone patches of forests, fuel, and the spatial positions of fire-breaking landscape patches. Based on connectivity concepts, the potential paths of forest fire propagation can be demarcated in advance and can play a crucial role in forest fire mitigation. Other than identifying the risk-prone zones with respect to various hazards, connectivity concept can also be used to plan evacuation routes as well. Therefore, we propose that the geomorphic connectivity framework can be a robust tool to manage and mitigate various geological hazards.
How to cite: Singh, M. N., Singh, S., Laha, A., and Mishra, K.: Applicability of connectivity concept for disaster management and hazard mitigation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14040, https://doi.org/10.5194/egusphere-egu21-14040, 2021.
EGU21-14057 | vPICO presentations | GM4.16
Applications of a hydro-geomorphic (dis)connectivity framework to study vegetation transitions in semiarid ecosystems.Patricia Saco, Mariano Moreno-de las Heras, Jose Rodriguez, Steven Sandi, Samira Azadi, and Juan Quijano
Changes in hydro-geomorphic connectivity have been previously linked to catastrophic shifts in landscape structures and function leading to irreversible degradation. Here we present evidence and new observations to better understand the link between connectivity of water and sediments and possible phase transitions for the case of semiarid ecosystems at the catchment and hillslope scales. We first focus on rangelands, where coevolving vegetation and landform structures lead to a distinct connectivity pattern responsible for the healthy functioning of the system. Positive feedbacks, triggered by disturbances in vegetation, water or sediment structures can alter the hydro-geomorphic connectivity leading to degradation. Our results for rangelands in Australia, from both simulations and observations, suggest that an increase in connectivity beyond a threshold may lead to irreversible degradation, meaning that the system return to a functional state is unlikely without extensive management interventions. We also analyse the case of semi-arid floodplain wetlands of the Murray-Darling Basin, where we observe that dis-connectivity during droughts promote terrestrial vegetation encroachment and degradation. Simulations and observations also indicate the presence of thresholds beyond which the recovery of the system is unlikely without interventions.
How to cite: Saco, P., Moreno-de las Heras, M., Rodriguez, J., Sandi, S., Azadi, S., and Quijano, J.: Applications of a hydro-geomorphic (dis)connectivity framework to study vegetation transitions in semiarid ecosystems., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14057, https://doi.org/10.5194/egusphere-egu21-14057, 2021.
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Changes in hydro-geomorphic connectivity have been previously linked to catastrophic shifts in landscape structures and function leading to irreversible degradation. Here we present evidence and new observations to better understand the link between connectivity of water and sediments and possible phase transitions for the case of semiarid ecosystems at the catchment and hillslope scales. We first focus on rangelands, where coevolving vegetation and landform structures lead to a distinct connectivity pattern responsible for the healthy functioning of the system. Positive feedbacks, triggered by disturbances in vegetation, water or sediment structures can alter the hydro-geomorphic connectivity leading to degradation. Our results for rangelands in Australia, from both simulations and observations, suggest that an increase in connectivity beyond a threshold may lead to irreversible degradation, meaning that the system return to a functional state is unlikely without extensive management interventions. We also analyse the case of semi-arid floodplain wetlands of the Murray-Darling Basin, where we observe that dis-connectivity during droughts promote terrestrial vegetation encroachment and degradation. Simulations and observations also indicate the presence of thresholds beyond which the recovery of the system is unlikely without interventions.
How to cite: Saco, P., Moreno-de las Heras, M., Rodriguez, J., Sandi, S., Azadi, S., and Quijano, J.: Applications of a hydro-geomorphic (dis)connectivity framework to study vegetation transitions in semiarid ecosystems., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14057, https://doi.org/10.5194/egusphere-egu21-14057, 2021.
EGU21-16175 | vPICO presentations | GM4.16
Sediment connectivity in the Koiyavgan glacier's cirques (Adyl-Su river basin, Caucasus, Russia)Andrei Kedich, Maxim Uspensky, Anatoly Tsyplenkov, Sergey Kharchenko, and Valentin Golosov
The highland cirques mostly created by nivation and glacial exaration take large areas in mountains and have a significant role in the sediment transit of the basins. The approximate view on the connection of cirques and low levels in the sediment flow could be given with the sediment connectivity index analysis. We study the spatial distribution of the index for typical ice cirque – the Koiyavgan cirque near the join of the Main Caucasus Range and its offshoot (the Gumachy range). This area is located in the tops of the Adyl-Su valley (left side of the Baksan river basin). In August 2020, we got a high-resolution orthophoto image (13+ cm) and digital elevation model (27+ cm) from aerial photography. The territory located in the elevation range from 3230 to 4022 m. Geological conditions: gneiss, metamorphic shale and basic dark coloured igneous rocks. There is no developed vegetation cover. Typical post-glacial cirques topography includes (top-down): mountain tops, very steep bedrock slopes, colluvial footslopes and fans, cirques bottom (moraine ridges with dividing valleys, craters from melting of the in-moraine covered ice etc.) with fluvial, avalanche and creep post-shaping, and bottom surface break as analogue of riegels in glacial trough valleys. The connectivity index (CI) after Cavalli et al. [2013] is very dependent on initial DEM resolution, from the method for filling mistaken depressions, from window size for computing intermediate geomorphometric variables (e.g. roughness index), from choice in flow impedance variable, from area coverage and terrain diversity and others. We compute connectivity index with the parameters: 1) DEM resolution – 27 cm; 2) impedance variable – terrain roughness index (standard deviation of elevation) with window 7*7 cells; 3) standard filling method used in the ArcMap (filling local depression without any limitations on maximum depth); 4) range of impedance values before normalization (partially related to area coverage) is from 0 to 72 m. In the some buffers from the channel network the connectivity index generally grows in the top-down direction. Greatest spurt of the CI values relates to the cirques low border - the riegel (3300 m asl). There are two levels characterised with low values of the CI: 3550 m and 3750 m. The first one is backside of cirques bottom with relatively low flow accumulation area and low-moderate slopes (0-25°), the second one is mountain tops with high steep slopes, but with lowest flow accumulation. For different geomorphodynamical zones the threshold of IC where sediment transit turns into sediment accumulation has differ values: for example, -2.3 for colluvial fans and -2.5 for alluvial fans (p-value for differences significance « 0.01). Maximum values of CI (quantile: the top-95%) for accumulative positions again are -1.27 and -0.72. Its means, those accumulative processes areas with different mechanics of the deposition may be delineated with using non-constant CI values only. The potential of sediment flow connectivity modelling for high mountain isn’t exhausted, but its application needs wide discussion and calibration.
The study was supported by the Russian Science Foundation (project No. 19-17-00181).
How to cite: Kedich, A., Uspensky, M., Tsyplenkov, A., Kharchenko, S., and Golosov, V.: Sediment connectivity in the Koiyavgan glacier's cirques (Adyl-Su river basin, Caucasus, Russia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16175, https://doi.org/10.5194/egusphere-egu21-16175, 2021.
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The highland cirques mostly created by nivation and glacial exaration take large areas in mountains and have a significant role in the sediment transit of the basins. The approximate view on the connection of cirques and low levels in the sediment flow could be given with the sediment connectivity index analysis. We study the spatial distribution of the index for typical ice cirque – the Koiyavgan cirque near the join of the Main Caucasus Range and its offshoot (the Gumachy range). This area is located in the tops of the Adyl-Su valley (left side of the Baksan river basin). In August 2020, we got a high-resolution orthophoto image (13+ cm) and digital elevation model (27+ cm) from aerial photography. The territory located in the elevation range from 3230 to 4022 m. Geological conditions: gneiss, metamorphic shale and basic dark coloured igneous rocks. There is no developed vegetation cover. Typical post-glacial cirques topography includes (top-down): mountain tops, very steep bedrock slopes, colluvial footslopes and fans, cirques bottom (moraine ridges with dividing valleys, craters from melting of the in-moraine covered ice etc.) with fluvial, avalanche and creep post-shaping, and bottom surface break as analogue of riegels in glacial trough valleys. The connectivity index (CI) after Cavalli et al. [2013] is very dependent on initial DEM resolution, from the method for filling mistaken depressions, from window size for computing intermediate geomorphometric variables (e.g. roughness index), from choice in flow impedance variable, from area coverage and terrain diversity and others. We compute connectivity index with the parameters: 1) DEM resolution – 27 cm; 2) impedance variable – terrain roughness index (standard deviation of elevation) with window 7*7 cells; 3) standard filling method used in the ArcMap (filling local depression without any limitations on maximum depth); 4) range of impedance values before normalization (partially related to area coverage) is from 0 to 72 m. In the some buffers from the channel network the connectivity index generally grows in the top-down direction. Greatest spurt of the CI values relates to the cirques low border - the riegel (3300 m asl). There are two levels characterised with low values of the CI: 3550 m and 3750 m. The first one is backside of cirques bottom with relatively low flow accumulation area and low-moderate slopes (0-25°), the second one is mountain tops with high steep slopes, but with lowest flow accumulation. For different geomorphodynamical zones the threshold of IC where sediment transit turns into sediment accumulation has differ values: for example, -2.3 for colluvial fans and -2.5 for alluvial fans (p-value for differences significance « 0.01). Maximum values of CI (quantile: the top-95%) for accumulative positions again are -1.27 and -0.72. Its means, those accumulative processes areas with different mechanics of the deposition may be delineated with using non-constant CI values only. The potential of sediment flow connectivity modelling for high mountain isn’t exhausted, but its application needs wide discussion and calibration.
The study was supported by the Russian Science Foundation (project No. 19-17-00181).
How to cite: Kedich, A., Uspensky, M., Tsyplenkov, A., Kharchenko, S., and Golosov, V.: Sediment connectivity in the Koiyavgan glacier's cirques (Adyl-Su river basin, Caucasus, Russia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16175, https://doi.org/10.5194/egusphere-egu21-16175, 2021.
GM5.1 – Fluvial systems: Dynamics and interactions across scales
EGU21-4568 | vPICO presentations | GM5.1 | Highlight
Drivers of channel morphology in semi-alluvial boulder-bed streams & implications for river restorationRichard Mason and Lina Polvi
Research to understand the drivers of river form and processes has focussed on alluvial sand and gravel-bed channels. However, boulder-bed rivers are also an abundant channel type, particularly in previously glaciated and mountainous regions. Understanding boulder distribution in rivers is important because of their effects on channel hydraulics and sediment transport processes. Boulder-bed channels in low-relief, previously glaciated landscapes may be considered semi-alluvial since the boulders likely were not deposited by fluvial processes (unlike in e.g., step-pool mountain channels). However, the relative importance of glacial legacy sediment and fluvial processes as drivers of boulder-bed river morphology is poorly understood. This is especially true in northern Sweden where channel clearance for timber floating has resulted in the removal of boulders from most rivers. Restoration of these rivers involves the replacement of boulders but is challenged by a lack of geomorphological understanding.
This study aimed to quantify the morphological characteristics of northern Swedish boulder-bed streams and determine the association between fluvial and glacial legacy controls on these channels. We undertook a large-scale field campaign surveying 20 rivers (drainage area: 15 - 112 km2) that have not been cleared for timber floating. At each reach, we measured channel morphology using a total station over approximately 100 m river length, surveying the channel planform, thalweg and 5 cross sections. In addition, we measured the location, diameter and protrusion of every boulder (> D84) within each reach. We also conducted a survey of the size and density of boulders on the floodplain to compare to in-channel boulder distributions. We coupled this field campaign with analysis of digital elevation models, surficial geology, glacial landform maps, and hydrological data to investigate potential landscape controls on reach-scale geomorphology. Associations between drainage area, channel slope, width and D84 as well as longitudinal clustering of boulders into fluvial bed-forms would indicate fluvial rather than legacy glacial drivers.
Preliminary results show high variability in the morphology of reference sites, from low-gradient reaches with high floodplain connectivity to steep and narrow channels (Slope ranged 1.1 - 8.8%). D84 ranged from 0.4 m to 2.1 m with some sites having as many as 500 large boulders (> 1 m diameter) in a 100 m reach. D84 was not associated with channel slope and boulders were not clustered longitudinally in most reaches. This suggests that boulder spacing is the result of glacial legacy controls. These results are important for understanding geomorphic processes in boulder-bed channels and how channel form relates to reach- and landscape-scale controls. The relative importance of fluvial versus glacial legacy controls on boulder-bed channel morphology is also important to help restoration practitioners more accurately identify reference states of boulder-bed channels in previously glaciated landscapes.
How to cite: Mason, R. and Polvi, L.: Drivers of channel morphology in semi-alluvial boulder-bed streams & implications for river restoration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4568, https://doi.org/10.5194/egusphere-egu21-4568, 2021.
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Research to understand the drivers of river form and processes has focussed on alluvial sand and gravel-bed channels. However, boulder-bed rivers are also an abundant channel type, particularly in previously glaciated and mountainous regions. Understanding boulder distribution in rivers is important because of their effects on channel hydraulics and sediment transport processes. Boulder-bed channels in low-relief, previously glaciated landscapes may be considered semi-alluvial since the boulders likely were not deposited by fluvial processes (unlike in e.g., step-pool mountain channels). However, the relative importance of glacial legacy sediment and fluvial processes as drivers of boulder-bed river morphology is poorly understood. This is especially true in northern Sweden where channel clearance for timber floating has resulted in the removal of boulders from most rivers. Restoration of these rivers involves the replacement of boulders but is challenged by a lack of geomorphological understanding.
This study aimed to quantify the morphological characteristics of northern Swedish boulder-bed streams and determine the association between fluvial and glacial legacy controls on these channels. We undertook a large-scale field campaign surveying 20 rivers (drainage area: 15 - 112 km2) that have not been cleared for timber floating. At each reach, we measured channel morphology using a total station over approximately 100 m river length, surveying the channel planform, thalweg and 5 cross sections. In addition, we measured the location, diameter and protrusion of every boulder (> D84) within each reach. We also conducted a survey of the size and density of boulders on the floodplain to compare to in-channel boulder distributions. We coupled this field campaign with analysis of digital elevation models, surficial geology, glacial landform maps, and hydrological data to investigate potential landscape controls on reach-scale geomorphology. Associations between drainage area, channel slope, width and D84 as well as longitudinal clustering of boulders into fluvial bed-forms would indicate fluvial rather than legacy glacial drivers.
Preliminary results show high variability in the morphology of reference sites, from low-gradient reaches with high floodplain connectivity to steep and narrow channels (Slope ranged 1.1 - 8.8%). D84 ranged from 0.4 m to 2.1 m with some sites having as many as 500 large boulders (> 1 m diameter) in a 100 m reach. D84 was not associated with channel slope and boulders were not clustered longitudinally in most reaches. This suggests that boulder spacing is the result of glacial legacy controls. These results are important for understanding geomorphic processes in boulder-bed channels and how channel form relates to reach- and landscape-scale controls. The relative importance of fluvial versus glacial legacy controls on boulder-bed channel morphology is also important to help restoration practitioners more accurately identify reference states of boulder-bed channels in previously glaciated landscapes.
How to cite: Mason, R. and Polvi, L.: Drivers of channel morphology in semi-alluvial boulder-bed streams & implications for river restoration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4568, https://doi.org/10.5194/egusphere-egu21-4568, 2021.
EGU21-719 | vPICO presentations | GM5.1
Interpreting reach-scale classifications and the role of spatial-morphological variables in river channel mapping using machine learning algorithmsAdeyemi Olusola and Adetoye Faniran
Over the years, there has been tremendous growth in the literature as regards river channel classifications, however, very few studies have been able to engage the use of remote sensing products in channel classification at the reach-scale level especially by combining reflections from satellite sensors with channel morphological variables. This study aims to identify discriminating spatio-morphological variables using machine learning algorithms and classify site-specific channel types at the reach scale. Each reach was broadly classified based on valley settings (confined, partly confined and unconfined) and channel types (alluvial or bedrock). However, variations and site observations were recorded for site-specific classification purposes. For each reach, Global Positioning System devices were used to geo-locate their endpoints. Standard field instruments were used for cross-sectional measurements and established hydraulic equations for the derived variables. A total of 249 points across 83 reaches were sampled during the fieldwork. Landsat 8 and Sentinel-1 bands were retrieved for days the fieldwork was carried out/for days close to those dates using Google Earth Engine (GEE) platform. Hierarchical cluster analysis, HCA, using Ward’s linkages was used to provide a classification for the channel types. For the identification of important variables in predicting channel unit types, the random-forest - recursive feature elimination (RF-RFE) algorithm was used using the rfe() function. To identify the best machine learning algorithm, random-forest (rf), support vector machines (svm), multivariate adaptive regression spline (mars) extreme gradient boosting (xgb) and adaptive boosting (adaboost) were used on the training and test data to identify the best performing algorithm. The rfe() feature selection identified five (5) variables that can significantly help in channel unit type identification. The top five variables are dimensionless stream power, slope, width, wetted perimeter and Band 4. Using ROC curve, sensitivity, and specificity, the mars model has the highest ROC curve. Hence, it appears to be the best performing out of the five. However, if the argument is to be based on positive prediction, then any of the models except adaboost will be preferred given their high sensitivity. The HCA using illustrated the clustering structure of the studied reaches by producing five distinct channel classification types distinguished based on width-depth ratio values (high and low). The five distinct channel types are listed as M1e, M5e, B1, E5b, and E. These codings are based partly on Rosgen’s classification while, the capital letters (M, B and E) represent mixed channels, bedrock with moderate width-depth ratio and alluvial channels with low width-depth ratio respectively. Numbers 1 and 5 represent bedrocks and sandy beds based on slope variation respectively. The identified channel unit types are a result of the underlying lithology, process-form dynamics and confinement. As streams are expected to respond differently to shocks and recover from damages, it becomes essential to understand these differences in classification which will go a long way in establishing watershed and streamside management guidelines.
How to cite: Olusola, A. and Faniran, A.: Interpreting reach-scale classifications and the role of spatial-morphological variables in river channel mapping using machine learning algorithms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-719, https://doi.org/10.5194/egusphere-egu21-719, 2021.
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Over the years, there has been tremendous growth in the literature as regards river channel classifications, however, very few studies have been able to engage the use of remote sensing products in channel classification at the reach-scale level especially by combining reflections from satellite sensors with channel morphological variables. This study aims to identify discriminating spatio-morphological variables using machine learning algorithms and classify site-specific channel types at the reach scale. Each reach was broadly classified based on valley settings (confined, partly confined and unconfined) and channel types (alluvial or bedrock). However, variations and site observations were recorded for site-specific classification purposes. For each reach, Global Positioning System devices were used to geo-locate their endpoints. Standard field instruments were used for cross-sectional measurements and established hydraulic equations for the derived variables. A total of 249 points across 83 reaches were sampled during the fieldwork. Landsat 8 and Sentinel-1 bands were retrieved for days the fieldwork was carried out/for days close to those dates using Google Earth Engine (GEE) platform. Hierarchical cluster analysis, HCA, using Ward’s linkages was used to provide a classification for the channel types. For the identification of important variables in predicting channel unit types, the random-forest - recursive feature elimination (RF-RFE) algorithm was used using the rfe() function. To identify the best machine learning algorithm, random-forest (rf), support vector machines (svm), multivariate adaptive regression spline (mars) extreme gradient boosting (xgb) and adaptive boosting (adaboost) were used on the training and test data to identify the best performing algorithm. The rfe() feature selection identified five (5) variables that can significantly help in channel unit type identification. The top five variables are dimensionless stream power, slope, width, wetted perimeter and Band 4. Using ROC curve, sensitivity, and specificity, the mars model has the highest ROC curve. Hence, it appears to be the best performing out of the five. However, if the argument is to be based on positive prediction, then any of the models except adaboost will be preferred given their high sensitivity. The HCA using illustrated the clustering structure of the studied reaches by producing five distinct channel classification types distinguished based on width-depth ratio values (high and low). The five distinct channel types are listed as M1e, M5e, B1, E5b, and E. These codings are based partly on Rosgen’s classification while, the capital letters (M, B and E) represent mixed channels, bedrock with moderate width-depth ratio and alluvial channels with low width-depth ratio respectively. Numbers 1 and 5 represent bedrocks and sandy beds based on slope variation respectively. The identified channel unit types are a result of the underlying lithology, process-form dynamics and confinement. As streams are expected to respond differently to shocks and recover from damages, it becomes essential to understand these differences in classification which will go a long way in establishing watershed and streamside management guidelines.
How to cite: Olusola, A. and Faniran, A.: Interpreting reach-scale classifications and the role of spatial-morphological variables in river channel mapping using machine learning algorithms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-719, https://doi.org/10.5194/egusphere-egu21-719, 2021.
EGU21-1287 | vPICO presentations | GM5.1
Morphodynamics of active meandering rivers in a hierarchy of spatial and temporal scalesJanet Hooke
Active meandering rivers have the advantage of exhibiting morphodynamic changes at such a rate that changes are detectable on a range of timescales, from event, through decadal, to centennial. The evidence from river reaches that have been investigated directly for 40 years by various methods is used to examine the morphodynamics over differing spatial and temporal scales. Several questions can be addressed, including: what channel changes are produced by different events, discharge periods and sequences; how do events and phases combine to produce changes in position and in morphology; to what extent are such changes coherent, systematic and predictable. The combination of evidence from detailed cross-sectional surveys, field mapping, drone and aerial photographic surveys and use of historical maps demonstrates how the morphodynamics at different scales combine and interact. Analysis indicates some systematic changes at cross-sectional and bend scale but contrasts between different reaches, bends and within bends, and reveals complex patterns and lags in propagation of change. Survey and monitoring requirements to detect and understand the interactions are identified. Research into these active meandering rivers may be indicative and helpful for our wider understanding of less dynamic rivers, where changes are less easily detected. It raises the question of whether the mechanisms are similar in more stable rivers and reaches.
How to cite: Hooke, J.: Morphodynamics of active meandering rivers in a hierarchy of spatial and temporal scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1287, https://doi.org/10.5194/egusphere-egu21-1287, 2021.
Active meandering rivers have the advantage of exhibiting morphodynamic changes at such a rate that changes are detectable on a range of timescales, from event, through decadal, to centennial. The evidence from river reaches that have been investigated directly for 40 years by various methods is used to examine the morphodynamics over differing spatial and temporal scales. Several questions can be addressed, including: what channel changes are produced by different events, discharge periods and sequences; how do events and phases combine to produce changes in position and in morphology; to what extent are such changes coherent, systematic and predictable. The combination of evidence from detailed cross-sectional surveys, field mapping, drone and aerial photographic surveys and use of historical maps demonstrates how the morphodynamics at different scales combine and interact. Analysis indicates some systematic changes at cross-sectional and bend scale but contrasts between different reaches, bends and within bends, and reveals complex patterns and lags in propagation of change. Survey and monitoring requirements to detect and understand the interactions are identified. Research into these active meandering rivers may be indicative and helpful for our wider understanding of less dynamic rivers, where changes are less easily detected. It raises the question of whether the mechanisms are similar in more stable rivers and reaches.
How to cite: Hooke, J.: Morphodynamics of active meandering rivers in a hierarchy of spatial and temporal scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1287, https://doi.org/10.5194/egusphere-egu21-1287, 2021.
EGU21-7957 | vPICO presentations | GM5.1
The effect of flood events on the altimetric response of river alternate barsMattia Carlin, Marco Redolfi, and Marco Tubino
Alternate bars are large bedforms, characterized by an ordered sequence of scour and deposition zones, which often appear in rivers. It is well proved by many experimental, theoretical and numerical works that the formation of migrating alternate bars results form an intrinsic instability mechanism occurring when the width-to-depth ratio of the channel is larger than a critical threshold. Although a large amount of literature is available to describe equilibrium bar properties under steady flow conditions, much less information exists about the evolution of bars when flow discharge is variable in time. In a recent work we investigated how the long-term, average properties of bars respond to changes of the hydrological regime. This average state represents the net result of a multitude of flood events, each of them producing a different morphological alteration. However, a systematic description of how changes of the bar properties depend on the characteristics of the individual floods is still missing, as existing studies are limited to a small number of flood events, not sufficient to make a statistical description of the riverbed response. In this work, we aim at studying the time evolution of the bar amplitude in a relatively straight, channelized reach of a gravel bed river. Specifically, we considered a 10 km-long reach of the Alpine Rhine River, for which a detailed record of flow stages is available for the period from 1984 to 2010. This is accomplished by modelling the bed evolution through the theoretically-based model of Colombini et al. (1987), here applied by considering a time-varying basic flow and numerically integrating the bar amplitude. Compared with classical approaches based on numerically solving the two-dimensional shallow-water equations, our procedure allows for calculating the bar response over long periods of time with a very low computational cost. This enables for modelling different scenarios of hydrological alterations, due to dam constructions or climate changes, and to statistically analyse the expected impact on bar evolution. Assuming that bars cannot evolve when the flow is too low to fully submerge the bar crests, we identify 200 morphologically-active flood events, covering about 1.1% of the total duration of the flow series. Model results reveal that moderate flow events tend to increase the bar amplitude, while larger floods reduce the bar height. However, the value of the peak discharge alone is not sufficient to explain the morphological changes, as an important (and opposite) role is also played by the duration of the events. Specifically, longer floods tend to promote an increase of the bar height during the receding phase, which implies that a strong reduction of the bar amplitude requires intense, but relatively short flood events.
How to cite: Carlin, M., Redolfi, M., and Tubino, M.: The effect of flood events on the altimetric response of river alternate bars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7957, https://doi.org/10.5194/egusphere-egu21-7957, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Alternate bars are large bedforms, characterized by an ordered sequence of scour and deposition zones, which often appear in rivers. It is well proved by many experimental, theoretical and numerical works that the formation of migrating alternate bars results form an intrinsic instability mechanism occurring when the width-to-depth ratio of the channel is larger than a critical threshold. Although a large amount of literature is available to describe equilibrium bar properties under steady flow conditions, much less information exists about the evolution of bars when flow discharge is variable in time. In a recent work we investigated how the long-term, average properties of bars respond to changes of the hydrological regime. This average state represents the net result of a multitude of flood events, each of them producing a different morphological alteration. However, a systematic description of how changes of the bar properties depend on the characteristics of the individual floods is still missing, as existing studies are limited to a small number of flood events, not sufficient to make a statistical description of the riverbed response. In this work, we aim at studying the time evolution of the bar amplitude in a relatively straight, channelized reach of a gravel bed river. Specifically, we considered a 10 km-long reach of the Alpine Rhine River, for which a detailed record of flow stages is available for the period from 1984 to 2010. This is accomplished by modelling the bed evolution through the theoretically-based model of Colombini et al. (1987), here applied by considering a time-varying basic flow and numerically integrating the bar amplitude. Compared with classical approaches based on numerically solving the two-dimensional shallow-water equations, our procedure allows for calculating the bar response over long periods of time with a very low computational cost. This enables for modelling different scenarios of hydrological alterations, due to dam constructions or climate changes, and to statistically analyse the expected impact on bar evolution. Assuming that bars cannot evolve when the flow is too low to fully submerge the bar crests, we identify 200 morphologically-active flood events, covering about 1.1% of the total duration of the flow series. Model results reveal that moderate flow events tend to increase the bar amplitude, while larger floods reduce the bar height. However, the value of the peak discharge alone is not sufficient to explain the morphological changes, as an important (and opposite) role is also played by the duration of the events. Specifically, longer floods tend to promote an increase of the bar height during the receding phase, which implies that a strong reduction of the bar amplitude requires intense, but relatively short flood events.
How to cite: Carlin, M., Redolfi, M., and Tubino, M.: The effect of flood events on the altimetric response of river alternate bars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7957, https://doi.org/10.5194/egusphere-egu21-7957, 2021.
EGU21-12728 * | vPICO presentations | GM5.1 | Highlight
Meandering channels over ice: Cooler and unique?Roberto Fernández
Experimental work on small-scale meltwater meandering channels over ice and field observations have identified similarities and differences between their planform morphologies and those of meandering channels in other media (e.g. alluvial, bedrock). Qualitatively and quantitatively, planform characteristics, including sinuosity, wavelength-to-width ratios, coefficient of skewness and fatness, suggest that most meandering channels behave in certain ways and within certain ranges. However, what makes meltwater meandering channels over ice unique? In this contribution, I highlight the different aspects that set meltwater meandering channels over ice apart from meandering channels in other media and share ongoing work focusing in their planform morphologies, curvature signals, and cross section geometry.
How to cite: Fernández, R.: Meandering channels over ice: Cooler and unique?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12728, https://doi.org/10.5194/egusphere-egu21-12728, 2021.
Experimental work on small-scale meltwater meandering channels over ice and field observations have identified similarities and differences between their planform morphologies and those of meandering channels in other media (e.g. alluvial, bedrock). Qualitatively and quantitatively, planform characteristics, including sinuosity, wavelength-to-width ratios, coefficient of skewness and fatness, suggest that most meandering channels behave in certain ways and within certain ranges. However, what makes meltwater meandering channels over ice unique? In this contribution, I highlight the different aspects that set meltwater meandering channels over ice apart from meandering channels in other media and share ongoing work focusing in their planform morphologies, curvature signals, and cross section geometry.
How to cite: Fernández, R.: Meandering channels over ice: Cooler and unique?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12728, https://doi.org/10.5194/egusphere-egu21-12728, 2021.
EGU21-8178 | vPICO presentations | GM5.1
Analysing the intrinsic time scale of river bifurcationsGabriele Barile, Marco Redolfi, and Marco Tubino
River bifurcations play a crucial role in the morphodynamics of multi-thread channel systems such as braided or anastomosed rivers, deltas and alluvial fans, as they guide the downstream distribution of water and sediment fluxes. Several experimental and theoretical studies have highlighted the unstable character of bifurcations, which tend to produce a differential erosion/deposition in the downstream channels, even in the case of symmetric planform configuration and boundary conditions. This leads to equilibrium states where the flow distribution can be highly unbalanced, depending on the channel width-to-depth ratio. The analyses performed so far have mainly focused on equilibrium configurations, while little information exists about the time evolution of the instability process. In particular, there is no systematic analysis of how the bifurcation timescale depends on the controlling parameters, such as the channel aspect ratio, and the length of the downstream channels. Evaluation of this “intrinsic” time scale is fundamental to study the response of river bifurcations to time variations of any “external” factor that influences the bifurcation dynamics, such as the water discharge, the downstream conditions, or the presence of migrating bedforms. In this work we consider a simple bifurcation, consisting of a straight channel with mobile bed but fixed banks, which splits in two bifurcates that diverge with the same angle. We employ a 1-D shallow-water model for the upstream channel and downstream bifurcates, which are connected by means of the nodal point relation proposed by Bolla Pittaluga et al. (2013). We then numerically analyse the development of the bifurcations instability, starting from an initially-small perturbation of the bed elevation. Finally, we extensively investigate the effect of the key controlling parameters, including the model calibration coefficients, also allowing them to vary in time. The evolution of water discharge asymmetry shows a first exponential growth stage, followed by an asymptotic behaviour that leads to the equilibrium configuration. Model results reveal the key role of the width-to-depth ratio in determining the speed of the bifurcation evolution. Specifically, the evolution is very slow when the system is close to marginal stability conditions, while it becomes increasingly fast when increasing the width-to-depth ratio. Moreover, the timescale of the bifurcation increases with the length of the downstream channel, unless their length-to-depth ratio is sufficiently high.
How to cite: Barile, G., Redolfi, M., and Tubino, M.: Analysing the intrinsic time scale of river bifurcations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8178, https://doi.org/10.5194/egusphere-egu21-8178, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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River bifurcations play a crucial role in the morphodynamics of multi-thread channel systems such as braided or anastomosed rivers, deltas and alluvial fans, as they guide the downstream distribution of water and sediment fluxes. Several experimental and theoretical studies have highlighted the unstable character of bifurcations, which tend to produce a differential erosion/deposition in the downstream channels, even in the case of symmetric planform configuration and boundary conditions. This leads to equilibrium states where the flow distribution can be highly unbalanced, depending on the channel width-to-depth ratio. The analyses performed so far have mainly focused on equilibrium configurations, while little information exists about the time evolution of the instability process. In particular, there is no systematic analysis of how the bifurcation timescale depends on the controlling parameters, such as the channel aspect ratio, and the length of the downstream channels. Evaluation of this “intrinsic” time scale is fundamental to study the response of river bifurcations to time variations of any “external” factor that influences the bifurcation dynamics, such as the water discharge, the downstream conditions, or the presence of migrating bedforms. In this work we consider a simple bifurcation, consisting of a straight channel with mobile bed but fixed banks, which splits in two bifurcates that diverge with the same angle. We employ a 1-D shallow-water model for the upstream channel and downstream bifurcates, which are connected by means of the nodal point relation proposed by Bolla Pittaluga et al. (2013). We then numerically analyse the development of the bifurcations instability, starting from an initially-small perturbation of the bed elevation. Finally, we extensively investigate the effect of the key controlling parameters, including the model calibration coefficients, also allowing them to vary in time. The evolution of water discharge asymmetry shows a first exponential growth stage, followed by an asymptotic behaviour that leads to the equilibrium configuration. Model results reveal the key role of the width-to-depth ratio in determining the speed of the bifurcation evolution. Specifically, the evolution is very slow when the system is close to marginal stability conditions, while it becomes increasingly fast when increasing the width-to-depth ratio. Moreover, the timescale of the bifurcation increases with the length of the downstream channel, unless their length-to-depth ratio is sufficiently high.
How to cite: Barile, G., Redolfi, M., and Tubino, M.: Analysing the intrinsic time scale of river bifurcations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8178, https://doi.org/10.5194/egusphere-egu21-8178, 2021.
EGU21-8017 | vPICO presentations | GM5.1
Morphodynamic stability and characteristic length scales of bifurcations and confluences loopsNiccolò Ragno, Marco Redolfi, and Marco Tubino
The morphodynamics of multi-thread fluvial environments like braided and anastomosing rivers is fundamentally driven by the continuous concatenation of channel bifurcations and confluences, which govern the distribution of flow and sediment among the different branches that are reconnecting further downstream. Almost all studies performed to date consider the two processes separately, although they frequently appear as closely interconnected. In this work, we tackle the problem of analyzing the coupled morphodynamics of such bifurcation-confluence systems by studying the equilibrium and stability conditions of a channel loop, where flow splits into two secondary anabranches that rejoin after a prescribed distance. Through the formulation of a novel theoretical model for erodible bed confluences based on the momentum balance on two distinct control volumes, we show that the dominating anabranch (i.e. that carrying more water and sediment) is subject to an increase of the water surface elevation that is proportional to the square of the Froude number. This increase in water surface elevation tends to reduce the slope of the dominating branch, which produces a negative feedback that tends to stabilize the bifurcation-confluence system. A linear analysis of the coupled model reveals that the stabilizing effect of the confluence depends on the ratio between the length of the connecting channels and the average water depth, independently of the channel slope and Froude number. Furthermore, the effect of the confluence is potentially able to stabilize the channel loop in conditions where the classic stabilizing mechanism at the bifurcation (i.e. the topographical effect related to the gravitational pull on the sediment transport) is very weak, as expected when most of the sediment is transported in suspension. The identification of a characteristic length scale that produces a coupling between the confluences and bifurcations opens intriguing possibilities for interpreting the self-adjustment of the planform scale of natural multi-thread rivers.
How to cite: Ragno, N., Redolfi, M., and Tubino, M.: Morphodynamic stability and characteristic length scales of bifurcations and confluences loops, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8017, https://doi.org/10.5194/egusphere-egu21-8017, 2021.
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The morphodynamics of multi-thread fluvial environments like braided and anastomosing rivers is fundamentally driven by the continuous concatenation of channel bifurcations and confluences, which govern the distribution of flow and sediment among the different branches that are reconnecting further downstream. Almost all studies performed to date consider the two processes separately, although they frequently appear as closely interconnected. In this work, we tackle the problem of analyzing the coupled morphodynamics of such bifurcation-confluence systems by studying the equilibrium and stability conditions of a channel loop, where flow splits into two secondary anabranches that rejoin after a prescribed distance. Through the formulation of a novel theoretical model for erodible bed confluences based on the momentum balance on two distinct control volumes, we show that the dominating anabranch (i.e. that carrying more water and sediment) is subject to an increase of the water surface elevation that is proportional to the square of the Froude number. This increase in water surface elevation tends to reduce the slope of the dominating branch, which produces a negative feedback that tends to stabilize the bifurcation-confluence system. A linear analysis of the coupled model reveals that the stabilizing effect of the confluence depends on the ratio between the length of the connecting channels and the average water depth, independently of the channel slope and Froude number. Furthermore, the effect of the confluence is potentially able to stabilize the channel loop in conditions where the classic stabilizing mechanism at the bifurcation (i.e. the topographical effect related to the gravitational pull on the sediment transport) is very weak, as expected when most of the sediment is transported in suspension. The identification of a characteristic length scale that produces a coupling between the confluences and bifurcations opens intriguing possibilities for interpreting the self-adjustment of the planform scale of natural multi-thread rivers.
How to cite: Ragno, N., Redolfi, M., and Tubino, M.: Morphodynamic stability and characteristic length scales of bifurcations and confluences loops, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8017, https://doi.org/10.5194/egusphere-egu21-8017, 2021.
EGU21-7478 | vPICO presentations | GM5.1
Exploring the 4D scales of vegetation-morphological interactions along a river corridor using repeat UAV Laser Scanning (ULS), multispectral imagery, and a functional traits framework.Chris Tomsett and Julian Leyland
Interactions between riparian vegetation and river morphology are complex as they are often co-dependent, highly dynamic, and vary across both space and time. Vegetation diversity can be partially attributed to factors such as flood regimes and morphology, whilst simultaneously influencing the flow of water and sediment, ultimately impacting morphology and floodplain connectivity. As such, the importance of vegetation within the river corridor is well recognised and has been the subject of a considerable volume of research. However, within ecogeomorphology, most studies to date have been scale invariant, focusing either on characterisation of fine scale hydraulic roughness (e.g. using Terrestrial Laser Scanning; TLS) or on >reach scale patterns of riparian vegetation (using airborne or satellite imagery). Similarly, less attention has been paid to the temporal dynamics of vegetation beyond some appreciation of seasonality in controlling flow dynamics. This leaves a number of unresolved questions relating to the nested spatial and temporal (i.e. 4-dimensional; 4D) interactions of riparian vegetation and river flow.
In this study we seek to establish the temporal and spatial scales of riparian vegetation interaction within a river corridor using a traits based framework. Traits based research characterises plants with similar functional traits into guilds (groups) as opposed to by species or types, and as such provides a more useful basis to group vegetation according to the potential geomorphic impact that they exhibit. Traits based research for ecogeomorphic processes is relatively new in fluvial geomorphology, but has shown promise in its applicability, albeit existing applications are yet to investigate the temporal changes in vegetation. The need for extensive ground survey currently limits the application of traits based methods at reach scale and greater, highlighting the requirement for an approach that is able to classify a range of vegetation sizes and types into appropriate guilds.
Using a novel ULS and multispectral imaging systems, we have collected repeat high resolution (~1000 points per m3) surveys over a 1 km reach of the River Teme, UK, which has a wide variety of seasonally dynamic riparian vegetation. For each survey we use the point cloud data and multispectral imagery to classify vegetation into guilds. We use these in conjunction with the morphological data from the survey to create spatially varying surfaces of ecogeomorphic interactions, allowing us to establish links between guild coverage and morphological evolution across the reach throughout the year. The results show that vegetation-morphological co-evolution exists across scales and that high resolution survey methods are highly beneficial for resolving such interactions. The methods are designed to be transferable to other eco-geomorphic domains in any morpho-climatic regions, highlighting the flexibility and potential of a high resolution 4D traits based approach.
How to cite: Tomsett, C. and Leyland, J.: Exploring the 4D scales of vegetation-morphological interactions along a river corridor using repeat UAV Laser Scanning (ULS), multispectral imagery, and a functional traits framework., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7478, https://doi.org/10.5194/egusphere-egu21-7478, 2021.
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Interactions between riparian vegetation and river morphology are complex as they are often co-dependent, highly dynamic, and vary across both space and time. Vegetation diversity can be partially attributed to factors such as flood regimes and morphology, whilst simultaneously influencing the flow of water and sediment, ultimately impacting morphology and floodplain connectivity. As such, the importance of vegetation within the river corridor is well recognised and has been the subject of a considerable volume of research. However, within ecogeomorphology, most studies to date have been scale invariant, focusing either on characterisation of fine scale hydraulic roughness (e.g. using Terrestrial Laser Scanning; TLS) or on >reach scale patterns of riparian vegetation (using airborne or satellite imagery). Similarly, less attention has been paid to the temporal dynamics of vegetation beyond some appreciation of seasonality in controlling flow dynamics. This leaves a number of unresolved questions relating to the nested spatial and temporal (i.e. 4-dimensional; 4D) interactions of riparian vegetation and river flow.
In this study we seek to establish the temporal and spatial scales of riparian vegetation interaction within a river corridor using a traits based framework. Traits based research characterises plants with similar functional traits into guilds (groups) as opposed to by species or types, and as such provides a more useful basis to group vegetation according to the potential geomorphic impact that they exhibit. Traits based research for ecogeomorphic processes is relatively new in fluvial geomorphology, but has shown promise in its applicability, albeit existing applications are yet to investigate the temporal changes in vegetation. The need for extensive ground survey currently limits the application of traits based methods at reach scale and greater, highlighting the requirement for an approach that is able to classify a range of vegetation sizes and types into appropriate guilds.
Using a novel ULS and multispectral imaging systems, we have collected repeat high resolution (~1000 points per m3) surveys over a 1 km reach of the River Teme, UK, which has a wide variety of seasonally dynamic riparian vegetation. For each survey we use the point cloud data and multispectral imagery to classify vegetation into guilds. We use these in conjunction with the morphological data from the survey to create spatially varying surfaces of ecogeomorphic interactions, allowing us to establish links between guild coverage and morphological evolution across the reach throughout the year. The results show that vegetation-morphological co-evolution exists across scales and that high resolution survey methods are highly beneficial for resolving such interactions. The methods are designed to be transferable to other eco-geomorphic domains in any morpho-climatic regions, highlighting the flexibility and potential of a high resolution 4D traits based approach.
How to cite: Tomsett, C. and Leyland, J.: Exploring the 4D scales of vegetation-morphological interactions along a river corridor using repeat UAV Laser Scanning (ULS), multispectral imagery, and a functional traits framework., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7478, https://doi.org/10.5194/egusphere-egu21-7478, 2021.
EGU21-1465 | vPICO presentations | GM5.1
Effect of bridge pier induced turbulence on vegetated meander river morphologySuresh Modalavalasa, Vinay Chembolu, Ketan Kumar Nandi, Vinayak Kulkarni, and Subashisa Dutta
A natural riverine corridor has several curls based on its physical and geomorphological characteristics. In most of the scenarios, the bridge construction on a meandering channel aligns along the convergent section. The enhanced secondary flow at convergent sections and the effect of meandering curvature bring the complexity in river turbulent characteristics. This effect may become predominant inside the main channel with variability in size and shape of the bridge pier. The present work discusses the turbulent structures in the main channel due to the variability in pier diameter (1inch and 2 inch ϕ) and a number of bridge piers on floodplain with inclusive of vegetation. Three-dimensional flow vertical and transverse velocity measurements were carried with acoustic Doppler velocimeter (ADV) 100Hz, at apex cross-section in a low sinuous channel. The results of the analysis showed that the combined effect of pier and vegetation on floodplain significantly altered the shear layer mechanisms in the channel with varying flow patterns. The comparison of the difference in secondary velocities between the pier with 1 inch and 2 inch ϕ is 57% more in the case of lesser diameter pier. Further, the effect of size and number of piers on transverse velocity, Reynold’s shear stress is more susceptible to the mainstream. The convergence induced contraction of the meandering channel along with the bridge pier on its floodplain is observed to affect the turbulent structures formed in the main channel.
How to cite: Modalavalasa, S., Chembolu, V., Nandi, K. K., Kulkarni, V., and Dutta, S.: Effect of bridge pier induced turbulence on vegetated meander river morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1465, https://doi.org/10.5194/egusphere-egu21-1465, 2021.
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A natural riverine corridor has several curls based on its physical and geomorphological characteristics. In most of the scenarios, the bridge construction on a meandering channel aligns along the convergent section. The enhanced secondary flow at convergent sections and the effect of meandering curvature bring the complexity in river turbulent characteristics. This effect may become predominant inside the main channel with variability in size and shape of the bridge pier. The present work discusses the turbulent structures in the main channel due to the variability in pier diameter (1inch and 2 inch ϕ) and a number of bridge piers on floodplain with inclusive of vegetation. Three-dimensional flow vertical and transverse velocity measurements were carried with acoustic Doppler velocimeter (ADV) 100Hz, at apex cross-section in a low sinuous channel. The results of the analysis showed that the combined effect of pier and vegetation on floodplain significantly altered the shear layer mechanisms in the channel with varying flow patterns. The comparison of the difference in secondary velocities between the pier with 1 inch and 2 inch ϕ is 57% more in the case of lesser diameter pier. Further, the effect of size and number of piers on transverse velocity, Reynold’s shear stress is more susceptible to the mainstream. The convergence induced contraction of the meandering channel along with the bridge pier on its floodplain is observed to affect the turbulent structures formed in the main channel.
How to cite: Modalavalasa, S., Chembolu, V., Nandi, K. K., Kulkarni, V., and Dutta, S.: Effect of bridge pier induced turbulence on vegetated meander river morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1465, https://doi.org/10.5194/egusphere-egu21-1465, 2021.
EGU21-10900 | vPICO presentations | GM5.1
Turbulence Scale in Compound ChannelJyotirmoy Barman, Jyotismita Taye, and Bimlesh Kumar
The study of turbulence in a compound channel would address the nature of sedmient transport and bank erosion activity. The study would also give insights of embankment and levee breaches at the time of high flood. Experimental investigations were conducted on two compound channels of 310 and 450 bank angle in the laboratory flume to study the turbulece scale. Velocity data were recorded with Nortek Velocimeter at seven different locations (3 locations at the upstream, 3 locations at the downstream and 1 location at the middle) of the compound channel. Turbulence scale like Taylor microscale (λT) estimates the length scale of the inertial sub- range. The Taylor scale is calculated as:
The Taylor microscale analysis showed dominance in the main channel for 450 bank angle as compared to 310 bank angle. In the location of slope midpoint and floodplain region of the compound channel, Taylor microscale was more dominant for 310 bank angle. Another important observation in both the compound channels (310 and 450 bank angle) is the dominance of Taylor microscale at the upstream section of the channel as compared to the downstream part of the channel. The results from the study would help us to get a better understanding of the role of turbulence in the morphological changes in a compound channel with different bank angles.
How to cite: Barman, J., Taye, J., and Kumar, B.: Turbulence Scale in Compound Channel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10900, https://doi.org/10.5194/egusphere-egu21-10900, 2021.
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The study of turbulence in a compound channel would address the nature of sedmient transport and bank erosion activity. The study would also give insights of embankment and levee breaches at the time of high flood. Experimental investigations were conducted on two compound channels of 310 and 450 bank angle in the laboratory flume to study the turbulece scale. Velocity data were recorded with Nortek Velocimeter at seven different locations (3 locations at the upstream, 3 locations at the downstream and 1 location at the middle) of the compound channel. Turbulence scale like Taylor microscale (λT) estimates the length scale of the inertial sub- range. The Taylor scale is calculated as:
The Taylor microscale analysis showed dominance in the main channel for 450 bank angle as compared to 310 bank angle. In the location of slope midpoint and floodplain region of the compound channel, Taylor microscale was more dominant for 310 bank angle. Another important observation in both the compound channels (310 and 450 bank angle) is the dominance of Taylor microscale at the upstream section of the channel as compared to the downstream part of the channel. The results from the study would help us to get a better understanding of the role of turbulence in the morphological changes in a compound channel with different bank angles.
How to cite: Barman, J., Taye, J., and Kumar, B.: Turbulence Scale in Compound Channel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10900, https://doi.org/10.5194/egusphere-egu21-10900, 2021.
EGU21-1630 | vPICO presentations | GM5.1
Estimation of Bed Material Load using Artificial Intelligence TechniquesLaxman Rathod, Bandita Barman, and Bimlesh Kumar
Estimation of sediment transport has significant implementation on water resources and hydraulic engineering. Transport of sediment is affected by flow and sediment properties and also climatic variation of the region. To examine the behaviour of sediment transport, wide range of experiments have been performed in laboratories. Most of the developed sediment transport formulations are empirical or semi empirical in nature. These days, the development of computer-aided programs such as MATLAB has opened the way for researchers to quickly study the generation mechanism. The “Artificial Neural Networks (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS)” can be used widely for developing sediment model. In this research, Feed Forward Back Propagation (FFBP) sort of ANN and Hybrid type based on the Sugeno approach of ANFIS is used to develop a model for bed material load transport using parameters like “channel discharge, width of the channel, flow depth, friction/energy slope, mean size of sediment, bed shear stress, critical shear stress, gradation coefficient of the sediment particles, specific gravity, and viscosity”. Subsequently, the relationship between the expected and observed values is presented. The proposed approach showed superior results based on various statistical parameters, like the coefficient of determination (R2), Nash-Sutcliffe coefficient (NSE), Root mean square error (RMSE) and Mean absolute error (MAE). Correlation (R2), higher than (~0.90) indicates that ANN and ANFIS are compatible and capable of measuring the total bed material load.
Keywords: Sediment transport, Bed material Load, ANFIS, ANN, FFBP
How to cite: Rathod, L., Barman, B., and Kumar, B.: Estimation of Bed Material Load using Artificial Intelligence Techniques, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1630, https://doi.org/10.5194/egusphere-egu21-1630, 2021.
Estimation of sediment transport has significant implementation on water resources and hydraulic engineering. Transport of sediment is affected by flow and sediment properties and also climatic variation of the region. To examine the behaviour of sediment transport, wide range of experiments have been performed in laboratories. Most of the developed sediment transport formulations are empirical or semi empirical in nature. These days, the development of computer-aided programs such as MATLAB has opened the way for researchers to quickly study the generation mechanism. The “Artificial Neural Networks (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS)” can be used widely for developing sediment model. In this research, Feed Forward Back Propagation (FFBP) sort of ANN and Hybrid type based on the Sugeno approach of ANFIS is used to develop a model for bed material load transport using parameters like “channel discharge, width of the channel, flow depth, friction/energy slope, mean size of sediment, bed shear stress, critical shear stress, gradation coefficient of the sediment particles, specific gravity, and viscosity”. Subsequently, the relationship between the expected and observed values is presented. The proposed approach showed superior results based on various statistical parameters, like the coefficient of determination (R2), Nash-Sutcliffe coefficient (NSE), Root mean square error (RMSE) and Mean absolute error (MAE). Correlation (R2), higher than (~0.90) indicates that ANN and ANFIS are compatible and capable of measuring the total bed material load.
Keywords: Sediment transport, Bed material Load, ANFIS, ANN, FFBP
How to cite: Rathod, L., Barman, B., and Kumar, B.: Estimation of Bed Material Load using Artificial Intelligence Techniques, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1630, https://doi.org/10.5194/egusphere-egu21-1630, 2021.
EGU21-2141 | vPICO presentations | GM5.1
Width control on event scale bedload dynamics in bedrock-confined channelsKristen Cook, Jens Turowski, and Niels Hovius
In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing, and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory, and numerical modeling to address this gap. Observations from two flood events in the Daan River gorge in western Taiwan suggest that coarse sediment evacuation and re-deposition can cause intra-flood changes of up to several meters in channel bed elevation that are distinct from measured before/after bed changes. We hypothesize that this could be related to the abrupt change in width between the 1 km long bedrock gorge and the river upstream and downstream. An analysis of the theoretical relationships between discharge, channel width, and bedload transport capacity shows that for a given slope, narrow channels transport bedload more efficiently than wide ones at low discharges, while wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modeling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. Further, the deposition or erosion that takes place within a flood is often not reflected in the before/after changes to the bed, and this disconnect increases with increasing flood size.
How to cite: Cook, K., Turowski, J., and Hovius, N.: Width control on event scale bedload dynamics in bedrock-confined channels, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2141, https://doi.org/10.5194/egusphere-egu21-2141, 2021.
In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing, and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory, and numerical modeling to address this gap. Observations from two flood events in the Daan River gorge in western Taiwan suggest that coarse sediment evacuation and re-deposition can cause intra-flood changes of up to several meters in channel bed elevation that are distinct from measured before/after bed changes. We hypothesize that this could be related to the abrupt change in width between the 1 km long bedrock gorge and the river upstream and downstream. An analysis of the theoretical relationships between discharge, channel width, and bedload transport capacity shows that for a given slope, narrow channels transport bedload more efficiently than wide ones at low discharges, while wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modeling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. Further, the deposition or erosion that takes place within a flood is often not reflected in the before/after changes to the bed, and this disconnect increases with increasing flood size.
How to cite: Cook, K., Turowski, J., and Hovius, N.: Width control on event scale bedload dynamics in bedrock-confined channels, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2141, https://doi.org/10.5194/egusphere-egu21-2141, 2021.
EGU21-10377 | vPICO presentations | GM5.1
Analysis of geometric relationships of bedrock and alluvial channels: a comparison between rivers from the Scottish Highlands and San Gabriel Mountains (USA)Mel O. Guirro, Rebecca A. Hodge, Fiona Clubb, and Laura Turnbull
Sediment transport in rivers depends on interactions between sediment supply, topography, and flow characteristics. Erosion in bedrock rivers controls topography and is paramount in landscape evolution models. The riverbed cover indicates sediment transport processes: alluvial cover indicates low transport capacity or high sediment supply, and bedrock cover demonstrates high transport capacity or low sediment supply. This study aims to evaluate controls on the spatial distributions of bedrock and alluvial covers, by analysing scaling geometric relations between bedrock and alluvial channels. A Principal Component Analysis (PCA) was conducted to evaluate correlations between river slope, depth, width, and sediment size. The two principal components were used to implement a clustering analysis in order to identify differences in alluvial and bedrock sections. Spatial distributions of mixed bedrock-alluvial sections were investigated from two datasets - Scottish Highlands (Whitbread 2015) and the San Gabriel Mountains in the USA (Dibiase 2011)-, representing different environmental conditions, such as erosion rates, lithology, tectonics, and climate. The rock strength of both areas is high, and therefore it is excluded as a factor that explains the difference between the areas. The results of the cluster analysis were different in each environment. The main sources of variation among river sections identified by PCA were slope and width for the San Gabriel Mountains, and drainage area and depth for the Scottish Highlands. The rivers in the Scottish Highlands formed clusters that differentiate bedrock and alluvial patches, showing a clear geometric distinction between channels. However, the river analysis from the San Gabriel Mountains showed no clusters. Bedrock rivers are typically described as narrower and steeper than alluvial rivers, as demonstrated by rivers in the Scottish Highlands (e.g. slope was around 0.1 m/m for bedrock sections and 0.01 m/m for alluvial sections). However, this may not be always the case: both bedrock and alluvial sections in San Gabriel Mountains presented similar slope around 0.1 m/m. The inability to demonstrate significant geometry differences in bedrock and alluvial sections in the San Gabriel Mountains may be due to the frequency and magnitude of sediment supply of that region, which are influenced by tectonics and climate. A major difference in the supply of sediment in rivers of the San Gabriel Mountains is the frequent occurrence of debris flow. Non-linear interactions between hydraulic and sediment processes may constantly modify the geometry of bedrock-alluvial channels, increasing the complexity of analysis at larger temporal and spatial scales. This study is part of the i-CONN project, which links connectivity in different scientific disciplines. A sediment connectivity assessment in different environments and scales may be useful to evaluate the controls on the spatial distribution of bedrock and alluvial rivers.
Dibiase, R.A. 2011. Tectonic Geomorphology of the San Gabriel Mountains, CA. PhD Thesis. Arizona State University, Phoenix, 247pp.
Whitbread, K. 2015. Channel geometry data set for the northwest Scottish Highlands. British Geological Survey Open Report, OR/15/040. 12pp.
How to cite: Guirro, M. O., Hodge, R. A., Clubb, F., and Turnbull, L.: Analysis of geometric relationships of bedrock and alluvial channels: a comparison between rivers from the Scottish Highlands and San Gabriel Mountains (USA), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10377, https://doi.org/10.5194/egusphere-egu21-10377, 2021.
Sediment transport in rivers depends on interactions between sediment supply, topography, and flow characteristics. Erosion in bedrock rivers controls topography and is paramount in landscape evolution models. The riverbed cover indicates sediment transport processes: alluvial cover indicates low transport capacity or high sediment supply, and bedrock cover demonstrates high transport capacity or low sediment supply. This study aims to evaluate controls on the spatial distributions of bedrock and alluvial covers, by analysing scaling geometric relations between bedrock and alluvial channels. A Principal Component Analysis (PCA) was conducted to evaluate correlations between river slope, depth, width, and sediment size. The two principal components were used to implement a clustering analysis in order to identify differences in alluvial and bedrock sections. Spatial distributions of mixed bedrock-alluvial sections were investigated from two datasets - Scottish Highlands (Whitbread 2015) and the San Gabriel Mountains in the USA (Dibiase 2011)-, representing different environmental conditions, such as erosion rates, lithology, tectonics, and climate. The rock strength of both areas is high, and therefore it is excluded as a factor that explains the difference between the areas. The results of the cluster analysis were different in each environment. The main sources of variation among river sections identified by PCA were slope and width for the San Gabriel Mountains, and drainage area and depth for the Scottish Highlands. The rivers in the Scottish Highlands formed clusters that differentiate bedrock and alluvial patches, showing a clear geometric distinction between channels. However, the river analysis from the San Gabriel Mountains showed no clusters. Bedrock rivers are typically described as narrower and steeper than alluvial rivers, as demonstrated by rivers in the Scottish Highlands (e.g. slope was around 0.1 m/m for bedrock sections and 0.01 m/m for alluvial sections). However, this may not be always the case: both bedrock and alluvial sections in San Gabriel Mountains presented similar slope around 0.1 m/m. The inability to demonstrate significant geometry differences in bedrock and alluvial sections in the San Gabriel Mountains may be due to the frequency and magnitude of sediment supply of that region, which are influenced by tectonics and climate. A major difference in the supply of sediment in rivers of the San Gabriel Mountains is the frequent occurrence of debris flow. Non-linear interactions between hydraulic and sediment processes may constantly modify the geometry of bedrock-alluvial channels, increasing the complexity of analysis at larger temporal and spatial scales. This study is part of the i-CONN project, which links connectivity in different scientific disciplines. A sediment connectivity assessment in different environments and scales may be useful to evaluate the controls on the spatial distribution of bedrock and alluvial rivers.
Dibiase, R.A. 2011. Tectonic Geomorphology of the San Gabriel Mountains, CA. PhD Thesis. Arizona State University, Phoenix, 247pp.
Whitbread, K. 2015. Channel geometry data set for the northwest Scottish Highlands. British Geological Survey Open Report, OR/15/040. 12pp.
How to cite: Guirro, M. O., Hodge, R. A., Clubb, F., and Turnbull, L.: Analysis of geometric relationships of bedrock and alluvial channels: a comparison between rivers from the Scottish Highlands and San Gabriel Mountains (USA), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10377, https://doi.org/10.5194/egusphere-egu21-10377, 2021.
EGU21-12453 | vPICO presentations | GM5.1
Feedbacks between sediment input, bed state and threshold for motion in gravel-bed rivers: an experimental studyMatteo Saletti and Marwan Hassan
In gravel-bed rivers the relation between the magnitude and frequency of sediment input, the threshold for motion and channel stability is still not fully understood.
Here we present results from a 280-hour long flume experiment, in which poorly sorted sediment was fed episodically in an 18-m long, 2.2%-steep channel. The experiment included 7 consecutive runs lasting 40 hours each characterized by a constant water discharge but different sediment supply regimes (i.e., with no feed, constant feed and sediment pulses). Several measurements of sediment transport, flow depth and bed structures were taken along the flume, to assess how changes in sediment supply influence particle mobility and channel stability.
Our results show that the surface grain‐size distribution coarsened quickly, developing an armored layer that persisted throughout the entire experiment with only short-lived changes after sediment pulses. Grain clusters and other bed structures developed continuously during the experiments, changing dynamically in response to sediment pulses.
We estimated the thresholds of motion with three different methods, all of which yielded consistent results. Overall, the threshold for motion increased during the experiment, fluctuating in response to changes in sediment input. Our results provide further evidence to the idea that the threshold for motion in gravel-bed rivers is not a constant, but changes as a state parameter. These changes in our experiments are controlled by (a) the sediment supply regime, (b) the degree of bed structuring, and (c) the history of bed evolution. These outcomes suggest that sediment supply regime is a primary control on bed surface evolution and the channel stabilizing function played by surface structures.
How to cite: Saletti, M. and Hassan, M.: Feedbacks between sediment input, bed state and threshold for motion in gravel-bed rivers: an experimental study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12453, https://doi.org/10.5194/egusphere-egu21-12453, 2021.
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In gravel-bed rivers the relation between the magnitude and frequency of sediment input, the threshold for motion and channel stability is still not fully understood.
Here we present results from a 280-hour long flume experiment, in which poorly sorted sediment was fed episodically in an 18-m long, 2.2%-steep channel. The experiment included 7 consecutive runs lasting 40 hours each characterized by a constant water discharge but different sediment supply regimes (i.e., with no feed, constant feed and sediment pulses). Several measurements of sediment transport, flow depth and bed structures were taken along the flume, to assess how changes in sediment supply influence particle mobility and channel stability.
Our results show that the surface grain‐size distribution coarsened quickly, developing an armored layer that persisted throughout the entire experiment with only short-lived changes after sediment pulses. Grain clusters and other bed structures developed continuously during the experiments, changing dynamically in response to sediment pulses.
We estimated the thresholds of motion with three different methods, all of which yielded consistent results. Overall, the threshold for motion increased during the experiment, fluctuating in response to changes in sediment input. Our results provide further evidence to the idea that the threshold for motion in gravel-bed rivers is not a constant, but changes as a state parameter. These changes in our experiments are controlled by (a) the sediment supply regime, (b) the degree of bed structuring, and (c) the history of bed evolution. These outcomes suggest that sediment supply regime is a primary control on bed surface evolution and the channel stabilizing function played by surface structures.
How to cite: Saletti, M. and Hassan, M.: Feedbacks between sediment input, bed state and threshold for motion in gravel-bed rivers: an experimental study, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12453, https://doi.org/10.5194/egusphere-egu21-12453, 2021.
EGU21-9362 | vPICO presentations | GM5.1
An entropy-based investigation on the river recovery potential in a regulated river basinChandan Pradhan, Suman Padhee, Subashisa Dutta, and Rishikesh Bharti
River recovery is the process that describes the capacity of the river to adjust to the limiting boundary conditions. In the regulated rivers, altered flow-sediment regime controls the trajectory of adjustments along the geomorphic and vegetative attributes. The present study is focused on recovery potential assessment of Mahanadi River, which shows a gradual emergence of in-channel vegetation in the post-dam period. The study area encompasses (i) 10 km reach of Mahanadi River (M1) having bedrock exposed, anabranching channel pattern and (ii) 102 km reach of Ong river (O1) with alluvial, compound channel form. In this study, Google Earth Engine cloud computing platform is used to process the Landsat images (1980-2010) and vegetation, water, and floodplain geomorphic classes are derived by Normalized Difference Vegetation Index (NDVI) and modified Normalized Difference Water Index (mNDWI). Finally, the intensity disorder index (IDI) is computed to represent the ‘system state’ in the post-monsoon periods and the influence of vegetation growth on the channel recovery. The results show that M1 is relatively stable, with cumulative vegetation area increased from 2% in 1980 to 8% in 2010. However, O1 demonstrates an accelerated increase in vegetation area i.e., 10% in 1980 to 30% in 2010. The system state (IDI) varies between 0.2 and 0.6 and follows a decreasing trend along M1 and O1. The findings establish that both regulated reaches may approach channel recovery in the near future, and prevailing boundary conditions indirectly influence the rate and direction of IDI.
How to cite: Pradhan, C., Padhee, S., Dutta, S., and Bharti, R.: An entropy-based investigation on the river recovery potential in a regulated river basin , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9362, https://doi.org/10.5194/egusphere-egu21-9362, 2021.
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River recovery is the process that describes the capacity of the river to adjust to the limiting boundary conditions. In the regulated rivers, altered flow-sediment regime controls the trajectory of adjustments along the geomorphic and vegetative attributes. The present study is focused on recovery potential assessment of Mahanadi River, which shows a gradual emergence of in-channel vegetation in the post-dam period. The study area encompasses (i) 10 km reach of Mahanadi River (M1) having bedrock exposed, anabranching channel pattern and (ii) 102 km reach of Ong river (O1) with alluvial, compound channel form. In this study, Google Earth Engine cloud computing platform is used to process the Landsat images (1980-2010) and vegetation, water, and floodplain geomorphic classes are derived by Normalized Difference Vegetation Index (NDVI) and modified Normalized Difference Water Index (mNDWI). Finally, the intensity disorder index (IDI) is computed to represent the ‘system state’ in the post-monsoon periods and the influence of vegetation growth on the channel recovery. The results show that M1 is relatively stable, with cumulative vegetation area increased from 2% in 1980 to 8% in 2010. However, O1 demonstrates an accelerated increase in vegetation area i.e., 10% in 1980 to 30% in 2010. The system state (IDI) varies between 0.2 and 0.6 and follows a decreasing trend along M1 and O1. The findings establish that both regulated reaches may approach channel recovery in the near future, and prevailing boundary conditions indirectly influence the rate and direction of IDI.
How to cite: Pradhan, C., Padhee, S., Dutta, S., and Bharti, R.: An entropy-based investigation on the river recovery potential in a regulated river basin , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9362, https://doi.org/10.5194/egusphere-egu21-9362, 2021.
EGU21-14124 | vPICO presentations | GM5.1
Automatic Extraction of Intermittent Channel Systems of a Low‐Relief, Low‐Gradient FloodplainHaiqing Xu, Shailesh van der Steeg, and Raymond Torres
Intermittent floodplain channels are low‐relief conduits etched into the floodplain surface and remain dry much of the year. These channels comprise expansive systems and are important because during low‐level inundation they facilitate lateral hydraulic connectivity throughout the floodplain. Nevertheless, few studies have focused on these floodplain channels due to uncertainty in how to identify and characterize these systems in digital elevation models (DEMs). In particular, their automatic extraction from widely available DEMs is challenging due to the characteristically low‐relief and low‐gradient topography of floodplains. We applied three channel extraction approaches to the Congaree River floodplain DEM and compared the results to a channel reference map created through numerous field excursions over the past 30 years. The methods that we tested are based on flow accumulation area, topographic curvature, and mathematical morphology, or the D8, Laplacian, and bottom‐hat transform (BHT), respectively. Of the 198 km of reference channels the BHT, Laplacian, and D8 extracted 83%, 71%, and 23%, respectively, and the BHT consistently had the highest agreement with the reference network at the local (5 m) and regional (10 km) scales. The extraction results also include commission “error”, augmenting the reference map with about 100 km of channel length. Overall, the BHT method provided the best results for channel extraction, giving over 298 km in 69 km2 with a detrended regional relief of 1.9 m.
How to cite: Xu, H., van der Steeg, S., and Torres, R.: Automatic Extraction of Intermittent Channel Systems of a Low‐Relief, Low‐Gradient Floodplain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14124, https://doi.org/10.5194/egusphere-egu21-14124, 2021.
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Intermittent floodplain channels are low‐relief conduits etched into the floodplain surface and remain dry much of the year. These channels comprise expansive systems and are important because during low‐level inundation they facilitate lateral hydraulic connectivity throughout the floodplain. Nevertheless, few studies have focused on these floodplain channels due to uncertainty in how to identify and characterize these systems in digital elevation models (DEMs). In particular, their automatic extraction from widely available DEMs is challenging due to the characteristically low‐relief and low‐gradient topography of floodplains. We applied three channel extraction approaches to the Congaree River floodplain DEM and compared the results to a channel reference map created through numerous field excursions over the past 30 years. The methods that we tested are based on flow accumulation area, topographic curvature, and mathematical morphology, or the D8, Laplacian, and bottom‐hat transform (BHT), respectively. Of the 198 km of reference channels the BHT, Laplacian, and D8 extracted 83%, 71%, and 23%, respectively, and the BHT consistently had the highest agreement with the reference network at the local (5 m) and regional (10 km) scales. The extraction results also include commission “error”, augmenting the reference map with about 100 km of channel length. Overall, the BHT method provided the best results for channel extraction, giving over 298 km in 69 km2 with a detrended regional relief of 1.9 m.
How to cite: Xu, H., van der Steeg, S., and Torres, R.: Automatic Extraction of Intermittent Channel Systems of a Low‐Relief, Low‐Gradient Floodplain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14124, https://doi.org/10.5194/egusphere-egu21-14124, 2021.
EGU21-7216 | vPICO presentations | GM5.1
Spatial planning and flood risk: The case of the Buna River, Shkoder, AlbaniaErvis Krymbi and Dritan Rustja
In the last years, Albania underwent a rapid development, which resulted in an uncontrolled building boom and general land degradation. For these reasons, an ever-greater portion of the Albanian population is exposed to natural risks, whose major threats are represented by floods and earthquakes. Spatial planning and hydraulic risk management are a worldwide necessity which is best achieved when natural and artificial elements located closely to watercourses are known in detail. A geodatabase is a practical tool to store and manage such information. Land use and land cover changes have negative consequences on watershed management in Buna River Basin. They increase impervious ground surfaces, decrease infiltration rate and increase runoff rate, hence causing flood during the dry seasons. This study was undertaken to achieve the natural and artificial elements connected to hydraulic risk and fluvial dynamics in Buna River. Through a GIS overlay and GPS measurements where mapped elements include buildings, hydraulic works, weirs, drainage outlets, riverbanks, structural damages, fluvial bars and eroding banks. Consequently, a GIS geo database was built to visualize the spatial distribution of the mapped elements and to store a series of technical data, including the present preservation condition for man-made objects. GPS data was integrated in GIS to examine the extent of land use and cover change in the sub catchment of Buna River. Both quantitative and qualitative data were used for this study. The geo database provides an overview of the territories connected with the fluvial dynamics, highlighting that in the studied territory; the more is urbanized, the more it is exposed to hydraulic risk.
Key word; spatial planning, natural hazards, relief drill, Buna river, Shkoder.
How to cite: Krymbi, E. and Rustja, D.: Spatial planning and flood risk: The case of the Buna River, Shkoder, Albania, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7216, https://doi.org/10.5194/egusphere-egu21-7216, 2021.
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In the last years, Albania underwent a rapid development, which resulted in an uncontrolled building boom and general land degradation. For these reasons, an ever-greater portion of the Albanian population is exposed to natural risks, whose major threats are represented by floods and earthquakes. Spatial planning and hydraulic risk management are a worldwide necessity which is best achieved when natural and artificial elements located closely to watercourses are known in detail. A geodatabase is a practical tool to store and manage such information. Land use and land cover changes have negative consequences on watershed management in Buna River Basin. They increase impervious ground surfaces, decrease infiltration rate and increase runoff rate, hence causing flood during the dry seasons. This study was undertaken to achieve the natural and artificial elements connected to hydraulic risk and fluvial dynamics in Buna River. Through a GIS overlay and GPS measurements where mapped elements include buildings, hydraulic works, weirs, drainage outlets, riverbanks, structural damages, fluvial bars and eroding banks. Consequently, a GIS geo database was built to visualize the spatial distribution of the mapped elements and to store a series of technical data, including the present preservation condition for man-made objects. GPS data was integrated in GIS to examine the extent of land use and cover change in the sub catchment of Buna River. Both quantitative and qualitative data were used for this study. The geo database provides an overview of the territories connected with the fluvial dynamics, highlighting that in the studied territory; the more is urbanized, the more it is exposed to hydraulic risk.
Key word; spatial planning, natural hazards, relief drill, Buna river, Shkoder.
How to cite: Krymbi, E. and Rustja, D.: Spatial planning and flood risk: The case of the Buna River, Shkoder, Albania, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7216, https://doi.org/10.5194/egusphere-egu21-7216, 2021.
EGU21-15498 | vPICO presentations | GM5.1
Contextualized sedimentation rates for large floods along the lower Mississippi River: the importance of flood durationPaul Hudson, Franklin Heitmuller, Samuel Muñoz, and Jansen Costello
Flood sedimentary deposits vary due to upper basin and lower basin controls. In this study we focus on overbank sediment thickness, which over longer periods drives changes to riparian aquatic habitat and floodplain construction. The study setting is a ~25 km long segment of the lower Mississippi alluvial valley, between Natchez, MS and Red River Landing, LA. We report new field data for overbank sedimentation generated by compound flooding over 2018 and 2019 hydrologic years, and compare with sedimentation data from prior large flood events. Overbank conditions in 2018 and 2019 persisted for 286 days (at Natchez, MS). During the 2019 hydrologic year the Mississippi was overbank for a record duration of 216 days, resulting in a much greater duration of overbank sedimentation than the 2011 (53 days) and 1973 (90 days) flood events.
The thickness of overbank deposits are reported for 48 field sites across a range of depositional environments typical of large lowland meandering river floodplains. Flood deposits were sampled in October 2019 using conventional field sampling procedures, including sedimentation traps (artificial grass mats installed in October 2017) and recognition of recent sediment deposited atop buried organic layers. The thickness of each reported sample is an average of three measurements obtained at each field site.
The average thickness of flood deposit samples over 2018-2019 hydrologic years is 71 mm, with variability according to distance from channel and floodplain depositional environment. Maximum sedimentation was associated with crevasse (750 mm) and sand sheet (1,430 mm) deposition along the crest of natural levees. Sedimentation thickness decreases within ~250 m of the channel, but remains high at a distance of ~3.5 km (30 mm). Beyond the range of sand sheet deposition, overbank deposition is likely influenced by variability in floodplain hydrology and geomorphology across natural levee (181 mm), meander scroll (30 mm), old channel (77 mm), and backswamp (108 mm) environments. High backswamp sedimentation at the study site is likely influenced by historic hydraulic engineering for flood control, which has altered local sedimentation patterns.
The 2018-2019 sedimentation data are contextualized by comparison with field data from the record 2011 magnitude flood (peak Q of 65,978 m3/s at Vicksburg, MS, USGS 0728900) and the historic 1973 flood (55,558 m3/s). Average sediment thickness for the 2011 and 1973 overbank deposits was 42 mm (n=49) and 230 mm (n=31), respectively. The 2018-2019 daily sedimentation rate (0.25 mm/day) is much less than 2011 (0.75 mm/day). Thus, the much thicker sedimentary deposits for the 2018-2019 events suggests the greater importance of flood duration – rather than flood magnitude – to overall floodplain processes and alluvial fill chronologies along lowland rivers. The much lower flood sedimentation rate for 2018-2019 in comparison with 1973 (2.49 mm/day) may reveal the persistent decline in Mississippi suspended sediment loads since the early 1950s. Study results are further contextualized by considering corresponding event-based discharge – suspended sediment dynamics, sediment province, as well as flood hydroclimatology.
How to cite: Hudson, P., Heitmuller, F., Muñoz, S., and Costello, J.: Contextualized sedimentation rates for large floods along the lower Mississippi River: the importance of flood duration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15498, https://doi.org/10.5194/egusphere-egu21-15498, 2021.
Flood sedimentary deposits vary due to upper basin and lower basin controls. In this study we focus on overbank sediment thickness, which over longer periods drives changes to riparian aquatic habitat and floodplain construction. The study setting is a ~25 km long segment of the lower Mississippi alluvial valley, between Natchez, MS and Red River Landing, LA. We report new field data for overbank sedimentation generated by compound flooding over 2018 and 2019 hydrologic years, and compare with sedimentation data from prior large flood events. Overbank conditions in 2018 and 2019 persisted for 286 days (at Natchez, MS). During the 2019 hydrologic year the Mississippi was overbank for a record duration of 216 days, resulting in a much greater duration of overbank sedimentation than the 2011 (53 days) and 1973 (90 days) flood events.
The thickness of overbank deposits are reported for 48 field sites across a range of depositional environments typical of large lowland meandering river floodplains. Flood deposits were sampled in October 2019 using conventional field sampling procedures, including sedimentation traps (artificial grass mats installed in October 2017) and recognition of recent sediment deposited atop buried organic layers. The thickness of each reported sample is an average of three measurements obtained at each field site.
The average thickness of flood deposit samples over 2018-2019 hydrologic years is 71 mm, with variability according to distance from channel and floodplain depositional environment. Maximum sedimentation was associated with crevasse (750 mm) and sand sheet (1,430 mm) deposition along the crest of natural levees. Sedimentation thickness decreases within ~250 m of the channel, but remains high at a distance of ~3.5 km (30 mm). Beyond the range of sand sheet deposition, overbank deposition is likely influenced by variability in floodplain hydrology and geomorphology across natural levee (181 mm), meander scroll (30 mm), old channel (77 mm), and backswamp (108 mm) environments. High backswamp sedimentation at the study site is likely influenced by historic hydraulic engineering for flood control, which has altered local sedimentation patterns.
The 2018-2019 sedimentation data are contextualized by comparison with field data from the record 2011 magnitude flood (peak Q of 65,978 m3/s at Vicksburg, MS, USGS 0728900) and the historic 1973 flood (55,558 m3/s). Average sediment thickness for the 2011 and 1973 overbank deposits was 42 mm (n=49) and 230 mm (n=31), respectively. The 2018-2019 daily sedimentation rate (0.25 mm/day) is much less than 2011 (0.75 mm/day). Thus, the much thicker sedimentary deposits for the 2018-2019 events suggests the greater importance of flood duration – rather than flood magnitude – to overall floodplain processes and alluvial fill chronologies along lowland rivers. The much lower flood sedimentation rate for 2018-2019 in comparison with 1973 (2.49 mm/day) may reveal the persistent decline in Mississippi suspended sediment loads since the early 1950s. Study results are further contextualized by considering corresponding event-based discharge – suspended sediment dynamics, sediment province, as well as flood hydroclimatology.
How to cite: Hudson, P., Heitmuller, F., Muñoz, S., and Costello, J.: Contextualized sedimentation rates for large floods along the lower Mississippi River: the importance of flood duration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15498, https://doi.org/10.5194/egusphere-egu21-15498, 2021.
EGU21-9075 | vPICO presentations | GM5.1
Wetland dynamics at the transition between humid and semiarid environments of inland Brazil: São Francisco river morphodynamics and implications for the Pandeiros wetland.Diego Alves de Oliveira, Cristina Helena Ribeiro Rocha Augustin, Trevor Hoey, and Cristina Persano
The presence of wetlands as a result of local fluvial and hydrological conditions constitutes a frequently observed feature of such rivers. Therefore, they are important elements of the basin, because besides functioning as buffer zones for CO2 and sediments they also house important ecosystems, playing an important role in the control of water circulation. Brazilian wetlands have different typologies and sizes, varying from huge swamplands such as the Pantanal do Mato Grosso, to flooded savannas called “veredas” or oxbow lakes. Their distribution in inland areas depends on the variety of flood pulses mainly linked to seasonality with the presence of distinct dry and wet seasons (Junk et al., 1989). This strong seasonality affects the São Francisco River (SFR), the 4th largest river in Brazil, which has frequent marginal lakes and swamps as it passes through five Brazilian states. This research aims to analyze the effect of the variation of the SFR level from 1925 to 2018, on the flow of the Pandeiros River which is one of many tributaries on the left side of SFR and on its wetland (“Pantanal Mineiro”). This wetland is hydrogeomorphologically linked to the SFR and receives water inputs during SFR flood periods. Measurements of the SFR water level performed once daily in the morning were obtained from gauging station no 44200000 belonging to the Companhia de Pesquisa de Recursos Minerais (CPRM) [altitude 445 m; 15°56'57.84"S; 44°52'4.68"W. The hydrological year starts at the end of the dry season on October 1st. Time series analyses (level duration curve, Seasonal Trend Decomposition (STL) of the daily level data, monthly level, mean, maximum, minimum level for each day of the year) were conducted to describe the hydrological regime and to assess temporal changes of the SFR levels and how these affect the magnitude, frequency and duration of flooding of the Pandeiros’s River wetland. Field observations (March 14, 2018) show that when SFR, which is Pandeiro’s base level, reaches a level of 5.0 m this leads to flooding conditions of the Pandeiros River wetland. Over the full period of record (1925-2018) the average level of the SFR was 3.86 m, with a minimum annual average of 2.43 m during the dry season (winter) and maximum of 5.98 m during the wet season (summer), with an average annual range of 3.55 m between both seasons. The SFR was above the 5.0 m threshold flooding level for 20% of the time 1925-2018, which corresponds to an average of 77.8 days of flooding per year in the wetland. The longest period of inundation was 178 days in 1926, when the SFR reached its maximum recorded level, and the shortest was 1 day in 2015, when it reached its minimum. The number of days per year of inundation have decreased over the full record, but that this is mainly due to a significant decrease since 1985. Prior to this, cyclic differences between wetter (1925 and 1985) and drier periods (1925 to 1945, 1945 to 1965) are observed.
How to cite: Alves de Oliveira, D., Helena Ribeiro Rocha Augustin, C., Hoey, T., and Persano, C.: Wetland dynamics at the transition between humid and semiarid environments of inland Brazil: São Francisco river morphodynamics and implications for the Pandeiros wetland., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9075, https://doi.org/10.5194/egusphere-egu21-9075, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The presence of wetlands as a result of local fluvial and hydrological conditions constitutes a frequently observed feature of such rivers. Therefore, they are important elements of the basin, because besides functioning as buffer zones for CO2 and sediments they also house important ecosystems, playing an important role in the control of water circulation. Brazilian wetlands have different typologies and sizes, varying from huge swamplands such as the Pantanal do Mato Grosso, to flooded savannas called “veredas” or oxbow lakes. Their distribution in inland areas depends on the variety of flood pulses mainly linked to seasonality with the presence of distinct dry and wet seasons (Junk et al., 1989). This strong seasonality affects the São Francisco River (SFR), the 4th largest river in Brazil, which has frequent marginal lakes and swamps as it passes through five Brazilian states. This research aims to analyze the effect of the variation of the SFR level from 1925 to 2018, on the flow of the Pandeiros River which is one of many tributaries on the left side of SFR and on its wetland (“Pantanal Mineiro”). This wetland is hydrogeomorphologically linked to the SFR and receives water inputs during SFR flood periods. Measurements of the SFR water level performed once daily in the morning were obtained from gauging station no 44200000 belonging to the Companhia de Pesquisa de Recursos Minerais (CPRM) [altitude 445 m; 15°56'57.84"S; 44°52'4.68"W. The hydrological year starts at the end of the dry season on October 1st. Time series analyses (level duration curve, Seasonal Trend Decomposition (STL) of the daily level data, monthly level, mean, maximum, minimum level for each day of the year) were conducted to describe the hydrological regime and to assess temporal changes of the SFR levels and how these affect the magnitude, frequency and duration of flooding of the Pandeiros’s River wetland. Field observations (March 14, 2018) show that when SFR, which is Pandeiro’s base level, reaches a level of 5.0 m this leads to flooding conditions of the Pandeiros River wetland. Over the full period of record (1925-2018) the average level of the SFR was 3.86 m, with a minimum annual average of 2.43 m during the dry season (winter) and maximum of 5.98 m during the wet season (summer), with an average annual range of 3.55 m between both seasons. The SFR was above the 5.0 m threshold flooding level for 20% of the time 1925-2018, which corresponds to an average of 77.8 days of flooding per year in the wetland. The longest period of inundation was 178 days in 1926, when the SFR reached its maximum recorded level, and the shortest was 1 day in 2015, when it reached its minimum. The number of days per year of inundation have decreased over the full record, but that this is mainly due to a significant decrease since 1985. Prior to this, cyclic differences between wetter (1925 and 1985) and drier periods (1925 to 1945, 1945 to 1965) are observed.
How to cite: Alves de Oliveira, D., Helena Ribeiro Rocha Augustin, C., Hoey, T., and Persano, C.: Wetland dynamics at the transition between humid and semiarid environments of inland Brazil: São Francisco river morphodynamics and implications for the Pandeiros wetland., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9075, https://doi.org/10.5194/egusphere-egu21-9075, 2021.
EGU21-6652 | vPICO presentations | GM5.1
Quaternary climate variability as the main driver of the fluvial evolution of the Middle Tocantins River, eastern AmazoniaJandessa Jesus, Fabiano Pupim, and André Sawakuchi
The Tocantins River is the easternmost fluvial system of the Amazon region, with a watershed draining both the Amazon rainforest and the Cerrado dry forest. This condition makes the Tocantins a natural laboratory to investigate the effects of past climate variability along with the rainforest-savanna ecosystems because its watershed drains both the Amazon rainforest and the Cerrado dry forest, and it is influenced by the Equatorial and central-northeast Brazil hydroclimates. Despite these unique physiographic and climatologic conditions, the Quaternary history of the Tocantins River is poorly known due to a lack of geochronological data about its sedimentary record. Here, we use optically stimulated luminescence (OSL) dating applied to quartz sand grains combined with geomorphological and sedimentological techniques to reconstruct the morphosedimentary evolution of the middle reach of the Tocantins River during the Late Quaternary. Three main geomorphological units were mapped: (i) fluvial plain, (ii) fluvial terraces, and (iii) paleo-alluvial fans. The OSL ages of 33 sediment samples retrieved from these geomorphological units range from 661 ± 42 years to 160 ± 16.3 ka, allowing to reconstruct of the depositional-erosion periods during the Mid-Late Pleistocene and Holocene. Our data indicate three stages of fluvial aggradation and two stages of incision. The older aggradational stage is represented by sediments from Upper Terrace (T1) and the paleo-alluvial fan deposited between 160 and 32 ka. Subsequently, a major incision event occurred at ~31 ka, which resulted in the abandonment of T1. The second phase of aggradation is recorded in the Lower Terrace (T2) and it also promotes reactivation of the paleo-alluvial fans from 31 to 6 ka. A new incision occurred from about 6 to 5 ka, allowing the abandonment of the T2 and reducing the local base level to its current position. The modern floodplain was built from 5 ka to the present, with sediment deposition due to lateral migration of the Tocantins River channel. The phases of aggradation and incision were correlated with regional paleoclimatic data, suggesting that precipitation changes related to the South American Summer Monsoon (SASM) as the main driver of the evolution of the Tocantins river in the last 160 ka. Disturbances in the supply of sediments and the flow of these rivers promote phases of depositional (drier periods) and incision (wetter periods). These depositional and incision phases of the Tocantins River appear to be synchronous with changes recorded by rivers from central and western Amazon, suggesting that the SASM is the main control of the Amazon fluvial systems. The continuous change in the Tocantins River dynamics has molded a high heterogeneity of habitats in the associated floodplains and terraces, which is a fundamental factor to support the diversity of fauna and flora in this transitional environment between Amazon and Cerrado biomes.
How to cite: Jesus, J., Pupim, F., and Sawakuchi, A.: Quaternary climate variability as the main driver of the fluvial evolution of the Middle Tocantins River, eastern Amazonia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6652, https://doi.org/10.5194/egusphere-egu21-6652, 2021.
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The Tocantins River is the easternmost fluvial system of the Amazon region, with a watershed draining both the Amazon rainforest and the Cerrado dry forest. This condition makes the Tocantins a natural laboratory to investigate the effects of past climate variability along with the rainforest-savanna ecosystems because its watershed drains both the Amazon rainforest and the Cerrado dry forest, and it is influenced by the Equatorial and central-northeast Brazil hydroclimates. Despite these unique physiographic and climatologic conditions, the Quaternary history of the Tocantins River is poorly known due to a lack of geochronological data about its sedimentary record. Here, we use optically stimulated luminescence (OSL) dating applied to quartz sand grains combined with geomorphological and sedimentological techniques to reconstruct the morphosedimentary evolution of the middle reach of the Tocantins River during the Late Quaternary. Three main geomorphological units were mapped: (i) fluvial plain, (ii) fluvial terraces, and (iii) paleo-alluvial fans. The OSL ages of 33 sediment samples retrieved from these geomorphological units range from 661 ± 42 years to 160 ± 16.3 ka, allowing to reconstruct of the depositional-erosion periods during the Mid-Late Pleistocene and Holocene. Our data indicate three stages of fluvial aggradation and two stages of incision. The older aggradational stage is represented by sediments from Upper Terrace (T1) and the paleo-alluvial fan deposited between 160 and 32 ka. Subsequently, a major incision event occurred at ~31 ka, which resulted in the abandonment of T1. The second phase of aggradation is recorded in the Lower Terrace (T2) and it also promotes reactivation of the paleo-alluvial fans from 31 to 6 ka. A new incision occurred from about 6 to 5 ka, allowing the abandonment of the T2 and reducing the local base level to its current position. The modern floodplain was built from 5 ka to the present, with sediment deposition due to lateral migration of the Tocantins River channel. The phases of aggradation and incision were correlated with regional paleoclimatic data, suggesting that precipitation changes related to the South American Summer Monsoon (SASM) as the main driver of the evolution of the Tocantins river in the last 160 ka. Disturbances in the supply of sediments and the flow of these rivers promote phases of depositional (drier periods) and incision (wetter periods). These depositional and incision phases of the Tocantins River appear to be synchronous with changes recorded by rivers from central and western Amazon, suggesting that the SASM is the main control of the Amazon fluvial systems. The continuous change in the Tocantins River dynamics has molded a high heterogeneity of habitats in the associated floodplains and terraces, which is a fundamental factor to support the diversity of fauna and flora in this transitional environment between Amazon and Cerrado biomes.
How to cite: Jesus, J., Pupim, F., and Sawakuchi, A.: Quaternary climate variability as the main driver of the fluvial evolution of the Middle Tocantins River, eastern Amazonia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6652, https://doi.org/10.5194/egusphere-egu21-6652, 2021.
EGU21-9928 | vPICO presentations | GM5.1
Change of channel pattern and construction of fluvial terraces driven by SAMS since the LGM in southeastern South America: records from Tietê River, BrazilCaio Breda and Fabiano Nascimento Pupim
The last 30 ka is a period marked by well-documented abrupt environmental changes on Earth. Despite the growing efforts to investigate the effects of past environmental changes in the fluvial dynamics, there is a lack of studies in intraplate tropical regions. Here, we applied geomorphological, sedimentological, and optically stimulated luminescence dating (OSL) technics to investigate the effects of environmental factors on the evolution of the Upper and Middle Tietê River during the Late Quaternary. Tietê River is one of the most important rivers of the southeast of Brazil, flowing from steepest to low-relief intraplate terrains, and under tropical climate. In order to understand the responses of the Tietê River system to environmental changes during the Late Quaternary, two main questions were tentatively answered: (i) what are the most important allogeneic factors for the evolution of this system?; (ii) how did climatic fluctuations affect river dynamics over time? We recognized a sequence of seven terraces, from 2 to 105 m above the channel, in the Middle Tietê valley. These terraces are formed by thin deposits (< 10 m), composed of sandy and conglomeratic sediments. The high and intermediate terrace levels of the Middle Tietê River are strath, while the low terraces of the middle reach are cut-and-fill. The formation of seven terrace levels in the Middle Tietê River was controlled by the combination of low erosion resistance of the lithological substrate and high stream power and coarse bedload that increase the erosion efficiency of the channels. OSL dating of sedimentary deposits in different terrace levels indicate 5 periods of aggradation in the Middle Tietê valley since the Last Glacial Maximum: 18.5 ± 2.0 ka; 9.8 ± 1.0 to 8.6 ± 0.8 ka; 7.1 ± 0.7 to 5.8 ± 0.5 ka; 4.2 ± 0.4 to 3.1 ± 0.3 ka; and 0.6 ± 0.06 ka. The results indicate that the activity of the South American Monsoon System induced the occurrence of climatic fluctuations and changes in vegetation cover in the river valleys of southeastern Brazil over the past 20 ka. The aggradation periods are correlated with more arid environmental conditions and sparser vegetation, while the incision events in the valley developed under transitions to humid environmental conditions and stimulated by vegetation recovery.
Key-words: Tietê River, fluvial evolution, fluvial terraces, Quaternary geochronology.
How to cite: Breda, C. and Nascimento Pupim, F.: Change of channel pattern and construction of fluvial terraces driven by SAMS since the LGM in southeastern South America: records from Tietê River, Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9928, https://doi.org/10.5194/egusphere-egu21-9928, 2021.
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The last 30 ka is a period marked by well-documented abrupt environmental changes on Earth. Despite the growing efforts to investigate the effects of past environmental changes in the fluvial dynamics, there is a lack of studies in intraplate tropical regions. Here, we applied geomorphological, sedimentological, and optically stimulated luminescence dating (OSL) technics to investigate the effects of environmental factors on the evolution of the Upper and Middle Tietê River during the Late Quaternary. Tietê River is one of the most important rivers of the southeast of Brazil, flowing from steepest to low-relief intraplate terrains, and under tropical climate. In order to understand the responses of the Tietê River system to environmental changes during the Late Quaternary, two main questions were tentatively answered: (i) what are the most important allogeneic factors for the evolution of this system?; (ii) how did climatic fluctuations affect river dynamics over time? We recognized a sequence of seven terraces, from 2 to 105 m above the channel, in the Middle Tietê valley. These terraces are formed by thin deposits (< 10 m), composed of sandy and conglomeratic sediments. The high and intermediate terrace levels of the Middle Tietê River are strath, while the low terraces of the middle reach are cut-and-fill. The formation of seven terrace levels in the Middle Tietê River was controlled by the combination of low erosion resistance of the lithological substrate and high stream power and coarse bedload that increase the erosion efficiency of the channels. OSL dating of sedimentary deposits in different terrace levels indicate 5 periods of aggradation in the Middle Tietê valley since the Last Glacial Maximum: 18.5 ± 2.0 ka; 9.8 ± 1.0 to 8.6 ± 0.8 ka; 7.1 ± 0.7 to 5.8 ± 0.5 ka; 4.2 ± 0.4 to 3.1 ± 0.3 ka; and 0.6 ± 0.06 ka. The results indicate that the activity of the South American Monsoon System induced the occurrence of climatic fluctuations and changes in vegetation cover in the river valleys of southeastern Brazil over the past 20 ka. The aggradation periods are correlated with more arid environmental conditions and sparser vegetation, while the incision events in the valley developed under transitions to humid environmental conditions and stimulated by vegetation recovery.
Key-words: Tietê River, fluvial evolution, fluvial terraces, Quaternary geochronology.
How to cite: Breda, C. and Nascimento Pupim, F.: Change of channel pattern and construction of fluvial terraces driven by SAMS since the LGM in southeastern South America: records from Tietê River, Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9928, https://doi.org/10.5194/egusphere-egu21-9928, 2021.
EGU21-11713 | vPICO presentations | GM5.1
Late Quaternary evolution of the Upper Paraná River, southeast Brazil: a new geomorphological and chronological databaseStefania C. Oliveira, Fabiano N. Pupim, José C. Stevaux, and Mario L. Assine
The Paraná River has being extensively studied in terms of its hydrological and sedimentological aspects, but the geological history of its fluvial plain is still poorly understood due to the lack of geochronological data. Most of the published studies are focused on the low and middle reaches, and the region upstream of the Porto Primavera dam is an area almost unknown in terms of geomorphic evolution. Here, we aim to investigate the succession of geological events responsible for the evolution and current configuration of the Upper Paraná River fluvial system, in the stretch between the Jupiá and Porto Primavera Hydroelectric Plants (São Paulo and Mato Grosso states). Thus, we used an integrated approach including remote sensing data, geomorphology, sedimentology, bathymetric profiles, and chronological methods. Four geomorphological compartments were identified and three of these compartments were dated by Optically Stimulated Luminescence (OSL): Unit 1, raised terrace with circular and semicircular ponds (~150 ka); Unit 2, intermediate terrace with small ponds and waterlogged areas (~60 ka); Unit 3, low terrace with preserved paleochannels (~39–35 ka); and Unit 4, current river plain (>9 ka). The geomorphological units were correlated with previous studies downstream of the studied area and their sedimentary characteristics and depositional ages suggest that their genesis is linked to changes in climatic and hydrological conditions during the Late Quaternary. Units 1, 3, and 4 are considered extensions of the geomorphological units Taquaruçu, Fazenda Boa Vista, and Rio Paraná, respectively. Unit 2 is a compartment with unique morphological characteristics, therefore not correlated with units presented in previous works. Further, two main knickpoints were identified, suggesting an important control in the sedimentation and development of the terrace levels. Thus, this work brings new data on the evolutionary history of the Paraná River, which allows us to understand that the development of the terrace levels and the floodplain of the upper reaches are strongly controlled by the climatic changes that occurred during the Late Quaternary.
How to cite: Oliveira, S. C., Pupim, F. N., Stevaux, J. C., and Assine, M. L.: Late Quaternary evolution of the Upper Paraná River, southeast Brazil: a new geomorphological and chronological database, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11713, https://doi.org/10.5194/egusphere-egu21-11713, 2021.
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The Paraná River has being extensively studied in terms of its hydrological and sedimentological aspects, but the geological history of its fluvial plain is still poorly understood due to the lack of geochronological data. Most of the published studies are focused on the low and middle reaches, and the region upstream of the Porto Primavera dam is an area almost unknown in terms of geomorphic evolution. Here, we aim to investigate the succession of geological events responsible for the evolution and current configuration of the Upper Paraná River fluvial system, in the stretch between the Jupiá and Porto Primavera Hydroelectric Plants (São Paulo and Mato Grosso states). Thus, we used an integrated approach including remote sensing data, geomorphology, sedimentology, bathymetric profiles, and chronological methods. Four geomorphological compartments were identified and three of these compartments were dated by Optically Stimulated Luminescence (OSL): Unit 1, raised terrace with circular and semicircular ponds (~150 ka); Unit 2, intermediate terrace with small ponds and waterlogged areas (~60 ka); Unit 3, low terrace with preserved paleochannels (~39–35 ka); and Unit 4, current river plain (>9 ka). The geomorphological units were correlated with previous studies downstream of the studied area and their sedimentary characteristics and depositional ages suggest that their genesis is linked to changes in climatic and hydrological conditions during the Late Quaternary. Units 1, 3, and 4 are considered extensions of the geomorphological units Taquaruçu, Fazenda Boa Vista, and Rio Paraná, respectively. Unit 2 is a compartment with unique morphological characteristics, therefore not correlated with units presented in previous works. Further, two main knickpoints were identified, suggesting an important control in the sedimentation and development of the terrace levels. Thus, this work brings new data on the evolutionary history of the Paraná River, which allows us to understand that the development of the terrace levels and the floodplain of the upper reaches are strongly controlled by the climatic changes that occurred during the Late Quaternary.
How to cite: Oliveira, S. C., Pupim, F. N., Stevaux, J. C., and Assine, M. L.: Late Quaternary evolution of the Upper Paraná River, southeast Brazil: a new geomorphological and chronological database, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11713, https://doi.org/10.5194/egusphere-egu21-11713, 2021.
EGU21-16498 | vPICO presentations | GM5.1
How Quaternary climate changes build and erode sedimentary deposits in an intraplate large fluvial system: the São Francisco River, BrazilPatricia Mescolotti, Fabiano do Nascimento Pupim, Francisco Sérgio Bernardes Ladeira, André Oliveira Sawakuchi, Amanda Santa Catharina, and Mario Luis Assine
Climate, tectonic and sea level factors contribute to the geomorphic evolution of large rivers. Rivers draining settings where the tectonic activity and sea level influence are minors allow clearer signals from climate variation to be identified. Thus, rivers that run exclusively in tectonically quiescent areas and away from coastal regions are the most suitable targets to understand the climate drivers. In northeastern Brazil, the São Francisco River is one of the largest cratonic rivers in South America, with an extension of 2,900 km, and its thousand years evolution is registered by Quaternary deposits preserved as terraces. With the upper course in semi-humid settings, the São Franciscos flows northward, but with a watershed mostly under semi-arid conditions. Hence, the São Francisco River’s deposits are an excellent fluvial sedimentary record to shed light on how large tropical rivers responded to climatic changes of the Quaternary. We studied a 200 km stretch of the middle course of the São Francisco in the State of Bahia by using remote sensing methods and field surveys for geomorphological and sedimentological analyses combined with optically stimulated luminescence dating (OSL). We recognized at least four phases of fluvial aggradation (>90 ka; 65 to 39 ka; 18 to 9.5 ka and 380 years to recent) and three phases of incision (I1 - 85 to 65 ka; I2 - 39 to 18 ka and I3 - 9.5 to 1.0 ka). Two aggradation events and the incision event I2 are also observed in the upper course of the São Francisco River. The river incision events agree with precession insolation cycles (~25 ka) at latitude 10° S, which influence the rainfall in the area. The incision events occurred probably due to increased fluvial discharge produced by intensification of the South Atlantic Convergence Zone (SACZ), which has great influence on precipitation over the upper São Francisco river. Thus, we conclude that the aggradation-incision cycles of the São Francisco River during the last 100 ka are likely products of millennial precipitation variation, possibly related to precession cycles. The events of high sedimentation rate in the São Francisco river mouth are partially correlated with incision phases in its middle course. This suggests that sedimentation in plains of large plateau rivers can be decoupled from the coastal area.
Keywords: Late Quaternary, fluvial response, OSL dating, aggradation-incision cycles, precession cycles
How to cite: Mescolotti, P., do Nascimento Pupim, F., Bernardes Ladeira, F. S., Oliveira Sawakuchi, A., Santa Catharina, A., and Assine, M. L.: How Quaternary climate changes build and erode sedimentary deposits in an intraplate large fluvial system: the São Francisco River, Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16498, https://doi.org/10.5194/egusphere-egu21-16498, 2021.
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Climate, tectonic and sea level factors contribute to the geomorphic evolution of large rivers. Rivers draining settings where the tectonic activity and sea level influence are minors allow clearer signals from climate variation to be identified. Thus, rivers that run exclusively in tectonically quiescent areas and away from coastal regions are the most suitable targets to understand the climate drivers. In northeastern Brazil, the São Francisco River is one of the largest cratonic rivers in South America, with an extension of 2,900 km, and its thousand years evolution is registered by Quaternary deposits preserved as terraces. With the upper course in semi-humid settings, the São Franciscos flows northward, but with a watershed mostly under semi-arid conditions. Hence, the São Francisco River’s deposits are an excellent fluvial sedimentary record to shed light on how large tropical rivers responded to climatic changes of the Quaternary. We studied a 200 km stretch of the middle course of the São Francisco in the State of Bahia by using remote sensing methods and field surveys for geomorphological and sedimentological analyses combined with optically stimulated luminescence dating (OSL). We recognized at least four phases of fluvial aggradation (>90 ka; 65 to 39 ka; 18 to 9.5 ka and 380 years to recent) and three phases of incision (I1 - 85 to 65 ka; I2 - 39 to 18 ka and I3 - 9.5 to 1.0 ka). Two aggradation events and the incision event I2 are also observed in the upper course of the São Francisco River. The river incision events agree with precession insolation cycles (~25 ka) at latitude 10° S, which influence the rainfall in the area. The incision events occurred probably due to increased fluvial discharge produced by intensification of the South Atlantic Convergence Zone (SACZ), which has great influence on precipitation over the upper São Francisco river. Thus, we conclude that the aggradation-incision cycles of the São Francisco River during the last 100 ka are likely products of millennial precipitation variation, possibly related to precession cycles. The events of high sedimentation rate in the São Francisco river mouth are partially correlated with incision phases in its middle course. This suggests that sedimentation in plains of large plateau rivers can be decoupled from the coastal area.
Keywords: Late Quaternary, fluvial response, OSL dating, aggradation-incision cycles, precession cycles
How to cite: Mescolotti, P., do Nascimento Pupim, F., Bernardes Ladeira, F. S., Oliveira Sawakuchi, A., Santa Catharina, A., and Assine, M. L.: How Quaternary climate changes build and erode sedimentary deposits in an intraplate large fluvial system: the São Francisco River, Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16498, https://doi.org/10.5194/egusphere-egu21-16498, 2021.
EGU21-7592 | vPICO presentations | GM5.1
A novel combination of core drillings with 2D and 3D geophysical measurements helps to decipher the fluvial architecture of buried floodplain sediments of the Weiße Elster River (Central Germany)Hans von Suchodoletz, Christoph Zielhofer, Mathias Ulrich, Azra Khosravichenar, Jan Miera, Pierre Fütterer, Ulrich Veit, Peter Ettel, Lukas Werther, Helen Ballasus, and Ulrike Werban
Fluvial sediments are valuable archives of late Quaternary landscape evolution, paleoenvironmental changes and human-environmental interactions. However, given their complex and non-linear character their correct interpretation requires a good understanding of the fluvial architecture. The fluvial architecture describes the spatial arrangement and genetic interconnectedness of different types of fluvial sediments in a floodplain such as channel and overbank deposits. To properly map the different fluvial forms, their variations in composition and geometry must be understood in three dimensions. However, whereas investigations of the fluvial architecture are relatively easy in cohesive floodplain types with incised channel beds and large natural exposures, these are challenging in floodplains with buried stratigraphies where artificial exposures or corings are required.
We studied three cross sections through the floodplain of the middle and upper course of the Weiße Elster River in Central Germany by means of geophysical Electrical Resistivity Measurements (ERT) and closely spaced drillings. These 2D investigations were complemented by spatial geophysical 3D measurements of Electromagnetic Induction (EMI) in the surrounding areas of the cross sections. The latter technique allows fast mapping of larger areas, and was only rarely applied to fluvial systems so far. Our novel and cost-effective combination of core drillings with multidimensional geophysical measurements allowed to systematically reconstruct the fluvial architecture of larger areas of the Weiße Elster floodplain with high resolution, and thereby demonstrates its high value for fluvial geomorphology. Furthermore, in combination with ongoing numerical datings of the fluvial sediments these investigations form the base for precise conclusions about possible climatic and human drivers of the Holocene fluvial dynamics of the Weiße Elster River.
How to cite: von Suchodoletz, H., Zielhofer, C., Ulrich, M., Khosravichenar, A., Miera, J., Fütterer, P., Veit, U., Ettel, P., Werther, L., Ballasus, H., and Werban, U.: A novel combination of core drillings with 2D and 3D geophysical measurements helps to decipher the fluvial architecture of buried floodplain sediments of the Weiße Elster River (Central Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7592, https://doi.org/10.5194/egusphere-egu21-7592, 2021.
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Fluvial sediments are valuable archives of late Quaternary landscape evolution, paleoenvironmental changes and human-environmental interactions. However, given their complex and non-linear character their correct interpretation requires a good understanding of the fluvial architecture. The fluvial architecture describes the spatial arrangement and genetic interconnectedness of different types of fluvial sediments in a floodplain such as channel and overbank deposits. To properly map the different fluvial forms, their variations in composition and geometry must be understood in three dimensions. However, whereas investigations of the fluvial architecture are relatively easy in cohesive floodplain types with incised channel beds and large natural exposures, these are challenging in floodplains with buried stratigraphies where artificial exposures or corings are required.
We studied three cross sections through the floodplain of the middle and upper course of the Weiße Elster River in Central Germany by means of geophysical Electrical Resistivity Measurements (ERT) and closely spaced drillings. These 2D investigations were complemented by spatial geophysical 3D measurements of Electromagnetic Induction (EMI) in the surrounding areas of the cross sections. The latter technique allows fast mapping of larger areas, and was only rarely applied to fluvial systems so far. Our novel and cost-effective combination of core drillings with multidimensional geophysical measurements allowed to systematically reconstruct the fluvial architecture of larger areas of the Weiße Elster floodplain with high resolution, and thereby demonstrates its high value for fluvial geomorphology. Furthermore, in combination with ongoing numerical datings of the fluvial sediments these investigations form the base for precise conclusions about possible climatic and human drivers of the Holocene fluvial dynamics of the Weiße Elster River.
How to cite: von Suchodoletz, H., Zielhofer, C., Ulrich, M., Khosravichenar, A., Miera, J., Fütterer, P., Veit, U., Ettel, P., Werther, L., Ballasus, H., and Werban, U.: A novel combination of core drillings with 2D and 3D geophysical measurements helps to decipher the fluvial architecture of buried floodplain sediments of the Weiße Elster River (Central Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7592, https://doi.org/10.5194/egusphere-egu21-7592, 2021.
EGU21-6701 | vPICO presentations | GM5.1
Provenance Determination of Paleochannel Infillings in the Alsatian Upper Rhine Floodplain Using Mid-Infrared Spectroscopy-Discriminant AnalysisMubarak Abdulkarim, Stoil Chapkanski, Damien Ertlen, Claire Rambeau, Laurent Schmitt, Louis Le Bouteiller, and Frank Preusser
The Alsatian Upper Rhine floodplain (northeastern France) is characterized by a complex anastomosing network of paleochannels inherited from Late Glacial braided fluvial pattern of the Rhine system. These paleochannels are filled by mixed or stratified clastic and organic sediments originating from different sediment sources. Identifying these sediments' provenance is critically important for understanding past surface processes and reconstructing the Upper Rhine Valley evolution in the course of the Holocene. This study employed mid-infrared spectroscopy to determine the source of sediments and, therefore, understand which rivers may have contributed to the paleochannel infilling and establish the main patterns of filling through time. Sediment samples with unknown sedimentary provenance were collected in 16 sites consisting of paleochannels and the Ill River's levees. Mid-Infrared spectroscopic analyses were carried out on powdered (< 2 mm) samples using a Frontier Spectrometer (PerkinElmer) equipped with Diffuse Reflectance Infrared Fourier Transform accessory. Statistical analysis (Discriminant Analysis - DA) was performed to compare the spectral signatures obtained from the samples and a previously established reference spectral dataset (Chapkanski et al. 2020) covering potential sediment sources in the Upper Rhine area (the Rhine, Ill, and Vosges tributaries). The results showed well-contrasted sediment sources, with multiple rivers contributing to the paleochannel infilling history. The sediments were found to originate from the Rhine and Ill River systems and, to a lesser extent, Vosges tributaries. Some channels have an exclusively Alpine Rhine catchment origin while others showed purely Ill signatures. However, for most of the channels, infilling sources changed over time, presenting a relatively complex mixture of multiple sediment sources, indicating the lateral shifting of the two rivers within the alluvial plain. The results confirm that Mid-infrared spectroscopy (MIRS), combined with discriminant analysis, can give highly-specific determinations to sediments' sources. Thus MIRS-DA technique shows the potential of its being applicable as a rapid, low-cost, and efficient alternative method for provenance analysis of fluvial deposits in large, complex floodplains.
How to cite: Abdulkarim, M., Chapkanski, S., Ertlen, D., Rambeau, C., Schmitt, L., Le Bouteiller, L., and Preusser, F.: Provenance Determination of Paleochannel Infillings in the Alsatian Upper Rhine Floodplain Using Mid-Infrared Spectroscopy-Discriminant Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6701, https://doi.org/10.5194/egusphere-egu21-6701, 2021.
The Alsatian Upper Rhine floodplain (northeastern France) is characterized by a complex anastomosing network of paleochannels inherited from Late Glacial braided fluvial pattern of the Rhine system. These paleochannels are filled by mixed or stratified clastic and organic sediments originating from different sediment sources. Identifying these sediments' provenance is critically important for understanding past surface processes and reconstructing the Upper Rhine Valley evolution in the course of the Holocene. This study employed mid-infrared spectroscopy to determine the source of sediments and, therefore, understand which rivers may have contributed to the paleochannel infilling and establish the main patterns of filling through time. Sediment samples with unknown sedimentary provenance were collected in 16 sites consisting of paleochannels and the Ill River's levees. Mid-Infrared spectroscopic analyses were carried out on powdered (< 2 mm) samples using a Frontier Spectrometer (PerkinElmer) equipped with Diffuse Reflectance Infrared Fourier Transform accessory. Statistical analysis (Discriminant Analysis - DA) was performed to compare the spectral signatures obtained from the samples and a previously established reference spectral dataset (Chapkanski et al. 2020) covering potential sediment sources in the Upper Rhine area (the Rhine, Ill, and Vosges tributaries). The results showed well-contrasted sediment sources, with multiple rivers contributing to the paleochannel infilling history. The sediments were found to originate from the Rhine and Ill River systems and, to a lesser extent, Vosges tributaries. Some channels have an exclusively Alpine Rhine catchment origin while others showed purely Ill signatures. However, for most of the channels, infilling sources changed over time, presenting a relatively complex mixture of multiple sediment sources, indicating the lateral shifting of the two rivers within the alluvial plain. The results confirm that Mid-infrared spectroscopy (MIRS), combined with discriminant analysis, can give highly-specific determinations to sediments' sources. Thus MIRS-DA technique shows the potential of its being applicable as a rapid, low-cost, and efficient alternative method for provenance analysis of fluvial deposits in large, complex floodplains.
How to cite: Abdulkarim, M., Chapkanski, S., Ertlen, D., Rambeau, C., Schmitt, L., Le Bouteiller, L., and Preusser, F.: Provenance Determination of Paleochannel Infillings in the Alsatian Upper Rhine Floodplain Using Mid-Infrared Spectroscopy-Discriminant Analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6701, https://doi.org/10.5194/egusphere-egu21-6701, 2021.
EGU21-4979 | vPICO presentations | GM5.1
Pliocene-Quaternary river-terrace sequences in intramontane basins in the south-eastern Alpine foreland (Slovenia): characterization of morphostratigraphy and provenanceEva Mencin Gale, Petra Jamšek Rupnik, Miloš Bavec, Mirka Trajanova, Luka Gale, Flavio S. Anselmetti, and Andrej Šmuc
This study focuses on the Pliocene-Quaternary sedimentary evolution of the fluvial systems in the Slovenj Gradec, Nazarje, Velenje, Celje, Drava-Ptuj and Krško Basins in the south-eastern Alpine foreland, Slovenia. The main aim was to determine the composition, morphostratigraphy, provenance, sedimentary environment and age of the deposits using geomorphological, sedimentological, geochemical, mineralogical and biostratigraphical methods. Pliocene-Quaternary sediments were deposited in fluvial (braided and wandering river systems) and alluvial/colluvial fan environments. The sediments are preserved in the terrace staircase sequences, formation of which is strongly controlled by tectonic activity. Based on geomorphological analyses, low-, middle- and high-level terrace groups were constrained and tentatively attributed to Late Pleistocene, Middle Pleistocene, and Plio-Early Pleistocene, respectively. The provenance analyses focused on the Plio-Early Pleistocene sediments and included lithological and microfacies analyses of the clasts. Based on the provenance analyses and published data, the long-term development of the drainage network was interpreted. Major changes occurred during the transition from Miocene-Pliocene and at the latest at Plio-Early Pleistocene the drainage network reached conformity with the present one. Overall, the spatial distribution of the Pliocene-Quaternary landforms revealed tectonic activity in intramontane basins during their development, from which the landscape evolution was deduced.
How to cite: Mencin Gale, E., Jamšek Rupnik, P., Bavec, M., Trajanova, M., Gale, L., Anselmetti, F. S., and Šmuc, A.: Pliocene-Quaternary river-terrace sequences in intramontane basins in the south-eastern Alpine foreland (Slovenia): characterization of morphostratigraphy and provenance, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4979, https://doi.org/10.5194/egusphere-egu21-4979, 2021.
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This study focuses on the Pliocene-Quaternary sedimentary evolution of the fluvial systems in the Slovenj Gradec, Nazarje, Velenje, Celje, Drava-Ptuj and Krško Basins in the south-eastern Alpine foreland, Slovenia. The main aim was to determine the composition, morphostratigraphy, provenance, sedimentary environment and age of the deposits using geomorphological, sedimentological, geochemical, mineralogical and biostratigraphical methods. Pliocene-Quaternary sediments were deposited in fluvial (braided and wandering river systems) and alluvial/colluvial fan environments. The sediments are preserved in the terrace staircase sequences, formation of which is strongly controlled by tectonic activity. Based on geomorphological analyses, low-, middle- and high-level terrace groups were constrained and tentatively attributed to Late Pleistocene, Middle Pleistocene, and Plio-Early Pleistocene, respectively. The provenance analyses focused on the Plio-Early Pleistocene sediments and included lithological and microfacies analyses of the clasts. Based on the provenance analyses and published data, the long-term development of the drainage network was interpreted. Major changes occurred during the transition from Miocene-Pliocene and at the latest at Plio-Early Pleistocene the drainage network reached conformity with the present one. Overall, the spatial distribution of the Pliocene-Quaternary landforms revealed tectonic activity in intramontane basins during their development, from which the landscape evolution was deduced.
How to cite: Mencin Gale, E., Jamšek Rupnik, P., Bavec, M., Trajanova, M., Gale, L., Anselmetti, F. S., and Šmuc, A.: Pliocene-Quaternary river-terrace sequences in intramontane basins in the south-eastern Alpine foreland (Slovenia): characterization of morphostratigraphy and provenance, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4979, https://doi.org/10.5194/egusphere-egu21-4979, 2021.
EGU21-12502 | vPICO presentations | GM5.1
Morphological evolution of the middle and lower Seine valley during the Quaternary period.Kim Genuite, Carole Nehme, Daniel Ballesteros, Dominique Todisco, and Damase Mouralis
The Seine river (France) drains today a catchment area of 80,000 km2 covering almost the northern part of France. Despite its importance, few studies focused on the Seine catchment and its landscape evolution, unlike the Somme basin, which remains a European reference for the Quaternary, because of to the numerous archaeological sites it contains. The middle and lower Seine valley in Normandy shows nevertheless a particular meandering fluvial dynamic and a succession of fluvial terraces over 120 m height, dated back to Early Quaternary. Previous works focused on the stratigraphy of alluvial sequences and led to the accurate characterization of lower fluvial and estuarine levels from Marine Isotope Stage (MIS) 1 to MIS 11. The alluvial terraces comprise also various Acheulean industries, showing human settlements in the valley for at least 400,000 years. Such archaeological remnants were retrieved in Saint-Pierre-Lès-Elbeuf, Tourville-la-Rivière, Vernon and La Celle.
Nowadays, the Seine connects to the drowned lower Seine course which continues in the Channel. This submerged part was subaerial during the last glacial cycle. Presently, the lower Seine course is still under the influence of marine tidal effects up to la Bouille (around 30 km from the coast). Additionally, estuarine deposits filled the valley up to Les Andelys (around 80 km from the coast) during the Holocene transgression and cover the penultimate and last glacial alluvial terraces. Nevertheless, the dynamic of the Seine river is broadly identified with few chronological constraints, but without any morphometric analysis combined with stratigraphical study.
This work provides a review of the stratigraphy of the quaternary alluvial deposits in the lower part of the Seine Valley, together with new morphometrical analysis of the paleo-meanders located at higher altitudes. The analysis of the paleo-morphologies compared with high-resolution digital elevation model (DEM), provides new means for constraining the fluvial incision and deposition over long distances and periods, and helps to discuss the river evolution related with quaternary uplift, catchment evolution and glacio-eustatic dynamics.
How to cite: Genuite, K., Nehme, C., Ballesteros, D., Todisco, D., and Mouralis, D.: Morphological evolution of the middle and lower Seine valley during the Quaternary period., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12502, https://doi.org/10.5194/egusphere-egu21-12502, 2021.
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The Seine river (France) drains today a catchment area of 80,000 km2 covering almost the northern part of France. Despite its importance, few studies focused on the Seine catchment and its landscape evolution, unlike the Somme basin, which remains a European reference for the Quaternary, because of to the numerous archaeological sites it contains. The middle and lower Seine valley in Normandy shows nevertheless a particular meandering fluvial dynamic and a succession of fluvial terraces over 120 m height, dated back to Early Quaternary. Previous works focused on the stratigraphy of alluvial sequences and led to the accurate characterization of lower fluvial and estuarine levels from Marine Isotope Stage (MIS) 1 to MIS 11. The alluvial terraces comprise also various Acheulean industries, showing human settlements in the valley for at least 400,000 years. Such archaeological remnants were retrieved in Saint-Pierre-Lès-Elbeuf, Tourville-la-Rivière, Vernon and La Celle.
Nowadays, the Seine connects to the drowned lower Seine course which continues in the Channel. This submerged part was subaerial during the last glacial cycle. Presently, the lower Seine course is still under the influence of marine tidal effects up to la Bouille (around 30 km from the coast). Additionally, estuarine deposits filled the valley up to Les Andelys (around 80 km from the coast) during the Holocene transgression and cover the penultimate and last glacial alluvial terraces. Nevertheless, the dynamic of the Seine river is broadly identified with few chronological constraints, but without any morphometric analysis combined with stratigraphical study.
This work provides a review of the stratigraphy of the quaternary alluvial deposits in the lower part of the Seine Valley, together with new morphometrical analysis of the paleo-meanders located at higher altitudes. The analysis of the paleo-morphologies compared with high-resolution digital elevation model (DEM), provides new means for constraining the fluvial incision and deposition over long distances and periods, and helps to discuss the river evolution related with quaternary uplift, catchment evolution and glacio-eustatic dynamics.
How to cite: Genuite, K., Nehme, C., Ballesteros, D., Todisco, D., and Mouralis, D.: Morphological evolution of the middle and lower Seine valley during the Quaternary period., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12502, https://doi.org/10.5194/egusphere-egu21-12502, 2021.
EGU21-14718 | vPICO presentations | GM5.1
Formation and infill of the Late Glacial incised valley of Concordia Sagittaria (Tagliamento River, NE Italy)Alessandro Fontana, Livio Ronchi, Kim Cohen, Esther Stouthamer, Timme Donders, Kim Hissink, and Sandra Donnici
At the end of LGM the alluvial plains extending along the southern side of the Alps experienced a strong phase of fluvial entrenchment because of the impressive decrease of sedimentary input, related to the withdrawn of the Alpine glaciers within their valleys. Since 19 ka cal BP and up to Early Holocene, few incised valleys formed from the apex of the alluvial megafans to their distal sector but, along the northern Adriatic, the mid and late Holocene fluvial and coastal depositions have largely buried these landforms. During the Late Glacial the incised valleys were the only fluvial corridors where transport and deposition of sediments could occur in the whole plain.
We investigated the distal sector of the alluvial megafan of Tagliamento River through the analysis of a dataset consisting of ca. 2300 mechanical and hand-made cores. These data, compared with LIDAR-derived DEM, radiocarbon and paleoenvironmental analyses, allowed a detailed reconstruction of the formation and evolution of the buried incised valley characterizing the area of Portogruaro and Concordia Sagittaria. The valley has been traced for over 25 km, is up to 1.2 km wide and with a depth of 20 m below the top of LGM surface.
The erosive valley has been mainly formed between 19 and 14 ka cal BP, leading also to its partial infill with about 10 m of gravels, that arrived up to the present coast. The fluvial activity has been after limited to the deposition of fine sediment almost until the end of Late Glacial and, according to paleobotanical information, for the first time in the Venetian–Friulian Plain, these deposits recorded the vegetation of the Younger Dryas period.
After the disconnection from active Tagliamento, swampy environments occupied the valley bottom and the Holocene marine transgression started to indirectly affect the valley around 9.5 ka cal BP, contrasting the drainage and favouring the formation of widespread lacustrine environments. Since 8 ka cal BP lagoon entered in the valley and, following the sea-level rise, led to the deposition of a ca. 15 m thick unit of lagoon muds up to historical time. The infill of the valley documents the evidence of anthropogenic activity since 6-5 ka cal BP, probably in relation to wood clearance and soil degradation. Anyhow, significant human impact occurred during Iron and Roman Age, when Concordia became an important city. In 6th century AD high-magnitude floods deposited up to 5 m of sediments and largely obliterated the valley.
The detailed 3D reconstruction of the valley of Concordia allowed also to highlight the importance of the groundwater-fed streams in affecting the formation of this and other large incised valleys of Tagliamento. In particular, we produced evidence that river piracy by minor rivers triggered the creation of other incised valleys in the distal sector of Tagliamento megafan.
The buried incised valley of Concordia can represent a reference model also for describing the fluvial evolution of the other main Alpine rivers in the coastal sector of the whole Venetian-Friulian Plain during Late Glacial and Early Holocene.
How to cite: Fontana, A., Ronchi, L., Cohen, K., Stouthamer, E., Donders, T., Hissink, K., and Donnici, S.: Formation and infill of the Late Glacial incised valley of Concordia Sagittaria (Tagliamento River, NE Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14718, https://doi.org/10.5194/egusphere-egu21-14718, 2021.
At the end of LGM the alluvial plains extending along the southern side of the Alps experienced a strong phase of fluvial entrenchment because of the impressive decrease of sedimentary input, related to the withdrawn of the Alpine glaciers within their valleys. Since 19 ka cal BP and up to Early Holocene, few incised valleys formed from the apex of the alluvial megafans to their distal sector but, along the northern Adriatic, the mid and late Holocene fluvial and coastal depositions have largely buried these landforms. During the Late Glacial the incised valleys were the only fluvial corridors where transport and deposition of sediments could occur in the whole plain.
We investigated the distal sector of the alluvial megafan of Tagliamento River through the analysis of a dataset consisting of ca. 2300 mechanical and hand-made cores. These data, compared with LIDAR-derived DEM, radiocarbon and paleoenvironmental analyses, allowed a detailed reconstruction of the formation and evolution of the buried incised valley characterizing the area of Portogruaro and Concordia Sagittaria. The valley has been traced for over 25 km, is up to 1.2 km wide and with a depth of 20 m below the top of LGM surface.
The erosive valley has been mainly formed between 19 and 14 ka cal BP, leading also to its partial infill with about 10 m of gravels, that arrived up to the present coast. The fluvial activity has been after limited to the deposition of fine sediment almost until the end of Late Glacial and, according to paleobotanical information, for the first time in the Venetian–Friulian Plain, these deposits recorded the vegetation of the Younger Dryas period.
After the disconnection from active Tagliamento, swampy environments occupied the valley bottom and the Holocene marine transgression started to indirectly affect the valley around 9.5 ka cal BP, contrasting the drainage and favouring the formation of widespread lacustrine environments. Since 8 ka cal BP lagoon entered in the valley and, following the sea-level rise, led to the deposition of a ca. 15 m thick unit of lagoon muds up to historical time. The infill of the valley documents the evidence of anthropogenic activity since 6-5 ka cal BP, probably in relation to wood clearance and soil degradation. Anyhow, significant human impact occurred during Iron and Roman Age, when Concordia became an important city. In 6th century AD high-magnitude floods deposited up to 5 m of sediments and largely obliterated the valley.
The detailed 3D reconstruction of the valley of Concordia allowed also to highlight the importance of the groundwater-fed streams in affecting the formation of this and other large incised valleys of Tagliamento. In particular, we produced evidence that river piracy by minor rivers triggered the creation of other incised valleys in the distal sector of Tagliamento megafan.
The buried incised valley of Concordia can represent a reference model also for describing the fluvial evolution of the other main Alpine rivers in the coastal sector of the whole Venetian-Friulian Plain during Late Glacial and Early Holocene.
How to cite: Fontana, A., Ronchi, L., Cohen, K., Stouthamer, E., Donders, T., Hissink, K., and Donnici, S.: Formation and infill of the Late Glacial incised valley of Concordia Sagittaria (Tagliamento River, NE Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14718, https://doi.org/10.5194/egusphere-egu21-14718, 2021.
EGU21-13533 | vPICO presentations | GM5.1
Alluvial deposits evolution in the Inaouene river valley (Morocco) during late Pleistocene and Holocene epoch.Mohammed Lghamour, Lhoucine Karrat, Vincenzo Picotti, Irka Hajdas, Negar Haghipour, Giulia Guidobaldi, and Karin Wyss Heeb
The Inaouène wadi is a river located in the northern region of Morocco. Its catchment area covers about 5124 km² with an average altitude of 800 m. The tributaries drain the marly reliefs of the Prerif in the northern side, as well as its southern ones are crossing the liasic carbonate and the Paleozoic crystalline rocks of the last Middle Atlas foothills. This region is characterised by a semi-arid Mediterranean climate influenced by the ocean oscillations, the average annual rainfall records 600 mm with a very significant spatial and interannual irregularity.
Along the major part of its flow, the Inaouène river has cut its bed between the Prerif and the Middle Atlas belts, by following the foreland corridor that separates them. From a pass (Touaher) that marks the corridor closing, the river valley widens from East to West, forming an alluvial plain with a maximum width of 5 km incised by a meandering and highly sinuous stream.
Alluvial deposits in this valley are more developed on the Atlas side than at the Prerif foot; At least five levels representing the vestiges of the Lower and Middle Pleistocene terraces are present in the landscape.
More recent deposits occupy the valley floor, they constitute a more homogeneous surface showing low terraces abrupts and lateral limits between different sedimentary units. These alluvial deposits correspond to the terminal Pleistocene, middle and upper Holocene epoch. About 30 samples of charcoal and TOC have been selected and analysed using the AMS 14C dating. Due to the scarcity of organic matter, some of the samples contained less than 0.1 mg of carbon and had to be analysed using the gas ion source (GIS) interface of the MICADAS (Haghipour et al., 2019; Wacker et al.,2013). 12 sections were described in the field and of which 8 sections were analysed regarding grain size, mineralogical composition, carbonate content as well as organic matter in soils and sediments.
The analysis results indicate that the late Pleistocene is characterised by a high fluvial activity reflected by the development of braided system river and so coarse material, while fine deposits of floodplains are more abundant during the Holocene.
……...........
Haghipour, N., Ausin, B., Usman, M. O., Ishikawa, N., Wacker, L., Welte, C., Ueda, K., and Eglinton, T. I., 2019, Compound-Specific Radiocarbon Analysis by Elemental Analyzer-Accelerator Mass Spectrometry: Precision and Limitations: Analytical Chemistry, v. 91, no. 3, p. 2042-2049.
Wacker, L., Fahrni, S., Hajdas, I., Molnar, M., Synal, H., Szidat, S., and Zhang, Y., 2013, A versatile gas interface for routine radiocarbon analysis with a gas ion source: Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, v. 294, p. 315-319.
How to cite: Lghamour, M., Karrat, L., Picotti, V., Hajdas, I., Haghipour, N., Guidobaldi, G., and Wyss Heeb, K.: Alluvial deposits evolution in the Inaouene river valley (Morocco) during late Pleistocene and Holocene epoch., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13533, https://doi.org/10.5194/egusphere-egu21-13533, 2021.
The Inaouène wadi is a river located in the northern region of Morocco. Its catchment area covers about 5124 km² with an average altitude of 800 m. The tributaries drain the marly reliefs of the Prerif in the northern side, as well as its southern ones are crossing the liasic carbonate and the Paleozoic crystalline rocks of the last Middle Atlas foothills. This region is characterised by a semi-arid Mediterranean climate influenced by the ocean oscillations, the average annual rainfall records 600 mm with a very significant spatial and interannual irregularity.
Along the major part of its flow, the Inaouène river has cut its bed between the Prerif and the Middle Atlas belts, by following the foreland corridor that separates them. From a pass (Touaher) that marks the corridor closing, the river valley widens from East to West, forming an alluvial plain with a maximum width of 5 km incised by a meandering and highly sinuous stream.
Alluvial deposits in this valley are more developed on the Atlas side than at the Prerif foot; At least five levels representing the vestiges of the Lower and Middle Pleistocene terraces are present in the landscape.
More recent deposits occupy the valley floor, they constitute a more homogeneous surface showing low terraces abrupts and lateral limits between different sedimentary units. These alluvial deposits correspond to the terminal Pleistocene, middle and upper Holocene epoch. About 30 samples of charcoal and TOC have been selected and analysed using the AMS 14C dating. Due to the scarcity of organic matter, some of the samples contained less than 0.1 mg of carbon and had to be analysed using the gas ion source (GIS) interface of the MICADAS (Haghipour et al., 2019; Wacker et al.,2013). 12 sections were described in the field and of which 8 sections were analysed regarding grain size, mineralogical composition, carbonate content as well as organic matter in soils and sediments.
The analysis results indicate that the late Pleistocene is characterised by a high fluvial activity reflected by the development of braided system river and so coarse material, while fine deposits of floodplains are more abundant during the Holocene.
……...........
Haghipour, N., Ausin, B., Usman, M. O., Ishikawa, N., Wacker, L., Welte, C., Ueda, K., and Eglinton, T. I., 2019, Compound-Specific Radiocarbon Analysis by Elemental Analyzer-Accelerator Mass Spectrometry: Precision and Limitations: Analytical Chemistry, v. 91, no. 3, p. 2042-2049.
Wacker, L., Fahrni, S., Hajdas, I., Molnar, M., Synal, H., Szidat, S., and Zhang, Y., 2013, A versatile gas interface for routine radiocarbon analysis with a gas ion source: Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, v. 294, p. 315-319.
How to cite: Lghamour, M., Karrat, L., Picotti, V., Hajdas, I., Haghipour, N., Guidobaldi, G., and Wyss Heeb, K.: Alluvial deposits evolution in the Inaouene river valley (Morocco) during late Pleistocene and Holocene epoch., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13533, https://doi.org/10.5194/egusphere-egu21-13533, 2021.
EGU21-13188 | vPICO presentations | GM5.1
Quantification of fluvial-peat interactions in the Pikeville formation Central Appalachian Basin, USA.Peter Wooldridge, Robert Duller, Rhodri Jerrett, and Kyle Straub
Basin-scale fluvial architecture is, to a large extent, determined by the ability of river systems to migrate and avulse across their own floodplain. River avulsion takes place when a river aggrades by one channel depth to achieve super-elevation above the surrounding floodplain. However, peat enhancement of floodplain aggradation is likely to affect this fluvial behaviour and has received little attention. The interaction between river channels and peat-dominated floodplains is likely to have the effect of inhibiting or prolonging the conditions required for river avulsion, and so will impact on basin scale architecture during prolonged peat accumulation on floodplains. To elucidate and quantify the nature of this channel-floodplain interaction we investigate the coal-bearing clastic interval of the Carboniferous Pikeville Formation, Central Appalachian Basin, USA. Using a combination of well data and outcrop data, two coal horizons and intervening sand bodies, were mapped across an area of 5700 km2 to ascertain overall basin-scale architecture. Comparison of the accumulation rate of the coal units (corrected for decompaction) with the synchronously deposited sand bodies suggests that extensive and rapid peat accumulation can increase avulsion timescales by 3 orders of magnitude and dramatically alter basin-scale fluvial architecture.
How to cite: Wooldridge, P., Duller, R., Jerrett, R., and Straub, K.: Quantification of fluvial-peat interactions in the Pikeville formation Central Appalachian Basin, USA., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13188, https://doi.org/10.5194/egusphere-egu21-13188, 2021.
Basin-scale fluvial architecture is, to a large extent, determined by the ability of river systems to migrate and avulse across their own floodplain. River avulsion takes place when a river aggrades by one channel depth to achieve super-elevation above the surrounding floodplain. However, peat enhancement of floodplain aggradation is likely to affect this fluvial behaviour and has received little attention. The interaction between river channels and peat-dominated floodplains is likely to have the effect of inhibiting or prolonging the conditions required for river avulsion, and so will impact on basin scale architecture during prolonged peat accumulation on floodplains. To elucidate and quantify the nature of this channel-floodplain interaction we investigate the coal-bearing clastic interval of the Carboniferous Pikeville Formation, Central Appalachian Basin, USA. Using a combination of well data and outcrop data, two coal horizons and intervening sand bodies, were mapped across an area of 5700 km2 to ascertain overall basin-scale architecture. Comparison of the accumulation rate of the coal units (corrected for decompaction) with the synchronously deposited sand bodies suggests that extensive and rapid peat accumulation can increase avulsion timescales by 3 orders of magnitude and dramatically alter basin-scale fluvial architecture.
How to cite: Wooldridge, P., Duller, R., Jerrett, R., and Straub, K.: Quantification of fluvial-peat interactions in the Pikeville formation Central Appalachian Basin, USA., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13188, https://doi.org/10.5194/egusphere-egu21-13188, 2021.
GM5.2 – Advancing theory and modelling of river systems and erosion mechanics
EGU21-13485 | vPICO presentations | GM5.2
Riparian Vegetation Dynamic and River Stability on Intermittent Rivers: Impact of Water Transfer Project on Tropical DrylandsCamilla Santos, Leonardo Dantas Martins, Kenia Sousa da Cruz, and Jonas Otaviano Praça de Souza
Rivers on semiarid landscapes typically are characterised by sandy geomorphic units and riverbanks, a natural factor that enhances lateral mobility. Vegetation cover is a crucial factor on lateral instability due to its impact on riverbank and geomorphic units erosion resistance. Nevertheless, riparian vegetation on intermittent and ephemeral channels show growing patterns directly affect by the flow temporality, that controls the water availability. Extended dry intervals hinder the succession ecological on geomorphic units, like bars and islands, and riverbanks and retard the growing process. This work analysed the effects of hydrological changes, caused by one water transfer project, on the bio-geomorphological patterns on riverbanks of a main intermittent river of Brazilian Drylands. Flow data series was used to understand the hydrological pattern changes; Google Earth images and UAV surveys to analyse the vegetation and riverbank behaviour from 2008 to 2020. Lastly, the identification of riverbank material resistance was based on sedimentology analysis. The water transfer Project PISF (Projeto de Integração do São Francisco), operating since 2017 March, increase the average flow days from 137,5 to 260/300 days and decreasing the continuous dry period from 200 to 30/45 days. The impact on average annual discharge was slightest, whereas the average water transfer volume was 3m3/s. It is essential to highlight the short period of data posterior to the water transfer and the non-regulatiry of water volume transferred; what limits the temporal representativity of the results. There were different types, and level of impacts depending on the river reach characteristics. However, in general, the longer flow permanence increases riparian vegetation density, vertical incision, and lateral stability. Riparian vegetation cover increase, from 20% to 100% on the 9 reaches analysed, across the entire channel, including bedrock reaches, with riverbanks having some rock outcrops percentage. The main changes were on sand bed reaches, that used to have, before 2017, a dynamic braiding pattern, without a clear main incised channel and thalweg shifting. Afterwards, the flow permanence, due to the water transfer project, enabled herbaceous stratus temporal continuity, contributing to surface stability and progressive bushes/trees cover growing. Lastly, the increase in lateral stability, mainly on thalweg position, facilitates the vertical incision on the sand bed reaches, representing 85% of this channel. As a secondary impact, there were necessary, to the road network, built floodway crossings at several points, which changes the channel morphology and the (dis)connectivity process. It can generate distinct channel position and morphology changes causing water and sediment retention upstream and erosion downstream. Lastly, there were slight differences in textural characteristics on riverbanks and geomorphic units, with a rise in fine sediment on the most vegetated areas/units. This analysis reveals that a fast response of riparian vegetation and sand bed reaches morphology, affecting the bio-geomorphological process and all environmental dynamic. It points to fundamental elements which need monitoring after hydrological changes, especially to intermittent and ephemeral rivers.
How to cite: Santos, C., Dantas Martins, L., Sousa da Cruz, K., and Otaviano Praça de Souza, J.: Riparian Vegetation Dynamic and River Stability on Intermittent Rivers: Impact of Water Transfer Project on Tropical Drylands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13485, https://doi.org/10.5194/egusphere-egu21-13485, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Rivers on semiarid landscapes typically are characterised by sandy geomorphic units and riverbanks, a natural factor that enhances lateral mobility. Vegetation cover is a crucial factor on lateral instability due to its impact on riverbank and geomorphic units erosion resistance. Nevertheless, riparian vegetation on intermittent and ephemeral channels show growing patterns directly affect by the flow temporality, that controls the water availability. Extended dry intervals hinder the succession ecological on geomorphic units, like bars and islands, and riverbanks and retard the growing process. This work analysed the effects of hydrological changes, caused by one water transfer project, on the bio-geomorphological patterns on riverbanks of a main intermittent river of Brazilian Drylands. Flow data series was used to understand the hydrological pattern changes; Google Earth images and UAV surveys to analyse the vegetation and riverbank behaviour from 2008 to 2020. Lastly, the identification of riverbank material resistance was based on sedimentology analysis. The water transfer Project PISF (Projeto de Integração do São Francisco), operating since 2017 March, increase the average flow days from 137,5 to 260/300 days and decreasing the continuous dry period from 200 to 30/45 days. The impact on average annual discharge was slightest, whereas the average water transfer volume was 3m3/s. It is essential to highlight the short period of data posterior to the water transfer and the non-regulatiry of water volume transferred; what limits the temporal representativity of the results. There were different types, and level of impacts depending on the river reach characteristics. However, in general, the longer flow permanence increases riparian vegetation density, vertical incision, and lateral stability. Riparian vegetation cover increase, from 20% to 100% on the 9 reaches analysed, across the entire channel, including bedrock reaches, with riverbanks having some rock outcrops percentage. The main changes were on sand bed reaches, that used to have, before 2017, a dynamic braiding pattern, without a clear main incised channel and thalweg shifting. Afterwards, the flow permanence, due to the water transfer project, enabled herbaceous stratus temporal continuity, contributing to surface stability and progressive bushes/trees cover growing. Lastly, the increase in lateral stability, mainly on thalweg position, facilitates the vertical incision on the sand bed reaches, representing 85% of this channel. As a secondary impact, there were necessary, to the road network, built floodway crossings at several points, which changes the channel morphology and the (dis)connectivity process. It can generate distinct channel position and morphology changes causing water and sediment retention upstream and erosion downstream. Lastly, there were slight differences in textural characteristics on riverbanks and geomorphic units, with a rise in fine sediment on the most vegetated areas/units. This analysis reveals that a fast response of riparian vegetation and sand bed reaches morphology, affecting the bio-geomorphological process and all environmental dynamic. It points to fundamental elements which need monitoring after hydrological changes, especially to intermittent and ephemeral rivers.
How to cite: Santos, C., Dantas Martins, L., Sousa da Cruz, K., and Otaviano Praça de Souza, J.: Riparian Vegetation Dynamic and River Stability on Intermittent Rivers: Impact of Water Transfer Project on Tropical Drylands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13485, https://doi.org/10.5194/egusphere-egu21-13485, 2021.
EGU21-14337 | vPICO presentations | GM5.2
River bed dynamic monitoring on ephemeral/intermittent rivers – sand-bed response on topical drylandsJonas Souza, Fernando Alexandre, and Gabriel Monteiro
Intermittent and ephemeral rivers, prevalent in dryland areas, have less monitoring data than perennial rivers worldwide. It hinders studies about hydro-geomorphology dynamics on these streams, which is especially complex in rain-fed flow regime on tropical rivers. Irregular rain patterns characterise the tropical drylands, which reverberate in the hydro-geomorphological dynamic. Unmanned Aerial Vehicles (UAV) survey is an efficient and cheap technic to monitor these streams since the dry periods expose the riverbed surface. This research aimed to analyse the hydro-geomorphology dynamic on sandy bed reaches of an intermittent tropical river. Five UAV surveys were realised on eight sandy reaches, from headwater to the outlet, between 2020 January 7 and December 9 in the Tigre River – Brazilian Drylands –, a 30Km ephemeral/intermittent. The UAV photos from all the surveys were co-aligned to create matching DEMs. We compared the DEMs to identify channel morphology changes, calculating differences in the riverbed and riverbank. The DEMs comparison enabled to calculate the erosion and sedimentation volume to each reach. Simultaneously, we installed crest stages gauges to monitor the peak water level between the surveys. Lastly, we used five rain gauges to identify the necessary rain volume that generates flow events. The 2020 annual rain volume was close to the historical average, between 530mm and 700mm, on the pediments, up to 1000mm on highland headwaters. The average potential evapotranspiration is around 1400-1800mm/year, due to the tropical climate. There was an average of 3.4 extreme rainfall daily events (over 50mm/day) during the year and the rainest period was between March 15 to 26th when rained from 134mm to 376mm around the watershed. The surveys between January 18 and March 8 identified insignificant morphology changes on eight reaches. The peak water levels were between no flow to 0.49m; only the outlet reach showed slight erosion and water level reaching 1.1m. The rain events between March 15/26th generate the water level annual peaks at all the reaches, from 1.9m to 5.4m (outlet reach). Seven reaches increased the vertical incision around 20/30cm to 80cm, and localised pools were eroded to up 1.7m deep. The outlet part exhibit around 30 to 40cm of sedimentation even with a water level peak of 5.4m. This unusual response could be caused by backwater effect from the Espinho River flood, which Tigre River is a tributary, that trapped sediment in the Tigre River. These results highlight how dynamic intermittent/ephemeral tropical rivers and showed how low-cost UAV High-Resolution DEMs and stage crests are workable and efficient techniques to monitor ungauged intermittent/ephemeral rivers. Simultaneously, narrow the surveys timespan (Covid-19 pandemic hindered most of the monthly planned surveys) is essential to identify which flow events caused erosion and sedimentation and which rain events trigger flow events.
Keywords: Sand-bed rivers; UAV HR-DEMs; Brazilian Drylands; Water Level Stage Crest, riverbed erosion
How to cite: Souza, J., Alexandre, F., and Monteiro, G.: River bed dynamic monitoring on ephemeral/intermittent rivers – sand-bed response on topical drylands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14337, https://doi.org/10.5194/egusphere-egu21-14337, 2021.
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Intermittent and ephemeral rivers, prevalent in dryland areas, have less monitoring data than perennial rivers worldwide. It hinders studies about hydro-geomorphology dynamics on these streams, which is especially complex in rain-fed flow regime on tropical rivers. Irregular rain patterns characterise the tropical drylands, which reverberate in the hydro-geomorphological dynamic. Unmanned Aerial Vehicles (UAV) survey is an efficient and cheap technic to monitor these streams since the dry periods expose the riverbed surface. This research aimed to analyse the hydro-geomorphology dynamic on sandy bed reaches of an intermittent tropical river. Five UAV surveys were realised on eight sandy reaches, from headwater to the outlet, between 2020 January 7 and December 9 in the Tigre River – Brazilian Drylands –, a 30Km ephemeral/intermittent. The UAV photos from all the surveys were co-aligned to create matching DEMs. We compared the DEMs to identify channel morphology changes, calculating differences in the riverbed and riverbank. The DEMs comparison enabled to calculate the erosion and sedimentation volume to each reach. Simultaneously, we installed crest stages gauges to monitor the peak water level between the surveys. Lastly, we used five rain gauges to identify the necessary rain volume that generates flow events. The 2020 annual rain volume was close to the historical average, between 530mm and 700mm, on the pediments, up to 1000mm on highland headwaters. The average potential evapotranspiration is around 1400-1800mm/year, due to the tropical climate. There was an average of 3.4 extreme rainfall daily events (over 50mm/day) during the year and the rainest period was between March 15 to 26th when rained from 134mm to 376mm around the watershed. The surveys between January 18 and March 8 identified insignificant morphology changes on eight reaches. The peak water levels were between no flow to 0.49m; only the outlet reach showed slight erosion and water level reaching 1.1m. The rain events between March 15/26th generate the water level annual peaks at all the reaches, from 1.9m to 5.4m (outlet reach). Seven reaches increased the vertical incision around 20/30cm to 80cm, and localised pools were eroded to up 1.7m deep. The outlet part exhibit around 30 to 40cm of sedimentation even with a water level peak of 5.4m. This unusual response could be caused by backwater effect from the Espinho River flood, which Tigre River is a tributary, that trapped sediment in the Tigre River. These results highlight how dynamic intermittent/ephemeral tropical rivers and showed how low-cost UAV High-Resolution DEMs and stage crests are workable and efficient techniques to monitor ungauged intermittent/ephemeral rivers. Simultaneously, narrow the surveys timespan (Covid-19 pandemic hindered most of the monthly planned surveys) is essential to identify which flow events caused erosion and sedimentation and which rain events trigger flow events.
Keywords: Sand-bed rivers; UAV HR-DEMs; Brazilian Drylands; Water Level Stage Crest, riverbed erosion
How to cite: Souza, J., Alexandre, F., and Monteiro, G.: River bed dynamic monitoring on ephemeral/intermittent rivers – sand-bed response on topical drylands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14337, https://doi.org/10.5194/egusphere-egu21-14337, 2021.
EGU21-7033 | vPICO presentations | GM5.2
Effects of grid scale and resulting initial bed disturbance differences on the evolution of braided riversChangjin Wang and Peng Hu
Physics-based models have been increasingly developed in recent years and applied to simulate the braiding process and evolution of channel units in braided rivers. Braided rivers are the river network system characterized by the staggered distribution of bars and channels. In the numerical calculation, the grid scale affects the behavior process and morphological description of braided rivers. In this paper, a 2D numerical model is used to simulate the evolution of the braided rivers where the transport of load bed sediment plays a dominant role. In the natural scale braided rivers evolution modeling, the difference of the braided rivers' morphological characteristics under different grid scales is discussed, and the influence of different distribution of topographic disturbance caused by grid scale difference on the morphological characteristics of braided rivers is discussed. The study shows that the grid scale does not affect the description of braided rivers evolution process, and braided rivers evolve in the same way regardless of grid scale (within a reasonable range). However, the statistical characteristics of braided rivers are greatly affected by the grid scale. The braiding index increases as the grid scale decreases, but when the grid scale decreases to a certain extent (20m in this paper), the braiding index no longer increases. The number and average height of bars in braided rivers increase with the decrease of grid scale, and the average area of bar near riverbed also increases with the decrease of grid scale, but the average area of bar near water surface does not change with the change of grid scale. In general, the higher the grid resolution is, the more similar the bar morphology in the numerical model is to that in natural rivers. In addition, the different distribution of topographic disturbance caused by the grid scale difference has an influence on the braiding intensity and the bar morphology of the braided rivers, but the influence degree is much smaller than that caused by the grid scale difference.
How to cite: Wang, C. and Hu, P.: Effects of grid scale and resulting initial bed disturbance differences on the evolution of braided rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7033, https://doi.org/10.5194/egusphere-egu21-7033, 2021.
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Physics-based models have been increasingly developed in recent years and applied to simulate the braiding process and evolution of channel units in braided rivers. Braided rivers are the river network system characterized by the staggered distribution of bars and channels. In the numerical calculation, the grid scale affects the behavior process and morphological description of braided rivers. In this paper, a 2D numerical model is used to simulate the evolution of the braided rivers where the transport of load bed sediment plays a dominant role. In the natural scale braided rivers evolution modeling, the difference of the braided rivers' morphological characteristics under different grid scales is discussed, and the influence of different distribution of topographic disturbance caused by grid scale difference on the morphological characteristics of braided rivers is discussed. The study shows that the grid scale does not affect the description of braided rivers evolution process, and braided rivers evolve in the same way regardless of grid scale (within a reasonable range). However, the statistical characteristics of braided rivers are greatly affected by the grid scale. The braiding index increases as the grid scale decreases, but when the grid scale decreases to a certain extent (20m in this paper), the braiding index no longer increases. The number and average height of bars in braided rivers increase with the decrease of grid scale, and the average area of bar near riverbed also increases with the decrease of grid scale, but the average area of bar near water surface does not change with the change of grid scale. In general, the higher the grid resolution is, the more similar the bar morphology in the numerical model is to that in natural rivers. In addition, the different distribution of topographic disturbance caused by the grid scale difference has an influence on the braiding intensity and the bar morphology of the braided rivers, but the influence degree is much smaller than that caused by the grid scale difference.
How to cite: Wang, C. and Hu, P.: Effects of grid scale and resulting initial bed disturbance differences on the evolution of braided rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7033, https://doi.org/10.5194/egusphere-egu21-7033, 2021.
EGU21-4561 | vPICO presentations | GM5.2
Upstream and downstream morphodynamic influence in simulated and real meandering riversHossein Amini, Guido Zolezzi, Federico Monegaglia, Emanuele Olivetti, and Marco Tubino
This study investigates the dependency of meander lateral migration rates on the spatial distribution of channel centerline curvature in both synthetic and real meandering rivers. It employs Machine Learning techniques (hereafter ML) to relate observed local lateral meander migration rates with the local and the upstream/downstream values of the centerline curvature. To achieve this goal, it was primarily essential to identify the feasibility of using ML in the meandering river's morphodynamics. We then determined the ability of ML to predict the excess near bank velocity based a set of input data using different regression techniques (linear and polynomial, Stochastic Gradient Descent, Multi-Layer Perceptron, and Support Vector Machine). We then moved forward to study the upstream-downstream influence on local migration rate. Synthetic meandering river planforms, as obtained through the planform evolution model of Bogoni et al. (2017), which is based on Zolezzi and Seminara (2001) meander flow model, were used as test cases for the calibration and check of the different adopted ML algorithms. The calibrated algorithms were then applied to multi-temporal information on meander planform dynamics obtained through the PyRiS software (Monegaglia et al., 2018), to quantify to which extent the upstream and downstream distribution of meander centerline curvature affects the local meander migration rate in real rivers.
References
1- Zolezzi, G., & Seminara, G. (2001b). Downstream and upstream influence in river meandering. Part 1. General theory and application overdeepening. Journal of Fluid Mechanics, 438(September 2015), 183–211. https://doi.org/10.1017/S002211200100427X
2- Monegaglia, F., Zolezzi, G., Güneralp, I., Henshaw, A. J., & Tubino, M. (2018). Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data. In Environmental Modelling & Software (Vol. 105, pp. 171–186). https://doi.org/10.1016/j.envsoft.2018.03.028
3- Bogoni, M., Putti, M., & Lanzoni, S. (2017). Modeling meander morphodynamics over self-formed heterogeneous floodplains. In Water Resources Research (Vol. 53, Issue 6, pp. 5137–5157). https://doi.org/10.1002/2017wr020726
4- Benozzo, D., Olivetti, E., Avesani, P. (2017). Supervised Estimation of Granger-Based Causality between Time series. In Frontiers in Neuroinformatics.
https://doi.org/10.3389/fninf.2017.00068
5- Sharma A., Kiciman, E. (2020). DoWhy: An End-to-End library for Causal Inference. arXiv preprint arXiv:2011.04216.
https://arxiv.org/abs/2011.04216
How to cite: Amini, H., Zolezzi, G., Monegaglia, F., Olivetti, E., and Tubino, M.: Upstream and downstream morphodynamic influence in simulated and real meandering rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4561, https://doi.org/10.5194/egusphere-egu21-4561, 2021.
This study investigates the dependency of meander lateral migration rates on the spatial distribution of channel centerline curvature in both synthetic and real meandering rivers. It employs Machine Learning techniques (hereafter ML) to relate observed local lateral meander migration rates with the local and the upstream/downstream values of the centerline curvature. To achieve this goal, it was primarily essential to identify the feasibility of using ML in the meandering river's morphodynamics. We then determined the ability of ML to predict the excess near bank velocity based a set of input data using different regression techniques (linear and polynomial, Stochastic Gradient Descent, Multi-Layer Perceptron, and Support Vector Machine). We then moved forward to study the upstream-downstream influence on local migration rate. Synthetic meandering river planforms, as obtained through the planform evolution model of Bogoni et al. (2017), which is based on Zolezzi and Seminara (2001) meander flow model, were used as test cases for the calibration and check of the different adopted ML algorithms. The calibrated algorithms were then applied to multi-temporal information on meander planform dynamics obtained through the PyRiS software (Monegaglia et al., 2018), to quantify to which extent the upstream and downstream distribution of meander centerline curvature affects the local meander migration rate in real rivers.
References
1- Zolezzi, G., & Seminara, G. (2001b). Downstream and upstream influence in river meandering. Part 1. General theory and application overdeepening. Journal of Fluid Mechanics, 438(September 2015), 183–211. https://doi.org/10.1017/S002211200100427X
2- Monegaglia, F., Zolezzi, G., Güneralp, I., Henshaw, A. J., & Tubino, M. (2018). Automated extraction of meandering river morphodynamics from multitemporal remotely sensed data. In Environmental Modelling & Software (Vol. 105, pp. 171–186). https://doi.org/10.1016/j.envsoft.2018.03.028
3- Bogoni, M., Putti, M., & Lanzoni, S. (2017). Modeling meander morphodynamics over self-formed heterogeneous floodplains. In Water Resources Research (Vol. 53, Issue 6, pp. 5137–5157). https://doi.org/10.1002/2017wr020726
4- Benozzo, D., Olivetti, E., Avesani, P. (2017). Supervised Estimation of Granger-Based Causality between Time series. In Frontiers in Neuroinformatics.
https://doi.org/10.3389/fninf.2017.00068
5- Sharma A., Kiciman, E. (2020). DoWhy: An End-to-End library for Causal Inference. arXiv preprint arXiv:2011.04216.
https://arxiv.org/abs/2011.04216
How to cite: Amini, H., Zolezzi, G., Monegaglia, F., Olivetti, E., and Tubino, M.: Upstream and downstream morphodynamic influence in simulated and real meandering rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4561, https://doi.org/10.5194/egusphere-egu21-4561, 2021.
EGU21-8168 | vPICO presentations | GM5.2
Numerical Research of Fujiangsha Waterway Based on a Depth-integrated Hydro-sediment-morphodynamic ModelMengzhe Sun, Peng Hu, and Youwei Li
Fujiangsha waterway is located in the tidal reach of Yangtze River, which is one of the key sections for channel regulation. The channel condition of the waterway is governed by the evolution of the channel bar and point bar. Groins are consequently set on both sides of the channel bar and the left edge of Fujiangsha island. To explore the impact of the regulation works on the evolution of bars and channels, a numerical research is carried out based on a depth-integrated hydro-sediment-morphodynamic model, using the method of nesting large-scale model with local model. The non-negligible impact on the quality and momentum of water flow caused by enormous sediment transport and drastic change of topography, as well as the complex flow condition in both tide and runoff working together, has been taken into account. The simulation successfully reproduces the hydrological process and changes of topography in Fujiangsha waterway. Results show that: 1) there is a silting trend at the head of the channel bar, and the effect of the regulation works in bar protection and sand stabilization is remarkable; 2) The erosion on both sides of the channel bar improves the channel condition, and the hydrodynamic performance of shallow area at the entrance of the south branch has been enhanced; 3) The control on the evolution of point bar is still weak, which will have an adverse effect on channel condition of north branch.
How to cite: Sun, M., Hu, P., and Li, Y.: Numerical Research of Fujiangsha Waterway Based on a Depth-integrated Hydro-sediment-morphodynamic Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8168, https://doi.org/10.5194/egusphere-egu21-8168, 2021.
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Fujiangsha waterway is located in the tidal reach of Yangtze River, which is one of the key sections for channel regulation. The channel condition of the waterway is governed by the evolution of the channel bar and point bar. Groins are consequently set on both sides of the channel bar and the left edge of Fujiangsha island. To explore the impact of the regulation works on the evolution of bars and channels, a numerical research is carried out based on a depth-integrated hydro-sediment-morphodynamic model, using the method of nesting large-scale model with local model. The non-negligible impact on the quality and momentum of water flow caused by enormous sediment transport and drastic change of topography, as well as the complex flow condition in both tide and runoff working together, has been taken into account. The simulation successfully reproduces the hydrological process and changes of topography in Fujiangsha waterway. Results show that: 1) there is a silting trend at the head of the channel bar, and the effect of the regulation works in bar protection and sand stabilization is remarkable; 2) The erosion on both sides of the channel bar improves the channel condition, and the hydrodynamic performance of shallow area at the entrance of the south branch has been enhanced; 3) The control on the evolution of point bar is still weak, which will have an adverse effect on channel condition of north branch.
How to cite: Sun, M., Hu, P., and Li, Y.: Numerical Research of Fujiangsha Waterway Based on a Depth-integrated Hydro-sediment-morphodynamic Model, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8168, https://doi.org/10.5194/egusphere-egu21-8168, 2021.
EGU21-12234 | vPICO presentations | GM5.2
Application of equilibrium theory on alluvial channel-form adjustment in a large river heavily loaded with sedimentHe Qing Huang, Min Zhang, Teng Su, and Guoan Yu
Taking the width/depth ratio of an alluvial channel as an independent variable, a variational analysis of basic flow relationships shows that flow is able to achieve stationary equilibrium by adjusting channel geometry when the condition of maximum flow efficiency (MFE) is satisfied. To examine if this theory of self-adjusting channel morphodynamics can be practically applied to large river systems heavily loaded with sediment, this study examines the degree of correspondence between theoretically determined equilibrium channel geometries and actual measurements along the lower Yellow River. Using the Meyer-Peter and Müller bedload relation modified on the basis of MFE theory and relations of flow continuity and resistance we present a detailed investigation of the potential physical causes and main factors resulting in the correspondence.
How to cite: Huang, H. Q., Zhang, M., Su, T., and Yu, G.: Application of equilibrium theory on alluvial channel-form adjustment in a large river heavily loaded with sediment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12234, https://doi.org/10.5194/egusphere-egu21-12234, 2021.
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Taking the width/depth ratio of an alluvial channel as an independent variable, a variational analysis of basic flow relationships shows that flow is able to achieve stationary equilibrium by adjusting channel geometry when the condition of maximum flow efficiency (MFE) is satisfied. To examine if this theory of self-adjusting channel morphodynamics can be practically applied to large river systems heavily loaded with sediment, this study examines the degree of correspondence between theoretically determined equilibrium channel geometries and actual measurements along the lower Yellow River. Using the Meyer-Peter and Müller bedload relation modified on the basis of MFE theory and relations of flow continuity and resistance we present a detailed investigation of the potential physical causes and main factors resulting in the correspondence.
How to cite: Huang, H. Q., Zhang, M., Su, T., and Yu, G.: Application of equilibrium theory on alluvial channel-form adjustment in a large river heavily loaded with sediment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12234, https://doi.org/10.5194/egusphere-egu21-12234, 2021.
EGU21-10910 | vPICO presentations | GM5.2
River morphology evolution driven by mass movements in tectonic active regions – A negative feedback response of transient landscapeGuo-An Yu, He Qing Huang, and Weipeng Hou
Incised valleys or steep slopes in tectonic active mountain areas are normally in a critical equilibrium state which is highly fragile and prone to deviate under exotic disturbances (e.g., earthquake, heavy precipitation, or even human activities), inducing mass movements (e.g., landslides, avalanche, and/or debris flows). Mass movements have great impacts on fluvial processes and may even reshape valley morphology, hence are powerful drivers to river evolution in those environments. Unfortunately, compared to the mass movements themselves (e.g., occurrence time, volume, dynamics and underlying mechanisms), less attention has been paid to the fluvial processes (in a short/intermediate-term) and the long-term evolution of river morphology corresponding to (and after) those mass movements (especially catastrophic ones). This motivates the current work.
The southeast Tibet, located on the east Qinghai-Tibet Plateau, is one of the most active regions globally in terms of tectonic motion and rates of uplift. Rivers in the lower Yalung Tsangpo basin in this area are investigated to understand the morphodynamics influenced by modern and historical mass movements and examine the feedbacks of fluvial processes to mass movements. River reaches influenced by typical mass movements were chosen for detailed field surveys, including: (1) the upper part of the Yalung Tsangpo Grand Canyon which has been seriously impacted by avalanches and debris flows from tributary gullies originating at glacial mountains of Namcha Barwa and Gyala Peri; (2) the lower reach of the Yigong River covering the Yigong Landslide from the Zhamunong Gully; (3) the lower reach of the Palong River influenced by debris flows from Guxiang and Tianmo gullies; and (4) the upper and middle reaches of the Palong River (extending roughly from Ranwu Lake to the upstream of Guxiang Lake) influenced by glacial processes and other induced mass movements since the last glacial maximum. Remote sensing images before and after the large-scale mass movements in recent decades were also used to track the corresponding river morphology variation.
Due to very high transport rate and volume of sediment incoming, mass movements have caused dramatic channel processes in east Tibet. Some even dammed the river, forming knickpoints and reshaping valley morphology. The morphology of the valleys in this area normally show alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. In recent decades, mass movements (mostly debris flows), occurred more frequently through gullies in the reaches of gorge sections than through gullies along the wide valley sections. Mass movements deviate river morphology and slope from (quasi-)equilibrium to non-equilibrium state, however, with attendant rapid sediment incoming, valley bottom siltation and erosion benchmark rising, it triggers a negative feedback which drives the river morphology to a new round of development towards equilibrium.
How to cite: Yu, G.-A., Huang, H. Q., and Hou, W.: River morphology evolution driven by mass movements in tectonic active regions – A negative feedback response of transient landscape, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10910, https://doi.org/10.5194/egusphere-egu21-10910, 2021.
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Incised valleys or steep slopes in tectonic active mountain areas are normally in a critical equilibrium state which is highly fragile and prone to deviate under exotic disturbances (e.g., earthquake, heavy precipitation, or even human activities), inducing mass movements (e.g., landslides, avalanche, and/or debris flows). Mass movements have great impacts on fluvial processes and may even reshape valley morphology, hence are powerful drivers to river evolution in those environments. Unfortunately, compared to the mass movements themselves (e.g., occurrence time, volume, dynamics and underlying mechanisms), less attention has been paid to the fluvial processes (in a short/intermediate-term) and the long-term evolution of river morphology corresponding to (and after) those mass movements (especially catastrophic ones). This motivates the current work.
The southeast Tibet, located on the east Qinghai-Tibet Plateau, is one of the most active regions globally in terms of tectonic motion and rates of uplift. Rivers in the lower Yalung Tsangpo basin in this area are investigated to understand the morphodynamics influenced by modern and historical mass movements and examine the feedbacks of fluvial processes to mass movements. River reaches influenced by typical mass movements were chosen for detailed field surveys, including: (1) the upper part of the Yalung Tsangpo Grand Canyon which has been seriously impacted by avalanches and debris flows from tributary gullies originating at glacial mountains of Namcha Barwa and Gyala Peri; (2) the lower reach of the Yigong River covering the Yigong Landslide from the Zhamunong Gully; (3) the lower reach of the Palong River influenced by debris flows from Guxiang and Tianmo gullies; and (4) the upper and middle reaches of the Palong River (extending roughly from Ranwu Lake to the upstream of Guxiang Lake) influenced by glacial processes and other induced mass movements since the last glacial maximum. Remote sensing images before and after the large-scale mass movements in recent decades were also used to track the corresponding river morphology variation.
Due to very high transport rate and volume of sediment incoming, mass movements have caused dramatic channel processes in east Tibet. Some even dammed the river, forming knickpoints and reshaping valley morphology. The morphology of the valleys in this area normally show alternating sections of gorges and wide valleys, with a staircase-like longitudinal profile. The gorge sections exhibit single and deeply incised channels with a high-gradient channel bed and terraces. In contrast, the wide valley sections consist of lakes, braided or anabranching channels, gentle bed gradients, and thick alluvial deposits. In recent decades, mass movements (mostly debris flows), occurred more frequently through gullies in the reaches of gorge sections than through gullies along the wide valley sections. Mass movements deviate river morphology and slope from (quasi-)equilibrium to non-equilibrium state, however, with attendant rapid sediment incoming, valley bottom siltation and erosion benchmark rising, it triggers a negative feedback which drives the river morphology to a new round of development towards equilibrium.
How to cite: Yu, G.-A., Huang, H. Q., and Hou, W.: River morphology evolution driven by mass movements in tectonic active regions – A negative feedback response of transient landscape, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10910, https://doi.org/10.5194/egusphere-egu21-10910, 2021.
EGU21-9137 | vPICO presentations | GM5.2
Compiling and Analysing Bedrock River Data Across the USA to Unpick Bedrock River GeomorphologyJames Buckley, Rebecca Hodge, and Louise Slater
Active incision of bedrock rivers exerts a vital control on landscape evolution in upland areas. Previous research found that bedrock rivers were typically steeper and sometimes narrower than alluvial rivers. However, most of the literature on partially-exposed bedrock rivers has employed small samples mostly from mountainous regions, so their geomorphological properties remain poorly understood. In contrast with the existing literature, a large-sample analysis of bedrock river channel properties would allow the controls on bedrock river width and slope to be unpicked and reveal whether or not the existing literature is biased towards pristine, mountainous bedrock rivers. Overall, such an analysis could improve the reliability of upland landscape evolution models.
Here we present an analysis of 1,924 river sites from the EPA National Rivers and Streams Assessment to assess the geomorphological differences between bedrock and alluvial rivers. The influences of lithology and uplift on bedrock channel properties are examined using external datasets. We find bedrock rivers to be significantly steeper and wider than alluvial rivers. Sedimentary bedrock rivers were seen to be significantly wider than igneous/ metamorphic bedrock rivers, consistent with findings from Ferguson et al. (2017). We estimated shear stress and critical shear stress for each river site and assessed correlation with bedrock exposure. We found that exposed bedrock could not always be explained by local sediment transport exceeding local sediment supply, indicating that bedrock exposure may be controlled by other factors in some bedrock rivers. Currently, uplift data are being compiled for further analysis.
How to cite: Buckley, J., Hodge, R., and Slater, L.: Compiling and Analysing Bedrock River Data Across the USA to Unpick Bedrock River Geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9137, https://doi.org/10.5194/egusphere-egu21-9137, 2021.
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Active incision of bedrock rivers exerts a vital control on landscape evolution in upland areas. Previous research found that bedrock rivers were typically steeper and sometimes narrower than alluvial rivers. However, most of the literature on partially-exposed bedrock rivers has employed small samples mostly from mountainous regions, so their geomorphological properties remain poorly understood. In contrast with the existing literature, a large-sample analysis of bedrock river channel properties would allow the controls on bedrock river width and slope to be unpicked and reveal whether or not the existing literature is biased towards pristine, mountainous bedrock rivers. Overall, such an analysis could improve the reliability of upland landscape evolution models.
Here we present an analysis of 1,924 river sites from the EPA National Rivers and Streams Assessment to assess the geomorphological differences between bedrock and alluvial rivers. The influences of lithology and uplift on bedrock channel properties are examined using external datasets. We find bedrock rivers to be significantly steeper and wider than alluvial rivers. Sedimentary bedrock rivers were seen to be significantly wider than igneous/ metamorphic bedrock rivers, consistent with findings from Ferguson et al. (2017). We estimated shear stress and critical shear stress for each river site and assessed correlation with bedrock exposure. We found that exposed bedrock could not always be explained by local sediment transport exceeding local sediment supply, indicating that bedrock exposure may be controlled by other factors in some bedrock rivers. Currently, uplift data are being compiled for further analysis.
How to cite: Buckley, J., Hodge, R., and Slater, L.: Compiling and Analysing Bedrock River Data Across the USA to Unpick Bedrock River Geomorphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9137, https://doi.org/10.5194/egusphere-egu21-9137, 2021.
EGU21-6784 | vPICO presentations | GM5.2
Effects of lithology on bedrock channel occurrence: an examination from the Seogang River in South KoreaHui Chen and Jongmin Byun
Bedrock river is rock-bound, its bed and banks are composed mainly of in-place bedrock. Bedrock channel reaches, commonly short and intermittent, often occur where transport capacity exceeds bedload sediment flux. Despite the abundant research on the typical patterns of alluvial channel reaches, the distribution of bedrock channels has not been well studied. Rock type may affect the occurrence of bedrock channels because the strength, joint density, and erosion process of bedrock vary depending on the rock type. Previous studies have viewed the bedrock channel occurrence in the aspect of the excessive sediment transport capacity, but the influence of lithology has not been considered in the literature. To understand the influence of lithology on bedrock channel occurrence in a drainage basin-scale, we investigated the distribution of bedrock channels in relation to varying lithology and unit stream power along the Seogang River in South Korea. We used satellite images with high resolution for the identification of bedrock channel reaches and then verified them through field surveys. Geological maps and 1 arc-second SRTM DEMs were used to analyze lithological effects and calculate unit stream power. As a result of the analysis, we identified 94 bedrock channels in the studied river, varying depending on lithologies. The frequency of bedrock channels in granitic gneiss areas (0.73/km) is much higher than those in the other rock type areas (granite areas, 0.57/km; limestone areas, 0.16/km). In the more frequent granitic gneiss areas, the bedrock channels are steepened (average channel slope: 0.0074 m/m) and narrow (average channel width: 65 m) and mainly reside within steepened and narrow (average valley width: 123 m) rock-bound valleys so that their occurrence is mainly associated with high unit stream power. In contrast, the bedrock channels over the other lithologies are wider (89 m) and lower-gradient (0.0056 m/m) and occur along flat and broad valleys (391 m). Consequently, the bedrock channels in the studied river were divided into two types: confined and unconfined bedrock channels. The confined bedrock channels are within the steepened and narrow valleys composed of resistant granitic gneiss and show the evidence for recent bedrock incision processes. However, the unconfined bedrock channels are mainly within the broad and flat valleys of weak saprolites and limestone with high joint density have lower unit stream power and don't show any marker for bedrock incision. In conclusion, high-relief landscape mainly composed of more resistant rocks generates steep and narrow valleys, which leads to the formation of continuous and actively incising bedrock channels. However, low-relief landscape underlain by non-resistant rocks shows wider and lower-gradient channels, with intermittent bedrock channels due to locally more resistant rock bodies.
How to cite: Chen, H. and Byun, J.: Effects of lithology on bedrock channel occurrence: an examination from the Seogang River in South Korea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6784, https://doi.org/10.5194/egusphere-egu21-6784, 2021.
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Bedrock river is rock-bound, its bed and banks are composed mainly of in-place bedrock. Bedrock channel reaches, commonly short and intermittent, often occur where transport capacity exceeds bedload sediment flux. Despite the abundant research on the typical patterns of alluvial channel reaches, the distribution of bedrock channels has not been well studied. Rock type may affect the occurrence of bedrock channels because the strength, joint density, and erosion process of bedrock vary depending on the rock type. Previous studies have viewed the bedrock channel occurrence in the aspect of the excessive sediment transport capacity, but the influence of lithology has not been considered in the literature. To understand the influence of lithology on bedrock channel occurrence in a drainage basin-scale, we investigated the distribution of bedrock channels in relation to varying lithology and unit stream power along the Seogang River in South Korea. We used satellite images with high resolution for the identification of bedrock channel reaches and then verified them through field surveys. Geological maps and 1 arc-second SRTM DEMs were used to analyze lithological effects and calculate unit stream power. As a result of the analysis, we identified 94 bedrock channels in the studied river, varying depending on lithologies. The frequency of bedrock channels in granitic gneiss areas (0.73/km) is much higher than those in the other rock type areas (granite areas, 0.57/km; limestone areas, 0.16/km). In the more frequent granitic gneiss areas, the bedrock channels are steepened (average channel slope: 0.0074 m/m) and narrow (average channel width: 65 m) and mainly reside within steepened and narrow (average valley width: 123 m) rock-bound valleys so that their occurrence is mainly associated with high unit stream power. In contrast, the bedrock channels over the other lithologies are wider (89 m) and lower-gradient (0.0056 m/m) and occur along flat and broad valleys (391 m). Consequently, the bedrock channels in the studied river were divided into two types: confined and unconfined bedrock channels. The confined bedrock channels are within the steepened and narrow valleys composed of resistant granitic gneiss and show the evidence for recent bedrock incision processes. However, the unconfined bedrock channels are mainly within the broad and flat valleys of weak saprolites and limestone with high joint density have lower unit stream power and don't show any marker for bedrock incision. In conclusion, high-relief landscape mainly composed of more resistant rocks generates steep and narrow valleys, which leads to the formation of continuous and actively incising bedrock channels. However, low-relief landscape underlain by non-resistant rocks shows wider and lower-gradient channels, with intermittent bedrock channels due to locally more resistant rock bodies.
How to cite: Chen, H. and Byun, J.: Effects of lithology on bedrock channel occurrence: an examination from the Seogang River in South Korea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6784, https://doi.org/10.5194/egusphere-egu21-6784, 2021.
EGU21-14546 | vPICO presentations | GM5.2 | Highlight
Quantifying the erosion of the world’s largest impact crater using cosmogenic nuclides: the Vredefort Dome, South Africa.Rivoningo Khosa, Stephen Tooth, Jan Kramers, Vela Mbele, Lee Corbett, and Paul Bierman
The world’s largest meteorite impact crater, the Vredefort Dome, has been the subject of extensive studies relating to its age, geology and geomorphology. However, there are no studies pertaining to the rate at which the rocks in the crater remnant are eroding, which can provide insight into the development of the landform over time. This study used the cosmogenic nuclides 10Be and 26Al, extracted from purified quartz samples, to investigate erosion rates along the Vaal River as it traverses the impact crater. The Vaal River flows in mixed bedrock-alluvial terrain through the dome, crossing two different bedrock lithologies. The river is multi-channelled (anabranching) atop the granitoids exposed in the core of the dome, then downstream flows as a single channel through a narrow canyon cut into the quartzites that form the rim of the dome. We collected 14 samples from the two rock types to assess lithologic controls on erosion rate and determine landscape erosion history. Results from the analysis of both isotopes were in close agreement; here, we report outcrop erosion rates based on the 10Be. The average 10Be-determined erosion rates (± 1 SD) along the active river channel for the quartzite (n = 4) and granitoid (n = 6) regions are 1.90 ± 0.12 and 2.19 ± 0.14 m/Ma respectively. Additional samples from older, now elevated (>5 m) strath terraces developed atop quartzite (n = 4) indicate slightly lower average apparent erosion rates of 1.65 (± 0.09) m/Ma. The data demonstrate that the erosion rates along the active river channel are similar between the two lithologies despite differences in rock hardness. The resistant, slowing eroding quartzites serve as the local base level for the river upstream, promoting the development of anabranching, which disperses bedrock erosion over a wider area of the crater. We infer that both bedrock hardness and channel characteristics are important controls on erosion rates along the river. Collectively, the dataset further illustrates the low bedrock erosion rates that prevail across large areas of the southern African interior.
How to cite: Khosa, R., Tooth, S., Kramers, J., Mbele, V., Corbett, L., and Bierman, P.: Quantifying the erosion of the world’s largest impact crater using cosmogenic nuclides: the Vredefort Dome, South Africa., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14546, https://doi.org/10.5194/egusphere-egu21-14546, 2021.
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The world’s largest meteorite impact crater, the Vredefort Dome, has been the subject of extensive studies relating to its age, geology and geomorphology. However, there are no studies pertaining to the rate at which the rocks in the crater remnant are eroding, which can provide insight into the development of the landform over time. This study used the cosmogenic nuclides 10Be and 26Al, extracted from purified quartz samples, to investigate erosion rates along the Vaal River as it traverses the impact crater. The Vaal River flows in mixed bedrock-alluvial terrain through the dome, crossing two different bedrock lithologies. The river is multi-channelled (anabranching) atop the granitoids exposed in the core of the dome, then downstream flows as a single channel through a narrow canyon cut into the quartzites that form the rim of the dome. We collected 14 samples from the two rock types to assess lithologic controls on erosion rate and determine landscape erosion history. Results from the analysis of both isotopes were in close agreement; here, we report outcrop erosion rates based on the 10Be. The average 10Be-determined erosion rates (± 1 SD) along the active river channel for the quartzite (n = 4) and granitoid (n = 6) regions are 1.90 ± 0.12 and 2.19 ± 0.14 m/Ma respectively. Additional samples from older, now elevated (>5 m) strath terraces developed atop quartzite (n = 4) indicate slightly lower average apparent erosion rates of 1.65 (± 0.09) m/Ma. The data demonstrate that the erosion rates along the active river channel are similar between the two lithologies despite differences in rock hardness. The resistant, slowing eroding quartzites serve as the local base level for the river upstream, promoting the development of anabranching, which disperses bedrock erosion over a wider area of the crater. We infer that both bedrock hardness and channel characteristics are important controls on erosion rates along the river. Collectively, the dataset further illustrates the low bedrock erosion rates that prevail across large areas of the southern African interior.
How to cite: Khosa, R., Tooth, S., Kramers, J., Mbele, V., Corbett, L., and Bierman, P.: Quantifying the erosion of the world’s largest impact crater using cosmogenic nuclides: the Vredefort Dome, South Africa., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14546, https://doi.org/10.5194/egusphere-egu21-14546, 2021.
EGU21-3304 | vPICO presentations | GM5.2
A mechanistic model for bedrock undercut from saltating bedload particle impactsTingan Li, Jeremy Venditti, and Leonard Sklar
Bedrock walls can be undercut by saltating bedload particle impacts that are deflected by alluvial cover. Continued undercutting of the lower wall creates an imbalance on the wall and may cause the upper part to collapse and to widen the whole channel. Compared with vertical erosion rates, less is known about lateral erosion (undercutting) rates that are thought to dominate when river beds are alluviated. Here, we derive an analytical model for lateral erosion by saltating bedload particle impacts. The analytical model is a simplification of the Li et al. (2020) numerical model of the same process. The analytical model predicts a nonlinear dependence of lateral erosion rate on sediment supply, shear stress and grain size, revealing the same behaviour observed in the numerical model, but without tracking particle movements through time and space. The analytical model considers both uniformly distributed cover and patchy partial cover that is implemented with a fully alluviated patch along one bank and a bare bedrock along the other. The model predicts that lateral erosion rate peaks when the bed is ~70% covered for uniformly distributed alluvium and when the bed is fully covered for patchy alluvium. Vertical erosion dominates over lateral erosion for ~75% and >90% of sediment supply and transport conditions for uniformly distributed cover and patchy cover, respectively. We use the model to derive a phase diagram of channel responses (steepening, flattening, narrowing, widening) for various combinations of transport stage and relative sediment supply. Application of our model to Boulder Creek, CA captures the observed channel widening in response to increased sediment supply and steepening in response to larger grain size.
How to cite: Li, T., Venditti, J., and Sklar, L.: A mechanistic model for bedrock undercut from saltating bedload particle impacts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3304, https://doi.org/10.5194/egusphere-egu21-3304, 2021.
Bedrock walls can be undercut by saltating bedload particle impacts that are deflected by alluvial cover. Continued undercutting of the lower wall creates an imbalance on the wall and may cause the upper part to collapse and to widen the whole channel. Compared with vertical erosion rates, less is known about lateral erosion (undercutting) rates that are thought to dominate when river beds are alluviated. Here, we derive an analytical model for lateral erosion by saltating bedload particle impacts. The analytical model is a simplification of the Li et al. (2020) numerical model of the same process. The analytical model predicts a nonlinear dependence of lateral erosion rate on sediment supply, shear stress and grain size, revealing the same behaviour observed in the numerical model, but without tracking particle movements through time and space. The analytical model considers both uniformly distributed cover and patchy partial cover that is implemented with a fully alluviated patch along one bank and a bare bedrock along the other. The model predicts that lateral erosion rate peaks when the bed is ~70% covered for uniformly distributed alluvium and when the bed is fully covered for patchy alluvium. Vertical erosion dominates over lateral erosion for ~75% and >90% of sediment supply and transport conditions for uniformly distributed cover and patchy cover, respectively. We use the model to derive a phase diagram of channel responses (steepening, flattening, narrowing, widening) for various combinations of transport stage and relative sediment supply. Application of our model to Boulder Creek, CA captures the observed channel widening in response to increased sediment supply and steepening in response to larger grain size.
How to cite: Li, T., Venditti, J., and Sklar, L.: A mechanistic model for bedrock undercut from saltating bedload particle impacts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3304, https://doi.org/10.5194/egusphere-egu21-3304, 2021.
EGU21-14033 * | vPICO presentations | GM5.2 | Highlight
Do megafloods reset mountain valleys?Susannah Morey, Katharine Huntington, David Montgomery, Michael Turzewski, and Mahathi Mangipudi
Quaternary megafloods (106 m3/s) sourced from valley blocking glaciers on the Tibetan Plateau have long been implicated in the evolution of Yarlung-Tsangpo Gorge on the Yarlung-Siang River. However, past estimates of megaflood erosion in this region have relied on back of the envelope estimates of peak discharge and shear stress. This makes it difficult to fully understand how megafloods shape the landscape. Here, we use 2D numerical simulations of megaflood hydraulics over 3D topography to examine the legacy of these massive floods on this confined, sinuous mountain river. First, to assess erosional potential in the Gorge, we calculate flood power and compare it to measurements of annual stream power. We find that the simulated megaflood produces peak flood power up to three orders of magnitude higher than the stream power of the annual river. Compared to stream power, flood power in the Gorge is disproportionately higher than it is downstream of the Gorge. Additionally, in the Gorge, a larger proportion of the inundated valley experiences high flood power and shear stress for long periods of time (5-10 hrs) compared to the valley downstream of the Gorge. These results support previous hypotheses that megafloods can erode more material (both alluvium and bedrock) than the annual monsoon—potentially enough to “reset” the mountain valley by removing most of the sediment and fractured bedrock in the system. However, we hypothesize that this erosional effect is felt primarily in the Gorge region. In contrast to the erosive power in the Gorge, there is an order of magnitude decrease in average peak flood power downstream of the Gorge. We hypothesize that megafloods are predominantly depositional in this downstream domain. Here, we observe few locations that experience sustained (>5 hrs) high (>10 kPa) shear stress and those locations are often isolated and vary through time. At locations that do experience these higher shear stresses, megafloods could move and deposit large (>3 m) boulders, which subsequent annual flows or smaller historical outburst floods would be incapable of moving. These large boulders could then armor the bed and prevent erosion, which could have lasting consequences for the modern river. Most of the shear stress and flood power of the simulated megaflood outside of the modern channel boundaries are much lower, capable of moving gravel to sand sized sediment at most. This is particularly true where we observe significant amounts (>10 km) of megaflood backflow up tributaries. Instead of resetting the system, we predict our megaflood will overwhelm this downstream flood domain with the deposition of coarse- and fine-grained sediment. For the Yarlung-Siang River to incise into the bedrock in a post-megaflood landscape, it must first make its way through these megaflood deposits. Together, our results suggest that the legacy of a megaflood in the region is both erosional and depositional. We predict wide-spread megaflood erosion in the Gorge, potentially enough to reset the system, but would expect exceptional deposition downstream of it, possibly enough to overwhelm this downstream domain.
How to cite: Morey, S., Huntington, K., Montgomery, D., Turzewski, M., and Mangipudi, M.: Do megafloods reset mountain valleys?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14033, https://doi.org/10.5194/egusphere-egu21-14033, 2021.
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Quaternary megafloods (106 m3/s) sourced from valley blocking glaciers on the Tibetan Plateau have long been implicated in the evolution of Yarlung-Tsangpo Gorge on the Yarlung-Siang River. However, past estimates of megaflood erosion in this region have relied on back of the envelope estimates of peak discharge and shear stress. This makes it difficult to fully understand how megafloods shape the landscape. Here, we use 2D numerical simulations of megaflood hydraulics over 3D topography to examine the legacy of these massive floods on this confined, sinuous mountain river. First, to assess erosional potential in the Gorge, we calculate flood power and compare it to measurements of annual stream power. We find that the simulated megaflood produces peak flood power up to three orders of magnitude higher than the stream power of the annual river. Compared to stream power, flood power in the Gorge is disproportionately higher than it is downstream of the Gorge. Additionally, in the Gorge, a larger proportion of the inundated valley experiences high flood power and shear stress for long periods of time (5-10 hrs) compared to the valley downstream of the Gorge. These results support previous hypotheses that megafloods can erode more material (both alluvium and bedrock) than the annual monsoon—potentially enough to “reset” the mountain valley by removing most of the sediment and fractured bedrock in the system. However, we hypothesize that this erosional effect is felt primarily in the Gorge region. In contrast to the erosive power in the Gorge, there is an order of magnitude decrease in average peak flood power downstream of the Gorge. We hypothesize that megafloods are predominantly depositional in this downstream domain. Here, we observe few locations that experience sustained (>5 hrs) high (>10 kPa) shear stress and those locations are often isolated and vary through time. At locations that do experience these higher shear stresses, megafloods could move and deposit large (>3 m) boulders, which subsequent annual flows or smaller historical outburst floods would be incapable of moving. These large boulders could then armor the bed and prevent erosion, which could have lasting consequences for the modern river. Most of the shear stress and flood power of the simulated megaflood outside of the modern channel boundaries are much lower, capable of moving gravel to sand sized sediment at most. This is particularly true where we observe significant amounts (>10 km) of megaflood backflow up tributaries. Instead of resetting the system, we predict our megaflood will overwhelm this downstream flood domain with the deposition of coarse- and fine-grained sediment. For the Yarlung-Siang River to incise into the bedrock in a post-megaflood landscape, it must first make its way through these megaflood deposits. Together, our results suggest that the legacy of a megaflood in the region is both erosional and depositional. We predict wide-spread megaflood erosion in the Gorge, potentially enough to reset the system, but would expect exceptional deposition downstream of it, possibly enough to overwhelm this downstream domain.
How to cite: Morey, S., Huntington, K., Montgomery, D., Turzewski, M., and Mangipudi, M.: Do megafloods reset mountain valleys?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14033, https://doi.org/10.5194/egusphere-egu21-14033, 2021.
EGU21-5815 | vPICO presentations | GM5.2 | Highlight
Decadal sediment dynamics of a perturbed fluvial system: the case of the man-made Marecchia River canyon, Northern ApenninesManel Llena, Tommaso Simonelli, and Francesco Brardinoni
River canyons are transient geomorphic systems shaped by river incision into bedrock and coupled by instability of the adjacent valley walls. Investigating the evolution of river canyons is typically challenging due to the geologic time scales involved. In this context, the Marecchia River, which hosts in its intermediate portion a 6-km canyon, developed since the early 1950’s following intense gravel mining, may be instructive. Indeed, this setting offers the opportunity to: (i) document canyon development through highly erodible pelitic rocks; and (ii) evaluate relevant upstream and downstream effects on fluvial morphodynamics. To these ends, we subdivide the 50-km stretch of the Marecchia River main stem into 22 homogeneous reaches and evaluate decadal geomorphic changes through analysis of LiDAR-derived digital elevation models (i.e., 2009 and 2019) in conjunction with planimetric changes of active channel width delineated on orthophoto-mosaics (i.e., 2009, 2012, 2014, 2017, 2019). The estimation of patterns and rates of fluvial erosion into bedrock and its geomorphic effects are essential for understanding landscape evolution and for applying sustainable sediment management plans.
In terms of volumetric changes, the entire river stretch recorded a decadal degradation of 2,516,150 m3 (57%) and 1,884,700 m3 of aggradation (43%), with a corresponding net volume loss of -631,450 m3. Highest specific volumes of aggradation were observed in a homogeneous reach located in the lower part of the study segment (0.5 m3/m2), while highest values of degradation were observed in the upper reach of the canyon (-2.3 m3/m2). During the 2009-2019 period, knickpoint headward migration within the canyon has progressed for approximately 500 m, producing an average bedrock incision of about 10 m. As documented by area and volume changes, both rates of fluvial incision and canyon widening, as modulated by landslide activity and valley wall collapses, are highest in proximity of the main knickpoint and tend to decrease progressively downstream. By March 2019, when the second LiDAR survey was conducted, the main knickpoint had reached the foundations of a major check dam, which eventually collapsed two months later. Upstream of the canyon, channel reaches displayed narrowing dynamics with an alternation of degradation and aggradation processes. In terms of total volumetric changes, these reaches presented an indirect correlation with confinement, with the most confined reaches acting as sediment transfer zones. In contrast, the segment downstream of the canyon displayed widening dynamics (+ 11 m on average) together with an increase of aggradation processes. Due to the pelitic nature of the hosting bedrock, despite the high geomorphic change observed, most of the material supplied by the canyon walls gets transported in suspension, contributing very little to the estimated budget of the Marecchia River's distalmost reaches. In this way, we argue that most part of the aggradation observed in this segment was originated upstream, bypassing the canyon.
How to cite: Llena, M., Simonelli, T., and Brardinoni, F.: Decadal sediment dynamics of a perturbed fluvial system: the case of the man-made Marecchia River canyon, Northern Apennines , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5815, https://doi.org/10.5194/egusphere-egu21-5815, 2021.
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River canyons are transient geomorphic systems shaped by river incision into bedrock and coupled by instability of the adjacent valley walls. Investigating the evolution of river canyons is typically challenging due to the geologic time scales involved. In this context, the Marecchia River, which hosts in its intermediate portion a 6-km canyon, developed since the early 1950’s following intense gravel mining, may be instructive. Indeed, this setting offers the opportunity to: (i) document canyon development through highly erodible pelitic rocks; and (ii) evaluate relevant upstream and downstream effects on fluvial morphodynamics. To these ends, we subdivide the 50-km stretch of the Marecchia River main stem into 22 homogeneous reaches and evaluate decadal geomorphic changes through analysis of LiDAR-derived digital elevation models (i.e., 2009 and 2019) in conjunction with planimetric changes of active channel width delineated on orthophoto-mosaics (i.e., 2009, 2012, 2014, 2017, 2019). The estimation of patterns and rates of fluvial erosion into bedrock and its geomorphic effects are essential for understanding landscape evolution and for applying sustainable sediment management plans.
In terms of volumetric changes, the entire river stretch recorded a decadal degradation of 2,516,150 m3 (57%) and 1,884,700 m3 of aggradation (43%), with a corresponding net volume loss of -631,450 m3. Highest specific volumes of aggradation were observed in a homogeneous reach located in the lower part of the study segment (0.5 m3/m2), while highest values of degradation were observed in the upper reach of the canyon (-2.3 m3/m2). During the 2009-2019 period, knickpoint headward migration within the canyon has progressed for approximately 500 m, producing an average bedrock incision of about 10 m. As documented by area and volume changes, both rates of fluvial incision and canyon widening, as modulated by landslide activity and valley wall collapses, are highest in proximity of the main knickpoint and tend to decrease progressively downstream. By March 2019, when the second LiDAR survey was conducted, the main knickpoint had reached the foundations of a major check dam, which eventually collapsed two months later. Upstream of the canyon, channel reaches displayed narrowing dynamics with an alternation of degradation and aggradation processes. In terms of total volumetric changes, these reaches presented an indirect correlation with confinement, with the most confined reaches acting as sediment transfer zones. In contrast, the segment downstream of the canyon displayed widening dynamics (+ 11 m on average) together with an increase of aggradation processes. Due to the pelitic nature of the hosting bedrock, despite the high geomorphic change observed, most of the material supplied by the canyon walls gets transported in suspension, contributing very little to the estimated budget of the Marecchia River's distalmost reaches. In this way, we argue that most part of the aggradation observed in this segment was originated upstream, bypassing the canyon.
How to cite: Llena, M., Simonelli, T., and Brardinoni, F.: Decadal sediment dynamics of a perturbed fluvial system: the case of the man-made Marecchia River canyon, Northern Apennines , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5815, https://doi.org/10.5194/egusphere-egu21-5815, 2021.
EGU21-10160 | vPICO presentations | GM5.2
Effects of episodic sediment supply on experimental step-pool channel morphology, bedload transport and channel stabilityJiamei Wang, Marwan A. Hassan, Matteo Saletti, Xingyu Chen, Xudong Fu, Hongwei Zhou, and Xingguo Yang
Steep step-pool streams are often coupled to adjacent hillslope, directly receiving episodic sediment supply from mass movement processes such as landslides and debris flows. The response of step-pool channels to the variations in sediment supply remains largely unexplored. We conducted flume experiments with a poorly sorted grain-size distribution in an 8%-steep, 5-m long flume with variable width at the University of British Columbia, to study the effects of episodic sediment supply on channel evolution. After a conditioning phase with no feed, the channel was subjected to sediment pulses of different magnitude and frequency under constant flow discharge. High-resolution data of hydraulics, bedload transport, bed surface grain size, and channel morphology were collected every 10-20 minutes and an additional time at the end of each pulse.
In response to sediment pulses, we recorded an increase in bedload transport rates, channel aggradation, bed surface fining, and continuous step formation and collapse. In between pulses, bedload rates dropped by several orders of magnitude, net erosion occurred, the bed surface gradually coarsened, and steps became more stable. The small-magnitude high-frequency pulses caused smaller but more frequent spikes in bedload transport, bed surface evolution, and thus step stability. Instead, the large-magnitude low-frequency pulses cause larger changes but provided a longer time for the channel to recover. This suggests that in step-pool channels pulse magnitude is a key control on channel rearrangement, while pulse frequency controls how fast and strong the recovery is.
The frequency and stability of steps varied as a function of local channel width, showing that channel geometry is a primary control on step formation and stability even under episodic sediment supply conditions. Instead, the effect of sediment pulses is less important because the total number and average survival time of steps were similar among runs with different pulses. The critical Shields stress decreased following sediment pulses, then increased immediately after, and fluctuated until the next pulse. The variations in sediment supply caused cycles in bedload transport rate, surface and bedload texture, thus controlling the variability in the threshold for motion.
Our results indicate that episodic sediment supply is a primary control on the evolution of step-pool channels, with sediment feed magnitude affecting mostly morphological changes, and sediment feed frequency controlling channel stability.
How to cite: Wang, J., Hassan, M. A., Saletti, M., Chen, X., Fu, X., Zhou, H., and Yang, X.: Effects of episodic sediment supply on experimental step-pool channel morphology, bedload transport and channel stability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10160, https://doi.org/10.5194/egusphere-egu21-10160, 2021.
Steep step-pool streams are often coupled to adjacent hillslope, directly receiving episodic sediment supply from mass movement processes such as landslides and debris flows. The response of step-pool channels to the variations in sediment supply remains largely unexplored. We conducted flume experiments with a poorly sorted grain-size distribution in an 8%-steep, 5-m long flume with variable width at the University of British Columbia, to study the effects of episodic sediment supply on channel evolution. After a conditioning phase with no feed, the channel was subjected to sediment pulses of different magnitude and frequency under constant flow discharge. High-resolution data of hydraulics, bedload transport, bed surface grain size, and channel morphology were collected every 10-20 minutes and an additional time at the end of each pulse.
In response to sediment pulses, we recorded an increase in bedload transport rates, channel aggradation, bed surface fining, and continuous step formation and collapse. In between pulses, bedload rates dropped by several orders of magnitude, net erosion occurred, the bed surface gradually coarsened, and steps became more stable. The small-magnitude high-frequency pulses caused smaller but more frequent spikes in bedload transport, bed surface evolution, and thus step stability. Instead, the large-magnitude low-frequency pulses cause larger changes but provided a longer time for the channel to recover. This suggests that in step-pool channels pulse magnitude is a key control on channel rearrangement, while pulse frequency controls how fast and strong the recovery is.
The frequency and stability of steps varied as a function of local channel width, showing that channel geometry is a primary control on step formation and stability even under episodic sediment supply conditions. Instead, the effect of sediment pulses is less important because the total number and average survival time of steps were similar among runs with different pulses. The critical Shields stress decreased following sediment pulses, then increased immediately after, and fluctuated until the next pulse. The variations in sediment supply caused cycles in bedload transport rate, surface and bedload texture, thus controlling the variability in the threshold for motion.
Our results indicate that episodic sediment supply is a primary control on the evolution of step-pool channels, with sediment feed magnitude affecting mostly morphological changes, and sediment feed frequency controlling channel stability.
How to cite: Wang, J., Hassan, M. A., Saletti, M., Chen, X., Fu, X., Zhou, H., and Yang, X.: Effects of episodic sediment supply on experimental step-pool channel morphology, bedload transport and channel stability, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10160, https://doi.org/10.5194/egusphere-egu21-10160, 2021.
EGU21-10291 | vPICO presentations | GM5.2
Upscaling sediment-flux-dependent fluvial bedrock incision to long timescalesJens Turowski
Fluvial bedrock incision is driven by the impact of moving bedload particles. Mechanistic, sediment-flux-dependent incision models have been proposed, but the stream power incision model (SPIM) is frequently used to model landscape evolution over large spatial and temporal scales. This disconnect between the mechanistic understanding of fluvial bedrock incision on the process scale, and the way it is modelled on long time scales presents one of the current challenges in quantitative geomorphology. Here, a mechanistic model of fluvial bedrock incision that is rooted in current process understanding is explicitly upscaled to long time scales by integrating over the distribution of discharge. The model predicts a channel long profile form equivalent to the one yielded by the SPIM, but explicitly resolves the effects of channel width, cross-sectional shape, bedrock erodibility and discharge variability. The channel long profile chiefly depends on the mechanics of bedload transport, rather than bedrock incision. In addition to the imposed boundary conditions specifying the upstream supply of water and sediment, and the incision rate, the model includes four free parameters, describing the at-a-station hydraulic geometry of channel width, the dependence of bedload transport capacity on channel width, the threshold discharge of bedload motion, and reach-scale cover dynamics. For certain parameter combinations, no solutions exist. However, by adjusting the free parameters, one or several solutions can usually be found. The controls on and the feedbacks between the free parameters have so far been little studied, but may exert important controls on bedrock channel morphology and dynamics.
How to cite: Turowski, J.: Upscaling sediment-flux-dependent fluvial bedrock incision to long timescales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10291, https://doi.org/10.5194/egusphere-egu21-10291, 2021.
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Fluvial bedrock incision is driven by the impact of moving bedload particles. Mechanistic, sediment-flux-dependent incision models have been proposed, but the stream power incision model (SPIM) is frequently used to model landscape evolution over large spatial and temporal scales. This disconnect between the mechanistic understanding of fluvial bedrock incision on the process scale, and the way it is modelled on long time scales presents one of the current challenges in quantitative geomorphology. Here, a mechanistic model of fluvial bedrock incision that is rooted in current process understanding is explicitly upscaled to long time scales by integrating over the distribution of discharge. The model predicts a channel long profile form equivalent to the one yielded by the SPIM, but explicitly resolves the effects of channel width, cross-sectional shape, bedrock erodibility and discharge variability. The channel long profile chiefly depends on the mechanics of bedload transport, rather than bedrock incision. In addition to the imposed boundary conditions specifying the upstream supply of water and sediment, and the incision rate, the model includes four free parameters, describing the at-a-station hydraulic geometry of channel width, the dependence of bedload transport capacity on channel width, the threshold discharge of bedload motion, and reach-scale cover dynamics. For certain parameter combinations, no solutions exist. However, by adjusting the free parameters, one or several solutions can usually be found. The controls on and the feedbacks between the free parameters have so far been little studied, but may exert important controls on bedrock channel morphology and dynamics.
How to cite: Turowski, J.: Upscaling sediment-flux-dependent fluvial bedrock incision to long timescales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10291, https://doi.org/10.5194/egusphere-egu21-10291, 2021.
GM5.4 – Multi-scale Investigation of sediment transport processes in geophysical flows
EGU21-7089 | vPICO presentations | GM5.4
Combining TRIGRS and Massflow Models for the Assessment of Flash Flood Disasters Related to Sediment Supply in Mountainous WatershedsTong Sun, Xiekang Wang, and Xufeng Yan
Abstract: Evaluation of a large number of rainstorm disasters shows that the coupling effect of sediment supply and floodwaters is one predominant cause for the occurrence of flash flood disasters. Rainfall-induced shallow landslides often provide an adequate source of solid materials to recharge moving sediment during flash floods. In this study, we used the TRIGRS model to analyze the rainfall-related landslide stability in a mountainous basin and gain potential landslide volumes as potential sources for sediment loads. Then, with the calculated results of landslides as input, the Massflow model was used to evaluate how the landslides as sediment loads evolved with flows. The results showed that there was a large amount of sediment deposited in the channel, which can be initiated and transported by heavy rainfalls, leading to the destruction of villages at the mouth of gullies. In general, this study offers a strategy of evaluating sediment-coupled flash flood disasters that the TRIGRS can provides the estimate of landslide distribution and volume first and the Massflow provides the estimate of subsequent movement of the solids caused by flash floods.
Funded by: The National Key R&D Program of China (2019YFC1510702)
How to cite: Sun, T., Wang, X., and Yan, X.: Combining TRIGRS and Massflow Models for the Assessment of Flash Flood Disasters Related to Sediment Supply in Mountainous Watersheds, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7089, https://doi.org/10.5194/egusphere-egu21-7089, 2021.
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Abstract: Evaluation of a large number of rainstorm disasters shows that the coupling effect of sediment supply and floodwaters is one predominant cause for the occurrence of flash flood disasters. Rainfall-induced shallow landslides often provide an adequate source of solid materials to recharge moving sediment during flash floods. In this study, we used the TRIGRS model to analyze the rainfall-related landslide stability in a mountainous basin and gain potential landslide volumes as potential sources for sediment loads. Then, with the calculated results of landslides as input, the Massflow model was used to evaluate how the landslides as sediment loads evolved with flows. The results showed that there was a large amount of sediment deposited in the channel, which can be initiated and transported by heavy rainfalls, leading to the destruction of villages at the mouth of gullies. In general, this study offers a strategy of evaluating sediment-coupled flash flood disasters that the TRIGRS can provides the estimate of landslide distribution and volume first and the Massflow provides the estimate of subsequent movement of the solids caused by flash floods.
Funded by: The National Key R&D Program of China (2019YFC1510702)
How to cite: Sun, T., Wang, X., and Yan, X.: Combining TRIGRS and Massflow Models for the Assessment of Flash Flood Disasters Related to Sediment Supply in Mountainous Watersheds, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7089, https://doi.org/10.5194/egusphere-egu21-7089, 2021.
EGU21-7091 | vPICO presentations | GM5.4
Particle-scale fluid-particle interactions in particle-laden gravity flows over the flat slopeJiafeng Xie and Peng Hu
This study used the LES-DEM (Large-Eddy Simulation and Discrete Element Method) model to simulate the lock-exchange particle-laden gravity flow over a flat slope and studied its fluid-particle interactions. The following understandings are obtained. According to the longitudinal particle-fluid interaction force, the flat-slope lock-exchange PGF process can be divided into two stages: fluid conveying particles (Stage I) and particles pushing fluid (Stage II). In the early Stage I, due to the positive vorticity and the positive slip velocity, the lift force plays a leading role in the interaction force. And in the later Stage I, the drag force causes the fluid to push the particles when the lift force decreases and becomes negative due to the negative vorticity caused by the bottom resistance. In Stage II, the lift force hinders the particles’ advancement, which exceeds the drag force that transports the particles forward. The vertical suspension of particles mainly benefits from drag force and contact force, and the former is more prominent. In addition, the longitudinal transport of head particles is mainly controlled by the lift force caused by positive vorticity which is cause by the resistance from the ambient fluid at the current profile. Based on the interaction force, the study distinguishes two energy conversion modes. The final destination of the energy in the two modes is longitudinal particle kinetic energy and longitudinal fluid kinetic energy, respectively.
How to cite: Xie, J. and Hu, P.: Particle-scale fluid-particle interactions in particle-laden gravity flows over the flat slope, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7091, https://doi.org/10.5194/egusphere-egu21-7091, 2021.
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This study used the LES-DEM (Large-Eddy Simulation and Discrete Element Method) model to simulate the lock-exchange particle-laden gravity flow over a flat slope and studied its fluid-particle interactions. The following understandings are obtained. According to the longitudinal particle-fluid interaction force, the flat-slope lock-exchange PGF process can be divided into two stages: fluid conveying particles (Stage I) and particles pushing fluid (Stage II). In the early Stage I, due to the positive vorticity and the positive slip velocity, the lift force plays a leading role in the interaction force. And in the later Stage I, the drag force causes the fluid to push the particles when the lift force decreases and becomes negative due to the negative vorticity caused by the bottom resistance. In Stage II, the lift force hinders the particles’ advancement, which exceeds the drag force that transports the particles forward. The vertical suspension of particles mainly benefits from drag force and contact force, and the former is more prominent. In addition, the longitudinal transport of head particles is mainly controlled by the lift force caused by positive vorticity which is cause by the resistance from the ambient fluid at the current profile. Based on the interaction force, the study distinguishes two energy conversion modes. The final destination of the energy in the two modes is longitudinal particle kinetic energy and longitudinal fluid kinetic energy, respectively.
How to cite: Xie, J. and Hu, P.: Particle-scale fluid-particle interactions in particle-laden gravity flows over the flat slope, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7091, https://doi.org/10.5194/egusphere-egu21-7091, 2021.
EGU21-8169 | vPICO presentations | GM5.4
Large scale filed experiment on the landslide dam breachingWei Huang and Wengang Duan
Landslide dam breaching is the one of focus topics in the geophysical flows. The frequency of occurrence of landslide dam increases due to earthquake, climate change and mans activities in recent years. Once the dam breaks, it would trigger extreme flood downstream. A field experiment on landslide dam breach has been carried out on a small mountain river in Mianzhu, Sichuan Province, China from 23 November to 29 December, which aims to reveal impact of different diversion channel types on the dam breaching process as well as the resulting flood. The dam is of 4m high, 10~15m wide. the length of the dam crest is 5m, upstream downstream slopes of the dam are 1:2 and 1:5. Results show division channel can reduce the peak flood discharge obviously. The pilot vertical fall can trigger earlier back erosion and thus peak discharge appears earlier with smaller magnitude.
How to cite: Huang, W. and Duan, W.: Large scale filed experiment on the landslide dam breaching, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8169, https://doi.org/10.5194/egusphere-egu21-8169, 2021.
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Landslide dam breaching is the one of focus topics in the geophysical flows. The frequency of occurrence of landslide dam increases due to earthquake, climate change and mans activities in recent years. Once the dam breaks, it would trigger extreme flood downstream. A field experiment on landslide dam breach has been carried out on a small mountain river in Mianzhu, Sichuan Province, China from 23 November to 29 December, which aims to reveal impact of different diversion channel types on the dam breaching process as well as the resulting flood. The dam is of 4m high, 10~15m wide. the length of the dam crest is 5m, upstream downstream slopes of the dam are 1:2 and 1:5. Results show division channel can reduce the peak flood discharge obviously. The pilot vertical fall can trigger earlier back erosion and thus peak discharge appears earlier with smaller magnitude.
How to cite: Huang, W. and Duan, W.: Large scale filed experiment on the landslide dam breaching, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8169, https://doi.org/10.5194/egusphere-egu21-8169, 2021.
EGU21-9273 | vPICO presentations | GM5.4
Removal of a dense bottom layer by a gravity currentRui Zhu, Zhiguo He, and Eckart Meiburg
We investigate the removal of a dense bottom layer by a gravity current, via Navier-Stokes Boussinesq simulations. The problem is governed by a dimensionless thickness parameter for the bottom layer, and by the ratio of two density differences. A quasisteady gravity current propagates along the interface and displaces some of the dense bottom fluid, which accumulates ahead of the gravity current and forms an undular bore or a series of internal gravity waves. Depending on the ratio of the gravity current front velocity to the linear shallow-water wave velocity, we observe small-amplitude waves or a train of steep, nonlinear internal waves. We develop a self-contained model based on the conservation principles for mass and vorticity that does not require empirical closure assumptions. This model is able to predict the gravity current height and the internal wave or bore velocity, generally to within about 10% accuracy. An energy budget analysis provides information on the rates at which potential energy is converted into kinetic energy and then dissipated, and on the processes by which energy is transferred from the gravity current fluid to the dense and ambient fluids. We observe that the energy content of thicker and denser bottom layers grows more rapidly.
How to cite: Zhu, R., He, Z., and Meiburg, E.: Removal of a dense bottom layer by a gravity current, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9273, https://doi.org/10.5194/egusphere-egu21-9273, 2021.
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We investigate the removal of a dense bottom layer by a gravity current, via Navier-Stokes Boussinesq simulations. The problem is governed by a dimensionless thickness parameter for the bottom layer, and by the ratio of two density differences. A quasisteady gravity current propagates along the interface and displaces some of the dense bottom fluid, which accumulates ahead of the gravity current and forms an undular bore or a series of internal gravity waves. Depending on the ratio of the gravity current front velocity to the linear shallow-water wave velocity, we observe small-amplitude waves or a train of steep, nonlinear internal waves. We develop a self-contained model based on the conservation principles for mass and vorticity that does not require empirical closure assumptions. This model is able to predict the gravity current height and the internal wave or bore velocity, generally to within about 10% accuracy. An energy budget analysis provides information on the rates at which potential energy is converted into kinetic energy and then dissipated, and on the processes by which energy is transferred from the gravity current fluid to the dense and ambient fluids. We observe that the energy content of thicker and denser bottom layers grows more rapidly.
How to cite: Zhu, R., He, Z., and Meiburg, E.: Removal of a dense bottom layer by a gravity current, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9273, https://doi.org/10.5194/egusphere-egu21-9273, 2021.
EGU21-1808 | vPICO presentations | GM5.4
An initial assessment of bed destabilization risk past vegetation patches using instrumented particlesYi Xu, Valyrakis Manousos, and Panagiotis Michalis
Instream vegetation may alter the mean and turbukent flow fields leading to destabilizing riverbed surface, under certain flow conditions. In particular, recent research on instream vegetation hydrodynamics and ecohydrogeomorphology has focused on how energetic flow structures and bulk flow parameters downstream a vegetation may result in riverbed destabilization. This study, demonstrated the application of a 20mm novel instrumented particle in recording entrainment rates downstream simulated vegetation patches of distinct densities, at various distances downstream these. A patch of 6mm acrilic cylinders is used to simulate the emergent vegetation having the same diameter (12cm) and different porosities or densities (void volume equal to 1.25%, 3.15%, 6.25%, 11.25%, and 17.25%). The flow velocity near the instrumented particle is recorded using acoustic Doppler velocimetry (ADV) with appropriate seeding, under clear water conditions. Preliminary results are presented with focus on the effect of vegetation patch density on the flow field and subsequent effects on particle entrainment rates and implications for bed surface destabilisation.
How to cite: Xu, Y., Manousos, V., and Michalis, P.: An initial assessment of bed destabilization risk past vegetation patches using instrumented particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1808, https://doi.org/10.5194/egusphere-egu21-1808, 2021.
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Instream vegetation may alter the mean and turbukent flow fields leading to destabilizing riverbed surface, under certain flow conditions. In particular, recent research on instream vegetation hydrodynamics and ecohydrogeomorphology has focused on how energetic flow structures and bulk flow parameters downstream a vegetation may result in riverbed destabilization. This study, demonstrated the application of a 20mm novel instrumented particle in recording entrainment rates downstream simulated vegetation patches of distinct densities, at various distances downstream these. A patch of 6mm acrilic cylinders is used to simulate the emergent vegetation having the same diameter (12cm) and different porosities or densities (void volume equal to 1.25%, 3.15%, 6.25%, 11.25%, and 17.25%). The flow velocity near the instrumented particle is recorded using acoustic Doppler velocimetry (ADV) with appropriate seeding, under clear water conditions. Preliminary results are presented with focus on the effect of vegetation patch density on the flow field and subsequent effects on particle entrainment rates and implications for bed surface destabilisation.
How to cite: Xu, Y., Manousos, V., and Michalis, P.: An initial assessment of bed destabilization risk past vegetation patches using instrumented particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1808, https://doi.org/10.5194/egusphere-egu21-1808, 2021.
EGU21-10462 | vPICO presentations | GM5.4
Devastating hyper-concentrated flood on the Loess Plateau, China: simulations and implicationsGa Zhang, Chenge An, and Xudong Fu
Yellow River has long been suffered from floods and sedimentation in the history, and has brought great catastrophes to the Chinese nation. Therefore, the Yellow River is also called the “China’s sorrow”. From July 25 to 26 of 2017, most of the northern part of the Shanxi and Shannxi Province in the middle Yellow River basin encountered high intensity rainfall with the maximum rainfall of 223.6 mm. In the abstract below, we term this rainfall event as the “7.26 storm”. After the extreme rainfall, hyper-concentrated floods occurred in the Dali River and Wuding River, which are tributaries of the Yellow River. The objective of this research is to study the hyper-concentrated floods of the Wuding River (with a drainage area of 28460 km2) at hourly time-step with a numerical model. The model that we utilized is the Digital Yellow River Model (DYRIM), which a physically based spatially distributed model of watershed sediment dynamics. Due to lack of sub-daily observation data, we first calibrate and verify the model at daily time-step. Then we apply the model to simulate the 7.26 storm at hourly time-step. Results show the DYRIM could well reproduce the peak discharge, peak sediment concentration, flood timing and volume, when compared with the measured data. Furthermore, the DYRIM is able to (1) delineate spatial distribution of hillslope erosion intensity, maximum erosion intensity could reach 10000 t/km2; (2) provide information about proportion of different sources of sediment, channel erosion is the main source of the sediment to the outlet and (3) analysis the influence of check-dams on flow and sediment, the dam trapped about 40 millions tons sediment, their effect on water and sediment reduction under extreme rainfall events is limited though.
How to cite: Zhang, G., An, C., and Fu, X.: Devastating hyper-concentrated flood on the Loess Plateau, China: simulations and implications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10462, https://doi.org/10.5194/egusphere-egu21-10462, 2021.
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Yellow River has long been suffered from floods and sedimentation in the history, and has brought great catastrophes to the Chinese nation. Therefore, the Yellow River is also called the “China’s sorrow”. From July 25 to 26 of 2017, most of the northern part of the Shanxi and Shannxi Province in the middle Yellow River basin encountered high intensity rainfall with the maximum rainfall of 223.6 mm. In the abstract below, we term this rainfall event as the “7.26 storm”. After the extreme rainfall, hyper-concentrated floods occurred in the Dali River and Wuding River, which are tributaries of the Yellow River. The objective of this research is to study the hyper-concentrated floods of the Wuding River (with a drainage area of 28460 km2) at hourly time-step with a numerical model. The model that we utilized is the Digital Yellow River Model (DYRIM), which a physically based spatially distributed model of watershed sediment dynamics. Due to lack of sub-daily observation data, we first calibrate and verify the model at daily time-step. Then we apply the model to simulate the 7.26 storm at hourly time-step. Results show the DYRIM could well reproduce the peak discharge, peak sediment concentration, flood timing and volume, when compared with the measured data. Furthermore, the DYRIM is able to (1) delineate spatial distribution of hillslope erosion intensity, maximum erosion intensity could reach 10000 t/km2; (2) provide information about proportion of different sources of sediment, channel erosion is the main source of the sediment to the outlet and (3) analysis the influence of check-dams on flow and sediment, the dam trapped about 40 millions tons sediment, their effect on water and sediment reduction under extreme rainfall events is limited though.
How to cite: Zhang, G., An, C., and Fu, X.: Devastating hyper-concentrated flood on the Loess Plateau, China: simulations and implications, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10462, https://doi.org/10.5194/egusphere-egu21-10462, 2021.
EGU21-10565 | vPICO presentations | GM5.4
Experimental Study of Three-Dimensional Obstacle Effect on Velocity Structure of Density CurrentsJingyao Chen, Yanan Chen, Zhiguo He, and Benjamin Kneller
The density currents’ velocity structure, which can be divided into a jet region (JR) and a wall region (WR, thickness hr) according to their distinct dynamics, may be significantly modified as the current crosses an obstacle, thus leading to variations in the flow propagation process. However, there is a lack of direct observation of the response of different parts of the velocity structure to a three-dimensional obstacle due to the challenges in 3-D flow field measurement. To address this knowledge gap, a series of laboratory experiments have been devised to examine the separate influence of the WR and JR on mixing and propagation processes of density currents. A particle image velocimetry system and a high-speed camera are used to obtain the detailed velocity and vorticity fields with high temporal resolution. Compared with the no-obstacle counterpart that is uniform in the spanwise direction, the time-averaged current height (hc) in obstacle cases gradually thickens in that direction, and both the WR and JR thicken accordingly. The ratio of the obstacle height (ho) to hc influences the velocity structure. Specifically, hr/hc upstream is larger than that downstream when ho>hc, and vice versa. It is noteworthy that the variation of hr/hc in the spanwise direction is nonmonotonic with ho. Furthermore, the obstacle also influences the velocity profile upstream. The flow is obstructed on the center line when ho>hc. When ho<hr, the obstacle divides the wall region upstream into two parts above and below ho, and the gradient of the velocity profiles of the upper one is larger than the lower one. The results suggest that the obstacle plays an important role in determining the dissipation on the interface between the JR and the environment, and changing the current’s capacity on carrying the sediment since both the settling and resuspension of particles and sediment mostly happen in the WR. Our findings can improve understanding of the influence of submarine topography and provide a reference for underwater engineering.
How to cite: Chen, J., Chen, Y., He, Z., and Kneller, B.: Experimental Study of Three-Dimensional Obstacle Effect on Velocity Structure of Density Currents, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10565, https://doi.org/10.5194/egusphere-egu21-10565, 2021.
The density currents’ velocity structure, which can be divided into a jet region (JR) and a wall region (WR, thickness hr) according to their distinct dynamics, may be significantly modified as the current crosses an obstacle, thus leading to variations in the flow propagation process. However, there is a lack of direct observation of the response of different parts of the velocity structure to a three-dimensional obstacle due to the challenges in 3-D flow field measurement. To address this knowledge gap, a series of laboratory experiments have been devised to examine the separate influence of the WR and JR on mixing and propagation processes of density currents. A particle image velocimetry system and a high-speed camera are used to obtain the detailed velocity and vorticity fields with high temporal resolution. Compared with the no-obstacle counterpart that is uniform in the spanwise direction, the time-averaged current height (hc) in obstacle cases gradually thickens in that direction, and both the WR and JR thicken accordingly. The ratio of the obstacle height (ho) to hc influences the velocity structure. Specifically, hr/hc upstream is larger than that downstream when ho>hc, and vice versa. It is noteworthy that the variation of hr/hc in the spanwise direction is nonmonotonic with ho. Furthermore, the obstacle also influences the velocity profile upstream. The flow is obstructed on the center line when ho>hc. When ho<hr, the obstacle divides the wall region upstream into two parts above and below ho, and the gradient of the velocity profiles of the upper one is larger than the lower one. The results suggest that the obstacle plays an important role in determining the dissipation on the interface between the JR and the environment, and changing the current’s capacity on carrying the sediment since both the settling and resuspension of particles and sediment mostly happen in the WR. Our findings can improve understanding of the influence of submarine topography and provide a reference for underwater engineering.
How to cite: Chen, J., Chen, Y., He, Z., and Kneller, B.: Experimental Study of Three-Dimensional Obstacle Effect on Velocity Structure of Density Currents, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10565, https://doi.org/10.5194/egusphere-egu21-10565, 2021.
EGU21-3589 | vPICO presentations | GM5.4 | Highlight
Development and calibration of instrumented rock for monitoring rockfallsPeng Gu and Manousos Valyrakis
Rockfalls can be detrimental to the safety of people and exposed infrastructure or property. Especially in the mountainous areas, rockfall disasters are common and unpredictable. In many countries and regions around the world, rockfalls have directly and indirectly caused great economic losses and even loss of life. In Scotland, an average of 1.4 million pounds a year is lost due to rockfalls. In China, a direct economic loss of 170 million pounds was caused and 858 people were killed by rockfalls In 2018. Most of the current prevention methods are costly and time-consuming. The objective of this study is to develop a new sensor that could monitor the dynamics of rockfall process. This paper discusses the development and calibration of a spherical instrumented rock with low-cost sensors, simulating spherical rocks and stones, which can be used to record the triaxial accelerations and angular velocities. The instrumented rock is tested on an appropriately designed dry flume for a range of slopes and fixed bed roughness. The preliminary experimental setup and results will be presented and discussed. By utilizing the impact forces obtained from the instrumented rock for the assessment for rock-fall dynamics with the designed dry flume physical experiments, we demonstrate how rockfall hazards can be monitored directly or indirectly using a low-cost tool.
Key words: rockfalls, instrumented rock, sensors, dynamics of process, earth surface hazards
How to cite: Gu, P. and Valyrakis, M.: Development and calibration of instrumented rock for monitoring rockfalls, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3589, https://doi.org/10.5194/egusphere-egu21-3589, 2021.
Rockfalls can be detrimental to the safety of people and exposed infrastructure or property. Especially in the mountainous areas, rockfall disasters are common and unpredictable. In many countries and regions around the world, rockfalls have directly and indirectly caused great economic losses and even loss of life. In Scotland, an average of 1.4 million pounds a year is lost due to rockfalls. In China, a direct economic loss of 170 million pounds was caused and 858 people were killed by rockfalls In 2018. Most of the current prevention methods are costly and time-consuming. The objective of this study is to develop a new sensor that could monitor the dynamics of rockfall process. This paper discusses the development and calibration of a spherical instrumented rock with low-cost sensors, simulating spherical rocks and stones, which can be used to record the triaxial accelerations and angular velocities. The instrumented rock is tested on an appropriately designed dry flume for a range of slopes and fixed bed roughness. The preliminary experimental setup and results will be presented and discussed. By utilizing the impact forces obtained from the instrumented rock for the assessment for rock-fall dynamics with the designed dry flume physical experiments, we demonstrate how rockfall hazards can be monitored directly or indirectly using a low-cost tool.
Key words: rockfalls, instrumented rock, sensors, dynamics of process, earth surface hazards
How to cite: Gu, P. and Valyrakis, M.: Development and calibration of instrumented rock for monitoring rockfalls, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3589, https://doi.org/10.5194/egusphere-egu21-3589, 2021.
EGU21-3819 | vPICO presentations | GM5.4
Morphological effects of a hydraulic lifting dam on the middle Fenhe River, ChinaYufang Ni, Zhixian Cao, Wenjun Qi, Xiangbin Chai, and Aili Zhao
Hydraulic lifting dams become increasingly popular in China for water storage, river landscaping and environmental restoration. Inevitably, dams influence riverine morphology. Unfortunately, current understanding of this topic has remained rather limited. Here, the morphological effects of a hydraulic lifting dam on the middle Fenhe River, China are investigated. This reach features a compound channel and floodplains, and the riverbed is mainly composed of silt that can be easily eroded, indicating potential significant bed deformation. A computationally efficient depth-averaged two-dimensional shallow water hydro-sediment-morphodynamic model is employed. Unstructured meshes are refined around dam structures to accurately present topography. The numerical predictions show discrepancies of morphological responses of the main channel and floodplains to different operation schemes of the hydraulic lifting dam. This work helps to support decisions on the management of hydraulic lifting dams on the middle Fenhe River and reveals a general pattern for the morphological impact of hydraulic lifting dam.
How to cite: Ni, Y., Cao, Z., Qi, W., Chai, X., and Zhao, A.: Morphological effects of a hydraulic lifting dam on the middle Fenhe River, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3819, https://doi.org/10.5194/egusphere-egu21-3819, 2021.
Hydraulic lifting dams become increasingly popular in China for water storage, river landscaping and environmental restoration. Inevitably, dams influence riverine morphology. Unfortunately, current understanding of this topic has remained rather limited. Here, the morphological effects of a hydraulic lifting dam on the middle Fenhe River, China are investigated. This reach features a compound channel and floodplains, and the riverbed is mainly composed of silt that can be easily eroded, indicating potential significant bed deformation. A computationally efficient depth-averaged two-dimensional shallow water hydro-sediment-morphodynamic model is employed. Unstructured meshes are refined around dam structures to accurately present topography. The numerical predictions show discrepancies of morphological responses of the main channel and floodplains to different operation schemes of the hydraulic lifting dam. This work helps to support decisions on the management of hydraulic lifting dams on the middle Fenhe River and reveals a general pattern for the morphological impact of hydraulic lifting dam.
How to cite: Ni, Y., Cao, Z., Qi, W., Chai, X., and Zhao, A.: Morphological effects of a hydraulic lifting dam on the middle Fenhe River, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3819, https://doi.org/10.5194/egusphere-egu21-3819, 2021.
EGU21-4146 | vPICO presentations | GM5.4
A Coupled CFD-DEM Simulation of Immersed Granular CollapseYunhui Sun, Xiaoliang Wang, and Qingquan Liu
Natural disasters normally involve the flow of polydispersed granular materials with interstitial fluid which may change the flow dramatically. Here we focus on a typical small-scale case of fluid–particle mixture flows, i.e., the immersed granular collapse using computational fluid dynamics coupled with discrete element method (CFD-DEM). The simulation parameters are calibrated with laboratory experiments and the immersed granular collapse process is reproduced in terms of different aspect ratios. We present a deeper investigation of the collapse based on simulation results. The granular front evolves in three stages, i.e., acceleration, steady propagation, and deceleration. We found that the constant propagation stage is maintained by the transition of particles’ motion from vertical to horizontal and the drag of the fluid. The constant propagation velocity is proportional to the free-fall velocity with a Stokes-number-dependent coefficient and the normalized final runout is linearly correlated with the densimetric Froude number. These conclusions may find its significance in geophysical applications.
How to cite: Sun, Y., Wang, X., and Liu, Q.: A Coupled CFD-DEM Simulation of Immersed Granular Collapse, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4146, https://doi.org/10.5194/egusphere-egu21-4146, 2021.
Natural disasters normally involve the flow of polydispersed granular materials with interstitial fluid which may change the flow dramatically. Here we focus on a typical small-scale case of fluid–particle mixture flows, i.e., the immersed granular collapse using computational fluid dynamics coupled with discrete element method (CFD-DEM). The simulation parameters are calibrated with laboratory experiments and the immersed granular collapse process is reproduced in terms of different aspect ratios. We present a deeper investigation of the collapse based on simulation results. The granular front evolves in three stages, i.e., acceleration, steady propagation, and deceleration. We found that the constant propagation stage is maintained by the transition of particles’ motion from vertical to horizontal and the drag of the fluid. The constant propagation velocity is proportional to the free-fall velocity with a Stokes-number-dependent coefficient and the normalized final runout is linearly correlated with the densimetric Froude number. These conclusions may find its significance in geophysical applications.
How to cite: Sun, Y., Wang, X., and Liu, Q.: A Coupled CFD-DEM Simulation of Immersed Granular Collapse, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4146, https://doi.org/10.5194/egusphere-egu21-4146, 2021.
EGU21-4258 | vPICO presentations | GM5.4
A computationally efficient two-phase hydro-sediment-morphdynamic model and its preliminary field applicationsBinghan Lyu, Peng Hu, Ji Li, Zhixian Cao, Wei Li, and Zhiguo He
While fluvial flows carrying relatively coarse sediments involve strong two-phase interactions, existing numerical modeling in the field-scale is mostly based on quasi-single phase flow model. Here a computationally efficient two-phase hydro-sediment-morphodynamic model is developed with a special focus on field applications. The hybrid LTS/GMaTS method originally developed for quasi-single flow model is extended to the present two-phase flow model, of which the achieved reduction in the computational cost facilitates the present field applications in the Taipingkou Waterway, Middle Yangtze River. To overcome numerical instabilities arising from the relatively large spatial and time steps in field case that lead to an issue of stiff source term, the following numerical treatments are proposed: implementation of theoretically-derived lower and upper limits for the inter-phase interactive forces. Moreover, to improve the numerical accuracy, the HLLC approximate Riemann solver is used for the water phase, whereas the FORCE solver is used for the sediment phase. Both the present two-phase flow model and the existing quasi-single-phase flow model are applied to a series of typical cases, including refilling of a dredged trench, a full dam-break flow in an abruptly widening channel and reproduction of the Taipingkou waterway, Middle Yangtze River. Compared with the quasi-single-phase flow model, the two-phase flow model has better performance as compared to the measure data and has more profound physical significance.
How to cite: Lyu, B., Hu, P., Li, J., Cao, Z., Li, W., and He, Z.: A computationally efficient two-phase hydro-sediment-morphdynamic model and its preliminary field applications , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4258, https://doi.org/10.5194/egusphere-egu21-4258, 2021.
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While fluvial flows carrying relatively coarse sediments involve strong two-phase interactions, existing numerical modeling in the field-scale is mostly based on quasi-single phase flow model. Here a computationally efficient two-phase hydro-sediment-morphodynamic model is developed with a special focus on field applications. The hybrid LTS/GMaTS method originally developed for quasi-single flow model is extended to the present two-phase flow model, of which the achieved reduction in the computational cost facilitates the present field applications in the Taipingkou Waterway, Middle Yangtze River. To overcome numerical instabilities arising from the relatively large spatial and time steps in field case that lead to an issue of stiff source term, the following numerical treatments are proposed: implementation of theoretically-derived lower and upper limits for the inter-phase interactive forces. Moreover, to improve the numerical accuracy, the HLLC approximate Riemann solver is used for the water phase, whereas the FORCE solver is used for the sediment phase. Both the present two-phase flow model and the existing quasi-single-phase flow model are applied to a series of typical cases, including refilling of a dredged trench, a full dam-break flow in an abruptly widening channel and reproduction of the Taipingkou waterway, Middle Yangtze River. Compared with the quasi-single-phase flow model, the two-phase flow model has better performance as compared to the measure data and has more profound physical significance.
How to cite: Lyu, B., Hu, P., Li, J., Cao, Z., Li, W., and He, Z.: A computationally efficient two-phase hydro-sediment-morphdynamic model and its preliminary field applications , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4258, https://doi.org/10.5194/egusphere-egu21-4258, 2021.
EGU21-4364 | vPICO presentations | GM5.4
Analytical approach unifying the two-regime scaling for bedload particle motionsZi Wu, Arvind Singh, Efi Foufoula-Georgiou, Michele Guala, Xudong Fu, and Guangqian Wang
Bedload particle hops are defined as successive motions of a particle from start to stop, characterizing one of the most fundamental processes describing bedload sediment transport in rivers. Although two transport regimes have been recently identified for short- and long-hops, respectively (Wu et al., Water Resour Res, 2020), there still lacks a theory explaining how the mean hop distance-travel time scaling may extend to cover the phenomenology of bedload particle motions. Here we propose a velocity-variation based formulation, and for the first time, we obtain analytical solution for the mean hop distance-travel time relation valid for the entire range of travel times, which agrees well with the measured data (Wu et al., J Fluid Mech, 2021). Regarding travel times, we identify three distinct regimes in terms of different scaling exponents: respectively as ~1.5 for an initial regime and ~5/3 for a transition regime, which define the short-hops; and 1 for the so-called Taylor dispersion regime defining long-hops. The corresponding probability density function of the hop distance is also analytically obtained and experimentally verified.
How to cite: Wu, Z., Singh, A., Foufoula-Georgiou, E., Guala, M., Fu, X., and Wang, G.: Analytical approach unifying the two-regime scaling for bedload particle motions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4364, https://doi.org/10.5194/egusphere-egu21-4364, 2021.
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Bedload particle hops are defined as successive motions of a particle from start to stop, characterizing one of the most fundamental processes describing bedload sediment transport in rivers. Although two transport regimes have been recently identified for short- and long-hops, respectively (Wu et al., Water Resour Res, 2020), there still lacks a theory explaining how the mean hop distance-travel time scaling may extend to cover the phenomenology of bedload particle motions. Here we propose a velocity-variation based formulation, and for the first time, we obtain analytical solution for the mean hop distance-travel time relation valid for the entire range of travel times, which agrees well with the measured data (Wu et al., J Fluid Mech, 2021). Regarding travel times, we identify three distinct regimes in terms of different scaling exponents: respectively as ~1.5 for an initial regime and ~5/3 for a transition regime, which define the short-hops; and 1 for the so-called Taylor dispersion regime defining long-hops. The corresponding probability density function of the hop distance is also analytically obtained and experimentally verified.
How to cite: Wu, Z., Singh, A., Foufoula-Georgiou, E., Guala, M., Fu, X., and Wang, G.: Analytical approach unifying the two-regime scaling for bedload particle motions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4364, https://doi.org/10.5194/egusphere-egu21-4364, 2021.
EGU21-4656 | vPICO presentations | GM5.4
Effects of tributary inflow and sediment input on reservoir turbidity current formation and evolutionYining Sun, Ji Li, Zhixian Cao, and Alistair G.L. Borthwick
For reservoirs built on a hyper-concentrated river, tributary inflow and sediment input may affect the formation and evolution of reservoir turbidity current, and accordingly bed morphology. However, the understanding of tributary effects on reservoir turbidity currents has remained poor. Here a series of laboratory-scale reservoir turbidity currents are investigated using a coupled 2D double layer-averaged shallow water hydro-sediment-morphodynamic model. It is shown that the tributary location may lead to distinctive effects on reservoir turbidity current. Clear-water flow from the tributary may cause the stable plunge point to migrate upstream, and reduce its front speed. Sediment-laden inflow from the tributary may increase the discharge, sediment concentration, and front speed of the turbidity current, and also cause the plunge point to migrate downstream when the tributary is located upstream of the plunge point. In contrast, if the tributary is located downstream of the plunge point, sediment-laden flow from the tributary causes the stable plunge point to migrate upstream, and while the tributary effects on discharge, sediment concentration, and front speed of the turbidity current are minor. A case study is presented as of the Guxian Reservoir (under planning) on the middle Yellow River, China. The present finding highlights the significance of tributary inflow and sediment input in the formation and propagation of reservoir turbidity current and also riverbed deformation. Appropriate account of tributary effects is warranted for long-term maintenance of reservoir capacity and maximum utilization of the reservoir.
How to cite: Sun, Y., Li, J., Cao, Z., and Borthwick, A. G. L.: Effects of tributary inflow and sediment input on reservoir turbidity current formation and evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4656, https://doi.org/10.5194/egusphere-egu21-4656, 2021.
For reservoirs built on a hyper-concentrated river, tributary inflow and sediment input may affect the formation and evolution of reservoir turbidity current, and accordingly bed morphology. However, the understanding of tributary effects on reservoir turbidity currents has remained poor. Here a series of laboratory-scale reservoir turbidity currents are investigated using a coupled 2D double layer-averaged shallow water hydro-sediment-morphodynamic model. It is shown that the tributary location may lead to distinctive effects on reservoir turbidity current. Clear-water flow from the tributary may cause the stable plunge point to migrate upstream, and reduce its front speed. Sediment-laden inflow from the tributary may increase the discharge, sediment concentration, and front speed of the turbidity current, and also cause the plunge point to migrate downstream when the tributary is located upstream of the plunge point. In contrast, if the tributary is located downstream of the plunge point, sediment-laden flow from the tributary causes the stable plunge point to migrate upstream, and while the tributary effects on discharge, sediment concentration, and front speed of the turbidity current are minor. A case study is presented as of the Guxian Reservoir (under planning) on the middle Yellow River, China. The present finding highlights the significance of tributary inflow and sediment input in the formation and propagation of reservoir turbidity current and also riverbed deformation. Appropriate account of tributary effects is warranted for long-term maintenance of reservoir capacity and maximum utilization of the reservoir.
How to cite: Sun, Y., Li, J., Cao, Z., and Borthwick, A. G. L.: Effects of tributary inflow and sediment input on reservoir turbidity current formation and evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4656, https://doi.org/10.5194/egusphere-egu21-4656, 2021.
EGU21-6889 | vPICO presentations | GM5.4
Effect of stress history on sediment transport and channel adjustment in graded gravel-bed riversChenge An, Marwan A. Hassan, Carles Ferrer-Boix, and Xudong Fu
Recently, there has been an increasing attention on the environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers. More specifically, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Such an effect is often termed as “stress history” effect. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this study, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.
How to cite: An, C., Hassan, M. A., Ferrer-Boix, C., and Fu, X.: Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6889, https://doi.org/10.5194/egusphere-egu21-6889, 2021.
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Recently, there has been an increasing attention on the environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers. More specifically, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Such an effect is often termed as “stress history” effect. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this study, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.
How to cite: An, C., Hassan, M. A., Ferrer-Boix, C., and Fu, X.: Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6889, https://doi.org/10.5194/egusphere-egu21-6889, 2021.
EGU21-5490 | vPICO presentations | GM5.4
Typical debris-flow barrier dams and associated outburst floods in the southeastern TibetKaiheng Hu, Xiaopeng Zhang, and Li Wei
Large-magnitude debris flows up to a volume of 1.0 million m3 happen frequently in the southeastern margin of Tibetan plateau due to rapid rock uplift, high relief and abundant rainfall. These flows with high bulk density can easily block main rivers. Such debris-flow barrier dams fail very quickly, resulting in outburst floods and intensive sed-iment transport. We collect data of four recent large-scale debris-flow damming events at Peilong, Yigong, Tianmo and Sedongpu catch-ments, and examine the process of riverbank erosion and sediment transportation under dam narrowing and outburst flooding. More than 10% of debris mass was delivered downstream when the dams breached. It is concluded that debris flow is main erosion way in this area, and the very high erosion rate play a key role on river morpholo-gy in southeast Tibet.
How to cite: Hu, K., Zhang, X., and Wei, L.: Typical debris-flow barrier dams and associated outburst floods in the southeastern Tibet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5490, https://doi.org/10.5194/egusphere-egu21-5490, 2021.
Large-magnitude debris flows up to a volume of 1.0 million m3 happen frequently in the southeastern margin of Tibetan plateau due to rapid rock uplift, high relief and abundant rainfall. These flows with high bulk density can easily block main rivers. Such debris-flow barrier dams fail very quickly, resulting in outburst floods and intensive sed-iment transport. We collect data of four recent large-scale debris-flow damming events at Peilong, Yigong, Tianmo and Sedongpu catch-ments, and examine the process of riverbank erosion and sediment transportation under dam narrowing and outburst flooding. More than 10% of debris mass was delivered downstream when the dams breached. It is concluded that debris flow is main erosion way in this area, and the very high erosion rate play a key role on river morpholo-gy in southeast Tibet.
How to cite: Hu, K., Zhang, X., and Wei, L.: Typical debris-flow barrier dams and associated outburst floods in the southeastern Tibet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5490, https://doi.org/10.5194/egusphere-egu21-5490, 2021.
EGU21-5854 | vPICO presentations | GM5.4
Effect of unsteady flows on the development and magnitude of bed formsLe Wang, Alan Cuthbertson, Gareth Pender, and Zhixian Cao
Sediment transport and associated morphological changes in alluvial rivers occur primarily under unsteady flow conditions that are manifested as well-defined flood hydrograph events. At present, typical bed forms generated by such unsteady flows is far less studied and, thus, more poorly understood, than equivalent bed forms generated under steady flow conditions. In view of this, the objective of this work is to investigate the development of morphological bed features, and specifically variability in the length, height and steepness of bed forms that develop in a mobile coarse-sand bed layer under unsteady flow hydrographs under zero sediment feed conditions. A series of laboratory flume experiments is conducted within which different flow hydrograph events are simulated physically by controlling their shape, unsteadiness and magnitude. Experimental results indicate that different categories of bed forms such as dunes, alternate bars or transitional dune-bar structures develop within the erodible bed layer when subject to varying hydrograph flow conditions. Examination of relative importance of three parameters used to describe the hydrograph characteristics (i.e. asymmetry, unsteadiness and total water work) on bed form dimensional descriptors (i.e. wavelength, height and steepness) reveals that hydrograph unsteadiness and total water work are the primary and second-order controls on bed deformations or corresponding bed form dimensions. By contrast, hydrograph asymmetry appears to have minimal or negligible influence on bed form development in terms of their type and magnitude. Based on these findings, a physical model was developed and tested to describe the effect of unsteady flow hydrographs with varying unsteadiness and total water work on the nature and size of resulting bed forms that are generated in sand-bed layers.
How to cite: Wang, L., Cuthbertson, A., Pender, G., and Cao, Z.: Effect of unsteady flows on the development and magnitude of bed forms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5854, https://doi.org/10.5194/egusphere-egu21-5854, 2021.
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Sediment transport and associated morphological changes in alluvial rivers occur primarily under unsteady flow conditions that are manifested as well-defined flood hydrograph events. At present, typical bed forms generated by such unsteady flows is far less studied and, thus, more poorly understood, than equivalent bed forms generated under steady flow conditions. In view of this, the objective of this work is to investigate the development of morphological bed features, and specifically variability in the length, height and steepness of bed forms that develop in a mobile coarse-sand bed layer under unsteady flow hydrographs under zero sediment feed conditions. A series of laboratory flume experiments is conducted within which different flow hydrograph events are simulated physically by controlling their shape, unsteadiness and magnitude. Experimental results indicate that different categories of bed forms such as dunes, alternate bars or transitional dune-bar structures develop within the erodible bed layer when subject to varying hydrograph flow conditions. Examination of relative importance of three parameters used to describe the hydrograph characteristics (i.e. asymmetry, unsteadiness and total water work) on bed form dimensional descriptors (i.e. wavelength, height and steepness) reveals that hydrograph unsteadiness and total water work are the primary and second-order controls on bed deformations or corresponding bed form dimensions. By contrast, hydrograph asymmetry appears to have minimal or negligible influence on bed form development in terms of their type and magnitude. Based on these findings, a physical model was developed and tested to describe the effect of unsteady flow hydrographs with varying unsteadiness and total water work on the nature and size of resulting bed forms that are generated in sand-bed layers.
How to cite: Wang, L., Cuthbertson, A., Pender, G., and Cao, Z.: Effect of unsteady flows on the development and magnitude of bed forms, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5854, https://doi.org/10.5194/egusphere-egu21-5854, 2021.
EGU21-6789 | vPICO presentations | GM5.4
Modelling Morphological Evolution of Deltaic Lobes in the Yellow River MouthWei Li, Lehong Zhu, and Peng Hu
In history, channel avulsion occurred frequently in the Yellow River Delta featuring by the combination of large-scale north-south shifts and small-scale evolution of “wandering-merging-meandering-diverting” patterns. However, these evolution processes are lack of quantitative investigations due to the complex interactions between riverine and tidal flows, and between sediment-laden flow and river bed as well. Since public observations are scarce, we numerically study this problem focusing on the controlling factors for reproducing the “wandering-merging-meandering” evolution patterns and the characteristics of relative morphological equilibrium under constant discharge and sediment conditions. Using a 2-D depth-averaged fully coupled morphological model, numerical experiments are carried out for a schematic Yellow River Delta. The results show that random disturbance on initial topography is the key factor to initiate wandering patterns. Moreover, the development of river patterns and the associated morphological time scales are strongly related to initial bed slopes and upstream discharge and sediment conditions. Generally, a small bed slope and a low discharge favor the formation of wandering patterns in the early stage, while a large bed slope and a high discharge may accelerate the merging and routing processes. In the case of upstream clear flow, channel formation is dominated by erosion processes. Yet with increasing sediment, it results from the combination of levee lip sedimentation and channel erosion. In addition, the flow routing may be facilitated by enhanced tidal ranges whereas decelerated when subaqueous sedimentation extends to the sea. Regarding the equilibrium state, the morphological time scales are 4~8 years in most cases and the width-depth ratio increases longitudinally following a power-law function.
How to cite: Li, W., Zhu, L., and Hu, P.: Modelling Morphological Evolution of Deltaic Lobes in the Yellow River Mouth, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6789, https://doi.org/10.5194/egusphere-egu21-6789, 2021.
In history, channel avulsion occurred frequently in the Yellow River Delta featuring by the combination of large-scale north-south shifts and small-scale evolution of “wandering-merging-meandering-diverting” patterns. However, these evolution processes are lack of quantitative investigations due to the complex interactions between riverine and tidal flows, and between sediment-laden flow and river bed as well. Since public observations are scarce, we numerically study this problem focusing on the controlling factors for reproducing the “wandering-merging-meandering” evolution patterns and the characteristics of relative morphological equilibrium under constant discharge and sediment conditions. Using a 2-D depth-averaged fully coupled morphological model, numerical experiments are carried out for a schematic Yellow River Delta. The results show that random disturbance on initial topography is the key factor to initiate wandering patterns. Moreover, the development of river patterns and the associated morphological time scales are strongly related to initial bed slopes and upstream discharge and sediment conditions. Generally, a small bed slope and a low discharge favor the formation of wandering patterns in the early stage, while a large bed slope and a high discharge may accelerate the merging and routing processes. In the case of upstream clear flow, channel formation is dominated by erosion processes. Yet with increasing sediment, it results from the combination of levee lip sedimentation and channel erosion. In addition, the flow routing may be facilitated by enhanced tidal ranges whereas decelerated when subaqueous sedimentation extends to the sea. Regarding the equilibrium state, the morphological time scales are 4~8 years in most cases and the width-depth ratio increases longitudinally following a power-law function.
How to cite: Li, W., Zhu, L., and Hu, P.: Modelling Morphological Evolution of Deltaic Lobes in the Yellow River Mouth, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6789, https://doi.org/10.5194/egusphere-egu21-6789, 2021.
EGU21-6798 | vPICO presentations | GM5.4
Numerical Simulation of Scouring in Overtopping Dam-break FlowCan Huang, Xiaoliang Wang, and Qingquan Liu
Overtopping dam-break flow has great harm to the earthen embankments due to the hydraulic erosion. Some researchers have carried out relevant model experiments, but it is difficult to achieve the experimental conditions for the actual situation. The common numerical simulation is to express the scouring process through the empirical relationship, which obviously could not reflect the real scouring process. In this paper, a new overtopping erosion model using Smoothed Particle Hydrodynamics (SPH) is proposed. When the shear stress on the sediment SPH particle exceeds the critical stress, the erosion process begins. Then, when a sediment SPH particle is completely eroded, it will begin to move and is described as a non-Newtonian fluid. The un-incipient sediment particles are treated as boundary. This model is well validated with plane dike-breach experiment, and has also achieved a good agreement with erodible bed dam-break experiment.
How to cite: Huang, C., Wang, X., and Liu, Q.: Numerical Simulation of Scouring in Overtopping Dam-break Flow, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6798, https://doi.org/10.5194/egusphere-egu21-6798, 2021.
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Overtopping dam-break flow has great harm to the earthen embankments due to the hydraulic erosion. Some researchers have carried out relevant model experiments, but it is difficult to achieve the experimental conditions for the actual situation. The common numerical simulation is to express the scouring process through the empirical relationship, which obviously could not reflect the real scouring process. In this paper, a new overtopping erosion model using Smoothed Particle Hydrodynamics (SPH) is proposed. When the shear stress on the sediment SPH particle exceeds the critical stress, the erosion process begins. Then, when a sediment SPH particle is completely eroded, it will begin to move and is described as a non-Newtonian fluid. The un-incipient sediment particles are treated as boundary. This model is well validated with plane dike-breach experiment, and has also achieved a good agreement with erodible bed dam-break experiment.
How to cite: Huang, C., Wang, X., and Liu, Q.: Numerical Simulation of Scouring in Overtopping Dam-break Flow, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6798, https://doi.org/10.5194/egusphere-egu21-6798, 2021.
EGU21-6884 | vPICO presentations | GM5.4
Numerical study on the effect of edge scouring on stability of soft mattress in the Yangtze estuaryAofei Ji, Peng Hu, Zhiguo He, and Fengfeng Gu
Abstract: In the Yangtze River Estuary deep-water channel regulation project, soft mattresses have been widely used to reduce bed erosion and thus improve stability of bridges/piers/levees/dikes. However, soft mattresses are also subject to failure due to the continuous and gradual scour in their edges, which have been a major risk for their stability. Here we report a preliminary numerical study on this issue. Firstly, a depth-averaged two-dimensional hydro-sediment-morphodynamic model is applied to simulate edge scour process for the submerged dike of the Jiangyanansha in the Yangtze estuary. For this purpose, physically-based sediment erosion parameterization is proposed to take account of the effect of the soft mattresses. Compared with the inner area of the soft mattress, only the edge area has stronger erodibility. Numerical comparative studies indicate that a scouring pit may develop to the vicinity of the submerged dike without the protection of the soft mattress, whereas under the protection of the soft mattress, the scouring pit can be largely controlled. Nevertheless, as the scouring process continues, the pit region and depth increase, which may finally lead to failure of the soft mattress. Finally, full 3D high-resolution simulations of the near-bed flow structure with/without edge scour are conducted using flow3D to shed light on the failure mechanisms of the soft mattresses.
Keywords: submerged dikes, soft mattress, erodibility, Yangtze estuary, edge scour, flow structure
How to cite: Ji, A., Hu, P., He, Z., and Gu, F.: Numerical study on the effect of edge scouring on stability of soft mattress in the Yangtze estuary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6884, https://doi.org/10.5194/egusphere-egu21-6884, 2021.
Abstract: In the Yangtze River Estuary deep-water channel regulation project, soft mattresses have been widely used to reduce bed erosion and thus improve stability of bridges/piers/levees/dikes. However, soft mattresses are also subject to failure due to the continuous and gradual scour in their edges, which have been a major risk for their stability. Here we report a preliminary numerical study on this issue. Firstly, a depth-averaged two-dimensional hydro-sediment-morphodynamic model is applied to simulate edge scour process for the submerged dike of the Jiangyanansha in the Yangtze estuary. For this purpose, physically-based sediment erosion parameterization is proposed to take account of the effect of the soft mattresses. Compared with the inner area of the soft mattress, only the edge area has stronger erodibility. Numerical comparative studies indicate that a scouring pit may develop to the vicinity of the submerged dike without the protection of the soft mattress, whereas under the protection of the soft mattress, the scouring pit can be largely controlled. Nevertheless, as the scouring process continues, the pit region and depth increase, which may finally lead to failure of the soft mattress. Finally, full 3D high-resolution simulations of the near-bed flow structure with/without edge scour are conducted using flow3D to shed light on the failure mechanisms of the soft mattresses.
Keywords: submerged dikes, soft mattress, erodibility, Yangtze estuary, edge scour, flow structure
How to cite: Ji, A., Hu, P., He, Z., and Gu, F.: Numerical study on the effect of edge scouring on stability of soft mattress in the Yangtze estuary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6884, https://doi.org/10.5194/egusphere-egu21-6884, 2021.
EGU21-131 | vPICO presentations | GM5.4
ScourBuoy – concept for scour monitoring systemAntonija Harasti, Gordon Gilja, Matej Varga, and Robert Fliszar
The objective of this paper is to present the ScourBuoy – concept for scour monitoring system. The ScourBuoy prototype is currently under development within the R3PEAT project (Remote Real-time Riprap Protection Erosion AssessmenT on large rivers), which aims to investigate scouring processes next to the riprap protection around bridge piers. ScourBuoy integrates commercially available technical devices into a functional system for scour monitoring during flood conditions. Sensors used are single beam echo sounder that collects depth and temperature data, multi-GNSS device for 3D positioning, compass for orientation respective to the True North and motion sensor for pitch and roll data. Combined output from the sensors allows user to calculate river depth and monitoring of scour development during floods. Advantage of ScourBuoy is adaptability to the field conditions, such as placement over the scour hole, as well as simpler deployment and reallocation in comparison to fix-mount solutions. ScourBuoy prototype was built using a common small-scale pipe float with an 80 mm inner diameter hole, which was used as a holder for an aluminium pipe. Aluminium pipe is used as a casing for echo sounder, positioned as downward-looking, so it stays submerged during deployment. The rest of the sensors are enclosed in the waterproof housing placed atop of the buoy, permanently above the waterline. The ScourBuoy will be a practical and affordable system which will allow researchers and engineers to collect measurements for scouring estimation. It will be used as a support system for rapid and timely decision making. Finally, developed Scour Buoy will present an alternative for real-time scour monitoring which allows responsive adapting to the specific conditions at the locations affected by scour.
How to cite: Harasti, A., Gilja, G., Varga, M., and Fliszar, R.: ScourBuoy – concept for scour monitoring system, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-131, https://doi.org/10.5194/egusphere-egu21-131, 2021.
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The objective of this paper is to present the ScourBuoy – concept for scour monitoring system. The ScourBuoy prototype is currently under development within the R3PEAT project (Remote Real-time Riprap Protection Erosion AssessmenT on large rivers), which aims to investigate scouring processes next to the riprap protection around bridge piers. ScourBuoy integrates commercially available technical devices into a functional system for scour monitoring during flood conditions. Sensors used are single beam echo sounder that collects depth and temperature data, multi-GNSS device for 3D positioning, compass for orientation respective to the True North and motion sensor for pitch and roll data. Combined output from the sensors allows user to calculate river depth and monitoring of scour development during floods. Advantage of ScourBuoy is adaptability to the field conditions, such as placement over the scour hole, as well as simpler deployment and reallocation in comparison to fix-mount solutions. ScourBuoy prototype was built using a common small-scale pipe float with an 80 mm inner diameter hole, which was used as a holder for an aluminium pipe. Aluminium pipe is used as a casing for echo sounder, positioned as downward-looking, so it stays submerged during deployment. The rest of the sensors are enclosed in the waterproof housing placed atop of the buoy, permanently above the waterline. The ScourBuoy will be a practical and affordable system which will allow researchers and engineers to collect measurements for scouring estimation. It will be used as a support system for rapid and timely decision making. Finally, developed Scour Buoy will present an alternative for real-time scour monitoring which allows responsive adapting to the specific conditions at the locations affected by scour.
How to cite: Harasti, A., Gilja, G., Varga, M., and Fliszar, R.: ScourBuoy – concept for scour monitoring system, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-131, https://doi.org/10.5194/egusphere-egu21-131, 2021.
EGU21-171 | vPICO presentations | GM5.4
Scaling approach for physical modelling of pier scourRobert Fliszar, Gordon Gilja, Antonija Harasti, and Kristina Potočki
Physical modelling of local scour around bridge piers is challenging due to the three different similarity criteria that need to be satisfied for the complete similitude of the model and the prototype. To achieve the complete similitude, geometry, flow and sediment material in the model scale need to be scaled simultaneously. Aim of this paper is to calculate the scale parameters of the physical model used for scour assessment next to piers protected with riprap. The scale parameters are calculated individually for each prototype – two bridges located on the Drava River and one on the Sava River. Hydrological conditions are determined by analysis of flood wave amplitude and duration from the nearby hydrological station adjacent to the pilot bridge. Experiments will be conducted with different pier shapes and sizes, as well as with two different materials representing the riverbed – same density as prototype and lower density material. Range of discharges used for simulating various flow conditions are selected to be compatible with the flume pump capacity. To calculate required thickness of sediment trap layer in the hydraulic flume, expected scour depth is estimated. Sensitivity analysis of 13 empirical equations was conducted due to differences in hydraulic and geometric conditions of each prototype [1]. Bathymetric survey was the basis for establishing a numerical model, and its results were input parameters for empirical equations. Finally, scour depths were estimated as the average of all equations results except those results that turned out to be inadequate. Scaling affects the time parameter of the scouring process, and therefore an adequate time scale is calculated to achieve full development of the scour hole with respect to flow conditions. Finally, as a result of the flume restrictions, advantages and disadvantages of the physical model distortion are discussed.
[1] Cikojević, A., Gilja, G., Kuspilić, N.: Sensitivity analysis of empirical equations applicable on bridge piers in sand-bed rivers, Proceedings of International Symposium on Water Management and Hydraulic Engineering, Skopje, Republic of North Macedonia, pp. 100-108, (2019)
Acknowledgments
This work has been supported in part by Croatian Science Foundation under the project R3PEAT (UIP-2019-04-4046).
How to cite: Fliszar, R., Gilja, G., Harasti, A., and Potočki, K.: Scaling approach for physical modelling of pier scour, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-171, https://doi.org/10.5194/egusphere-egu21-171, 2021.
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Physical modelling of local scour around bridge piers is challenging due to the three different similarity criteria that need to be satisfied for the complete similitude of the model and the prototype. To achieve the complete similitude, geometry, flow and sediment material in the model scale need to be scaled simultaneously. Aim of this paper is to calculate the scale parameters of the physical model used for scour assessment next to piers protected with riprap. The scale parameters are calculated individually for each prototype – two bridges located on the Drava River and one on the Sava River. Hydrological conditions are determined by analysis of flood wave amplitude and duration from the nearby hydrological station adjacent to the pilot bridge. Experiments will be conducted with different pier shapes and sizes, as well as with two different materials representing the riverbed – same density as prototype and lower density material. Range of discharges used for simulating various flow conditions are selected to be compatible with the flume pump capacity. To calculate required thickness of sediment trap layer in the hydraulic flume, expected scour depth is estimated. Sensitivity analysis of 13 empirical equations was conducted due to differences in hydraulic and geometric conditions of each prototype [1]. Bathymetric survey was the basis for establishing a numerical model, and its results were input parameters for empirical equations. Finally, scour depths were estimated as the average of all equations results except those results that turned out to be inadequate. Scaling affects the time parameter of the scouring process, and therefore an adequate time scale is calculated to achieve full development of the scour hole with respect to flow conditions. Finally, as a result of the flume restrictions, advantages and disadvantages of the physical model distortion are discussed.
[1] Cikojević, A., Gilja, G., Kuspilić, N.: Sensitivity analysis of empirical equations applicable on bridge piers in sand-bed rivers, Proceedings of International Symposium on Water Management and Hydraulic Engineering, Skopje, Republic of North Macedonia, pp. 100-108, (2019)
Acknowledgments
This work has been supported in part by Croatian Science Foundation under the project R3PEAT (UIP-2019-04-4046).
How to cite: Fliszar, R., Gilja, G., Harasti, A., and Potočki, K.: Scaling approach for physical modelling of pier scour, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-171, https://doi.org/10.5194/egusphere-egu21-171, 2021.
EGU21-1820 | vPICO presentations | GM5.4
Exploring probability distribution functions best-fitting the kinetic energy of coarse particles at above threshold flow conditionsHamed Farhadi and Manousos Valyrakis
Applying an instrumented particle [1-3], the probability density functions of kinetic energy of a coarse particle (at different solid densities) mobilised over a range of above threshold flow conditions conditions corresponding to the intermittent transport regime, were explored. The experiments were conducted in the Water Engineering Lab at the University of Glasgow on a tilting recirculating flume with 800 (length) × 90 (width) cm dimension. Twelve different flow conditions corresponding to intermittent transport regime for the range of particle densities examined herein, have been implemented in this research. Ensuring fully developed flow conditions, the start of the test section was located at 3.2 meters upstream of the flume outlet. The bed surface of the flume is flat and made up of well-packed glass beads of 16.2 mm diameter, offering a uniform roughness over which the instrumented particle is transported. MEMS sensors are embedded within the instrumented particle with 3-axis gyroscope and 3-axis accelerometer. At the beginning of each experimental run, instrumented particle is placed at the upstream of the test section, fully exposed to the free stream flow. Its motion is recorded with top and side cameras to enable a deeper understanding of particle transport processes. Using results from sets of instrumented particle transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of the instrumented particles kinetic energy, were generated. The best-fitted PDFs were selected by applying the Kolmogorov-Smirnov test and the results were discussed considering the light of the recent literature of the particle velocity distributions.
[1] Valyrakis, M.; Alexakis, A. Development of a “smart-pebble” for tracking sediment transport. In Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2016), St. Louis, MO, USA, 12–15 July 2016.
[2] Al-Obaidi, K., Xu, Y. & Valyrakis, M. 2020, The Design and Calibration of Instrumented Particles for Assessing Water Infrastructure Hazards, Journal of Sensors and Actuator Networks, vol. 9, no. 3, 36.
[3] Al-Obaidi, K. & Valyrakis, M. 2020, Asensory instrumented particle for environmental monitoring applications: development and calibration, IEEE sensors journal (accepted).
How to cite: Farhadi, H. and Valyrakis, M.: Exploring probability distribution functions best-fitting the kinetic energy of coarse particles at above threshold flow conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1820, https://doi.org/10.5194/egusphere-egu21-1820, 2021.
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Applying an instrumented particle [1-3], the probability density functions of kinetic energy of a coarse particle (at different solid densities) mobilised over a range of above threshold flow conditions conditions corresponding to the intermittent transport regime, were explored. The experiments were conducted in the Water Engineering Lab at the University of Glasgow on a tilting recirculating flume with 800 (length) × 90 (width) cm dimension. Twelve different flow conditions corresponding to intermittent transport regime for the range of particle densities examined herein, have been implemented in this research. Ensuring fully developed flow conditions, the start of the test section was located at 3.2 meters upstream of the flume outlet. The bed surface of the flume is flat and made up of well-packed glass beads of 16.2 mm diameter, offering a uniform roughness over which the instrumented particle is transported. MEMS sensors are embedded within the instrumented particle with 3-axis gyroscope and 3-axis accelerometer. At the beginning of each experimental run, instrumented particle is placed at the upstream of the test section, fully exposed to the free stream flow. Its motion is recorded with top and side cameras to enable a deeper understanding of particle transport processes. Using results from sets of instrumented particle transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of the instrumented particles kinetic energy, were generated. The best-fitted PDFs were selected by applying the Kolmogorov-Smirnov test and the results were discussed considering the light of the recent literature of the particle velocity distributions.
[1] Valyrakis, M.; Alexakis, A. Development of a “smart-pebble” for tracking sediment transport. In Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2016), St. Louis, MO, USA, 12–15 July 2016.
[2] Al-Obaidi, K., Xu, Y. & Valyrakis, M. 2020, The Design and Calibration of Instrumented Particles for Assessing Water Infrastructure Hazards, Journal of Sensors and Actuator Networks, vol. 9, no. 3, 36.
[3] Al-Obaidi, K. & Valyrakis, M. 2020, Asensory instrumented particle for environmental monitoring applications: development and calibration, IEEE sensors journal (accepted).
How to cite: Farhadi, H. and Valyrakis, M.: Exploring probability distribution functions best-fitting the kinetic energy of coarse particles at above threshold flow conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1820, https://doi.org/10.5194/egusphere-egu21-1820, 2021.
EGU21-7022 | vPICO presentations | GM5.4
Unified model of sediment transport threshold and rate across subaqueous bedload, windblown sand, and windblown snowThomas Pähtz, Yonghui Liu, Yuezhang Xia, Peng Hu, Zhiguo He, and Katharina Tholen
Nonsuspended sediment transport (NST) refers to the sediment transport regime in which the flow turbulence is unable to support the weight of transported grains. It occurs in fluvial environments (i.e., driven by a stream of liquid) and in aeolian environments (i.e., wind-blown) and plays a key role in shaping sedimentary landscapes of planetary bodies. NST is a highly fluctuating physical process because of turbulence, surface inhomogeneities, and variations of grain size and shape and packing geometry. Furthermore, the energy of transported grains varies strongly due to variations of their flow exposure duration since their entrainment from the bed. In spite of such variability, we here propose a deterministic model that represents the entire grain motion, including grains that roll and/or slide along the bed, by a periodic saltation motion with rebound laws that describe an average rebound of a grain after colliding with the bed. The model simultaneously captures laboratory and field measurements and discrete element method (DEM)-based numerical simulations of the threshold and rate of equilibrium NST within a factor of about 2, unifying weak and intense transport conditions in oil, water, and air (oil only for threshold). The model parameters have not been adjusted to these measurements but determined from independent data sets. Recent DEM-based numerical simulations (Comola, Gaume, et al., 2019, https://doi.org/10.1029/2019GL082195) suggest that equilibrium aeolian NST on Earth is insensitive to the strength of cohesive bonds between bed grains. Consistently, the model captures cohesive windblown sand and windblown snow conditions despite not explicitly accounting for cohesion.
How to cite: Pähtz, T., Liu, Y., Xia, Y., Hu, P., He, Z., and Tholen, K.: Unified model of sediment transport threshold and rate across subaqueous bedload, windblown sand, and windblown snow, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7022, https://doi.org/10.5194/egusphere-egu21-7022, 2021.
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Nonsuspended sediment transport (NST) refers to the sediment transport regime in which the flow turbulence is unable to support the weight of transported grains. It occurs in fluvial environments (i.e., driven by a stream of liquid) and in aeolian environments (i.e., wind-blown) and plays a key role in shaping sedimentary landscapes of planetary bodies. NST is a highly fluctuating physical process because of turbulence, surface inhomogeneities, and variations of grain size and shape and packing geometry. Furthermore, the energy of transported grains varies strongly due to variations of their flow exposure duration since their entrainment from the bed. In spite of such variability, we here propose a deterministic model that represents the entire grain motion, including grains that roll and/or slide along the bed, by a periodic saltation motion with rebound laws that describe an average rebound of a grain after colliding with the bed. The model simultaneously captures laboratory and field measurements and discrete element method (DEM)-based numerical simulations of the threshold and rate of equilibrium NST within a factor of about 2, unifying weak and intense transport conditions in oil, water, and air (oil only for threshold). The model parameters have not been adjusted to these measurements but determined from independent data sets. Recent DEM-based numerical simulations (Comola, Gaume, et al., 2019, https://doi.org/10.1029/2019GL082195) suggest that equilibrium aeolian NST on Earth is insensitive to the strength of cohesive bonds between bed grains. Consistently, the model captures cohesive windblown sand and windblown snow conditions despite not explicitly accounting for cohesion.
How to cite: Pähtz, T., Liu, Y., Xia, Y., Hu, P., He, Z., and Tholen, K.: Unified model of sediment transport threshold and rate across subaqueous bedload, windblown sand, and windblown snow, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7022, https://doi.org/10.5194/egusphere-egu21-7022, 2021.
EGU21-5481 | vPICO presentations | GM5.4
Dynamics of Aeolian Sand Streamers and Airflow Turbulence over a Beach SurfaceAndreas Baas
Sand transport by wind over granular beds displays dynamic structure and organisation in the form of streamers (aka ‘sand snakes’) that appear, meander and intertwine, and then dissipate as they are advected downwind. These patterns of saltating grain populations are thought to be initiated and controlled by coherent flow structures in the turbulent boundary layer wind that scrape over the bed surface raking up sand into entrainment. Streamer behaviour is thus fundamental to understanding sand transport dynamics, in particular its strong spatio-temporal variability, and is equally relevant to granular transport in other geophysical flows (fluvial, submarine).
This paper presents findings on streamer dynamics and associated wind turbulence observed in a field experiment on a beach, with measurements from 30Hz video-imagery using Large-Scale Particle Image Velocimetry (LS-PIV), combined with 50Hz wind measurements from 3D sonic anemometry and co-located sand transport rate monitoring using an array of laser particle counters (‘Wenglors’), all taking place over an area of ~10 m2 and over periods of several minutes. The video imagery was used to identify when and where streamers advected past the sonic anemometer and laser sensors so that relationships could be detected between the passage of turbulence structures in the airflow and the length- and time-scales, propagation speeds, and sand transport intensities of associated streamers. The findings form the basis for a phenomenological model of streamer dynamics under turbulent boundary layer flows that predicts the impact of spatio-temporal variability on local measurement of sand transport.
How to cite: Baas, A.: Dynamics of Aeolian Sand Streamers and Airflow Turbulence over a Beach Surface, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5481, https://doi.org/10.5194/egusphere-egu21-5481, 2021.
Sand transport by wind over granular beds displays dynamic structure and organisation in the form of streamers (aka ‘sand snakes’) that appear, meander and intertwine, and then dissipate as they are advected downwind. These patterns of saltating grain populations are thought to be initiated and controlled by coherent flow structures in the turbulent boundary layer wind that scrape over the bed surface raking up sand into entrainment. Streamer behaviour is thus fundamental to understanding sand transport dynamics, in particular its strong spatio-temporal variability, and is equally relevant to granular transport in other geophysical flows (fluvial, submarine).
This paper presents findings on streamer dynamics and associated wind turbulence observed in a field experiment on a beach, with measurements from 30Hz video-imagery using Large-Scale Particle Image Velocimetry (LS-PIV), combined with 50Hz wind measurements from 3D sonic anemometry and co-located sand transport rate monitoring using an array of laser particle counters (‘Wenglors’), all taking place over an area of ~10 m2 and over periods of several minutes. The video imagery was used to identify when and where streamers advected past the sonic anemometer and laser sensors so that relationships could be detected between the passage of turbulence structures in the airflow and the length- and time-scales, propagation speeds, and sand transport intensities of associated streamers. The findings form the basis for a phenomenological model of streamer dynamics under turbulent boundary layer flows that predicts the impact of spatio-temporal variability on local measurement of sand transport.
How to cite: Baas, A.: Dynamics of Aeolian Sand Streamers and Airflow Turbulence over a Beach Surface, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5481, https://doi.org/10.5194/egusphere-egu21-5481, 2021.
EGU21-8148 | vPICO presentations | GM5.4
Collisional Langevin approach to bed load sediment velocity distributionsKevin Pierce and Marwan Hassan
Bed load experiments reveal a range of possibilities for the downstream velocity distributions of moving particles, including normal, exponential, and gamma distributions. Although bed load velocities are key for understanding fluctuations in transport rates, existing models have not accounted for the full range of observations. Here, we present a generalized Langevin model of particle transport that includes turbulent drag and episodic particle-bed collisions. By means of analytical calculations, we demonstrate that momentum dissipation by particle-bed collisions controls the form of the bed load velocity distribution. As collisions vary between elastic and inelastic, the velocity distribution interpolates between normal and exponential. These results add context to conflicting experiments on bed load velocities and suggest that granular interactions regulate sediment dynamics and transport rate fluctuations.
How to cite: Pierce, K. and Hassan, M.: Collisional Langevin approach to bed load sediment velocity distributions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8148, https://doi.org/10.5194/egusphere-egu21-8148, 2021.
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Bed load experiments reveal a range of possibilities for the downstream velocity distributions of moving particles, including normal, exponential, and gamma distributions. Although bed load velocities are key for understanding fluctuations in transport rates, existing models have not accounted for the full range of observations. Here, we present a generalized Langevin model of particle transport that includes turbulent drag and episodic particle-bed collisions. By means of analytical calculations, we demonstrate that momentum dissipation by particle-bed collisions controls the form of the bed load velocity distribution. As collisions vary between elastic and inelastic, the velocity distribution interpolates between normal and exponential. These results add context to conflicting experiments on bed load velocities and suggest that granular interactions regulate sediment dynamics and transport rate fluctuations.
How to cite: Pierce, K. and Hassan, M.: Collisional Langevin approach to bed load sediment velocity distributions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8148, https://doi.org/10.5194/egusphere-egu21-8148, 2021.
EGU21-4605 | vPICO presentations | GM5.4
Sediment-water flows in mountain catchments: Variability in response to high-magnitude hydrological eventsAndrea Brenna, Marco Borga, Massimiliano Ghinassi, Lorenzo Marchi, Mattia Zaramella, and Nicola Surian
Sediment transfer in mountain streams occurs by processes classified as debris flows, hyperconcentrated flows, debris floods, and water flows. One of the most important tasks in investigating floods in mountain catchments is to identify the transport mechanisms since different sediment-water flows induce peculiar geomorphological dynamics and hazards. This study aims at testing how the energy of water and the amount of sediment involved during a high-magnitude hydrological event can modify the mechanisms of sediment transfer with respect to those occurring during ordinary floods.
The selected case study is the Tegnas catchment (Dolomites, Italy), which, in October 2018, was affected by a severe hydrological event (Vaia Storm) with a recurrence interval of about 200 years. The studied catchment drains an area of 51 km2, with a range in elevation between 2872 and 620 m a.s.l.. The classification of flows that occurred during the Vaia storm was addressed at the sub-reach scale applying a field survey protocol developed to classify the flood deposits based on their sedimentological and morphological features. Following the same approach, we also determined the flow types typifying the stream network during ordinary floods. Additionally, we considered flows predicted by three morphometric approaches for high-magnitude events, and took into account the geomorphological dynamics (e.g., channel changes) and the hydraulic constraints (i.e., unit stream power) that occurred during the Vaia storm.
Water flow was the dominant process during Vaia storm in the Tegnas main steam (12 sub-reaches), although debris flow and debris flood deposits were documented at 3 and 7 sub-reaches, respectively. Water flow was observed in response to ordinary events along the entire Tegnas Torrent. Most of the steep tributaries were affected by debris flows (6 tributaries), but also debris floods were recognized at 3 steep channels. The morphometric approaches had a satisfactory performance in predicting the two end-member flows, but often failed in recognizing sub-reaches affected by debris floods.
The comparison between the occurred high-magnitude flows, and the ordinary flows allowed us to infer the existence of relationships between the transport mechanisms, the hydraulic forcing, and channel dynamics. The upheaval of the ordinary flow types did not occur along the entire stream network. The transition from water flows to debris floods occurred for unit stream powers exceeding the threshold of 5000-6000 Wm-2 or downstream of a channel delivering a large amount of sediment mobilized by debris flow to the receiving stream. The occurrence of debris floods, causing higher channel widening than water flows, appears to be facilitated by the injection of fine material into the flow, which can occur as consequence of channel-bank erosion and overbank floodwater re-entering the channel. Finally, morphometric approaches turned out to be adequate to provide a first-order discrimination of expectable high-magnitude flow types. However, the complex relationships found between flow types and a range of hydraulic, morphological, and geological controlling factors, reveal that a more detailed characterization is necessary for understanding the transport mechanisms and predicting geomorphic hazard that can affect specific channel sites during high-magnitude to extreme hydrological events.
How to cite: Brenna, A., Borga, M., Ghinassi, M., Marchi, L., Zaramella, M., and Surian, N.: Sediment-water flows in mountain catchments: Variability in response to high-magnitude hydrological events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4605, https://doi.org/10.5194/egusphere-egu21-4605, 2021.
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Sediment transfer in mountain streams occurs by processes classified as debris flows, hyperconcentrated flows, debris floods, and water flows. One of the most important tasks in investigating floods in mountain catchments is to identify the transport mechanisms since different sediment-water flows induce peculiar geomorphological dynamics and hazards. This study aims at testing how the energy of water and the amount of sediment involved during a high-magnitude hydrological event can modify the mechanisms of sediment transfer with respect to those occurring during ordinary floods.
The selected case study is the Tegnas catchment (Dolomites, Italy), which, in October 2018, was affected by a severe hydrological event (Vaia Storm) with a recurrence interval of about 200 years. The studied catchment drains an area of 51 km2, with a range in elevation between 2872 and 620 m a.s.l.. The classification of flows that occurred during the Vaia storm was addressed at the sub-reach scale applying a field survey protocol developed to classify the flood deposits based on their sedimentological and morphological features. Following the same approach, we also determined the flow types typifying the stream network during ordinary floods. Additionally, we considered flows predicted by three morphometric approaches for high-magnitude events, and took into account the geomorphological dynamics (e.g., channel changes) and the hydraulic constraints (i.e., unit stream power) that occurred during the Vaia storm.
Water flow was the dominant process during Vaia storm in the Tegnas main steam (12 sub-reaches), although debris flow and debris flood deposits were documented at 3 and 7 sub-reaches, respectively. Water flow was observed in response to ordinary events along the entire Tegnas Torrent. Most of the steep tributaries were affected by debris flows (6 tributaries), but also debris floods were recognized at 3 steep channels. The morphometric approaches had a satisfactory performance in predicting the two end-member flows, but often failed in recognizing sub-reaches affected by debris floods.
The comparison between the occurred high-magnitude flows, and the ordinary flows allowed us to infer the existence of relationships between the transport mechanisms, the hydraulic forcing, and channel dynamics. The upheaval of the ordinary flow types did not occur along the entire stream network. The transition from water flows to debris floods occurred for unit stream powers exceeding the threshold of 5000-6000 Wm-2 or downstream of a channel delivering a large amount of sediment mobilized by debris flow to the receiving stream. The occurrence of debris floods, causing higher channel widening than water flows, appears to be facilitated by the injection of fine material into the flow, which can occur as consequence of channel-bank erosion and overbank floodwater re-entering the channel. Finally, morphometric approaches turned out to be adequate to provide a first-order discrimination of expectable high-magnitude flow types. However, the complex relationships found between flow types and a range of hydraulic, morphological, and geological controlling factors, reveal that a more detailed characterization is necessary for understanding the transport mechanisms and predicting geomorphic hazard that can affect specific channel sites during high-magnitude to extreme hydrological events.
How to cite: Brenna, A., Borga, M., Ghinassi, M., Marchi, L., Zaramella, M., and Surian, N.: Sediment-water flows in mountain catchments: Variability in response to high-magnitude hydrological events, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4605, https://doi.org/10.5194/egusphere-egu21-4605, 2021.
EGU21-1795 | vPICO presentations | GM5.4
A new geo-sensing system to monitor seepage effects at transportation infrastructureManousos Valyrakis, Panagiotis Michalis, and Eftychia Koursari
Real-time condition assessment of transportation systems is critical considering these have been constructed over the past decades with now outdated designs and in the majority of the cases without taking into account the current climatic variability. One of the most vulnerable elements of these infrastructure systems are embankments and geo-structures near water bodies, as flowing water typically has a degradating impact on their performance. Water-related hazards can increase seepage effects which can be the main cause for their structural failure. Floods can also accelerate internal seepage processes occurring inside the body of geo-structures, due to a combined effect of the high permeability of soil and increased hydrostatic pressure, worsening the risks of catastrophic failures [1].
The difficulty in detecting seepage processes inside the body of geo-infrastructure with conventional methods leads to irreversible effects with major disruption and costs to road asset owners, maintainers and users. The need to obtain real-time information about the evolution of geomorphological hazards is therefore considered to be of significant importance considering the ageing infrastructure, constructed near geomorphologically active rivers, and the extreme shifting climatic conditions [2].
This study presents the development of a new sensing system aiming to provide advanced information about seepage processes inside the body of geo-structures. The main principles around the sensor's operation are presented alongside with implementation and installation procedures for optimum application. Finally guidelines about their efficient incorporation into existing sensing and management platforms are provided. The proposed sensing system is expected to enhance the response capabilities of asset owners providing advanced warnings about the condition of infrastructure, increasing commutters' safety and resilience of transportation systems to climatic hazards.
References
[1] Michalis, P., Sentenac, P. and Macbrayne, D. (2016). Geophysical assessment of dam infrastructure: The Mugdock reservoir dam case study. Proceedings of the 3rd Joint International Symposium on DeformationMonitoring (JISDM), Vienna, Austria, 30 March–1 April, pp.1-6.
[2] Michalis, P. Xu., Y. and Valyrakis M. (2020). Current practices and future directions of monitoring systems for the assessment of geomorphological conditions atbridge infrastructure. River Flow 2020. Proceedings of the 10th Conference on Fluvial Hydraulics, Delft, Netherlands, 7-10 July. pp. 1-6.
How to cite: Valyrakis, M., Michalis, P., and Koursari, E.: A new geo-sensing system to monitor seepage effects at transportation infrastructure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1795, https://doi.org/10.5194/egusphere-egu21-1795, 2021.
Real-time condition assessment of transportation systems is critical considering these have been constructed over the past decades with now outdated designs and in the majority of the cases without taking into account the current climatic variability. One of the most vulnerable elements of these infrastructure systems are embankments and geo-structures near water bodies, as flowing water typically has a degradating impact on their performance. Water-related hazards can increase seepage effects which can be the main cause for their structural failure. Floods can also accelerate internal seepage processes occurring inside the body of geo-structures, due to a combined effect of the high permeability of soil and increased hydrostatic pressure, worsening the risks of catastrophic failures [1].
The difficulty in detecting seepage processes inside the body of geo-infrastructure with conventional methods leads to irreversible effects with major disruption and costs to road asset owners, maintainers and users. The need to obtain real-time information about the evolution of geomorphological hazards is therefore considered to be of significant importance considering the ageing infrastructure, constructed near geomorphologically active rivers, and the extreme shifting climatic conditions [2].
This study presents the development of a new sensing system aiming to provide advanced information about seepage processes inside the body of geo-structures. The main principles around the sensor's operation are presented alongside with implementation and installation procedures for optimum application. Finally guidelines about their efficient incorporation into existing sensing and management platforms are provided. The proposed sensing system is expected to enhance the response capabilities of asset owners providing advanced warnings about the condition of infrastructure, increasing commutters' safety and resilience of transportation systems to climatic hazards.
References
[1] Michalis, P., Sentenac, P. and Macbrayne, D. (2016). Geophysical assessment of dam infrastructure: The Mugdock reservoir dam case study. Proceedings of the 3rd Joint International Symposium on DeformationMonitoring (JISDM), Vienna, Austria, 30 March–1 April, pp.1-6.
[2] Michalis, P. Xu., Y. and Valyrakis M. (2020). Current practices and future directions of monitoring systems for the assessment of geomorphological conditions atbridge infrastructure. River Flow 2020. Proceedings of the 10th Conference on Fluvial Hydraulics, Delft, Netherlands, 7-10 July. pp. 1-6.
How to cite: Valyrakis, M., Michalis, P., and Koursari, E.: A new geo-sensing system to monitor seepage effects at transportation infrastructure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1795, https://doi.org/10.5194/egusphere-egu21-1795, 2021.
EGU21-3325 | vPICO presentations | GM5.4
Assessing thresholds for fluvial entrainment with instrumented particlesKhaldoon AlObaidi and Manousos Valyrakis
Sediment transport is considered to be the governing process in many applications around the fields of geosciences and engineering as well as infrastructure and environment monitoring. Of a special interest to which scientists and engineers have dedicated a lot of time and experimental studies in the last century is the conditions for initiation of sediment entrainment, or incipient motion. In the literature, there are different criteria for determining the conditions that can result in initiation of sediment entrainment. Among these criteria, the impulse (or energy) criterion [1-2] captures the actual physics of sediment entrainment since it accounts for both the magnitude and the duration of the turbulent flow events that can result in initiation of a particle’s motion. The experimental and field studies of incipient motion use relatively expensive tools, like Particle image velocimetry (PIV) or Acoustic Doppler velocimetry (ADV), with indirect methods to determine flow parameters that could be related to predicting sediment entrainment. However, technological developments in recent decades has made it possible to assess sediment entrainment directly. Recently, a number of research studies [3-4] have suggested linking micro-electromechanical system (MEMS) recordings that consist of accelerometers, gyroscopes and magnetometer as well as an internal digital motion processor that are interconnected forming inertial measurement units (IMUs) to the probability of entrainment of individual particles. The particles have been presented provide a direct, non-intrusive, low-cost and accessible method for assessing the probability of entrainment of individual sediment particles rather than inferred using near bed flow diagnostics. In this work, an instrumented particle of 3cm in diameter [5] is used to investigate experimentally the conditions that can result in initiation of sediment entrainment for a range of flowrates that represent the near threshold conditions. The data is used to derive metrics like frequency of entrainment that could be linked to the probability of entrainment of individual sediment particles which could be used as an indicator of the risk of riverbed destabilization based on well-established theories in hydraulic engineering. Additionally, the novelty of this work is explicitly linking the probability of entrainment to the flow hydrodynamics. In addition to that, a stochastic analysis is performed to identify the relevance of certain flow structures (sweeps) to the incipient entrainment of the instrumented particle.
[1] Valyrakis M., Diplas P., Dancey C.L., Greer K., Celik A.O. (2010). Role of Instantaneous Force Magnitude and Duration on Particle Entrainment. JGR, 115, 1-18.
[2] Valyrakis M., Diplas P., Dancey C.L. (2013). Entrainment of Coarse Particles in Turbulent Flows: An Energy Approach. JGR- Earth Surf., 118, 42-53.
[3] Valyrakis, M., Alexakis, A. (2016). Development of a “smart-pebble” for tracking sediment transport. River Flow 2016, MO, USA.
[4] Al-Obaidi, K., Xu, Y., Valyrakis, M. (2020). The Design and Calibration of Instrumented Particles for Assessing Water Infrastructure Hazards. JSAN, 9, 3, 36.
[5] Al-Obaidi, K., Valyrakis, M. (2020). A sensory instrumented particle for environmental monitoring applications: development and calibration. IEEE sensors journal (accepted).
How to cite: AlObaidi, K. and Valyrakis, M.: Assessing thresholds for fluvial entrainment with instrumented particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3325, https://doi.org/10.5194/egusphere-egu21-3325, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Sediment transport is considered to be the governing process in many applications around the fields of geosciences and engineering as well as infrastructure and environment monitoring. Of a special interest to which scientists and engineers have dedicated a lot of time and experimental studies in the last century is the conditions for initiation of sediment entrainment, or incipient motion. In the literature, there are different criteria for determining the conditions that can result in initiation of sediment entrainment. Among these criteria, the impulse (or energy) criterion [1-2] captures the actual physics of sediment entrainment since it accounts for both the magnitude and the duration of the turbulent flow events that can result in initiation of a particle’s motion. The experimental and field studies of incipient motion use relatively expensive tools, like Particle image velocimetry (PIV) or Acoustic Doppler velocimetry (ADV), with indirect methods to determine flow parameters that could be related to predicting sediment entrainment. However, technological developments in recent decades has made it possible to assess sediment entrainment directly. Recently, a number of research studies [3-4] have suggested linking micro-electromechanical system (MEMS) recordings that consist of accelerometers, gyroscopes and magnetometer as well as an internal digital motion processor that are interconnected forming inertial measurement units (IMUs) to the probability of entrainment of individual particles. The particles have been presented provide a direct, non-intrusive, low-cost and accessible method for assessing the probability of entrainment of individual sediment particles rather than inferred using near bed flow diagnostics. In this work, an instrumented particle of 3cm in diameter [5] is used to investigate experimentally the conditions that can result in initiation of sediment entrainment for a range of flowrates that represent the near threshold conditions. The data is used to derive metrics like frequency of entrainment that could be linked to the probability of entrainment of individual sediment particles which could be used as an indicator of the risk of riverbed destabilization based on well-established theories in hydraulic engineering. Additionally, the novelty of this work is explicitly linking the probability of entrainment to the flow hydrodynamics. In addition to that, a stochastic analysis is performed to identify the relevance of certain flow structures (sweeps) to the incipient entrainment of the instrumented particle.
[1] Valyrakis M., Diplas P., Dancey C.L., Greer K., Celik A.O. (2010). Role of Instantaneous Force Magnitude and Duration on Particle Entrainment. JGR, 115, 1-18.
[2] Valyrakis M., Diplas P., Dancey C.L. (2013). Entrainment of Coarse Particles in Turbulent Flows: An Energy Approach. JGR- Earth Surf., 118, 42-53.
[3] Valyrakis, M., Alexakis, A. (2016). Development of a “smart-pebble” for tracking sediment transport. River Flow 2016, MO, USA.
[4] Al-Obaidi, K., Xu, Y., Valyrakis, M. (2020). The Design and Calibration of Instrumented Particles for Assessing Water Infrastructure Hazards. JSAN, 9, 3, 36.
[5] Al-Obaidi, K., Valyrakis, M. (2020). A sensory instrumented particle for environmental monitoring applications: development and calibration. IEEE sensors journal (accepted).
How to cite: AlObaidi, K. and Valyrakis, M.: Assessing thresholds for fluvial entrainment with instrumented particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3325, https://doi.org/10.5194/egusphere-egu21-3325, 2021.
EGU21-9574 | vPICO presentations | GM5.4
Characterization of windblown sand transport in open field conditions through wind-sand tunnel testing and computational simulationLorenzo Raffaele, Nicolas Coste, Andrea Lo Giudice, Gertjan Glabeke, and Jeroen van Beeck
Aeolian sediment transport in desert and sandy coastal environments affects civil structures and infrastructures, such as pipelines, industrial facilities, towns, single buildings, farms, roads, and railways [1]. The wind flow interacts with surface-mounted obstacles of any kind inducing sand erosion, transport, and sedimentation around them. This can lead to detrimental effects such as the loss of functionality of the endangered structure or infrastructure, or even danger for users when structural failure is involved [2]. In order to cope with the effects above, the demand for the characterization of aeolian sand transport and the design of Sand Mitigation Measures (SMMs) has grown in the last decade and is expected to further increase in the next years [1]. The multiphase and multiscale nature of the aeolian flow ranging from the sand grain diameters to the obstacle characteristic lengths make the problem only tractable by means of physical experiments and computational simulations. On the one hand, in-situ full scale field tests are expensive, time-consuming, and subject to environmental setup conditions difficult to control. On the other hand, numerical models shall be carefully validated against physical experiments. Hence, experimental Wind-Sand Tunnel Tests (WSTTs) are often carried out.
In this study, windblown sand transport on flat ground is reproduced by means of WSTTs carried out in the wind tunnel L-1B of von Karman Institute for Fluid Dynamics. The aim of WSTTs is twofold. On one hand, they are intended to characterize the incoming sand flux in open field conditions. On the other hand, they allow to properly tune cheaper Wind-Sand Computational Simulations [3], so as to assess the performance of SMMs in full-scale. The wind tunnel setup implements a uniform 5-meter-long sand fetch as sand source. The wind speed boundary layer and sand flux saltation layer are characterized through 2D Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) techniques, respectively. Wind flow and sand transport state variables are assessed along the sand fetch by setting the wind speed equal to 1.3, 1.5, 2 times the threshold one, and by assessing the influence of a monoplane grid installed at the inlet of the wind tunnel testing sections. Results from WSTTs are critically discussed by investigating the effects induced by the sand fetch length, wind speed, and turbulence intensity on the sand transport. Finally, a Eulerian multiphase computational fluid dynamics model is tuned in order to reproduce the obtained results.
References
[1] Bruno L, Horvat M, Raffaele L. Windblown sand along railway infrastructures: a review of challenges and mitigation measures. J Wind Eng Ind Aerodynam 2018;177:340–65.
[2] Raffaele L, Bruno L. Windblown sand action on civil structures: Definition and probabilistic modelling. Eng Struct 2019;178:88-101.
[3] Lo Giudice A, Preziosi L. A fully Eulerian multiphase model of windblown sand coupled with morphodynamic evolution: Erosion, transport, deposition, and avalanching. Appl Math Model 2020;79:68-84.
How to cite: Raffaele, L., Coste, N., Lo Giudice, A., Glabeke, G., and van Beeck, J.: Characterization of windblown sand transport in open field conditions through wind-sand tunnel testing and computational simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9574, https://doi.org/10.5194/egusphere-egu21-9574, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Aeolian sediment transport in desert and sandy coastal environments affects civil structures and infrastructures, such as pipelines, industrial facilities, towns, single buildings, farms, roads, and railways [1]. The wind flow interacts with surface-mounted obstacles of any kind inducing sand erosion, transport, and sedimentation around them. This can lead to detrimental effects such as the loss of functionality of the endangered structure or infrastructure, or even danger for users when structural failure is involved [2]. In order to cope with the effects above, the demand for the characterization of aeolian sand transport and the design of Sand Mitigation Measures (SMMs) has grown in the last decade and is expected to further increase in the next years [1]. The multiphase and multiscale nature of the aeolian flow ranging from the sand grain diameters to the obstacle characteristic lengths make the problem only tractable by means of physical experiments and computational simulations. On the one hand, in-situ full scale field tests are expensive, time-consuming, and subject to environmental setup conditions difficult to control. On the other hand, numerical models shall be carefully validated against physical experiments. Hence, experimental Wind-Sand Tunnel Tests (WSTTs) are often carried out.
In this study, windblown sand transport on flat ground is reproduced by means of WSTTs carried out in the wind tunnel L-1B of von Karman Institute for Fluid Dynamics. The aim of WSTTs is twofold. On one hand, they are intended to characterize the incoming sand flux in open field conditions. On the other hand, they allow to properly tune cheaper Wind-Sand Computational Simulations [3], so as to assess the performance of SMMs in full-scale. The wind tunnel setup implements a uniform 5-meter-long sand fetch as sand source. The wind speed boundary layer and sand flux saltation layer are characterized through 2D Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV) techniques, respectively. Wind flow and sand transport state variables are assessed along the sand fetch by setting the wind speed equal to 1.3, 1.5, 2 times the threshold one, and by assessing the influence of a monoplane grid installed at the inlet of the wind tunnel testing sections. Results from WSTTs are critically discussed by investigating the effects induced by the sand fetch length, wind speed, and turbulence intensity on the sand transport. Finally, a Eulerian multiphase computational fluid dynamics model is tuned in order to reproduce the obtained results.
References
[1] Bruno L, Horvat M, Raffaele L. Windblown sand along railway infrastructures: a review of challenges and mitigation measures. J Wind Eng Ind Aerodynam 2018;177:340–65.
[2] Raffaele L, Bruno L. Windblown sand action on civil structures: Definition and probabilistic modelling. Eng Struct 2019;178:88-101.
[3] Lo Giudice A, Preziosi L. A fully Eulerian multiphase model of windblown sand coupled with morphodynamic evolution: Erosion, transport, deposition, and avalanching. Appl Math Model 2020;79:68-84.
How to cite: Raffaele, L., Coste, N., Lo Giudice, A., Glabeke, G., and van Beeck, J.: Characterization of windblown sand transport in open field conditions through wind-sand tunnel testing and computational simulation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9574, https://doi.org/10.5194/egusphere-egu21-9574, 2021.
EGU21-1589 | vPICO presentations | GM5.4
Digital Transformation of Critical Water InfrastructureFotios Konstantinidis, Panagiotis Michalis, and Manousos Valyrakis
The ongoing fourth industrial revolution has accelerated the transformation of management and maintenance of assets into the digital era. This involves the application and interoperability of management systems in an upper system like the one described as Civil Infrastructure 4.0 [1]. CI4.0 involves the collection and process of data from the surrounding infrastructure over a wide range of assets and systems, incorporating a multi-integrated decision support system for efficient asset management. This is particular important for ageing water infrastructure as it is threatened by the occurrence of flood-related hazards, which have significant degradation impact and consequences to transport systems, e.g. bridges, embankments, waterways etc.
Despite the recent advances in the development and application of immersive technologies, transport and water infrastructure are still considered to be managed in a traditional way. This process involves on-site engineers making decisions based on their skills and experience, while in the majority of the times using paper-based analytics.
This study presents the development of intelligent tools to efficiently advance decision making about the maintenance procedure of water infrastructure, aiming to reduce costs and assessment times. One of the technological pillars, which can upgrade the traditional procedures is Augmented Reality (AR) technology, which is already used in other industries like Manufacturing and Automotive [2]. AR creates a combined environment in which the views of real and virtual worlds co-exist. AR technology provides valuable key information to inspectors, through AR glasses or mobile devices, pointing out areas of interest. Such an AR solution can register the coordination of location of the defects, analysing the possible maintenance solutions, and communicating effectively between in-house operators and inspectors on-site.
[1] Michalis, P., Konstantinidis, F. and Valyrakis, M. (2019). The road towards Civil Infrastructure 4.0 for proactive asset management of critical infrastructure systems. Proceedings of the 2nd International Conference on Natural Hazards & Infrastructure (ICONHIC), 23–26 June Chania, Greece, pp. 1-9.
[2] Konstantinidis, F.K., Kansizoglou, I., Santavas, N., Mouroutsos, S.G. and Gasteratos, A., 2020. MARMA: A Mobile Augmented Reality Maintenance Assistant for Fast-Track Repair Procedures in the Context of Industry 4.0. Machines, 8(4), p.88.
How to cite: Konstantinidis, F., Michalis, P., and Valyrakis, M.: Digital Transformation of Critical Water Infrastructure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1589, https://doi.org/10.5194/egusphere-egu21-1589, 2021.
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The ongoing fourth industrial revolution has accelerated the transformation of management and maintenance of assets into the digital era. This involves the application and interoperability of management systems in an upper system like the one described as Civil Infrastructure 4.0 [1]. CI4.0 involves the collection and process of data from the surrounding infrastructure over a wide range of assets and systems, incorporating a multi-integrated decision support system for efficient asset management. This is particular important for ageing water infrastructure as it is threatened by the occurrence of flood-related hazards, which have significant degradation impact and consequences to transport systems, e.g. bridges, embankments, waterways etc.
Despite the recent advances in the development and application of immersive technologies, transport and water infrastructure are still considered to be managed in a traditional way. This process involves on-site engineers making decisions based on their skills and experience, while in the majority of the times using paper-based analytics.
This study presents the development of intelligent tools to efficiently advance decision making about the maintenance procedure of water infrastructure, aiming to reduce costs and assessment times. One of the technological pillars, which can upgrade the traditional procedures is Augmented Reality (AR) technology, which is already used in other industries like Manufacturing and Automotive [2]. AR creates a combined environment in which the views of real and virtual worlds co-exist. AR technology provides valuable key information to inspectors, through AR glasses or mobile devices, pointing out areas of interest. Such an AR solution can register the coordination of location of the defects, analysing the possible maintenance solutions, and communicating effectively between in-house operators and inspectors on-site.
[1] Michalis, P., Konstantinidis, F. and Valyrakis, M. (2019). The road towards Civil Infrastructure 4.0 for proactive asset management of critical infrastructure systems. Proceedings of the 2nd International Conference on Natural Hazards & Infrastructure (ICONHIC), 23–26 June Chania, Greece, pp. 1-9.
[2] Konstantinidis, F.K., Kansizoglou, I., Santavas, N., Mouroutsos, S.G. and Gasteratos, A., 2020. MARMA: A Mobile Augmented Reality Maintenance Assistant for Fast-Track Repair Procedures in the Context of Industry 4.0. Machines, 8(4), p.88.
How to cite: Konstantinidis, F., Michalis, P., and Valyrakis, M.: Digital Transformation of Critical Water Infrastructure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1589, https://doi.org/10.5194/egusphere-egu21-1589, 2021.
EGU21-10880 | vPICO presentations | GM5.4 | Highlight
Impact of river weirs on bedload dynamics in low to medium energy riversVincent Tamisier, Frédéric Gob, Emmanuèle Gautier, Geoffrey Houbrechts, and Thomas Dépret
Assessing the impact of weirs in low- to medium-energy rivers, especially their influence on the bedload continuity, is an important issue for the understanding and management of river hydrosystems. The implementation of European regulations has for example led to an increasing number of restoration projects involving the total or partial dismantling of weirs. The effect of weirs on sedimentary continuity is beginning to be studied but remains poorly understood. In this study we present the results of monitoring over three hydrological seasons of 900 particles equipped with PIT tags set up around two weirs on the Rognon river (France) and the Amblève river (Belgium). For the two sites studied, and while floods were relatively frequent (max 5 return-interval years for the Rognon River and 2 return-interval years for the Amblève River), nearly 80% of the tagged particles positioned just upstream of the weirs were exported downstream of them during the study period. However, the tagged particles in the control reaches, non-influenced by weirs, travelled distances 2 to 2.5 times greater than the particles injected in the impoundment. Mobilisation rates are also significantly higher in the control reaches. Whereas the size of the mobilised particles (D50, D90) is similar between the impoundment and the control reaches in the Amblève river, mobilised particles are significantly smaller in the impoundment reach in the Rognon river. This data indicates that these weirs can have a significant effect by slowing down the bed load velocity, especially its coarsest part. Nevertheless, in the current weir operating, weirs do not interrupt the bedload continuity. This type of structure does not seem to constitute a real obstacle to sedimentary continuity and the question of their dismantling may be raised in view of the potential impacts they could have on the other components of ecological continuity.
How to cite: Tamisier, V., Gob, F., Gautier, E., Houbrechts, G., and Dépret, T.: Impact of river weirs on bedload dynamics in low to medium energy rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10880, https://doi.org/10.5194/egusphere-egu21-10880, 2021.
Assessing the impact of weirs in low- to medium-energy rivers, especially their influence on the bedload continuity, is an important issue for the understanding and management of river hydrosystems. The implementation of European regulations has for example led to an increasing number of restoration projects involving the total or partial dismantling of weirs. The effect of weirs on sedimentary continuity is beginning to be studied but remains poorly understood. In this study we present the results of monitoring over three hydrological seasons of 900 particles equipped with PIT tags set up around two weirs on the Rognon river (France) and the Amblève river (Belgium). For the two sites studied, and while floods were relatively frequent (max 5 return-interval years for the Rognon River and 2 return-interval years for the Amblève River), nearly 80% of the tagged particles positioned just upstream of the weirs were exported downstream of them during the study period. However, the tagged particles in the control reaches, non-influenced by weirs, travelled distances 2 to 2.5 times greater than the particles injected in the impoundment. Mobilisation rates are also significantly higher in the control reaches. Whereas the size of the mobilised particles (D50, D90) is similar between the impoundment and the control reaches in the Amblève river, mobilised particles are significantly smaller in the impoundment reach in the Rognon river. This data indicates that these weirs can have a significant effect by slowing down the bed load velocity, especially its coarsest part. Nevertheless, in the current weir operating, weirs do not interrupt the bedload continuity. This type of structure does not seem to constitute a real obstacle to sedimentary continuity and the question of their dismantling may be raised in view of the potential impacts they could have on the other components of ecological continuity.
How to cite: Tamisier, V., Gob, F., Gautier, E., Houbrechts, G., and Dépret, T.: Impact of river weirs on bedload dynamics in low to medium energy rivers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10880, https://doi.org/10.5194/egusphere-egu21-10880, 2021.
EGU21-13093 | vPICO presentations | GM5.4
Experiments on the grain size gap across gravel-sand transitionsElizabeth Dingle and Jeremy Venditti
An abrupt transition in river bed grain size occurs from gravel to sand over a short downstream distance, often only a few channel widths, and is termed the gravel-sand transition (GST). At this point, the bed structure also changes from framework- to matrix-supported. Whether the GST is externally imposed, a result of internal dynamics (sediment sorting, abrasion, suspension deposition) or due to some other emergent property is unclear. There is also a general absence of rivers beds with median surface grain sizes between ~1 and 5 mm, often referred to as the grain size gap. Here we present two sets of new laboratory experiments, examining changes in fluid and sediment dynamics across the GST. In the first set, we created stable GSTs with a 10 mm gravel and 0.5 mm sand that show GST formation is consistent with previous theory suggesting that at shear velocities of ~0.1 m/s, sand particles rapidly fall out of suspension as a result of a particle Reynolds number dependency (i.e. a viscous effect). In a second set of experiments, we explored the fate of grain size gap material. We formed a gravel wedge composed of ~2 to 5 mm sediment, then fed 0.5 mm sand. Our observations indicate that where sand rapidly starts to fall out of suspension, the gravel bed becomes inherently unstable. Gravel is transported downstream until the grain size gap material is largely exhausted from the system (e.g. buried under sand or rafted out of the flume). This occurs because sand sized particles fill or bridge interstitial pockets in the fine gravel bed surface, generating fluid acceleration in the near-bed region (i.e. a geometric effect specific to these grain sizes). As such, particles in the grain size gap do not form the dominant mode in river bed sediments.
How to cite: Dingle, E. and Venditti, J.: Experiments on the grain size gap across gravel-sand transitions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13093, https://doi.org/10.5194/egusphere-egu21-13093, 2021.
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An abrupt transition in river bed grain size occurs from gravel to sand over a short downstream distance, often only a few channel widths, and is termed the gravel-sand transition (GST). At this point, the bed structure also changes from framework- to matrix-supported. Whether the GST is externally imposed, a result of internal dynamics (sediment sorting, abrasion, suspension deposition) or due to some other emergent property is unclear. There is also a general absence of rivers beds with median surface grain sizes between ~1 and 5 mm, often referred to as the grain size gap. Here we present two sets of new laboratory experiments, examining changes in fluid and sediment dynamics across the GST. In the first set, we created stable GSTs with a 10 mm gravel and 0.5 mm sand that show GST formation is consistent with previous theory suggesting that at shear velocities of ~0.1 m/s, sand particles rapidly fall out of suspension as a result of a particle Reynolds number dependency (i.e. a viscous effect). In a second set of experiments, we explored the fate of grain size gap material. We formed a gravel wedge composed of ~2 to 5 mm sediment, then fed 0.5 mm sand. Our observations indicate that where sand rapidly starts to fall out of suspension, the gravel bed becomes inherently unstable. Gravel is transported downstream until the grain size gap material is largely exhausted from the system (e.g. buried under sand or rafted out of the flume). This occurs because sand sized particles fill or bridge interstitial pockets in the fine gravel bed surface, generating fluid acceleration in the near-bed region (i.e. a geometric effect specific to these grain sizes). As such, particles in the grain size gap do not form the dominant mode in river bed sediments.
How to cite: Dingle, E. and Venditti, J.: Experiments on the grain size gap across gravel-sand transitions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13093, https://doi.org/10.5194/egusphere-egu21-13093, 2021.
EGU21-13221 | vPICO presentations | GM5.4
Investigation on hydrodynamic forces leading to coarse particle entrainment using Large-Eddy SimulationsGaston Latessa, Angela Busse, and Manousos Valyrakis
The prediction of particle motion in a fluid flow environment presents several challenges from the quantification of the forces exerted by the fluid onto the solids -normally with fluctuating behaviour due to turbulence- and the definition of the potential particle entrainment from these actions. An accurate description of these phenomena has many practical applications in local scour definition and to the design of protection measures.
In the present work, the actions of different flow conditions on sediment particles is investigated with the aim to translate these effects into particle entrainment identification through analytical solid dynamic equations.
Large Eddy Simulations (LES) are an increasingly practical tool that provide an accurate representation of both the mean flow field and the large-scale turbulent fluctuations. For the present case, the forces exerted by the flow are integrated over the surface of a stationary particle in the streamwise (drag) and vertical (lift) directions, together with the torques around the particle’s centre of mass. These forces are validated against experimental data under the same bed and flow conditions.
The forces are then compared against threshold values, obtained through theoretical equations of simple motions such as rolling without sliding. Thus, the frequency of entrainment is related to the different flow conditions in good agreement with results from experimental sediment entrainment research.
A thorough monitoring of the velocity flow field on several locations is carried out to determine the relationships between velocity time series at several locations around the particle and the forces acting on its surface. These results a relevant to determine ideal locations for flow investigation both in numerical and physical experiments.
Through numerical experiments, a large number of flow conditions were simulated obtaining a full set of actions over a fixed particle sitting on a smooth bed. These actions were translated into potential particle entrainment events and validated against experimental data. Future work will present the coupling of these LES models with Discrete Element Method (DEM) models to verify the entrainment phenomena entirely from a numerical perspective.
How to cite: Latessa, G., Busse, A., and Valyrakis, M.: Investigation on hydrodynamic forces leading to coarse particle entrainment using Large-Eddy Simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13221, https://doi.org/10.5194/egusphere-egu21-13221, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The prediction of particle motion in a fluid flow environment presents several challenges from the quantification of the forces exerted by the fluid onto the solids -normally with fluctuating behaviour due to turbulence- and the definition of the potential particle entrainment from these actions. An accurate description of these phenomena has many practical applications in local scour definition and to the design of protection measures.
In the present work, the actions of different flow conditions on sediment particles is investigated with the aim to translate these effects into particle entrainment identification through analytical solid dynamic equations.
Large Eddy Simulations (LES) are an increasingly practical tool that provide an accurate representation of both the mean flow field and the large-scale turbulent fluctuations. For the present case, the forces exerted by the flow are integrated over the surface of a stationary particle in the streamwise (drag) and vertical (lift) directions, together with the torques around the particle’s centre of mass. These forces are validated against experimental data under the same bed and flow conditions.
The forces are then compared against threshold values, obtained through theoretical equations of simple motions such as rolling without sliding. Thus, the frequency of entrainment is related to the different flow conditions in good agreement with results from experimental sediment entrainment research.
A thorough monitoring of the velocity flow field on several locations is carried out to determine the relationships between velocity time series at several locations around the particle and the forces acting on its surface. These results a relevant to determine ideal locations for flow investigation both in numerical and physical experiments.
Through numerical experiments, a large number of flow conditions were simulated obtaining a full set of actions over a fixed particle sitting on a smooth bed. These actions were translated into potential particle entrainment events and validated against experimental data. Future work will present the coupling of these LES models with Discrete Element Method (DEM) models to verify the entrainment phenomena entirely from a numerical perspective.
How to cite: Latessa, G., Busse, A., and Valyrakis, M.: Investigation on hydrodynamic forces leading to coarse particle entrainment using Large-Eddy Simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13221, https://doi.org/10.5194/egusphere-egu21-13221, 2021.
EGU21-15791 | vPICO presentations | GM5.4
A Preliminary Assessment of Low-Cost Bridge Scour Monitoring Methods and ToolsEftychia Koursari, Stuart Wallace, Panagiotis Michalis, Manousos Valyrakis, and Scott Paton
Scour is a major cause of bridge collapse worldwide.
Climate change has resulted in flood events increasing both in frequency and in magnitude. Climate change, together with the current uncertainty about maximum scour depth around structures, make scour and other hydraulic actions some of the most important challenges for engineering going forward.
This study offers a preliminary assessment of bridge scour monitoring methods considering scour as a dynamical earth surface shaping process, and discusses how these methods can be used to improve predictive models for bridge scour depth.
Current methods used to monitor scour are mostly reactive. A vast amount of research has been carried out, aiming towards the implementation of various approaches to assist in the monitoring of scour; however, most methods used are either still reactive, or extremely costly and therefore not practical to be used for small to medium scale structures. This study aims in addressing major challenges faced by establishing a new, innovative framework for the monitoring of scour, while considering relevant approaches in literature. It discusses the development of an innovative, sustainable and low-cost framework, that can be used for small to medium scale structures. This will ensure a proactive response in the event of catastrophic scour occurring, safeguarding infrastructure and the travelling public.
How to cite: Koursari, E., Wallace, S., Michalis, P., Valyrakis, M., and Paton, S.: A Preliminary Assessment of Low-Cost Bridge Scour Monitoring Methods and Tools, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15791, https://doi.org/10.5194/egusphere-egu21-15791, 2021.
Scour is a major cause of bridge collapse worldwide.
Climate change has resulted in flood events increasing both in frequency and in magnitude. Climate change, together with the current uncertainty about maximum scour depth around structures, make scour and other hydraulic actions some of the most important challenges for engineering going forward.
This study offers a preliminary assessment of bridge scour monitoring methods considering scour as a dynamical earth surface shaping process, and discusses how these methods can be used to improve predictive models for bridge scour depth.
Current methods used to monitor scour are mostly reactive. A vast amount of research has been carried out, aiming towards the implementation of various approaches to assist in the monitoring of scour; however, most methods used are either still reactive, or extremely costly and therefore not practical to be used for small to medium scale structures. This study aims in addressing major challenges faced by establishing a new, innovative framework for the monitoring of scour, while considering relevant approaches in literature. It discusses the development of an innovative, sustainable and low-cost framework, that can be used for small to medium scale structures. This will ensure a proactive response in the event of catastrophic scour occurring, safeguarding infrastructure and the travelling public.
How to cite: Koursari, E., Wallace, S., Michalis, P., Valyrakis, M., and Paton, S.: A Preliminary Assessment of Low-Cost Bridge Scour Monitoring Methods and Tools, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15791, https://doi.org/10.5194/egusphere-egu21-15791, 2021.
EGU21-1652 | vPICO presentations | GM5.4
A New Structural Health Monitoring System to Assess Bridge ScourPanagiotis Michalis, Manousos Valyrakis, and Elissavet Vintzilaiou
Scour action still remains the leading cause of numerous bridge failures each year and is considered one of the most destructive flood related hazards occurring around underwater foundation elements [1]. Undetected erosion related processes are therefore the cause of major disruptions to the transportation network with significant socio-economic losses and disruption to users, maintainers and asset owners. Recent cases of bridge failures due to extreme climatic events have highlighted the need for a reliable scour monitoring and early warning system to assess flood and geo-related hazards in real-time, providing advanced key info for repair and maintenance actions. Despite the past efforts to provide such a system for scour assessment, most of these instruments have not managed to realise a solution for scour monitoring due to technical and cost issues. The existing practices to assess, manage and maintain transportation assets are mainly based on visual inspection procedure which is also considered to be insufficient [2]. As a result there currently exists a gap in the knowledge and understanding of scour mechanism during flood incidents.
This study presents the architecture of ‘Climatic Hazard Monitoring and Bridge Scour Early Warning System’ (CliHaMoS) project, which is expected to significantly assist towards the optimisation of bridge performance against scour issues with a real-time data driven approach. CliHaMoS platform comprises of a new structural health monitoring system based on a novel bio-inspired sensing system aiming to deliver key information under different hydrodynamic events for real-time and forecasted assessment of flood hazards at bridges. The sensing solution is coupled by an early warning system, with advanced interoperability characteristics, to provide a holistic interactive platform and ensure that risks associated with flood hazards are properly and timely communicated to end-users. The obtained information is expected to enable stakeholders to plan adaptation strategies and proactively manage and maintain transportation infrastructure.
[1] Michalis, P., Saafi, M., and Judd. M. (2013) Capacitive sensors for offshore scour monitoring. Proceedings of the ICE – Energy, 166 (4), pp. 189-197
[2] Michalis, P., Saafi, M. and Judd, M. (2012) Wireless sensor networks for surveillance and monitoring of bridge scour. Proceedings of the XI International Conference Protection and Restoration of the Environment - PRE XI. Thessaloniki, Greece, pp. 1345–1354.
ACKNOWLEDGMENT:
This research is co-financed by Greece and the European Union (European Social FundESF) through the Operational Programme «Human Resources Development, Education and 4 Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” (MIS-5033021), implemented by the State Scholarships Foundation (ΙΚΥ).
How to cite: Michalis, P., Valyrakis, M., and Vintzilaiou, E.: A New Structural Health Monitoring System to Assess Bridge Scour, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1652, https://doi.org/10.5194/egusphere-egu21-1652, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Scour action still remains the leading cause of numerous bridge failures each year and is considered one of the most destructive flood related hazards occurring around underwater foundation elements [1]. Undetected erosion related processes are therefore the cause of major disruptions to the transportation network with significant socio-economic losses and disruption to users, maintainers and asset owners. Recent cases of bridge failures due to extreme climatic events have highlighted the need for a reliable scour monitoring and early warning system to assess flood and geo-related hazards in real-time, providing advanced key info for repair and maintenance actions. Despite the past efforts to provide such a system for scour assessment, most of these instruments have not managed to realise a solution for scour monitoring due to technical and cost issues. The existing practices to assess, manage and maintain transportation assets are mainly based on visual inspection procedure which is also considered to be insufficient [2]. As a result there currently exists a gap in the knowledge and understanding of scour mechanism during flood incidents.
This study presents the architecture of ‘Climatic Hazard Monitoring and Bridge Scour Early Warning System’ (CliHaMoS) project, which is expected to significantly assist towards the optimisation of bridge performance against scour issues with a real-time data driven approach. CliHaMoS platform comprises of a new structural health monitoring system based on a novel bio-inspired sensing system aiming to deliver key information under different hydrodynamic events for real-time and forecasted assessment of flood hazards at bridges. The sensing solution is coupled by an early warning system, with advanced interoperability characteristics, to provide a holistic interactive platform and ensure that risks associated with flood hazards are properly and timely communicated to end-users. The obtained information is expected to enable stakeholders to plan adaptation strategies and proactively manage and maintain transportation infrastructure.
[1] Michalis, P., Saafi, M., and Judd. M. (2013) Capacitive sensors for offshore scour monitoring. Proceedings of the ICE – Energy, 166 (4), pp. 189-197
[2] Michalis, P., Saafi, M. and Judd, M. (2012) Wireless sensor networks for surveillance and monitoring of bridge scour. Proceedings of the XI International Conference Protection and Restoration of the Environment - PRE XI. Thessaloniki, Greece, pp. 1345–1354.
ACKNOWLEDGMENT:
This research is co-financed by Greece and the European Union (European Social FundESF) through the Operational Programme «Human Resources Development, Education and 4 Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” (MIS-5033021), implemented by the State Scholarships Foundation (ΙΚΥ).
How to cite: Michalis, P., Valyrakis, M., and Vintzilaiou, E.: A New Structural Health Monitoring System to Assess Bridge Scour, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1652, https://doi.org/10.5194/egusphere-egu21-1652, 2021.
EGU21-16313 | vPICO presentations | GM5.4
Gravity induced vertical motion of dense fluids into saturated granular bedsRui M L Ferreira, Gabriel Solis, Claudia Adduce, and Ana Margarida Ricardo
Gravity currents propagating over and within porous layers occurs in natural environments and in industrial processes. The particular modes by which the dense fluid flows into the porous layer is a subject that is not sufficiently understood. To overcome this research gap, we conducted laboratory experiments aimed at describing experimentally the dynamics of the drainage flow.
The experiments were conducted in a horizontal channel with a rectangular cross-section. The channel is 3.0 m long, 0.05 m wide. The porous bottom was composed of 5 cm and 10 cm layers of 3 mm borosilicate spheres – unimodal bed – and of a mixture of 3 mm (50% in weight) and 5 mm spheres (50%) – bi-modal bed. The porosity of the unimodal bed ranged between 0.60 and 0.64 (compatible with loose packing). The porosity of the bi-modal bed ranged between 0.61 and 0.65. All gravity currents were generated by releasing suddenly denser fluid locked by a thin vertical barrier placed at 0.2 m from the channel end. The dense fluid consists in a mixture of freshwater and salt (coloured with Rhodamine) while the ambient fluid is a solution of freshwater and ethanol. The density difference between the ambient fluid and the current, and the need to maintain the same refractive index, determine the amount of salt and alcohol added in each mixture. Here we report the findings of currents with a reduced gravity of 0.06 ms-2.
Each experiment was recorded by an high-speed camera with a frame-rate of 386 Hz and a resolution of 2320 x 1726 pxxpx. Measurements were based on light absorption techniques: a LED light panel 0.3 m high and 0.61 m long was used as back illumination. All images were calibrated to ascribe, pixel by pixel, a concentration value from a 8 bit gray level. Different calibrations were performed for the porous layer and for the surface current.
Results show that, in the slumping phase, the gravity current flows with velocities compatible with those over rough beds. As the current progresses further attenuation of momentum is noticed owing to mass loss to the porous bed.
The flow in the porous bed reveals plume instability akin to a Saffman-Taylor instability. The growth of the plumes seems independent from the initial fluid height in both types of porous beds. The wavelength and the growth rate of the plumes depends on the bed material. Plumes grow faster in the case of the bi-modal bed and the wavelength of the bi-modal bed is about 1.5 as that of the unimodal bed. It is hypothesised that the gravity-induced porous flow is best parameterized by a Péclet number defined as a ratio of dispersive (mechanical diffusion) and advective modes of transport. Smaller wavelengths and slower growths are attained for stronger dispersion, characterisitic of the unimodal bed. For bimodal beds, permeability is larger, and thus also advection. This causes the flow to concentrate in faster growing but farther apart plumes.
This research was funded by national funds through Portuguese Foundation for Science and Technology (FCT) project PTDC/CTA-OHR/30561/2017 (WinTherface).
How to cite: L Ferreira, R. M., Solis, G., Adduce, C., and Ricardo, A. M.: Gravity induced vertical motion of dense fluids into saturated granular beds, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16313, https://doi.org/10.5194/egusphere-egu21-16313, 2021.
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Gravity currents propagating over and within porous layers occurs in natural environments and in industrial processes. The particular modes by which the dense fluid flows into the porous layer is a subject that is not sufficiently understood. To overcome this research gap, we conducted laboratory experiments aimed at describing experimentally the dynamics of the drainage flow.
The experiments were conducted in a horizontal channel with a rectangular cross-section. The channel is 3.0 m long, 0.05 m wide. The porous bottom was composed of 5 cm and 10 cm layers of 3 mm borosilicate spheres – unimodal bed – and of a mixture of 3 mm (50% in weight) and 5 mm spheres (50%) – bi-modal bed. The porosity of the unimodal bed ranged between 0.60 and 0.64 (compatible with loose packing). The porosity of the bi-modal bed ranged between 0.61 and 0.65. All gravity currents were generated by releasing suddenly denser fluid locked by a thin vertical barrier placed at 0.2 m from the channel end. The dense fluid consists in a mixture of freshwater and salt (coloured with Rhodamine) while the ambient fluid is a solution of freshwater and ethanol. The density difference between the ambient fluid and the current, and the need to maintain the same refractive index, determine the amount of salt and alcohol added in each mixture. Here we report the findings of currents with a reduced gravity of 0.06 ms-2.
Each experiment was recorded by an high-speed camera with a frame-rate of 386 Hz and a resolution of 2320 x 1726 pxxpx. Measurements were based on light absorption techniques: a LED light panel 0.3 m high and 0.61 m long was used as back illumination. All images were calibrated to ascribe, pixel by pixel, a concentration value from a 8 bit gray level. Different calibrations were performed for the porous layer and for the surface current.
Results show that, in the slumping phase, the gravity current flows with velocities compatible with those over rough beds. As the current progresses further attenuation of momentum is noticed owing to mass loss to the porous bed.
The flow in the porous bed reveals plume instability akin to a Saffman-Taylor instability. The growth of the plumes seems independent from the initial fluid height in both types of porous beds. The wavelength and the growth rate of the plumes depends on the bed material. Plumes grow faster in the case of the bi-modal bed and the wavelength of the bi-modal bed is about 1.5 as that of the unimodal bed. It is hypothesised that the gravity-induced porous flow is best parameterized by a Péclet number defined as a ratio of dispersive (mechanical diffusion) and advective modes of transport. Smaller wavelengths and slower growths are attained for stronger dispersion, characterisitic of the unimodal bed. For bimodal beds, permeability is larger, and thus also advection. This causes the flow to concentrate in faster growing but farther apart plumes.
This research was funded by national funds through Portuguese Foundation for Science and Technology (FCT) project PTDC/CTA-OHR/30561/2017 (WinTherface).
How to cite: L Ferreira, R. M., Solis, G., Adduce, C., and Ricardo, A. M.: Gravity induced vertical motion of dense fluids into saturated granular beds, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16313, https://doi.org/10.5194/egusphere-egu21-16313, 2021.
GM6.3 – Submarine geomorphology
EGU21-13520 | vPICO presentations | GM6.3
SubSpread: An integrated approach to understand the signature, mechanics and controls of subaqueous spreadingMonica Giona Bucci, Aaron Micallef, Morelia Urlaub, and Joshu Mountjoy
Subaqueous spreading is a widespread type of mass movement, which involves extensional displacement along a gliding plane and the deformation of the failing layer into a sequence of ridges and troughs. Spreading has been poorly investigated, nonetheless it poses hazard to offshore infrastructures. SubSpread is a new project that will investigate the mechanics of the spreading failure and its geological controls in the subaqueous environment. The first objective of SubSpread is to identify the topographic and sedimentary signature of subaqueous environment. We have compiled a global database of subaqueous and subaerial spreads that includes information on physiography, geomorphology, sedimentology and geotechnical properties, where available. A preliminary analysis of the database reveals that spreading morphologies occur on both passive and active margins, especially in the headwall area of translational retrogressive slides. Potential causes of spreading include seismic loading (also glacially induced), sediment loading, and increased pore pressure generated by migration of fluid or gas. The latter may induce loss of shear strength and the formation of a weak layer, particularly in gentle open slopes. Information compiled in this database will also be used to develop a numerical model that can better understand the mechanics and rheological aspects of submarine spreading, focusing on the role played by pore pressure generation. The Tuaheni slide complex in the Hikurangi Margin of New Zealand is being used as a case-study in view of the wealth of geophysical and sedimentological data that are available. The final part of the SubSpread project will test whether the morphometric and sedimentological signature of spreading can provide information on past seismicity. In this case, the test site will be Lake Tekapo in the South Island of New Zealand.
How to cite: Giona Bucci, M., Micallef, A., Urlaub, M., and Mountjoy, J.: SubSpread: An integrated approach to understand the signature, mechanics and controls of subaqueous spreading, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13520, https://doi.org/10.5194/egusphere-egu21-13520, 2021.
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Subaqueous spreading is a widespread type of mass movement, which involves extensional displacement along a gliding plane and the deformation of the failing layer into a sequence of ridges and troughs. Spreading has been poorly investigated, nonetheless it poses hazard to offshore infrastructures. SubSpread is a new project that will investigate the mechanics of the spreading failure and its geological controls in the subaqueous environment. The first objective of SubSpread is to identify the topographic and sedimentary signature of subaqueous environment. We have compiled a global database of subaqueous and subaerial spreads that includes information on physiography, geomorphology, sedimentology and geotechnical properties, where available. A preliminary analysis of the database reveals that spreading morphologies occur on both passive and active margins, especially in the headwall area of translational retrogressive slides. Potential causes of spreading include seismic loading (also glacially induced), sediment loading, and increased pore pressure generated by migration of fluid or gas. The latter may induce loss of shear strength and the formation of a weak layer, particularly in gentle open slopes. Information compiled in this database will also be used to develop a numerical model that can better understand the mechanics and rheological aspects of submarine spreading, focusing on the role played by pore pressure generation. The Tuaheni slide complex in the Hikurangi Margin of New Zealand is being used as a case-study in view of the wealth of geophysical and sedimentological data that are available. The final part of the SubSpread project will test whether the morphometric and sedimentological signature of spreading can provide information on past seismicity. In this case, the test site will be Lake Tekapo in the South Island of New Zealand.
How to cite: Giona Bucci, M., Micallef, A., Urlaub, M., and Mountjoy, J.: SubSpread: An integrated approach to understand the signature, mechanics and controls of subaqueous spreading, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13520, https://doi.org/10.5194/egusphere-egu21-13520, 2021.
EGU21-13105 | vPICO presentations | GM6.3
Enhancing subtle seafloor relief variation: relief visualisation techniques for bathymetric dataAna Novak, Sašo Poglajen, and Marko Vrabec
Bathymetric data is commonly visualized as a simple shaded relief, where features oriented parallel to the light source are prone to false topographic perception or are even obscured to the viewer. On the other hand, many relief visualisation techniques developed in past decades are extensively used in visualisation and analysis of high-resolution digital elevation models, especially in geomorphological and archaeological studies. We tested and assessed the suitability of relief visualisation techniques provided by the Relief Visualisation Toolbox (RVT) software for representation of bathymetric data. We used a multibeam-sonar derived bathymetric model with a 10 x 10 m cell size from the Gulf of Trieste (northern Adriatic) characterised by a shallow low-relief seabed. Our results clearly demonstrate the effectiveness of relief visualisation techniques for exposing subtle relief variation in bathymetric data. We find that small-scale features (outcrops, wrecks, pockmarks, reefs, etc.) and negative linear features are best highlighted by “visualization for archaeological topography” (VAT) and “openness” techniques. High-relief features and topographic infection points are pronounced by “hillshade from multiple directions” and “sky-view factor” (SVF). Finally, “principal components analysis” (PCA), “prismatic openness”, “simple local relief model”, “anisotropic SVF” and “local dominance” algorithms show best results when we want to highlight both high- and low-relief features in one image. The tested techniques are far superior to a simple hillshade visualisation especially when imaging low-gradient relief (common on continental shelves and abyssal plains) where topographic details are often not adequately pronounced by hillshading. To our knowledge, this study represents the first attempt to test and compare several relief visualisation techniques for bathymetric data.
How to cite: Novak, A., Poglajen, S., and Vrabec, M.: Enhancing subtle seafloor relief variation: relief visualisation techniques for bathymetric data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13105, https://doi.org/10.5194/egusphere-egu21-13105, 2021.
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Bathymetric data is commonly visualized as a simple shaded relief, where features oriented parallel to the light source are prone to false topographic perception or are even obscured to the viewer. On the other hand, many relief visualisation techniques developed in past decades are extensively used in visualisation and analysis of high-resolution digital elevation models, especially in geomorphological and archaeological studies. We tested and assessed the suitability of relief visualisation techniques provided by the Relief Visualisation Toolbox (RVT) software for representation of bathymetric data. We used a multibeam-sonar derived bathymetric model with a 10 x 10 m cell size from the Gulf of Trieste (northern Adriatic) characterised by a shallow low-relief seabed. Our results clearly demonstrate the effectiveness of relief visualisation techniques for exposing subtle relief variation in bathymetric data. We find that small-scale features (outcrops, wrecks, pockmarks, reefs, etc.) and negative linear features are best highlighted by “visualization for archaeological topography” (VAT) and “openness” techniques. High-relief features and topographic infection points are pronounced by “hillshade from multiple directions” and “sky-view factor” (SVF). Finally, “principal components analysis” (PCA), “prismatic openness”, “simple local relief model”, “anisotropic SVF” and “local dominance” algorithms show best results when we want to highlight both high- and low-relief features in one image. The tested techniques are far superior to a simple hillshade visualisation especially when imaging low-gradient relief (common on continental shelves and abyssal plains) where topographic details are often not adequately pronounced by hillshading. To our knowledge, this study represents the first attempt to test and compare several relief visualisation techniques for bathymetric data.
How to cite: Novak, A., Poglajen, S., and Vrabec, M.: Enhancing subtle seafloor relief variation: relief visualisation techniques for bathymetric data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13105, https://doi.org/10.5194/egusphere-egu21-13105, 2021.
EGU21-15812 | vPICO presentations | GM6.3
Numerical Modeling of Sampling Seafloor Sediments to Study Their Rheological PropertiesNikita Dubinya, Victor Nachev, and Tikhotskii Sergey
The work presents the results of applying SIMULIA Abaqus's capabilities to solve problems related to infrastructure development in the development of oil and gas fields on the continental shelf. The primary attention is paid to the stability of the load-bearing structures of infrastructure facilities. When developing oil and gas fields located in the continental shelf, several geomechanical problems not typical for onshore fields arise. First of all, there is a need to construct a detailed model of the mechanical properties of the upper layers of bottom sediments in conditions of limited data on these properties. This limitation of data is caused by the complexity and cost of engineering drilling, which in other conditions provides the necessary information regarding the properties of the upper layers of sediments. Current study describes the proposed set of methods for studying the mechanical properties of the upper layers of bottom sediments using sampling. It is shown that the process of bottom sampling itself makes it possible to estimate the mechanical properties of bottom sediments. Quantitatively, such estimations can be made based on a numerical solution of the contact problem of gravity corer indentation into visco-elastoplastic medium, the specific rheological properties of which are a priori unknown. The possibility of determining the possible values of these properties from the data obtained in the sampling process (the dependence of the acceleration of the contact point on time) is demonstrated in the study with solution of the inverse problem.
How to cite: Dubinya, N., Nachev, V., and Sergey, T.: Numerical Modeling of Sampling Seafloor Sediments to Study Their Rheological Properties, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15812, https://doi.org/10.5194/egusphere-egu21-15812, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The work presents the results of applying SIMULIA Abaqus's capabilities to solve problems related to infrastructure development in the development of oil and gas fields on the continental shelf. The primary attention is paid to the stability of the load-bearing structures of infrastructure facilities. When developing oil and gas fields located in the continental shelf, several geomechanical problems not typical for onshore fields arise. First of all, there is a need to construct a detailed model of the mechanical properties of the upper layers of bottom sediments in conditions of limited data on these properties. This limitation of data is caused by the complexity and cost of engineering drilling, which in other conditions provides the necessary information regarding the properties of the upper layers of sediments. Current study describes the proposed set of methods for studying the mechanical properties of the upper layers of bottom sediments using sampling. It is shown that the process of bottom sampling itself makes it possible to estimate the mechanical properties of bottom sediments. Quantitatively, such estimations can be made based on a numerical solution of the contact problem of gravity corer indentation into visco-elastoplastic medium, the specific rheological properties of which are a priori unknown. The possibility of determining the possible values of these properties from the data obtained in the sampling process (the dependence of the acceleration of the contact point on time) is demonstrated in the study with solution of the inverse problem.
How to cite: Dubinya, N., Nachev, V., and Sergey, T.: Numerical Modeling of Sampling Seafloor Sediments to Study Their Rheological Properties, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15812, https://doi.org/10.5194/egusphere-egu21-15812, 2021.
EGU21-14413 | vPICO presentations | GM6.3
Multi-physics, multi-domain, and multi-scale coupling concept for groundwater to surface-water interactions driving submarine landscape evolutionShubhangi Gupta and Aaron micallef
Groundwater is an important geomorphic agent, and its interactions with land and surface-water play a critical role in driving landscape evolution through highly coupled and complex processes such as internal erosion, surface erosion, slope failure and debris flows.
From a modelling point of view, a common approach has been to tackle the hydrologic and geomorphic processes separately. To date, the multi-domain and multi-physics interactions across the groundwater – surface-water interfaces remain poorly conceptualized. Furthermore, the groundwater models are typically highly simplified; the effects of thermal fluxes, diagenetic processes, multi-phase transport and phase transitions, density driven flows, etc. are either ignored, or introduced through lumped or reduced models without fully resolving the underlying process couplings. In sediments that are susceptible to chemical weathering, like carbonate rocks, there are almost no known and validated models that can handle evolving pore geometry due to carbonate dissolution in conjunction with internal erosion. Moreover, the saturated and unsaturated groundwater, surface-water, seafloor, and subaerial terrain constitute multiple distinct domains. The interactions across these domains occur at multiple length and time scales, and the landscape evolution results in changing geometries of each domain.
Due to the multi-physics, multi-scale, and multi-domain characteristics of these models, the resulting systems of equations are highly complex, nonlinear, non-standard, and computationally challenging, both in terms of numerical implementation as well as computing resources. These features not only add to the conceptual and numerical complexity, but also demand specialized and targeted solutions.
Here we present an abstract modular framework to resolve the multi-physics couplings within targeted sub-domains (i.e., 2D/3D sub-surface and1D/2D surface-water, sea-floor and subaerial terrain) and across the domain interfaces. We also introduce an algorithm to handle the changing geometries of these domains. This framework is being developed within the ERC project ‘MARCAN’ and will be used to assess the role of groundwater flow and seepage on the geomorphic evolution of continental margins.
How to cite: Gupta, S. and micallef, A.: Multi-physics, multi-domain, and multi-scale coupling concept for groundwater to surface-water interactions driving submarine landscape evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14413, https://doi.org/10.5194/egusphere-egu21-14413, 2021.
Groundwater is an important geomorphic agent, and its interactions with land and surface-water play a critical role in driving landscape evolution through highly coupled and complex processes such as internal erosion, surface erosion, slope failure and debris flows.
From a modelling point of view, a common approach has been to tackle the hydrologic and geomorphic processes separately. To date, the multi-domain and multi-physics interactions across the groundwater – surface-water interfaces remain poorly conceptualized. Furthermore, the groundwater models are typically highly simplified; the effects of thermal fluxes, diagenetic processes, multi-phase transport and phase transitions, density driven flows, etc. are either ignored, or introduced through lumped or reduced models without fully resolving the underlying process couplings. In sediments that are susceptible to chemical weathering, like carbonate rocks, there are almost no known and validated models that can handle evolving pore geometry due to carbonate dissolution in conjunction with internal erosion. Moreover, the saturated and unsaturated groundwater, surface-water, seafloor, and subaerial terrain constitute multiple distinct domains. The interactions across these domains occur at multiple length and time scales, and the landscape evolution results in changing geometries of each domain.
Due to the multi-physics, multi-scale, and multi-domain characteristics of these models, the resulting systems of equations are highly complex, nonlinear, non-standard, and computationally challenging, both in terms of numerical implementation as well as computing resources. These features not only add to the conceptual and numerical complexity, but also demand specialized and targeted solutions.
Here we present an abstract modular framework to resolve the multi-physics couplings within targeted sub-domains (i.e., 2D/3D sub-surface and1D/2D surface-water, sea-floor and subaerial terrain) and across the domain interfaces. We also introduce an algorithm to handle the changing geometries of these domains. This framework is being developed within the ERC project ‘MARCAN’ and will be used to assess the role of groundwater flow and seepage on the geomorphic evolution of continental margins.
How to cite: Gupta, S. and micallef, A.: Multi-physics, multi-domain, and multi-scale coupling concept for groundwater to surface-water interactions driving submarine landscape evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14413, https://doi.org/10.5194/egusphere-egu21-14413, 2021.
EGU21-3139 | vPICO presentations | GM6.3
Sedimentary Processes on a Mixed Turbidite-Contourite System - Northern Campos Basin, SE BrazilBruna Teixeira Pandolpho, Antonio Henrique da Fontoura Klein, Isadora Dutra, Michel M. Mahiques, Adriano R. Viana, Gilmar Vital Bueno, Arthur Antonio Machado, Yuri L. Camargo, Cizia M. Hercos, Yhaohannah Lima, Antonio Fernando H. F. Filho, and Carlos E. Theodoro
A new mixed turbidite-contourite system is described in the northern Campos Basin, southeastern Brazilian margin. This system is developed in a middle slope setting and was formed through non-synchronous interaction between the turbidity current and a contour current in the same stratigraphic interval (Miocene). Different depositional cycles were accounted based on their diagnostic seismic features. Seismic attributes, seismic facies, and isochron maps were used to identify alternating cycles of downslope and alongslope processes in the study area, along with the intermediate stage with features from both processes (mixed system). Seismic units were then associated with the dominant type of current. Depositional processes resulted from alongslope current activity can be distinguished from the downslope current activity, based on the acoustic characteristics (root-mean-square (RMS) amplitude values), internal architecture, and external geometry pattern. While alongslope currents deposits consist of mainly low RMS amplitude values clinoforms with an alongslope trend; the downslope gravity deposits present high-amplitude or chaotic seismic facies, usually higher values of RMS amplitude, channel or channel-lobe features, erosive surfaces, and a basinward depositional trend. The first and oldest seismic unit (S1) was interpreted as a dominantly alongslope system, with aggrading sigmoidal clinoforms and high-frequency, low-amplitude reflections commonly associated with fine-grained sedimentary deposits, typical of a plastered drift. Basinward mass transport deposit derived from previous drift instability are often identified. Seismic unit S2 represents the intermediate stage where both gravity-driven and along-slope currents act asynchronously. It is referred to as a mixed turbidite-contourite sequence that shows high-amplitude sediment waves migrating upslope and a moat feature carved in its upslope front. The interfingering between high- and low-amplitude reflectors, distal chaotic facies, together with sediment waves and a channel moat, points to a sand-rich deposit reworked by northward-flowing contour currents. Seismic units S3 and S4 show downslope features with chaotic facies (S3) and paleochannels with coarse basal lag deposits interpreted after the high RMS amplitude values (S4). In S4, a series of long-lived submarine channels formed. The last seismic unit, S5, referred to as the second plastered drift sequence, is marked by low-amplitude clinoforms that thin basinward. Important information on the paleocurrents' direction was also made based on the final deposits display (e.g. terraces, sediment waves, paleochannels), where a northward-flowing bottom current was assumed. Research on alternating dominant processes and transitional stages or mixed depositional systems may provide a better understanding of deep-water depositional processes. Because these processes do not always fit previous depositional models that are mainly described for synchronous systems, new insights on cyclic non-synchronous mixed systems can improve our understanding of how mixed systems are organized through time and space. We can also determine which were the dominant processes that controlled the sedimentation by indicating periods where the margin was mostly submitted to sediment transfer from continent to the basin and periods where the oceanic currents prevailed by redistributing sediments along the isobaths and replacing the axis of downslope transfer conduits. Setting new models on cyclic deposits and intermediate stages can have a future economic impact on potential hydrocarbon reservoir architecture.
How to cite: Pandolpho, B. T., Klein, A. H. D. F., Dutra, I., Mahiques, M. M., Viana, A. R., Bueno, G. V., Machado, A. A., Camargo, Y. L., Hercos, C. M., Lima, Y., Filho, A. F. H. F., and Theodoro, C. E.: Sedimentary Processes on a Mixed Turbidite-Contourite System - Northern Campos Basin, SE Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3139, https://doi.org/10.5194/egusphere-egu21-3139, 2021.
A new mixed turbidite-contourite system is described in the northern Campos Basin, southeastern Brazilian margin. This system is developed in a middle slope setting and was formed through non-synchronous interaction between the turbidity current and a contour current in the same stratigraphic interval (Miocene). Different depositional cycles were accounted based on their diagnostic seismic features. Seismic attributes, seismic facies, and isochron maps were used to identify alternating cycles of downslope and alongslope processes in the study area, along with the intermediate stage with features from both processes (mixed system). Seismic units were then associated with the dominant type of current. Depositional processes resulted from alongslope current activity can be distinguished from the downslope current activity, based on the acoustic characteristics (root-mean-square (RMS) amplitude values), internal architecture, and external geometry pattern. While alongslope currents deposits consist of mainly low RMS amplitude values clinoforms with an alongslope trend; the downslope gravity deposits present high-amplitude or chaotic seismic facies, usually higher values of RMS amplitude, channel or channel-lobe features, erosive surfaces, and a basinward depositional trend. The first and oldest seismic unit (S1) was interpreted as a dominantly alongslope system, with aggrading sigmoidal clinoforms and high-frequency, low-amplitude reflections commonly associated with fine-grained sedimentary deposits, typical of a plastered drift. Basinward mass transport deposit derived from previous drift instability are often identified. Seismic unit S2 represents the intermediate stage where both gravity-driven and along-slope currents act asynchronously. It is referred to as a mixed turbidite-contourite sequence that shows high-amplitude sediment waves migrating upslope and a moat feature carved in its upslope front. The interfingering between high- and low-amplitude reflectors, distal chaotic facies, together with sediment waves and a channel moat, points to a sand-rich deposit reworked by northward-flowing contour currents. Seismic units S3 and S4 show downslope features with chaotic facies (S3) and paleochannels with coarse basal lag deposits interpreted after the high RMS amplitude values (S4). In S4, a series of long-lived submarine channels formed. The last seismic unit, S5, referred to as the second plastered drift sequence, is marked by low-amplitude clinoforms that thin basinward. Important information on the paleocurrents' direction was also made based on the final deposits display (e.g. terraces, sediment waves, paleochannels), where a northward-flowing bottom current was assumed. Research on alternating dominant processes and transitional stages or mixed depositional systems may provide a better understanding of deep-water depositional processes. Because these processes do not always fit previous depositional models that are mainly described for synchronous systems, new insights on cyclic non-synchronous mixed systems can improve our understanding of how mixed systems are organized through time and space. We can also determine which were the dominant processes that controlled the sedimentation by indicating periods where the margin was mostly submitted to sediment transfer from continent to the basin and periods where the oceanic currents prevailed by redistributing sediments along the isobaths and replacing the axis of downslope transfer conduits. Setting new models on cyclic deposits and intermediate stages can have a future economic impact on potential hydrocarbon reservoir architecture.
How to cite: Pandolpho, B. T., Klein, A. H. D. F., Dutra, I., Mahiques, M. M., Viana, A. R., Bueno, G. V., Machado, A. A., Camargo, Y. L., Hercos, C. M., Lima, Y., Filho, A. F. H. F., and Theodoro, C. E.: Sedimentary Processes on a Mixed Turbidite-Contourite System - Northern Campos Basin, SE Brazil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3139, https://doi.org/10.5194/egusphere-egu21-3139, 2021.
EGU21-12712 | vPICO presentations | GM6.3
Morphological rejuvenation on tectonic seamounts: insights from the Gorringe Bank, SW Iberian MarginDavide Gamboa, Rachid Omira, Aldina Piedade, Pedro Terrinha, Cristina Roque, and Nevio Zitellini
Seamounts are spectacular bathymetric features common within volcanic and tectonically active continental margins. During their lifecycles, they evolve through stages of construction and destruction. Seamount chains on the Southwest Iberian Margin are prone to instability and collapse due to regionally complex tectonism with moderate to high seismicity. In this work we investigate collapse episodes during the lifecycle of the tectonic Gorringe Bank (GB), the largest submarine seamount offshore European margins, based on recurrence patterns of MTDs on the active thrust flank. Eight MTDs with relevant expression on the seismic data were analysed, four of estimated Miocene age and four on a Pliocene-Quarternary interval. Miocene MTDs are overall larger and correlate with the main uplift stages of the GB structure. Their distribution and relative timing suggest that failure-triggering earthquakes were common along the whole length of the GB. Pliocene to Quarternary MTDs tend to cluster along the northern half of the GB flank and are generally smaller. Based on our observations, we propose that the lifecycle of tectonic seamounts is marked by morphological rejuvenation episodes driven by tectonic activity between major collapse events or cycles. Tectonic-driven rejuvenation is thus key to hinder or obliterate evidence of past high-magnitude destructive events on tectonic seamount morphology.
How to cite: Gamboa, D., Omira, R., Piedade, A., Terrinha, P., Roque, C., and Zitellini, N.: Morphological rejuvenation on tectonic seamounts: insights from the Gorringe Bank, SW Iberian Margin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12712, https://doi.org/10.5194/egusphere-egu21-12712, 2021.
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Seamounts are spectacular bathymetric features common within volcanic and tectonically active continental margins. During their lifecycles, they evolve through stages of construction and destruction. Seamount chains on the Southwest Iberian Margin are prone to instability and collapse due to regionally complex tectonism with moderate to high seismicity. In this work we investigate collapse episodes during the lifecycle of the tectonic Gorringe Bank (GB), the largest submarine seamount offshore European margins, based on recurrence patterns of MTDs on the active thrust flank. Eight MTDs with relevant expression on the seismic data were analysed, four of estimated Miocene age and four on a Pliocene-Quarternary interval. Miocene MTDs are overall larger and correlate with the main uplift stages of the GB structure. Their distribution and relative timing suggest that failure-triggering earthquakes were common along the whole length of the GB. Pliocene to Quarternary MTDs tend to cluster along the northern half of the GB flank and are generally smaller. Based on our observations, we propose that the lifecycle of tectonic seamounts is marked by morphological rejuvenation episodes driven by tectonic activity between major collapse events or cycles. Tectonic-driven rejuvenation is thus key to hinder or obliterate evidence of past high-magnitude destructive events on tectonic seamount morphology.
How to cite: Gamboa, D., Omira, R., Piedade, A., Terrinha, P., Roque, C., and Zitellini, N.: Morphological rejuvenation on tectonic seamounts: insights from the Gorringe Bank, SW Iberian Margin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12712, https://doi.org/10.5194/egusphere-egu21-12712, 2021.
EGU21-12602 | vPICO presentations | GM6.3
The MAGICLAND (Marine Geohazards InduCed by LANDslides) database: Early results on submarine landslide distribution and morphometrics offshore PortugalRachid Omira, Davide Gamboa, and Pedro Terrinha
Submarine landslides are major geohazards occurring on distinct seabed domains ranging from shallow coastal areas to the deeper points of the ocean. The nature and relief of the seabed are key factors influencing the location and size of submarine landslides. Mass-failures on the continental slopes are frequent, but collapses on and along chains of oceanic seamounts and ridges can account also for a high frequency of events. Regardless of their area of occurrence, submarine landslides are a major hazard that needs to be recognised and categorised. For this purpose, numerous efforts have been made to compile databases of submarine landslides with the aim to better understand their distribution and characteristics on marine settings around the world.
This work presents the initial efforts of the MAGICLAND (Marine Geo-hazards Induced by underwater Landslides in the SW Iberian Margin) database which, based on bathymetric DEMs available through EmodNET, compiled geomorphological properties of 1552 morphological scars and submarine landslides offshore West and Southwest Portugal. These are distributed through seven morphological domains: 1) canyons incising the continental slope (232 landslide episodes); 2) continental slope (233 landslide episodes); 3) large seamounts (437 landslide episodes); 4) submarine ridges and small seamounts (263 landslide episodes); 5) Gulf of Cadiz (226 landslide episodes); 6) Gulf of Cadiz banks and channels (123 landslide episodes); and 7) Estremadura Spur (38 landslide episodes). A wealth of 43 parameters were measured or calculated, which include a subset of morphological quantifications for the evacuation and deposit sections for 347 occurrences where the latter was observed. We present the morphological data and any derived computations as measured on the 3D surface in order to increase their accuracy and mitigate the effect of slope gradient on map-based 2D analysis. The larger events were recorded on the large seamounts and the ridges domains, which also correspond to the larger recorded landslide heights (measured as the difference between minimum and maximum depths). Good correlations (coefficient of determination R2>0.8) where obtained for Area-Volume, Width-Area, and Length-Area relationships. Where evacuation and deposit sections were discernible, their area relationships present a better correlation compared to their lengths.
Further stages of the database development will involve the addition of still unmapped scars, as well as further statistical analysis and integration with available geophysical and geotechnical datasets for the areas of study. This dataset will be made available for the free use and benefit of the international marine community. Further contributions or analysis based on, and complementing the MAGICLAND database will be welcome.
This work is supported by the FCT funded project MAGICLAND - MArine Geo-hazards InduCed by underwater LANDslides in the SW Iberian Margin (Ref: PTDC/CTA-GEO/30381/2017).
How to cite: Omira, R., Gamboa, D., and Terrinha, P.: The MAGICLAND (Marine Geohazards InduCed by LANDslides) database: Early results on submarine landslide distribution and morphometrics offshore Portugal , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12602, https://doi.org/10.5194/egusphere-egu21-12602, 2021.
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Submarine landslides are major geohazards occurring on distinct seabed domains ranging from shallow coastal areas to the deeper points of the ocean. The nature and relief of the seabed are key factors influencing the location and size of submarine landslides. Mass-failures on the continental slopes are frequent, but collapses on and along chains of oceanic seamounts and ridges can account also for a high frequency of events. Regardless of their area of occurrence, submarine landslides are a major hazard that needs to be recognised and categorised. For this purpose, numerous efforts have been made to compile databases of submarine landslides with the aim to better understand their distribution and characteristics on marine settings around the world.
This work presents the initial efforts of the MAGICLAND (Marine Geo-hazards Induced by underwater Landslides in the SW Iberian Margin) database which, based on bathymetric DEMs available through EmodNET, compiled geomorphological properties of 1552 morphological scars and submarine landslides offshore West and Southwest Portugal. These are distributed through seven morphological domains: 1) canyons incising the continental slope (232 landslide episodes); 2) continental slope (233 landslide episodes); 3) large seamounts (437 landslide episodes); 4) submarine ridges and small seamounts (263 landslide episodes); 5) Gulf of Cadiz (226 landslide episodes); 6) Gulf of Cadiz banks and channels (123 landslide episodes); and 7) Estremadura Spur (38 landslide episodes). A wealth of 43 parameters were measured or calculated, which include a subset of morphological quantifications for the evacuation and deposit sections for 347 occurrences where the latter was observed. We present the morphological data and any derived computations as measured on the 3D surface in order to increase their accuracy and mitigate the effect of slope gradient on map-based 2D analysis. The larger events were recorded on the large seamounts and the ridges domains, which also correspond to the larger recorded landslide heights (measured as the difference between minimum and maximum depths). Good correlations (coefficient of determination R2>0.8) where obtained for Area-Volume, Width-Area, and Length-Area relationships. Where evacuation and deposit sections were discernible, their area relationships present a better correlation compared to their lengths.
Further stages of the database development will involve the addition of still unmapped scars, as well as further statistical analysis and integration with available geophysical and geotechnical datasets for the areas of study. This dataset will be made available for the free use and benefit of the international marine community. Further contributions or analysis based on, and complementing the MAGICLAND database will be welcome.
This work is supported by the FCT funded project MAGICLAND - MArine Geo-hazards InduCed by underwater LANDslides in the SW Iberian Margin (Ref: PTDC/CTA-GEO/30381/2017).
How to cite: Omira, R., Gamboa, D., and Terrinha, P.: The MAGICLAND (Marine Geohazards InduCed by LANDslides) database: Early results on submarine landslide distribution and morphometrics offshore Portugal , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12602, https://doi.org/10.5194/egusphere-egu21-12602, 2021.
EGU21-9713 | vPICO presentations | GM6.3
Long-term seafloor morphological changes generated by bottom trawling on the northern Catalan continental shelf (NW Mediterranean)Ruth Durán, Pere Puig, Araceli Muñoz, Claudio Lo Iacono, Jorge Guillén, Aaron Micallef, and Albert Palanques
The north-western Mediterranean continental margin is one of the few regions in the world where bottom trawling has been continuously practised since several decades. Among the existing trawling techniques, the one practised on this region is the "otter trawling", which has a strong impact on the seafloor morphology via scraping and ploughing, especially on muddy substrates. High-resolution multibeam bathymetry and backscatter data, side scan sonar images, sediment cores and satellite based Vessel Monitoring System (VMS) data have been integrated to investigate the impact of bottom trawling on the seafloor morphology of the northern Catalan continental shelf (NW Mediterranean). Satellite-based navigation tracks from bottom trawlers operating in the study area during 6 years (2006-2011) reveal the spatial distribution of fishing grounds and the occurrence of an intense trawling effort around the 50-60 m isobaths, since trawling is banned at shallow depths. Backscatter imagery shows a narrow (120-250 m wide) and discontinuous high backscatter facies along this depth range, extending parallel to the coastline for more than 40 km from Portbou to l’Estartit. In the bathymetric data, this high backscatter region also coincides with an abrupt change in the mean seafloor gradient (from 0.8° in the inner shelf to 0.4° in the middle shelf), or locally with a narrow (50-150 m wide) slightly depressed (0.2-0.6 m deep) channeled morphology. Side-scan sonar images display high density of trawl marks generated by fishing gears in this area. Further offshore, scattered narrower trawl hauls are also observed on the middle shelf (60-90 m deep), where they can be traced across several thousands of meters. Sediment cores retrieved from the area of high backscatter and largest trawling intensity display sediment coarsening in the upper layers (0-4 cm) caused by winnowing of finer fractions. These findings demonstrate that chronic stirring, mixing and erosion of surface sediments induced by recurrent trawling persisting over the same fishing grounds can cause long-term morphological and sedimentary changes on the continental shelf seafloor.
This study has received funding from the ABIDES (Assessment of Bottom-trawling Impacts in the Deep-sea Sediments) Spanish Research Project (CTM2015-65142-R) and the European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No. 867471. Additional funds were provided by the Generalitat de Catalunya Generalitat de Catalunya (2017 SGR-663 and -1588) and by the Spanish Research Project ABRIC (RTI2018-096434-B-I00). This work is contributing to the ICM’s ‘Center of Excellence’ Severo Ochoa (CEX2019-000928-S). The authors wish to thank the Secretaría General de Pesca and Tragsa for the 2004 Espace Project dataset.
How to cite: Durán, R., Puig, P., Muñoz, A., Lo Iacono, C., Guillén, J., Micallef, A., and Palanques, A.: Long-term seafloor morphological changes generated by bottom trawling on the northern Catalan continental shelf (NW Mediterranean), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9713, https://doi.org/10.5194/egusphere-egu21-9713, 2021.
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The north-western Mediterranean continental margin is one of the few regions in the world where bottom trawling has been continuously practised since several decades. Among the existing trawling techniques, the one practised on this region is the "otter trawling", which has a strong impact on the seafloor morphology via scraping and ploughing, especially on muddy substrates. High-resolution multibeam bathymetry and backscatter data, side scan sonar images, sediment cores and satellite based Vessel Monitoring System (VMS) data have been integrated to investigate the impact of bottom trawling on the seafloor morphology of the northern Catalan continental shelf (NW Mediterranean). Satellite-based navigation tracks from bottom trawlers operating in the study area during 6 years (2006-2011) reveal the spatial distribution of fishing grounds and the occurrence of an intense trawling effort around the 50-60 m isobaths, since trawling is banned at shallow depths. Backscatter imagery shows a narrow (120-250 m wide) and discontinuous high backscatter facies along this depth range, extending parallel to the coastline for more than 40 km from Portbou to l’Estartit. In the bathymetric data, this high backscatter region also coincides with an abrupt change in the mean seafloor gradient (from 0.8° in the inner shelf to 0.4° in the middle shelf), or locally with a narrow (50-150 m wide) slightly depressed (0.2-0.6 m deep) channeled morphology. Side-scan sonar images display high density of trawl marks generated by fishing gears in this area. Further offshore, scattered narrower trawl hauls are also observed on the middle shelf (60-90 m deep), where they can be traced across several thousands of meters. Sediment cores retrieved from the area of high backscatter and largest trawling intensity display sediment coarsening in the upper layers (0-4 cm) caused by winnowing of finer fractions. These findings demonstrate that chronic stirring, mixing and erosion of surface sediments induced by recurrent trawling persisting over the same fishing grounds can cause long-term morphological and sedimentary changes on the continental shelf seafloor.
This study has received funding from the ABIDES (Assessment of Bottom-trawling Impacts in the Deep-sea Sediments) Spanish Research Project (CTM2015-65142-R) and the European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No. 867471. Additional funds were provided by the Generalitat de Catalunya Generalitat de Catalunya (2017 SGR-663 and -1588) and by the Spanish Research Project ABRIC (RTI2018-096434-B-I00). This work is contributing to the ICM’s ‘Center of Excellence’ Severo Ochoa (CEX2019-000928-S). The authors wish to thank the Secretaría General de Pesca and Tragsa for the 2004 Espace Project dataset.
How to cite: Durán, R., Puig, P., Muñoz, A., Lo Iacono, C., Guillén, J., Micallef, A., and Palanques, A.: Long-term seafloor morphological changes generated by bottom trawling on the northern Catalan continental shelf (NW Mediterranean), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9713, https://doi.org/10.5194/egusphere-egu21-9713, 2021.
EGU21-15380 | vPICO presentations | GM6.3
Morphology of small-scale submarine mass movement events across the northwest United KingdomGareth Carter, Rhys Cooper, Joana Gafeira, John Howe, and David Long
Given the potentially devastating consequences of shallow submarine landslides on infrastructure and human lives, it is imperative that we understand potential slope stability issues within marine coastal regions. In Scottish waters, our lack of knowledge regarding the nature of the seabed within the fjords and coastal inlets is concerning given that these sea lochs have similar morphological features and settings to global examples (e.g. Norway) where recent slope failures have had such highly devastating results. Global examples from similar physiographic settings also demonstrate the temporal aspect of these events, highlighting that they are caused by active modern processes and therefore represent contemporary geohazards. In addition, previous studies have highlighted that there tends to be a scale bias towards the mapping and reporting of large-scale events, and there is a requirement for studies that focus on small-scale (≤1 km3) mass movements which can still have damaging consequences on seafloor and coastal (both nearshore and onshore) infrastructure.
In this study, a review of multibeam echo sounder (MBES) survey datasets from five locations around the United Kingdom northwest coast has led to the identification of a total of 14 separate submarine mass movement scars and deposits within the fjords (sea lochs) and coastal inlets of mainland Scotland, and the channels between the islands of the Inner Hebrides. In these areas, Quaternary sediment deposition was dominated by glacial and glaciomarine processes. Analysis of the morphometric parameters of each submarine mass movement has revealed that they fall into four distinct groups of subaqueous landslides; Singular Slumps, Singular Translational, Multiple Single-Type, and Complex (translational & rotational) failures. The Singular Slump Group includes discrete, individual subaqueous slumps that exhibit no evidence of modification through the merging of several scars. The Singular Translational Group comprise a single slide that displays characteristics associated with a single translational (planar) failure with no merging of multiple events. The Multiple Single-Type Group incorporates scars and deposits that displayed morphometric features consistent with the amalgamation of several failure events of the same type (e.g. debris flows or slumps). Finally, the Complex (translational & rotational) Group comprises landslides that exhibited complex styles of failures, including both translational and rotational mechanisms controlling the same slide. The submarine mass movements that comprise this dataset are then discussed in relation to global fjordic and glaciomarine nearshore settings, and slope failure trigger mechanisms associated with these environments are described with tentative links to individual submarine landslides from the database, where appropriate. It is acknowledged that additional MBES data are needed not only to expand this database but also to create a more statistically robust study. However, this initial study provides the basis for a much wider investigation of submarine mass movements and correlations between their morphometric parameters.
How to cite: Carter, G., Cooper, R., Gafeira, J., Howe, J., and Long, D.: Morphology of small-scale submarine mass movement events across the northwest United Kingdom, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15380, https://doi.org/10.5194/egusphere-egu21-15380, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Given the potentially devastating consequences of shallow submarine landslides on infrastructure and human lives, it is imperative that we understand potential slope stability issues within marine coastal regions. In Scottish waters, our lack of knowledge regarding the nature of the seabed within the fjords and coastal inlets is concerning given that these sea lochs have similar morphological features and settings to global examples (e.g. Norway) where recent slope failures have had such highly devastating results. Global examples from similar physiographic settings also demonstrate the temporal aspect of these events, highlighting that they are caused by active modern processes and therefore represent contemporary geohazards. In addition, previous studies have highlighted that there tends to be a scale bias towards the mapping and reporting of large-scale events, and there is a requirement for studies that focus on small-scale (≤1 km3) mass movements which can still have damaging consequences on seafloor and coastal (both nearshore and onshore) infrastructure.
In this study, a review of multibeam echo sounder (MBES) survey datasets from five locations around the United Kingdom northwest coast has led to the identification of a total of 14 separate submarine mass movement scars and deposits within the fjords (sea lochs) and coastal inlets of mainland Scotland, and the channels between the islands of the Inner Hebrides. In these areas, Quaternary sediment deposition was dominated by glacial and glaciomarine processes. Analysis of the morphometric parameters of each submarine mass movement has revealed that they fall into four distinct groups of subaqueous landslides; Singular Slumps, Singular Translational, Multiple Single-Type, and Complex (translational & rotational) failures. The Singular Slump Group includes discrete, individual subaqueous slumps that exhibit no evidence of modification through the merging of several scars. The Singular Translational Group comprise a single slide that displays characteristics associated with a single translational (planar) failure with no merging of multiple events. The Multiple Single-Type Group incorporates scars and deposits that displayed morphometric features consistent with the amalgamation of several failure events of the same type (e.g. debris flows or slumps). Finally, the Complex (translational & rotational) Group comprises landslides that exhibited complex styles of failures, including both translational and rotational mechanisms controlling the same slide. The submarine mass movements that comprise this dataset are then discussed in relation to global fjordic and glaciomarine nearshore settings, and slope failure trigger mechanisms associated with these environments are described with tentative links to individual submarine landslides from the database, where appropriate. It is acknowledged that additional MBES data are needed not only to expand this database but also to create a more statistically robust study. However, this initial study provides the basis for a much wider investigation of submarine mass movements and correlations between their morphometric parameters.
How to cite: Carter, G., Cooper, R., Gafeira, J., Howe, J., and Long, D.: Morphology of small-scale submarine mass movement events across the northwest United Kingdom, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15380, https://doi.org/10.5194/egusphere-egu21-15380, 2021.
EGU21-13364 | vPICO presentations | GM6.3
Investigating the controls of submarine landslides and associated hazards in Pangnirtung Fiord, Eastern Baffin Island (Nunavut)Philip Sedore, Alexandre Normandeau, and Vittorio Maselli
High-latitude fiords are susceptible to hazardous subaerial and submarine slope failures. Recent investigations have shown that past slope failures in fiords of Greenland and Alaska have generated devastating landslide induced tsunamis. Since coastal communities inhabit these high-latitude fiords, it is critical to understand the slope failure recurrence time, their distribution, potential triggers, and ability to generate tsunamis. In this study, we identified > 50 near-surface submarine landslides in Pangnirtung Fiord, eastern Baffin Island, Nunavut, using multibeam bathymetric and sub-bottom profiler data, along with sediment gravity-cores collected in 2019. Morphometric and morphological analyses, along with sedimentological analyses, were carried out on submarine landslide deposits to quantify their spatial and temporal distribution throughout the fiord and to evaluate the factors that may have triggered the slope failures.
Combining bathymetric with topographic data from unmanned aerial vehicle imagery, we found that most of these landslide deposits are relatively small (~ 0.08 km2) and are associated with outwash fans and steep fiord sidewalls. However, since most slope failure head scarps lie between the intertidal zone and ~30 m water depth, they could not be mapped, which makes it challenging to determine the triggers of the submarine slope failures. Radiocarbon dating reveals that most of these surficial landslide deposits are younger than 500 years old and that they were most likely triggered at different times. This finding highlights a high recurrence rate of slope failures within the fiord, suggesting that localised triggers are responsible for slope failures within the fiord, as opposed to widespread, seismically induced triggers which do not occur as frequently in the study area. In addition, the elongated morphology of the landslide deposits and the varying degrees of landslide deposit surface roughness supports localised point-source triggers. Since most landslides are associated with subaerial outwash fans and deltas, we suggest that triggers of these relatively frequent submarine landslides within Pangnirtung Fiord include rapid floodwater input, subaerial debris flows, and sea-ice loading during low tide.
This research shows that slope failures in a high-latitude fiord are affected by the interaction of numerous subaerial and submarine processes, leading us to speculate that a potential increase in the frequency of subaerial debris flows and river floods due to climate change may increase the recurrence of submarine landslides.
How to cite: Sedore, P., Normandeau, A., and Maselli, V.: Investigating the controls of submarine landslides and associated hazards in Pangnirtung Fiord, Eastern Baffin Island (Nunavut), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13364, https://doi.org/10.5194/egusphere-egu21-13364, 2021.
Please decide on your access
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Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
High-latitude fiords are susceptible to hazardous subaerial and submarine slope failures. Recent investigations have shown that past slope failures in fiords of Greenland and Alaska have generated devastating landslide induced tsunamis. Since coastal communities inhabit these high-latitude fiords, it is critical to understand the slope failure recurrence time, their distribution, potential triggers, and ability to generate tsunamis. In this study, we identified > 50 near-surface submarine landslides in Pangnirtung Fiord, eastern Baffin Island, Nunavut, using multibeam bathymetric and sub-bottom profiler data, along with sediment gravity-cores collected in 2019. Morphometric and morphological analyses, along with sedimentological analyses, were carried out on submarine landslide deposits to quantify their spatial and temporal distribution throughout the fiord and to evaluate the factors that may have triggered the slope failures.
Combining bathymetric with topographic data from unmanned aerial vehicle imagery, we found that most of these landslide deposits are relatively small (~ 0.08 km2) and are associated with outwash fans and steep fiord sidewalls. However, since most slope failure head scarps lie between the intertidal zone and ~30 m water depth, they could not be mapped, which makes it challenging to determine the triggers of the submarine slope failures. Radiocarbon dating reveals that most of these surficial landslide deposits are younger than 500 years old and that they were most likely triggered at different times. This finding highlights a high recurrence rate of slope failures within the fiord, suggesting that localised triggers are responsible for slope failures within the fiord, as opposed to widespread, seismically induced triggers which do not occur as frequently in the study area. In addition, the elongated morphology of the landslide deposits and the varying degrees of landslide deposit surface roughness supports localised point-source triggers. Since most landslides are associated with subaerial outwash fans and deltas, we suggest that triggers of these relatively frequent submarine landslides within Pangnirtung Fiord include rapid floodwater input, subaerial debris flows, and sea-ice loading during low tide.
This research shows that slope failures in a high-latitude fiord are affected by the interaction of numerous subaerial and submarine processes, leading us to speculate that a potential increase in the frequency of subaerial debris flows and river floods due to climate change may increase the recurrence of submarine landslides.
How to cite: Sedore, P., Normandeau, A., and Maselli, V.: Investigating the controls of submarine landslides and associated hazards in Pangnirtung Fiord, Eastern Baffin Island (Nunavut), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13364, https://doi.org/10.5194/egusphere-egu21-13364, 2021.
EGU21-1050 | vPICO presentations | GM6.3
Unveiling the volcanic evolution of the Mohns RidgeHåvard Stubseid, Anders Bjerga, Haflidi Haflidason, and Rolf Birger Pedersen
Volcanic eruptions are far less common along slow-spreading ridges compared to fast-spreading ridges. Consequently, knowledge of the volcanic rejuvenation along close to 1/3 of the global mid-ocean ridges is poorly constrained. To determine the temporal evolution of the rift valley of one of the slowest spreading-ridges in the world, the Mohns Ridge in the Norwegian-Greenland Sea, we have interpreted more than 3000 km of sub-bottom profiles. Sedimentation rates derived from several core locations along the ridge are used to calculate the age of the underlying volcanic crust. Here we present a framework for understanding the geological evolution of rift valleys of slow-spreading ridges using an integrated approach combining geological and geophysical data. The high-resolution dataset acquired using autonomous underwater vehicles, cover more than 50% of the 575 km long Mohns Ridge. The results unravel large variation in sediment thickness inside the central rift area, from exposed basalts to several meters of sediments, within only a few hundreds of meters. Studied sub-bottom profiles reveal active volcanism in the deepest parts of the ridge, areas thought to be inactive, surrounded by significantly older crust covered in meters of sediments. We find that all axial volcanic ridge systems (AVRs) in our area completely renewed their surface within the last 30-50 ka. Detailed volcanological investigation of the central parts of an AVR reveal at least 72 individual eruptions during the last 20 ka ranging in size from 1.2x103 m2 - 2.6 x105 m2. These estimates have been verified with visual observations and sampling using an ROV. Our estimates indicate that more than 230 eruptions are required to renew the surface of an average AVR. Based on the acquired age assessments a volcanic eruption is anticipated to occur approximately every 200 years. Volcanic renewal is a first order control on the lifetime of magmatically driven hydrothermal systems.
How to cite: Stubseid, H., Bjerga, A., Haflidason, H., and Pedersen, R. B.: Unveiling the volcanic evolution of the Mohns Ridge, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1050, https://doi.org/10.5194/egusphere-egu21-1050, 2021.
Volcanic eruptions are far less common along slow-spreading ridges compared to fast-spreading ridges. Consequently, knowledge of the volcanic rejuvenation along close to 1/3 of the global mid-ocean ridges is poorly constrained. To determine the temporal evolution of the rift valley of one of the slowest spreading-ridges in the world, the Mohns Ridge in the Norwegian-Greenland Sea, we have interpreted more than 3000 km of sub-bottom profiles. Sedimentation rates derived from several core locations along the ridge are used to calculate the age of the underlying volcanic crust. Here we present a framework for understanding the geological evolution of rift valleys of slow-spreading ridges using an integrated approach combining geological and geophysical data. The high-resolution dataset acquired using autonomous underwater vehicles, cover more than 50% of the 575 km long Mohns Ridge. The results unravel large variation in sediment thickness inside the central rift area, from exposed basalts to several meters of sediments, within only a few hundreds of meters. Studied sub-bottom profiles reveal active volcanism in the deepest parts of the ridge, areas thought to be inactive, surrounded by significantly older crust covered in meters of sediments. We find that all axial volcanic ridge systems (AVRs) in our area completely renewed their surface within the last 30-50 ka. Detailed volcanological investigation of the central parts of an AVR reveal at least 72 individual eruptions during the last 20 ka ranging in size from 1.2x103 m2 - 2.6 x105 m2. These estimates have been verified with visual observations and sampling using an ROV. Our estimates indicate that more than 230 eruptions are required to renew the surface of an average AVR. Based on the acquired age assessments a volcanic eruption is anticipated to occur approximately every 200 years. Volcanic renewal is a first order control on the lifetime of magmatically driven hydrothermal systems.
How to cite: Stubseid, H., Bjerga, A., Haflidason, H., and Pedersen, R. B.: Unveiling the volcanic evolution of the Mohns Ridge, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1050, https://doi.org/10.5194/egusphere-egu21-1050, 2021.
EGU21-1789 | vPICO presentations | GM6.3
Tectonic ledges at the bottom of Lake LadogaVladimir Anokhin, Dina Dudakova, and Mikhael Dudakov
For the last several years, the Institute of Limnology RAS has been conducting geological and geomorphological studies of the bottom of Lake Ladoga, the largest lake in Europe. Beginning in 2018, these studies began to use underwater photo and video camera, created at INOZ RAS. The use of this new research tool led to the discovery of a number of new facts of the structure of the bottom of Lake Ladoga. In particular, during the 2020 field season, the authors discovered in several areas of Lake Ladoga the existence of underwater subvertical scarps, composed of bedrocks. At the same time, the submarine towing boat stood in one place, and the camera vertically upward from depths of about 100 - 120 meters to depths of 20 - 30 meters. During this entire rise, the camera recorded the bedrock ledge with vertical and even negative angles. No traces of glacier processing were found, which indicates the Holocene age of the found scarps. In 2020, such ledges were found in 3 regions of Lake Ladoga: in a depression near the Pitkyaranta in the northeastern part of the lake, in the Suuri-Viroluoto trench in the northern part of the lake and on the western underwater slope of Valaam Island. A mention of the possibility of the existence of such ledges (up to the first tens of meters in height) in the northern part of Lake Ladoga is found in the works of V.A. Rumyantsev and V.N. Rybakina (2012), A.V. Amantov (2014), Bolshiyanov (2018). M.A.Naumenko, who studied the underwater slope of Valaam Island, considered the maximum angle of this slope to be 60 degrees (2019). We found sub-vertical ledges up to 100 meters high. In addition, these scarps are in spatial relationship with the existing tectonic faults, confirming their significant fault component. The presence of young vertical high ledges at the bottom of Lake Ladoga indicates powerful young tectonic movements in this region.
How to cite: Anokhin, V., Dudakova, D., and Dudakov, M.: Tectonic ledges at the bottom of Lake Ladoga, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1789, https://doi.org/10.5194/egusphere-egu21-1789, 2021.
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For the last several years, the Institute of Limnology RAS has been conducting geological and geomorphological studies of the bottom of Lake Ladoga, the largest lake in Europe. Beginning in 2018, these studies began to use underwater photo and video camera, created at INOZ RAS. The use of this new research tool led to the discovery of a number of new facts of the structure of the bottom of Lake Ladoga. In particular, during the 2020 field season, the authors discovered in several areas of Lake Ladoga the existence of underwater subvertical scarps, composed of bedrocks. At the same time, the submarine towing boat stood in one place, and the camera vertically upward from depths of about 100 - 120 meters to depths of 20 - 30 meters. During this entire rise, the camera recorded the bedrock ledge with vertical and even negative angles. No traces of glacier processing were found, which indicates the Holocene age of the found scarps. In 2020, such ledges were found in 3 regions of Lake Ladoga: in a depression near the Pitkyaranta in the northeastern part of the lake, in the Suuri-Viroluoto trench in the northern part of the lake and on the western underwater slope of Valaam Island. A mention of the possibility of the existence of such ledges (up to the first tens of meters in height) in the northern part of Lake Ladoga is found in the works of V.A. Rumyantsev and V.N. Rybakina (2012), A.V. Amantov (2014), Bolshiyanov (2018). M.A.Naumenko, who studied the underwater slope of Valaam Island, considered the maximum angle of this slope to be 60 degrees (2019). We found sub-vertical ledges up to 100 meters high. In addition, these scarps are in spatial relationship with the existing tectonic faults, confirming their significant fault component. The presence of young vertical high ledges at the bottom of Lake Ladoga indicates powerful young tectonic movements in this region.
How to cite: Anokhin, V., Dudakova, D., and Dudakov, M.: Tectonic ledges at the bottom of Lake Ladoga, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1789, https://doi.org/10.5194/egusphere-egu21-1789, 2021.
EGU21-2118 | vPICO presentations | GM6.3
Evolutionary development and volume balance calculations of the Ana Slide in the Eivissa Channel, Western MediterraneanThore F. Sager, Morelia Urlaub, Pauline Kaminski, Galderic Lastras, Miquel Canals, and Christian Berndt
Submarine landslides are widespread phenomena on continental slopes and act as prime sediment transport processes between shallow and deep marine regions. In addition, they pose significant risk to coastal communities worldwide. Within this study, we focus on the Ana Slide, a relatively small landslide with areal extent of 4.7 km2 located at water depth between 635 – 905 m on the eastern slopes of the Eivissa Channel, western Mediterranean. Predominant sediment types are high-water content, carbonate-dominated hemipelagic deposits susceptible to high pore pressures and liquefaction. The Ana Slide is completely covered by very-high resolution bathymetric and 3D seismic data and additional legacy data, what allows us to perform detailed kinematic analysis of the landslide evolutionary development.
The Ana Slide is characterised by three landslide domains: the 1) evacuational or headwall domain, 2) translational domain, and 3) accumulational or toe domain. While the headwall domain demonstrates classic features of material evacuation and poses as the exclusive source of material within the landslide process, the translational domain is characterised by extensive in-situ remnant blocks which were unaffected during failure. Instead, landslide material from the evacuational domain moved up and over the translational domain. The toe domain exhibits extensive chaotic seismic facies with compressional ridges throughout the deposit and imprinted onto the seafloor.
Even though the toe domain is characterised by extensive chaotic seismic facies, its volume differs significantly from the volume of the evacuated material. Thus, we conclude that the chaotic seismic facies does not represent landslide material. Instead, the in-situ sediment underwent a range of soft-sediment deformation processes. We propose two mechanisms responsible for this deformation: loading- and shearing-induced soft-sediment deformation resulting from rapid deposition of overburden material. Under consideration of the likely elevated pore pressure and liquefaction potential of deposits, these mechanisms lead to the destruction and disturbance of internal reflections.
Our analysis demonstrates the difficulties in distinguishing between actually failed landslide material and deformed but not translated sediment, which may well lead to erroneous landslide volume estimations. Our new model of the evolutionary development of the Ana Slide may well hold for many other submarine landslides globally, the volumes of which could be significantly overestimated.
How to cite: Sager, T. F., Urlaub, M., Kaminski, P., Lastras, G., Canals, M., and Berndt, C.: Evolutionary development and volume balance calculations of the Ana Slide in the Eivissa Channel, Western Mediterranean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2118, https://doi.org/10.5194/egusphere-egu21-2118, 2021.
Submarine landslides are widespread phenomena on continental slopes and act as prime sediment transport processes between shallow and deep marine regions. In addition, they pose significant risk to coastal communities worldwide. Within this study, we focus on the Ana Slide, a relatively small landslide with areal extent of 4.7 km2 located at water depth between 635 – 905 m on the eastern slopes of the Eivissa Channel, western Mediterranean. Predominant sediment types are high-water content, carbonate-dominated hemipelagic deposits susceptible to high pore pressures and liquefaction. The Ana Slide is completely covered by very-high resolution bathymetric and 3D seismic data and additional legacy data, what allows us to perform detailed kinematic analysis of the landslide evolutionary development.
The Ana Slide is characterised by three landslide domains: the 1) evacuational or headwall domain, 2) translational domain, and 3) accumulational or toe domain. While the headwall domain demonstrates classic features of material evacuation and poses as the exclusive source of material within the landslide process, the translational domain is characterised by extensive in-situ remnant blocks which were unaffected during failure. Instead, landslide material from the evacuational domain moved up and over the translational domain. The toe domain exhibits extensive chaotic seismic facies with compressional ridges throughout the deposit and imprinted onto the seafloor.
Even though the toe domain is characterised by extensive chaotic seismic facies, its volume differs significantly from the volume of the evacuated material. Thus, we conclude that the chaotic seismic facies does not represent landslide material. Instead, the in-situ sediment underwent a range of soft-sediment deformation processes. We propose two mechanisms responsible for this deformation: loading- and shearing-induced soft-sediment deformation resulting from rapid deposition of overburden material. Under consideration of the likely elevated pore pressure and liquefaction potential of deposits, these mechanisms lead to the destruction and disturbance of internal reflections.
Our analysis demonstrates the difficulties in distinguishing between actually failed landslide material and deformed but not translated sediment, which may well lead to erroneous landslide volume estimations. Our new model of the evolutionary development of the Ana Slide may well hold for many other submarine landslides globally, the volumes of which could be significantly overestimated.
How to cite: Sager, T. F., Urlaub, M., Kaminski, P., Lastras, G., Canals, M., and Berndt, C.: Evolutionary development and volume balance calculations of the Ana Slide in the Eivissa Channel, Western Mediterranean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2118, https://doi.org/10.5194/egusphere-egu21-2118, 2021.
EGU21-12286 | vPICO presentations | GM6.3
Short-term evolution of submarine canyon head morphologies in the NW Mediterranean: Blanes and Cap de Creus canyonsCecilia Cabrera, Ruth Durán, Pere Puig, Jorge Guillén, Araceli Muñoz, Montse Demestre, and Albert Palanques
Submarine canyons are morphological features found along continental margins that play a key role channeling and connecting sediment from continental shelves to the abyssal plains. The current morphological characterization of the Blanes and Cap de Creus canyon heads, located on the Catalan continental margin (NW Mediterranean Sea), has been recently conducted during the CRIMA cruise in September 2020 using high-resolution (4 m grid size) multibeam bathymetry data. These data have been compared with a previous dataset collected in 2004 during the ESPACE project to evaluate the morphological changes during this 16-year interval. Since these canyon heads are located at shallow water depths and at short distances from the shoreline, their short-term evolution is related to the sediment dynamics on the continental shelf.
A large-scale change in the seafloor morphology was observed in the Blanes canyon head, indicating the prevalence of erosion in the western canyon rim and non-deposition in the eastern rim. In the Cap de Creus canyon head, the excavation of pre-existing erosive structures was also evidenced in the southwestern canyon rim. These changes mainly happen in the area where the shelf is narrower, which coincide with the main zone of dense water advection along the shelf and toward the canyon interior. The different small-scale morphological evolution between both canyon heads seems to be related to the local geological characteristic of the subsurface deposits of the continental shelf. The Blanes canyon head incises a succession of relict (Holocene) sediment bodies that can act as a source of erodible sediments to the canyon, mainly during strong storms. The continental shelf in the vicinity of the Cap de Creus canyon head, however, is characterized by a rocky substratum (Paleozoic) with a limited sediment coverage and numerous erosive features that evidence relative sand starvation. This creates a greater erosive resistance, although the erosive character of strong storms and major dense-shelf water cascading events occurring during the studied time interval is evident. Additionally, small changes in the shelf bedforms indicate that such high-energetic oceanographic processes also modify the fine-scale seafloor morphology.
These results reveal that both submarine canyon heads are dynamic and sensitive to oceanographic processes that enhance the erosion and transport of sediment from the shelf into the canyon, particularly during energetic storms and dense shelf water cascading events. Nevertheless, their small-scale evolution seems to be closely related to the type of geological substrate of the shelf on which they are developing.
This study has received funding from the ABRIC (RTI2018-096434-B-I00) and CRIMA (RTI2018-095770-B-I00) Spanish Research Projects, the European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No. 867471 and the Generalitat de Catalunya (2017 SGR-663 and -1588). This work is contributing to the ICM’s ‘Center of Excellence’ Severo Ochoa (CEX2019-000928-S). The authors thank the Secretaría General de Pesca and Tragsa for the 2004 ESPACE Project dataset.
How to cite: Cabrera, C., Durán, R., Puig, P., Guillén, J., Muñoz, A., Demestre, M., and Palanques, A.: Short-term evolution of submarine canyon head morphologies in the NW Mediterranean: Blanes and Cap de Creus canyons, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12286, https://doi.org/10.5194/egusphere-egu21-12286, 2021.
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Submarine canyons are morphological features found along continental margins that play a key role channeling and connecting sediment from continental shelves to the abyssal plains. The current morphological characterization of the Blanes and Cap de Creus canyon heads, located on the Catalan continental margin (NW Mediterranean Sea), has been recently conducted during the CRIMA cruise in September 2020 using high-resolution (4 m grid size) multibeam bathymetry data. These data have been compared with a previous dataset collected in 2004 during the ESPACE project to evaluate the morphological changes during this 16-year interval. Since these canyon heads are located at shallow water depths and at short distances from the shoreline, their short-term evolution is related to the sediment dynamics on the continental shelf.
A large-scale change in the seafloor morphology was observed in the Blanes canyon head, indicating the prevalence of erosion in the western canyon rim and non-deposition in the eastern rim. In the Cap de Creus canyon head, the excavation of pre-existing erosive structures was also evidenced in the southwestern canyon rim. These changes mainly happen in the area where the shelf is narrower, which coincide with the main zone of dense water advection along the shelf and toward the canyon interior. The different small-scale morphological evolution between both canyon heads seems to be related to the local geological characteristic of the subsurface deposits of the continental shelf. The Blanes canyon head incises a succession of relict (Holocene) sediment bodies that can act as a source of erodible sediments to the canyon, mainly during strong storms. The continental shelf in the vicinity of the Cap de Creus canyon head, however, is characterized by a rocky substratum (Paleozoic) with a limited sediment coverage and numerous erosive features that evidence relative sand starvation. This creates a greater erosive resistance, although the erosive character of strong storms and major dense-shelf water cascading events occurring during the studied time interval is evident. Additionally, small changes in the shelf bedforms indicate that such high-energetic oceanographic processes also modify the fine-scale seafloor morphology.
These results reveal that both submarine canyon heads are dynamic and sensitive to oceanographic processes that enhance the erosion and transport of sediment from the shelf into the canyon, particularly during energetic storms and dense shelf water cascading events. Nevertheless, their small-scale evolution seems to be closely related to the type of geological substrate of the shelf on which they are developing.
This study has received funding from the ABRIC (RTI2018-096434-B-I00) and CRIMA (RTI2018-095770-B-I00) Spanish Research Projects, the European Union's Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No. 867471 and the Generalitat de Catalunya (2017 SGR-663 and -1588). This work is contributing to the ICM’s ‘Center of Excellence’ Severo Ochoa (CEX2019-000928-S). The authors thank the Secretaría General de Pesca and Tragsa for the 2004 ESPACE Project dataset.
How to cite: Cabrera, C., Durán, R., Puig, P., Guillén, J., Muñoz, A., Demestre, M., and Palanques, A.: Short-term evolution of submarine canyon head morphologies in the NW Mediterranean: Blanes and Cap de Creus canyons, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12286, https://doi.org/10.5194/egusphere-egu21-12286, 2021.
EGU21-2731 | vPICO presentations | GM6.3 | Highlight
Micro-bathymetric mapping of the North Alfeo strike-slip fault (offshore Catania Sicily): preliminary results from the FocusX1 expeditionArnaud Gaillot, Marc-André Gutscher, Shane Murphy, and Frauke Klingelhoefer
In October 2020, during the marine expedition FocusX1 onboard the research vessel PourquoiPas? microbathymetric mapping was performed using the ROV Victor6000. The main goal was to map the seafloor expression of the North Alfeo fault and select the best path for deployment of a 6-km long fiber optic strain cable designed to monitor movement along the fault and the deployment sites for 8 geodetic stations.
Bathymetric data were collected through a Reson Seabat 7125 multibeam echosounder (400 kHz). ROV navigation data were processed using DelphINS, resulting in an optimal merging of navigation sensors (GPS, USBL, DVL, pressure). The MBES data processing (GLOBE software) mainly consisted in estimating and correcting static angular offsets, applying actual in-situ sound speed profile, and finally performing an automatical and manual soundings filtering.
The resulting bathymetric grid spans a region of roughly 3 km x 1.5 km, with a 1m cell size, and allows us to identify a variety of morphological features:
1 - a set of narrow, linear, E-W oriented gulleys, all parallel (not merging/branching) on a regional E dipping 5-15° slope
2 - a striking, continuous curvi-linear feature, which is interpreted as the primary surface expression of the fault.The fault morphology changes from a smooth less than 10 m depression in the NW to a up to 10-20m high scarp with slopes of 20-30°, and locally sub-vertical cliff faces.
3 - a local bathymetric plateau (mesa like feature) with a gently E-dipping summit region, showing signs of eastward sliding / rafting tectonics, indicated by N-S oriented gashes/depressions.
The 3-km long segment of the fault covered by our survey includes the mesa-like bathymetric high (at the NW extremity) interpreted as a transpressional pop-up feature and an elongated, fault bounded trough (at the SE extremity) interpreted as a transtensional pull-apart basin. Video-camera images recorded by ROV Victor6000 from the seafloor provide visual documentation of the fault scarp and seafloor morphology. Future surveys with a sub-bottom profiler and/or HR- seismics can help confirm these interpretations. The ongoing monitoring with the fiber-optic strain cable is being calibrated by a 3-4 year deployment of seafloor geodetic instruments (Canopus acoustic beacons manufactured by iXblue) which started in Oct. 2020, and will allow us to quantify relative displacement across the fault.
How to cite: Gaillot, A., Gutscher, M.-A., Murphy, S., and Klingelhoefer, F.: Micro-bathymetric mapping of the North Alfeo strike-slip fault (offshore Catania Sicily): preliminary results from the FocusX1 expedition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2731, https://doi.org/10.5194/egusphere-egu21-2731, 2021.
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In October 2020, during the marine expedition FocusX1 onboard the research vessel PourquoiPas? microbathymetric mapping was performed using the ROV Victor6000. The main goal was to map the seafloor expression of the North Alfeo fault and select the best path for deployment of a 6-km long fiber optic strain cable designed to monitor movement along the fault and the deployment sites for 8 geodetic stations.
Bathymetric data were collected through a Reson Seabat 7125 multibeam echosounder (400 kHz). ROV navigation data were processed using DelphINS, resulting in an optimal merging of navigation sensors (GPS, USBL, DVL, pressure). The MBES data processing (GLOBE software) mainly consisted in estimating and correcting static angular offsets, applying actual in-situ sound speed profile, and finally performing an automatical and manual soundings filtering.
The resulting bathymetric grid spans a region of roughly 3 km x 1.5 km, with a 1m cell size, and allows us to identify a variety of morphological features:
1 - a set of narrow, linear, E-W oriented gulleys, all parallel (not merging/branching) on a regional E dipping 5-15° slope
2 - a striking, continuous curvi-linear feature, which is interpreted as the primary surface expression of the fault.The fault morphology changes from a smooth less than 10 m depression in the NW to a up to 10-20m high scarp with slopes of 20-30°, and locally sub-vertical cliff faces.
3 - a local bathymetric plateau (mesa like feature) with a gently E-dipping summit region, showing signs of eastward sliding / rafting tectonics, indicated by N-S oriented gashes/depressions.
The 3-km long segment of the fault covered by our survey includes the mesa-like bathymetric high (at the NW extremity) interpreted as a transpressional pop-up feature and an elongated, fault bounded trough (at the SE extremity) interpreted as a transtensional pull-apart basin. Video-camera images recorded by ROV Victor6000 from the seafloor provide visual documentation of the fault scarp and seafloor morphology. Future surveys with a sub-bottom profiler and/or HR- seismics can help confirm these interpretations. The ongoing monitoring with the fiber-optic strain cable is being calibrated by a 3-4 year deployment of seafloor geodetic instruments (Canopus acoustic beacons manufactured by iXblue) which started in Oct. 2020, and will allow us to quantify relative displacement across the fault.
How to cite: Gaillot, A., Gutscher, M.-A., Murphy, S., and Klingelhoefer, F.: Micro-bathymetric mapping of the North Alfeo strike-slip fault (offshore Catania Sicily): preliminary results from the FocusX1 expedition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2731, https://doi.org/10.5194/egusphere-egu21-2731, 2021.
EGU21-660 | vPICO presentations | GM6.3
Bathymetry estimation from altimeter - derived gravity data in the Adriatic SeaLjerka Vrdoljak, Marijan Grgić, and Tomislav Bašić
Bathymetric models representing the topography of the seafloor are an important parameter in almost all maritime related research. Traditional bathymetric shipborne or airborne surveys are cost and/or time consuming, and access to the measured data is mostly limited or expensive. Alternative bathymetric data sources for marine researchers are publicly available bathymetric models whose quality is often unknown and/or uneven. This research presents the study on the bathymetric prediction for the Adriatic Sea from altimetry-derived gravity anomalies and in-situ soundings using the gravity - geologic method (GGM). Bathymetric soundings used to determine the density contrast between seawater and bedrock were derived from nautical charts, EMODnet (European Marine Observation and Data Network) bathymetric grid, and GEBCO (General Bathymetric Chart of the Oceans) One Minute grid. More than 3000 chart soundings distributed across the Adriatic Sea were used to estimate the quality of the predicted bathymetric model as well as the quality of the latest versions of publicly available bathymetric models: DTU10Bat (Technical University of Denmark), GEBCO 2020, EMODnet 2018, ETOPO1, Smith and Sandwell v.19.1, and SRTM (Shuttle Radar Topography Mission) 15+ V.2.1. The results show that the computed model represents an update to bathymetric data in the Adriatic Sea, especially along its eastern coast.
How to cite: Vrdoljak, L., Grgić, M., and Bašić, T.: Bathymetry estimation from altimeter - derived gravity data in the Adriatic Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-660, https://doi.org/10.5194/egusphere-egu21-660, 2021.
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Bathymetric models representing the topography of the seafloor are an important parameter in almost all maritime related research. Traditional bathymetric shipborne or airborne surveys are cost and/or time consuming, and access to the measured data is mostly limited or expensive. Alternative bathymetric data sources for marine researchers are publicly available bathymetric models whose quality is often unknown and/or uneven. This research presents the study on the bathymetric prediction for the Adriatic Sea from altimetry-derived gravity anomalies and in-situ soundings using the gravity - geologic method (GGM). Bathymetric soundings used to determine the density contrast between seawater and bedrock were derived from nautical charts, EMODnet (European Marine Observation and Data Network) bathymetric grid, and GEBCO (General Bathymetric Chart of the Oceans) One Minute grid. More than 3000 chart soundings distributed across the Adriatic Sea were used to estimate the quality of the predicted bathymetric model as well as the quality of the latest versions of publicly available bathymetric models: DTU10Bat (Technical University of Denmark), GEBCO 2020, EMODnet 2018, ETOPO1, Smith and Sandwell v.19.1, and SRTM (Shuttle Radar Topography Mission) 15+ V.2.1. The results show that the computed model represents an update to bathymetric data in the Adriatic Sea, especially along its eastern coast.
How to cite: Vrdoljak, L., Grgić, M., and Bašić, T.: Bathymetry estimation from altimeter - derived gravity data in the Adriatic Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-660, https://doi.org/10.5194/egusphere-egu21-660, 2021.
EGU21-12177 | vPICO presentations | GM6.3
Submerged landscapes of the eastern Adriatic – from the river across the lake all the way to the seaSlobodan Miko and the QMAD Project Team
Submerged paleolandscapes constitute records of long-term paleoenvironmental change, climate, and sea level. To date, there is a very limited knowledge concerning the submerged karst paleolandscapes of the eastern Adriatic coast and the Late Quaternary sedimentary sequences along the eastern part of the Mid Adriatic Deep (MAD). We aim to improve this through the project “Sediments between source and sink during a Late Quaternary eustatic cycle: The Krka and the Mid Adriatic Deep System” (QMAD). The QMAD project supports multidisciplinary research by application of the high-resolution geophysical surveys (multibeam, side-scan sonar and sub-bottom profiler), in combination with sedimentological, petrophysical, geochemical (trace elements and isotopes), micropaleontological (ostracod and foraminifera), mineralogical and aDNA techniques. This suite of analyses will enable tracking of the paleoenvironmental evolution from fluvial/lake to deeper marine environments, on a short transect less than 100 km in length (Lake Prokljan in the Krka River estuary to the eastern part of MAD). The submerged Late Pleistocene and Holocene environments that occur include isolation basins, lagoons, deltas, estuaries, submarine channels and shelf. The continuous marine sedimentation during the Late Quaternary is investigated in the MAD. In the case of the central part of the eastern side of the Adriatic Sea (Krka catchment - MAD) these different environments compose an integrated system; thus, they can’t be analysed separately. The main goals of this project fill the existing gaps in understanding of the climatic and environmental changes, including sea-level related landscape changes and their interplay during the Late Quaternary eustatic cycle. More data on the Pleistocene environments, especially from the region of Krka estuary that was land during the Last Glacial Maximum (LGM), will complete the picture of the evolution and environmental adaptation of Paleolithic humans and their relationship with vegetation changes. Attention is also paid to potential anthropogenic environments, recent sedimentation rates, landscape features and artefacts. All results of the multi-proxy approach applied in this project will eventually be merged into a comprehensive Late Quaternary paleoenvironmental and paleoclimatic reconstruction of the eastern Adriatic landscapes that contribute to the understanding of these changes in the Mediterranean region.
How to cite: Miko, S. and the QMAD Project Team: Submerged landscapes of the eastern Adriatic – from the river across the lake all the way to the sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12177, https://doi.org/10.5194/egusphere-egu21-12177, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Submerged paleolandscapes constitute records of long-term paleoenvironmental change, climate, and sea level. To date, there is a very limited knowledge concerning the submerged karst paleolandscapes of the eastern Adriatic coast and the Late Quaternary sedimentary sequences along the eastern part of the Mid Adriatic Deep (MAD). We aim to improve this through the project “Sediments between source and sink during a Late Quaternary eustatic cycle: The Krka and the Mid Adriatic Deep System” (QMAD). The QMAD project supports multidisciplinary research by application of the high-resolution geophysical surveys (multibeam, side-scan sonar and sub-bottom profiler), in combination with sedimentological, petrophysical, geochemical (trace elements and isotopes), micropaleontological (ostracod and foraminifera), mineralogical and aDNA techniques. This suite of analyses will enable tracking of the paleoenvironmental evolution from fluvial/lake to deeper marine environments, on a short transect less than 100 km in length (Lake Prokljan in the Krka River estuary to the eastern part of MAD). The submerged Late Pleistocene and Holocene environments that occur include isolation basins, lagoons, deltas, estuaries, submarine channels and shelf. The continuous marine sedimentation during the Late Quaternary is investigated in the MAD. In the case of the central part of the eastern side of the Adriatic Sea (Krka catchment - MAD) these different environments compose an integrated system; thus, they can’t be analysed separately. The main goals of this project fill the existing gaps in understanding of the climatic and environmental changes, including sea-level related landscape changes and their interplay during the Late Quaternary eustatic cycle. More data on the Pleistocene environments, especially from the region of Krka estuary that was land during the Last Glacial Maximum (LGM), will complete the picture of the evolution and environmental adaptation of Paleolithic humans and their relationship with vegetation changes. Attention is also paid to potential anthropogenic environments, recent sedimentation rates, landscape features and artefacts. All results of the multi-proxy approach applied in this project will eventually be merged into a comprehensive Late Quaternary paleoenvironmental and paleoclimatic reconstruction of the eastern Adriatic landscapes that contribute to the understanding of these changes in the Mediterranean region.
How to cite: Miko, S. and the QMAD Project Team: Submerged landscapes of the eastern Adriatic – from the river across the lake all the way to the sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12177, https://doi.org/10.5194/egusphere-egu21-12177, 2021.
EGU21-10987 | vPICO presentations | GM6.3
A trail of crumbs: ancient geomorphological indicators of past sea-level rise in the Northern Adriatic Sea (Italy)Livio Ronchi, Alessandro Fontana, and Annamaria Correggiari
The reconstruction of timing and modes of the last marine transgression is often hampered by the scarceness of available indicators, which is caused by bad preservation, lack of formation or difficult accessibility.
This is particularly true for the first period of the Holocene, between 7 ka and 11 ka cal, when the rate of transgression was high (hence little to absent formation of possible indicators) and the sea level was placed below ca. -20 m MSL (hence scarce accessibility).
Shoreline deposits and erosional landforms have long been recognized as geomorphological indicators of past sea levels. Such indicators (e.g. beach ridges, tidal notches) can be both submerged or exposed due to RSL variations of coastal progradation.
A major group of potential indicators which, up to date, is largely underrepresented, is constituted by paleo tidal inlets. Being excavated up to several meters below the surrounding lagoon and filled during the migration or deactivation of the inlet, such landforms may represent outstanding archives with a potentially high chance of preservation from erosion. Paleo tidal inlets can be easily recognized and cataloged through shallow sub-bottom profiling methods.
The analysis of almost 7000 km of high resolution seismic profiles collected in the northern Adriatic Sea allowed to recognized almost 100 paleo tidal inlets dating to the early Holocene, which constitute the only widespread witnesses of the post-LGM marine transgression in the area. Paleo tidal inlets are essential features to the paleo-geographic and -environmental reconstruction and provide new data to constrain the position of the transgressive coastlines. The presence of widespread lagoon environments during a phase of strong RSL rise comes from the interplay between sediment dispersal operated by the main fluvial actors of the area and phases of slowdown of the RSL rise. This study sheds light on the phenomena affecting coastal plains in response to RSL rise and constitutes the first report of an extensive distribution of paleo tidal inlets on a regional scale.
How to cite: Ronchi, L., Fontana, A., and Correggiari, A.: A trail of crumbs: ancient geomorphological indicators of past sea-level rise in the Northern Adriatic Sea (Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10987, https://doi.org/10.5194/egusphere-egu21-10987, 2021.
The reconstruction of timing and modes of the last marine transgression is often hampered by the scarceness of available indicators, which is caused by bad preservation, lack of formation or difficult accessibility.
This is particularly true for the first period of the Holocene, between 7 ka and 11 ka cal, when the rate of transgression was high (hence little to absent formation of possible indicators) and the sea level was placed below ca. -20 m MSL (hence scarce accessibility).
Shoreline deposits and erosional landforms have long been recognized as geomorphological indicators of past sea levels. Such indicators (e.g. beach ridges, tidal notches) can be both submerged or exposed due to RSL variations of coastal progradation.
A major group of potential indicators which, up to date, is largely underrepresented, is constituted by paleo tidal inlets. Being excavated up to several meters below the surrounding lagoon and filled during the migration or deactivation of the inlet, such landforms may represent outstanding archives with a potentially high chance of preservation from erosion. Paleo tidal inlets can be easily recognized and cataloged through shallow sub-bottom profiling methods.
The analysis of almost 7000 km of high resolution seismic profiles collected in the northern Adriatic Sea allowed to recognized almost 100 paleo tidal inlets dating to the early Holocene, which constitute the only widespread witnesses of the post-LGM marine transgression in the area. Paleo tidal inlets are essential features to the paleo-geographic and -environmental reconstruction and provide new data to constrain the position of the transgressive coastlines. The presence of widespread lagoon environments during a phase of strong RSL rise comes from the interplay between sediment dispersal operated by the main fluvial actors of the area and phases of slowdown of the RSL rise. This study sheds light on the phenomena affecting coastal plains in response to RSL rise and constitutes the first report of an extensive distribution of paleo tidal inlets on a regional scale.
How to cite: Ronchi, L., Fontana, A., and Correggiari, A.: A trail of crumbs: ancient geomorphological indicators of past sea-level rise in the Northern Adriatic Sea (Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10987, https://doi.org/10.5194/egusphere-egu21-10987, 2021.
EGU21-7220 | vPICO presentations | GM6.3
New insights into sedimentary processes and related morphologies in tidal straits: the case of the Rio-Antirio Sill (Greece)Romain Rubi, Aurélia Hubert-Ferrari, Elias Fakiris, Dimitris Christodoulou, Xenophon Dimas, Maria Geraga, and George Papatheodorou
Straits are crossed by marine currents that are amplified due to the water constriction. These nearshore high-velocity flows are problematic for offshore infrastructures (bridge pillars, cables, pipelines etc), but constitute an under-estimated carbon-free kinematic energy source. Most of the straits are dominated by tidal currents which flow axially to the seaway, with reversal directions and phase difference between the two interlinked basins. These tidal currents interplay with: (i) sediment sources that also includes in situ carbonate production and deltas, (ii) tectonic activity, and (iii) inherited lowstand features, all shaping the sea floor into complex geomorphologies. Previous studies have highlighted a common tidal-strait depositional model with a strait-center zone in erosion and on each side a dune-bedded strait zone with 3D and 2D tidal dunes and tidal ripples.
Here, we present an alternative tidal-strait model based on an interdisciplinary approach using high-resolution geophysical and oceanographical data to better constrain the processes acting at the sea floor. We focus on the Rion-Antirion strait in Greece which controls the connection between the Gulf of Corinth and the Mediterranean Sea. Based on high-resolution multibeam bathymetry (MBES) over an area of 211km2, we identify and quantify the morphologies by extracting bathymetric swath profiles. These results are integrated with currents data (ADCP) and CTD profiles. In addition, we use high-resolution Chirp subbottom profiles and high-resolution sparker seismic reflection profiles to document the stratigraphy and morphology of the sedimentary beds and erosional features. To complete this dataset, we use a towed underwater camera to image the sea-floor.
We define three zones, each characterized by common hydrodynamics, bedforms and morpho-bathymetric features which reveal an asymmetric strait. (1) The western zone is dominated by tectonics with salt diapirism and faults which interact with bottom currents to form erosional pools and ridge systems. (2) The strait center zone displays abrasion surfaces which consists on a rough rock-paved plateau surface encrusted by living red corals and sponges. Moreover, a moat cuts this plateau that localizes the sill at its eastern tip. This strait center area is dominated by inherited hard-ground fluviatile deposits which are abraded by bidirectional tidal-currents. (3) The eastern zone shows a deeper bathymetry with smoother features. The sediments are veneered on slopes forming plastered drifts and spits while the basin axis presents large chutes and pools. The bottom-currents in this zone, are related to internal tides from the Gulf of Corinth that are delayed with respect to the tidal currents. These internal-tide currents (3m/s) are three times faster than the oceanic tidal-currents in the strait (1m/s).
In conclusion, we document a tidal-strait system, which is interacting with active tectonics, and internal-tides along its axis. In results, Rion strait displays complex bathymetric features without any 3D or 2D tidal dunes. Thus, it provides a new end member to the tidal-strait depositional model. This end member is characterized by a re-localization of the erosion, bypass and deposition. It illustrates the key role of internal tides for straits located at the boundary between a confined deep-basin and the open-sea.
How to cite: Rubi, R., Hubert-Ferrari, A., Fakiris, E., Christodoulou, D., Dimas, X., Geraga, M., and Papatheodorou, G.: New insights into sedimentary processes and related morphologies in tidal straits: the case of the Rio-Antirio Sill (Greece), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7220, https://doi.org/10.5194/egusphere-egu21-7220, 2021.
Straits are crossed by marine currents that are amplified due to the water constriction. These nearshore high-velocity flows are problematic for offshore infrastructures (bridge pillars, cables, pipelines etc), but constitute an under-estimated carbon-free kinematic energy source. Most of the straits are dominated by tidal currents which flow axially to the seaway, with reversal directions and phase difference between the two interlinked basins. These tidal currents interplay with: (i) sediment sources that also includes in situ carbonate production and deltas, (ii) tectonic activity, and (iii) inherited lowstand features, all shaping the sea floor into complex geomorphologies. Previous studies have highlighted a common tidal-strait depositional model with a strait-center zone in erosion and on each side a dune-bedded strait zone with 3D and 2D tidal dunes and tidal ripples.
Here, we present an alternative tidal-strait model based on an interdisciplinary approach using high-resolution geophysical and oceanographical data to better constrain the processes acting at the sea floor. We focus on the Rion-Antirion strait in Greece which controls the connection between the Gulf of Corinth and the Mediterranean Sea. Based on high-resolution multibeam bathymetry (MBES) over an area of 211km2, we identify and quantify the morphologies by extracting bathymetric swath profiles. These results are integrated with currents data (ADCP) and CTD profiles. In addition, we use high-resolution Chirp subbottom profiles and high-resolution sparker seismic reflection profiles to document the stratigraphy and morphology of the sedimentary beds and erosional features. To complete this dataset, we use a towed underwater camera to image the sea-floor.
We define three zones, each characterized by common hydrodynamics, bedforms and morpho-bathymetric features which reveal an asymmetric strait. (1) The western zone is dominated by tectonics with salt diapirism and faults which interact with bottom currents to form erosional pools and ridge systems. (2) The strait center zone displays abrasion surfaces which consists on a rough rock-paved plateau surface encrusted by living red corals and sponges. Moreover, a moat cuts this plateau that localizes the sill at its eastern tip. This strait center area is dominated by inherited hard-ground fluviatile deposits which are abraded by bidirectional tidal-currents. (3) The eastern zone shows a deeper bathymetry with smoother features. The sediments are veneered on slopes forming plastered drifts and spits while the basin axis presents large chutes and pools. The bottom-currents in this zone, are related to internal tides from the Gulf of Corinth that are delayed with respect to the tidal currents. These internal-tide currents (3m/s) are three times faster than the oceanic tidal-currents in the strait (1m/s).
In conclusion, we document a tidal-strait system, which is interacting with active tectonics, and internal-tides along its axis. In results, Rion strait displays complex bathymetric features without any 3D or 2D tidal dunes. Thus, it provides a new end member to the tidal-strait depositional model. This end member is characterized by a re-localization of the erosion, bypass and deposition. It illustrates the key role of internal tides for straits located at the boundary between a confined deep-basin and the open-sea.
How to cite: Rubi, R., Hubert-Ferrari, A., Fakiris, E., Christodoulou, D., Dimas, X., Geraga, M., and Papatheodorou, G.: New insights into sedimentary processes and related morphologies in tidal straits: the case of the Rio-Antirio Sill (Greece), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7220, https://doi.org/10.5194/egusphere-egu21-7220, 2021.
EGU21-16246 | vPICO presentations | GM6.3
3-D Architecture and the Upper Miocene-Pliocene Depositional Pattern of the Gulf of İzmir by Reflection TomographyZehra Altan, Neslihan Ocakoğlu, and Gualtiero Böhm
The ongoing tectonism in the Western Anatolia creates N-S extension and counter-clockwise rotational motion along the right-lateral North Anatolian fault (NAF) and left-lateral East Anatolian Fault (EAF). This continental extension creates predominantly E-W extending onshore grabens rarely NE to SW and NW to SE trending onshore/offshore grabens characterised by the intense seismic activity, high heat flow associated with volcanism, crustal thinning and geothermal systems. Our study area, the gulf of İzmir, has an “L” shape composing of an E-W oriented inner bay from İzmir to Urla and incompatibly NNW-SSE oriented outer bay between offshore Foça and Karaburun. It is located at the intersection of the E-W oriented onshore Gediz Graben and NE-SW oriented onshore Bakırçay graben. Geophysical evidence for fluid discharge and subsurface gas-associated structures such as gas chimneys, pockmarks, mud diapirs and acoustic turbidity zones have been detected in the inner and outer parts of the Gulf of İzmir by the previous studies. For this reason, the Gulf of İzmir and the adjacent onshore grabens are areas of great interest for further study of the region.
In this study, the 3-D stratigraphic architecture (up to 1.5 km) and the Upper Miocene-Pliocene depositional settings of the Gulf of İzmir reconstructed by reflection tomography for the first time. Three seismic stratigraphic units, labelled SSU1, SSU2 and SSU3 from bottom to top, were identified by their bounding unconformity surfaces (H1-H5). We have subdivided unit SSU1 into three subunits named SSU1c-SSU1a. The acoustic basement associated with SSU3 is likely tied to the Lower-Middle Miocene Yuntdağ Volcanics consisting of tuffs, sandstones, limestones and volcanics. The upper surface of SSU3 (horizon H5) is marked as a major regional unconformity representing a basin-ridge morphology. The first rocks deposited on top of acoustic basement (SSU2) correspond to the sandstones, limestones, volcanics and shales of the Bozköy Formation and the limestones of the Ularca Formation, dating from the Late Miocene to the Pliocene. The top of SSU2 (horizon H4) is interpreted as another unconformity and is correlated with the Pliocene unconformity. Above that, part of the Bayramiç Formation (SSU1c) is dated as Quaternary, consisting of conglomerates at the base overlain by sandstones and shales above. On top of the SSU1c are two further sub-units of the Bayramiç Formation separated by horizons H3 and H2. SSU1b consists of a similar sequence of conglomerates, sandstones and shales; SSU1a consists of Quaternary sandstones. Following the tomographic analysis, the isopach map of the Plio-Quaternary sediment fills was derived from the depth of interpreted horizons calculated using tomographic interval velocities. According to the isopach map of the sedimentary fills, thickness abruptly decreasing from NW to SE. The maximum thickness of total sedimentary succession is ~1400 m in the NW, whereas the thickness decreases through the west, east (up to ~450 m) and the southeastern flank of the basin, reaching ~150 m forming a ridge. A few local lateral velocity variations were identified within the Plio-Quaternary sedimentary succession associated with faults, fluid escape and shallow gas occurrences or a combination of these.
How to cite: Altan, Z., Ocakoğlu, N., and Böhm, G.: 3-D Architecture and the Upper Miocene-Pliocene Depositional Pattern of the Gulf of İzmir by Reflection Tomography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16246, https://doi.org/10.5194/egusphere-egu21-16246, 2021.
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The ongoing tectonism in the Western Anatolia creates N-S extension and counter-clockwise rotational motion along the right-lateral North Anatolian fault (NAF) and left-lateral East Anatolian Fault (EAF). This continental extension creates predominantly E-W extending onshore grabens rarely NE to SW and NW to SE trending onshore/offshore grabens characterised by the intense seismic activity, high heat flow associated with volcanism, crustal thinning and geothermal systems. Our study area, the gulf of İzmir, has an “L” shape composing of an E-W oriented inner bay from İzmir to Urla and incompatibly NNW-SSE oriented outer bay between offshore Foça and Karaburun. It is located at the intersection of the E-W oriented onshore Gediz Graben and NE-SW oriented onshore Bakırçay graben. Geophysical evidence for fluid discharge and subsurface gas-associated structures such as gas chimneys, pockmarks, mud diapirs and acoustic turbidity zones have been detected in the inner and outer parts of the Gulf of İzmir by the previous studies. For this reason, the Gulf of İzmir and the adjacent onshore grabens are areas of great interest for further study of the region.
In this study, the 3-D stratigraphic architecture (up to 1.5 km) and the Upper Miocene-Pliocene depositional settings of the Gulf of İzmir reconstructed by reflection tomography for the first time. Three seismic stratigraphic units, labelled SSU1, SSU2 and SSU3 from bottom to top, were identified by their bounding unconformity surfaces (H1-H5). We have subdivided unit SSU1 into three subunits named SSU1c-SSU1a. The acoustic basement associated with SSU3 is likely tied to the Lower-Middle Miocene Yuntdağ Volcanics consisting of tuffs, sandstones, limestones and volcanics. The upper surface of SSU3 (horizon H5) is marked as a major regional unconformity representing a basin-ridge morphology. The first rocks deposited on top of acoustic basement (SSU2) correspond to the sandstones, limestones, volcanics and shales of the Bozköy Formation and the limestones of the Ularca Formation, dating from the Late Miocene to the Pliocene. The top of SSU2 (horizon H4) is interpreted as another unconformity and is correlated with the Pliocene unconformity. Above that, part of the Bayramiç Formation (SSU1c) is dated as Quaternary, consisting of conglomerates at the base overlain by sandstones and shales above. On top of the SSU1c are two further sub-units of the Bayramiç Formation separated by horizons H3 and H2. SSU1b consists of a similar sequence of conglomerates, sandstones and shales; SSU1a consists of Quaternary sandstones. Following the tomographic analysis, the isopach map of the Plio-Quaternary sediment fills was derived from the depth of interpreted horizons calculated using tomographic interval velocities. According to the isopach map of the sedimentary fills, thickness abruptly decreasing from NW to SE. The maximum thickness of total sedimentary succession is ~1400 m in the NW, whereas the thickness decreases through the west, east (up to ~450 m) and the southeastern flank of the basin, reaching ~150 m forming a ridge. A few local lateral velocity variations were identified within the Plio-Quaternary sedimentary succession associated with faults, fluid escape and shallow gas occurrences or a combination of these.
How to cite: Altan, Z., Ocakoğlu, N., and Böhm, G.: 3-D Architecture and the Upper Miocene-Pliocene Depositional Pattern of the Gulf of İzmir by Reflection Tomography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16246, https://doi.org/10.5194/egusphere-egu21-16246, 2021.
EGU21-14327 | vPICO presentations | GM6.3
Sentinel-2 mission Contribution for Supporting Bathymetric layers of SAFAGA coastal zone, EgyptRamez Saeed, Saad Abdelrahman, Andrea Scozari, and Abdelazim Negm
ABSTRACT
With the fast and highly growing demand for all possible ways of remote work as a result of COVID19 pandemic, new technologies using Satellite data were highly encouraged for multidisciplinary applications in different fields such as; agriculture, climate change, environment, coastal management, maritime, security and Blue Economy.
This work supports applying Satellite Derived Bathymetry (SDB) with the available low-cost multispectral satellite imagery applications, instruments and readily accessible data for different areas with only their benthic parameters, water characteristics and atmospheric conditions. The main goal of this work is to derive bathymetric data needed for different hydrographic applications, such as: nautical charting, coastal engineering, water quality monitoring, sediment movement monitoring and supporting both green carbon and marine data science. Also, this work proposes and assesses a SDB procedure that makes use of publicly-available multispectral satellite images (Sentinel2 MSI) and applies algorithms available in the SNAP software package for extracting bathymetry and supporting bathymetric layers against highly expensive traditional in-situ hydrographic surveys. The procedure was applied at SAFAGA harbor area, located south of Hurghada at (26°44′N, 33°56′E), on the Egyptian Red Sea coast. SAFAGA controls important maritime traffic line in Red Sea such as (Safaga – Deba, Saudi Arabia) maritime cruises. SAFAGA depths change between 6 m to 22m surrounded by many shoal batches and confined waters that largely affect maritime safety of navigation. Therefore, there is always a high demand for updated nautical charts which this work supports. The outcome of this work provides and fulfils those demands with bathymetric layers data for the approach channel and harbour usage bands electronic nautical chart of SAFAGA with reasonable accuracies. The coefficient of determination (R2) differs between 0.42 to 0.71 after applying water column correction by Lyzenga algorithm and deriving bathymetric data depending on reflectance /radiance of optical imagery collected by sentinel2 missions with in-situ depth data values relationship by Stumpf equation. The adopted approach proved to give highly reasonable results that could be used in nautical charts compilation. Similar methodologies could be applied to inland water bodies. This study is part of the MSc Thesis of the first author and is in the framework of a bilateral project between ASRT of Egypt and CNR of Italy which is still running.
Keywords: Algorithm, Bathymetry, Sentinel 2, nautical charting, Safaga port, satellite imagery, water depth, Egypt.
How to cite: Saeed, R., Abdelrahman, S., Scozari, A., and Negm, A.: Sentinel-2 mission Contribution for Supporting Bathymetric layers of SAFAGA coastal zone, Egypt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14327, https://doi.org/10.5194/egusphere-egu21-14327, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
ABSTRACT
With the fast and highly growing demand for all possible ways of remote work as a result of COVID19 pandemic, new technologies using Satellite data were highly encouraged for multidisciplinary applications in different fields such as; agriculture, climate change, environment, coastal management, maritime, security and Blue Economy.
This work supports applying Satellite Derived Bathymetry (SDB) with the available low-cost multispectral satellite imagery applications, instruments and readily accessible data for different areas with only their benthic parameters, water characteristics and atmospheric conditions. The main goal of this work is to derive bathymetric data needed for different hydrographic applications, such as: nautical charting, coastal engineering, water quality monitoring, sediment movement monitoring and supporting both green carbon and marine data science. Also, this work proposes and assesses a SDB procedure that makes use of publicly-available multispectral satellite images (Sentinel2 MSI) and applies algorithms available in the SNAP software package for extracting bathymetry and supporting bathymetric layers against highly expensive traditional in-situ hydrographic surveys. The procedure was applied at SAFAGA harbor area, located south of Hurghada at (26°44′N, 33°56′E), on the Egyptian Red Sea coast. SAFAGA controls important maritime traffic line in Red Sea such as (Safaga – Deba, Saudi Arabia) maritime cruises. SAFAGA depths change between 6 m to 22m surrounded by many shoal batches and confined waters that largely affect maritime safety of navigation. Therefore, there is always a high demand for updated nautical charts which this work supports. The outcome of this work provides and fulfils those demands with bathymetric layers data for the approach channel and harbour usage bands electronic nautical chart of SAFAGA with reasonable accuracies. The coefficient of determination (R2) differs between 0.42 to 0.71 after applying water column correction by Lyzenga algorithm and deriving bathymetric data depending on reflectance /radiance of optical imagery collected by sentinel2 missions with in-situ depth data values relationship by Stumpf equation. The adopted approach proved to give highly reasonable results that could be used in nautical charts compilation. Similar methodologies could be applied to inland water bodies. This study is part of the MSc Thesis of the first author and is in the framework of a bilateral project between ASRT of Egypt and CNR of Italy which is still running.
Keywords: Algorithm, Bathymetry, Sentinel 2, nautical charting, Safaga port, satellite imagery, water depth, Egypt.
How to cite: Saeed, R., Abdelrahman, S., Scozari, A., and Negm, A.: Sentinel-2 mission Contribution for Supporting Bathymetric layers of SAFAGA coastal zone, Egypt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14327, https://doi.org/10.5194/egusphere-egu21-14327, 2021.
EGU21-16421 | vPICO presentations | GM6.3
The contribution of acoustic seafloor mapping techniques to outlining coral reef geomorphology: A case study in the Republic of Maldives (Magoodhoo Reef – Maldivian Archipelago)Alessandra Savini, Fabio Marchese, Luca Fallati, Sebastian Krastel, Aaron Micallef, Luca Saponari, Francesca Dajma, Gabriele Mandelli, and Paolo Galli
Optical remote sensing data coupled with a dense network of field surveys have historically played a crucial role in geomorphological mapping of coral reef environments. Recently this field has undergone a major upgrade thanks to the integration of new advanced methods such as LiDAR, AUV-based and close-range digital photogrammetry and acoustic remote sensing techniques, which are able to investigate the deeper components of this complex geomorphic system. The new detailed maps can produce seamless digital elevation model (DEM) of coral reef environments, by integrating the elevation datasets acquired by the combination of the mentioned survey techniques.
In our work, a harmonised geomorphological map is generated for the Magoodhoo reef, which borders the southwestern discontinuous marginal rim of a subcircular atoll (i.e. Faafu Atoll) of the Maldivian archipelago. In its north-eastern sector the reef consists of a cuspate reef joined to an almost closed ring reef to the south-west, where Magoodhoo Island is located. The map was generated from the analysis of Sentinel data, orthomosaics and 3D optical models generated by the application of SfM techniques to UAV images, as well as bathymetry and backscatter intensity measurements. The latter were collected down to a depth of up to 120 m along the oceanward margin of the atoll's rim, and to a depth of roughly 60 m along the lagoonward margin. Direct observations were also performed using an observational ROV on the forereef and within the lagoon, and video-transects on the reef flat.
The oceanward margin shows steep terraced slopes that reveal a complex history of late Pleistocene/Holocene sea level oscillations, while the backreef slopes (toward the lagoon) are generally more gentle, although at places can show abrupt escarpments and overhangs. The lagoon submarine landscape is distinctly featured by patch reefs of variable shapes (from circular to sub-elongated) and dimensions (from few meters to 30m high). Their distribution is clearly controlled by the surface circulation pattern, regulated by the pass that borders the reef to the west. Towards the deeper edge of the mapped sector of the lagoon floor, where patch reefs are totally absent, intriguing small-scale depressions have been detected instead. The regular circular and concave shape calls for their interpretation as pockmarks, but their origin is still unknow due to the lack of core samples and geochemical analysis in the area. New data are actually needed to precisely outline the sedimentary environments that feature Faafu Atoll and its inner lagoon. Nevertheless, the obtained geomorphological map and the mapped landforms shed new light and a more complete understanding on the processes that drive morphological changes of the entire Magoodhoo reef.
How to cite: Savini, A., Marchese, F., Fallati, L., Krastel, S., Micallef, A., Saponari, L., Dajma, F., Mandelli, G., and Galli, P.: The contribution of acoustic seafloor mapping techniques to outlining coral reef geomorphology: A case study in the Republic of Maldives (Magoodhoo Reef – Maldivian Archipelago), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16421, https://doi.org/10.5194/egusphere-egu21-16421, 2021.
Optical remote sensing data coupled with a dense network of field surveys have historically played a crucial role in geomorphological mapping of coral reef environments. Recently this field has undergone a major upgrade thanks to the integration of new advanced methods such as LiDAR, AUV-based and close-range digital photogrammetry and acoustic remote sensing techniques, which are able to investigate the deeper components of this complex geomorphic system. The new detailed maps can produce seamless digital elevation model (DEM) of coral reef environments, by integrating the elevation datasets acquired by the combination of the mentioned survey techniques.
In our work, a harmonised geomorphological map is generated for the Magoodhoo reef, which borders the southwestern discontinuous marginal rim of a subcircular atoll (i.e. Faafu Atoll) of the Maldivian archipelago. In its north-eastern sector the reef consists of a cuspate reef joined to an almost closed ring reef to the south-west, where Magoodhoo Island is located. The map was generated from the analysis of Sentinel data, orthomosaics and 3D optical models generated by the application of SfM techniques to UAV images, as well as bathymetry and backscatter intensity measurements. The latter were collected down to a depth of up to 120 m along the oceanward margin of the atoll's rim, and to a depth of roughly 60 m along the lagoonward margin. Direct observations were also performed using an observational ROV on the forereef and within the lagoon, and video-transects on the reef flat.
The oceanward margin shows steep terraced slopes that reveal a complex history of late Pleistocene/Holocene sea level oscillations, while the backreef slopes (toward the lagoon) are generally more gentle, although at places can show abrupt escarpments and overhangs. The lagoon submarine landscape is distinctly featured by patch reefs of variable shapes (from circular to sub-elongated) and dimensions (from few meters to 30m high). Their distribution is clearly controlled by the surface circulation pattern, regulated by the pass that borders the reef to the west. Towards the deeper edge of the mapped sector of the lagoon floor, where patch reefs are totally absent, intriguing small-scale depressions have been detected instead. The regular circular and concave shape calls for their interpretation as pockmarks, but their origin is still unknow due to the lack of core samples and geochemical analysis in the area. New data are actually needed to precisely outline the sedimentary environments that feature Faafu Atoll and its inner lagoon. Nevertheless, the obtained geomorphological map and the mapped landforms shed new light and a more complete understanding on the processes that drive morphological changes of the entire Magoodhoo reef.
How to cite: Savini, A., Marchese, F., Fallati, L., Krastel, S., Micallef, A., Saponari, L., Dajma, F., Mandelli, G., and Galli, P.: The contribution of acoustic seafloor mapping techniques to outlining coral reef geomorphology: A case study in the Republic of Maldives (Magoodhoo Reef – Maldivian Archipelago), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16421, https://doi.org/10.5194/egusphere-egu21-16421, 2021.
GM6.4 – Coastal wetlands: Processes, interactions, management
EGU21-14069 | vPICO presentations | GM6.4
Coastal wetland substrate elevation is dynamically related to accommodation space and influenced by sea-level riseKerrylee Rogers and Neil Saintilan
The resilience of coastal wetlands in the fate of sea-level rise is proposed to be related to the combined influence of changes in substrate organic matter volume, mineral sediment volume, auto-compaction of accumulating material and deep subsidence; however, relatively few studies have measured all of these variables. In addition, there is ongoing debate about the suitability of this data for modelling the behaviour of coastal wetlands under anticipated sea-level rise projections as temporal discrepancies in the elevation response of coastal wetlands derived from observational and stratigraphic records exist. To resolve these issues, data derived from a range of techniques sensitive to changes occurring at annual, decadal and century timescales, is presented in the context of available accommodation space, that is, the space in which tidally-borne material can accumulate. Focussing on an embayment in Victoria, Australia, analyses confirm that at annual-decadal timescales, organic matter behaves like a sponge, compressing as the overburden of material accumulates, resulting in auto-compaction that modulates the degree of surface elevation change that occurs as tidally-borne material accumulates. These processes operate concurrently and are influenced by sediment availability, yet vary on the basis of available accommodation space. At longer timescales, the influence of auto-compaction diminishes as organic matter has undergone significant compression and decomposition, yet accumulated material remains proportional to available accommodation space. These analyses confirm that temporal discrepancies in rates of substrate elevation change can be resolved by accounting for the timescale over which processes operate and the influence of sea-level rise on available accommodation space. Accordingly, models should dynamically consider rates of surface elevation change relative to available accommodation space.
How to cite: Rogers, K. and Saintilan, N.: Coastal wetland substrate elevation is dynamically related to accommodation space and influenced by sea-level rise, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14069, https://doi.org/10.5194/egusphere-egu21-14069, 2021.
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The resilience of coastal wetlands in the fate of sea-level rise is proposed to be related to the combined influence of changes in substrate organic matter volume, mineral sediment volume, auto-compaction of accumulating material and deep subsidence; however, relatively few studies have measured all of these variables. In addition, there is ongoing debate about the suitability of this data for modelling the behaviour of coastal wetlands under anticipated sea-level rise projections as temporal discrepancies in the elevation response of coastal wetlands derived from observational and stratigraphic records exist. To resolve these issues, data derived from a range of techniques sensitive to changes occurring at annual, decadal and century timescales, is presented in the context of available accommodation space, that is, the space in which tidally-borne material can accumulate. Focussing on an embayment in Victoria, Australia, analyses confirm that at annual-decadal timescales, organic matter behaves like a sponge, compressing as the overburden of material accumulates, resulting in auto-compaction that modulates the degree of surface elevation change that occurs as tidally-borne material accumulates. These processes operate concurrently and are influenced by sediment availability, yet vary on the basis of available accommodation space. At longer timescales, the influence of auto-compaction diminishes as organic matter has undergone significant compression and decomposition, yet accumulated material remains proportional to available accommodation space. These analyses confirm that temporal discrepancies in rates of substrate elevation change can be resolved by accounting for the timescale over which processes operate and the influence of sea-level rise on available accommodation space. Accordingly, models should dynamically consider rates of surface elevation change relative to available accommodation space.
How to cite: Rogers, K. and Saintilan, N.: Coastal wetland substrate elevation is dynamically related to accommodation space and influenced by sea-level rise, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14069, https://doi.org/10.5194/egusphere-egu21-14069, 2021.
EGU21-9107 | vPICO presentations | GM6.4
Salt marshes adjustment to anthropogenic pressures and sea-level riseA. Rita Carrasco, Katerina Kombiadou, and Miguel Amado
It is predictable that salt marshes in regions, where sediment loads are high, should be stable against a broader range of relative sea level scenarios than those in sediment-poor systems. Despite extensive theoretical and laboratory studies, additional syntheses of marsh ‘persistence’ indicators under human interventions and accelerated sea-level rise rates are still needed. This study investigates the recent lateral changes occurring in lagoon-type marshes of the Ria Formosa lagoon (south Portugal) in the presence of human interventions and sea-level rise, to identify the major drivers for past marsh evolution and to estimate potential future trends. The conducted analysis assessed the past geomorphological adjustment based on imagery analysis and assessed its potential future adjustment to sea-level rise (~100 years) based on modelled land cover changes (by employing the SLAMM model within two sea-level rise scenarios).
Salt marshes in the Ria Formosa showed slow lateral growth rates over the last 70 years (<1 mm∙yr-1), with localized erosion along the main navigable channels associated with dredging activities. Higher change rates were noted near the inlets, with stronger progradation near the natural inlets of the system, fed by sediment influx pulses. Any potential influence of sea-level increase to an intensification of marsh-edge erosion in the past, could not be distinguished from human-induced pressures in the area. No significant sediment was exchanged between the salt marshes and tidal flats, and no self-organization pattern between them was observed in past. The related analysis showed that landcover changes in the salt marsh areas are likely to be more prominent in the future. The obtained results showed evidence of non-linearity in marsh response to high sea-level rise rates, which could indicate to the presence of critical thresholds and potential negative feedbacks within the system, with significant implications to marsh resilience.
Acknowledgements:
Rita Carrasco was supported by the contract DL57/2016/CP1361/CT0002, Katerina Kombiadou was supported by the research project ENLACE (ref. PTDC/CTA-GFI/28949/2017), all funded by Fundação para a Ciência e a Tecnologia. The authors would like to acknowledge the support granted by UIDB/00350/2020 CIMA BASE.
How to cite: Carrasco, A. R., Kombiadou, K., and Amado, M.: Salt marshes adjustment to anthropogenic pressures and sea-level rise, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9107, https://doi.org/10.5194/egusphere-egu21-9107, 2021.
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It is predictable that salt marshes in regions, where sediment loads are high, should be stable against a broader range of relative sea level scenarios than those in sediment-poor systems. Despite extensive theoretical and laboratory studies, additional syntheses of marsh ‘persistence’ indicators under human interventions and accelerated sea-level rise rates are still needed. This study investigates the recent lateral changes occurring in lagoon-type marshes of the Ria Formosa lagoon (south Portugal) in the presence of human interventions and sea-level rise, to identify the major drivers for past marsh evolution and to estimate potential future trends. The conducted analysis assessed the past geomorphological adjustment based on imagery analysis and assessed its potential future adjustment to sea-level rise (~100 years) based on modelled land cover changes (by employing the SLAMM model within two sea-level rise scenarios).
Salt marshes in the Ria Formosa showed slow lateral growth rates over the last 70 years (<1 mm∙yr-1), with localized erosion along the main navigable channels associated with dredging activities. Higher change rates were noted near the inlets, with stronger progradation near the natural inlets of the system, fed by sediment influx pulses. Any potential influence of sea-level increase to an intensification of marsh-edge erosion in the past, could not be distinguished from human-induced pressures in the area. No significant sediment was exchanged between the salt marshes and tidal flats, and no self-organization pattern between them was observed in past. The related analysis showed that landcover changes in the salt marsh areas are likely to be more prominent in the future. The obtained results showed evidence of non-linearity in marsh response to high sea-level rise rates, which could indicate to the presence of critical thresholds and potential negative feedbacks within the system, with significant implications to marsh resilience.
Acknowledgements:
Rita Carrasco was supported by the contract DL57/2016/CP1361/CT0002, Katerina Kombiadou was supported by the research project ENLACE (ref. PTDC/CTA-GFI/28949/2017), all funded by Fundação para a Ciência e a Tecnologia. The authors would like to acknowledge the support granted by UIDB/00350/2020 CIMA BASE.
How to cite: Carrasco, A. R., Kombiadou, K., and Amado, M.: Salt marshes adjustment to anthropogenic pressures and sea-level rise, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9107, https://doi.org/10.5194/egusphere-egu21-9107, 2021.
EGU21-13983 | vPICO presentations | GM6.4
Will hurricane sedimentation aid southeastern US saltmarsh resiliency in the face of climate change and sea-level rise?Alice Staro, Duncan FitzGerald, Zoe Hughes, Christopher Hein, Ioannis Georgiou, Kendall King, Jennifer Connell, and Christina Pondell
Coastal saltmarshes are an important and highly diverse ecosystem, shielding the mainland from erosion and flooding. Along the US East Coast these valuable wetlands are endangered due to climate change, sea-level rise, and reduced fluvial sediment fluxes. Although hurricanes are commonly an erosional agent, they may be responsible for delivering significant volumes of sediment to the marsh surface, which could aid resiliency by increasing vertical accretion. This study analyzes marsh sediment cores collected during December 2017 within the Georgia Bight, targeting deposits associated with Hurricane Irma, which caused significant wave energy and storm surge along the coast from Florida to South Carolina in September 2017.
We have focused our initial research on samples from Sapelo Island (Georgia), where Hurricane Irma produced maximum wind velocities of 17.5 m/s and a 1.3 m storm surge, inundating the marsh for 14.8 hrs. We find that Irma-related layers are between 2 and 7 cm thick and well-oxidized. These deposits typically consist of laminated mud with low organic content (LOI: 10-25%) and low bulk density (0.3-0.8 g/cm3). On average, Irma event sediment thickness is 4 times the historical average annual accretion, which in Georgia salt marshes is 1.55 mm.
A direct comparison of Irma-affiliated marsh accretion and historical rates is complicated due to differences in consolidation, rooting and vegetation, and the sedimentation history of the marsh. Nonetheless, the storm layer represents a significant addition of sediment to the marsh surface. Thus, future increases in event sedimentation, associated with increased frequency or severity of storms, could help compensate for sea-level rise and lessen the likelihood or extent of marsh loss due to submergence.
How to cite: Staro, A., FitzGerald, D., Hughes, Z., Hein, C., Georgiou, I., King, K., Connell, J., and Pondell, C.: Will hurricane sedimentation aid southeastern US saltmarsh resiliency in the face of climate change and sea-level rise?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13983, https://doi.org/10.5194/egusphere-egu21-13983, 2021.
Coastal saltmarshes are an important and highly diverse ecosystem, shielding the mainland from erosion and flooding. Along the US East Coast these valuable wetlands are endangered due to climate change, sea-level rise, and reduced fluvial sediment fluxes. Although hurricanes are commonly an erosional agent, they may be responsible for delivering significant volumes of sediment to the marsh surface, which could aid resiliency by increasing vertical accretion. This study analyzes marsh sediment cores collected during December 2017 within the Georgia Bight, targeting deposits associated with Hurricane Irma, which caused significant wave energy and storm surge along the coast from Florida to South Carolina in September 2017.
We have focused our initial research on samples from Sapelo Island (Georgia), where Hurricane Irma produced maximum wind velocities of 17.5 m/s and a 1.3 m storm surge, inundating the marsh for 14.8 hrs. We find that Irma-related layers are between 2 and 7 cm thick and well-oxidized. These deposits typically consist of laminated mud with low organic content (LOI: 10-25%) and low bulk density (0.3-0.8 g/cm3). On average, Irma event sediment thickness is 4 times the historical average annual accretion, which in Georgia salt marshes is 1.55 mm.
A direct comparison of Irma-affiliated marsh accretion and historical rates is complicated due to differences in consolidation, rooting and vegetation, and the sedimentation history of the marsh. Nonetheless, the storm layer represents a significant addition of sediment to the marsh surface. Thus, future increases in event sedimentation, associated with increased frequency or severity of storms, could help compensate for sea-level rise and lessen the likelihood or extent of marsh loss due to submergence.
How to cite: Staro, A., FitzGerald, D., Hughes, Z., Hein, C., Georgiou, I., King, K., Connell, J., and Pondell, C.: Will hurricane sedimentation aid southeastern US saltmarsh resiliency in the face of climate change and sea-level rise?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13983, https://doi.org/10.5194/egusphere-egu21-13983, 2021.
EGU21-10682 | vPICO presentations | GM6.4
Quantifying vertical deformation of salt marsh substrates and their recovery during and after storm surge inundationHelen Brooks, Iris Moeller, Tom Spencer, Katherine Royse, Simon Price, and Matt Kirkham
Salt marshes are globally-distributed, intertidal wetlands. These wetlands provide vital ecosystem functions (providing habitats, filtering water and attenuating waves and currents) that can translate into valuable ecosystem services. Alongside the existence of suitable horizontal accommodation space, the ability of the salt marsh platform to accrete or increase in elevation at a rate commensurate with current and projected future rates of sea-level rise is critical to ensuring future saltmarsh functioning.
While several studies have assessed whether marsh surface and subsurface processes can keep pace with sea-level rise, few have measured whether, and to what extent, a marsh substrate may consolidate during a storm surge and whether such deformation is permanent or recoverable. This is of key importance given that the frequency and/or magnitude of storm surges is expected to change over the next few decades in some locations. We apply strictly-controlled oedometer tests to understand the response of salt marsh substrates to an applied normal stress (such as that exerted by a storm surge). We compare sediment samples from Tillingham marsh, eastern England, where the sediment is clay/silt-dominated, to samples from Warton marsh, Morecambe Bay, North West England, where the sediment is sand/silt-dominated.
This research provides, for the first time, insight into the response of two compositionally-different UK marsh substrates to the application of normal stress, such as that induced by hydrostatic loading during extreme inundation events. We demonstrate that both the expected magnitude of axial displacement and the potential to recover vertical deformation after the event are affected by the particle size distribution and the void ratio, as well as past stress conditions on the marsh (particularly as a result of desiccation). The potential for irrecoverable vertical deformation in response to storm surge loading has not previously been identified in salt marsh studies.
The results of this research will improve the ability of future models of marsh geomorphological evolution to better represent these dynamic responses and their implications for the provision of ecosystem services. This research also challenges existing studies which often do not fully parameterise these dynamic responses when considering salt marsh morphodynamics.
How to cite: Brooks, H., Moeller, I., Spencer, T., Royse, K., Price, S., and Kirkham, M.: Quantifying vertical deformation of salt marsh substrates and their recovery during and after storm surge inundation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10682, https://doi.org/10.5194/egusphere-egu21-10682, 2021.
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Salt marshes are globally-distributed, intertidal wetlands. These wetlands provide vital ecosystem functions (providing habitats, filtering water and attenuating waves and currents) that can translate into valuable ecosystem services. Alongside the existence of suitable horizontal accommodation space, the ability of the salt marsh platform to accrete or increase in elevation at a rate commensurate with current and projected future rates of sea-level rise is critical to ensuring future saltmarsh functioning.
While several studies have assessed whether marsh surface and subsurface processes can keep pace with sea-level rise, few have measured whether, and to what extent, a marsh substrate may consolidate during a storm surge and whether such deformation is permanent or recoverable. This is of key importance given that the frequency and/or magnitude of storm surges is expected to change over the next few decades in some locations. We apply strictly-controlled oedometer tests to understand the response of salt marsh substrates to an applied normal stress (such as that exerted by a storm surge). We compare sediment samples from Tillingham marsh, eastern England, where the sediment is clay/silt-dominated, to samples from Warton marsh, Morecambe Bay, North West England, where the sediment is sand/silt-dominated.
This research provides, for the first time, insight into the response of two compositionally-different UK marsh substrates to the application of normal stress, such as that induced by hydrostatic loading during extreme inundation events. We demonstrate that both the expected magnitude of axial displacement and the potential to recover vertical deformation after the event are affected by the particle size distribution and the void ratio, as well as past stress conditions on the marsh (particularly as a result of desiccation). The potential for irrecoverable vertical deformation in response to storm surge loading has not previously been identified in salt marsh studies.
The results of this research will improve the ability of future models of marsh geomorphological evolution to better represent these dynamic responses and their implications for the provision of ecosystem services. This research also challenges existing studies which often do not fully parameterise these dynamic responses when considering salt marsh morphodynamics.
How to cite: Brooks, H., Moeller, I., Spencer, T., Royse, K., Price, S., and Kirkham, M.: Quantifying vertical deformation of salt marsh substrates and their recovery during and after storm surge inundation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10682, https://doi.org/10.5194/egusphere-egu21-10682, 2021.
EGU21-4925 | vPICO presentations | GM6.4
Variability in the erosion response of vertical sections of salt marsh sediments exposed to tidal flat conditionsOlivia Shears, Iris Möller, Tom Spencer, Ben Evans, and Kate Royse
Salt marsh ecosystems are important for supporting biodiversity, sequestering carbon and providing natural coastal protection. Evidence for their existing and potential future loss through marginal erosion is therefore of concern. However, the factors governing spatial variability in the rates of erosion at salt marsh margins – including between creek banks within individual salt marsh sites – remain relatively poorly understood. Accurate prediction of changes to the marsh edge, and thus marsh areal extent, requires more complete understanding of the dynamics and mechanisms occurring at exposed marsh fronts.
In this study, we present observations of the responses of vertical sections of marsh substrate exposed to tidal flat conditions, during a field experiment over a six-month period. Vertical sections were extracted from natural and restored sites at two salt marshes in the UK: Northey Island, eastern England, where sediment is fine-grained, and Hesketh Out Marsh West, north-west England, where sediment is typically sand/silt-dominated. The study specifically investigates the role of different sedimentology and downcore substrate properties, including lamination and rooting structures, on observed change in the exposed vertical sections. Images captured in the field are analysed using structure-from-motion photogrammetry and used to create 3-D models of surface change. This is coupled with laboratory testing of downcore sedimentary characteristics, such as particle size distribution and organic matter content.
The study finds that within-core and between-core variability in substrate response to erosive forcing appears to be partly related to variability in sedimentology. Sediment from sand-dominated layers, such as those found in the cores extracted from Hesketh Out Marsh West, was more rapidly and consistently (i.e. across the sediment cores) removed than clay-silt rich sediment. This grain-scale sediment removal resulted in specific morphological responses, whereby ‘chunks’ of substrate were lost, creating cavity areas further exposed to hydrodynamic forcing. Intrinsic biophysical characteristics, including sediment type and the presence of vegetation structures, can impact vertical connectivity within salt marsh substrates. Observations of structural change in the vertical sections over the six-month study period suggest that reduced downcore connectivity in restored salt marsh substrates results in increased desiccation, cracking and bulk sediment removal. An improved understanding of how such intrinsic substrate properties impact marsh front dynamics will facilitate more accurate predictions of marsh evolution and potential ecosystem service provision under future conditions.
How to cite: Shears, O., Möller, I., Spencer, T., Evans, B., and Royse, K.: Variability in the erosion response of vertical sections of salt marsh sediments exposed to tidal flat conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4925, https://doi.org/10.5194/egusphere-egu21-4925, 2021.
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Salt marsh ecosystems are important for supporting biodiversity, sequestering carbon and providing natural coastal protection. Evidence for their existing and potential future loss through marginal erosion is therefore of concern. However, the factors governing spatial variability in the rates of erosion at salt marsh margins – including between creek banks within individual salt marsh sites – remain relatively poorly understood. Accurate prediction of changes to the marsh edge, and thus marsh areal extent, requires more complete understanding of the dynamics and mechanisms occurring at exposed marsh fronts.
In this study, we present observations of the responses of vertical sections of marsh substrate exposed to tidal flat conditions, during a field experiment over a six-month period. Vertical sections were extracted from natural and restored sites at two salt marshes in the UK: Northey Island, eastern England, where sediment is fine-grained, and Hesketh Out Marsh West, north-west England, where sediment is typically sand/silt-dominated. The study specifically investigates the role of different sedimentology and downcore substrate properties, including lamination and rooting structures, on observed change in the exposed vertical sections. Images captured in the field are analysed using structure-from-motion photogrammetry and used to create 3-D models of surface change. This is coupled with laboratory testing of downcore sedimentary characteristics, such as particle size distribution and organic matter content.
The study finds that within-core and between-core variability in substrate response to erosive forcing appears to be partly related to variability in sedimentology. Sediment from sand-dominated layers, such as those found in the cores extracted from Hesketh Out Marsh West, was more rapidly and consistently (i.e. across the sediment cores) removed than clay-silt rich sediment. This grain-scale sediment removal resulted in specific morphological responses, whereby ‘chunks’ of substrate were lost, creating cavity areas further exposed to hydrodynamic forcing. Intrinsic biophysical characteristics, including sediment type and the presence of vegetation structures, can impact vertical connectivity within salt marsh substrates. Observations of structural change in the vertical sections over the six-month study period suggest that reduced downcore connectivity in restored salt marsh substrates results in increased desiccation, cracking and bulk sediment removal. An improved understanding of how such intrinsic substrate properties impact marsh front dynamics will facilitate more accurate predictions of marsh evolution and potential ecosystem service provision under future conditions.
How to cite: Shears, O., Möller, I., Spencer, T., Evans, B., and Royse, K.: Variability in the erosion response of vertical sections of salt marsh sediments exposed to tidal flat conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4925, https://doi.org/10.5194/egusphere-egu21-4925, 2021.
EGU21-4169 | vPICO presentations | GM6.4
Evolution of Tidal Flats in the Northern Part of the Po Delta (Italy): A Strategy for Future Buiding-with-Nature ManagementRiccardo Brunetta and Paolo Ciavola
In the period 1950s-60s, the Po river Delta (Northern Italy) was hit by several floods. Agricultural fields were covered by water and many of them remained submerged since. As a consequence of the massive sediment injection into the system, this lead to the birth of new tidal flats around the tip of the Delta. The evolution of these environments over 50 years was studied, as they may be taken as an example for future reconstruction of intertidal areas. The sediment distribution and the morphological evolution of a young tidal flat of about 10 ha located in the Northern part of the Po della Pila branch were studied by undertaking fieldwork since October 2018, including detailed topographic surveys using a UAV, sedimentological analyses, and a study of sediment deposition rates. An extended crevasse splay covers the central part of the flat. The granulometry is predominately fine (Silty clay and Clayey silt), except for the central area, where the sand percentage increases (Loam and Silty sand). This surface distribution is uniform down to ~10 cm; the sand percentage increases instead within the sediment column from ~10 to 25 cm next to the mouths of the channels. The tidal flat experienced a positive sediment budget and it was characterized by higher rates of accretion after the Po river floods. These observations suggest that the tidal channels are fed by sediment from the Po River branch. Orthophotos from the 1950s show that the tidal flat is about 17 - 20 years old and its formation was influenced by human intervention and river floods. The work aims at finally comparing this case study with other tidal flats and salt marshes worldwide characterized by similar and different tidal regimes, to identify the optimal elevation for vegetation to establish and flourish, to support the future restoration of these environments.
How to cite: Brunetta, R. and Ciavola, P.: Evolution of Tidal Flats in the Northern Part of the Po Delta (Italy): A Strategy for Future Buiding-with-Nature Management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4169, https://doi.org/10.5194/egusphere-egu21-4169, 2021.
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In the period 1950s-60s, the Po river Delta (Northern Italy) was hit by several floods. Agricultural fields were covered by water and many of them remained submerged since. As a consequence of the massive sediment injection into the system, this lead to the birth of new tidal flats around the tip of the Delta. The evolution of these environments over 50 years was studied, as they may be taken as an example for future reconstruction of intertidal areas. The sediment distribution and the morphological evolution of a young tidal flat of about 10 ha located in the Northern part of the Po della Pila branch were studied by undertaking fieldwork since October 2018, including detailed topographic surveys using a UAV, sedimentological analyses, and a study of sediment deposition rates. An extended crevasse splay covers the central part of the flat. The granulometry is predominately fine (Silty clay and Clayey silt), except for the central area, where the sand percentage increases (Loam and Silty sand). This surface distribution is uniform down to ~10 cm; the sand percentage increases instead within the sediment column from ~10 to 25 cm next to the mouths of the channels. The tidal flat experienced a positive sediment budget and it was characterized by higher rates of accretion after the Po river floods. These observations suggest that the tidal channels are fed by sediment from the Po River branch. Orthophotos from the 1950s show that the tidal flat is about 17 - 20 years old and its formation was influenced by human intervention and river floods. The work aims at finally comparing this case study with other tidal flats and salt marshes worldwide characterized by similar and different tidal regimes, to identify the optimal elevation for vegetation to establish and flourish, to support the future restoration of these environments.
How to cite: Brunetta, R. and Ciavola, P.: Evolution of Tidal Flats in the Northern Part of the Po Delta (Italy): A Strategy for Future Buiding-with-Nature Management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4169, https://doi.org/10.5194/egusphere-egu21-4169, 2021.
EGU21-7537 | vPICO presentations | GM6.4
Multi-Time Scale Mangrove-Mudflat Modelling: Exploring Guyana’s Unique Dataset & Numerical ModellingUwe Best, Mick van der Wegen, Jasper Dijkstra, Johan Reyns, and Dano Roelvink
The uncertainty surrounding the impact of sea-level-rise (SLR) and storms, which threaten the coastal hinterland, heightens the need for design guidelines on mangroves adaptation and their use in coastal safety. Mangrove forests, well known as coastal ecosystem defences, attenuate the hydrodynamic forces, reduce coastal erosion and foster conditions for increased sedimentation. However, the mechanistic understanding of the feedbacks between the vegetation and the morphodynamics and, the processes which result in the long term erosion- sedimentation during extreme wave events has been limited (Horstman 2014, Best 2017).Therefore, this research seeks to quantify the bio-physical processes governing the geomorphological evolution of mangrove-mudflat systems utilizing spatially explicit observations of mangrove population dynamics with process-based modelling. For calibration purposes and increased insight into interactions between hydrodynamics, sediment dynamics and mangroves, field observations were collected along Guyana’s coast.
A quadrant, 1km wide and 6km in length, was established in the mangrove-mudflat coastline at Chateau Margot. This stretch of coastline is subject to a semi-diurnal tidal regime with a maximum tidal range of 3.5m during spring tide. Using the data, we developed a 2D high-resolution depth-averaged model of the field site using Delft3D-Flexible Mesh.
We coupled this model with a mangrove dynamics model capturing the development of Avicennia germinans and Laguncularia racemosa species under suitable inundation and competition regimes. With the dynamic vegetation interface linked via the Basic Model Interface (BMI) with Delft3D-FM, the initial establishment is randomized over the computation grid cells, followed by the growth, diffusion and decay of the mangroves in areas of high stresses. The coupled model simulates the geomorphological development from the interaction between the intertidal flow, waves, sediment transport and the temporal and spatial variation in the mangrove growth, drag and bio-accumulation over 100 years.
A combination of 1D and 2D simulations to analyze the equilibrium behavior of the system as well to identify the mechanistic feedbacks critical for the development of stable belt widths. Waves are critical for the transport of mud into the mangrove belt during high tide. Inundation of the inner fringe occurs during spring tides, so the calm conditions allow for a heightened platform and species establishment. The channels form the major path for the tidal inflow during the lower tides, while the interior of the forest is an effective sediment sink during the higher tides.
RCP SLR scenarios, liner and exponential, reinforce behavioral trends for mangrove retreat and decay, with modelled tipping points realized after 1.5m increases. Results indicate mangrove adaptability hinges on the long term sedimentation responses and system conditions to promote the establishment of belt widths exceeding 300m.
How to cite: Best, U., van der Wegen, M., Dijkstra, J., Reyns, J., and Roelvink, D.: Multi-Time Scale Mangrove-Mudflat Modelling: Exploring Guyana’s Unique Dataset & Numerical Modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7537, https://doi.org/10.5194/egusphere-egu21-7537, 2021.
The uncertainty surrounding the impact of sea-level-rise (SLR) and storms, which threaten the coastal hinterland, heightens the need for design guidelines on mangroves adaptation and their use in coastal safety. Mangrove forests, well known as coastal ecosystem defences, attenuate the hydrodynamic forces, reduce coastal erosion and foster conditions for increased sedimentation. However, the mechanistic understanding of the feedbacks between the vegetation and the morphodynamics and, the processes which result in the long term erosion- sedimentation during extreme wave events has been limited (Horstman 2014, Best 2017).Therefore, this research seeks to quantify the bio-physical processes governing the geomorphological evolution of mangrove-mudflat systems utilizing spatially explicit observations of mangrove population dynamics with process-based modelling. For calibration purposes and increased insight into interactions between hydrodynamics, sediment dynamics and mangroves, field observations were collected along Guyana’s coast.
A quadrant, 1km wide and 6km in length, was established in the mangrove-mudflat coastline at Chateau Margot. This stretch of coastline is subject to a semi-diurnal tidal regime with a maximum tidal range of 3.5m during spring tide. Using the data, we developed a 2D high-resolution depth-averaged model of the field site using Delft3D-Flexible Mesh.
We coupled this model with a mangrove dynamics model capturing the development of Avicennia germinans and Laguncularia racemosa species under suitable inundation and competition regimes. With the dynamic vegetation interface linked via the Basic Model Interface (BMI) with Delft3D-FM, the initial establishment is randomized over the computation grid cells, followed by the growth, diffusion and decay of the mangroves in areas of high stresses. The coupled model simulates the geomorphological development from the interaction between the intertidal flow, waves, sediment transport and the temporal and spatial variation in the mangrove growth, drag and bio-accumulation over 100 years.
A combination of 1D and 2D simulations to analyze the equilibrium behavior of the system as well to identify the mechanistic feedbacks critical for the development of stable belt widths. Waves are critical for the transport of mud into the mangrove belt during high tide. Inundation of the inner fringe occurs during spring tides, so the calm conditions allow for a heightened platform and species establishment. The channels form the major path for the tidal inflow during the lower tides, while the interior of the forest is an effective sediment sink during the higher tides.
RCP SLR scenarios, liner and exponential, reinforce behavioral trends for mangrove retreat and decay, with modelled tipping points realized after 1.5m increases. Results indicate mangrove adaptability hinges on the long term sedimentation responses and system conditions to promote the establishment of belt widths exceeding 300m.
How to cite: Best, U., van der Wegen, M., Dijkstra, J., Reyns, J., and Roelvink, D.: Multi-Time Scale Mangrove-Mudflat Modelling: Exploring Guyana’s Unique Dataset & Numerical Modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7537, https://doi.org/10.5194/egusphere-egu21-7537, 2021.
EGU21-8837 | vPICO presentations | GM6.4
Long-term seasonal dynamics of seagrass extent in a Mediterranean Lagoon (Venice, Italy) from public satellite dataGuillaume Goodwin, Luca Carniello, Andrea D'Alpaos, Marco Marani, and Sonia Silvestri
Seagrass meadows are globally distributed ecosystems found on coastal shelves, where they typically occupy the intertidal and shallow subtidal zones. Their sensitivity to environmental changes and proximity to human activities puts them at risk of degradation; as highly valuable marine habitats and potent carbon sequestration agents, they are therefore the target of numerous conservation programmes.
The presence of seagrass strongly influences both wave and current propagation as well as sediment mobility, affecting the morphodynamics of entire estuarine systems. However, quantifying this influence is difficult, because our knowledge of seagrass cover is limited by its dynamic nature. Sensitivity to environmental factors such as nutrient load, available sunlight (mediated by turbidity) and temperature makes seagrass meadows prone to widespread changes in extent and density. Further degradation may occur stochastically through fishing and aquaculture. Conversely, seasonal cycles of high productivity allow meadows to recover and colonize new grounds through clonal and sexual reproduction.
We propose a novel and cost-effective method to monitor seagrass cover in shallow waters across its seasonal and interannual variations. Combining machine learning and simple numerical modelling, we create a dense time-series of seagrass extent using over 100 LandSat scenes covering a 20-year-long period in the Venice Lagoon, Italy. Based on an expert-lead ecological survey (2004), we train one binary Random Forest Classifier in each of 5 environmentally-homogeneous geographical subzones, using spectral reflectance in the blue, green, red and near-infrared bands of the corresponding LandSat scene as recognition features. We then predict seagrass presence probability for LandSat scenes spanning the 1999-2019 period. Such predictions are made unstable by their sensitivity to sediment plumes as well as algal or gelbstoff blooms. Classification is therefore constrained by a simple numerical model that simulates clonal and sexual reproduction, regional die-off and punctual degradation. The model examines the potential areas colonised or degraded with respect to previous scenes, iteratively building stabilised maps of seagrass cover over time.
Results are verified using further expert-lead estival surveys of the lagoon (2009, 2010, 2017) and of the inlets of Lido, Malamocco and Chioggia (2006 to 2015), as well as 10 digitised seagrass patches for a subsample of 20 invernal scenes. Accuracy metrics improve on the raw predictions (>80% to >85%), and scene-to-scene variability is reduced(>50% to <5%). These results show that public satellite data can be used to map seagrass cover and monitor its seasonal variations. In the future, cover maps may be used to estimate carbon storage, improve sediment transport models in shallow coastal areas, or identify drivers of change in seagrass meadows.
How to cite: Goodwin, G., Carniello, L., D'Alpaos, A., Marani, M., and Silvestri, S.: Long-term seasonal dynamics of seagrass extent in a Mediterranean Lagoon (Venice, Italy) from public satellite data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8837, https://doi.org/10.5194/egusphere-egu21-8837, 2021.
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Seagrass meadows are globally distributed ecosystems found on coastal shelves, where they typically occupy the intertidal and shallow subtidal zones. Their sensitivity to environmental changes and proximity to human activities puts them at risk of degradation; as highly valuable marine habitats and potent carbon sequestration agents, they are therefore the target of numerous conservation programmes.
The presence of seagrass strongly influences both wave and current propagation as well as sediment mobility, affecting the morphodynamics of entire estuarine systems. However, quantifying this influence is difficult, because our knowledge of seagrass cover is limited by its dynamic nature. Sensitivity to environmental factors such as nutrient load, available sunlight (mediated by turbidity) and temperature makes seagrass meadows prone to widespread changes in extent and density. Further degradation may occur stochastically through fishing and aquaculture. Conversely, seasonal cycles of high productivity allow meadows to recover and colonize new grounds through clonal and sexual reproduction.
We propose a novel and cost-effective method to monitor seagrass cover in shallow waters across its seasonal and interannual variations. Combining machine learning and simple numerical modelling, we create a dense time-series of seagrass extent using over 100 LandSat scenes covering a 20-year-long period in the Venice Lagoon, Italy. Based on an expert-lead ecological survey (2004), we train one binary Random Forest Classifier in each of 5 environmentally-homogeneous geographical subzones, using spectral reflectance in the blue, green, red and near-infrared bands of the corresponding LandSat scene as recognition features. We then predict seagrass presence probability for LandSat scenes spanning the 1999-2019 period. Such predictions are made unstable by their sensitivity to sediment plumes as well as algal or gelbstoff blooms. Classification is therefore constrained by a simple numerical model that simulates clonal and sexual reproduction, regional die-off and punctual degradation. The model examines the potential areas colonised or degraded with respect to previous scenes, iteratively building stabilised maps of seagrass cover over time.
Results are verified using further expert-lead estival surveys of the lagoon (2009, 2010, 2017) and of the inlets of Lido, Malamocco and Chioggia (2006 to 2015), as well as 10 digitised seagrass patches for a subsample of 20 invernal scenes. Accuracy metrics improve on the raw predictions (>80% to >85%), and scene-to-scene variability is reduced(>50% to <5%). These results show that public satellite data can be used to map seagrass cover and monitor its seasonal variations. In the future, cover maps may be used to estimate carbon storage, improve sediment transport models in shallow coastal areas, or identify drivers of change in seagrass meadows.
How to cite: Goodwin, G., Carniello, L., D'Alpaos, A., Marani, M., and Silvestri, S.: Long-term seasonal dynamics of seagrass extent in a Mediterranean Lagoon (Venice, Italy) from public satellite data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8837, https://doi.org/10.5194/egusphere-egu21-8837, 2021.
EGU21-1011 | vPICO presentations | GM6.4
Effects of interactions between macroalgae and seagrass on the distribution of macrobenthic invertebrate communities at the Yellow River Estuary, ChinaXinyan Wang, Jiaguo Yan, Junhong Bai, Dongdong Shao, and Baoshan Cui
Algae-dominance in seagrass beds has been well recognized, however, the competitive relationship between seagrass and macroalgae along land-sea gradients and their ecological effects has received little attention. In this study, a field survey was conducted at the Yellow River Estuary to investigate the effects of macroalgal proliferation on seagrass and macrobenthic invertebrate communities. Our results suggested that strong competitive interaction existed between the two primary producers, and the positive or negative effects of macroalgae on seagrass growth varied along land-sea gradient. Furthermore, the dominant controlling factors on the biomass, density and diversity of macrobenthic invertebrate communities were found to vary accordingly, i.e., from features of the primary producers in the nearshore where macroalgae suppressed seagrass growth to hydrodynamic disturbance in the offshore where macroalgae facilitated seagrass growth. Our study emphasizes the importance to integrate interspecific competition into ecosystem-based management of seagrass ecosystem, and provides references for additional ecological indicators.
How to cite: Wang, X., Yan, J., Bai, J., Shao, D., and Cui, B.: Effects of interactions between macroalgae and seagrass on the distribution of macrobenthic invertebrate communities at the Yellow River Estuary, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1011, https://doi.org/10.5194/egusphere-egu21-1011, 2021.
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Algae-dominance in seagrass beds has been well recognized, however, the competitive relationship between seagrass and macroalgae along land-sea gradients and their ecological effects has received little attention. In this study, a field survey was conducted at the Yellow River Estuary to investigate the effects of macroalgal proliferation on seagrass and macrobenthic invertebrate communities. Our results suggested that strong competitive interaction existed between the two primary producers, and the positive or negative effects of macroalgae on seagrass growth varied along land-sea gradient. Furthermore, the dominant controlling factors on the biomass, density and diversity of macrobenthic invertebrate communities were found to vary accordingly, i.e., from features of the primary producers in the nearshore where macroalgae suppressed seagrass growth to hydrodynamic disturbance in the offshore where macroalgae facilitated seagrass growth. Our study emphasizes the importance to integrate interspecific competition into ecosystem-based management of seagrass ecosystem, and provides references for additional ecological indicators.
How to cite: Wang, X., Yan, J., Bai, J., Shao, D., and Cui, B.: Effects of interactions between macroalgae and seagrass on the distribution of macrobenthic invertebrate communities at the Yellow River Estuary, China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1011, https://doi.org/10.5194/egusphere-egu21-1011, 2021.
EGU21-15258 | vPICO presentations | GM6.4
Impact of Climate Change on Coastal Meadows: a Mesocosm ApproachThaisa Bergamo, Raymond Ward, Christopher Joyce, and Kalev Sepp
Coastal meadows supply a wide range of ecosystem services, including high carbon storage, high plant species richness and a wide variety of habitat types, which supports breeding and migratory bird populations. However, global change (climate change, pollution and environmental degradation) poses several threats to the stability and ecosystem services supplied by coastal meadows. Specifically within the Baltic Sea, recent estimates foresee various degrees of sea level rise along the Estonian coast and salinity is expected to decrease in the eastern Baltic and increase in the west. In order to assess the effects of climate change in coastal wetlands, an investigation of the influence of changes in water level and salinity on coastal wetland plant communities was undertaken. Future scenarios of Estonian coastal wetlands were evaluated using a three-year mesocosm experiment simulating altered environmental conditions. The response of three plant communities (Open Pioneer, Lower Shore and Upper Shore) were assessed in terms of changes in species composition through time. The experiment included 45 mesocosms, 15 per community with 5 treatments (3 replicates per treatment) with control, altered water level and salinity. Exploratory analysis, ANOVA and NMDS, were used to assess changes in the plant communities throughout the duration of the project. Preliminary results show that Open Pioneer is more sensitive to decreased salinity. A decrease in percentage cover of species adapted to high salinity concentration (e.g. Spergularia marina) was observed. On the other hand, Lower Shore didn’t show any clear changes with the treatments. In order to obtain deeper insights, further analysis are needed to reveal complex community shifts under altered physical conditions.
How to cite: Bergamo, T., Ward, R., Joyce, C., and Sepp, K.: Impact of Climate Change on Coastal Meadows: a Mesocosm Approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15258, https://doi.org/10.5194/egusphere-egu21-15258, 2021.
Coastal meadows supply a wide range of ecosystem services, including high carbon storage, high plant species richness and a wide variety of habitat types, which supports breeding and migratory bird populations. However, global change (climate change, pollution and environmental degradation) poses several threats to the stability and ecosystem services supplied by coastal meadows. Specifically within the Baltic Sea, recent estimates foresee various degrees of sea level rise along the Estonian coast and salinity is expected to decrease in the eastern Baltic and increase in the west. In order to assess the effects of climate change in coastal wetlands, an investigation of the influence of changes in water level and salinity on coastal wetland plant communities was undertaken. Future scenarios of Estonian coastal wetlands were evaluated using a three-year mesocosm experiment simulating altered environmental conditions. The response of three plant communities (Open Pioneer, Lower Shore and Upper Shore) were assessed in terms of changes in species composition through time. The experiment included 45 mesocosms, 15 per community with 5 treatments (3 replicates per treatment) with control, altered water level and salinity. Exploratory analysis, ANOVA and NMDS, were used to assess changes in the plant communities throughout the duration of the project. Preliminary results show that Open Pioneer is more sensitive to decreased salinity. A decrease in percentage cover of species adapted to high salinity concentration (e.g. Spergularia marina) was observed. On the other hand, Lower Shore didn’t show any clear changes with the treatments. In order to obtain deeper insights, further analysis are needed to reveal complex community shifts under altered physical conditions.
How to cite: Bergamo, T., Ward, R., Joyce, C., and Sepp, K.: Impact of Climate Change on Coastal Meadows: a Mesocosm Approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15258, https://doi.org/10.5194/egusphere-egu21-15258, 2021.
EGU21-8626 | vPICO presentations | GM6.4
Ecosystem services in coastal wetlands: Investigating bio- and hydro-mechanical traits of salt marsh vegetationKara Keimer, Charlotte Steinigeweg, Viktoria Kosmalla, Oliver Lojek, David Schürenkamp, Boris Schröder, and Nils Goseberg
Biodiversity and nature conservation play an increasingly important role with growing societal awareness, which is reflected in current European legislative frameworks such as the Marine Strategy Framework Directive or the Water Framework Directive, calling for integrative solutions and restoration of good environmental status. Salt marshes provide ecosystem services which can help mitigate climate change and sea level rise threats and simultaneously address coastal squeeze problems. The periodical submergence due to tidal changes creates a special ecosystem with different zones delineated by a landward increasing marsh elevation, which are inhabited by different plant and animal communities. In addition to their ecological value, salt marshes provide coastal protection, as they dissipate wave energy and stabilize otherwise exposed coastal soil lining sea dikes.
The "Gute Küste Niedersachsen" research project investigates which environmental properties account for livable and safe coastal conditions along temperate climate coastlines, focusing on the symbiosis of human settlements, nature conservation and sustainable coastal protection. Specifically, the identification of vegetation-mediated ecosystem services within salt marshes at the North Sea coast of Lower Saxony, Germany is addressed here. The overarching goal of the transdisciplinary project is to gain knowledge of natural or nature-based systems and their processes within real-world laboratories at the coast to incorporate proven ecosystem services into standardized coastal protection design guidelines and promote integrated coastal zone management.
Methods include field observations and experiments, hydraulic laboratory experiments and numerical simulations over the course of 5 years. During the first years, a systematic observation of vegetation regarding distribution patterns, growth, density, and bio-mechanical (e.g. flexural rigidity, area moment of inertia) as well as root properties (e.g. root length density, tensile strength) and their respective seasonality is conducted. Through comprehensive monitoring covering large areas of halophytic meadows, a physical model of heterogeneous salt marshes will be developed. Simultaneous measurements of environmental parameters covering waves, currents and soil properties yield a comprehensive data set for analysis, numerical and analytical modeling purposes.
Hydraulic experiments modeling the wave-vegetation-soil interaction will be devised based on field data, developing dynamically and geometrically scaled vegetation surrogates. Besides vegetation properties aboveground, a focus will be on previously sparsely considered root system effects that is hypothesized to govern erosional processes in salt marshes.
How to cite: Keimer, K., Steinigeweg, C., Kosmalla, V., Lojek, O., Schürenkamp, D., Schröder, B., and Goseberg, N.: Ecosystem services in coastal wetlands: Investigating bio- and hydro-mechanical traits of salt marsh vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8626, https://doi.org/10.5194/egusphere-egu21-8626, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Biodiversity and nature conservation play an increasingly important role with growing societal awareness, which is reflected in current European legislative frameworks such as the Marine Strategy Framework Directive or the Water Framework Directive, calling for integrative solutions and restoration of good environmental status. Salt marshes provide ecosystem services which can help mitigate climate change and sea level rise threats and simultaneously address coastal squeeze problems. The periodical submergence due to tidal changes creates a special ecosystem with different zones delineated by a landward increasing marsh elevation, which are inhabited by different plant and animal communities. In addition to their ecological value, salt marshes provide coastal protection, as they dissipate wave energy and stabilize otherwise exposed coastal soil lining sea dikes.
The "Gute Küste Niedersachsen" research project investigates which environmental properties account for livable and safe coastal conditions along temperate climate coastlines, focusing on the symbiosis of human settlements, nature conservation and sustainable coastal protection. Specifically, the identification of vegetation-mediated ecosystem services within salt marshes at the North Sea coast of Lower Saxony, Germany is addressed here. The overarching goal of the transdisciplinary project is to gain knowledge of natural or nature-based systems and their processes within real-world laboratories at the coast to incorporate proven ecosystem services into standardized coastal protection design guidelines and promote integrated coastal zone management.
Methods include field observations and experiments, hydraulic laboratory experiments and numerical simulations over the course of 5 years. During the first years, a systematic observation of vegetation regarding distribution patterns, growth, density, and bio-mechanical (e.g. flexural rigidity, area moment of inertia) as well as root properties (e.g. root length density, tensile strength) and their respective seasonality is conducted. Through comprehensive monitoring covering large areas of halophytic meadows, a physical model of heterogeneous salt marshes will be developed. Simultaneous measurements of environmental parameters covering waves, currents and soil properties yield a comprehensive data set for analysis, numerical and analytical modeling purposes.
Hydraulic experiments modeling the wave-vegetation-soil interaction will be devised based on field data, developing dynamically and geometrically scaled vegetation surrogates. Besides vegetation properties aboveground, a focus will be on previously sparsely considered root system effects that is hypothesized to govern erosional processes in salt marshes.
How to cite: Keimer, K., Steinigeweg, C., Kosmalla, V., Lojek, O., Schürenkamp, D., Schröder, B., and Goseberg, N.: Ecosystem services in coastal wetlands: Investigating bio- and hydro-mechanical traits of salt marsh vegetation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8626, https://doi.org/10.5194/egusphere-egu21-8626, 2021.
EGU21-7114 | vPICO presentations | GM6.4 | Highlight
The standing biomass of saltmarshes as a key variable for estimating their wave energy damping capacityMaria Maza, Javier L. Lara, and Iñigo J. Losada
The estimation of wave energy dissipation produced by saltmarshes has traditionally been obtained in terms of a drag or friction force. The estimation of these forces is made taking into account the characteristics of the saltmarsh (i.e. biomechanical properties, morphology, density) and a hydrodynamic coefficient (i.e. the drag or friction coefficient). The characterization of a vegetated ecosystem by measuring leaf traits, the biomechanical properties of the plants and the number of individuals per unit area involves a lot of effort and is case-specific. In addition, hydrodynamic coefficients are selected on the basis of simplified geometry parameterizations or on calibrations performed in ad hoc studies and accurate estimates rely on their validation under real conditions.
Although for a very limited number of species, previous studies have shown that wave damping positively correlates with standing biomass. Therefore, standing biomass can be a unique variable that defines the wave energy attenuation capacity of the ecosystem. In addition, this variable has already been already characterized for many ecosystems by means of traditional plant harvesting or more recently using aerial images. Then, to further explore its relationship with the induced flow energy attenuation, a new set of experiments is proposed using real vegetation, with contrasting morphology and biomechanical properties, and subjected to different incident flow conditions. The experiments are carried out considering four species of vegetation, with contrasting biomechanical properties and morphology, and including two densities per species. Three water depths, wave heights from 0.08 to 0.18 m and wave periods from 1.5 to 4 s are tested. Capacitive free surface gauges and Acoustic Doppler Velocimeters (ADVs) are used to measure wave damping plant capacity along the meadow.
A direct relationship between the standing biomass of the meadow and plant induced wave attenuation is found for the eight vegetated conditions. In addition, a single relationship is obtained for the resultant wave damping and the eight standing biomass values. This relationship provides the basis for the use of standing biomass as a key parameter to estimate the coastal protection service provided by different saltmarsh species using a single variable that can be easily quantified from the field.
How to cite: Maza, M., Lara, J. L., and Losada, I. J.: The standing biomass of saltmarshes as a key variable for estimating their wave energy damping capacity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7114, https://doi.org/10.5194/egusphere-egu21-7114, 2021.
The estimation of wave energy dissipation produced by saltmarshes has traditionally been obtained in terms of a drag or friction force. The estimation of these forces is made taking into account the characteristics of the saltmarsh (i.e. biomechanical properties, morphology, density) and a hydrodynamic coefficient (i.e. the drag or friction coefficient). The characterization of a vegetated ecosystem by measuring leaf traits, the biomechanical properties of the plants and the number of individuals per unit area involves a lot of effort and is case-specific. In addition, hydrodynamic coefficients are selected on the basis of simplified geometry parameterizations or on calibrations performed in ad hoc studies and accurate estimates rely on their validation under real conditions.
Although for a very limited number of species, previous studies have shown that wave damping positively correlates with standing biomass. Therefore, standing biomass can be a unique variable that defines the wave energy attenuation capacity of the ecosystem. In addition, this variable has already been already characterized for many ecosystems by means of traditional plant harvesting or more recently using aerial images. Then, to further explore its relationship with the induced flow energy attenuation, a new set of experiments is proposed using real vegetation, with contrasting morphology and biomechanical properties, and subjected to different incident flow conditions. The experiments are carried out considering four species of vegetation, with contrasting biomechanical properties and morphology, and including two densities per species. Three water depths, wave heights from 0.08 to 0.18 m and wave periods from 1.5 to 4 s are tested. Capacitive free surface gauges and Acoustic Doppler Velocimeters (ADVs) are used to measure wave damping plant capacity along the meadow.
A direct relationship between the standing biomass of the meadow and plant induced wave attenuation is found for the eight vegetated conditions. In addition, a single relationship is obtained for the resultant wave damping and the eight standing biomass values. This relationship provides the basis for the use of standing biomass as a key parameter to estimate the coastal protection service provided by different saltmarsh species using a single variable that can be easily quantified from the field.
How to cite: Maza, M., Lara, J. L., and Losada, I. J.: The standing biomass of saltmarshes as a key variable for estimating their wave energy damping capacity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7114, https://doi.org/10.5194/egusphere-egu21-7114, 2021.
EGU21-15068 | vPICO presentations | GM6.4
Novel UAV-based tools for assessing coastal grassland structure and functionMiguel Villoslada, Thaisa Bergamo, and Raymond Ward
Coastal grasslands provide a wide range of ecosystem services worldwide. In order to better target conservation efforts in these ecosystems, it is necessary to develop highly accurate models that account for the spatial nature of ecosystem structure, processes and functions. Here, we present a novel set of UAV-based tools to accurately assess and map coastal grassland structure and functions. Firstly, a combination of UAV-derived datasets were used to produce vegetation indices and micro topographic models. A classification random forest algorithm was used to process the spectral and microtopography datasets and map the extent and spatial configuration of plant communities in coastal meadows in Estonia. The model accurately predicted the occurrence of plant communities with a very high kappa value.
In the second stage, a regression random forest algorithm was used to model and map above-ground biomass within the coastal grasslands sites. Subsequently, the above-ground biomass maps in combination with a mean-shift algorithm were used to assess grassland structural heterogeneity. The results were then related to management history at each study site, showing that continuous, monospecific grazing management tends to simplify grassland structure, which could in turn reduce the supply of a key regulation and maintenance ecosystem services: nursery and reproduction habitat for waders.
These results also indicate that UAV-based surveys can serve as reliable grassland monitoring tools and could aid in the development of site-specific management strategies.
How to cite: Villoslada, M., Bergamo, T., and Ward, R.: Novel UAV-based tools for assessing coastal grassland structure and function , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15068, https://doi.org/10.5194/egusphere-egu21-15068, 2021.
Coastal grasslands provide a wide range of ecosystem services worldwide. In order to better target conservation efforts in these ecosystems, it is necessary to develop highly accurate models that account for the spatial nature of ecosystem structure, processes and functions. Here, we present a novel set of UAV-based tools to accurately assess and map coastal grassland structure and functions. Firstly, a combination of UAV-derived datasets were used to produce vegetation indices and micro topographic models. A classification random forest algorithm was used to process the spectral and microtopography datasets and map the extent and spatial configuration of plant communities in coastal meadows in Estonia. The model accurately predicted the occurrence of plant communities with a very high kappa value.
In the second stage, a regression random forest algorithm was used to model and map above-ground biomass within the coastal grasslands sites. Subsequently, the above-ground biomass maps in combination with a mean-shift algorithm were used to assess grassland structural heterogeneity. The results were then related to management history at each study site, showing that continuous, monospecific grazing management tends to simplify grassland structure, which could in turn reduce the supply of a key regulation and maintenance ecosystem services: nursery and reproduction habitat for waders.
These results also indicate that UAV-based surveys can serve as reliable grassland monitoring tools and could aid in the development of site-specific management strategies.
How to cite: Villoslada, M., Bergamo, T., and Ward, R.: Novel UAV-based tools for assessing coastal grassland structure and function , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15068, https://doi.org/10.5194/egusphere-egu21-15068, 2021.
EGU21-7208 | vPICO presentations | GM6.4
The Mini Buoy: a novel hydrodynamics sensor for long-term deployments in coastal wetlandsCai Ladd, Alejandra Vovides, Christian Schwarz, Gail Chmura, Mohammad Basyuni, María Maza, and Thorsten Balke
Hydrological monitoring is crucial for management and research in coastal wetlands. However, long-term monitoring is scarce due to the high cost of conventional hydrological equipment. The development of open-source and low-power sensors over the past decade presents an opportunity for enabling long-term, high spatial resolution monitoring of hydrodynamics in the intertidal zone. Here, we present the design, calibration, and application of one such sensor: the Mini Buoy. The Mini Buoy is a battery-powered accelerometer and data logger, contained in a standard centrifuge tube. The Mini Buoy floats upright when inundated, and moves freely about a tether anchored to the substrate. Acceleration is measured along a single axis of the buoy, and motion along the axis is used to measure inundation, currents, and waves. Deployments of up to 6 months are possible, and the buoy can measure current and wave orbital velocities as low as 0.05 m/s. Mini Buoys cost less than €350 to assemble, and the materials are globally available. We present the successful application of Mini Buoys in four contrasting scenarios: (1) characterising waves under calm and stormy conditions; (2) linking saltmarsh erosion-expansion patterns with hydrological exposure; (3) identifying high-resolution spatial variability of waves and currents along a saltmarsh edge; and (4) assessing the suitability of former aquaculture ponds for mangrove restoration. Mini Buoys are also being deployed along mangrove fringes across Vietnam, India, and Bangladesh, in order to detect thresholds in hydrodynamic forcing responsible for triggering erosion or progradation events. Mini Buoys offer an exciting and novel tool for coastal management worldwide.
How to cite: Ladd, C., Vovides, A., Schwarz, C., Chmura, G., Basyuni, M., Maza, M., and Balke, T.: The Mini Buoy: a novel hydrodynamics sensor for long-term deployments in coastal wetlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7208, https://doi.org/10.5194/egusphere-egu21-7208, 2021.
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Hydrological monitoring is crucial for management and research in coastal wetlands. However, long-term monitoring is scarce due to the high cost of conventional hydrological equipment. The development of open-source and low-power sensors over the past decade presents an opportunity for enabling long-term, high spatial resolution monitoring of hydrodynamics in the intertidal zone. Here, we present the design, calibration, and application of one such sensor: the Mini Buoy. The Mini Buoy is a battery-powered accelerometer and data logger, contained in a standard centrifuge tube. The Mini Buoy floats upright when inundated, and moves freely about a tether anchored to the substrate. Acceleration is measured along a single axis of the buoy, and motion along the axis is used to measure inundation, currents, and waves. Deployments of up to 6 months are possible, and the buoy can measure current and wave orbital velocities as low as 0.05 m/s. Mini Buoys cost less than €350 to assemble, and the materials are globally available. We present the successful application of Mini Buoys in four contrasting scenarios: (1) characterising waves under calm and stormy conditions; (2) linking saltmarsh erosion-expansion patterns with hydrological exposure; (3) identifying high-resolution spatial variability of waves and currents along a saltmarsh edge; and (4) assessing the suitability of former aquaculture ponds for mangrove restoration. Mini Buoys are also being deployed along mangrove fringes across Vietnam, India, and Bangladesh, in order to detect thresholds in hydrodynamic forcing responsible for triggering erosion or progradation events. Mini Buoys offer an exciting and novel tool for coastal management worldwide.
How to cite: Ladd, C., Vovides, A., Schwarz, C., Chmura, G., Basyuni, M., Maza, M., and Balke, T.: The Mini Buoy: a novel hydrodynamics sensor for long-term deployments in coastal wetlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7208, https://doi.org/10.5194/egusphere-egu21-7208, 2021.
EGU21-13953 | vPICO presentations | GM6.4
Carbon burial capacity limited by accelerated sea-level rise in coastal wetlandsSteven Sandi, Jose Rodriguez, Patricia Saco, Neil Saintilan, and Gerardo Riccardi
Coastal wetland are known to be among the most efficient carbon burial environments around the worlds and given this high efficiency for carbon sequestration, wetland restoration and conservation efforts have been proposed as a way to potentially mitigate greenhouse emissions. The processes that lead to carbon sequestration can be quite complex and often depend on feedbacks between the type of vegetation in the wetlands, tidal flow regime, geomorphology and sediment availability. Coastal wetland vulnerability to submergence due to sea-level rise has been widely discussed in the current literature, and while wetlands could survive under some sea-level rise scenarios, accelerated rates of sea-level rise would most likely result in significant wetland losses. These can be less accentuated when accommodation space is available and the wetland is able to migrate inland, however, topography, physical barriers, and some anthropogenic factors can limit wetland migration thus decreasing the ability of wetlands to cope with sea-level rise. Potential losses of wetland vegetation under accelerated sea-level rise and limited capacity for wetlands to migrate inland are expected to affect the overall efficiency for carbon sequestration. We apply an eco-geomorphic model to simulate vegetation dynamics, carbon accumulation and overall change in carbon stocks for a restored mangrove-saltmarsh wetland experiencing accelerated sea-level rise under different management scenarios. Our results suggest that under accelerated sea-level rise and limited space for inland migration, vegetation might not be able to fully mature, reducing the capacity for sequestering carbon over time.
How to cite: Sandi, S., Rodriguez, J., Saco, P., Saintilan, N., and Riccardi, G.: Carbon burial capacity limited by accelerated sea-level rise in coastal wetlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13953, https://doi.org/10.5194/egusphere-egu21-13953, 2021.
Coastal wetland are known to be among the most efficient carbon burial environments around the worlds and given this high efficiency for carbon sequestration, wetland restoration and conservation efforts have been proposed as a way to potentially mitigate greenhouse emissions. The processes that lead to carbon sequestration can be quite complex and often depend on feedbacks between the type of vegetation in the wetlands, tidal flow regime, geomorphology and sediment availability. Coastal wetland vulnerability to submergence due to sea-level rise has been widely discussed in the current literature, and while wetlands could survive under some sea-level rise scenarios, accelerated rates of sea-level rise would most likely result in significant wetland losses. These can be less accentuated when accommodation space is available and the wetland is able to migrate inland, however, topography, physical barriers, and some anthropogenic factors can limit wetland migration thus decreasing the ability of wetlands to cope with sea-level rise. Potential losses of wetland vegetation under accelerated sea-level rise and limited capacity for wetlands to migrate inland are expected to affect the overall efficiency for carbon sequestration. We apply an eco-geomorphic model to simulate vegetation dynamics, carbon accumulation and overall change in carbon stocks for a restored mangrove-saltmarsh wetland experiencing accelerated sea-level rise under different management scenarios. Our results suggest that under accelerated sea-level rise and limited space for inland migration, vegetation might not be able to fully mature, reducing the capacity for sequestering carbon over time.
How to cite: Sandi, S., Rodriguez, J., Saco, P., Saintilan, N., and Riccardi, G.: Carbon burial capacity limited by accelerated sea-level rise in coastal wetlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13953, https://doi.org/10.5194/egusphere-egu21-13953, 2021.
EGU21-3701 | vPICO presentations | GM6.4
Effects of Temperature increase on N2O Emissions from Intertidal Area along the East China CoastShu Chen and Dongqi Wang
Coasts and estuaries are key contributors to atmospheric nitrous oxide (N2O) emissions. Here, we used laboratory incubation experiments to investigate temperature (12, 25, and 35 °C) and tidal effects on N2O fluxes in sediments sampled from three contrasting latitudinal subareas along the East China Coast (ECC) (North, Mid, and South). Overall, responses of N2O emissions to increasing temperature varied among the three climatic zones. During non-flood and flooding, mean N2O fluxes in sediments sampled from the North subarea increased exponentially with temperature (49.0 ±40.6 nmol m-2 h-1 at 12 °C to 3160 ±3960 nmol m-2 h-1 at 35 °C, and 741 ±518 nmol m-2 h-1 at 12 °C to 1020 ±1400 nmol m-2 h-1 at 35 °C, respectively). However, mean N2O fluxes in sediments sampled from the South subarea decreased at higher temperatures during flooding (977 ±306 nmol m-2 h-1 at 12 °C to 68.0 ±47.5 nmol m-2 h-1 at 35 °C) and non-flood (233 ±292 nmol m-2 h-1 at 12 °C to 183 ±142 nmol m-2 h-1 at 35 °C). Under ongoing global warming, intertidal areas at temperate may act as potential sources of N2O, whereas the contribution of low latitude coastal sediments to N2O budget may decrease. In addition, there is a combined impact of temperature and tidal fluctuation on N2O emissions that controls N2O production and consumption. Our results improve understanding of the diverse feedbacks of N2O emissions from coastal area to global climate change.
How to cite: Chen, S. and Wang, D.: Effects of Temperature increase on N2O Emissions from Intertidal Area along the East China Coast, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3701, https://doi.org/10.5194/egusphere-egu21-3701, 2021.
Coasts and estuaries are key contributors to atmospheric nitrous oxide (N2O) emissions. Here, we used laboratory incubation experiments to investigate temperature (12, 25, and 35 °C) and tidal effects on N2O fluxes in sediments sampled from three contrasting latitudinal subareas along the East China Coast (ECC) (North, Mid, and South). Overall, responses of N2O emissions to increasing temperature varied among the three climatic zones. During non-flood and flooding, mean N2O fluxes in sediments sampled from the North subarea increased exponentially with temperature (49.0 ±40.6 nmol m-2 h-1 at 12 °C to 3160 ±3960 nmol m-2 h-1 at 35 °C, and 741 ±518 nmol m-2 h-1 at 12 °C to 1020 ±1400 nmol m-2 h-1 at 35 °C, respectively). However, mean N2O fluxes in sediments sampled from the South subarea decreased at higher temperatures during flooding (977 ±306 nmol m-2 h-1 at 12 °C to 68.0 ±47.5 nmol m-2 h-1 at 35 °C) and non-flood (233 ±292 nmol m-2 h-1 at 12 °C to 183 ±142 nmol m-2 h-1 at 35 °C). Under ongoing global warming, intertidal areas at temperate may act as potential sources of N2O, whereas the contribution of low latitude coastal sediments to N2O budget may decrease. In addition, there is a combined impact of temperature and tidal fluctuation on N2O emissions that controls N2O production and consumption. Our results improve understanding of the diverse feedbacks of N2O emissions from coastal area to global climate change.
How to cite: Chen, S. and Wang, D.: Effects of Temperature increase on N2O Emissions from Intertidal Area along the East China Coast, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3701, https://doi.org/10.5194/egusphere-egu21-3701, 2021.
EGU21-3425 | vPICO presentations | GM6.4
Salinity effects on mass loss and nutrient release in the litter decomposition of peatland macrophytesCheryl Batistel, Gerald Jurasinski, and Hendrik Schubert
Global mean sea level had been rising and accelerating in the last decades affecting coastal wetlands that are important carbon stores since they are susceptible to fluctuating water levels. Climate-change-driven sea-level rise, which is predicted to reach about one to two meters by 2100, may lead to dramatic shifts in the vegetation composition of coastal wetlands consequently influencing ecosystem functions including photosynthetic activity, biomass production, litter decomposability, and ultimately the pattern and rates of nutrient cycling, carbon storage, and greenhouse gas exchange. In this regard, aside from water level, changes in salinity that may especially influence the decomposition of dead plant material are also of prime concern.
Here, we provide a comparative evaluation of the decomposition rates of the dominant macrophytes in different nearby freshwater and brackish peatlands. We assumed that the degradability of leaf litter differs among species due to the difference in chemical composition. Two peatland sites, Schutower Moor (freshwater) and Diedrichshagen Moor (brackish) were selected to compare the decomposition rate and nutrient release of Phragmites australis, Carex sp. and Schoenoplectus tabernaemontanii as influenced by salinity. We used the litterbag method using senescent leaves or stem parts (for S. tabernaemontanii) of the macrophytes that were collected in late autumn. We deposited 30 litterbags per species per site and retrieved 5 of these per site after 1, 2, 4, 6, 8 and 12 months, respectively.
Regardless of site and species, the highest mass loss occurred in the first 35 days of decomposition with a strong decrease thereafter with almost flat slopes. The initial decay rates of the same species did not differ significantly between sites. However, the initial mass loss of the S. tabernaemontanii litter was significantly higher than the other species. This species has the highest decay coefficient of 0.008 d-1 and 0.006 d-1 in freshwater and brackish sites, respectively. These decay rates are up to four times faster compared to the other species resulting in empty litterbags a year after deployment indicating the complete decomposition of S. tabernaemontanii while other species had between 40% to 60% dry mass remaining. Initially, the carbon and nitrogen contents of S. tabernaemontanii were significantly lower than those of the other species while its initial sulfur content was significantly higher than of the other species. S. tabernaemontanii retained a relatively high amount of nitrogen, phosphorus, sulfur and magnesium throughout decomposition compared to the other species. This keeps the C:N, C:P, C:S, C:Mg and N:P ratios nearly constant from the start to the end of the study suggesting continuous microbial activities due to the availability of such nutrients in the detritus of S. tabernaemontanii. This confirms that P. australis and Carex sp. contribute to the formation of peat while S. tabernaemontanii does not.
Litter quality showed to be a more important factor affecting decomposition than the little difference in salinity between sites (e.g. annual average of 3psu) that did not significantly affect the decomposition rate of macrophyte litter. Therefore, future similar studies should consider comparing sites with higher salinity levels.
How to cite: Batistel, C., Jurasinski, G., and Schubert, H.: Salinity effects on mass loss and nutrient release in the litter decomposition of peatland macrophytes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3425, https://doi.org/10.5194/egusphere-egu21-3425, 2021.
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Global mean sea level had been rising and accelerating in the last decades affecting coastal wetlands that are important carbon stores since they are susceptible to fluctuating water levels. Climate-change-driven sea-level rise, which is predicted to reach about one to two meters by 2100, may lead to dramatic shifts in the vegetation composition of coastal wetlands consequently influencing ecosystem functions including photosynthetic activity, biomass production, litter decomposability, and ultimately the pattern and rates of nutrient cycling, carbon storage, and greenhouse gas exchange. In this regard, aside from water level, changes in salinity that may especially influence the decomposition of dead plant material are also of prime concern.
Here, we provide a comparative evaluation of the decomposition rates of the dominant macrophytes in different nearby freshwater and brackish peatlands. We assumed that the degradability of leaf litter differs among species due to the difference in chemical composition. Two peatland sites, Schutower Moor (freshwater) and Diedrichshagen Moor (brackish) were selected to compare the decomposition rate and nutrient release of Phragmites australis, Carex sp. and Schoenoplectus tabernaemontanii as influenced by salinity. We used the litterbag method using senescent leaves or stem parts (for S. tabernaemontanii) of the macrophytes that were collected in late autumn. We deposited 30 litterbags per species per site and retrieved 5 of these per site after 1, 2, 4, 6, 8 and 12 months, respectively.
Regardless of site and species, the highest mass loss occurred in the first 35 days of decomposition with a strong decrease thereafter with almost flat slopes. The initial decay rates of the same species did not differ significantly between sites. However, the initial mass loss of the S. tabernaemontanii litter was significantly higher than the other species. This species has the highest decay coefficient of 0.008 d-1 and 0.006 d-1 in freshwater and brackish sites, respectively. These decay rates are up to four times faster compared to the other species resulting in empty litterbags a year after deployment indicating the complete decomposition of S. tabernaemontanii while other species had between 40% to 60% dry mass remaining. Initially, the carbon and nitrogen contents of S. tabernaemontanii were significantly lower than those of the other species while its initial sulfur content was significantly higher than of the other species. S. tabernaemontanii retained a relatively high amount of nitrogen, phosphorus, sulfur and magnesium throughout decomposition compared to the other species. This keeps the C:N, C:P, C:S, C:Mg and N:P ratios nearly constant from the start to the end of the study suggesting continuous microbial activities due to the availability of such nutrients in the detritus of S. tabernaemontanii. This confirms that P. australis and Carex sp. contribute to the formation of peat while S. tabernaemontanii does not.
Litter quality showed to be a more important factor affecting decomposition than the little difference in salinity between sites (e.g. annual average of 3psu) that did not significantly affect the decomposition rate of macrophyte litter. Therefore, future similar studies should consider comparing sites with higher salinity levels.
How to cite: Batistel, C., Jurasinski, G., and Schubert, H.: Salinity effects on mass loss and nutrient release in the litter decomposition of peatland macrophytes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3425, https://doi.org/10.5194/egusphere-egu21-3425, 2021.
EGU21-9981 | vPICO presentations | GM6.4
Modeling the hydrodynamics of a wetland under strong anthropic pressures (Torbiere del Sebino, Italy)Stella Volpini, Marco Pilotti, Giulia Valerio, and Steven C. Chapra
The Natural Reserve “Torbiere del Sebino” is situated on the southern bank of Lake Iseo and is one the most meaningful wet zone for extension and ecological importance of northern Italy, belonging to the Natura2000 network.
Torbiere occupies an area of 3.60 km2 within a 14 km2 watershed where almost 12000 inhabitants live and where agricultural activities, mostly vineyards, cover almost 40% of the area; this leads to a significant anthropic pressure that over the last 50 years has compromised the system and changed the equilibria between species, enhancing eutrophication.
Despite the ecological relevance of the area, one of the most important in northern Italy, very little quantitative information is available regarding its current state and evolution in terms of water quality and hydrodynamics. Given the critical environmental condition of the habitat, it is necessary to address the consequences of human impact on the trophic state of Torbiere.
Torbiere consists of a system of shallow lakes or ponds (average depth 1.5 m) whose main affluent is a creek (called Rì) entering from the South. A secondary occasional affluent enters the system from the East and consists of a combined sewer overflow (CSO). Finally, the main effluent is an artificial channel located in the North connecting Torbiere directly with the subalpine Lake Iseo. Although originally subdivided into a set of many interconnected ponds, the separation levees have been demolished over the last decades to enhance internal circulation, under the assumption that this would decrease the residence time and improve the water quality. However, no rational argument was used to support this decision that led to a system where similar characteristics (Secchi’s depth, turbidity, specific conductivity) are found all over the study area and where the expansion of invasive species was easier; now there is some evidence that a separate set of ponds would be better manageable to contrast the eutrophication process. To understand this process, a 3D hydrodynamic model has been set up using Delft-3D, an open source, finite difference package.
Given the great extension of the system, the inner circulation of the water is not driven by the momentum of the affluents, instead the wind plays a major role. This forcing term presents a daily pattern: it blows from the North in the mornings and shifts to the opposite direction in the late afternoon. The water mainly flows from the South to the North. However, preliminary results by Delft 3D showed that the circulation is made complex by the wind. The model shows that opposite directions of horizontal flow velocities are found at the surface and at the bottom of the water column, showing that only the upper layers follow the direction of the wind.
By comparing the actual and previous conditions of separation of the ponds, the model aims to give an answer to whether the choice of demolishing the banks was positive or negative for the water quality of Torbiere. Once the role of the banks will be clarified, the effects of their possible restoration will be addressed.
How to cite: Volpini, S., Pilotti, M., Valerio, G., and Chapra, S. C.: Modeling the hydrodynamics of a wetland under strong anthropic pressures (Torbiere del Sebino, Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9981, https://doi.org/10.5194/egusphere-egu21-9981, 2021.
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The Natural Reserve “Torbiere del Sebino” is situated on the southern bank of Lake Iseo and is one the most meaningful wet zone for extension and ecological importance of northern Italy, belonging to the Natura2000 network.
Torbiere occupies an area of 3.60 km2 within a 14 km2 watershed where almost 12000 inhabitants live and where agricultural activities, mostly vineyards, cover almost 40% of the area; this leads to a significant anthropic pressure that over the last 50 years has compromised the system and changed the equilibria between species, enhancing eutrophication.
Despite the ecological relevance of the area, one of the most important in northern Italy, very little quantitative information is available regarding its current state and evolution in terms of water quality and hydrodynamics. Given the critical environmental condition of the habitat, it is necessary to address the consequences of human impact on the trophic state of Torbiere.
Torbiere consists of a system of shallow lakes or ponds (average depth 1.5 m) whose main affluent is a creek (called Rì) entering from the South. A secondary occasional affluent enters the system from the East and consists of a combined sewer overflow (CSO). Finally, the main effluent is an artificial channel located in the North connecting Torbiere directly with the subalpine Lake Iseo. Although originally subdivided into a set of many interconnected ponds, the separation levees have been demolished over the last decades to enhance internal circulation, under the assumption that this would decrease the residence time and improve the water quality. However, no rational argument was used to support this decision that led to a system where similar characteristics (Secchi’s depth, turbidity, specific conductivity) are found all over the study area and where the expansion of invasive species was easier; now there is some evidence that a separate set of ponds would be better manageable to contrast the eutrophication process. To understand this process, a 3D hydrodynamic model has been set up using Delft-3D, an open source, finite difference package.
Given the great extension of the system, the inner circulation of the water is not driven by the momentum of the affluents, instead the wind plays a major role. This forcing term presents a daily pattern: it blows from the North in the mornings and shifts to the opposite direction in the late afternoon. The water mainly flows from the South to the North. However, preliminary results by Delft 3D showed that the circulation is made complex by the wind. The model shows that opposite directions of horizontal flow velocities are found at the surface and at the bottom of the water column, showing that only the upper layers follow the direction of the wind.
By comparing the actual and previous conditions of separation of the ponds, the model aims to give an answer to whether the choice of demolishing the banks was positive or negative for the water quality of Torbiere. Once the role of the banks will be clarified, the effects of their possible restoration will be addressed.
How to cite: Volpini, S., Pilotti, M., Valerio, G., and Chapra, S. C.: Modeling the hydrodynamics of a wetland under strong anthropic pressures (Torbiere del Sebino, Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9981, https://doi.org/10.5194/egusphere-egu21-9981, 2021.
EGU21-12119 | vPICO presentations | GM6.4
Detection of land use-land cover changes in Anzali Wetland using a remote sensing-based approachAmirmoez Jamaat and Ammar Safaie
Wetlands are valuable ecological resources which play an essential and important role in the ecosystem of the region. Hence, there is a crucial need for monitoring and characterization of wetland changes caused by natural and anthropogenic disturbance. In this study, we developed a remote sensing-based approach to investigate long term land use/land cover changes (LULC) of Anzali Lagoon located in the southern coast of the Caspian Sea. In recent years, Anzali Wetland has experienced severe threats by human- and climate-induced changes and is drying up at an alarming rate. Here, an enhanced LULC change detection method is presented using a seasonal harmonic analysis of satellite image based on Normalized Difference Vegetation Index (NDVI) that combined with remotely-sensed thermal observations. Machine learning and object-oriented approaches were implemented on high-resolution satellite images to obtain a comprehensive land-use classification map of the study area. Then, wetland vegetation changes, such as marshes, were investigated during 2013 to 2020. Additionally, the long-term sea level trend in Caspian Sea was used, along with groundwater storage changes derived by GRACE satellite data, to study their impacts on wetland ecological changes. Results of the developed hybrid model indicate that the western and central parts of the wetland are more subjected to drought stress. Moreover, spatial and temporal changes in density of aquatic plants related to external stressors were identified in the wetland. The results of this study enhance a better understanding of long-term LULC changes in coastal wetlands in response to climate changes and anthropogenic activities.
How to cite: Jamaat, A. and Safaie, A.: Detection of land use-land cover changes in Anzali Wetland using a remote sensing-based approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12119, https://doi.org/10.5194/egusphere-egu21-12119, 2021.
Wetlands are valuable ecological resources which play an essential and important role in the ecosystem of the region. Hence, there is a crucial need for monitoring and characterization of wetland changes caused by natural and anthropogenic disturbance. In this study, we developed a remote sensing-based approach to investigate long term land use/land cover changes (LULC) of Anzali Lagoon located in the southern coast of the Caspian Sea. In recent years, Anzali Wetland has experienced severe threats by human- and climate-induced changes and is drying up at an alarming rate. Here, an enhanced LULC change detection method is presented using a seasonal harmonic analysis of satellite image based on Normalized Difference Vegetation Index (NDVI) that combined with remotely-sensed thermal observations. Machine learning and object-oriented approaches were implemented on high-resolution satellite images to obtain a comprehensive land-use classification map of the study area. Then, wetland vegetation changes, such as marshes, were investigated during 2013 to 2020. Additionally, the long-term sea level trend in Caspian Sea was used, along with groundwater storage changes derived by GRACE satellite data, to study their impacts on wetland ecological changes. Results of the developed hybrid model indicate that the western and central parts of the wetland are more subjected to drought stress. Moreover, spatial and temporal changes in density of aquatic plants related to external stressors were identified in the wetland. The results of this study enhance a better understanding of long-term LULC changes in coastal wetlands in response to climate changes and anthropogenic activities.
How to cite: Jamaat, A. and Safaie, A.: Detection of land use-land cover changes in Anzali Wetland using a remote sensing-based approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12119, https://doi.org/10.5194/egusphere-egu21-12119, 2021.
EGU21-15055 | vPICO presentations | GM6.4
Mining Contamination Disrupts Successional Change in Salt MarshesChris Smillie
Salt marshes can generally be considered as sinks for metals. Research into salt marshes in Cornwall, UK suggests those estuaries heavily impacted by mining contamination are characterised by a less diverse vegetation compared with a significantly less-polluted site. Assessment using the National Vegetation Classification on the mid-marsh confirmed an Armeria maritima-dominated community was to be found in the most metal-enriched salt marsh of Restronguet Creek. However, this plant was co-dominant with Plantago maritima in the moderately contaminated marsh of Lelant and not present at all in the Camel, which has been subject to limited mining related contamination. Using canonical correspondence analysis, vegetation abundance data was compared with geochemical variables within the sediment. Metals were studied using extractions to signal bioavailability. P. maritima was not associated with the very high metal levels found in Restronguet Creek. A. maritima, had some association with soluble copper and was closer to the bulk of metals than P. maritima. As tolerance to adverse conditions and competitiveness are mutually exclusive, A. maritima, therefore, exists in a successional relationship with P. maritima. A. maritima then appears to be outcompeted by P. maritima in marshes with low metal loadings. Moderately high metal content results in a loss of competitiveness by P. maritima allowing A. maritima to co-dominate. In extremely metal-rich estuaries, however, P. maritima is unable to compete, allowing A. maritima to colonize the mid-marsh. Vegetation community may, therefore, be useful as an indicator of the level of metal contamination.
How to cite: Smillie, C.: Mining Contamination Disrupts Successional Change in Salt Marshes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15055, https://doi.org/10.5194/egusphere-egu21-15055, 2021.
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Salt marshes can generally be considered as sinks for metals. Research into salt marshes in Cornwall, UK suggests those estuaries heavily impacted by mining contamination are characterised by a less diverse vegetation compared with a significantly less-polluted site. Assessment using the National Vegetation Classification on the mid-marsh confirmed an Armeria maritima-dominated community was to be found in the most metal-enriched salt marsh of Restronguet Creek. However, this plant was co-dominant with Plantago maritima in the moderately contaminated marsh of Lelant and not present at all in the Camel, which has been subject to limited mining related contamination. Using canonical correspondence analysis, vegetation abundance data was compared with geochemical variables within the sediment. Metals were studied using extractions to signal bioavailability. P. maritima was not associated with the very high metal levels found in Restronguet Creek. A. maritima, had some association with soluble copper and was closer to the bulk of metals than P. maritima. As tolerance to adverse conditions and competitiveness are mutually exclusive, A. maritima, therefore, exists in a successional relationship with P. maritima. A. maritima then appears to be outcompeted by P. maritima in marshes with low metal loadings. Moderately high metal content results in a loss of competitiveness by P. maritima allowing A. maritima to co-dominate. In extremely metal-rich estuaries, however, P. maritima is unable to compete, allowing A. maritima to colonize the mid-marsh. Vegetation community may, therefore, be useful as an indicator of the level of metal contamination.
How to cite: Smillie, C.: Mining Contamination Disrupts Successional Change in Salt Marshes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15055, https://doi.org/10.5194/egusphere-egu21-15055, 2021.
EGU21-13176 | vPICO presentations | GM6.4
Hurdles for implementation of constructed wetlands as Nature-based Solutions in SwedenJulián Andrés García Murcia, Fernando Jaramillo, and Sofia Wikström
Eutrophication in the Baltic Sea has been one of the major environmental issues during the last century partly due to extensive land-use change, loss of natural retention systems, and insufficient management. European legislation such as the Water Framework Directive (WFD) attempts to guide the recovery of good ecological status from freshwater to the sea, and suggests wetlands as ecosystems that can potentially contribute to achieving this goal. Wetlands are considered remarkable Nature-based Solutions (NbS) for improving water quality by diminishing the nutrient loads. This study aims to set a background context of the WFD implementation in Sweden, determine the status of constructed wetlands, and evaluate the stakeholders’ perspectives to identify the main administrative hurdles of wetland implementation in Sweden. For this purpose, we conducted a narrative review, database analysis, and semi-structured interviews with members of the institutions involved in water management. Our results show that it is essential to find synergies among the WFD and other directives to expand cross-sectoral cooperation, implement adjustments on the funding scheme that includes restoration and maintenance of natural wetlands, and increase compensation periods and cost ceiling. Likewise, it is crucial to perform significant improvements in the monitoring system, including more frequent data collection, as well as exploring new strategies to capture landowners’ interest in the implementation of NbS, such as the Catchment Officers program. Finally, we suggest paludiculture as a promising farming practice to increase proprietors’ attention on novel market alternatives, and in turn, to provide benefits for climate, water, and biodiversity.
Keywords Wetlands management · Water Framework Directive · Nature-based Solutions · Eutrophication · Semi-structured interviews · Sweden
How to cite: García Murcia, J. A., Jaramillo, F., and Wikström, S.: Hurdles for implementation of constructed wetlands as Nature-based Solutions in Sweden, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13176, https://doi.org/10.5194/egusphere-egu21-13176, 2021.
Eutrophication in the Baltic Sea has been one of the major environmental issues during the last century partly due to extensive land-use change, loss of natural retention systems, and insufficient management. European legislation such as the Water Framework Directive (WFD) attempts to guide the recovery of good ecological status from freshwater to the sea, and suggests wetlands as ecosystems that can potentially contribute to achieving this goal. Wetlands are considered remarkable Nature-based Solutions (NbS) for improving water quality by diminishing the nutrient loads. This study aims to set a background context of the WFD implementation in Sweden, determine the status of constructed wetlands, and evaluate the stakeholders’ perspectives to identify the main administrative hurdles of wetland implementation in Sweden. For this purpose, we conducted a narrative review, database analysis, and semi-structured interviews with members of the institutions involved in water management. Our results show that it is essential to find synergies among the WFD and other directives to expand cross-sectoral cooperation, implement adjustments on the funding scheme that includes restoration and maintenance of natural wetlands, and increase compensation periods and cost ceiling. Likewise, it is crucial to perform significant improvements in the monitoring system, including more frequent data collection, as well as exploring new strategies to capture landowners’ interest in the implementation of NbS, such as the Catchment Officers program. Finally, we suggest paludiculture as a promising farming practice to increase proprietors’ attention on novel market alternatives, and in turn, to provide benefits for climate, water, and biodiversity.
Keywords Wetlands management · Water Framework Directive · Nature-based Solutions · Eutrophication · Semi-structured interviews · Sweden
How to cite: García Murcia, J. A., Jaramillo, F., and Wikström, S.: Hurdles for implementation of constructed wetlands as Nature-based Solutions in Sweden, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13176, https://doi.org/10.5194/egusphere-egu21-13176, 2021.
GM6.5 – Coastal subsidence: Natural and anthropogenic drivers
EGU21-2944 | vPICO presentations | GM6.5
How to tackle spatial variability and temporal non-linearity in land subsidence in unconsolidated coastal environments?Philip S.J. Minderhoud, Claudia Zoccarato, Riccardo Xotta, and Pietro Teatini
Accurate land subsidence quantifications are of growing importance as relative sea-level rise in unconsolidated coastal environments is increasingly dominated by subsidence. Land subsidence, especially in unconsolidated settings, is the result of a complex interplay and sum of a range of different subsurface processes. As these processes can be spatially and temporally very variable, it requires more than (point and/or land surface) measurements to accurately quantify subsidence, especially when projections of subsidence are required for example to assess future relative sea-level rise. This requires first of all a thorough understanding of subsidence drivers and subsurface processes in a 4D perspective (3D including time) and secondly data interpretation methods and tools to handle the complex coupling of these interrelated processes to enable spatial-temporal quantification and projection of coastal subsidence.
We present a set of novel approaches, with which we aim to move our capacity to accurately capture and simulate the highly dynamic behaviour of subsidence processes. The approaches range from novel field experiments to advanced interpretation of sedimentary information in coastal-deltaic setting to gain important input for numerical modelling, and to newly-developed state-of-the-art 3D numerical simulators. Through these combined methodologies we aim to improve our capacity to assess both natural subsidence processes, like natural compaction, and anthropogenic-induced processes, like aquifer-system compaction following overexploitation in unconsolidated settings. This will ultimately contribute, for example through scenario modelling of anthropogenic drivers, to create reliable future projections of land subsidence which will enable sound projections of relative sea-level rise.
How to cite: Minderhoud, P. S. J., Zoccarato, C., Xotta, R., and Teatini, P.: How to tackle spatial variability and temporal non-linearity in land subsidence in unconsolidated coastal environments?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2944, https://doi.org/10.5194/egusphere-egu21-2944, 2021.
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Accurate land subsidence quantifications are of growing importance as relative sea-level rise in unconsolidated coastal environments is increasingly dominated by subsidence. Land subsidence, especially in unconsolidated settings, is the result of a complex interplay and sum of a range of different subsurface processes. As these processes can be spatially and temporally very variable, it requires more than (point and/or land surface) measurements to accurately quantify subsidence, especially when projections of subsidence are required for example to assess future relative sea-level rise. This requires first of all a thorough understanding of subsidence drivers and subsurface processes in a 4D perspective (3D including time) and secondly data interpretation methods and tools to handle the complex coupling of these interrelated processes to enable spatial-temporal quantification and projection of coastal subsidence.
We present a set of novel approaches, with which we aim to move our capacity to accurately capture and simulate the highly dynamic behaviour of subsidence processes. The approaches range from novel field experiments to advanced interpretation of sedimentary information in coastal-deltaic setting to gain important input for numerical modelling, and to newly-developed state-of-the-art 3D numerical simulators. Through these combined methodologies we aim to improve our capacity to assess both natural subsidence processes, like natural compaction, and anthropogenic-induced processes, like aquifer-system compaction following overexploitation in unconsolidated settings. This will ultimately contribute, for example through scenario modelling of anthropogenic drivers, to create reliable future projections of land subsidence which will enable sound projections of relative sea-level rise.
How to cite: Minderhoud, P. S. J., Zoccarato, C., Xotta, R., and Teatini, P.: How to tackle spatial variability and temporal non-linearity in land subsidence in unconsolidated coastal environments?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2944, https://doi.org/10.5194/egusphere-egu21-2944, 2021.
EGU21-2889 | vPICO presentations | GM6.5 | Highlight
Relative sea-level rise scenario for 2100 along the coasts of south eastern Sicily by GNSS and InSAR data, satellite images and high-resolution topographyMarco Anzidei, Giovanni Scicchitano, Giovanni Scardino, Christian Bignami, Cristiano Tolomei, Antonio Vecchio, Enrico Serpelloni, Vincenzo De Santis, Carmelo Monaco, Maurilio Milella, Arcangelo Piscitelli, Giuseppe Mastronuzzi, and Luca Pizzimenti
The global sea-level rise (SLR) projections for the next decades are the basis for developing flooding maps that depict the expected hazard scenarios. However, the spatially variable land subsidence has generally not been considered in the current projections. In this study, we use geodetic data from global navigation satellite system (GNSS), synthetic aperture radar interferometric measurements (InSAR) and sea-level data from tidal stations to show subsidence rates and SLR along the coast between Catania and Marzamemi, in south-eastern Sicily (southern Italy). This is one of the most active tectonic areas of the Mediterranean basin, which is affected to accelerated SLR, continuous coastal retreat and increasing effects of flooding and storms surges. We focus on six selected areas, which show valuable coastal infrastructures and natural reserves where the expected SLR in the next years could be a potential cause of significant land flooding and morphological changes of the coastal strip. Through a multidisciplinary study, the multi-temporal flooding scenarios until 2100, have been estimated. Results are based on the spatially variable rates of vertical land movements (VLM), the topographic features of the area provided by airborne Light Detection And Ranging (LiDAR) data and the Intergovernmental Panel on Climate Change (IPCC) projections of SLR in the Representative Concentration Pathways RCP2.6 and RCP8.5 emission scenarios. In addition, from the analysis of the time series of optical satellite images, a coastal retreat up to 70 m has been observed at the Ciane river mouth (Siracusa) in the time span 2001-2019. Our results show a diffuse land subsidence locally exceeding 10 ± 2.0 mm/yr-1 in some areas, due to compacting artificial landfill, salt marshes and Holocene soft deposits. Given ongoing land subsidence a high end of RSLR in the RCP8.5 at 0.52± 0.05 m and 1.52±0.13 m is expected for 2050 AD and 2100 AD, respectively, with a projected area of about 9.7 km2 that will be vulnerable to inundation in the next 80 years.
How to cite: Anzidei, M., Scicchitano, G., Scardino, G., Bignami, C., Tolomei, C., Vecchio, A., Serpelloni, E., De Santis, V., Monaco, C., Milella, M., Piscitelli, A., Mastronuzzi, G., and Pizzimenti, L.: Relative sea-level rise scenario for 2100 along the coasts of south eastern Sicily by GNSS and InSAR data, satellite images and high-resolution topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2889, https://doi.org/10.5194/egusphere-egu21-2889, 2021.
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The global sea-level rise (SLR) projections for the next decades are the basis for developing flooding maps that depict the expected hazard scenarios. However, the spatially variable land subsidence has generally not been considered in the current projections. In this study, we use geodetic data from global navigation satellite system (GNSS), synthetic aperture radar interferometric measurements (InSAR) and sea-level data from tidal stations to show subsidence rates and SLR along the coast between Catania and Marzamemi, in south-eastern Sicily (southern Italy). This is one of the most active tectonic areas of the Mediterranean basin, which is affected to accelerated SLR, continuous coastal retreat and increasing effects of flooding and storms surges. We focus on six selected areas, which show valuable coastal infrastructures and natural reserves where the expected SLR in the next years could be a potential cause of significant land flooding and morphological changes of the coastal strip. Through a multidisciplinary study, the multi-temporal flooding scenarios until 2100, have been estimated. Results are based on the spatially variable rates of vertical land movements (VLM), the topographic features of the area provided by airborne Light Detection And Ranging (LiDAR) data and the Intergovernmental Panel on Climate Change (IPCC) projections of SLR in the Representative Concentration Pathways RCP2.6 and RCP8.5 emission scenarios. In addition, from the analysis of the time series of optical satellite images, a coastal retreat up to 70 m has been observed at the Ciane river mouth (Siracusa) in the time span 2001-2019. Our results show a diffuse land subsidence locally exceeding 10 ± 2.0 mm/yr-1 in some areas, due to compacting artificial landfill, salt marshes and Holocene soft deposits. Given ongoing land subsidence a high end of RSLR in the RCP8.5 at 0.52± 0.05 m and 1.52±0.13 m is expected for 2050 AD and 2100 AD, respectively, with a projected area of about 9.7 km2 that will be vulnerable to inundation in the next 80 years.
How to cite: Anzidei, M., Scicchitano, G., Scardino, G., Bignami, C., Tolomei, C., Vecchio, A., Serpelloni, E., De Santis, V., Monaco, C., Milella, M., Piscitelli, A., Mastronuzzi, G., and Pizzimenti, L.: Relative sea-level rise scenario for 2100 along the coasts of south eastern Sicily by GNSS and InSAR data, satellite images and high-resolution topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2889, https://doi.org/10.5194/egusphere-egu21-2889, 2021.
EGU21-3671 | vPICO presentations | GM6.5
Monitoring on land subsidence in reclaimed land with space-based synthetic aperture radar observations.Seo-Woo Park and Sang-Hoon Hong
Land subsidence is often occurred by compaction of alluvial sediments due to groundwater extraction and threatens invaluable lives and properties. Space-based interferometric Synthetic Aperture Radar (SAR) observation has been widely used to estimate surface displacement precisely. Especially, Small BAseline Subset (SBAS) technique with SAR Interferometry (InSAR) could serve to monitor a time-series of the land subsidence. In this study, the SBAS with L-band ALOS PALSAR and C-band Sentinel-1 observations have been applied to investigate the land subsidence in Noksan reclaimed land, Busan, South Korea. The average velocity showing the largest displacement is -3.40 cm/year from ALOS PALSAR and -2.17 cm/year with Sentinel-1 dataset at the line of sight (LOS) direction. An annual subsidence rate of -2.77 cm/year was estimated assuming that the surface has been deformed linearly for the data acquisition period.
How to cite: Park, S.-W. and Hong, S.-H.: Monitoring on land subsidence in reclaimed land with space-based synthetic aperture radar observations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3671, https://doi.org/10.5194/egusphere-egu21-3671, 2021.
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Land subsidence is often occurred by compaction of alluvial sediments due to groundwater extraction and threatens invaluable lives and properties. Space-based interferometric Synthetic Aperture Radar (SAR) observation has been widely used to estimate surface displacement precisely. Especially, Small BAseline Subset (SBAS) technique with SAR Interferometry (InSAR) could serve to monitor a time-series of the land subsidence. In this study, the SBAS with L-band ALOS PALSAR and C-band Sentinel-1 observations have been applied to investigate the land subsidence in Noksan reclaimed land, Busan, South Korea. The average velocity showing the largest displacement is -3.40 cm/year from ALOS PALSAR and -2.17 cm/year with Sentinel-1 dataset at the line of sight (LOS) direction. An annual subsidence rate of -2.77 cm/year was estimated assuming that the surface has been deformed linearly for the data acquisition period.
How to cite: Park, S.-W. and Hong, S.-H.: Monitoring on land subsidence in reclaimed land with space-based synthetic aperture radar observations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3671, https://doi.org/10.5194/egusphere-egu21-3671, 2021.
EGU21-3734 | vPICO presentations | GM6.5 | Highlight
Mapping Land Subsidence in Pekalongan, Indonesia using Time Series Interferometry and Optimized Hot Spot Analysis with Sentinel-1 SAR DataWahyu Luqmanul Hakim, Seul Ki Lee, and Chang-Wook Lee
Floods in Pekalongan, Indonesia often occur due to the overflowing of river water during heavy monsoon rain. While the northern coast area of Pekalongan which located adjacent to the Java sea was affected by coastal floods due to sea-level rise. The flood conditions in every area were exacerbated by land subsidence and lead to coastal inundation. Monitoring land subsidence in Pekalongan becomes important to predict the further possible land subsidence occurrence area and mitigate the possible hazard caused by land subsidence. The analysis of land subsidence is much easier since the existence of radar satellites. This study used Synthetic Aperture Radar (SAR) datasets from the Sentinel-1 radar satellite between 2017 and 2020 in descending tracks. The data was processed through a time-series Interferometry SAR (InSAR) method based on the Stanford Methods for Persistent Scatterer (StaMPS) algorithm to provide accurate measurements over large areas by improving the selection of coherent pixels and reducing atmosphere noises. The result of persistent scatterer points then spatially clustered using Optimized Hot Spot Analysis (OHSA) to estimate significant points statistically and define them as the hot spot points. The results of time-series vertical deformation in Pekalongan were compared with the GPS station measurements. The comparison showed a good correlation in deformation patterns between time-series InSAR and GPS measurements. Our study revealed that the land subsidence in Pekalongan occurred mostly in settlement areas under the young alluvium soil which did not support the maximum compression from many buildings. Another cause of land subsidence in Pekalongan was the excessive groundwater extraction in the settlement areas could reduce the effective stress of pore pressure and lead to compaction in the aquifer areas. The time-series method that using the StaMPS algorithm and Optimized Hot Spot Analysis in this study can be applied for monitoring land subsidence in another area and from all-terrain.
How to cite: Hakim, W. L., Lee, S. K., and Lee, C.-W.: Mapping Land Subsidence in Pekalongan, Indonesia using Time Series Interferometry and Optimized Hot Spot Analysis with Sentinel-1 SAR Data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3734, https://doi.org/10.5194/egusphere-egu21-3734, 2021.
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Floods in Pekalongan, Indonesia often occur due to the overflowing of river water during heavy monsoon rain. While the northern coast area of Pekalongan which located adjacent to the Java sea was affected by coastal floods due to sea-level rise. The flood conditions in every area were exacerbated by land subsidence and lead to coastal inundation. Monitoring land subsidence in Pekalongan becomes important to predict the further possible land subsidence occurrence area and mitigate the possible hazard caused by land subsidence. The analysis of land subsidence is much easier since the existence of radar satellites. This study used Synthetic Aperture Radar (SAR) datasets from the Sentinel-1 radar satellite between 2017 and 2020 in descending tracks. The data was processed through a time-series Interferometry SAR (InSAR) method based on the Stanford Methods for Persistent Scatterer (StaMPS) algorithm to provide accurate measurements over large areas by improving the selection of coherent pixels and reducing atmosphere noises. The result of persistent scatterer points then spatially clustered using Optimized Hot Spot Analysis (OHSA) to estimate significant points statistically and define them as the hot spot points. The results of time-series vertical deformation in Pekalongan were compared with the GPS station measurements. The comparison showed a good correlation in deformation patterns between time-series InSAR and GPS measurements. Our study revealed that the land subsidence in Pekalongan occurred mostly in settlement areas under the young alluvium soil which did not support the maximum compression from many buildings. Another cause of land subsidence in Pekalongan was the excessive groundwater extraction in the settlement areas could reduce the effective stress of pore pressure and lead to compaction in the aquifer areas. The time-series method that using the StaMPS algorithm and Optimized Hot Spot Analysis in this study can be applied for monitoring land subsidence in another area and from all-terrain.
How to cite: Hakim, W. L., Lee, S. K., and Lee, C.-W.: Mapping Land Subsidence in Pekalongan, Indonesia using Time Series Interferometry and Optimized Hot Spot Analysis with Sentinel-1 SAR Data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3734, https://doi.org/10.5194/egusphere-egu21-3734, 2021.
EGU21-12174 | vPICO presentations | GM6.5 | Highlight
Observations of uplift and subsidence along the North American Pacific coast – illuminating the geodynamic complexity of an active marginMaryam Yousefi, Glenn Milne, Shaoyang Li, Kelin Wang, Alan Bartholet, Ryan Love, and Lev Tarasov
The Pacific Coast of Central North America is a geodynamically complex region subject to various geophysical processes with different patterns of vertical land motion. It includes two distinct tectonic regimes: the Cascadia subduction zone and the strike-slip San Andreas fault system. The vertical land motion in this region reflects not only tectonic activity of these plate boundaries, but also isostatic signals associated with different loading effects such as the (de)glaciation of North American ice sheets and the more contemporary, anthropogenically-related groundwater extraction and mountain glacier mass loss. These processes occur over a broad range of timescales and are observed by a variety of measuring techniques.
Here we combine geological measurements of relative sea level (RSL) change with contemporary observations of vertical land motion inferred from geodetic data to decipher and thus better understand the contribution from various individual processes. Our results suggest that contemporary vertical land motion is dominated by Cascadia interseismic deformation and the isostatic response to the retreat of the North American ice sheets but is also influenced by other contemporary processes. We present some model results that illustrate the contributions of the above-mentioned processes to RSL projections along this coastline.
How to cite: Yousefi, M., Milne, G., Li, S., Wang, K., Bartholet, A., Love, R., and Tarasov, L.: Observations of uplift and subsidence along the North American Pacific coast – illuminating the geodynamic complexity of an active margin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12174, https://doi.org/10.5194/egusphere-egu21-12174, 2021.
The Pacific Coast of Central North America is a geodynamically complex region subject to various geophysical processes with different patterns of vertical land motion. It includes two distinct tectonic regimes: the Cascadia subduction zone and the strike-slip San Andreas fault system. The vertical land motion in this region reflects not only tectonic activity of these plate boundaries, but also isostatic signals associated with different loading effects such as the (de)glaciation of North American ice sheets and the more contemporary, anthropogenically-related groundwater extraction and mountain glacier mass loss. These processes occur over a broad range of timescales and are observed by a variety of measuring techniques.
Here we combine geological measurements of relative sea level (RSL) change with contemporary observations of vertical land motion inferred from geodetic data to decipher and thus better understand the contribution from various individual processes. Our results suggest that contemporary vertical land motion is dominated by Cascadia interseismic deformation and the isostatic response to the retreat of the North American ice sheets but is also influenced by other contemporary processes. We present some model results that illustrate the contributions of the above-mentioned processes to RSL projections along this coastline.
How to cite: Yousefi, M., Milne, G., Li, S., Wang, K., Bartholet, A., Love, R., and Tarasov, L.: Observations of uplift and subsidence along the North American Pacific coast – illuminating the geodynamic complexity of an active margin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12174, https://doi.org/10.5194/egusphere-egu21-12174, 2021.
EGU21-6369 | vPICO presentations | GM6.5
Unraveling anthropogenic causes of subsidence in the coastal plain of Friesland (NL)Kay Koster, Thibault Candela, Joana Esteves Martins, Peter Fokker, Aris Lourens, Willem Dabekaussen, Madelon Molhoek, Merijn De Bakker, Manon Verberne, and Andrei Bocin-Dumitriu
The coastal plains of the Netherlands are subject to anthropogenic and natural subsidence with rates which are an order of magnitude higher than sea-level rise. Because one-third of the Netherlands lies below mean sea level, subsidence may threaten the country’s subsistence with major socio-economic consequences. Subsidence is a normal natural process but is overprinted and accelerated by anthropogenic activities which drives deep or shallow processes. Deep processes are caused by the extraction of hydrocarbons and salt, whereas shallow processes are primarily caused by lowering of phreatic groundwater levels. At present, the relative contribution of each process to total subsidence (i.e. natural plus anthropogenic) is unclear. Such information is important for stakeholders to support decision making on subsidence mitigation and it should be substantiated with independent scientific studies.
We present the outline of a hybrid Artificial Intelligence (AI) big data and model workflow to disentangle different subsidence forcing and we report on preliminary results for an area covering a gas field in the peat-rich Friesland coastal plain. The proposed workflow is a hybrid approach between a knowledge-based physical model and machine-learning techniques. The big input data comprises a suite of static (structural model) and time-dependent subsurface data (phreatic groundwater level, reservoir pressure), and geodetic measurements. Geomechanical models provide the connection between the drivers (groundwater levels and reservoir pressures) and the surface movement.
How to cite: Koster, K., Candela, T., Esteves Martins, J., Fokker, P., Lourens, A., Dabekaussen, W., Molhoek, M., De Bakker, M., Verberne, M., and Bocin-Dumitriu, A.: Unraveling anthropogenic causes of subsidence in the coastal plain of Friesland (NL) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6369, https://doi.org/10.5194/egusphere-egu21-6369, 2021.
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The coastal plains of the Netherlands are subject to anthropogenic and natural subsidence with rates which are an order of magnitude higher than sea-level rise. Because one-third of the Netherlands lies below mean sea level, subsidence may threaten the country’s subsistence with major socio-economic consequences. Subsidence is a normal natural process but is overprinted and accelerated by anthropogenic activities which drives deep or shallow processes. Deep processes are caused by the extraction of hydrocarbons and salt, whereas shallow processes are primarily caused by lowering of phreatic groundwater levels. At present, the relative contribution of each process to total subsidence (i.e. natural plus anthropogenic) is unclear. Such information is important for stakeholders to support decision making on subsidence mitigation and it should be substantiated with independent scientific studies.
We present the outline of a hybrid Artificial Intelligence (AI) big data and model workflow to disentangle different subsidence forcing and we report on preliminary results for an area covering a gas field in the peat-rich Friesland coastal plain. The proposed workflow is a hybrid approach between a knowledge-based physical model and machine-learning techniques. The big input data comprises a suite of static (structural model) and time-dependent subsurface data (phreatic groundwater level, reservoir pressure), and geodetic measurements. Geomechanical models provide the connection between the drivers (groundwater levels and reservoir pressures) and the surface movement.
How to cite: Koster, K., Candela, T., Esteves Martins, J., Fokker, P., Lourens, A., Dabekaussen, W., Molhoek, M., De Bakker, M., Verberne, M., and Bocin-Dumitriu, A.: Unraveling anthropogenic causes of subsidence in the coastal plain of Friesland (NL) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6369, https://doi.org/10.5194/egusphere-egu21-6369, 2021.
EGU21-4856 | vPICO presentations | GM6.5
Determining sedimentation rates by accounting for past compaction in the Mekong Delta as input for 3D delta evolution modellingSelena Baldan, Philip S.J. Minderhoud, Claudia Zoccarato, and Pietro Teatini
The Vietnamese Mekong River Delta has been formed by the deposition of soft, fine-grained sediments during the last thousands of years. Natural compaction of these unconsolidated deposits over time and with increased overburden load is one of the main drivers of subsidence in this delta. High rates of natural compaction may have a considerable increased flood vulnerability of the lowly elevated delta plain and ultimately result in permanent inundation.
Following the loading history of accumulating sediments during the Holocene delta evolution, it is possible to estimate delta-wide present-day natural compaction rates. The ultimate goal of this study is to provide reliable input data on Holocene sedimentation rate throughout the Mekong Delta for a novel 3D numerical model to simulate delta formation and its dynamic evolution during the late Holocene. In order to achieve this, it is fundamental to first take into account previous compaction that already happened to the sediments in the past to estimate the original sedimentation rate of Holocene sediments.
We employed a 1D decompaction module to compute the original, uncompacted thickness of Holocene delta sequences from lithological borelogs to estimate the amount of virgin sediment that has been deposited in time. The original thickness of Holocene sediments was determined after investigating geomechanical properties of Holocene deposits and decompaction of lithological boreholes spread over the delta. To determine the sedimentation rate for the borelogs with missing dating information, the age was estimated by using a linear distance interpolation of age isochrones starting from a limited number of boreholes, where both stratigraphy and sediment ages are available.
As a final step, the estimated sedimentation rates from each of the borelogs are interpolated to arrive at delta-wide sedimentation rates and lithology during the Late Holocene. This provides the required input data for the 3D model to simulate natural consolidation during the delta evolution and accurately assess present natural compaction rates.
How to cite: Baldan, S., Minderhoud, P. S. J., Zoccarato, C., and Teatini, P.: Determining sedimentation rates by accounting for past compaction in the Mekong Delta as input for 3D delta evolution modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4856, https://doi.org/10.5194/egusphere-egu21-4856, 2021.
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The Vietnamese Mekong River Delta has been formed by the deposition of soft, fine-grained sediments during the last thousands of years. Natural compaction of these unconsolidated deposits over time and with increased overburden load is one of the main drivers of subsidence in this delta. High rates of natural compaction may have a considerable increased flood vulnerability of the lowly elevated delta plain and ultimately result in permanent inundation.
Following the loading history of accumulating sediments during the Holocene delta evolution, it is possible to estimate delta-wide present-day natural compaction rates. The ultimate goal of this study is to provide reliable input data on Holocene sedimentation rate throughout the Mekong Delta for a novel 3D numerical model to simulate delta formation and its dynamic evolution during the late Holocene. In order to achieve this, it is fundamental to first take into account previous compaction that already happened to the sediments in the past to estimate the original sedimentation rate of Holocene sediments.
We employed a 1D decompaction module to compute the original, uncompacted thickness of Holocene delta sequences from lithological borelogs to estimate the amount of virgin sediment that has been deposited in time. The original thickness of Holocene sediments was determined after investigating geomechanical properties of Holocene deposits and decompaction of lithological boreholes spread over the delta. To determine the sedimentation rate for the borelogs with missing dating information, the age was estimated by using a linear distance interpolation of age isochrones starting from a limited number of boreholes, where both stratigraphy and sediment ages are available.
As a final step, the estimated sedimentation rates from each of the borelogs are interpolated to arrive at delta-wide sedimentation rates and lithology during the Late Holocene. This provides the required input data for the 3D model to simulate natural consolidation during the delta evolution and accurately assess present natural compaction rates.
How to cite: Baldan, S., Minderhoud, P. S. J., Zoccarato, C., and Teatini, P.: Determining sedimentation rates by accounting for past compaction in the Mekong Delta as input for 3D delta evolution modelling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4856, https://doi.org/10.5194/egusphere-egu21-4856, 2021.
EGU21-3727 | vPICO presentations | GM6.5
Visualizing uncertainty of one-dimensional land subsidence prediction by preparing various local optimal solutions with a genetic algorithmKento Akitaya and Masaatsu Aichi
This study tried to visualize the predictive uncertainty while predicting future land subsidence caused by the groundwater pumping. Because land subsidence modeling is highly uncertain, it is impossible to determine the distribution of subsurface physical property values uniquely. Therefore, we prepared various local optimal solutions through the inversion analysis with a genetic algorithm in order to visualize land subsidence prediction uncertainty. The inversion analysis was conducted using the long-term land subsidence monitoring data at Kawajima in the Kanto Plain, Japan. In this study site, the seasonal groundwater level fluctuations have caused plastic compaction in summer and elastic expansion in winter every year. Obtained multiple sets of subsurface properties were within the range of typical values in the existing literature and satisfactorily reproduced the observed subsidence, showing that the inversion analysis worked well. In addition, the groundwater level scenario analysis was conducted using obtained property sets. This revealed that the subsidences predicted for a sudden groundwater level drop and rapid recovery scenario are more volatile than the subsidences predicted for the stable scenario. This means that it is important to have multiple sets of subsurface properties to predict future land subsidence caused by unprecedented groundwater level fluctuations.
How to cite: Akitaya, K. and Aichi, M.: Visualizing uncertainty of one-dimensional land subsidence prediction by preparing various local optimal solutions with a genetic algorithm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3727, https://doi.org/10.5194/egusphere-egu21-3727, 2021.
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This study tried to visualize the predictive uncertainty while predicting future land subsidence caused by the groundwater pumping. Because land subsidence modeling is highly uncertain, it is impossible to determine the distribution of subsurface physical property values uniquely. Therefore, we prepared various local optimal solutions through the inversion analysis with a genetic algorithm in order to visualize land subsidence prediction uncertainty. The inversion analysis was conducted using the long-term land subsidence monitoring data at Kawajima in the Kanto Plain, Japan. In this study site, the seasonal groundwater level fluctuations have caused plastic compaction in summer and elastic expansion in winter every year. Obtained multiple sets of subsurface properties were within the range of typical values in the existing literature and satisfactorily reproduced the observed subsidence, showing that the inversion analysis worked well. In addition, the groundwater level scenario analysis was conducted using obtained property sets. This revealed that the subsidences predicted for a sudden groundwater level drop and rapid recovery scenario are more volatile than the subsidences predicted for the stable scenario. This means that it is important to have multiple sets of subsurface properties to predict future land subsidence caused by unprecedented groundwater level fluctuations.
How to cite: Akitaya, K. and Aichi, M.: Visualizing uncertainty of one-dimensional land subsidence prediction by preparing various local optimal solutions with a genetic algorithm, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3727, https://doi.org/10.5194/egusphere-egu21-3727, 2021.
EGU21-7698 | vPICO presentations | GM6.5 | Highlight
Land subsidence and sea-level rise for six coastal zones of the Mediterranean region: implications for flooding scenarios for 2100 from the SAVEMEDCOASTS-2 projectMichele Crosetto, Marco Anzidei, Giovanna Forlenza, José Navarro, Petros Patias, Charalampos Georgiadis, Fawzi Doumaz, Maria Lucia Trivigno, Antonio Falciano, Michele Greco, Enrico Serpelloni, Antonio Vecchio, Qi Gao, and Anna Barra
Here we show and discuss the first results arising from the SAVEMEDCOASTS-2 Project (Sea Level Rise Scenarios along the Mediterranean Coasts - 2, funded by the European Commission ECHO), which aims to respond to the need for people and assets prevention from natural disasters in the Mediterranean coastal zones placed at less than 1 m above sea level, which are vulnerable to the combined effect of sea-level rise and land subsidence.
We use geodetic data from global navigation satellite system (GNSS), synthetic aperture radar interferometric measurements (InSAR), Lidar and tide gauge data, and the latest IPCC - SROCC projections of sea-level rise released by the Intergovernmental Panel on Climate Change, to estimate the Relative Sea Level Rise to realize marine flooding scenarios expected for 2100 AD in six targeted areas of the Mediterranean region.
We focus on the Ebro (Spain), Rhone (France), and Nile (Egypt) river deltas; the reclamation area of Basento (Italy), the coastal plain of Thessaloniki (Greece), and the Venice lagoon (Italy). Results, from Copernicus Sentinel-1A (S1A) and Sentinel-1B (S1B) sensors, highlighted the variable spatial rates of land subsidence up to some cm/yr in most of the investigated areas representing a relevant driver of local SLR. All the investigated zones show valuable coastal infrastructures and natural reserves where SLR and land subsidence are exacerbating coastal retreat, land flooding, and storm surges.
The hazard implications for the population living along the shore should push land planners and decision-makers to take into account scenarios similar to that reported in this study for cognizant coastal management.
How to cite: Crosetto, M., Anzidei, M., Forlenza, G., Navarro, J., Patias, P., Georgiadis, C., Doumaz, F., Trivigno, M. L., Falciano, A., Greco, M., Serpelloni, E., Vecchio, A., Gao, Q., and Barra, A.: Land subsidence and sea-level rise for six coastal zones of the Mediterranean region: implications for flooding scenarios for 2100 from the SAVEMEDCOASTS-2 project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7698, https://doi.org/10.5194/egusphere-egu21-7698, 2021.
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Here we show and discuss the first results arising from the SAVEMEDCOASTS-2 Project (Sea Level Rise Scenarios along the Mediterranean Coasts - 2, funded by the European Commission ECHO), which aims to respond to the need for people and assets prevention from natural disasters in the Mediterranean coastal zones placed at less than 1 m above sea level, which are vulnerable to the combined effect of sea-level rise and land subsidence.
We use geodetic data from global navigation satellite system (GNSS), synthetic aperture radar interferometric measurements (InSAR), Lidar and tide gauge data, and the latest IPCC - SROCC projections of sea-level rise released by the Intergovernmental Panel on Climate Change, to estimate the Relative Sea Level Rise to realize marine flooding scenarios expected for 2100 AD in six targeted areas of the Mediterranean region.
We focus on the Ebro (Spain), Rhone (France), and Nile (Egypt) river deltas; the reclamation area of Basento (Italy), the coastal plain of Thessaloniki (Greece), and the Venice lagoon (Italy). Results, from Copernicus Sentinel-1A (S1A) and Sentinel-1B (S1B) sensors, highlighted the variable spatial rates of land subsidence up to some cm/yr in most of the investigated areas representing a relevant driver of local SLR. All the investigated zones show valuable coastal infrastructures and natural reserves where SLR and land subsidence are exacerbating coastal retreat, land flooding, and storm surges.
The hazard implications for the population living along the shore should push land planners and decision-makers to take into account scenarios similar to that reported in this study for cognizant coastal management.
How to cite: Crosetto, M., Anzidei, M., Forlenza, G., Navarro, J., Patias, P., Georgiadis, C., Doumaz, F., Trivigno, M. L., Falciano, A., Greco, M., Serpelloni, E., Vecchio, A., Gao, Q., and Barra, A.: Land subsidence and sea-level rise for six coastal zones of the Mediterranean region: implications for flooding scenarios for 2100 from the SAVEMEDCOASTS-2 project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7698, https://doi.org/10.5194/egusphere-egu21-7698, 2021.
EGU21-10968 | vPICO presentations | GM6.5
Coastal changes through time is the only constant: Case study of west coast of Naxos Island, Cyclades, GreeceNiki Evelpidou, Alexandros Petropoulos, Anna Karkani, and Giannis Saitis
Coastal areas include various landforms, such as dunes, lagoons and wetlands, which constitutes them as areas of particular environmental and geomorphological values. Coastal lagoons and dunes are of great environmental importance, given that, among others, they provide habitat for rare species of flora and fauna, but they also contribute to the protection of the coastal zone from sea level rise, storms, etc. Although these features are unique elements for sustainable development and are of great importance to the natural environment and economy, due to their relatively small size, they are one of the most vulnerable and threatened ecosystems. Such a case is the western coast of Naxos Island, hosting several wetlands bordering with low-lying sand dunes.
Naxos island lies in the center of the Aegean Sea, being part of the Cyclades Island group. The western coasts of Naxos include a number of natural features, which have been inherited from their palaeogeographical evolution over the last 10,000 years. Typically, the western coastal zone is composed of a sandy beach, bordered by low lying sand dunes, lagoons and an alluvial plain. These systems are becoming increasingly vulnerable, due to natural processes such as intensity of waves, but also due to human interventions that have blocked sediment input to the coastal zone and the increasing touristic development. The erosion of the dunes, the intense storms, the sea level rise, extreme events such as storms or tsunamis, and the increased tourist "raid", will lead to marine flooding not only to the beach, but also to the lagoons and many acres of land (rural, residential areas).
The aim of our study is to assess the vulnerability of the western coasts of Naxos to sea level rise, considering both natural and anthropogenic pressures. For this purpose, we used a series of methodologies for the environmental and geomorphological study of the coastal zone and the shallow submarine area, which included: a) photointerpretation of aerial photographs from 1960 until today, b) systematic seasonal aerial monitoring by drone, since 2015, c) mapping of the coastal zone and topographic sections using DGPS and d) dune mapping and sampling, e) sampling of underwater beachrocks. Through our analysis we aim to better elucidate the impact of the relative sea level rise in the study area.
How to cite: Evelpidou, N., Petropoulos, A., Karkani, A., and Saitis, G.: Coastal changes through time is the only constant: Case study of west coast of Naxos Island, Cyclades, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10968, https://doi.org/10.5194/egusphere-egu21-10968, 2021.
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Coastal areas include various landforms, such as dunes, lagoons and wetlands, which constitutes them as areas of particular environmental and geomorphological values. Coastal lagoons and dunes are of great environmental importance, given that, among others, they provide habitat for rare species of flora and fauna, but they also contribute to the protection of the coastal zone from sea level rise, storms, etc. Although these features are unique elements for sustainable development and are of great importance to the natural environment and economy, due to their relatively small size, they are one of the most vulnerable and threatened ecosystems. Such a case is the western coast of Naxos Island, hosting several wetlands bordering with low-lying sand dunes.
Naxos island lies in the center of the Aegean Sea, being part of the Cyclades Island group. The western coasts of Naxos include a number of natural features, which have been inherited from their palaeogeographical evolution over the last 10,000 years. Typically, the western coastal zone is composed of a sandy beach, bordered by low lying sand dunes, lagoons and an alluvial plain. These systems are becoming increasingly vulnerable, due to natural processes such as intensity of waves, but also due to human interventions that have blocked sediment input to the coastal zone and the increasing touristic development. The erosion of the dunes, the intense storms, the sea level rise, extreme events such as storms or tsunamis, and the increased tourist "raid", will lead to marine flooding not only to the beach, but also to the lagoons and many acres of land (rural, residential areas).
The aim of our study is to assess the vulnerability of the western coasts of Naxos to sea level rise, considering both natural and anthropogenic pressures. For this purpose, we used a series of methodologies for the environmental and geomorphological study of the coastal zone and the shallow submarine area, which included: a) photointerpretation of aerial photographs from 1960 until today, b) systematic seasonal aerial monitoring by drone, since 2015, c) mapping of the coastal zone and topographic sections using DGPS and d) dune mapping and sampling, e) sampling of underwater beachrocks. Through our analysis we aim to better elucidate the impact of the relative sea level rise in the study area.
How to cite: Evelpidou, N., Petropoulos, A., Karkani, A., and Saitis, G.: Coastal changes through time is the only constant: Case study of west coast of Naxos Island, Cyclades, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10968, https://doi.org/10.5194/egusphere-egu21-10968, 2021.
EGU21-10710 | vPICO presentations | GM6.5
Reconciling geodetic and geologic estimates of coastal vertical land motion around the British IslesMakan A. Karegar, Simon E. Engelhart, Jürgen Kusche, Glenn A. Milne, and Sarah L. Bradley
Karegar et al. (2016, GRL) showed that independent estimates of vertical land motion from geodetic and geologic techniques are critical for understanding coastal surface motion caused by geological versus human-induced processes along the Atlantic coast of North America. Motivated by these results, we extend our analysis to the British Isles where good quality and spatially dense constraints are available from a continuous GNSS network and a state-of-the-art Holocene sea-level database. Glacial Isostatic Adjustment (GIA) along the Atlantic coast of North America causes the land surface to sink (up to -1.5 mm/yr), exacerbating tidal-induced flooding effects of sea-level rise. The British Isles are also subjected to proglacial forebulge collapse associated with the GIA response to the ancient Fennoscandian and British-Irish Ice Sheets. Here, we present an up-to-date and precise analysis based on continuous GNSS (combined GPS and GlONASS observations) and geologic records of late Holocene sea-level change to examine residuals between rates on these different timescales to determine if there is a significant residual and, if so, the processes responsible for the rate change.
How to cite: A. Karegar, M., E. Engelhart, S., Kusche, J., A. Milne, G., and L. Bradley, S.: Reconciling geodetic and geologic estimates of coastal vertical land motion around the British Isles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10710, https://doi.org/10.5194/egusphere-egu21-10710, 2021.
Karegar et al. (2016, GRL) showed that independent estimates of vertical land motion from geodetic and geologic techniques are critical for understanding coastal surface motion caused by geological versus human-induced processes along the Atlantic coast of North America. Motivated by these results, we extend our analysis to the British Isles where good quality and spatially dense constraints are available from a continuous GNSS network and a state-of-the-art Holocene sea-level database. Glacial Isostatic Adjustment (GIA) along the Atlantic coast of North America causes the land surface to sink (up to -1.5 mm/yr), exacerbating tidal-induced flooding effects of sea-level rise. The British Isles are also subjected to proglacial forebulge collapse associated with the GIA response to the ancient Fennoscandian and British-Irish Ice Sheets. Here, we present an up-to-date and precise analysis based on continuous GNSS (combined GPS and GlONASS observations) and geologic records of late Holocene sea-level change to examine residuals between rates on these different timescales to determine if there is a significant residual and, if so, the processes responsible for the rate change.
How to cite: A. Karegar, M., E. Engelhart, S., Kusche, J., A. Milne, G., and L. Bradley, S.: Reconciling geodetic and geologic estimates of coastal vertical land motion around the British Isles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10710, https://doi.org/10.5194/egusphere-egu21-10710, 2021.
GM6.6 – Coastal Zone Geomorphological Interactions: Natural versus Human-Induced Driving Factors
EGU21-8397 | vPICO presentations | GM6.6 | Highlight
What mechanisms trigger coastal flow slides?Patrick Barrineau
Some beaches regularly experience a rapid decrease in volume due to ‘coastal flow slides’. These events visually resemble subaerial landslides, but are subaqueous and located along river or tidal channels. Along a steeper shoreface, material eroded from the upper beach can be stored in deep water. In some cases, these events can remove thousands of cubic meters (m3) of beach sand in a few hours.
On several occasions in recent years, a flow slide has formed at Seabrook Island, South Carolina (USA). As of January 2021, there have been five events observed since July 2016. Surveys of a January 2017 event show the slide displaced ~25,000 m3 into deep water (15–20 m) along North Edisto River Inlet. This volume is comparable to hillside-scale slides observed in mountainous regions like the Blue Ridge, and similar-scale failures have been observed in the Netherlands, France, and Australia (Mastbergen, 2019).
The Seabrook flow slide is consistently located along a marginal flood channel of a relatively large ebb-dominant inlet, just below a quarrystone revetment protecting an upland development. In this particular location, erosion of the dry beach could cause undermining of the revetment. Historical charts suggest a small inlet was located along this portion of the beach as recently as ~1920. Reviews of available rainfall and water level data suggest exceptional (ie – near-record daily total) rainfall events and spring tide levels may coincide with observed flow slide events.
This study analyzes available meteorological, water level, geotechnical, and historical shoreline data to identify mechanisms affecting repeat coastal flow slide events at Seabrook Island (SC). A combination of excessive rainfall, spring tidal currents, and sediment characteristics all appear to affect these events. Because of the unpredictability of these events, and the dynamic nature of the inlet channel adjacent to this portion of the island, it is difficult to observe events in situ and identify specific mechanisms triggering flow slides. While a hard structural solution is unlikely to effectively mitigate the hazard in this location, providing an excess of beach sand may help maintain a shallower shoreface slope and mitigate future flow slides.
How to cite: Barrineau, P.: What mechanisms trigger coastal flow slides?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8397, https://doi.org/10.5194/egusphere-egu21-8397, 2021.
Some beaches regularly experience a rapid decrease in volume due to ‘coastal flow slides’. These events visually resemble subaerial landslides, but are subaqueous and located along river or tidal channels. Along a steeper shoreface, material eroded from the upper beach can be stored in deep water. In some cases, these events can remove thousands of cubic meters (m3) of beach sand in a few hours.
On several occasions in recent years, a flow slide has formed at Seabrook Island, South Carolina (USA). As of January 2021, there have been five events observed since July 2016. Surveys of a January 2017 event show the slide displaced ~25,000 m3 into deep water (15–20 m) along North Edisto River Inlet. This volume is comparable to hillside-scale slides observed in mountainous regions like the Blue Ridge, and similar-scale failures have been observed in the Netherlands, France, and Australia (Mastbergen, 2019).
The Seabrook flow slide is consistently located along a marginal flood channel of a relatively large ebb-dominant inlet, just below a quarrystone revetment protecting an upland development. In this particular location, erosion of the dry beach could cause undermining of the revetment. Historical charts suggest a small inlet was located along this portion of the beach as recently as ~1920. Reviews of available rainfall and water level data suggest exceptional (ie – near-record daily total) rainfall events and spring tide levels may coincide with observed flow slide events.
This study analyzes available meteorological, water level, geotechnical, and historical shoreline data to identify mechanisms affecting repeat coastal flow slide events at Seabrook Island (SC). A combination of excessive rainfall, spring tidal currents, and sediment characteristics all appear to affect these events. Because of the unpredictability of these events, and the dynamic nature of the inlet channel adjacent to this portion of the island, it is difficult to observe events in situ and identify specific mechanisms triggering flow slides. While a hard structural solution is unlikely to effectively mitigate the hazard in this location, providing an excess of beach sand may help maintain a shallower shoreface slope and mitigate future flow slides.
How to cite: Barrineau, P.: What mechanisms trigger coastal flow slides?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8397, https://doi.org/10.5194/egusphere-egu21-8397, 2021.
EGU21-10779 | vPICO presentations | GM6.6 | Highlight
Coastal dunes - A nature based coastal protection element exposed to exacerbated anthropogenic stressBjörn Mehrtens, Viktoria Kosmalla, Oliver Lojek, David Schürenkamp, and Nils Goseberg
Natural coastal dunes covered by vegetation are an essential component on many sandy coastlines worldwide and often provide the only physical protection against flooding by dissipating wave energy and enhancing erosion resilience. However, sea level rise, changing and widely intensifying coastal wave climates and storm surges constitute severe exacerbated stresses, calling into question the perseverance of such unique coastal ecosystems as dunes and their protective functions taken for granted.
Here we investigate the extensive coastal dune system of St. Peter-Ording, a major tourist draw of the German North Sea within a marine high energy zone. Lining the coast along 15 km, extending up to 1.5 km in cross-shore direction it covers an area of 18 sqkm characterized by overgrown dunes separating the tidal foreshore from the topographically flat hinterland. Featuring a dedicated, Germany wide unique, coastal protection function sets it apart from other national coastal dune systems - potentially creating a role model for mitigating coastal squeeze related driving factors, further adding to its awe-inspiring landscape character.
Consequently, the joint-research project ''Sandküste St. Peter Ording'' examines whether the local flood protection dune “Maleens Knoll”, a 16.6 m high natural coastal dune stretching a roughly 1.2 km long gap in the sea-dike defense, will continue to offer adequate protection in the future. Current hypothesis is, that due to the overgrowth with non-endemic and invasive vegetation species, the natural dynamic and self-adaptation of the system is impaired and will not withstand projected changes in coastal drivers. Therefore, the long-term goal is to develop a variety of nature-friendly flood protection measures to reinforce the dune and reduce its probability of failure during an extreme storm surge.
Possible options comprise the installation of hybrid systems, combining the existing dune core with one of the following structures: 1) a vertical wall to gain more stability during erosion of the sand cover, 2) rock filling to increase wave dissipation and reduce wave reflection and erosion and 3) geotextiles to provide a temporary and more environmentally protection against runup. The built-in materials will be covered with sand, to mimic the original landform and yield its previous degree of freedom regarding topographic adaptation. Another approach is to strengthen the resistance of the sand surface against aeolian and fluvial erosion. Through a microbiological process based on calcium carbonate precipitation (MICP), the strength can be increased in a particularly environmentally friendly way that saves raw materials. Furthermore, adapted or additional planting with a site-typical vegetation can promote sand accumulation at the surface and thereby stabilize the dune.
Large-scale physical model experiments will be performed in a wave flume to investigate the protection potential of the dune. First, the natural dune condition will be recreated and tested under a combination of water levels and wave conditions to investigate current and future load cases. Based on the findings, a second series of experiments will be conducted to determine which engineering methods are most appropriate to reinforce the dune and ensure its coastal protection character and retain its naturalness at the same time.
How to cite: Mehrtens, B., Kosmalla, V., Lojek, O., Schürenkamp, D., and Goseberg, N.: Coastal dunes - A nature based coastal protection element exposed to exacerbated anthropogenic stress, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10779, https://doi.org/10.5194/egusphere-egu21-10779, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Natural coastal dunes covered by vegetation are an essential component on many sandy coastlines worldwide and often provide the only physical protection against flooding by dissipating wave energy and enhancing erosion resilience. However, sea level rise, changing and widely intensifying coastal wave climates and storm surges constitute severe exacerbated stresses, calling into question the perseverance of such unique coastal ecosystems as dunes and their protective functions taken for granted.
Here we investigate the extensive coastal dune system of St. Peter-Ording, a major tourist draw of the German North Sea within a marine high energy zone. Lining the coast along 15 km, extending up to 1.5 km in cross-shore direction it covers an area of 18 sqkm characterized by overgrown dunes separating the tidal foreshore from the topographically flat hinterland. Featuring a dedicated, Germany wide unique, coastal protection function sets it apart from other national coastal dune systems - potentially creating a role model for mitigating coastal squeeze related driving factors, further adding to its awe-inspiring landscape character.
Consequently, the joint-research project ''Sandküste St. Peter Ording'' examines whether the local flood protection dune “Maleens Knoll”, a 16.6 m high natural coastal dune stretching a roughly 1.2 km long gap in the sea-dike defense, will continue to offer adequate protection in the future. Current hypothesis is, that due to the overgrowth with non-endemic and invasive vegetation species, the natural dynamic and self-adaptation of the system is impaired and will not withstand projected changes in coastal drivers. Therefore, the long-term goal is to develop a variety of nature-friendly flood protection measures to reinforce the dune and reduce its probability of failure during an extreme storm surge.
Possible options comprise the installation of hybrid systems, combining the existing dune core with one of the following structures: 1) a vertical wall to gain more stability during erosion of the sand cover, 2) rock filling to increase wave dissipation and reduce wave reflection and erosion and 3) geotextiles to provide a temporary and more environmentally protection against runup. The built-in materials will be covered with sand, to mimic the original landform and yield its previous degree of freedom regarding topographic adaptation. Another approach is to strengthen the resistance of the sand surface against aeolian and fluvial erosion. Through a microbiological process based on calcium carbonate precipitation (MICP), the strength can be increased in a particularly environmentally friendly way that saves raw materials. Furthermore, adapted or additional planting with a site-typical vegetation can promote sand accumulation at the surface and thereby stabilize the dune.
Large-scale physical model experiments will be performed in a wave flume to investigate the protection potential of the dune. First, the natural dune condition will be recreated and tested under a combination of water levels and wave conditions to investigate current and future load cases. Based on the findings, a second series of experiments will be conducted to determine which engineering methods are most appropriate to reinforce the dune and ensure its coastal protection character and retain its naturalness at the same time.
How to cite: Mehrtens, B., Kosmalla, V., Lojek, O., Schürenkamp, D., and Goseberg, N.: Coastal dunes - A nature based coastal protection element exposed to exacerbated anthropogenic stress, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10779, https://doi.org/10.5194/egusphere-egu21-10779, 2021.
EGU21-15838 | vPICO presentations | GM6.6
Morphosedimentary and ecosystem evolution at Belharucas beach after a sand nourishment (Algarve, south Portugal)Teresa Drago, Sebastião Teixeira, Marcos Rosa, Miriam Tuaty-Guerra, Maria José Gaudêncio, Jorge Lobo-Arteaga, Arthur Veronez, Rui Taborda, and João Cascalho
Beach nourishment is an increasingly recommended solution for reversing the erosion process that affects nowadays the coastal zone. Usually, it is used in emergency situations as a local and short-term solution or as a regional and long-term management strategy.
From April 2017 to November 2019, sediment samples and beach profile data were collected seasonally, before and after a sand nourishment (100.000m3) that increased 30m of width in Belharucas beach (south Portugal, Algarve).
The main objective of the work was to evaluate the nourishment impact in the beach ecosystem, aiming at contributing to seafloor integrity assessment, in the scope of Descriptor 6 of the Marine Strategy Framework Directive.
Methodology included grain size and macrobenthic fauna analyses in two profiles of the nourished area and another one further away, selected as a control area. Each profile was sampled at three intertidal zones: supralittoral (beach berm), mediolittoral (beach face) and infralittoral (low tide terrace). Beach profile data were collected with the main objective of measuring the beach width and evaluate nourishment longevity.
Results show that grain size variability, higher at beach face, is dominated by local energy beach conditions rather than to changes related to the nourishment.
Morphological data shows that beach nourishment had a relatively low longevity as two years after the nourished beach present roughly the same width as priori to nourishment.
While supralittoral samples were defaunated, medio and infralittoral ones exhibited extremely low diversity. Assemblages were dominated by small-size polychaetes, bivalves and isopods. No statistically significant differences were found in assemblage composition regarding pre- and post-sand nourishment, year seasons, tidal zones and control stations.
In conclusion, Belharucas beach exhibited high resilience to the sand nourishment, preserving its morphodynamics and ecosystem conditions.
The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – IDL and through the strategic project UIDB/MAR/04292/2019 - MARE and ECOEXA project (MAR-01.04.02-FEAMP-0016)
How to cite: Drago, T., Teixeira, S., Rosa, M., Tuaty-Guerra, M., Gaudêncio, M. J., Lobo-Arteaga, J., Veronez, A., Taborda, R., and Cascalho, J.: Morphosedimentary and ecosystem evolution at Belharucas beach after a sand nourishment (Algarve, south Portugal), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15838, https://doi.org/10.5194/egusphere-egu21-15838, 2021.
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Beach nourishment is an increasingly recommended solution for reversing the erosion process that affects nowadays the coastal zone. Usually, it is used in emergency situations as a local and short-term solution or as a regional and long-term management strategy.
From April 2017 to November 2019, sediment samples and beach profile data were collected seasonally, before and after a sand nourishment (100.000m3) that increased 30m of width in Belharucas beach (south Portugal, Algarve).
The main objective of the work was to evaluate the nourishment impact in the beach ecosystem, aiming at contributing to seafloor integrity assessment, in the scope of Descriptor 6 of the Marine Strategy Framework Directive.
Methodology included grain size and macrobenthic fauna analyses in two profiles of the nourished area and another one further away, selected as a control area. Each profile was sampled at three intertidal zones: supralittoral (beach berm), mediolittoral (beach face) and infralittoral (low tide terrace). Beach profile data were collected with the main objective of measuring the beach width and evaluate nourishment longevity.
Results show that grain size variability, higher at beach face, is dominated by local energy beach conditions rather than to changes related to the nourishment.
Morphological data shows that beach nourishment had a relatively low longevity as two years after the nourished beach present roughly the same width as priori to nourishment.
While supralittoral samples were defaunated, medio and infralittoral ones exhibited extremely low diversity. Assemblages were dominated by small-size polychaetes, bivalves and isopods. No statistically significant differences were found in assemblage composition regarding pre- and post-sand nourishment, year seasons, tidal zones and control stations.
In conclusion, Belharucas beach exhibited high resilience to the sand nourishment, preserving its morphodynamics and ecosystem conditions.
The authors would like to acknowledge the financial support FCT through project UIDB/50019/2020 – IDL and through the strategic project UIDB/MAR/04292/2019 - MARE and ECOEXA project (MAR-01.04.02-FEAMP-0016)
How to cite: Drago, T., Teixeira, S., Rosa, M., Tuaty-Guerra, M., Gaudêncio, M. J., Lobo-Arteaga, J., Veronez, A., Taborda, R., and Cascalho, J.: Morphosedimentary and ecosystem evolution at Belharucas beach after a sand nourishment (Algarve, south Portugal), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15838, https://doi.org/10.5194/egusphere-egu21-15838, 2021.
EGU21-3021 | vPICO presentations | GM6.6 | Highlight
The effect of repeated sand nourishments on long-term nearshore evolution: a case study for Noordwijk aan Zee, the NetherlandsNienke Vermeer, Gerben Ruessink, and Timothy Price
Sand nourishments are carried out along numerous sandy coasts worldwide to counteract coastal erosion, with the sand added to the inter- and supratidal beach or to the subtidal nearshore profile. Since the early 1990s beach and shoreface nourishments have been carried out along the Dutch coast, with a total nourished volume of 10 to 15 Mm3/year. Although we have a reasonable understanding of how an individual nourishment temporarily affects the evolution of nearshore morphology, it is not clear how repeated nourishments influence the long-term dynamics of the nearshore zone. This understanding is crucial, not only for the safety of beachgoers or marine life, but especially in view of the expected increase in the number of nourishments and total nourishment volume given expected accelerating sea-level rise in the decades to come.
This contribution aims to analyse how repeated nourishments affect the long-term evolution of the shoreline and the two subtidal sandbars at the Dutch beach town Noordwijk aan Zee using Argus video imagery available since 1995. Between 1998 and 2014 four shoreface and three beach nourishments were carried out at the study site. The low-tide time-exposure images of the Argus station were used to determine sandbar and shoreline position along a 6-km stretch of coast.
The results show that prior to the first nourishment the sandbars migrated seaward slowly but persistently. The repeated nourishments permanently decreased this seaward directed migration rate of the sandbars to only a few m/year. The sandbars showed alternating periods of seasonal to multi-year onshore and offshore migration superimposed on this very weak decadal offshore trend. Furthermore, the various sand nourishments gave rise to forked shoreline-sandbar morphology. This large-scale alongshore variability was undone within 1 – 2 years by switches, in which the landward part of a sandbar or the shoreline on one side of the fork realigned with the seaward part of a bar on the other side. These switches appear to be a direct consequence of the repeated nourishments. For example, the 2013-2014 sequence of a beach and a shoreface nourishment resulted in 4 bar switches within the subsequent 2 years, compared to a total of 12 switches in the total dataset of 24.8 years. Further analysis will focus on the effect of repeated nourishments on the temporal and spatial persistence of rip-channel morphology and on the wave conditions that caused the forked morphology to switch.
How to cite: Vermeer, N., Ruessink, G., and Price, T.: The effect of repeated sand nourishments on long-term nearshore evolution: a case study for Noordwijk aan Zee, the Netherlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3021, https://doi.org/10.5194/egusphere-egu21-3021, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Sand nourishments are carried out along numerous sandy coasts worldwide to counteract coastal erosion, with the sand added to the inter- and supratidal beach or to the subtidal nearshore profile. Since the early 1990s beach and shoreface nourishments have been carried out along the Dutch coast, with a total nourished volume of 10 to 15 Mm3/year. Although we have a reasonable understanding of how an individual nourishment temporarily affects the evolution of nearshore morphology, it is not clear how repeated nourishments influence the long-term dynamics of the nearshore zone. This understanding is crucial, not only for the safety of beachgoers or marine life, but especially in view of the expected increase in the number of nourishments and total nourishment volume given expected accelerating sea-level rise in the decades to come.
This contribution aims to analyse how repeated nourishments affect the long-term evolution of the shoreline and the two subtidal sandbars at the Dutch beach town Noordwijk aan Zee using Argus video imagery available since 1995. Between 1998 and 2014 four shoreface and three beach nourishments were carried out at the study site. The low-tide time-exposure images of the Argus station were used to determine sandbar and shoreline position along a 6-km stretch of coast.
The results show that prior to the first nourishment the sandbars migrated seaward slowly but persistently. The repeated nourishments permanently decreased this seaward directed migration rate of the sandbars to only a few m/year. The sandbars showed alternating periods of seasonal to multi-year onshore and offshore migration superimposed on this very weak decadal offshore trend. Furthermore, the various sand nourishments gave rise to forked shoreline-sandbar morphology. This large-scale alongshore variability was undone within 1 – 2 years by switches, in which the landward part of a sandbar or the shoreline on one side of the fork realigned with the seaward part of a bar on the other side. These switches appear to be a direct consequence of the repeated nourishments. For example, the 2013-2014 sequence of a beach and a shoreface nourishment resulted in 4 bar switches within the subsequent 2 years, compared to a total of 12 switches in the total dataset of 24.8 years. Further analysis will focus on the effect of repeated nourishments on the temporal and spatial persistence of rip-channel morphology and on the wave conditions that caused the forked morphology to switch.
How to cite: Vermeer, N., Ruessink, G., and Price, T.: The effect of repeated sand nourishments on long-term nearshore evolution: a case study for Noordwijk aan Zee, the Netherlands, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3021, https://doi.org/10.5194/egusphere-egu21-3021, 2021.
EGU21-10021 | vPICO presentations | GM6.6
Analysis of morphological changes of the island of Hvar beaches using archive maps, old photographs and UAV (Eastern Adriatic Coast, Croatia)Marin Mićunović and Sanja Faivre
Beaches are dynamic coastal forms. However, nowadays, natural processes are intertwined with anthropogenic influences. The island of Hvar has 247 beaches from which we selected those which evolution could be studied by means of repeat photography method using archive maps and old photographs. More than 150 old photographs dating between the 1900s and 1980s have been collected and analyzed. The recent period is studied using unmanned aerial vehicles (UAV).
In total 12 beaches have been selected for precise study. The benchmarks from old photographs were marked and geolocated during the fieldwork using GNSS Trimble receiver. In November 2020, all locations were recorded by quadcopter DJI Phantom 4 Pro v2.0 with approximately 80% overlapping. On each beach, 6 - 12 ground control points (GCP), mostly benchmarks from the old photographs, were marked and measured. Data collected from UAV has been generated by photogrammetric techniques in ESRI Drone2Map software. Orthophoto and digital surface model (DSM) has been processed with a spatial resolution of 0,02 m and 0,1 m for the digital elevation model (DEM). All analyses were made using the ArcGIS Pro software. In this work, the analysis will be presented on two sites: Mina sand beach, formed in Aeolian deposits, on the northern side of the island and Mola Milna gravel beach, found on the southern side. Beaches have been studied in three points in time, in the 19th, 20th and 21st century.
On the Franciscan Cadastre (1834), Mina beach was mapped as an individual cadastral parcel with an area of 222 Klafter Quadrimeter (written in the Cadastral supplement), that is 799 m2. Recalculating in GIS we obtained a similar value, that is, 782 m2. The beach area from the beginning of the 20th century was reconstructed from old photographs and was approximated to 450 m2. Consequently, since 1834 the beach area reduced by ~43%. In 2020, the area further drops to 226 m2, so its surface diminishes by 55% since the beginning of the 20th century or even 72% from 1834.
In 1834 the Mola Milna beach was ~1073 m2, ~900 m2 in the 1950s (16% smaller) and finally 802 m2 in 2020 (11% less than in the 1950s, or 27% smaller compared to 1834).
Thus, we observed that during the last two centuries the sand beach Mina reduced for more than 2/3 of its size since 1834, while the gravel beach Mola Milna reduced for around 1/3. Similar results have been observed previously on the Zogon gravel beach which lost ½ of its size since the 1960s. Even if the reconstructions of the beach area from the Cadaster maps and old photographs are less accurate than the model generated from UAV photos, obtained values clearly reveal the trend of beach erosion during the studied period.
This research was made with the support of the Croatian Science Foundation (HRZZ-IP-2019-04-9445).
How to cite: Mićunović, M. and Faivre, S.: Analysis of morphological changes of the island of Hvar beaches using archive maps, old photographs and UAV (Eastern Adriatic Coast, Croatia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10021, https://doi.org/10.5194/egusphere-egu21-10021, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Beaches are dynamic coastal forms. However, nowadays, natural processes are intertwined with anthropogenic influences. The island of Hvar has 247 beaches from which we selected those which evolution could be studied by means of repeat photography method using archive maps and old photographs. More than 150 old photographs dating between the 1900s and 1980s have been collected and analyzed. The recent period is studied using unmanned aerial vehicles (UAV).
In total 12 beaches have been selected for precise study. The benchmarks from old photographs were marked and geolocated during the fieldwork using GNSS Trimble receiver. In November 2020, all locations were recorded by quadcopter DJI Phantom 4 Pro v2.0 with approximately 80% overlapping. On each beach, 6 - 12 ground control points (GCP), mostly benchmarks from the old photographs, were marked and measured. Data collected from UAV has been generated by photogrammetric techniques in ESRI Drone2Map software. Orthophoto and digital surface model (DSM) has been processed with a spatial resolution of 0,02 m and 0,1 m for the digital elevation model (DEM). All analyses were made using the ArcGIS Pro software. In this work, the analysis will be presented on two sites: Mina sand beach, formed in Aeolian deposits, on the northern side of the island and Mola Milna gravel beach, found on the southern side. Beaches have been studied in three points in time, in the 19th, 20th and 21st century.
On the Franciscan Cadastre (1834), Mina beach was mapped as an individual cadastral parcel with an area of 222 Klafter Quadrimeter (written in the Cadastral supplement), that is 799 m2. Recalculating in GIS we obtained a similar value, that is, 782 m2. The beach area from the beginning of the 20th century was reconstructed from old photographs and was approximated to 450 m2. Consequently, since 1834 the beach area reduced by ~43%. In 2020, the area further drops to 226 m2, so its surface diminishes by 55% since the beginning of the 20th century or even 72% from 1834.
In 1834 the Mola Milna beach was ~1073 m2, ~900 m2 in the 1950s (16% smaller) and finally 802 m2 in 2020 (11% less than in the 1950s, or 27% smaller compared to 1834).
Thus, we observed that during the last two centuries the sand beach Mina reduced for more than 2/3 of its size since 1834, while the gravel beach Mola Milna reduced for around 1/3. Similar results have been observed previously on the Zogon gravel beach which lost ½ of its size since the 1960s. Even if the reconstructions of the beach area from the Cadaster maps and old photographs are less accurate than the model generated from UAV photos, obtained values clearly reveal the trend of beach erosion during the studied period.
This research was made with the support of the Croatian Science Foundation (HRZZ-IP-2019-04-9445).
How to cite: Mićunović, M. and Faivre, S.: Analysis of morphological changes of the island of Hvar beaches using archive maps, old photographs and UAV (Eastern Adriatic Coast, Croatia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10021, https://doi.org/10.5194/egusphere-egu21-10021, 2021.
EGU21-13031 | vPICO presentations | GM6.6
Satellite-derived shorelines reveal fascinating dynamics for the last three decades on Danube Delta coastFlorin Tatui, Georgiana Anghelin, and Sorin Constantin
Shoreline, as the interface between the upper shoreface and the beach-dune system, is sensitive to all changes from both the underwater and sub-aerial parts of the beach at a wide range of temporal scales (seconds to decades), making it a good indicator for coastal health. While more traditional techniques of shoreline monitoring present some shortcomings (low temporal resolution for photointerpretation, reduced spatial extension for video-based techniques, high costs for DGPS in-situ data acquisition), freely available satellite images can provide information for large areas (tens/hundreds of km) at very good temporal scales (days).
We employed a shoreline detection workflow for the dynamic environment of the Danube Delta coast (Black Sea). We focused on an index-based approach using the Automated Water Extraction Index (AWEI). A fully automated procedure was deployed for data processing and the waterline was estimated at sub-pixel level with an adapted image thresholding technique. For validation purposes, 5 Sentinel-2 and 5 Landsat based results were compared with both in-situ (D)GPS measurements and manually digitized shoreline positions from very high-resolution satellite images (Pleiades – 0.5 m and Spot 7 – 1.5 m). The overall accuracy of the methodology, expressed as mean absolute error, was found to be of approximately 7.5 m for Sentinel-2 and 4.7 m for Landsat data, respectively.
More than 200 Landsat (5 and 8) and Sentinel-2 images were processed and the corresponding satellite-derived shorelines between 1990 and 2020 were analysed for the whole Romanian Danube Delta coast (130 km). This high number of shorelines allowed us the discrimination of different patterns of coastline dynamic and behaviour which could not have been possible using usual surveying techniques: the extent of accumulation areas induced by the 2005-2006 historical river floods, the impact of different high-energy storms and the subsequent beach recovery after these events, the alongshore movement of erosional processes in accordance with the dominant direction of longshore sediment transport, multi-annual differences in both erosional and accumulation trends. Moreover, a very important result of our analysis is the zonation of Danube Delta coast based on multi-annual trends of shoreline dynamics at finer alongshore spatial resolution than before. This has significant implications for future studies dealing with different scenarios of Danube Delta response to projected sea level rise and increased storminess.
The presented approach and resulting products offer optimal combination of data availability, accuracy and frequency necessary to meet the monitoring and management needs of the increasing number of stakeholders involved in the coastal zone protection activities.
How to cite: Tatui, F., Anghelin, G., and Constantin, S.: Satellite-derived shorelines reveal fascinating dynamics for the last three decades on Danube Delta coast, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13031, https://doi.org/10.5194/egusphere-egu21-13031, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Shoreline, as the interface between the upper shoreface and the beach-dune system, is sensitive to all changes from both the underwater and sub-aerial parts of the beach at a wide range of temporal scales (seconds to decades), making it a good indicator for coastal health. While more traditional techniques of shoreline monitoring present some shortcomings (low temporal resolution for photointerpretation, reduced spatial extension for video-based techniques, high costs for DGPS in-situ data acquisition), freely available satellite images can provide information for large areas (tens/hundreds of km) at very good temporal scales (days).
We employed a shoreline detection workflow for the dynamic environment of the Danube Delta coast (Black Sea). We focused on an index-based approach using the Automated Water Extraction Index (AWEI). A fully automated procedure was deployed for data processing and the waterline was estimated at sub-pixel level with an adapted image thresholding technique. For validation purposes, 5 Sentinel-2 and 5 Landsat based results were compared with both in-situ (D)GPS measurements and manually digitized shoreline positions from very high-resolution satellite images (Pleiades – 0.5 m and Spot 7 – 1.5 m). The overall accuracy of the methodology, expressed as mean absolute error, was found to be of approximately 7.5 m for Sentinel-2 and 4.7 m for Landsat data, respectively.
More than 200 Landsat (5 and 8) and Sentinel-2 images were processed and the corresponding satellite-derived shorelines between 1990 and 2020 were analysed for the whole Romanian Danube Delta coast (130 km). This high number of shorelines allowed us the discrimination of different patterns of coastline dynamic and behaviour which could not have been possible using usual surveying techniques: the extent of accumulation areas induced by the 2005-2006 historical river floods, the impact of different high-energy storms and the subsequent beach recovery after these events, the alongshore movement of erosional processes in accordance with the dominant direction of longshore sediment transport, multi-annual differences in both erosional and accumulation trends. Moreover, a very important result of our analysis is the zonation of Danube Delta coast based on multi-annual trends of shoreline dynamics at finer alongshore spatial resolution than before. This has significant implications for future studies dealing with different scenarios of Danube Delta response to projected sea level rise and increased storminess.
The presented approach and resulting products offer optimal combination of data availability, accuracy and frequency necessary to meet the monitoring and management needs of the increasing number of stakeholders involved in the coastal zone protection activities.
How to cite: Tatui, F., Anghelin, G., and Constantin, S.: Satellite-derived shorelines reveal fascinating dynamics for the last three decades on Danube Delta coast, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13031, https://doi.org/10.5194/egusphere-egu21-13031, 2021.
EGU21-8266 | vPICO presentations | GM6.6 | Highlight
Detecting coastal change around the North Sea from open-source satellite imagesFreya Fenwick, Timothy Price, and Gerben Ruessink
Wave-dominated sandy coastlines worldwide are susceptible to change under the expected climate-change induced developments in sea level rise, mean wave conditions and storm events. For coastal management it remains important to observe and quantify these coastal changes, especially in low-lying developed coastal areas susceptible to flooding. The beaches surrounding an ocean basin have a variety of orientations, tidal ranges and management strategies, to name a few, which will lead to a range of morphological responses to future changes in hydrodynamic conditions within the basin. In addition, the conditions under which these varied responses mainly occur (e.g., under regular conditions or only during storm conditions) is not clear. Here, we used satellite imagery to compare the morphological response of a selection of beaches surrounding the North Sea.
The position of the shoreline is generally considered as a key variable to monitor the morphological evolution of sandy coasts. This research used the open-source software toolkit CoastSat (Vos et al., 2019) to automatically map shorelines from publicly available satellite imagery from 1984 to present, which are retrieved via Google Earth Engine (Gorelick et al., 2017). We selected five long, sandy beaches around the North Sea with varying tidal ranges, orientations and wave exposure for our analysis: (1) Skallingen in Denmark, (2) Egmond aan Zee and (3) the barrier island of Schiermonnikoog, both in the Netherlands, (4) Groenendijk in Belgium, and (5), Theddlethorpe in the UK. Approximately 2000 images per site were used for the shoreline extraction. Offshore wave buoy measurements and numerical model output provided the tidal water levels and wave conditions for the different sites. To account for tidal correction of the shoreline to a reference elevation, we used the dataset of Athanasiou et al. (2019) to estimate characteristic beach face slopes. At the conference we will present our analysis of the shoreline responses around the North Sea over the last few decades.
Athanasiou, P., Van Dongeren, A., Giardino, A., Vousdoukas, M., Gaytan-Aguilar, S., & Ranasinghe, R. (2019). Global distribution of nearshore slopes with implications for coastal retreat. Earth system science data, 11(4).
Gorelick, N., Hancher, M., Dixon, M., Ilyushchenko, S., Thau, D., & Moore, R. (2017). Google Earth Engine: Planetary-scale geospatial analysis for everyone. Remote sensing of Environment, 202, 18-27.
Vos, K., Splinter, K. D., Harley, M. D., Simmons, J. A., & Turner, I. L. (2019). CoastSat: A Google Earth Engine-enabled Python toolkit to extract shorelines from publicly available satellite imagery. Environmental Modelling & Software, 122, 104528.
How to cite: Fenwick, F., Price, T., and Ruessink, G.: Detecting coastal change around the North Sea from open-source satellite images, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8266, https://doi.org/10.5194/egusphere-egu21-8266, 2021.
Wave-dominated sandy coastlines worldwide are susceptible to change under the expected climate-change induced developments in sea level rise, mean wave conditions and storm events. For coastal management it remains important to observe and quantify these coastal changes, especially in low-lying developed coastal areas susceptible to flooding. The beaches surrounding an ocean basin have a variety of orientations, tidal ranges and management strategies, to name a few, which will lead to a range of morphological responses to future changes in hydrodynamic conditions within the basin. In addition, the conditions under which these varied responses mainly occur (e.g., under regular conditions or only during storm conditions) is not clear. Here, we used satellite imagery to compare the morphological response of a selection of beaches surrounding the North Sea.
The position of the shoreline is generally considered as a key variable to monitor the morphological evolution of sandy coasts. This research used the open-source software toolkit CoastSat (Vos et al., 2019) to automatically map shorelines from publicly available satellite imagery from 1984 to present, which are retrieved via Google Earth Engine (Gorelick et al., 2017). We selected five long, sandy beaches around the North Sea with varying tidal ranges, orientations and wave exposure for our analysis: (1) Skallingen in Denmark, (2) Egmond aan Zee and (3) the barrier island of Schiermonnikoog, both in the Netherlands, (4) Groenendijk in Belgium, and (5), Theddlethorpe in the UK. Approximately 2000 images per site were used for the shoreline extraction. Offshore wave buoy measurements and numerical model output provided the tidal water levels and wave conditions for the different sites. To account for tidal correction of the shoreline to a reference elevation, we used the dataset of Athanasiou et al. (2019) to estimate characteristic beach face slopes. At the conference we will present our analysis of the shoreline responses around the North Sea over the last few decades.
Athanasiou, P., Van Dongeren, A., Giardino, A., Vousdoukas, M., Gaytan-Aguilar, S., & Ranasinghe, R. (2019). Global distribution of nearshore slopes with implications for coastal retreat. Earth system science data, 11(4).
Gorelick, N., Hancher, M., Dixon, M., Ilyushchenko, S., Thau, D., & Moore, R. (2017). Google Earth Engine: Planetary-scale geospatial analysis for everyone. Remote sensing of Environment, 202, 18-27.
Vos, K., Splinter, K. D., Harley, M. D., Simmons, J. A., & Turner, I. L. (2019). CoastSat: A Google Earth Engine-enabled Python toolkit to extract shorelines from publicly available satellite imagery. Environmental Modelling & Software, 122, 104528.
How to cite: Fenwick, F., Price, T., and Ruessink, G.: Detecting coastal change around the North Sea from open-source satellite images, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8266, https://doi.org/10.5194/egusphere-egu21-8266, 2021.
EGU21-11099 | vPICO presentations | GM6.6
Trends in shoreline variability driven by anthropogenic change, EThekwini Municipality, South AfricaErrol Wiles, Rio Leuci, Zane Thakeray, and Godfrey Vella
It is well-known that the coastal zone attracts human populations like no other. There is ever increasing demand on the coastal zone by tourists, residents and developers alike; it is named as the fastest growing sector of the blue economy. Hence, coastal zone processes require better understanding to be effectively managed in the context of sustainable development of the asset. While sea level may be rising over the long-term, and many global-resolution studies lament the loss of sandy beaches as a result, coastal managers work over far shorter time-scales thus require site specific information to manage the coastal zone on a daily and monthly basis. In this contribution we discuss nine years of morphological change along a sandy beach in Durban, South Africa. The beach is managed by the eThekwini Municipality who are responsible for maintaining a coastal zone of ca. 100 km. The morphological data of this study were collected on a near monthly basis over 9.6 km of sandy beach between October 2011 and March 2020. From these data, beach volume and area are calculated and the variation is documented over time in conjunction with wave data recorded from a proximal directional wave buoy. Over the study period, the beach has experienced a net loss of 177 885m3 and 29 375 m2 in volume and area respectively. However, the beach response has not been uniform throughout the study area. The southern three-quarters of the beach were affected by significant losses while the northern one-quarter gained in volume and area over the same period. The summer wave climate is characterised by increased variability in swell origin with greater easterly contributions than other seasons, and typically lacks the frequency of large swell (>3.5 m) events (7% of events) common to autumn (20%), winter (35%) and spring (38%). Winter, followed by spring then autumn seasons have more focused swell origins and southerly contribution, particularly in terms of large swell events. During periods of reduced event frequency allow for partial beach recovery, while erosion is associated with periods of increase event frequency. The sediment budget has been significantly reduced though impoundments on the proximal river catchment, compounded by un-managed sand mining. Rather than sea level, these near-field controls on sediment availability likely play a major role in beach volume and area in response to wave climate. There is less sediment available to nourish the beach naturally following erosional events; artificial nourishment will likely be required to maintain the sandy beach in the future.
How to cite: Wiles, E., Leuci, R., Thakeray, Z., and Vella, G.: Trends in shoreline variability driven by anthropogenic change, EThekwini Municipality, South Africa, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11099, https://doi.org/10.5194/egusphere-egu21-11099, 2021.
It is well-known that the coastal zone attracts human populations like no other. There is ever increasing demand on the coastal zone by tourists, residents and developers alike; it is named as the fastest growing sector of the blue economy. Hence, coastal zone processes require better understanding to be effectively managed in the context of sustainable development of the asset. While sea level may be rising over the long-term, and many global-resolution studies lament the loss of sandy beaches as a result, coastal managers work over far shorter time-scales thus require site specific information to manage the coastal zone on a daily and monthly basis. In this contribution we discuss nine years of morphological change along a sandy beach in Durban, South Africa. The beach is managed by the eThekwini Municipality who are responsible for maintaining a coastal zone of ca. 100 km. The morphological data of this study were collected on a near monthly basis over 9.6 km of sandy beach between October 2011 and March 2020. From these data, beach volume and area are calculated and the variation is documented over time in conjunction with wave data recorded from a proximal directional wave buoy. Over the study period, the beach has experienced a net loss of 177 885m3 and 29 375 m2 in volume and area respectively. However, the beach response has not been uniform throughout the study area. The southern three-quarters of the beach were affected by significant losses while the northern one-quarter gained in volume and area over the same period. The summer wave climate is characterised by increased variability in swell origin with greater easterly contributions than other seasons, and typically lacks the frequency of large swell (>3.5 m) events (7% of events) common to autumn (20%), winter (35%) and spring (38%). Winter, followed by spring then autumn seasons have more focused swell origins and southerly contribution, particularly in terms of large swell events. During periods of reduced event frequency allow for partial beach recovery, while erosion is associated with periods of increase event frequency. The sediment budget has been significantly reduced though impoundments on the proximal river catchment, compounded by un-managed sand mining. Rather than sea level, these near-field controls on sediment availability likely play a major role in beach volume and area in response to wave climate. There is less sediment available to nourish the beach naturally following erosional events; artificial nourishment will likely be required to maintain the sandy beach in the future.
How to cite: Wiles, E., Leuci, R., Thakeray, Z., and Vella, G.: Trends in shoreline variability driven by anthropogenic change, EThekwini Municipality, South Africa, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11099, https://doi.org/10.5194/egusphere-egu21-11099, 2021.
EGU21-15400 | vPICO presentations | GM6.6
Use of Sentinel-2A/B satellites and Google Earth Engine for monitoring estuarine systems: a study case in the Western MediterraneanMar Roca Mora, Gabriel Navarro Almendros, Javier García Sanabria, and Isabel Caballero de Frutos
Coastal areas are being rapidly transformed in the last 50 years due to anthropogenic causes. New infrastructures and intensive activities have changed the natural behaviour of coastal ecosystems, promoting problems related to water quality, eutrophication and coastal erosion. This situation increases the vulnerability to climate change, requiring important efforts in monitoring and defining protocols for optimizing operational decision-making and strategic management. Remote sensing techniques are becoming a key tool for coastal mapping in terms of resolution, effectiveness and cost reduction. In the last decade, the European Commission launched the Copernicus programme for Earth Observation as a way of improving coastal monitoring with higher resolution. Sentinel-2A/B twin satellites are part of this free and open policy programme available since 2015, but atmospheric corrections or cloud cover are still challenges to face. In order to process this data, cloud computing platforms such as Google Earth Engine (GEE) have revolutionized the way satellite images are processed, without the need to download and store local data. The present study aimed at developing a GEE-based technique for selecting cloud-free Sentinel-2 Level-2A images in the Guadiaro estuary in the Western Mediterranean (Spain) during the last four years (2017-2020). It has been used to analyse the evolution of the sand bar and to identify hotspots in its sedimentary variation along the coast, at 10 m and 5 days spatial and temporal resolution respectively. NDWI index was evaluated using 0.05 to 0.15 threshold, revealing 0.1 as the best threshold to be used for land/water mapping, easily incorporated in the GEE platform. In addition to Sentinel-2 potential, this study also demonstrates the power of GEE, computing more than 400 images for statistical analysis in terms of seconds, which enabled the automatic filtering method developed for cloud-free images selection with a 95% of effectiveness. Moreover, ACOLITE processor has been used on Sentinel-2 L1A images for atmospheric and sunglint correction to generate Level-2 data and for analysing turbidity and water quality patterns during extreme rainfall events, providing key information as early-warning indicators development. This improvement will be useful for near future implementation of remote sensing applications for coastal managers, ensuring a continuous and detailed monitoring and helping to support an ecosystem-based approach for coastal areas.
How to cite: Roca Mora, M., Navarro Almendros, G., García Sanabria, J., and Caballero de Frutos, I.: Use of Sentinel-2A/B satellites and Google Earth Engine for monitoring estuarine systems: a study case in the Western Mediterranean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15400, https://doi.org/10.5194/egusphere-egu21-15400, 2021.
Coastal areas are being rapidly transformed in the last 50 years due to anthropogenic causes. New infrastructures and intensive activities have changed the natural behaviour of coastal ecosystems, promoting problems related to water quality, eutrophication and coastal erosion. This situation increases the vulnerability to climate change, requiring important efforts in monitoring and defining protocols for optimizing operational decision-making and strategic management. Remote sensing techniques are becoming a key tool for coastal mapping in terms of resolution, effectiveness and cost reduction. In the last decade, the European Commission launched the Copernicus programme for Earth Observation as a way of improving coastal monitoring with higher resolution. Sentinel-2A/B twin satellites are part of this free and open policy programme available since 2015, but atmospheric corrections or cloud cover are still challenges to face. In order to process this data, cloud computing platforms such as Google Earth Engine (GEE) have revolutionized the way satellite images are processed, without the need to download and store local data. The present study aimed at developing a GEE-based technique for selecting cloud-free Sentinel-2 Level-2A images in the Guadiaro estuary in the Western Mediterranean (Spain) during the last four years (2017-2020). It has been used to analyse the evolution of the sand bar and to identify hotspots in its sedimentary variation along the coast, at 10 m and 5 days spatial and temporal resolution respectively. NDWI index was evaluated using 0.05 to 0.15 threshold, revealing 0.1 as the best threshold to be used for land/water mapping, easily incorporated in the GEE platform. In addition to Sentinel-2 potential, this study also demonstrates the power of GEE, computing more than 400 images for statistical analysis in terms of seconds, which enabled the automatic filtering method developed for cloud-free images selection with a 95% of effectiveness. Moreover, ACOLITE processor has been used on Sentinel-2 L1A images for atmospheric and sunglint correction to generate Level-2 data and for analysing turbidity and water quality patterns during extreme rainfall events, providing key information as early-warning indicators development. This improvement will be useful for near future implementation of remote sensing applications for coastal managers, ensuring a continuous and detailed monitoring and helping to support an ecosystem-based approach for coastal areas.
How to cite: Roca Mora, M., Navarro Almendros, G., García Sanabria, J., and Caballero de Frutos, I.: Use of Sentinel-2A/B satellites and Google Earth Engine for monitoring estuarine systems: a study case in the Western Mediterranean, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15400, https://doi.org/10.5194/egusphere-egu21-15400, 2021.
EGU21-15404 | vPICO presentations | GM6.6
Geomophological and vulnerability analysis of a coastal delta under increased hydrological alteration over the past two centuries: Tana River delta, Kenya, East Africa.Peter Gitau, Stéphanie Duvail, Dirk Verschuren, and Dominique Guillaud
Coastal deltas worldwide are under risk of degradation due to the increasing impacts of sea-level rise, and continuous human alterations of river basin hydrology. This research highlights the geomorphological changes that have occurred within the Tana River delta in Kenya, an important deltaic ecosystem of high biodiversity value in East Africa.
The geomorphological features (river channels, floodplain, coastal dune system) and their evolution over the past two centuries were described. Aerial and satellite imagery was used to assess the magnitude and distribution of coastal changes from the 1960s to present. Additionally, sediment cores recovered within the mangrove environment were analysed to establish the succession of sedimentation periods and patterns. Finally, we explored the response of the coastal processes of deposition and erosion under anthropogenic alterations of the hydrological system.
It was established that over the past two centuries Tana River has changed its main channel and outlet to the Indian Ocean on three occasions. A first river avulsion occurred in the 1860s, followed by a second avulsion in the late 1890s that was promoted by human interference through channel expansion and dyke construction. The third change in river course has occurred gradually over the past 20 years, amid human efforts to engineer the river channels.
From the sediment analysis and radiocarbon dating, it is ascertained that the lower deltaic region developed rapidly over the past ~180 years, facilitated by increased sedimentation from the main Tana River. On the other hand, analysis of the coastline changes indicate that there has been increased erosion of the coastal dune system and mangrove vegetation along the former river outlet, leading to rapid marine intrusion into local subsistence farming areas. By analysing the combined impacts of both natural river dynamics and human alteration we highlight how the integrity of the Tana River delta has increasingly become vulnerable under present sea level rise and continued upstream river alteration.
How to cite: Gitau, P., Duvail, S., Verschuren, D., and Guillaud, D.: Geomophological and vulnerability analysis of a coastal delta under increased hydrological alteration over the past two centuries: Tana River delta, Kenya, East Africa., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15404, https://doi.org/10.5194/egusphere-egu21-15404, 2021.
Coastal deltas worldwide are under risk of degradation due to the increasing impacts of sea-level rise, and continuous human alterations of river basin hydrology. This research highlights the geomorphological changes that have occurred within the Tana River delta in Kenya, an important deltaic ecosystem of high biodiversity value in East Africa.
The geomorphological features (river channels, floodplain, coastal dune system) and their evolution over the past two centuries were described. Aerial and satellite imagery was used to assess the magnitude and distribution of coastal changes from the 1960s to present. Additionally, sediment cores recovered within the mangrove environment were analysed to establish the succession of sedimentation periods and patterns. Finally, we explored the response of the coastal processes of deposition and erosion under anthropogenic alterations of the hydrological system.
It was established that over the past two centuries Tana River has changed its main channel and outlet to the Indian Ocean on three occasions. A first river avulsion occurred in the 1860s, followed by a second avulsion in the late 1890s that was promoted by human interference through channel expansion and dyke construction. The third change in river course has occurred gradually over the past 20 years, amid human efforts to engineer the river channels.
From the sediment analysis and radiocarbon dating, it is ascertained that the lower deltaic region developed rapidly over the past ~180 years, facilitated by increased sedimentation from the main Tana River. On the other hand, analysis of the coastline changes indicate that there has been increased erosion of the coastal dune system and mangrove vegetation along the former river outlet, leading to rapid marine intrusion into local subsistence farming areas. By analysing the combined impacts of both natural river dynamics and human alteration we highlight how the integrity of the Tana River delta has increasingly become vulnerable under present sea level rise and continued upstream river alteration.
How to cite: Gitau, P., Duvail, S., Verschuren, D., and Guillaud, D.: Geomophological and vulnerability analysis of a coastal delta under increased hydrological alteration over the past two centuries: Tana River delta, Kenya, East Africa., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15404, https://doi.org/10.5194/egusphere-egu21-15404, 2021.
EGU21-8965 | vPICO presentations | GM6.6 | Highlight
National geological and hazardous systematic cartography of the coastal zone as a contribution to the promotion of sustainability, defence and valorisation of the Portuguese coastal areaSílvia Nave and Luís Rebêlo
The Portuguese coastal zone, where ¾ of the population lives and where the contribution to GNP is estimated at 85%, assumes an important role in the national economic context, which is not only presently reflected on the budget dedicated to the management and mitigation of current risks associated to climate change, but also for its strategic importance in environmental, social and leisure industry perspectives.
The geological and hazardous cartography of the coastal zone, of mainland Portugal, on a 1:3000 scale, has been developed, at LNEG, as an instrument to support the sustainability, protection and enhancement of the coastline [2018, JCC, 22:1031-1043].
The increase in knowledge concerning coastal hazard, based on the historical evolution of the shoreline, expressed on a systematic and digital cartographic basis at a scale of detail, in addition to the important contribution to the development of regional geology, is a vital contribution for the correct use and sustainable development of the coast. So far, shoreline evolution evaluation has been determined for two coastal sectors covering approximately 140 km of coastline: the western sector of Figueira da Foz to Nazaré and the southern sector of Algarve between Faro and Vila Real de Santo António [2021, JCC, https://doi.org/10.1007/s11852-020-00791-3].
The western sector evolutionary trend, from 1947 to 2015, shows an overall erosional behaviour, even though a prograding tendency is observed in some areas. Coastline evolution assessment reveals an average retreat of -13.6 m and a 702,558 m2 land loss area. However, when looking only for the sectors where erosion occurred, a total of 1,164,888 m2 of land loss was observed. Erosion, that is more severe in the northern part, reaching a maximum coastal retreat of -145 m and an erosion rate of 2.46 my-1, seems to be induced by a reduction of the littoral drift, but also by human interference in coastal dynamics, namely by the introduction and enlargement of the original rigid constructions and groins installation.
Regarding the south eastern Algarve coastline displacement, from 1950 to 2015, a seaward shift prevails, with a prograding coastline occupying approximately 54% of the studied sector. However, this progradation is mostly associated to human intervention on the coast, being related to up-drift accumulation against inlet jetties / groins. The erosional trend prevails predominantly in the central barrier island system of Ria Formosa, namely in the Culatra (with a maximum displacement of -163 m), Armona (maximum displacement of -83 m), the Tavira, (maximum displacement of -116 m), and the Cabanas islands, where maximum displacement observed is up to -235 m. Regarding land area changes, some sectors lost and others gained area due to coastline displacement. However, the overall analysis showed an area increase of 1.05 × 106 m2 for this south-eastern coastal fringe.
The achievement of high-resolution, continuous and updated data, at a regional scale, likely favour successful application of the needed mitigation measures (as beach/dune nourishment, sand-shots and others) at the exact key target locations.
How to cite: Nave, S. and Rebêlo, L.: National geological and hazardous systematic cartography of the coastal zone as a contribution to the promotion of sustainability, defence and valorisation of the Portuguese coastal area, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8965, https://doi.org/10.5194/egusphere-egu21-8965, 2021.
The Portuguese coastal zone, where ¾ of the population lives and where the contribution to GNP is estimated at 85%, assumes an important role in the national economic context, which is not only presently reflected on the budget dedicated to the management and mitigation of current risks associated to climate change, but also for its strategic importance in environmental, social and leisure industry perspectives.
The geological and hazardous cartography of the coastal zone, of mainland Portugal, on a 1:3000 scale, has been developed, at LNEG, as an instrument to support the sustainability, protection and enhancement of the coastline [2018, JCC, 22:1031-1043].
The increase in knowledge concerning coastal hazard, based on the historical evolution of the shoreline, expressed on a systematic and digital cartographic basis at a scale of detail, in addition to the important contribution to the development of regional geology, is a vital contribution for the correct use and sustainable development of the coast. So far, shoreline evolution evaluation has been determined for two coastal sectors covering approximately 140 km of coastline: the western sector of Figueira da Foz to Nazaré and the southern sector of Algarve between Faro and Vila Real de Santo António [2021, JCC, https://doi.org/10.1007/s11852-020-00791-3].
The western sector evolutionary trend, from 1947 to 2015, shows an overall erosional behaviour, even though a prograding tendency is observed in some areas. Coastline evolution assessment reveals an average retreat of -13.6 m and a 702,558 m2 land loss area. However, when looking only for the sectors where erosion occurred, a total of 1,164,888 m2 of land loss was observed. Erosion, that is more severe in the northern part, reaching a maximum coastal retreat of -145 m and an erosion rate of 2.46 my-1, seems to be induced by a reduction of the littoral drift, but also by human interference in coastal dynamics, namely by the introduction and enlargement of the original rigid constructions and groins installation.
Regarding the south eastern Algarve coastline displacement, from 1950 to 2015, a seaward shift prevails, with a prograding coastline occupying approximately 54% of the studied sector. However, this progradation is mostly associated to human intervention on the coast, being related to up-drift accumulation against inlet jetties / groins. The erosional trend prevails predominantly in the central barrier island system of Ria Formosa, namely in the Culatra (with a maximum displacement of -163 m), Armona (maximum displacement of -83 m), the Tavira, (maximum displacement of -116 m), and the Cabanas islands, where maximum displacement observed is up to -235 m. Regarding land area changes, some sectors lost and others gained area due to coastline displacement. However, the overall analysis showed an area increase of 1.05 × 106 m2 for this south-eastern coastal fringe.
The achievement of high-resolution, continuous and updated data, at a regional scale, likely favour successful application of the needed mitigation measures (as beach/dune nourishment, sand-shots and others) at the exact key target locations.
How to cite: Nave, S. and Rebêlo, L.: National geological and hazardous systematic cartography of the coastal zone as a contribution to the promotion of sustainability, defence and valorisation of the Portuguese coastal area, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8965, https://doi.org/10.5194/egusphere-egu21-8965, 2021.
EGU21-8770 | vPICO presentations | GM6.6
Moisture distribution, tensile strength, evaporation rate and origin of coastal honeycombs (Tuscan, Italy)Jakub Mares and Jiri Bruthans
Cavernous weathering is a typical example of the degradation pattern of both natural outcrops and cultural heritage. It is described from all environments on Earth and also on Mars. The most common examples are honeycombs and tafoni. Honeycombs are known from arid, humid, and cold deserts, but best developed honeycombs are often described from coastal areas. There are many ideas on the origin of cavernous weathering (case hardening, chemical alteration), but currently most authors believe that the origin is caused by salt weathering. Huinink et al. (2004) described a theory that inside the pits, the capillary zone is closer to the surface and therefore the intensity of the evaporation is higher than in walls separation the pits. As more evaporation accumulates more salts the pits enlarges faster than surface outsides the pits is retreating. To verify this theory, in the environment of coastal honeycombs in Tuscan (Italy), the depth of the vaporization plane (interface between dry surface zone and deeper capillary zone) was measured by the "uranine-probe" method (Weiss et al., 2020) inside and outside the ten honeycombs. From the depth of the vaporization plane and climatic conditions on the study site, the intensity of evaporation was calculated and from the mineralization of water the amount of precipitated salts was estimated. To determine the effect of case hardening, the tensile strength of honeycomb pits and walls was measured. The vaporization plane measurements show that for all honeycombs, the vaporization plane was closer to the surface in pits than outside. The evaporation intensity was calculated for the mean depth of vaporization plane inside the honeycombs (2 mm) and the mean depth outside the honeycombs (7 mm). In marine environment a solution on a vaporization plane should be saturated with halite which has an equilibrium relative humidity of 75 %. The evaporation intensity inside the honeycombs is 9.4 mm/year for 75 % RH and 2.7 mm/year outside the honeycombs. Considering that the evaporated water is of the same composition as seawater, 0.1-0.4 g salts precipitate from 1 m2, most of which is NaCl. Inside the honeycombs precipitate 3 times more salts than outside. The tensile strength inside the honeycombs is approximately the same as outside considering standard deviation (354±339 and 284±157 kPa, respectively), so case hardening does not have any effect. The results correspond to the theory of origin according to Huinink et al. (2004). For a detailed description of the moisture behavior in future studies, it is necessary to better understand the moisture conditions (especially relative humidity on the vaporization plane) and it is vital to perform repeated measurements during various seasons.
References:
Huinink HP, Pel L, Kopinga K., 2004. Simulating the growth of tafoni. Earth Surface Processes and Landforms 29: 1225–1233.
Weiss T, Mareš J, Slavík M, Bruthans J. 2020. A microdestructive method using dye-coated-probe to visualize capillary, diffusion and evaporation zones in porous materials. Science of The Total Environment 704, 135339.
How to cite: Mares, J. and Bruthans, J.: Moisture distribution, tensile strength, evaporation rate and origin of coastal honeycombs (Tuscan, Italy) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8770, https://doi.org/10.5194/egusphere-egu21-8770, 2021.
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Cavernous weathering is a typical example of the degradation pattern of both natural outcrops and cultural heritage. It is described from all environments on Earth and also on Mars. The most common examples are honeycombs and tafoni. Honeycombs are known from arid, humid, and cold deserts, but best developed honeycombs are often described from coastal areas. There are many ideas on the origin of cavernous weathering (case hardening, chemical alteration), but currently most authors believe that the origin is caused by salt weathering. Huinink et al. (2004) described a theory that inside the pits, the capillary zone is closer to the surface and therefore the intensity of the evaporation is higher than in walls separation the pits. As more evaporation accumulates more salts the pits enlarges faster than surface outsides the pits is retreating. To verify this theory, in the environment of coastal honeycombs in Tuscan (Italy), the depth of the vaporization plane (interface between dry surface zone and deeper capillary zone) was measured by the "uranine-probe" method (Weiss et al., 2020) inside and outside the ten honeycombs. From the depth of the vaporization plane and climatic conditions on the study site, the intensity of evaporation was calculated and from the mineralization of water the amount of precipitated salts was estimated. To determine the effect of case hardening, the tensile strength of honeycomb pits and walls was measured. The vaporization plane measurements show that for all honeycombs, the vaporization plane was closer to the surface in pits than outside. The evaporation intensity was calculated for the mean depth of vaporization plane inside the honeycombs (2 mm) and the mean depth outside the honeycombs (7 mm). In marine environment a solution on a vaporization plane should be saturated with halite which has an equilibrium relative humidity of 75 %. The evaporation intensity inside the honeycombs is 9.4 mm/year for 75 % RH and 2.7 mm/year outside the honeycombs. Considering that the evaporated water is of the same composition as seawater, 0.1-0.4 g salts precipitate from 1 m2, most of which is NaCl. Inside the honeycombs precipitate 3 times more salts than outside. The tensile strength inside the honeycombs is approximately the same as outside considering standard deviation (354±339 and 284±157 kPa, respectively), so case hardening does not have any effect. The results correspond to the theory of origin according to Huinink et al. (2004). For a detailed description of the moisture behavior in future studies, it is necessary to better understand the moisture conditions (especially relative humidity on the vaporization plane) and it is vital to perform repeated measurements during various seasons.
References:
Huinink HP, Pel L, Kopinga K., 2004. Simulating the growth of tafoni. Earth Surface Processes and Landforms 29: 1225–1233.
Weiss T, Mareš J, Slavík M, Bruthans J. 2020. A microdestructive method using dye-coated-probe to visualize capillary, diffusion and evaporation zones in porous materials. Science of The Total Environment 704, 135339.
How to cite: Mares, J. and Bruthans, J.: Moisture distribution, tensile strength, evaporation rate and origin of coastal honeycombs (Tuscan, Italy) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8770, https://doi.org/10.5194/egusphere-egu21-8770, 2021.
EGU21-8104 | vPICO presentations | GM6.6
Holocene sediment budget for wave-dominated Moruya coastline, southeastern Australia: sediment sources, transport and embayment interconnectivityThomas Oliver, Toru Tamura, Brendan Brooke, Andrew Short, Michael Kinsela, Colin Woodroffe, and Bruce Thom
Sediment budgets on wave-dominated coastlines are important in understanding shoreline behaviour. Coastal sediment compartments provide a means to investigate sediment budgets over a range of time and space scales. This study reconstructs the sediment budget over the mid- to late- Holocene for a secondary coastal compartment on the New South Wales (NSW) south coast ~26 km in length and containing five adjacent but discrete barriers: Barlings Beach, Broulee Beach, Bengello Beach, Moruya Heads Beach and Pedro Beach. Building upon existing morphostratigraphic studies in this region, a new set of Optically Stimulated Luminescence (OSL) ages are reported for foredune ridge successions at previously un-dated sites. Additional Ground Penetrating Radar (GPR) transects complement earlier stratigraphic data, and topographic and bathymetric LiDAR datasets capture the morphology of subaerial coastal deposits and the inner shelf. The results demonstrate two different sediment sources promoting shoreline progradation and coastal barrier construction. A quartz-rich sand, transported onshore from the shoreface as it evolved towards equilibrium, dominates the barrier sequences. Skeletal carbonate sand augmented the quartz sand supply for the northern Barlings and Broulee beaches after ~3000 years ago. Shoreline progradation at Bengello Beach was steady throughout the mid-to late- Holocene. Bengello Beach contains the largest volume of Holocene sand and accreted at an average rate of 3.1 m3/m/yr (for the current shoreline length). Changes in sediment accumulation rate has occurred for the other barrier systems as their shorelines prograded resulting in changes to their alongshore interconnectivity. Rapid infilling of the Pedro Beach embayment by ~4000 years ago initiated headland bypassing northwards to Moruya Heads Beach which only then commenced progradation. In contrast, as Broulee and Bengello Beaches prograded, a tombolo formed in the lee of Broulee Headland which restricted northward sand drift into the Broulee embayment. As these once continuous shorelines became two, a marked increase in skeletal carbonate content at Broulee occurred attesting to shoreline separation and independence of sediment budget. This study emphasises the importance of quantifying the long-term temporal variability in sediment budget and embayment interconnectivity in order to better understand shoreline response to contemporary anthropogenic influences and changing boundary conditions such as sea level and wave climate.
How to cite: Oliver, T., Tamura, T., Brooke, B., Short, A., Kinsela, M., Woodroffe, C., and Thom, B.: Holocene sediment budget for wave-dominated Moruya coastline, southeastern Australia: sediment sources, transport and embayment interconnectivity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8104, https://doi.org/10.5194/egusphere-egu21-8104, 2021.
Sediment budgets on wave-dominated coastlines are important in understanding shoreline behaviour. Coastal sediment compartments provide a means to investigate sediment budgets over a range of time and space scales. This study reconstructs the sediment budget over the mid- to late- Holocene for a secondary coastal compartment on the New South Wales (NSW) south coast ~26 km in length and containing five adjacent but discrete barriers: Barlings Beach, Broulee Beach, Bengello Beach, Moruya Heads Beach and Pedro Beach. Building upon existing morphostratigraphic studies in this region, a new set of Optically Stimulated Luminescence (OSL) ages are reported for foredune ridge successions at previously un-dated sites. Additional Ground Penetrating Radar (GPR) transects complement earlier stratigraphic data, and topographic and bathymetric LiDAR datasets capture the morphology of subaerial coastal deposits and the inner shelf. The results demonstrate two different sediment sources promoting shoreline progradation and coastal barrier construction. A quartz-rich sand, transported onshore from the shoreface as it evolved towards equilibrium, dominates the barrier sequences. Skeletal carbonate sand augmented the quartz sand supply for the northern Barlings and Broulee beaches after ~3000 years ago. Shoreline progradation at Bengello Beach was steady throughout the mid-to late- Holocene. Bengello Beach contains the largest volume of Holocene sand and accreted at an average rate of 3.1 m3/m/yr (for the current shoreline length). Changes in sediment accumulation rate has occurred for the other barrier systems as their shorelines prograded resulting in changes to their alongshore interconnectivity. Rapid infilling of the Pedro Beach embayment by ~4000 years ago initiated headland bypassing northwards to Moruya Heads Beach which only then commenced progradation. In contrast, as Broulee and Bengello Beaches prograded, a tombolo formed in the lee of Broulee Headland which restricted northward sand drift into the Broulee embayment. As these once continuous shorelines became two, a marked increase in skeletal carbonate content at Broulee occurred attesting to shoreline separation and independence of sediment budget. This study emphasises the importance of quantifying the long-term temporal variability in sediment budget and embayment interconnectivity in order to better understand shoreline response to contemporary anthropogenic influences and changing boundary conditions such as sea level and wave climate.
How to cite: Oliver, T., Tamura, T., Brooke, B., Short, A., Kinsela, M., Woodroffe, C., and Thom, B.: Holocene sediment budget for wave-dominated Moruya coastline, southeastern Australia: sediment sources, transport and embayment interconnectivity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8104, https://doi.org/10.5194/egusphere-egu21-8104, 2021.
EGU21-7638 | vPICO presentations | GM6.6
Eemian marine terraces along the Pacific coast of South America (1°N-40°S) allow regional assessments of tectonic forcing from earthquake cycle to glacial-cycle timescalesRoland Freisleben, Julius Jara-Muñoz, Daniel Melnick, José Miguel Martínez, and Manfred Strecker
Abstract. Tectonically active coasts are dynamic environments characterized by the presence of multiple marine terraces formed by the combined effects of wave-erosion, tectonic uplift, and sea-level oscillations at glacial-cycle timescales. Well-preserved erosional terraces from the last interglacial sea-level highstand are ideal marker horizons for reconstructing past sea-level positions and calculating vertical displacement rates, which can be subsequently compared to short-term coastal deformation patterns associated with the earthquake cycle. We carried out an almost continuous mapping of the last interglacial marine terrace along ~5,000 km of the western coast of South America between 1°N and 40°S. We used quantitatively replicable approaches constrained by published terrace-age estimates to ultimately compare elevations and patterns of uplifted terraces with tectonic and climatic parameters in order to evaluate the controlling mechanisms for the formation and preservation of marine terraces, and crustal deformation. Uncertainties were estimated on the basis of measurement errors and the distance from referencing points. Overall, our results indicate a median elevation of 30.1 m, which would imply a median uplift rate of 0.22 m/ka averaged over the past ~125 ka. The patterns of terrace elevation and uplift rate display high-amplitude (~100–200 m) and long-wavelength (~102 km) structures at the Manta Peninsula (Ecuador), the San Juan de Marcona area (central Peru), and the Arauco Peninsula (south-central Chile). Medium-wavelength structures occur at the Mejillones Peninsula and Topocalma in Chile, while short-wavelength (< 10 km) features are for instance located near Los Vilos, Valparaíso, and Carranza, Chile. We interpret the long-wavelength deformation to be controlled by deep-seated processes at the plate interface such as the subduction of major bathymetric anomalies like the Nazca and Carnegie ridges. In contrast, short-wavelength deformation may be primarily controlled by sources in the upper plate such as crustal faulting, which, however, may also be associated with the subduction of topographically less pronounced bathymetric anomalies and varying distances to the trench. Latitudinal differences in climate additionally control the formation and preservation of marine terraces. Based on our synopsis we propose that increasing wave height and tidal range result in enhanced erosion and morphologically well-defined marine terraces in south-central Chile. Conversely, river incision and lateral scouring in areas with high precipitation may degrade marine terraces. Our study emphasizes the importance of using systematic measurements and uniform, quantitative methodologies to characterize and correctly interpret marine terraces at regional scales, especially if they are used to unravel tectonic and climatic forcing mechanisms of their formation.
How to cite: Freisleben, R., Jara-Muñoz, J., Melnick, D., Martínez, J. M., and Strecker, M.: Eemian marine terraces along the Pacific coast of South America (1°N-40°S) allow regional assessments of tectonic forcing from earthquake cycle to glacial-cycle timescales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7638, https://doi.org/10.5194/egusphere-egu21-7638, 2021.
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Abstract. Tectonically active coasts are dynamic environments characterized by the presence of multiple marine terraces formed by the combined effects of wave-erosion, tectonic uplift, and sea-level oscillations at glacial-cycle timescales. Well-preserved erosional terraces from the last interglacial sea-level highstand are ideal marker horizons for reconstructing past sea-level positions and calculating vertical displacement rates, which can be subsequently compared to short-term coastal deformation patterns associated with the earthquake cycle. We carried out an almost continuous mapping of the last interglacial marine terrace along ~5,000 km of the western coast of South America between 1°N and 40°S. We used quantitatively replicable approaches constrained by published terrace-age estimates to ultimately compare elevations and patterns of uplifted terraces with tectonic and climatic parameters in order to evaluate the controlling mechanisms for the formation and preservation of marine terraces, and crustal deformation. Uncertainties were estimated on the basis of measurement errors and the distance from referencing points. Overall, our results indicate a median elevation of 30.1 m, which would imply a median uplift rate of 0.22 m/ka averaged over the past ~125 ka. The patterns of terrace elevation and uplift rate display high-amplitude (~100–200 m) and long-wavelength (~102 km) structures at the Manta Peninsula (Ecuador), the San Juan de Marcona area (central Peru), and the Arauco Peninsula (south-central Chile). Medium-wavelength structures occur at the Mejillones Peninsula and Topocalma in Chile, while short-wavelength (< 10 km) features are for instance located near Los Vilos, Valparaíso, and Carranza, Chile. We interpret the long-wavelength deformation to be controlled by deep-seated processes at the plate interface such as the subduction of major bathymetric anomalies like the Nazca and Carnegie ridges. In contrast, short-wavelength deformation may be primarily controlled by sources in the upper plate such as crustal faulting, which, however, may also be associated with the subduction of topographically less pronounced bathymetric anomalies and varying distances to the trench. Latitudinal differences in climate additionally control the formation and preservation of marine terraces. Based on our synopsis we propose that increasing wave height and tidal range result in enhanced erosion and morphologically well-defined marine terraces in south-central Chile. Conversely, river incision and lateral scouring in areas with high precipitation may degrade marine terraces. Our study emphasizes the importance of using systematic measurements and uniform, quantitative methodologies to characterize and correctly interpret marine terraces at regional scales, especially if they are used to unravel tectonic and climatic forcing mechanisms of their formation.
How to cite: Freisleben, R., Jara-Muñoz, J., Melnick, D., Martínez, J. M., and Strecker, M.: Eemian marine terraces along the Pacific coast of South America (1°N-40°S) allow regional assessments of tectonic forcing from earthquake cycle to glacial-cycle timescales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7638, https://doi.org/10.5194/egusphere-egu21-7638, 2021.
GM6.7 – Underwater paleo-landscape reconstruction by using multi-proxy approaches in the framework of NEPTUNE INQUA Project
EGU21-13192 | vPICO presentations | GM6.7 | Highlight
The Last Interglacial Sea Level database for the Western MediterraneanCiro Cerrone, Matteo Vacchi, Alessandro Fontana, and Alessio Rovere
An open access database containing raw data of Last Interglacial sea-level proxies for the Western Mediterranean has been compiled by reviewing hundreds of original published papers in accordance with the WALIS template (https://warmcoasts.eu/world-atlas.html). WALIS allows collecting both the relative sea-level (RSL) indicators and ages data in a standardized format. Ca. 360 sea-level index points for the coasts of Spain, France, Italy, Albania, Algeria and Morocco have been included in the database. The sea-level index points of the database are related to ca. 350 samples dated by a wide range of dating techniques, e.g., U-series, Amino Acid Racemization, Luminescence (Tl/OSL) and Electron Spin Resonance methods or chronostratigraphically correlated to marine deposits bearing P. latus and “Senegalese fauna”. In fact, for some areas of the Mediterranean Sea, the “Senegalese fauna” is indicative of the MIS 5e.
Among the eleven types of sea-level indicators of our database, the majority of them are represented by marine terraces, beach deposits (or beachrocks), and tidal notches. Whenever the relationship between the RSL indicators and the former sea-level could not be quantified, such indicators have been considered as marine or terrestrial limiting points. An indirect age of the tidal notches has been provided by correlation with the nearby dated deposit. In the case no precise elevation information has been reported by the Authors, the elevation error of RSL datapoints has been reassessed in the 20 % of the elevation value, more a 5% if the sea-level datum was lacking in the scientific papers we have reviewed. Overall, the quality of each RSL datapoints and the associated age have been ranked in a 0 to 5 scale score according to Rovere et al., (2020).
References
Rovere, A., Ryan, D., Murray-Wallace, C., Simms, A., Vacchi, M., Dutton, A., Gowan, E., 2020. Descriptions of database fields for the World Atlas of Last Interglacial Shorelines (WALIS) (Version 1,0). Zenodo. https://doi.org/http://doi.org/10.5281/zenodo.3961544
How to cite: Cerrone, C., Vacchi, M., Fontana, A., and Rovere, A.: The Last Interglacial Sea Level database for the Western Mediterranean , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13192, https://doi.org/10.5194/egusphere-egu21-13192, 2021.
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An open access database containing raw data of Last Interglacial sea-level proxies for the Western Mediterranean has been compiled by reviewing hundreds of original published papers in accordance with the WALIS template (https://warmcoasts.eu/world-atlas.html). WALIS allows collecting both the relative sea-level (RSL) indicators and ages data in a standardized format. Ca. 360 sea-level index points for the coasts of Spain, France, Italy, Albania, Algeria and Morocco have been included in the database. The sea-level index points of the database are related to ca. 350 samples dated by a wide range of dating techniques, e.g., U-series, Amino Acid Racemization, Luminescence (Tl/OSL) and Electron Spin Resonance methods or chronostratigraphically correlated to marine deposits bearing P. latus and “Senegalese fauna”. In fact, for some areas of the Mediterranean Sea, the “Senegalese fauna” is indicative of the MIS 5e.
Among the eleven types of sea-level indicators of our database, the majority of them are represented by marine terraces, beach deposits (or beachrocks), and tidal notches. Whenever the relationship between the RSL indicators and the former sea-level could not be quantified, such indicators have been considered as marine or terrestrial limiting points. An indirect age of the tidal notches has been provided by correlation with the nearby dated deposit. In the case no precise elevation information has been reported by the Authors, the elevation error of RSL datapoints has been reassessed in the 20 % of the elevation value, more a 5% if the sea-level datum was lacking in the scientific papers we have reviewed. Overall, the quality of each RSL datapoints and the associated age have been ranked in a 0 to 5 scale score according to Rovere et al., (2020).
References
Rovere, A., Ryan, D., Murray-Wallace, C., Simms, A., Vacchi, M., Dutton, A., Gowan, E., 2020. Descriptions of database fields for the World Atlas of Last Interglacial Shorelines (WALIS) (Version 1,0). Zenodo. https://doi.org/http://doi.org/10.5281/zenodo.3961544
How to cite: Cerrone, C., Vacchi, M., Fontana, A., and Rovere, A.: The Last Interglacial Sea Level database for the Western Mediterranean , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13192, https://doi.org/10.5194/egusphere-egu21-13192, 2021.
EGU21-11320 | vPICO presentations | GM6.7 | Highlight
Seabed geomorphology of the Prokljan Lake – a Krka River estuary on the eastern Adriatic coast (Dalmatia)Ozren Hasan, Slobodan Miko, Dea Brunović, Natalia Šenolt, Martina Šparica Miko, and Nikolina Ilijanić
Vast areas of the shallow Adriatic shelf were exposed at the time of the Last Glacial Maximum lowstand. This enabled formation of lakes, river valleys and river floodplains that were submerged during the Holocene transgression. Here we present a study of the karst estuary of the Krka River located in central Dalmatia on the eastern Adriatic coast. The Krka River creates a 23 km long estuary extending north from the Šibenik Channel, over the Prokljan Lake, up to the tufa waterfall Skradinski buk. We used high resolution acoustic methods including sub-bottom profiler (SBP) coupled with multibeam echo sounder (MBES) (MBES bathymetry and MBES backscatter) and side-scan sonar (SSS) to investigate the submerged karst river valley and lake system that existed before the Holocene relative sea level rise. A total of 70 km of SBP profiles and a point cloud of 241 991 638 points in the area of 6.2 km2 were collected during the surveys. Water depth ranges from 5 m b.s.l. in the most northern part of the study area, to 25 m b.s.l. in the southern part of the Prokljan lake.
To create a better geomorphological and geological classifications of the seabed, we made a network of 36 ground truthing stations where we sampled sediments with Van Veen grab sampler and obtained underwater images. Sediment samples were analyzed for grain size, bulk density, carbon and nitrogen concentrations, as well as mineralogical XRD analysis and magnetic susceptibility. We combined gathered data with GIS classification tools to create accurate seabed maps of the area. Our results also showed that well-defined submerged river canyon in the Prokljan Lake area was filled with three sedimentary units: fluvial, brackish and marine. Quaternary sediment thickness is up to 15 m. Seabed geomorphology of the investigated area is characterized by many submerged tufa barriers. They are similar to present barriers upstream of the Skradinski buk waterfall. These unique karst geomorphological features, that grow as algae and mosses are encrusted by carbonate, enabled formation of lakes, as well as prevented a marine flooding during the Holocene sea-level rise. The depth of each barrier (4.5 to 12 m b.s.l.), in connection to the onset of marine sedimentation within the estuary, can be used as an indicator of sea level. Barriers are emphasized on the MBES backscatter data as strong reflectors. Grain size of sampled sediments ranges from poorly sorted sand and gravel on underwater barriers to fine silt sediments in the deeper parts of Prokljan Lake. Larger sediment size on barriers is caused by tufa debris while fine silt is sedimented in the deeper parts of the basin. Grain size results vary for different geomorphological provinces, allowing for a more precise (GIS) classification and description of the seabed.
This work was supported by the Croatian Science Foundation Project “Sediments between source and sink during a late Quaternary eustatic cycle: the Krka River and the Mid Adriatic Deep System” (QMAD) (HRZZ IP-04-2019-8505).
How to cite: Hasan, O., Miko, S., Brunović, D., Šenolt, N., Šparica Miko, M., and Ilijanić, N.: Seabed geomorphology of the Prokljan Lake – a Krka River estuary on the eastern Adriatic coast (Dalmatia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11320, https://doi.org/10.5194/egusphere-egu21-11320, 2021.
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Vast areas of the shallow Adriatic shelf were exposed at the time of the Last Glacial Maximum lowstand. This enabled formation of lakes, river valleys and river floodplains that were submerged during the Holocene transgression. Here we present a study of the karst estuary of the Krka River located in central Dalmatia on the eastern Adriatic coast. The Krka River creates a 23 km long estuary extending north from the Šibenik Channel, over the Prokljan Lake, up to the tufa waterfall Skradinski buk. We used high resolution acoustic methods including sub-bottom profiler (SBP) coupled with multibeam echo sounder (MBES) (MBES bathymetry and MBES backscatter) and side-scan sonar (SSS) to investigate the submerged karst river valley and lake system that existed before the Holocene relative sea level rise. A total of 70 km of SBP profiles and a point cloud of 241 991 638 points in the area of 6.2 km2 were collected during the surveys. Water depth ranges from 5 m b.s.l. in the most northern part of the study area, to 25 m b.s.l. in the southern part of the Prokljan lake.
To create a better geomorphological and geological classifications of the seabed, we made a network of 36 ground truthing stations where we sampled sediments with Van Veen grab sampler and obtained underwater images. Sediment samples were analyzed for grain size, bulk density, carbon and nitrogen concentrations, as well as mineralogical XRD analysis and magnetic susceptibility. We combined gathered data with GIS classification tools to create accurate seabed maps of the area. Our results also showed that well-defined submerged river canyon in the Prokljan Lake area was filled with three sedimentary units: fluvial, brackish and marine. Quaternary sediment thickness is up to 15 m. Seabed geomorphology of the investigated area is characterized by many submerged tufa barriers. They are similar to present barriers upstream of the Skradinski buk waterfall. These unique karst geomorphological features, that grow as algae and mosses are encrusted by carbonate, enabled formation of lakes, as well as prevented a marine flooding during the Holocene sea-level rise. The depth of each barrier (4.5 to 12 m b.s.l.), in connection to the onset of marine sedimentation within the estuary, can be used as an indicator of sea level. Barriers are emphasized on the MBES backscatter data as strong reflectors. Grain size of sampled sediments ranges from poorly sorted sand and gravel on underwater barriers to fine silt sediments in the deeper parts of Prokljan Lake. Larger sediment size on barriers is caused by tufa debris while fine silt is sedimented in the deeper parts of the basin. Grain size results vary for different geomorphological provinces, allowing for a more precise (GIS) classification and description of the seabed.
This work was supported by the Croatian Science Foundation Project “Sediments between source and sink during a late Quaternary eustatic cycle: the Krka River and the Mid Adriatic Deep System” (QMAD) (HRZZ IP-04-2019-8505).
How to cite: Hasan, O., Miko, S., Brunović, D., Šenolt, N., Šparica Miko, M., and Ilijanić, N.: Seabed geomorphology of the Prokljan Lake – a Krka River estuary on the eastern Adriatic coast (Dalmatia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11320, https://doi.org/10.5194/egusphere-egu21-11320, 2021.
EGU21-8591 | vPICO presentations | GM6.7 | Highlight
On the origin of multiple tsunami inundation of the archaeological site of Ognina (Sicily): Numerical models and field geological dataGiovanni Scardino, Angela Rizzo, Vincenzo De Santis, Despo Kyriakoudi, Alessio Rovere, Matteo Vacchi, and Giovanni Scicchitano
South-eastern Sicily is among the most seismically active areas of the central Mediterranean. As such, it is marked by a high level of crustal seismicity producing major earthquakes (up to Mw ∼7), and consequent several earthquake-generated tsunami, which have affected the Ionian coast of South-eastern Sicily in historical times. These tsunami events left geomorphic imprints such as large boulders or high-energy deposits along the Sicily coasts. In Ognina, a small town located 20 km south of Siracusa, high-energy deposits were correlated with three tsunami events that struck this coast on 21 July 365 Common Era (CE), 4 February 1169 CE, and 11 January 1693 CE. The deposits are detected in the inner part of a narrow channel, that is thought to have funnelled the tsunami flow energy. In this work, numerical models have been performed to simulate the tsunami impacts, considering the most probable tsunamogenic sources described in literature and integrating them with the past sea-level positions. To this end, we used Delft Dashboard, Delft 3d-FLOW and XBeach. A reconstruction of the past topography of Ognina coast was performed through geological and historical information, in order to model the tsunami wave propagation in the ancient landscape. Geological evidence with model results, under different scenarios, allow us to benchmark fault location and displacement scenarios. Modelling results indicate that the 1693 tsunami event was stronger than others impacting the Ognina area, determining significant inland flooding in the narrow channel. Moreover, simulations show that the most probable tsunamogenic sources of 1693 and 1169 tsunami events could be attributed to Western Fault dislocations occurred off-shore of Ognina area, rather than the other tsunamogenic sources described in literature, located off-shore of Catania and Siracusa. Modelling of 365 AD event shows a long period for the tsunami wave that determined the sedimentation on the lower units in the outcrop. For each of the three tsunami events, models of high-energy deposition match with position and thickness of high-energy layers detected in the field. The results of this study show how a combined approach between geological evidence and tsunami modelling could be a suitable tool for the attribution of tsunami deposits connected to specific tsunamogenic sources.
Keyword: tsunami; earthquake; faults; flooding; sea-level
How to cite: Scardino, G., Rizzo, A., De Santis, V., Kyriakoudi, D., Rovere, A., Vacchi, M., and Scicchitano, G.: On the origin of multiple tsunami inundation of the archaeological site of Ognina (Sicily): Numerical models and field geological data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8591, https://doi.org/10.5194/egusphere-egu21-8591, 2021.
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South-eastern Sicily is among the most seismically active areas of the central Mediterranean. As such, it is marked by a high level of crustal seismicity producing major earthquakes (up to Mw ∼7), and consequent several earthquake-generated tsunami, which have affected the Ionian coast of South-eastern Sicily in historical times. These tsunami events left geomorphic imprints such as large boulders or high-energy deposits along the Sicily coasts. In Ognina, a small town located 20 km south of Siracusa, high-energy deposits were correlated with three tsunami events that struck this coast on 21 July 365 Common Era (CE), 4 February 1169 CE, and 11 January 1693 CE. The deposits are detected in the inner part of a narrow channel, that is thought to have funnelled the tsunami flow energy. In this work, numerical models have been performed to simulate the tsunami impacts, considering the most probable tsunamogenic sources described in literature and integrating them with the past sea-level positions. To this end, we used Delft Dashboard, Delft 3d-FLOW and XBeach. A reconstruction of the past topography of Ognina coast was performed through geological and historical information, in order to model the tsunami wave propagation in the ancient landscape. Geological evidence with model results, under different scenarios, allow us to benchmark fault location and displacement scenarios. Modelling results indicate that the 1693 tsunami event was stronger than others impacting the Ognina area, determining significant inland flooding in the narrow channel. Moreover, simulations show that the most probable tsunamogenic sources of 1693 and 1169 tsunami events could be attributed to Western Fault dislocations occurred off-shore of Ognina area, rather than the other tsunamogenic sources described in literature, located off-shore of Catania and Siracusa. Modelling of 365 AD event shows a long period for the tsunami wave that determined the sedimentation on the lower units in the outcrop. For each of the three tsunami events, models of high-energy deposition match with position and thickness of high-energy layers detected in the field. The results of this study show how a combined approach between geological evidence and tsunami modelling could be a suitable tool for the attribution of tsunami deposits connected to specific tsunamogenic sources.
Keyword: tsunami; earthquake; faults; flooding; sea-level
How to cite: Scardino, G., Rizzo, A., De Santis, V., Kyriakoudi, D., Rovere, A., Vacchi, M., and Scicchitano, G.: On the origin of multiple tsunami inundation of the archaeological site of Ognina (Sicily): Numerical models and field geological data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8591, https://doi.org/10.5194/egusphere-egu21-8591, 2021.
EGU21-13236 | vPICO presentations | GM6.7
Palaeogeographic evolution and sea level changes of a tectonically active area: the case of Psatha, Alkyonides Gulf, GreeceAnna Karkani, Giannis Saitis, Konstantinos Tsanakas, Niki Evelpidou, Efthimios Karymbalis, Emmanuel Vassilakis, Hara Drinia, and Dimitrios-Vasileios Batzakis
The study of environmental changes in coastal areas provide useful information for past conditions and constitute a powerful tool for accurate palaeogeographic reconstructions. Several coastal landforms are present on the coastal zone, with different response to environmental change. Coastal wetlands and lagoons are particularly sensitive to local paleoenvironmental changes and provide an excellent opportunity to reconstruct the evolution of the coastal zone evolution and the sea level changes. In this context, the aim of this work is to elucidate the coastal evolution of Psatha bay, Alkyonides Gulf, Greece, through coastal drillings and geomorphological sea level markers.
The study area is located at the eastern end of Corinth Gulf, in the Gulf of Alkyonides. Psatha is bounded by active neotectonic structures, which have been a determining factor in its development. In this work we adopt a multiproxy approach through the study of coastal drillings and beachrocks, and micro-topography constructed after photogrammetric processing of very high resolution and accuracy images acquired by several Unmanned Aerial System flights. We coupled detailed beachrock mapping, microstratigraphic analysis and luminescence dating to study beachrock outcrops found up to 1 m above the present sea-level. For the palaeoenvironmental reconstruction, multiproxy analyses were undertaken, which included sedimentological analysis of the core, paleontological analysis of macrofauna and microfauna and radiocarbon dating. The results of this work will contribute to the better understanding of a coastal site in a tectonically active area and the relative sea level changes.
This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” (MIS-5033021).
How to cite: Karkani, A., Saitis, G., Tsanakas, K., Evelpidou, N., Karymbalis, E., Vassilakis, E., Drinia, H., and Batzakis, D.-V.: Palaeogeographic evolution and sea level changes of a tectonically active area: the case of Psatha, Alkyonides Gulf, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13236, https://doi.org/10.5194/egusphere-egu21-13236, 2021.
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The study of environmental changes in coastal areas provide useful information for past conditions and constitute a powerful tool for accurate palaeogeographic reconstructions. Several coastal landforms are present on the coastal zone, with different response to environmental change. Coastal wetlands and lagoons are particularly sensitive to local paleoenvironmental changes and provide an excellent opportunity to reconstruct the evolution of the coastal zone evolution and the sea level changes. In this context, the aim of this work is to elucidate the coastal evolution of Psatha bay, Alkyonides Gulf, Greece, through coastal drillings and geomorphological sea level markers.
The study area is located at the eastern end of Corinth Gulf, in the Gulf of Alkyonides. Psatha is bounded by active neotectonic structures, which have been a determining factor in its development. In this work we adopt a multiproxy approach through the study of coastal drillings and beachrocks, and micro-topography constructed after photogrammetric processing of very high resolution and accuracy images acquired by several Unmanned Aerial System flights. We coupled detailed beachrock mapping, microstratigraphic analysis and luminescence dating to study beachrock outcrops found up to 1 m above the present sea-level. For the palaeoenvironmental reconstruction, multiproxy analyses were undertaken, which included sedimentological analysis of the core, paleontological analysis of macrofauna and microfauna and radiocarbon dating. The results of this work will contribute to the better understanding of a coastal site in a tectonically active area and the relative sea level changes.
This research is co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning» in the context of the project “Reinforcement of Postdoctoral Researchers - 2nd Cycle” (MIS-5033021).
How to cite: Karkani, A., Saitis, G., Tsanakas, K., Evelpidou, N., Karymbalis, E., Vassilakis, E., Drinia, H., and Batzakis, D.-V.: Palaeogeographic evolution and sea level changes of a tectonically active area: the case of Psatha, Alkyonides Gulf, Greece, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13236, https://doi.org/10.5194/egusphere-egu21-13236, 2021.
EGU21-10027 | vPICO presentations | GM6.7
Comparing impact effects of common storms and Medicanes along the coast of Southeastern SicilyGiovanni Scardino, Giovanni Scicchitano, Angela Rizzo, Carmelo Monaco, Arcangelo Piscitelli, Maurilio Milella, De Giosa Francesco, and Giuseppe Mastronuzzi
The coastal vulnerability along the Mediterranean coasts is increasing, especially in response to the occurrence of tropical-like events, known as Medicanes, which have become more intense than in the past. A peculiar case was the impact of Medicane Zorbas occurred in September 2018 along the coasts of Southeastern Sicily, where it caused inland flooding and damages to the socio-economic activities. We reconstructed Zorbas effects through post-event geomorphological surveys, interviews to direct witness and analyses of video recorded by surveillance systems or found in the social media. These data allowed to assess the flooding extent on seven coastal sectors located between Thapsos Peninsula and Marzamemi. Flooding caused by Zorbas appears to be greater than those surveyed after the main seasonal storms occurred in the areas from 2015 to 2019, but comparable with the flooding generated by Medicane Qendresa that impacted the southeastern Sicily in 2014. Waves propagation modelling was performed through Delft 3D for the main marine extreme events occurred in the area since 2005, and analyses of data recorded by tide gauge of Catania and Porto Palo di Capo Passero and Malta since 2008 let us to hypothesize that Medicanes generate greater flooding than seasonal storms because they can induce higher and longer surge along the coastline. Collected data indicate that surge generated by Zorbas reached a maximum value between about 0.8 m and 1.2 m above mean sea level (msl) along the coast of southeastern Sicily. Results highlighted the need to better evaluate the coastal hazard related to the propagation of Medicanes, especially in the context of future climate change, when these events could be characterized by a longer duration and a greater intensity than the present, such to cause greater flooding and damage to the coastal areas.
Keywords: coastal flooding; storm wave; storm surge; Medicane; vulnerability.
How to cite: Scardino, G., Scicchitano, G., Rizzo, A., Monaco, C., Piscitelli, A., Milella, M., Francesco, D. G., and Mastronuzzi, G.: Comparing impact effects of common storms and Medicanes along the coast of Southeastern Sicily, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10027, https://doi.org/10.5194/egusphere-egu21-10027, 2021.
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The coastal vulnerability along the Mediterranean coasts is increasing, especially in response to the occurrence of tropical-like events, known as Medicanes, which have become more intense than in the past. A peculiar case was the impact of Medicane Zorbas occurred in September 2018 along the coasts of Southeastern Sicily, where it caused inland flooding and damages to the socio-economic activities. We reconstructed Zorbas effects through post-event geomorphological surveys, interviews to direct witness and analyses of video recorded by surveillance systems or found in the social media. These data allowed to assess the flooding extent on seven coastal sectors located between Thapsos Peninsula and Marzamemi. Flooding caused by Zorbas appears to be greater than those surveyed after the main seasonal storms occurred in the areas from 2015 to 2019, but comparable with the flooding generated by Medicane Qendresa that impacted the southeastern Sicily in 2014. Waves propagation modelling was performed through Delft 3D for the main marine extreme events occurred in the area since 2005, and analyses of data recorded by tide gauge of Catania and Porto Palo di Capo Passero and Malta since 2008 let us to hypothesize that Medicanes generate greater flooding than seasonal storms because they can induce higher and longer surge along the coastline. Collected data indicate that surge generated by Zorbas reached a maximum value between about 0.8 m and 1.2 m above mean sea level (msl) along the coast of southeastern Sicily. Results highlighted the need to better evaluate the coastal hazard related to the propagation of Medicanes, especially in the context of future climate change, when these events could be characterized by a longer duration and a greater intensity than the present, such to cause greater flooding and damage to the coastal areas.
Keywords: coastal flooding; storm wave; storm surge; Medicane; vulnerability.
How to cite: Scardino, G., Scicchitano, G., Rizzo, A., Monaco, C., Piscitelli, A., Milella, M., Francesco, D. G., and Mastronuzzi, G.: Comparing impact effects of common storms and Medicanes along the coast of Southeastern Sicily, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10027, https://doi.org/10.5194/egusphere-egu21-10027, 2021.
EGU21-338 | vPICO presentations | GM6.7
Late Pleistocene to Holocene shallow marine – coastal changing environments and human interaction in the South Bay of Dor, IsraelGilad Shtienberg, Omri Gadol, Thomas Levy, Richard Norris, Tammy Rittenour, Assaf Yasur-Landau, Anthony Tamberino, and Michael Lazar
The Tel-Dor embayment located along the Carmel coast provides a valuable opportunity to study environmental and human interaction due to its protecting geomorphic properties that are unique for the generally linear Israeli coast. Interpretations of seismic profiles collected from transects across the bay show five seismic units that have been correlated to dated and well-analyzed sediment units in coastal cores, enabling a detailed deep time reconstruction of the coastal system over the last ~77 ka. The earliest borehole deposits are low-stand aeolian followed by terrestrial sediments including wetland remains that were subsequently flooded by the mid-Holocene transgression. Evidence of the earliest human settlement submerged Pottery-Neolithic (8.25-7 ka) remains, found immediately above the wetland deposits landward of a submerged aeolianite ridge at the mouth of the bay. The wetland deposits and Pottery-Neolithic settlement remains are at present buried by coastal sand recording middle Holocene sea-level rise and thus, suggesting that these coastal communities were displaced by sea-level transgression ca. 7.6–6.5 ka. The sedimentological and archaeological evidence identified in the stratigraphical sequence of the sheltered bay is a good example of better understanding the essential environmental changes on the shallow shelf and the coastline migration especially in bays and the human settlement adaptations to these changes. This high-resolution reconstruction based on seismic methods in the shallow water and core analysis on land combined with detailed archaeological data from the studied area provides an important addition to the puzzle of the Mediterranean story, the cradle of Western Civilizations.
How to cite: Shtienberg, G., Gadol, O., Levy, T., Norris, R., Rittenour, T., Yasur-Landau, A., Tamberino, A., and Lazar, M.: Late Pleistocene to Holocene shallow marine – coastal changing environments and human interaction in the South Bay of Dor, Israel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-338, https://doi.org/10.5194/egusphere-egu21-338, 2021.
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The Tel-Dor embayment located along the Carmel coast provides a valuable opportunity to study environmental and human interaction due to its protecting geomorphic properties that are unique for the generally linear Israeli coast. Interpretations of seismic profiles collected from transects across the bay show five seismic units that have been correlated to dated and well-analyzed sediment units in coastal cores, enabling a detailed deep time reconstruction of the coastal system over the last ~77 ka. The earliest borehole deposits are low-stand aeolian followed by terrestrial sediments including wetland remains that were subsequently flooded by the mid-Holocene transgression. Evidence of the earliest human settlement submerged Pottery-Neolithic (8.25-7 ka) remains, found immediately above the wetland deposits landward of a submerged aeolianite ridge at the mouth of the bay. The wetland deposits and Pottery-Neolithic settlement remains are at present buried by coastal sand recording middle Holocene sea-level rise and thus, suggesting that these coastal communities were displaced by sea-level transgression ca. 7.6–6.5 ka. The sedimentological and archaeological evidence identified in the stratigraphical sequence of the sheltered bay is a good example of better understanding the essential environmental changes on the shallow shelf and the coastline migration especially in bays and the human settlement adaptations to these changes. This high-resolution reconstruction based on seismic methods in the shallow water and core analysis on land combined with detailed archaeological data from the studied area provides an important addition to the puzzle of the Mediterranean story, the cradle of Western Civilizations.
How to cite: Shtienberg, G., Gadol, O., Levy, T., Norris, R., Rittenour, T., Yasur-Landau, A., Tamberino, A., and Lazar, M.: Late Pleistocene to Holocene shallow marine – coastal changing environments and human interaction in the South Bay of Dor, Israel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-338, https://doi.org/10.5194/egusphere-egu21-338, 2021.
EGU21-9217 | vPICO presentations | GM6.7
Submerged Landscapes across European Seas: Harmonising information through the EMODnet-Geology projectHeather Stewart
The EMODnet Geology project is delivering integrated geological map products that include seabed substrates, sedimentation rates, seafloor geology, Quaternary geology, geomorphology, coastal behaviour, geological events such as submarine landslides and earthquakes, and marine mineral occurrences. The newest addition to the EMODnet Geology project are map products reflecting submerged landscapes of the continental shelf which have been compiled across European Seas for the first time.
Sea level is known to have fluctuated by more than 100 m over repeated glacial cycles, resulting in recurring exposure, inundation and migration of coastlines not only across Europe but worldwide. Landscape response to these changes in sea level, and the preservation of these features on continental shelves around Europe, are an invaluable resource for improving our understanding of human history and environmental change over geological time, while also providing data for potential use in examining future sea-level rise scenarios.
Recent advances in both data acquisition and availability over the last two decades has enabled researchers to more accurately reconstruct the extent and dynamics of fluctuating palaeocoastlines. High-resolution multibeam bathymetry and sub-bottom seismic data, in particular, have resulted in a step change in our understanding of palaeoshorelines and other traces of the original landscape topography and sediments.
The dedicated work package aimed to compile and harmonize available information on submerged landscape features by integrating existing records of palaeoenvironmental indicators with interpretations of geomorphology, stratigraphy and type of sediment. The fully attributed GIS layer comprises more than 10,000 features representing 26 classes of submerged landscape and palaeoenvironmental indicators ranging from mapped and modelled palaeocoastlines, evidence for submerged forests and peats, thickness of post-Last Glacial Maximum sediments and submerged freshwater springs across all European seas. These data will be used to underpin palaeogeographic reconstructions at 20,000, 9000, and 6000 ka BP during the fourth phase of the project (2019-2021).
This paper will present the ongoing data compilation and harmonisation process, current work on regional palaeogeographic reconstructions, primarily efforts towards creation of a pan-European 20,000 ka BP (Last Glacial Maximum) palaeogeographic reconstruction, and summarise key challenges. With preservation of these now submerged features under threat from commercial activities and natural erosion, bringing together existing knowledge through delivery of this work package is timely.
The Submerged Landscapes layer is delivered through the European Geological Data Infrastructure (EGDI) portal (www.emodnet-geology.eu). It is envisaged that the most recent update to the Submerged Landscapes layer (due April 2021) will be of practical use to the NEPTUNE INQUA project.
How to cite: Stewart, H.: Submerged Landscapes across European Seas: Harmonising information through the EMODnet-Geology project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9217, https://doi.org/10.5194/egusphere-egu21-9217, 2021.
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The EMODnet Geology project is delivering integrated geological map products that include seabed substrates, sedimentation rates, seafloor geology, Quaternary geology, geomorphology, coastal behaviour, geological events such as submarine landslides and earthquakes, and marine mineral occurrences. The newest addition to the EMODnet Geology project are map products reflecting submerged landscapes of the continental shelf which have been compiled across European Seas for the first time.
Sea level is known to have fluctuated by more than 100 m over repeated glacial cycles, resulting in recurring exposure, inundation and migration of coastlines not only across Europe but worldwide. Landscape response to these changes in sea level, and the preservation of these features on continental shelves around Europe, are an invaluable resource for improving our understanding of human history and environmental change over geological time, while also providing data for potential use in examining future sea-level rise scenarios.
Recent advances in both data acquisition and availability over the last two decades has enabled researchers to more accurately reconstruct the extent and dynamics of fluctuating palaeocoastlines. High-resolution multibeam bathymetry and sub-bottom seismic data, in particular, have resulted in a step change in our understanding of palaeoshorelines and other traces of the original landscape topography and sediments.
The dedicated work package aimed to compile and harmonize available information on submerged landscape features by integrating existing records of palaeoenvironmental indicators with interpretations of geomorphology, stratigraphy and type of sediment. The fully attributed GIS layer comprises more than 10,000 features representing 26 classes of submerged landscape and palaeoenvironmental indicators ranging from mapped and modelled palaeocoastlines, evidence for submerged forests and peats, thickness of post-Last Glacial Maximum sediments and submerged freshwater springs across all European seas. These data will be used to underpin palaeogeographic reconstructions at 20,000, 9000, and 6000 ka BP during the fourth phase of the project (2019-2021).
This paper will present the ongoing data compilation and harmonisation process, current work on regional palaeogeographic reconstructions, primarily efforts towards creation of a pan-European 20,000 ka BP (Last Glacial Maximum) palaeogeographic reconstruction, and summarise key challenges. With preservation of these now submerged features under threat from commercial activities and natural erosion, bringing together existing knowledge through delivery of this work package is timely.
The Submerged Landscapes layer is delivered through the European Geological Data Infrastructure (EGDI) portal (www.emodnet-geology.eu). It is envisaged that the most recent update to the Submerged Landscapes layer (due April 2021) will be of practical use to the NEPTUNE INQUA project.
How to cite: Stewart, H.: Submerged Landscapes across European Seas: Harmonising information through the EMODnet-Geology project, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9217, https://doi.org/10.5194/egusphere-egu21-9217, 2021.
EGU21-13251 | vPICO presentations | GM6.7
Uplifted marine terraces of Cephalonia island, Western Greece. Insights into the late Quaternary geomorphic evolution of the area.Konstantinos Tsanakas, Giannis Saitis, Niki Evelpidou, Efthimios Karymbalis, and Anna Karkani
Uplifted marine terraces act as a continuous record of eustatic changes in tectonically active coastal areas and can provide significant insight into their late Quaternary geomorphic evolution. Cephalonia island, located at the north-west edge of the Hellenic Arc, is a tectonically and seismically highly active area in the Ionian Sea, western Greece, where collision, subduction and transformation take place in a relatively small region. Pleistocene eustatic sea level fluctuations and the long-term vertical movements of the island, have left their imprint on the southern part of the island in the form of uplifted marine terraces. In the present study we aim to identify and map in detail the uplifted marine terraces, applying Digital Elevation Model analysis, utilizing GIS techniques and extensive fieldwork. A GIS spatial geodatabase has been organized and a GIS-based Automatic Landform Analysis was implemented for the identification and mapping of the inner edge of the uplifted marine terraces. Extensive field work and UAV imagery, enabled us to validate the results of the DEM analysis and to improve the accuracy of the position of the inner edges. A sequence of eight marine terraces has been revealed in the Paliki Peninsula ranging in elevation between 2-16 m above sea level for the lowest terrace and 300-440 m asl for the higher one. In the southern part of the main island 9 marine terraces have been identified and mapped at elevations ranging from 1-2 m for the lower one up to 142-170 m above sea level for the higher one respectively. The majority of the terraces is curved on erodible Pliocene and Pleistocene formations and only the lower ones appear to be well preserved. Their lateral morphological continuity is interrupted by the fluvial activity of a large number of ephemeral streams. The non-uniform occurrence of marine terraces at different elevations in Paliki peninsula and the southern part of the main island implies a complex tectonic activity of the island probably attributed to different tectonic blocks.
How to cite: Tsanakas, K., Saitis, G., Evelpidou, N., Karymbalis, E., and Karkani, A.: Uplifted marine terraces of Cephalonia island, Western Greece. Insights into the late Quaternary geomorphic evolution of the area., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13251, https://doi.org/10.5194/egusphere-egu21-13251, 2021.
Uplifted marine terraces act as a continuous record of eustatic changes in tectonically active coastal areas and can provide significant insight into their late Quaternary geomorphic evolution. Cephalonia island, located at the north-west edge of the Hellenic Arc, is a tectonically and seismically highly active area in the Ionian Sea, western Greece, where collision, subduction and transformation take place in a relatively small region. Pleistocene eustatic sea level fluctuations and the long-term vertical movements of the island, have left their imprint on the southern part of the island in the form of uplifted marine terraces. In the present study we aim to identify and map in detail the uplifted marine terraces, applying Digital Elevation Model analysis, utilizing GIS techniques and extensive fieldwork. A GIS spatial geodatabase has been organized and a GIS-based Automatic Landform Analysis was implemented for the identification and mapping of the inner edge of the uplifted marine terraces. Extensive field work and UAV imagery, enabled us to validate the results of the DEM analysis and to improve the accuracy of the position of the inner edges. A sequence of eight marine terraces has been revealed in the Paliki Peninsula ranging in elevation between 2-16 m above sea level for the lowest terrace and 300-440 m asl for the higher one. In the southern part of the main island 9 marine terraces have been identified and mapped at elevations ranging from 1-2 m for the lower one up to 142-170 m above sea level for the higher one respectively. The majority of the terraces is curved on erodible Pliocene and Pleistocene formations and only the lower ones appear to be well preserved. Their lateral morphological continuity is interrupted by the fluvial activity of a large number of ephemeral streams. The non-uniform occurrence of marine terraces at different elevations in Paliki peninsula and the southern part of the main island implies a complex tectonic activity of the island probably attributed to different tectonic blocks.
How to cite: Tsanakas, K., Saitis, G., Evelpidou, N., Karymbalis, E., and Karkani, A.: Uplifted marine terraces of Cephalonia island, Western Greece. Insights into the late Quaternary geomorphic evolution of the area., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13251, https://doi.org/10.5194/egusphere-egu21-13251, 2021.
EGU21-14997 | vPICO presentations | GM6.7
Erosional landforms and biological structures in tectonically stable areas in the Mediterranean basinValeria Vaccher, Stefano Furlani, Sara Biolchi, Chiara Boccali, Alice Busetti, Fabrizio Antonioli, Matteo Vacchi, Fiorenza Torricella, Mauro Agate, Francesco Caldareri, Renato Chemello, Valeria Lo Presti, Fabio Canziani, Silas Dean, Egidio Trainito, Augusto Navone, Eleonora de Sabata, Marco Anzidei, Joanna Causon Deguara, and Ritienne Gauci and the John A. Schembri (10), Paolo Orrù (11), Marco Taviani (12), Elisa Dal Bo (13), Elisa Venturini (14)
The Mediterranean basin displays a variety of neotectonics scenarios leading to positive or negative vertical displacement, which change the vertical position of former coastlines. As a result, the best locations to evaluate former sea levels and validate sea-level models are tectonically stable areas. There are a number of coastal areas considered to be stable based on the elevation of paleo sea-level markers, the absence of historical seismicity, and by their position far from major Mediterranean faults. We report here the results of swim surveys carried out at such locations following the Geoswim approach described by Furlani (2020) in nine coastal sectors of the central Mediterranean Sea (Egadi Island - Marettimo, Favignana, Levanzo, Gaeta Promontory, Circeo Promontory, North Sardinia - Razzoli, Budelli, Santa Maria, NW Sardinia – Capocaccia, Maddalena Archipelago, Tavolara Island, East of Malta - Ahrax Point, Bugibba-Qawra, Delimara, Addura, Palermo, Ansedonia Promontory). All the sites are considered to be tectonically stable, as validated by the elevation of sea-level indicators. In fact, modern and MIS5.5 (last interglacial) m.s.l. altitudes fit well with accepted figures based upon field data and model projections. Starting from precise morphometric parameters such as the size of tidal notches and indicative landforms and biological structures, we have developed a procedure that integrates multiple geomorphological and biological descriptors applicable to the vast spectrum of locally diverse coastal situations occurring in the Mediterranean Sea. We took detailed measurements of features such as modern and MIS5.5 tidal notches at 146 sites in all the areas, the absence of modern tidal notch at Circeo promontory, shore platforms, and MIS5.5 marine terraces at Egadi islands, Malta, and Palermo. Biological structures were also measured. In particular, vermetid platforms at Egadi, Palermo and Malta. The morphometric characteristics of these indicators depend on 1) local geological and structural constraints, 2) local geomorphotypes, 3) climate, sea, and weather conditions that affect geomorphic and biological processes, and 4) the sea level change history.
How to cite: Vaccher, V., Furlani, S., Biolchi, S., Boccali, C., Busetti, A., Antonioli, F., Vacchi, M., Torricella, F., Agate, M., Caldareri, F., Chemello, R., Lo Presti, V., Canziani, F., Dean, S., Trainito, E., Navone, A., de Sabata, E., Anzidei, M., Causon Deguara, J., and Gauci, R. and the John A. Schembri (10), Paolo Orrù (11), Marco Taviani (12), Elisa Dal Bo (13), Elisa Venturini (14): Erosional landforms and biological structures in tectonically stable areas in the Mediterranean basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14997, https://doi.org/10.5194/egusphere-egu21-14997, 2021.
The Mediterranean basin displays a variety of neotectonics scenarios leading to positive or negative vertical displacement, which change the vertical position of former coastlines. As a result, the best locations to evaluate former sea levels and validate sea-level models are tectonically stable areas. There are a number of coastal areas considered to be stable based on the elevation of paleo sea-level markers, the absence of historical seismicity, and by their position far from major Mediterranean faults. We report here the results of swim surveys carried out at such locations following the Geoswim approach described by Furlani (2020) in nine coastal sectors of the central Mediterranean Sea (Egadi Island - Marettimo, Favignana, Levanzo, Gaeta Promontory, Circeo Promontory, North Sardinia - Razzoli, Budelli, Santa Maria, NW Sardinia – Capocaccia, Maddalena Archipelago, Tavolara Island, East of Malta - Ahrax Point, Bugibba-Qawra, Delimara, Addura, Palermo, Ansedonia Promontory). All the sites are considered to be tectonically stable, as validated by the elevation of sea-level indicators. In fact, modern and MIS5.5 (last interglacial) m.s.l. altitudes fit well with accepted figures based upon field data and model projections. Starting from precise morphometric parameters such as the size of tidal notches and indicative landforms and biological structures, we have developed a procedure that integrates multiple geomorphological and biological descriptors applicable to the vast spectrum of locally diverse coastal situations occurring in the Mediterranean Sea. We took detailed measurements of features such as modern and MIS5.5 tidal notches at 146 sites in all the areas, the absence of modern tidal notch at Circeo promontory, shore platforms, and MIS5.5 marine terraces at Egadi islands, Malta, and Palermo. Biological structures were also measured. In particular, vermetid platforms at Egadi, Palermo and Malta. The morphometric characteristics of these indicators depend on 1) local geological and structural constraints, 2) local geomorphotypes, 3) climate, sea, and weather conditions that affect geomorphic and biological processes, and 4) the sea level change history.
How to cite: Vaccher, V., Furlani, S., Biolchi, S., Boccali, C., Busetti, A., Antonioli, F., Vacchi, M., Torricella, F., Agate, M., Caldareri, F., Chemello, R., Lo Presti, V., Canziani, F., Dean, S., Trainito, E., Navone, A., de Sabata, E., Anzidei, M., Causon Deguara, J., and Gauci, R. and the John A. Schembri (10), Paolo Orrù (11), Marco Taviani (12), Elisa Dal Bo (13), Elisa Venturini (14): Erosional landforms and biological structures in tectonically stable areas in the Mediterranean basin, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14997, https://doi.org/10.5194/egusphere-egu21-14997, 2021.
GM6.8 – Advances in seabed mapping and classification
EGU21-7751 | vPICO presentations | GM6.8
Development of a Seabed Geomorphology classification approach; aspiring towards a robust tool to support comprehensive and consistent seabed mappingDayton Dove, Rachel Nanson, Lilja Bjarnadóttir, Janine Guinan, Joana Gafeira, Alix Post, Margaret F.J. Dolan, Heather Stewart, and Riccardo Arosio
In 2016, through a collaboration between marine mapping programmes in Norway, Ireland, and the UK, we published a new classification scheme to aid the characterisation of seabed geomorphology (Dove et al., 2016). The classification scheme was developed to address shared objectives and challenges in seabed mapping, particularly to enable more consistent classification where required. The novel aspect of this framework was the effort to independently describe seabed features according to their observed physical 1-Morphology, and the more subjective interpretation of their origin and evolution (2-Geomorphology). Initial application of the approach within our own groups and externally proved promising, and through the welcome involvement of colleagues from Geoscience Australia, we continued to progress and improve the approach.
We are now within the second phase of the project, which involves the development of glossaries for both parts of the classification scheme. The glossary for part-1 Morphology was recently completed and published (Dove et al., 2020). This glossary includes a revised list of feature names, with definitions and representative diagrams for each feature. Feature definitions are in-part drawn from the International Hydrographic Organization (IHO) guide for undersea feature names, which were modified and augmented with additional terms to ensure the final feature catalogue and glossary encompasses the diversity of morphologies observed at the seabed.
Part-2 Geomorphology glossary is now in development. We anticipate it to be more complicated than the Morphology glossary due to the (often) variable meaning of different terms between different fields and individual scientists. But as for Part 1, our primary objective is to produce a useful and robust framework (applicable from the coastal zone to the abyss), that minimises duplication and/or ambiguity as much as possible. The Geomorphology glossary will include example bathymetry images to add further value.
Dove, D., Bradwell, T., Carter, G., Cotterill, C., Gafeira Goncalves, J., Green, S., Krabbendam, M., Mellett, C., Stevenson, A., Stewart, H. and Westhead, K., Scott, G., Guinan, J., Judge, M., Monteys, X., Elvenes, S., Maeten, N., Dolan, M., Thorsnes, T., Bjarnadottir, L., Ottesen, D., 2016. Seabed geomorphology: a two-part classification system. British Geological Survey, Open Report OR/16/001.
Dove, D., Nanson, R., Bjarnadóttir, L.R., Guinan, J., Gafeira, J., Post, A., Dolan, M.F.J., Stewart, H., Arosio, R. and Scott, G., 2020. A two-part seabed geomorphology classification scheme:(v. 2). Part 1: morphology features glossary.
How to cite: Dove, D., Nanson, R., Bjarnadóttir, L., Guinan, J., Gafeira, J., Post, A., Dolan, M. F. J., Stewart, H., and Arosio, R.: Development of a Seabed Geomorphology classification approach; aspiring towards a robust tool to support comprehensive and consistent seabed mapping , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7751, https://doi.org/10.5194/egusphere-egu21-7751, 2021.
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In 2016, through a collaboration between marine mapping programmes in Norway, Ireland, and the UK, we published a new classification scheme to aid the characterisation of seabed geomorphology (Dove et al., 2016). The classification scheme was developed to address shared objectives and challenges in seabed mapping, particularly to enable more consistent classification where required. The novel aspect of this framework was the effort to independently describe seabed features according to their observed physical 1-Morphology, and the more subjective interpretation of their origin and evolution (2-Geomorphology). Initial application of the approach within our own groups and externally proved promising, and through the welcome involvement of colleagues from Geoscience Australia, we continued to progress and improve the approach.
We are now within the second phase of the project, which involves the development of glossaries for both parts of the classification scheme. The glossary for part-1 Morphology was recently completed and published (Dove et al., 2020). This glossary includes a revised list of feature names, with definitions and representative diagrams for each feature. Feature definitions are in-part drawn from the International Hydrographic Organization (IHO) guide for undersea feature names, which were modified and augmented with additional terms to ensure the final feature catalogue and glossary encompasses the diversity of morphologies observed at the seabed.
Part-2 Geomorphology glossary is now in development. We anticipate it to be more complicated than the Morphology glossary due to the (often) variable meaning of different terms between different fields and individual scientists. But as for Part 1, our primary objective is to produce a useful and robust framework (applicable from the coastal zone to the abyss), that minimises duplication and/or ambiguity as much as possible. The Geomorphology glossary will include example bathymetry images to add further value.
Dove, D., Bradwell, T., Carter, G., Cotterill, C., Gafeira Goncalves, J., Green, S., Krabbendam, M., Mellett, C., Stevenson, A., Stewart, H. and Westhead, K., Scott, G., Guinan, J., Judge, M., Monteys, X., Elvenes, S., Maeten, N., Dolan, M., Thorsnes, T., Bjarnadottir, L., Ottesen, D., 2016. Seabed geomorphology: a two-part classification system. British Geological Survey, Open Report OR/16/001.
Dove, D., Nanson, R., Bjarnadóttir, L.R., Guinan, J., Gafeira, J., Post, A., Dolan, M.F.J., Stewart, H., Arosio, R. and Scott, G., 2020. A two-part seabed geomorphology classification scheme:(v. 2). Part 1: morphology features glossary.
How to cite: Dove, D., Nanson, R., Bjarnadóttir, L., Guinan, J., Gafeira, J., Post, A., Dolan, M. F. J., Stewart, H., and Arosio, R.: Development of a Seabed Geomorphology classification approach; aspiring towards a robust tool to support comprehensive and consistent seabed mapping , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7751, https://doi.org/10.5194/egusphere-egu21-7751, 2021.
EGU21-1414 | vPICO presentations | GM6.8
Developing multiscale terrain signatures for seabed classificationVincent Lecours
It is increasingly recognized that environmental variables must be considered at multiple spatial scales to produce maps of the seabed that better capture and represent geomorphic features and marine habitats. In this paper, the ability of new multiscale geomorphometric variables to classify different types of seabed habitats is tested. A digital terrain model of an area of coastal Florida with different types of intertidal habitats was used in the geospatial data analysis platform Whitebox Tools to generate multiscale measures of roughness, maximum deviation from mean elevation, maximum anisotropy in elevation deviation, maximum difference from mean elevation, and maximum spherical standard deviation. Results show that oyster reefs, muddy areas, and areas with aquatic vegetation have different multiscale terrain signatures, highlighting the potential of multiscale terrain attributes to inform seabed classification.
How to cite: Lecours, V.: Developing multiscale terrain signatures for seabed classification, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1414, https://doi.org/10.5194/egusphere-egu21-1414, 2021.
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It is increasingly recognized that environmental variables must be considered at multiple spatial scales to produce maps of the seabed that better capture and represent geomorphic features and marine habitats. In this paper, the ability of new multiscale geomorphometric variables to classify different types of seabed habitats is tested. A digital terrain model of an area of coastal Florida with different types of intertidal habitats was used in the geospatial data analysis platform Whitebox Tools to generate multiscale measures of roughness, maximum deviation from mean elevation, maximum anisotropy in elevation deviation, maximum difference from mean elevation, and maximum spherical standard deviation. Results show that oyster reefs, muddy areas, and areas with aquatic vegetation have different multiscale terrain signatures, highlighting the potential of multiscale terrain attributes to inform seabed classification.
How to cite: Lecours, V.: Developing multiscale terrain signatures for seabed classification, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1414, https://doi.org/10.5194/egusphere-egu21-1414, 2021.
EGU21-11157 | vPICO presentations | GM6.8
The utility of Sentinel 2 for bathymetry in turbid waters: a case study in the Gulf d’Arguin, MauritaniaRon Abileah
The Golfe d’Arguin (NW Mauritania) is a 15,000 km2 shelf, 150 km in N-S, and 150 km offshore. The Golfe is subdivided into inner and outer shelves. The shallow (<10m) inner shelf, also known as Banc d’Arguin, is part of a UNESCO World Heritage Site and renowned for a richly diverse marine ecosystem. A steep escarpment separates the deeper (20-200 m) outer shelf. The bottom morphology of both zones is a complex system of shoals, canyons, and channels.
The water is too turbid for traditional optical remote sensing bathymetry. The alternative is bathymetry derived from ocean wave celerity as waves shoal over the shelf.
The celerity method has been practiced for several decades, but only with small sensor footprints (typically 10-100 km2). The Sentinel 2 satellites (now two, with plans to expand to four) have a 290 km push-broom image swath, capturing 2100 km2 per second. The entire Earth is imaged every 4-5 days. The imagery is free, very accessible, and easy to process. The Sentinel 2 image archive is five years and growing daily. Mapping large regions such as the Golfe d’Arguin is made possible.
This presentation describes the Sentinel 2 bathymetry workflow. The Golfe d’Arguin is an excellent case study. Long swell waves from mid-Atlantic storms are frequent. Long waves are best for sensing the bottom depth. (Conversely, the method does not work in locations such as the Persian Gulf shielded from oceanic wave systems.)
For the test case, the horizontal resolution is 200m, covers depths 0 to 35 m, and accuracy is 5% of depth. Comparisons are made with the General Bathymetric Chart of the Oceans (GEBCO), EMODnet DTM, and various literature sources. GEBCO compares very poorly. EMODnet is better but with much lower spatial resolution and does not capture the morphological detail seen in Sentinel 2 derived bathymetry.
There is very limited ground truth bathymetry, e.g., Multibeam, in this area for rigorous validation. Other validation methods are presented. One is Sentinel 2 bathymetry of the Perth Australia area, with wave conditions similar to Mauritania, and a LiDAR survey for ground truth. Another is repeatability with images from different dates.
Below links preview Golfe d’Arguin bathymetry with Sentinel 2 and EMODnet for comparison. GoogleEarth can be used to view.
http://jOmegak.com/vEGU/28QBH.Sentinel2.kmz
http://jOmegak.com/vEGU/28QBH.EMOD.kmz
How to cite: Abileah, R.: The utility of Sentinel 2 for bathymetry in turbid waters: a case study in the Gulf d’Arguin, Mauritania, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11157, https://doi.org/10.5194/egusphere-egu21-11157, 2021.
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The Golfe d’Arguin (NW Mauritania) is a 15,000 km2 shelf, 150 km in N-S, and 150 km offshore. The Golfe is subdivided into inner and outer shelves. The shallow (<10m) inner shelf, also known as Banc d’Arguin, is part of a UNESCO World Heritage Site and renowned for a richly diverse marine ecosystem. A steep escarpment separates the deeper (20-200 m) outer shelf. The bottom morphology of both zones is a complex system of shoals, canyons, and channels.
The water is too turbid for traditional optical remote sensing bathymetry. The alternative is bathymetry derived from ocean wave celerity as waves shoal over the shelf.
The celerity method has been practiced for several decades, but only with small sensor footprints (typically 10-100 km2). The Sentinel 2 satellites (now two, with plans to expand to four) have a 290 km push-broom image swath, capturing 2100 km2 per second. The entire Earth is imaged every 4-5 days. The imagery is free, very accessible, and easy to process. The Sentinel 2 image archive is five years and growing daily. Mapping large regions such as the Golfe d’Arguin is made possible.
This presentation describes the Sentinel 2 bathymetry workflow. The Golfe d’Arguin is an excellent case study. Long swell waves from mid-Atlantic storms are frequent. Long waves are best for sensing the bottom depth. (Conversely, the method does not work in locations such as the Persian Gulf shielded from oceanic wave systems.)
For the test case, the horizontal resolution is 200m, covers depths 0 to 35 m, and accuracy is 5% of depth. Comparisons are made with the General Bathymetric Chart of the Oceans (GEBCO), EMODnet DTM, and various literature sources. GEBCO compares very poorly. EMODnet is better but with much lower spatial resolution and does not capture the morphological detail seen in Sentinel 2 derived bathymetry.
There is very limited ground truth bathymetry, e.g., Multibeam, in this area for rigorous validation. Other validation methods are presented. One is Sentinel 2 bathymetry of the Perth Australia area, with wave conditions similar to Mauritania, and a LiDAR survey for ground truth. Another is repeatability with images from different dates.
Below links preview Golfe d’Arguin bathymetry with Sentinel 2 and EMODnet for comparison. GoogleEarth can be used to view.
http://jOmegak.com/vEGU/28QBH.Sentinel2.kmz
http://jOmegak.com/vEGU/28QBH.EMOD.kmz
How to cite: Abileah, R.: The utility of Sentinel 2 for bathymetry in turbid waters: a case study in the Gulf d’Arguin, Mauritania, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11157, https://doi.org/10.5194/egusphere-egu21-11157, 2021.
EGU21-11160 | vPICO presentations | GM6.8
Geology of the Charlie Gibbs transform system (52-53ºN, Mid Atlantic Ridge): preliminary results from Akademik Nikolaj Strakhov Expedition S50Alessio Sanfilippo, Sergey Skolotnev, and Alexander Peyve and the A.N. Strakhov Expedition S50 Science Party
The Charlie Gibbs offsetting by ~340 km the Mid Atlantic Ridge (MAR) axis between 52°-53° N is one of the main transform systems of the North Atlantic. Located between long mid-ocean ridge segments influenced to the south by the Azores and to the north by the Iceland mantle plume, this transform system has been active since the early phases of North Atlantic rifting. Object of several surveys in the ‘70 and ‘80, Charlie Gibbs received great attention for its unique structure characterized by two long-lived right-lateral transform faults linked by a short ~40 km-long intra-transform spreading centre (ITR) with parallel fracture zone valleys extending continuously towards the continental margins. In October 2020 expedition S50 of the R/V A.N. Strakhov surveyed an area of 54552 km2 covering the entire Charlie Gibbs transform system and the adjacent MAR spreading segments. We collected new bathymetric, magnetic and high-resolution single channel seismic data, along with basaltic, gabbroic and mantle rocks from 21 dredges. In this contribution we present preliminary data from cruise S50 and discusses the large-scale architecture of this unique, long-lived transform system.
How to cite: Sanfilippo, A., Skolotnev, S., and Peyve, A. and the A.N. Strakhov Expedition S50 Science Party: Geology of the Charlie Gibbs transform system (52-53ºN, Mid Atlantic Ridge): preliminary results from Akademik Nikolaj Strakhov Expedition S50, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11160, https://doi.org/10.5194/egusphere-egu21-11160, 2021.
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The Charlie Gibbs offsetting by ~340 km the Mid Atlantic Ridge (MAR) axis between 52°-53° N is one of the main transform systems of the North Atlantic. Located between long mid-ocean ridge segments influenced to the south by the Azores and to the north by the Iceland mantle plume, this transform system has been active since the early phases of North Atlantic rifting. Object of several surveys in the ‘70 and ‘80, Charlie Gibbs received great attention for its unique structure characterized by two long-lived right-lateral transform faults linked by a short ~40 km-long intra-transform spreading centre (ITR) with parallel fracture zone valleys extending continuously towards the continental margins. In October 2020 expedition S50 of the R/V A.N. Strakhov surveyed an area of 54552 km2 covering the entire Charlie Gibbs transform system and the adjacent MAR spreading segments. We collected new bathymetric, magnetic and high-resolution single channel seismic data, along with basaltic, gabbroic and mantle rocks from 21 dredges. In this contribution we present preliminary data from cruise S50 and discusses the large-scale architecture of this unique, long-lived transform system.
How to cite: Sanfilippo, A., Skolotnev, S., and Peyve, A. and the A.N. Strakhov Expedition S50 Science Party: Geology of the Charlie Gibbs transform system (52-53ºN, Mid Atlantic Ridge): preliminary results from Akademik Nikolaj Strakhov Expedition S50, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11160, https://doi.org/10.5194/egusphere-egu21-11160, 2021.
EGU21-16227 | vPICO presentations | GM6.8 | Highlight
High resolution mapping of the Arctic Ocean deepest area: Molloy HoleRoberta Ivaldi, Maurizio Demarte, Massimiliano Nannini, Giuseppe Aquino, Cosimo Brancati, Massimo Ercolani, Agnese Fares, Matteo Guideri, Luca Labella, Mauro Marro, Federica Maurantonio, Roberto Nardini, and Alberto Niccolini
New hydro-oceanographic data were collected in the Arctic Ocean during HIGN NORTH20 marine geophysical campaign performed in July 2020, in a COVID-19 pandemic period. HIGH NORTH20 was developed as part of the IT-Navy HIGH NORTH program, a Pluriannual Joint Research Program in the Arctic devoted to contribute to oceans knowledge in order to ensure ocean science improving conditions for sustainable development of the Ocean in the aim of United Nations Decade of Ocean Science for Sustainable development and the GEBCO - SEABED 2030 project. In order to contribute in exploration and high-resolution seabed mapping new data was collected using a multibeam echosounder (EM 302 - 30 kHz). The particular sea ice environmental condition with open-sea allowed to survey and mapping the Molloy Hole, the deepest sector of the Arctic Ocean, a key area in the global geodynamics and oceanographic context. A 3D model of the Molloy Hole (804 km2) and the detection of the deepest seafloor (5567m - 79° 08.9’ N 002° 47.0’ E) was obtained with a 10x10m grid in compliance to the IHO standards.
How to cite: Ivaldi, R., Demarte, M., Nannini, M., Aquino, G., Brancati, C., Ercolani, M., Fares, A., Guideri, M., Labella, L., Marro, M., Maurantonio, F., Nardini, R., and Niccolini, A.: High resolution mapping of the Arctic Ocean deepest area: Molloy Hole, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16227, https://doi.org/10.5194/egusphere-egu21-16227, 2021.
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New hydro-oceanographic data were collected in the Arctic Ocean during HIGN NORTH20 marine geophysical campaign performed in July 2020, in a COVID-19 pandemic period. HIGH NORTH20 was developed as part of the IT-Navy HIGH NORTH program, a Pluriannual Joint Research Program in the Arctic devoted to contribute to oceans knowledge in order to ensure ocean science improving conditions for sustainable development of the Ocean in the aim of United Nations Decade of Ocean Science for Sustainable development and the GEBCO - SEABED 2030 project. In order to contribute in exploration and high-resolution seabed mapping new data was collected using a multibeam echosounder (EM 302 - 30 kHz). The particular sea ice environmental condition with open-sea allowed to survey and mapping the Molloy Hole, the deepest sector of the Arctic Ocean, a key area in the global geodynamics and oceanographic context. A 3D model of the Molloy Hole (804 km2) and the detection of the deepest seafloor (5567m - 79° 08.9’ N 002° 47.0’ E) was obtained with a 10x10m grid in compliance to the IHO standards.
How to cite: Ivaldi, R., Demarte, M., Nannini, M., Aquino, G., Brancati, C., Ercolani, M., Fares, A., Guideri, M., Labella, L., Marro, M., Maurantonio, F., Nardini, R., and Niccolini, A.: High resolution mapping of the Arctic Ocean deepest area: Molloy Hole, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16227, https://doi.org/10.5194/egusphere-egu21-16227, 2021.
EGU21-8254 | vPICO presentations | GM6.8
Classification of stones in coastal marine environments using random forest machine learning on topo-bathymetric LiDAR dataSigne Schilling Hansen, Verner Brandbyge Ernstsen, Mikkel Skovgaard Andersen, Zyad Al-Hamdani, Ramona Baran, Manfred Niederwieser, Frank Steinbacher, and Aart Kroon
Stones on the seabed in coastal marine environments form an important hard substrate for macroalgae, and hence for coastal marine reefs. Such reef areas constitute important ecosystem services, e.g. storage of organic carbon in macroalgae or “blue carbon” as well as important habitats to fish for living, hiding and feeding. Information and knowledge about stone locations and geometry in coastal marine environments are often obtained as part of seabed habitat mapping. Usually, seabed habitat mapping is based on geophysical surveys using multibeam echo sounding along with side-scan sonar imaging in combination with biological ground-truthing. However, coastal areas are challenging to map with full spatial coverage due to the shallow water conditions. Furthermore, the research vessels often have too large drafts to sail in very shallow water close to the coastline. An alternative is to use airborne LiDAR technology. Topo-bathymetric LiDAR (green wavelength of 532 nm) has made it possible to derive high-resolution data of the bathymetry in coastal zones (e.g. Andersen et al., 2017). This technology can cover the transition zone between land and water, and the time consumption for data acquisition is small compared to vessel borne methods. However, the processing of the data still requires manual decision steps, which makes it rather time consuming, and to some extent subjective.
The aim of this study was to investigate the possibility of developing an automated method to classify stones from topo-bathymetric LiDAR data in coastal marine environments with shallow water (<6 m). The Rødsand lagoon in Denmark, where topo-bathymetric LiDAR data were acquired in 2015, was used as test. The classification was done using the random forest machine learning algorithm. The study resulted in the development of a nearly automated method to classify stones from topo-bathymetric LiDAR data. The classification accuracy was between 80 and 90% for the test site. The obtained knowledge about stone locations can provide important information about the ecosystem services and improved management of the coastal marine environment.
Acknowledgement:
This work is part of the project "ECOMAP - Baltic Sea environmental assessments by opto-acoustic remote sensing, mapping, and monitoring", supported by BONUS (Art 185), funded jointly by the EU and the Innovation Fund Denmark.
References
Andersen MS, Gergely A, Al-Hamdani Z, Steinbacher F, Larsen LR, Ernstsen VB (2017). Processing and performance of topobathymetric lidar data for geomorphometric and morphological classification in a high-energy tidal environment. Hydrology and Earth System Sciences, 21: 43-63, DOI: 10.5194/hess-21-43-2017.
How to cite: Hansen, S. S., Ernstsen, V. B., Andersen, M. S., Al-Hamdani, Z., Baran, R., Niederwieser, M., Steinbacher, F., and Kroon, A.: Classification of stones in coastal marine environments using random forest machine learning on topo-bathymetric LiDAR data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8254, https://doi.org/10.5194/egusphere-egu21-8254, 2021.
Stones on the seabed in coastal marine environments form an important hard substrate for macroalgae, and hence for coastal marine reefs. Such reef areas constitute important ecosystem services, e.g. storage of organic carbon in macroalgae or “blue carbon” as well as important habitats to fish for living, hiding and feeding. Information and knowledge about stone locations and geometry in coastal marine environments are often obtained as part of seabed habitat mapping. Usually, seabed habitat mapping is based on geophysical surveys using multibeam echo sounding along with side-scan sonar imaging in combination with biological ground-truthing. However, coastal areas are challenging to map with full spatial coverage due to the shallow water conditions. Furthermore, the research vessels often have too large drafts to sail in very shallow water close to the coastline. An alternative is to use airborne LiDAR technology. Topo-bathymetric LiDAR (green wavelength of 532 nm) has made it possible to derive high-resolution data of the bathymetry in coastal zones (e.g. Andersen et al., 2017). This technology can cover the transition zone between land and water, and the time consumption for data acquisition is small compared to vessel borne methods. However, the processing of the data still requires manual decision steps, which makes it rather time consuming, and to some extent subjective.
The aim of this study was to investigate the possibility of developing an automated method to classify stones from topo-bathymetric LiDAR data in coastal marine environments with shallow water (<6 m). The Rødsand lagoon in Denmark, where topo-bathymetric LiDAR data were acquired in 2015, was used as test. The classification was done using the random forest machine learning algorithm. The study resulted in the development of a nearly automated method to classify stones from topo-bathymetric LiDAR data. The classification accuracy was between 80 and 90% for the test site. The obtained knowledge about stone locations can provide important information about the ecosystem services and improved management of the coastal marine environment.
Acknowledgement:
This work is part of the project "ECOMAP - Baltic Sea environmental assessments by opto-acoustic remote sensing, mapping, and monitoring", supported by BONUS (Art 185), funded jointly by the EU and the Innovation Fund Denmark.
References
Andersen MS, Gergely A, Al-Hamdani Z, Steinbacher F, Larsen LR, Ernstsen VB (2017). Processing and performance of topobathymetric lidar data for geomorphometric and morphological classification in a high-energy tidal environment. Hydrology and Earth System Sciences, 21: 43-63, DOI: 10.5194/hess-21-43-2017.
How to cite: Hansen, S. S., Ernstsen, V. B., Andersen, M. S., Al-Hamdani, Z., Baran, R., Niederwieser, M., Steinbacher, F., and Kroon, A.: Classification of stones in coastal marine environments using random forest machine learning on topo-bathymetric LiDAR data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8254, https://doi.org/10.5194/egusphere-egu21-8254, 2021.
EGU21-10605 | vPICO presentations | GM6.8
Large-Scale Mapping of Boulder Distribution in Acoustic Backscatter Data of the Baltic Sea by Neural NetworksPeter Feldens, Agata Feldens, Anne Herbst, Alexander Darr, and Svenja Papenmeier
The identification of marine cobbles and boulders (stones) based on acoustic remote sensing is important for the detection, delineation and for an ecological assessment of important seafloor habitats. Due to the large areas involved and the required high-resolution data, a manual interpretation is not feasible. In recent years, automated methods for stone detection were developed. However, these developments were only applied in comparatively small proof of concept areas, and a common barrier to practical implementation by authorities is the required upscaling. This case study aims to apply automated methods for boulder detection based on convolutional neural networks to larger areas, by identifying and validating boulder densities over several hundred km2 in the western Baltic Sea in acoustic backscatter data and derived datasets. The use of distributed training sites of less than 0.5 km2 in size is proposed to improve the model capacity to adapt to variations of boulder appearance in remote sensing data related to local geological variation and survey conditions. Distributed validation sites of similar size are suggested to provide quality control during reprocessing with adapted models. Current limitations for the automated identification of individual boulders in backscatter data are demonstrated, which can be caused by survey geometry, data quality or obstacles and seafloor with similar acoustic characteristics.
How to cite: Feldens, P., Feldens, A., Herbst, A., Darr, A., and Papenmeier, S.: Large-Scale Mapping of Boulder Distribution in Acoustic Backscatter Data of the Baltic Sea by Neural Networks , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10605, https://doi.org/10.5194/egusphere-egu21-10605, 2021.
The identification of marine cobbles and boulders (stones) based on acoustic remote sensing is important for the detection, delineation and for an ecological assessment of important seafloor habitats. Due to the large areas involved and the required high-resolution data, a manual interpretation is not feasible. In recent years, automated methods for stone detection were developed. However, these developments were only applied in comparatively small proof of concept areas, and a common barrier to practical implementation by authorities is the required upscaling. This case study aims to apply automated methods for boulder detection based on convolutional neural networks to larger areas, by identifying and validating boulder densities over several hundred km2 in the western Baltic Sea in acoustic backscatter data and derived datasets. The use of distributed training sites of less than 0.5 km2 in size is proposed to improve the model capacity to adapt to variations of boulder appearance in remote sensing data related to local geological variation and survey conditions. Distributed validation sites of similar size are suggested to provide quality control during reprocessing with adapted models. Current limitations for the automated identification of individual boulders in backscatter data are demonstrated, which can be caused by survey geometry, data quality or obstacles and seafloor with similar acoustic characteristics.
How to cite: Feldens, P., Feldens, A., Herbst, A., Darr, A., and Papenmeier, S.: Large-Scale Mapping of Boulder Distribution in Acoustic Backscatter Data of the Baltic Sea by Neural Networks , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10605, https://doi.org/10.5194/egusphere-egu21-10605, 2021.
EGU21-15899 | vPICO presentations | GM6.8
Mapping shallow water bubbling reefs – a method comparison between topobathymetric lidar and multibeam echosounderMikkel Skovgaard Andersen, Lars Øbro Hansen, Zyad Al-Hamdani, Signe Schilling Hansen, Manfred Niederwieser, Ramona Baran, Frank Steinbacher, and Verner Brandbyge Ernstsen
Bubbling reefs are submarine structures formed by aggregating carbonate resulting from leaking gases. The reef formations can form pillars rising several meters above the sea floor. They support a high diversity of benthic communities, and in the EU Habitat Directive they are specifically mentioned as a natural habitat type that require conservation.
Knowledge about the presence, locations and shape of bubbling reefs are usually obtained by geophysical surveying using multibeam echosounder (MBES), sidescan sonar and/or seismic acquisition systems, combined with ground truth verification. However, this traditional survey method is time consuming, especially for full coverage surveys in shallow water. Full coverage surveys are a requirement to capture the bubbling reefs due to their relatively small spatial extent. Besides, traditional geophysical vessel borne surveys have their limitations in shallow water due to low spatial coverage and vessel draft.
In recent years, airborne topobathymetric (green wavelength) lidar has emerged as a new possible surveying method in shallow water (e.g. Andersen et al., 2017). Compared to vessel borne MBES, full coverage lidar surveys can be conducted within hours instead of days/weeks, while also including full coverage in the shallow water and a seamless transition between land and water. Thus, topobathymetric lidar may be a good choice for carrying out full coverage surveys in large shallow water areas. However, the accuracy and the resolution of the collected dataset are important in these surveys, not least when mapping small scale features such as bubbling reefs.
In this study, we investigated the potential of mapping bubbling reefs in shallow water (<10 m) using topobathymetric lidar. The main objective was to assess the performance of airborne topobathymetric lidar to detect and resolve small scale objects, i.e. bubbling reefs, by comparison to MBES data. Both MBES and lidar data were acquired in spring 2019 in a designated Natura 2000 area close to Hirsholmene in the northern Kattegat region in Denmark. The comparison of the two datasets included a quantification of the accuracy, and an assessment of the performance for mapping bubbling reefs.
Reference:
Andersen M.S., Gergely A., Al-Hamdani Z., Steinbacher F., Larsen L.R., Ernstsen V.B. (2017). Processing and performance of topobathymetric lidar data for geomorphometric and morphological classification in a high-energy tidal environment. Hydrology and Earth System Sciences, 21: 43-63, DOI: 10.5194/hess-21-43-2017.
How to cite: Andersen, M. S., Hansen, L. Ø., Al-Hamdani, Z., Hansen, S. S., Niederwieser, M., Baran, R., Steinbacher, F., and Ernstsen, V. B.: Mapping shallow water bubbling reefs – a method comparison between topobathymetric lidar and multibeam echosounder, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15899, https://doi.org/10.5194/egusphere-egu21-15899, 2021.
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Bubbling reefs are submarine structures formed by aggregating carbonate resulting from leaking gases. The reef formations can form pillars rising several meters above the sea floor. They support a high diversity of benthic communities, and in the EU Habitat Directive they are specifically mentioned as a natural habitat type that require conservation.
Knowledge about the presence, locations and shape of bubbling reefs are usually obtained by geophysical surveying using multibeam echosounder (MBES), sidescan sonar and/or seismic acquisition systems, combined with ground truth verification. However, this traditional survey method is time consuming, especially for full coverage surveys in shallow water. Full coverage surveys are a requirement to capture the bubbling reefs due to their relatively small spatial extent. Besides, traditional geophysical vessel borne surveys have their limitations in shallow water due to low spatial coverage and vessel draft.
In recent years, airborne topobathymetric (green wavelength) lidar has emerged as a new possible surveying method in shallow water (e.g. Andersen et al., 2017). Compared to vessel borne MBES, full coverage lidar surveys can be conducted within hours instead of days/weeks, while also including full coverage in the shallow water and a seamless transition between land and water. Thus, topobathymetric lidar may be a good choice for carrying out full coverage surveys in large shallow water areas. However, the accuracy and the resolution of the collected dataset are important in these surveys, not least when mapping small scale features such as bubbling reefs.
In this study, we investigated the potential of mapping bubbling reefs in shallow water (<10 m) using topobathymetric lidar. The main objective was to assess the performance of airborne topobathymetric lidar to detect and resolve small scale objects, i.e. bubbling reefs, by comparison to MBES data. Both MBES and lidar data were acquired in spring 2019 in a designated Natura 2000 area close to Hirsholmene in the northern Kattegat region in Denmark. The comparison of the two datasets included a quantification of the accuracy, and an assessment of the performance for mapping bubbling reefs.
Reference:
Andersen M.S., Gergely A., Al-Hamdani Z., Steinbacher F., Larsen L.R., Ernstsen V.B. (2017). Processing and performance of topobathymetric lidar data for geomorphometric and morphological classification in a high-energy tidal environment. Hydrology and Earth System Sciences, 21: 43-63, DOI: 10.5194/hess-21-43-2017.
How to cite: Andersen, M. S., Hansen, L. Ø., Al-Hamdani, Z., Hansen, S. S., Niederwieser, M., Baran, R., Steinbacher, F., and Ernstsen, V. B.: Mapping shallow water bubbling reefs – a method comparison between topobathymetric lidar and multibeam echosounder, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15899, https://doi.org/10.5194/egusphere-egu21-15899, 2021.
EGU21-102 | vPICO presentations | GM6.8
Small Island Developing States (SIDS) and the sea: creating high resolution habitat maps to support effective marine management in St. LuciaRiccardo Arosio, Peter Mitchell, Jon Hawes, Stefan Bolam, Lisa Benson, and John Sperry
This study, conducted under the auspices of the Commonwealth Marine Economies Programme (CMEP), involved the characterisation of geomorphology and benthic assemblage groups around the previously unmapped western St. Lucian coastline. A high-resolution (2 x 2 m) seabed map was then produced, specifically focussing on the economically important regions.
Two hundred twelve video tow transects were acquired by CEFAS and associated to Multibeam echosounder (MBES) data collected by the United Kingdom Hydrographic Office (UKHO). Through object-based image analysis, MBES data and derivatives were categorized into eight basic morphological classes (e.g. slope, flat), with manual intervention required to further discriminate more complex forms (e.g. anthropogenic scours). Percentage coverage of epibenthic biota and substrate type data were extracted from still seabed images using the CATAMI[1] morphological classification system and a randomised point count approach. Benthic community assemblages were then defined based on K-means clustering. A random forest model was used to predict benthic community groups. Predictive layers included MBES-derived physical properties, geomorphological classes and wave exposure (using GREMO[2]). The resulting model had a predictive accuracy of 80%.
St. Lucia is characterised by gently sloping exposed plateaus (~30 m deep), extending for several km offshore in the north and south of the island. These appear to be mostly covered by an algal-dominated gravelly substratum. Bioturbated mud and sand with pockmarks occur typically in sheltered bays, near river mouths or within paleochannels that incise the seabed. Seagrass patches were more difficult to predict (50% producer’s accuracy) but are generally limited to very shallow coastal waters habitats. Finally, coral and sponge-dominated reef communities appear to generally be associated with raised “staircase” platforms and bommie features close to the coast, however, these were also observed further from shore and in deeper waters.
The seabed habitat maps produced will support the St. Lucian government to manage their shallow seabed resources. In particular, the maps will assist the systematic characterisation of the coral reef habitats and, therefore, improve delineations of marine reserves, especially around the town of Soufrière and the Pitons UNESCO world heritage site.
[1] Althaus, F., N. and many others. 2015. A standardised vocabulary for identifying benthic biota and substrata from underwater imagery: The CATAMI classification scheme. PLoS ONE 10:1–18.
[2] Pepper, A. and Puotinen, M. L., 2009. GREMO: A GIS-based generic model for estimating relative wave exposure. The 18th World IMACS Congress and MODSIM09 Int. Congress on Modelling and Simulation (pp. 1964-1970). Cairns, Australia.
How to cite: Arosio, R., Mitchell, P., Hawes, J., Bolam, S., Benson, L., and Sperry, J.: Small Island Developing States (SIDS) and the sea: creating high resolution habitat maps to support effective marine management in St. Lucia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-102, https://doi.org/10.5194/egusphere-egu21-102, 2021.
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This study, conducted under the auspices of the Commonwealth Marine Economies Programme (CMEP), involved the characterisation of geomorphology and benthic assemblage groups around the previously unmapped western St. Lucian coastline. A high-resolution (2 x 2 m) seabed map was then produced, specifically focussing on the economically important regions.
Two hundred twelve video tow transects were acquired by CEFAS and associated to Multibeam echosounder (MBES) data collected by the United Kingdom Hydrographic Office (UKHO). Through object-based image analysis, MBES data and derivatives were categorized into eight basic morphological classes (e.g. slope, flat), with manual intervention required to further discriminate more complex forms (e.g. anthropogenic scours). Percentage coverage of epibenthic biota and substrate type data were extracted from still seabed images using the CATAMI[1] morphological classification system and a randomised point count approach. Benthic community assemblages were then defined based on K-means clustering. A random forest model was used to predict benthic community groups. Predictive layers included MBES-derived physical properties, geomorphological classes and wave exposure (using GREMO[2]). The resulting model had a predictive accuracy of 80%.
St. Lucia is characterised by gently sloping exposed plateaus (~30 m deep), extending for several km offshore in the north and south of the island. These appear to be mostly covered by an algal-dominated gravelly substratum. Bioturbated mud and sand with pockmarks occur typically in sheltered bays, near river mouths or within paleochannels that incise the seabed. Seagrass patches were more difficult to predict (50% producer’s accuracy) but are generally limited to very shallow coastal waters habitats. Finally, coral and sponge-dominated reef communities appear to generally be associated with raised “staircase” platforms and bommie features close to the coast, however, these were also observed further from shore and in deeper waters.
The seabed habitat maps produced will support the St. Lucian government to manage their shallow seabed resources. In particular, the maps will assist the systematic characterisation of the coral reef habitats and, therefore, improve delineations of marine reserves, especially around the town of Soufrière and the Pitons UNESCO world heritage site.
[1] Althaus, F., N. and many others. 2015. A standardised vocabulary for identifying benthic biota and substrata from underwater imagery: The CATAMI classification scheme. PLoS ONE 10:1–18.
[2] Pepper, A. and Puotinen, M. L., 2009. GREMO: A GIS-based generic model for estimating relative wave exposure. The 18th World IMACS Congress and MODSIM09 Int. Congress on Modelling and Simulation (pp. 1964-1970). Cairns, Australia.
How to cite: Arosio, R., Mitchell, P., Hawes, J., Bolam, S., Benson, L., and Sperry, J.: Small Island Developing States (SIDS) and the sea: creating high resolution habitat maps to support effective marine management in St. Lucia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-102, https://doi.org/10.5194/egusphere-egu21-102, 2021.
EGU21-11688 | vPICO presentations | GM6.8
Seafloor sediment classification of the Sylt Outer Reef, German Bight from 2016 -2018 using ensemble modellingDaphnie Galvez, Svenja Papenmeier, Alexander Bartholomä, and Karen Helen Wiltshire
Recent studies on seafloor mapping have presented different modelling methods to map and classify marine sediment distribution. However, are these methods classify different sediment classes the same way? And how do we choose the right model for a certain set of sediment classes? In this study, we aim to address these issues by using ensemble modelling to map the distribution of different sediment class on a dynamic, shallow continental shelf. Our data were derived from side-scan mosaics and multibeam data repeatedly collected from 2016 to 2018 in the Sylt Outer Reef (German Bight). We used a probabilistic approach for each class separately and then compared the predicted probability for each class, to see which class is more likely to be assigned to the location. Each sediment class was predicted using a combination of different classification modelling techniques, and then the result of these models was ensembled to produced one final prediction. This approach avoids selecting one single method, limits model selection bias and can provide information on the trends and variation across models. Furthermore, we also looked on the temporal changes in sediment distributions by comparing the sediment class predictions from 2016 to 2018.
Our analysis suggest that combining different modelling techniques (i.e. random forest, boosting regression trees etc.) provide higher predictive accuracy than using one single modelling method. The resulting sediment distribution maps are more objective and are produced faster than manual delineated maps often considered by stakeholders. We also identify some limitations in having small sample size and we proposed that by combining certain models and choosing the proper amount of pseudo-absence or background data can address this issue.
How to cite: Galvez, D., Papenmeier, S., Bartholomä, A., and Wiltshire, K. H.: Seafloor sediment classification of the Sylt Outer Reef, German Bight from 2016 -2018 using ensemble modelling , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11688, https://doi.org/10.5194/egusphere-egu21-11688, 2021.
Please decide on your access
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Recent studies on seafloor mapping have presented different modelling methods to map and classify marine sediment distribution. However, are these methods classify different sediment classes the same way? And how do we choose the right model for a certain set of sediment classes? In this study, we aim to address these issues by using ensemble modelling to map the distribution of different sediment class on a dynamic, shallow continental shelf. Our data were derived from side-scan mosaics and multibeam data repeatedly collected from 2016 to 2018 in the Sylt Outer Reef (German Bight). We used a probabilistic approach for each class separately and then compared the predicted probability for each class, to see which class is more likely to be assigned to the location. Each sediment class was predicted using a combination of different classification modelling techniques, and then the result of these models was ensembled to produced one final prediction. This approach avoids selecting one single method, limits model selection bias and can provide information on the trends and variation across models. Furthermore, we also looked on the temporal changes in sediment distributions by comparing the sediment class predictions from 2016 to 2018.
Our analysis suggest that combining different modelling techniques (i.e. random forest, boosting regression trees etc.) provide higher predictive accuracy than using one single modelling method. The resulting sediment distribution maps are more objective and are produced faster than manual delineated maps often considered by stakeholders. We also identify some limitations in having small sample size and we proposed that by combining certain models and choosing the proper amount of pseudo-absence or background data can address this issue.
How to cite: Galvez, D., Papenmeier, S., Bartholomä, A., and Wiltshire, K. H.: Seafloor sediment classification of the Sylt Outer Reef, German Bight from 2016 -2018 using ensemble modelling , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11688, https://doi.org/10.5194/egusphere-egu21-11688, 2021.
EGU21-10854 | vPICO presentations | GM6.8
Sediments and bedform mapping of the Lower Saxony Wadden Sea and North Sea (Germany)Francesco Mascioli and Tina Kunde
Seafloor mapping is the subject of several worldwide research programs dealing with the growing awareness that changes of the marine environmental conditions have to be accurately monitored. The monitoring requirements strongly stimulate the scientific interest in innovative mapping methods and tools, which should be exploitable within the extensive mapping programs carried out by governmental agencies and institutes.
The Coastal Research Station within the NLWKN is carrying out a long-term program to map subtidal areas of the Lower Saxony coastal and marine waters, adopting a methodological approach aimed to increase objectivity and repeatability of results.
The study area is one of the world’s largest tidal system encompassing a multitude of transitional zones between land, marine, and estuarine environments. The geological and geomorphological setting is closely related to the Late Quaternary evolution of the North Sea and the actual morphodynamic processes. The seabed is made of Holocene sand to silt deposits and peat layers. They overlay Pleistocene fluvioglacial deposits, made of sands, rocks, and boulders, which locally outcrop in small areas of the North Sea and in the deepest sectors of the Wadden Sea tidal inlets.
Even though existing maps provide a good broad-scaled representation of the sediments distribution, they were produced by the interpolation of grab-samples therefore lacking of spatial resolution and bedforms characterization. The ongoing mapping program provides full-coverage detailed sedimentological and geomorphological data, by means of swath-bathymetrical systems, subbottom profiler, and validation samples. The methodological approach integrates bathymetric, backscatter, and stratigraphic information to characterize bedforms and substrates. Bathymetry and seabed images are interpreted using geomorphometric as well as object-based image analysis, to increase the objectivity and generate reproducible results.
Maps outline common sedimentological and geomorphological features across all the observed Wadden Sea tidal inlets, which are made of fine sandy sediments and narrow outcrops of peat layers on the main tidal channels slopes. Both erosive and depositional geomorphological processes are present, represented by several orders of scarps, mainly connected to alternations of hard-substrates and unconsolidated sands, and medium to very large sand waves. Moreover, data reveal high-resolution information about hard-substrate outcrops in the North Sea area.
The mapping program provides new detailed geological-geomorphological features of a very dynamic coastal area, using repeatable and objective methods. The combination of different datasets and tools allows the quantitative analysis of the complex subtidal morphology, the correlation of bedforms and substrates. Resulting products will be further developed for habitat mapping purposes and morphological and hydro-dynamical modelling.
How to cite: Mascioli, F. and Kunde, T.: Sediments and bedform mapping of the Lower Saxony Wadden Sea and North Sea (Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10854, https://doi.org/10.5194/egusphere-egu21-10854, 2021.
Seafloor mapping is the subject of several worldwide research programs dealing with the growing awareness that changes of the marine environmental conditions have to be accurately monitored. The monitoring requirements strongly stimulate the scientific interest in innovative mapping methods and tools, which should be exploitable within the extensive mapping programs carried out by governmental agencies and institutes.
The Coastal Research Station within the NLWKN is carrying out a long-term program to map subtidal areas of the Lower Saxony coastal and marine waters, adopting a methodological approach aimed to increase objectivity and repeatability of results.
The study area is one of the world’s largest tidal system encompassing a multitude of transitional zones between land, marine, and estuarine environments. The geological and geomorphological setting is closely related to the Late Quaternary evolution of the North Sea and the actual morphodynamic processes. The seabed is made of Holocene sand to silt deposits and peat layers. They overlay Pleistocene fluvioglacial deposits, made of sands, rocks, and boulders, which locally outcrop in small areas of the North Sea and in the deepest sectors of the Wadden Sea tidal inlets.
Even though existing maps provide a good broad-scaled representation of the sediments distribution, they were produced by the interpolation of grab-samples therefore lacking of spatial resolution and bedforms characterization. The ongoing mapping program provides full-coverage detailed sedimentological and geomorphological data, by means of swath-bathymetrical systems, subbottom profiler, and validation samples. The methodological approach integrates bathymetric, backscatter, and stratigraphic information to characterize bedforms and substrates. Bathymetry and seabed images are interpreted using geomorphometric as well as object-based image analysis, to increase the objectivity and generate reproducible results.
Maps outline common sedimentological and geomorphological features across all the observed Wadden Sea tidal inlets, which are made of fine sandy sediments and narrow outcrops of peat layers on the main tidal channels slopes. Both erosive and depositional geomorphological processes are present, represented by several orders of scarps, mainly connected to alternations of hard-substrates and unconsolidated sands, and medium to very large sand waves. Moreover, data reveal high-resolution information about hard-substrate outcrops in the North Sea area.
The mapping program provides new detailed geological-geomorphological features of a very dynamic coastal area, using repeatable and objective methods. The combination of different datasets and tools allows the quantitative analysis of the complex subtidal morphology, the correlation of bedforms and substrates. Resulting products will be further developed for habitat mapping purposes and morphological and hydro-dynamical modelling.
How to cite: Mascioli, F. and Kunde, T.: Sediments and bedform mapping of the Lower Saxony Wadden Sea and North Sea (Germany), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10854, https://doi.org/10.5194/egusphere-egu21-10854, 2021.
EGU21-6695 | vPICO presentations | GM6.8
Integrating Seafloor Mapping Data with Sediment Transport and Coastal Change Studies: Preliminary Results from the Southern Gulf of Maine, USALaura Brothers, Seth Ackerman, David Foster, Brian Andrews, John Warner, Emily Himmelstoss, William Danforth, and Emily Huntley
Coastal erosion, intense storm events and sea-level rise pose threats to coastal communities and infrastructure. Managers and scientists often lack the high-resolution data needed to improve estimates of sediment abundance and movement, shoreline change, substrate heterogeneity and other seabed characteristics that influence coastal vulnerability. To address these and other needs the U.S. Geological Survey is conducting a multi-tiered research initiative consisting of shoreline change characterization, sediment transport numerical modeling and seafloor mapping in Cape Cod Bay, Massachusetts, USA. Here we present the seafloor mapping findings and their applications to an integrated coastal change analysis. Our comprehensive seafloor mapping technique includes the collection of multibeam and phase-discriminating data, seismic-reflection profile data, sediment samples, seabed imagery, as well as the synthesis of regional legacy datasets. A first-order comparison of the interdisciplinary results indicates that the presence of seafloor bedforms and the thickness of Late Holocene sediments correspond to patterns of modeled seabed elevation change and observed relative coastline stability. Analyses of these data are ongoing and may further resolve the relationships among shoreline change, nearshore processes and antecedent geology.
How to cite: Brothers, L., Ackerman, S., Foster, D., Andrews, B., Warner, J., Himmelstoss, E., Danforth, W., and Huntley, E.: Integrating Seafloor Mapping Data with Sediment Transport and Coastal Change Studies: Preliminary Results from the Southern Gulf of Maine, USA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6695, https://doi.org/10.5194/egusphere-egu21-6695, 2021.
Coastal erosion, intense storm events and sea-level rise pose threats to coastal communities and infrastructure. Managers and scientists often lack the high-resolution data needed to improve estimates of sediment abundance and movement, shoreline change, substrate heterogeneity and other seabed characteristics that influence coastal vulnerability. To address these and other needs the U.S. Geological Survey is conducting a multi-tiered research initiative consisting of shoreline change characterization, sediment transport numerical modeling and seafloor mapping in Cape Cod Bay, Massachusetts, USA. Here we present the seafloor mapping findings and their applications to an integrated coastal change analysis. Our comprehensive seafloor mapping technique includes the collection of multibeam and phase-discriminating data, seismic-reflection profile data, sediment samples, seabed imagery, as well as the synthesis of regional legacy datasets. A first-order comparison of the interdisciplinary results indicates that the presence of seafloor bedforms and the thickness of Late Holocene sediments correspond to patterns of modeled seabed elevation change and observed relative coastline stability. Analyses of these data are ongoing and may further resolve the relationships among shoreline change, nearshore processes and antecedent geology.
How to cite: Brothers, L., Ackerman, S., Foster, D., Andrews, B., Warner, J., Himmelstoss, E., Danforth, W., and Huntley, E.: Integrating Seafloor Mapping Data with Sediment Transport and Coastal Change Studies: Preliminary Results from the Southern Gulf of Maine, USA, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6695, https://doi.org/10.5194/egusphere-egu21-6695, 2021.
EGU21-6257 | vPICO presentations | GM6.8
Monitoring sediment transport and grain size dynamics along the Israeli continental shelf with multibeam bathymetry and backscatter dataAsaf Giladi, Mor Kanari, Timor katz, and Gideon Tibor
In 2017, the Israel Oceanographic and Limnological Research (IOLR) started an annual seafloor monitoring program. The aim of the program is to evaluate the rate of erosion/deposition and the influence of man-made infrastructures on the seabed along the Israeli continental shelf south of Akko. The survey program onboard R/V Bat-Galim includes a multibeam (Kongsberg EM2040), sub-bottom (Knudsen 3260 Chirp) mapping and box-core sediment sampling along 13 transects across the shelf, from WD 10-100 m. The multibeam was operated at 400-kHz yielding a horizontal resolution of 0.25-1.0 m (depending on water depth), and vertical uncertainty of several centimeters. Using the QPS FMGT software, both angular response curves (ARA) and 0.5 m horizontal resolution of Backscatter data (BS) were derived. The multibeam acoustic return intensities (BS) were locally calibrated at selected reference areas using in-situ sediment sampling.
The main source of sediments along the Israeli continental shelf is the Nile Delta which undergoes erosion since 1960 when the Aswan dam was constructed. Along the Israeli inner-shelf, these sediments are transported northward and westward by wind-derived currents and storms. The analysis of the bathymetric surfaces from the consecutive years 2017-2020 shows that the shelf is stable in terms of sediment processes except along the marine infrastructures and natural seafloor features (e.g. rocky bottom outcrops) where patterns of sediment accumulation and erosion are observed. The variability along the marine infrastructures is mostly seen in the shallow water (less than 30 m) where yearly changes of up to +/-0.4 m of sediment accumulation/erosion in the vertical axis were measured.
The locally calibrated multibeam BS enabled grain size mode evaluation ranging from very fine gravel (-1 phi) to clay (9 phi). Additional in-situ sampling validated the reliability of the grain size classification method for the Israeli, continental shelf. Accordingly, we show that the Israeli continental shelf south of Haifa Bay is characterized by a sandy seafloor strip at WD 0-35 m and a muddy strip that extends west up to WD 100 m (in agreement with previous studies). Gravelly areas are identified at the coast-parallel Kurkar outcrops (Calcareous sandstone rocky ridges or rock patches) in water depths of 10-15m and 35-40m and in some places even at WD of 90 m. This demonstrates that grain size classification by locally calibrated multibeam BS is likely to be a very useful and fast method for monitoring changes in seafloor characteristics over large areas over time.
How to cite: Giladi, A., Kanari, M., katz, T., and Tibor, G.: Monitoring sediment transport and grain size dynamics along the Israeli continental shelf with multibeam bathymetry and backscatter data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6257, https://doi.org/10.5194/egusphere-egu21-6257, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
In 2017, the Israel Oceanographic and Limnological Research (IOLR) started an annual seafloor monitoring program. The aim of the program is to evaluate the rate of erosion/deposition and the influence of man-made infrastructures on the seabed along the Israeli continental shelf south of Akko. The survey program onboard R/V Bat-Galim includes a multibeam (Kongsberg EM2040), sub-bottom (Knudsen 3260 Chirp) mapping and box-core sediment sampling along 13 transects across the shelf, from WD 10-100 m. The multibeam was operated at 400-kHz yielding a horizontal resolution of 0.25-1.0 m (depending on water depth), and vertical uncertainty of several centimeters. Using the QPS FMGT software, both angular response curves (ARA) and 0.5 m horizontal resolution of Backscatter data (BS) were derived. The multibeam acoustic return intensities (BS) were locally calibrated at selected reference areas using in-situ sediment sampling.
The main source of sediments along the Israeli continental shelf is the Nile Delta which undergoes erosion since 1960 when the Aswan dam was constructed. Along the Israeli inner-shelf, these sediments are transported northward and westward by wind-derived currents and storms. The analysis of the bathymetric surfaces from the consecutive years 2017-2020 shows that the shelf is stable in terms of sediment processes except along the marine infrastructures and natural seafloor features (e.g. rocky bottom outcrops) where patterns of sediment accumulation and erosion are observed. The variability along the marine infrastructures is mostly seen in the shallow water (less than 30 m) where yearly changes of up to +/-0.4 m of sediment accumulation/erosion in the vertical axis were measured.
The locally calibrated multibeam BS enabled grain size mode evaluation ranging from very fine gravel (-1 phi) to clay (9 phi). Additional in-situ sampling validated the reliability of the grain size classification method for the Israeli, continental shelf. Accordingly, we show that the Israeli continental shelf south of Haifa Bay is characterized by a sandy seafloor strip at WD 0-35 m and a muddy strip that extends west up to WD 100 m (in agreement with previous studies). Gravelly areas are identified at the coast-parallel Kurkar outcrops (Calcareous sandstone rocky ridges or rock patches) in water depths of 10-15m and 35-40m and in some places even at WD of 90 m. This demonstrates that grain size classification by locally calibrated multibeam BS is likely to be a very useful and fast method for monitoring changes in seafloor characteristics over large areas over time.
How to cite: Giladi, A., Kanari, M., katz, T., and Tibor, G.: Monitoring sediment transport and grain size dynamics along the Israeli continental shelf with multibeam bathymetry and backscatter data , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6257, https://doi.org/10.5194/egusphere-egu21-6257, 2021.
EGU21-15523 | vPICO presentations | GM6.8
Uncrewed bathymetric survey in UK waters: Testing CARIS Mira AI and globally-distributed Nippon Foundation/ GEBCO training program Alumni to produce data productsDanai Lampridou, Kemron Beache, Aileen Bohan, Mohamed Elsaied, Travis Hamilton, Andy Hoggarth, Jaya Roperez, Karolina Zwolak, Ana Carolina Lavagnino, Tinah Martin, Victoria Obura, Seeboruth Sattiabaruth, Neil Tinmouth, and Rochelle Wigley
SEA-KIT USV Maxlimer successfully carried out a 22 day (24hrs per day), uncrewed survey operation offshore the United Kingdom in July-August 2020. The uncrewed vessel was controlled and manoeuvred from an operation room based in Essex, UK, while the data acquisition was performed by alumni of the Nippon Foundation/GEBCO Training Program, through the Map the Gaps NPO, spread across 10 countries. One of the main objectives of the trans-ocean survey was to test the remote survey capabilities through satellite communications, and also promote the contribution to seafloor mapping. CARIS Onboard, incorporating the new Sonar Noise Classifier tool via the CARIS Mira AI platform, was deployed to autonomously process the survey data in real-time, and provide products that could be streamed daily from SEA-KIT to ensure operations were successful and to help train the classifier as required. The data was post-processed with CARIS HIPS and SIPS using conventional and Ai techniques, and gridded at 10 m. The collected data size was 52.2 GB, surveyed area depth range from 57m to 1362 with 470m mean depth and around 900 km2 was totally covered. CARIS Mira AI with traditional QC approach reduced data processing time to 77% regarding the conventional path.
The high-resolution bathymetric dataset provided the first detailed picture of the Brenot Spur, adjacent to Dangeart Canyon. Three major submarine canyon systems can be identified, cross-cutting the continental shelf nearly perpendicularly. The main axis of the first canyon, located at the far northern part of the surveyed area, is oriented NE-SW and becomes wider downstream. Both of the flanks are highly carved by gullies and tributaries, especially along the northern flank, where a complex system is developed depicting well-developed amphitheatric heads, indicating retrogressive erosion. Moreover, this network shows a high degree of incision and narrow interfluves. The second major canyon trends ENE-WSW and is a multi-fed system consisting of three sub-canyons that coalesce at 1095 m water depth. Although tributaries bisect the flanks of this system, they are not mature and have not yet breached the continental shelf, but are mostly confined on the slope. The final canyon is narrower than the previous ones and its thalweg is nearly N-S oriented. Additionally, the flanks of the later differ substantially when it comes to their morphology. The western flank is undulated by linear wall gullies and several landslides indicated by the crescent like rim of high slope values, while the eastern flank is smooth and featureless. Along the SW continental slope, evidence for several old landslide events can be identified. The major failure scars are located right at the edge of the shelf at 560 m water depth.
How to cite: Lampridou, D., Beache, K., Bohan, A., Elsaied, M., Hamilton, T., Hoggarth, A., Roperez, J., Zwolak, K., Lavagnino, A. C., Martin, T., Obura, V., Sattiabaruth, S., Tinmouth, N., and Wigley, R.: Uncrewed bathymetric survey in UK waters: Testing CARIS Mira AI and globally-distributed Nippon Foundation/ GEBCO training program Alumni to produce data products, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15523, https://doi.org/10.5194/egusphere-egu21-15523, 2021.
SEA-KIT USV Maxlimer successfully carried out a 22 day (24hrs per day), uncrewed survey operation offshore the United Kingdom in July-August 2020. The uncrewed vessel was controlled and manoeuvred from an operation room based in Essex, UK, while the data acquisition was performed by alumni of the Nippon Foundation/GEBCO Training Program, through the Map the Gaps NPO, spread across 10 countries. One of the main objectives of the trans-ocean survey was to test the remote survey capabilities through satellite communications, and also promote the contribution to seafloor mapping. CARIS Onboard, incorporating the new Sonar Noise Classifier tool via the CARIS Mira AI platform, was deployed to autonomously process the survey data in real-time, and provide products that could be streamed daily from SEA-KIT to ensure operations were successful and to help train the classifier as required. The data was post-processed with CARIS HIPS and SIPS using conventional and Ai techniques, and gridded at 10 m. The collected data size was 52.2 GB, surveyed area depth range from 57m to 1362 with 470m mean depth and around 900 km2 was totally covered. CARIS Mira AI with traditional QC approach reduced data processing time to 77% regarding the conventional path.
The high-resolution bathymetric dataset provided the first detailed picture of the Brenot Spur, adjacent to Dangeart Canyon. Three major submarine canyon systems can be identified, cross-cutting the continental shelf nearly perpendicularly. The main axis of the first canyon, located at the far northern part of the surveyed area, is oriented NE-SW and becomes wider downstream. Both of the flanks are highly carved by gullies and tributaries, especially along the northern flank, where a complex system is developed depicting well-developed amphitheatric heads, indicating retrogressive erosion. Moreover, this network shows a high degree of incision and narrow interfluves. The second major canyon trends ENE-WSW and is a multi-fed system consisting of three sub-canyons that coalesce at 1095 m water depth. Although tributaries bisect the flanks of this system, they are not mature and have not yet breached the continental shelf, but are mostly confined on the slope. The final canyon is narrower than the previous ones and its thalweg is nearly N-S oriented. Additionally, the flanks of the later differ substantially when it comes to their morphology. The western flank is undulated by linear wall gullies and several landslides indicated by the crescent like rim of high slope values, while the eastern flank is smooth and featureless. Along the SW continental slope, evidence for several old landslide events can be identified. The major failure scars are located right at the edge of the shelf at 560 m water depth.
How to cite: Lampridou, D., Beache, K., Bohan, A., Elsaied, M., Hamilton, T., Hoggarth, A., Roperez, J., Zwolak, K., Lavagnino, A. C., Martin, T., Obura, V., Sattiabaruth, S., Tinmouth, N., and Wigley, R.: Uncrewed bathymetric survey in UK waters: Testing CARIS Mira AI and globally-distributed Nippon Foundation/ GEBCO training program Alumni to produce data products, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15523, https://doi.org/10.5194/egusphere-egu21-15523, 2021.
EGU21-3939 | vPICO presentations | GM6.8
Interferometric Synthetic Aperture Sonar as a tool for seafloor geological mapping on the Grand Banks offshore Atlantic Canada: preliminary results.Caroline Gini, Katleen Robert, John Jamieson, and Jeremy Dillon
With less than 20% of the seafloor mapped at a sufficiently high resolution for geological and biological studies (<50m), there is a need for new technological approaches to map and characterize the seafloor environment at higher resolutions. Here, we present preliminary results of an investigation into the use of interferometric synthetic aperture sonar (InSAS) as a new approach to help fill this gap. InSAS can provide very high-resolution acoustic imagery (3cm/pixel) and bathymetry (25 cm/pixel) as well as large coverage area (up to 150m across track per side while flying at a 15m altitude, at 6 knots). Compared to traditional sidescan sonars, high-resolution imagery in both along and across track directions is achieved by the synthetic aperture of the sonar array, which uses a large number of receiver arrays and a cm-size spacing between individual elements. This technique has so far mostly been used for military and industrial purposes.
Onboard the Atlantic Kingfisher in October 2020, we used Kraken Robotic Systems’ InSAS system on a Katfish towed vehicle to survey 85 km2 of the Tail of the Grand Banks, the southernmost extremity of the continental shelf offshore Newfoundland, Canada. During a survey, the sonar is set at a center frequency of 337 kHz and survey planning included data coverage overlap for 140% coverage of the seafloor. Kraken Robotic’s processing algorithm and the towing optic cable allowed for real-time processing of the data and initial post processing using Caris Onboard.
How to cite: Gini, C., Robert, K., Jamieson, J., and Dillon, J.: Interferometric Synthetic Aperture Sonar as a tool for seafloor geological mapping on the Grand Banks offshore Atlantic Canada: preliminary results., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3939, https://doi.org/10.5194/egusphere-egu21-3939, 2021.
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With less than 20% of the seafloor mapped at a sufficiently high resolution for geological and biological studies (<50m), there is a need for new technological approaches to map and characterize the seafloor environment at higher resolutions. Here, we present preliminary results of an investigation into the use of interferometric synthetic aperture sonar (InSAS) as a new approach to help fill this gap. InSAS can provide very high-resolution acoustic imagery (3cm/pixel) and bathymetry (25 cm/pixel) as well as large coverage area (up to 150m across track per side while flying at a 15m altitude, at 6 knots). Compared to traditional sidescan sonars, high-resolution imagery in both along and across track directions is achieved by the synthetic aperture of the sonar array, which uses a large number of receiver arrays and a cm-size spacing between individual elements. This technique has so far mostly been used for military and industrial purposes.
Onboard the Atlantic Kingfisher in October 2020, we used Kraken Robotic Systems’ InSAS system on a Katfish towed vehicle to survey 85 km2 of the Tail of the Grand Banks, the southernmost extremity of the continental shelf offshore Newfoundland, Canada. During a survey, the sonar is set at a center frequency of 337 kHz and survey planning included data coverage overlap for 140% coverage of the seafloor. Kraken Robotic’s processing algorithm and the towing optic cable allowed for real-time processing of the data and initial post processing using Caris Onboard.
How to cite: Gini, C., Robert, K., Jamieson, J., and Dillon, J.: Interferometric Synthetic Aperture Sonar as a tool for seafloor geological mapping on the Grand Banks offshore Atlantic Canada: preliminary results., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3939, https://doi.org/10.5194/egusphere-egu21-3939, 2021.
EGU21-10389 | vPICO presentations | GM6.8
Integrating multibeam echosounder water-column data into benthic habitat mappingPeter Porskamp, Alexandre Schimel, Mary Young, Alex Rattray, Yoann Ladroit, and Daniel Ierodiaconou
Kelp forests worldwide are under ever increasing pressure from anthropogenic impacts including kelp harvesting, pollution, and higher sea surface temperatures due to climate change. Marine spatial planning requires accurate mapping of these habitat types to inform effective policy. Key data needed for benthic habitat maps to inform policy are acquired by multibeam echosounders, which collect high resolution bathymetry and backscatter of the seafloor. An additional and previously little used product of high resolution MBES are mid-water backscatter data, termed water-column data, that have been used to identify and map kelp species that extended above the seafloor. We show that incorporating water-column data as a variable for modeling benthic marine habitat distributions can significantly improve the accuracy of benthic habitat maps, specifically where habitat categories include large species of macroalgae on shallow (2-34m) subtidal reefs. The study site has full coverage multibeam bathymetry, backscatter and water-column data, alongside comprehensive observation surveys of benthic habitats using towed video. All towed video observations were classified using a hierarchal marine biotope classification scheme. Water-column data were processed into a mosaic-like product representing the acoustic energy in a layer 0-1m above the seabed. This processing included filtering of the sidelobe artefact. The volumetric water-column mosaic along with bathymetric and backscatter derivatives combined with towed video observations were used as input variables in a supervised random forest classification algorithm to create habitat maps for the study site. Variable importance was assessed for all variables and water-column performed well as it was retained in all models. Including water-column data increased overall map accuracy up to 1.18% and improved producer class accuracies that contained macroalgae up to 2.95%. With increasing pressure on temperate macroalgal communities due to a synergy of pressures arising from warming oceans, our work provides a timely advance for mapping and monitoring changes.
How to cite: Porskamp, P., Schimel, A., Young, M., Rattray, A., Ladroit, Y., and Ierodiaconou, D.: Integrating multibeam echosounder water-column data into benthic habitat mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10389, https://doi.org/10.5194/egusphere-egu21-10389, 2021.
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Kelp forests worldwide are under ever increasing pressure from anthropogenic impacts including kelp harvesting, pollution, and higher sea surface temperatures due to climate change. Marine spatial planning requires accurate mapping of these habitat types to inform effective policy. Key data needed for benthic habitat maps to inform policy are acquired by multibeam echosounders, which collect high resolution bathymetry and backscatter of the seafloor. An additional and previously little used product of high resolution MBES are mid-water backscatter data, termed water-column data, that have been used to identify and map kelp species that extended above the seafloor. We show that incorporating water-column data as a variable for modeling benthic marine habitat distributions can significantly improve the accuracy of benthic habitat maps, specifically where habitat categories include large species of macroalgae on shallow (2-34m) subtidal reefs. The study site has full coverage multibeam bathymetry, backscatter and water-column data, alongside comprehensive observation surveys of benthic habitats using towed video. All towed video observations were classified using a hierarchal marine biotope classification scheme. Water-column data were processed into a mosaic-like product representing the acoustic energy in a layer 0-1m above the seabed. This processing included filtering of the sidelobe artefact. The volumetric water-column mosaic along with bathymetric and backscatter derivatives combined with towed video observations were used as input variables in a supervised random forest classification algorithm to create habitat maps for the study site. Variable importance was assessed for all variables and water-column performed well as it was retained in all models. Including water-column data increased overall map accuracy up to 1.18% and improved producer class accuracies that contained macroalgae up to 2.95%. With increasing pressure on temperate macroalgal communities due to a synergy of pressures arising from warming oceans, our work provides a timely advance for mapping and monitoring changes.
How to cite: Porskamp, P., Schimel, A., Young, M., Rattray, A., Ladroit, Y., and Ierodiaconou, D.: Integrating multibeam echosounder water-column data into benthic habitat mapping, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10389, https://doi.org/10.5194/egusphere-egu21-10389, 2021.
GM6.9 – Sinking, shrinking and saltier river deltas: processes, interactions and responses
EGU21-283 | vPICO presentations | GM6.9 | Highlight
Large deltas versus small deltas: Two different beastsJaia Syvitski
Many studies rank deltas as a continuum, as conditioned by hinterland drainage area, river discharge, sediment load, ocean energy, or even human interaction. This scaling has helped advance our understanding on how these important coastal deposits develop. From such studies, equilibrium states have been identified, such as the balance between sediment supply and the subsequent dispersal of incoming sediment. Conceptual equations are used to track the influence of changing boundary conditions such as sea level rise (or fall) that can then expose the role of anthropogenic influences such as groundwater mining. However, scaling may not reveal important differences between small-scale deltas, that globally number in the thousands, and large regional deltas that number in the dozens. For example backwater effects appear important in large delta systems but can often be ignored in many smaller delta systems with steeper fluvial gradients. Large deltas are home to large human populations and their infrastructure, but does this influence scale with delta size? This overview presentation explores the use of conceptual equations to determine if there is a limit to scaling.
How to cite: Syvitski, J.: Large deltas versus small deltas: Two different beasts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-283, https://doi.org/10.5194/egusphere-egu21-283, 2021.
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Many studies rank deltas as a continuum, as conditioned by hinterland drainage area, river discharge, sediment load, ocean energy, or even human interaction. This scaling has helped advance our understanding on how these important coastal deposits develop. From such studies, equilibrium states have been identified, such as the balance between sediment supply and the subsequent dispersal of incoming sediment. Conceptual equations are used to track the influence of changing boundary conditions such as sea level rise (or fall) that can then expose the role of anthropogenic influences such as groundwater mining. However, scaling may not reveal important differences between small-scale deltas, that globally number in the thousands, and large regional deltas that number in the dozens. For example backwater effects appear important in large delta systems but can often be ignored in many smaller delta systems with steeper fluvial gradients. Large deltas are home to large human populations and their infrastructure, but does this influence scale with delta size? This overview presentation explores the use of conceptual equations to determine if there is a limit to scaling.
How to cite: Syvitski, J.: Large deltas versus small deltas: Two different beasts, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-283, https://doi.org/10.5194/egusphere-egu21-283, 2021.
EGU21-15474 | vPICO presentations | GM6.9
Big Data-driven geomorphic analysis of the world’s river deltas: a need for caution and rigourFlorin Iulian Zăinescu and Edward Anthony
There is increasing recourse to Big Data in the geosciences as in all other spheres of research. This is an important development in the pursuit of global statistics or unifying rules on environmental change. However, the finality can only be justified if such data are rigorous and checks equally rigorous, because the objective is to derive and eventually propose reliable quantified trends or functional laws.
River deltas, a hot topic because of their exposure to hazards, increasing vulnerability and assumed loss of resilience caused by climate change and human intervention, are witnessing an upsurge of analysis based on available satellite and model data. A recent database (Nienhuis et al., 2020) comprises ~11000 identified ‘deltas‘ along with surface area changes for each delta based on Aqua Monitor (Aqua) and Global Surface Water Explorer (GSW) datasets derived from Landsat images, alongside with fluvial, wave and tidal sediment fluxes from global models and estimations. The authors claim that deltas globally have gained an area of 54 ±11.8 km2/yr over the last 30 years due partially to human interventions in drainage basins, and they attributed land loss in about 1000 deltas to recent reductions in sediment supply. However, these findings are, unfortunately, beset with flaws.
Prompted by the inventory of numerous ‘river deltas‘ in regions such as the British Isles and Britanny, France, where a Web-of-Science bibliographic check yielded no modern river deltas, we randomly selected 108 deltas from the dataset (n = 1%), checking for delta presence and obtaining change rates from manually-drawn buffers. We obtained no agreement with the original data of Nienhuis et al. (2020), and found the same disagreement when we tested the data against an already published dataset. We consider that the database of Nienhuis et al. (2020) is replete with errors that render the derived delta area changes unreliable. We raise fundamental concerns about their methodology and the criteria they use to define river mouths as deltas.
Our caveat here is that while Big Data certainly provide a way forward for the global analysis of river deltas (and other landforms), there is a need for awareness of current pitfalls in datasets and their handling. Nienhuis et al. (2020) proposed their definition of river deltas. There is indeed a need for community consensus on delta definition, but this could be a hard task. Considering just deltaic coastal change, some guidelines for rigorous analysis of data are: (i) better and more robust buffers that delineate only such change. Is this even achievable by automatic means?; and (ii) better filtering of anthropogenic modifications which, in many deltas, are dominating area change, so that new coastal reclamation projects can be more robustly detected in improved landcover databases. There is also a need for accurate datasets on water surface change. Do these exist? A comparison, for instance, of Aqua and GSW datasets on deltaic coastal change shows significant discrepancies between the two.
How to cite: Zăinescu, F. I. and Anthony, E.: Big Data-driven geomorphic analysis of the world’s river deltas: a need for caution and rigour, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15474, https://doi.org/10.5194/egusphere-egu21-15474, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
There is increasing recourse to Big Data in the geosciences as in all other spheres of research. This is an important development in the pursuit of global statistics or unifying rules on environmental change. However, the finality can only be justified if such data are rigorous and checks equally rigorous, because the objective is to derive and eventually propose reliable quantified trends or functional laws.
River deltas, a hot topic because of their exposure to hazards, increasing vulnerability and assumed loss of resilience caused by climate change and human intervention, are witnessing an upsurge of analysis based on available satellite and model data. A recent database (Nienhuis et al., 2020) comprises ~11000 identified ‘deltas‘ along with surface area changes for each delta based on Aqua Monitor (Aqua) and Global Surface Water Explorer (GSW) datasets derived from Landsat images, alongside with fluvial, wave and tidal sediment fluxes from global models and estimations. The authors claim that deltas globally have gained an area of 54 ±11.8 km2/yr over the last 30 years due partially to human interventions in drainage basins, and they attributed land loss in about 1000 deltas to recent reductions in sediment supply. However, these findings are, unfortunately, beset with flaws.
Prompted by the inventory of numerous ‘river deltas‘ in regions such as the British Isles and Britanny, France, where a Web-of-Science bibliographic check yielded no modern river deltas, we randomly selected 108 deltas from the dataset (n = 1%), checking for delta presence and obtaining change rates from manually-drawn buffers. We obtained no agreement with the original data of Nienhuis et al. (2020), and found the same disagreement when we tested the data against an already published dataset. We consider that the database of Nienhuis et al. (2020) is replete with errors that render the derived delta area changes unreliable. We raise fundamental concerns about their methodology and the criteria they use to define river mouths as deltas.
Our caveat here is that while Big Data certainly provide a way forward for the global analysis of river deltas (and other landforms), there is a need for awareness of current pitfalls in datasets and their handling. Nienhuis et al. (2020) proposed their definition of river deltas. There is indeed a need for community consensus on delta definition, but this could be a hard task. Considering just deltaic coastal change, some guidelines for rigorous analysis of data are: (i) better and more robust buffers that delineate only such change. Is this even achievable by automatic means?; and (ii) better filtering of anthropogenic modifications which, in many deltas, are dominating area change, so that new coastal reclamation projects can be more robustly detected in improved landcover databases. There is also a need for accurate datasets on water surface change. Do these exist? A comparison, for instance, of Aqua and GSW datasets on deltaic coastal change shows significant discrepancies between the two.
How to cite: Zăinescu, F. I. and Anthony, E.: Big Data-driven geomorphic analysis of the world’s river deltas: a need for caution and rigour, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15474, https://doi.org/10.5194/egusphere-egu21-15474, 2021.
EGU21-12309 | vPICO presentations | GM6.9
Decompacting Holocene deltas to quantify their (proper) weightAnita Rigoni, Philip S. J. Minderhoud, Claudia Zoccarato, and Pietro Teatini
Most of the world major deltas are threatened by relative sea level rise, i.e. land subsidence and sea level rise, caused by a combination of anthropogenic pressures and natural processes. This study focuses on the natural components of land subsidence directly and indirectly related to the Holocene delta stratigraphy. Firstly, subsidence is caused by natural compaction of the Holocene sediments following deposition over time under their own weight. Secondly, subsidence is caused by the visco-elastic deformation of the Earth crust driven by cumulative load of the Holocene delta (so-called Sediment Isostatic Adjustment). These two processes are obviously connected and call for a proper evaluation of the weight of (the Holocene portion of) a delta. This requires a proper quantification of specific weight and degree of compaction of Holocene deposits with depth to arrive at a first-order assessment of Holocene delta weight.
This study proposes an innovative methodology to address the following two questions: 1) What is the proper weight of a (Holocene) delta? 2) How much have deposits been compacted since their deposition during Holocene delta formation? Our approach integrates knowledge and data on deltaic depositional environments, stratigraphic information, geomechanical properties and other characteristics of the Holocene sequence.
The developed approach is applied to eight major deltas worldwide selected from a larger database according to the availability of lithostratigraphic and geomechanical information. The analysis is conducted at the scale of an entire delta, thus required the upscaling and interpolation of datasets generally available from a few wellbores only. Lithostratigraphic data is combined with a backwards modelling procedure to decompact the Holocene delta sequence to their decompacted thickness to provide a proper estimation of their weight, which takes into account the (computed) in-situ compaction degree. The results show a large variability in compaction and specific weight distribution for the different deltas which underscores the substantial role of natural compaction on delta evolution.
How to cite: Rigoni, A., Minderhoud, P. S. J., Zoccarato, C., and Teatini, P.: Decompacting Holocene deltas to quantify their (proper) weight, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12309, https://doi.org/10.5194/egusphere-egu21-12309, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Most of the world major deltas are threatened by relative sea level rise, i.e. land subsidence and sea level rise, caused by a combination of anthropogenic pressures and natural processes. This study focuses on the natural components of land subsidence directly and indirectly related to the Holocene delta stratigraphy. Firstly, subsidence is caused by natural compaction of the Holocene sediments following deposition over time under their own weight. Secondly, subsidence is caused by the visco-elastic deformation of the Earth crust driven by cumulative load of the Holocene delta (so-called Sediment Isostatic Adjustment). These two processes are obviously connected and call for a proper evaluation of the weight of (the Holocene portion of) a delta. This requires a proper quantification of specific weight and degree of compaction of Holocene deposits with depth to arrive at a first-order assessment of Holocene delta weight.
This study proposes an innovative methodology to address the following two questions: 1) What is the proper weight of a (Holocene) delta? 2) How much have deposits been compacted since their deposition during Holocene delta formation? Our approach integrates knowledge and data on deltaic depositional environments, stratigraphic information, geomechanical properties and other characteristics of the Holocene sequence.
The developed approach is applied to eight major deltas worldwide selected from a larger database according to the availability of lithostratigraphic and geomechanical information. The analysis is conducted at the scale of an entire delta, thus required the upscaling and interpolation of datasets generally available from a few wellbores only. Lithostratigraphic data is combined with a backwards modelling procedure to decompact the Holocene delta sequence to their decompacted thickness to provide a proper estimation of their weight, which takes into account the (computed) in-situ compaction degree. The results show a large variability in compaction and specific weight distribution for the different deltas which underscores the substantial role of natural compaction on delta evolution.
How to cite: Rigoni, A., Minderhoud, P. S. J., Zoccarato, C., and Teatini, P.: Decompacting Holocene deltas to quantify their (proper) weight, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12309, https://doi.org/10.5194/egusphere-egu21-12309, 2021.
EGU21-7931 | vPICO presentations | GM6.9
Modelling multi-fissure zones above buried rock ridges in subsiding basinsLi yueting, Pietro Teatini, Shujun Ye, Andrea Franceschini, Matteo Frigo, and Claudia Zoccarato
Aseismic earth fissures due to the excessive groundwater exploitation have caused seriously damage in many subsiding sedimentary basins worldwide. Generally, multiple fissures almost parallel to each other with equal distances are prone to develop where a compacting aquifer system overlies impermeable and/or incompressible ridges. Here, an advanced finite-element interface-elements modelling approach is employed to understand this process within unfaulted sedimentary sequences. A simplified geological setting is initially used to investigate the effect of the ridge slope on ruptures behaviors. Then, we reproduce the case of Guangming village, China. In both the proposed scenarios, the model simulates the occurrence of multi-fissures that initiate at land surface and propagate downward, as observed in the sites. The earth fissures are formed as a result of the combination of tensile stress (bending condition) and shear stress (shearing conditions) accumulation around and above the tip and the slopes of the ridge, respectively. The numerical outcomes indicate that the steeper ridge results in higher magnitude stress accumulation above the ridge tip which favors the formation of fissures with significant opening and small or null offset, but at expense of the reduction in stress accumulation area and fissure distribution. In Guangming case, the outcomes show that two ruptures started sliding and only one year later a central fissure opened and propagated down to 15-30 m depth. The simulated maximum opening and sliding of the central and side fissures, respectively, approximate 30 cm, which are almost in agreement with the observations. The numerical results prove that the proposed modeling approach is an effective way to predict and analyze multi-fissure onset and development in subsiding basins.
How to cite: yueting, L., Teatini, P., Ye, S., Franceschini, A., Frigo, M., and Zoccarato, C.: Modelling multi-fissure zones above buried rock ridges in subsiding basins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7931, https://doi.org/10.5194/egusphere-egu21-7931, 2021.
Aseismic earth fissures due to the excessive groundwater exploitation have caused seriously damage in many subsiding sedimentary basins worldwide. Generally, multiple fissures almost parallel to each other with equal distances are prone to develop where a compacting aquifer system overlies impermeable and/or incompressible ridges. Here, an advanced finite-element interface-elements modelling approach is employed to understand this process within unfaulted sedimentary sequences. A simplified geological setting is initially used to investigate the effect of the ridge slope on ruptures behaviors. Then, we reproduce the case of Guangming village, China. In both the proposed scenarios, the model simulates the occurrence of multi-fissures that initiate at land surface and propagate downward, as observed in the sites. The earth fissures are formed as a result of the combination of tensile stress (bending condition) and shear stress (shearing conditions) accumulation around and above the tip and the slopes of the ridge, respectively. The numerical outcomes indicate that the steeper ridge results in higher magnitude stress accumulation above the ridge tip which favors the formation of fissures with significant opening and small or null offset, but at expense of the reduction in stress accumulation area and fissure distribution. In Guangming case, the outcomes show that two ruptures started sliding and only one year later a central fissure opened and propagated down to 15-30 m depth. The simulated maximum opening and sliding of the central and side fissures, respectively, approximate 30 cm, which are almost in agreement with the observations. The numerical results prove that the proposed modeling approach is an effective way to predict and analyze multi-fissure onset and development in subsiding basins.
How to cite: yueting, L., Teatini, P., Ye, S., Franceschini, A., Frigo, M., and Zoccarato, C.: Modelling multi-fissure zones above buried rock ridges in subsiding basins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7931, https://doi.org/10.5194/egusphere-egu21-7931, 2021.
EGU21-13231 | vPICO presentations | GM6.9
Mechanism of salt flux transport in a tidal dynamic deltaYujuan Sun, Lucy Bricheno, and Kevin Horsburgh
The annual mean combined river discharge from the Ganges-Brahmaputra-Meghna (GBM) riverine system is 100,000 – 140,000 m3/s (EGIS 2000), draining to Bay of Bengal, covering 83% of total area of Bangladesh, and making Bangladesh delta more vulnerable to both the freshwater and the mixing with sea water. This estuarine environment varies spatially and temporally, over all multiple time scales, due to its funnel-shaped vast river networks, strong tides, and saltwater intrusion. Recent studies reported a drastic salinity increasing at the end of the dry season in the past 20 years (Murshed et al., 2019). Significant salinity intrusion appears from the Sundarbans (over 20ppt in 2015), and then extends inland, which makes salinity a key factor for changing land use and demographic migration.
We examine volume and salt flux transports at multi-river channels where the GBM drains to the Bay of Bengal, using our unstructured-grid Bangladesh-FVCOM model (Bricheno et al., 2016). This realistic simulation of the whole delta has been shown to reproduce the present-day river flow circulation, tidal dynamics, and salinity stratification.
We then summarise results from the detailed hydrodynamic numerical model into a simplified flow budget, to summarise the climate impacts on salt-intrusion in the delta. In this way, we can investigate the mechanism of salt flux transports in Bangladesh delta, and improve our understanding of the controlling processes driving salinity intrusion in this region.
How to cite: Sun, Y., Bricheno, L., and Horsburgh, K.: Mechanism of salt flux transport in a tidal dynamic delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13231, https://doi.org/10.5194/egusphere-egu21-13231, 2021.
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The annual mean combined river discharge from the Ganges-Brahmaputra-Meghna (GBM) riverine system is 100,000 – 140,000 m3/s (EGIS 2000), draining to Bay of Bengal, covering 83% of total area of Bangladesh, and making Bangladesh delta more vulnerable to both the freshwater and the mixing with sea water. This estuarine environment varies spatially and temporally, over all multiple time scales, due to its funnel-shaped vast river networks, strong tides, and saltwater intrusion. Recent studies reported a drastic salinity increasing at the end of the dry season in the past 20 years (Murshed et al., 2019). Significant salinity intrusion appears from the Sundarbans (over 20ppt in 2015), and then extends inland, which makes salinity a key factor for changing land use and demographic migration.
We examine volume and salt flux transports at multi-river channels where the GBM drains to the Bay of Bengal, using our unstructured-grid Bangladesh-FVCOM model (Bricheno et al., 2016). This realistic simulation of the whole delta has been shown to reproduce the present-day river flow circulation, tidal dynamics, and salinity stratification.
We then summarise results from the detailed hydrodynamic numerical model into a simplified flow budget, to summarise the climate impacts on salt-intrusion in the delta. In this way, we can investigate the mechanism of salt flux transports in Bangladesh delta, and improve our understanding of the controlling processes driving salinity intrusion in this region.
How to cite: Sun, Y., Bricheno, L., and Horsburgh, K.: Mechanism of salt flux transport in a tidal dynamic delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13231, https://doi.org/10.5194/egusphere-egu21-13231, 2021.
EGU21-2326 | vPICO presentations | GM6.9
Modelling the salinity response to fresh water flow and variable tidal amplitude in an idealized river deltaConstantinos Matsoukis, Laurent O. Amoudry, Lucy Bricheno, and Nicoletta Leonardi
High salinity values in deltaic regions can be detrimental for agriculture, aquaculture and human consumption. Salinity levels in river deltas could significantly increase due to sea level rise and infrastructure works such as river diversions or dam constructions. River flow and tides have a large influence on salinity concentrations and it is thus important to understand their combined role. In this paper, a 3D model is built for an idealized delta. A series of simulations is carried out to investigate salinity fields developed under the combined action of tidal amplitude and fresh water flow. Simulations are classified based on the ratio between fresh water and tidal range. Both tide influenced and river dominated cases were considered. Results emphasize the importance of tidally driven mixing which can establish fresher conditions in the delta for certain amplitudes. Tidal amplitude increase enhances the flow in the delta and enlarges the fresh water layer thickness and length. On the other hand, the maximum tidal ranges can limit significantly the fresh water volume. The spatiotemporal salinity distribution is described in terms of delta topology and network geometry. Salinity and river discharge were found to be negatively and exponentially correlated by an equation that resembles solutions of the 1D advection-diffusion equation. Large bathymetric differences between delta areas were identified to play a key role on the salinity patterns as they can modify the nature of the extracted relationships and correlations.
How to cite: Matsoukis, C., O. Amoudry, L., Bricheno, L., and Leonardi, N.: Modelling the salinity response to fresh water flow and variable tidal amplitude in an idealized river delta , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2326, https://doi.org/10.5194/egusphere-egu21-2326, 2021.
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High salinity values in deltaic regions can be detrimental for agriculture, aquaculture and human consumption. Salinity levels in river deltas could significantly increase due to sea level rise and infrastructure works such as river diversions or dam constructions. River flow and tides have a large influence on salinity concentrations and it is thus important to understand their combined role. In this paper, a 3D model is built for an idealized delta. A series of simulations is carried out to investigate salinity fields developed under the combined action of tidal amplitude and fresh water flow. Simulations are classified based on the ratio between fresh water and tidal range. Both tide influenced and river dominated cases were considered. Results emphasize the importance of tidally driven mixing which can establish fresher conditions in the delta for certain amplitudes. Tidal amplitude increase enhances the flow in the delta and enlarges the fresh water layer thickness and length. On the other hand, the maximum tidal ranges can limit significantly the fresh water volume. The spatiotemporal salinity distribution is described in terms of delta topology and network geometry. Salinity and river discharge were found to be negatively and exponentially correlated by an equation that resembles solutions of the 1D advection-diffusion equation. Large bathymetric differences between delta areas were identified to play a key role on the salinity patterns as they can modify the nature of the extracted relationships and correlations.
How to cite: Matsoukis, C., O. Amoudry, L., Bricheno, L., and Leonardi, N.: Modelling the salinity response to fresh water flow and variable tidal amplitude in an idealized river delta , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2326, https://doi.org/10.5194/egusphere-egu21-2326, 2021.
EGU21-2069 | vPICO presentations | GM6.9 | Highlight
The past and future dynamics of salt intrusion in the Mekong DeltaSepehr Eslami, Maarten van der Vegt, Philip Minderhoud, Nam Nguyen Trung, Jannis Hoch, Edwin Sutanudjaja, Dung Do Doc, Tho Tran Quang, Hal Voepel, and Marie-Noëlle Woillez
In the context of global rising temperatures, rapid urbanization and excessive demand for natural resources (e.g., freshwater and sand) stress the livelihood of the world deltas. Sea Level Rise, land subsidence, discharge anomalies, floods, drought, and salt intrusion are common challenges facing these ecologically essential and economically crucial coastal landscapes. Climate change projections in deltas regularly isolate climate-driven stressors and disregard anthropogenic environmental drivers. This often leads to insufficient socio-political drive at times when the short window of opportunity to save the world’s largest deltas is closing. Here, by integrating both climatic and anthropogenic drivers of exposure and vulnerability, we project salt intrusion within the Mekong mega-Delta for the next three decades. Leveraging modern numerical codes and computation capacity, by applying a high-resolution 3D model we capture the 3D dynamics of saline water intrusion, and by covering the entire delta (from 400 km upstream to 70 km offshore) we eliminate/minimize the boundary effects at the areas of interest. We differentiate the relative effects of various drivers and demonstrate that while sea level rise can increase areas affected by salinity by 5-19%, anthropogenic drivers such as extraction-induced subsidence and riverbed level incisions due to sediment starvation can further amplify that by additional 10-27%. The results are crucial input for climate adaptation policy development in the Mekong Delta and provides a blueprint for systemic assessment of environmental changes and developing environmental pathways at scale of a delta.
How to cite: Eslami, S., van der Vegt, M., Minderhoud, P., Nguyen Trung, N., Hoch, J., Sutanudjaja, E., Do Doc, D., Tran Quang, T., Voepel, H., and Woillez, M.-N.: The past and future dynamics of salt intrusion in the Mekong Delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2069, https://doi.org/10.5194/egusphere-egu21-2069, 2021.
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In the context of global rising temperatures, rapid urbanization and excessive demand for natural resources (e.g., freshwater and sand) stress the livelihood of the world deltas. Sea Level Rise, land subsidence, discharge anomalies, floods, drought, and salt intrusion are common challenges facing these ecologically essential and economically crucial coastal landscapes. Climate change projections in deltas regularly isolate climate-driven stressors and disregard anthropogenic environmental drivers. This often leads to insufficient socio-political drive at times when the short window of opportunity to save the world’s largest deltas is closing. Here, by integrating both climatic and anthropogenic drivers of exposure and vulnerability, we project salt intrusion within the Mekong mega-Delta for the next three decades. Leveraging modern numerical codes and computation capacity, by applying a high-resolution 3D model we capture the 3D dynamics of saline water intrusion, and by covering the entire delta (from 400 km upstream to 70 km offshore) we eliminate/minimize the boundary effects at the areas of interest. We differentiate the relative effects of various drivers and demonstrate that while sea level rise can increase areas affected by salinity by 5-19%, anthropogenic drivers such as extraction-induced subsidence and riverbed level incisions due to sediment starvation can further amplify that by additional 10-27%. The results are crucial input for climate adaptation policy development in the Mekong Delta and provides a blueprint for systemic assessment of environmental changes and developing environmental pathways at scale of a delta.
How to cite: Eslami, S., van der Vegt, M., Minderhoud, P., Nguyen Trung, N., Hoch, J., Sutanudjaja, E., Do Doc, D., Tran Quang, T., Voepel, H., and Woillez, M.-N.: The past and future dynamics of salt intrusion in the Mekong Delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2069, https://doi.org/10.5194/egusphere-egu21-2069, 2021.
EGU21-16509 | vPICO presentations | GM6.9 | Highlight
Robust multi-scale strategies for increasing the resilience of the Mekong DeltaRafael Schmitt, Matteo Giuliani, Simone Bizzi, Mathias Kondolf, Gretchen Daily, and Andrea Castelletti
Rising sea levels, accelerated land subsidence, and changes in water and sediment supply from upstream basins put the major livelihoods and agriculture in global river deltas at risk. Identifying effective and robust strategies to make deltas more resilient will require to systematically address uncertainty while consider the coupling between global, basin and delta scale processes.
Here, we demonstrate a bottom-up exploratory approach to forecast land loss in the Mekong Delta by 2100 and to identify most effective management levers to fight that land loss through management on different scales. To our knowledge, this is the first time that such a robust approach is applied to study coupled delta and basin systems, thus considering the full range of drivers behind land loss and delta degradation.
For this analysis, we couple a network-scale river sediment model and a conceptual model of delta morpho-dynamics. Our land loss estimates cover a large range (20 – 90 %), driven mostly by uncertainty about accelerated subsidence from groundwater pumping. However, sediment supply from the basin plays an important role to maintain delta land, especially for low and moderate scenarios of accelerated subsidence. However, sediment supply from the basin is a function of counteracting and uncertain processes. Population growth and agriculture expansion are expected to increase erosion and sediment yield from the basin, but most of this increased sediment load will be trapped in existing and planned hydropower dams, ultimately reducing sediment delivery to the delta as a function of dam siting and design.
Using more than 2 million Monte Carlo runs of a river sediment model, we find that placement of hydropower dams is the dominant control on sediment supply, far outweighing increases in sediment yield due to land conversion or reduced sediment trapping in dams because of better sediment management. Thus, the future of the Mekong delta will be determined by renewable energy policies in the basin that strategically avoid excessive sediment trapping in dams as well as by effective water management in the delta.
Our results demonstrate (1) the need for connecting delta and basin scales for managing river deltas world-wide, (2) the contribution of basin-scale sediment management to maximize the resilience of delta land, and (3) the crucial control that dams and reservoirs exert on sediment continuity between rivers and deltas.
How to cite: Schmitt, R., Giuliani, M., Bizzi, S., Kondolf, M., Daily, G., and Castelletti, A.: Robust multi-scale strategies for increasing the resilience of the Mekong Delta , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16509, https://doi.org/10.5194/egusphere-egu21-16509, 2021.
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Rising sea levels, accelerated land subsidence, and changes in water and sediment supply from upstream basins put the major livelihoods and agriculture in global river deltas at risk. Identifying effective and robust strategies to make deltas more resilient will require to systematically address uncertainty while consider the coupling between global, basin and delta scale processes.
Here, we demonstrate a bottom-up exploratory approach to forecast land loss in the Mekong Delta by 2100 and to identify most effective management levers to fight that land loss through management on different scales. To our knowledge, this is the first time that such a robust approach is applied to study coupled delta and basin systems, thus considering the full range of drivers behind land loss and delta degradation.
For this analysis, we couple a network-scale river sediment model and a conceptual model of delta morpho-dynamics. Our land loss estimates cover a large range (20 – 90 %), driven mostly by uncertainty about accelerated subsidence from groundwater pumping. However, sediment supply from the basin plays an important role to maintain delta land, especially for low and moderate scenarios of accelerated subsidence. However, sediment supply from the basin is a function of counteracting and uncertain processes. Population growth and agriculture expansion are expected to increase erosion and sediment yield from the basin, but most of this increased sediment load will be trapped in existing and planned hydropower dams, ultimately reducing sediment delivery to the delta as a function of dam siting and design.
Using more than 2 million Monte Carlo runs of a river sediment model, we find that placement of hydropower dams is the dominant control on sediment supply, far outweighing increases in sediment yield due to land conversion or reduced sediment trapping in dams because of better sediment management. Thus, the future of the Mekong delta will be determined by renewable energy policies in the basin that strategically avoid excessive sediment trapping in dams as well as by effective water management in the delta.
Our results demonstrate (1) the need for connecting delta and basin scales for managing river deltas world-wide, (2) the contribution of basin-scale sediment management to maximize the resilience of delta land, and (3) the crucial control that dams and reservoirs exert on sediment continuity between rivers and deltas.
How to cite: Schmitt, R., Giuliani, M., Bizzi, S., Kondolf, M., Daily, G., and Castelletti, A.: Robust multi-scale strategies for increasing the resilience of the Mekong Delta , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16509, https://doi.org/10.5194/egusphere-egu21-16509, 2021.
EGU21-6562 | vPICO presentations | GM6.9
Recent measurements of subsidence in the Ganges-Brahmaputra Delta, BangladeshMichael S. Steckler, Bar Oryan, Md. Hasnat Jaman, Dhiman R. Mondal, Céline Grall, Carol A. Wilson, S. Humayun Akhter, Scott DeWolf, and Steven L. Goodbred
Deltas, the low-lying land at rivers mouths, are sensitive to the delicate balance between sea level rise, land subsidence and sedimentation. Bangladesh and the Ganges-Brahmaputra Delta (GBD) have been highlighted as a region at risk from sea level rise, but reliable estimates of land subsidence have been limited. While early studies in the GBD suggested high rates of relative sea level rise, recent papers estimate more modest rates. Our objective is to better quantify the magnitude, spatial variability, and depth variation of compaction and subsidence in the GBD in order to better evaluate the processes controlling it and the pattern of relative sea level rise in this vulnerable region.
With support from the Bangladesh Water Development Board, we have rehabilitated previously installed GNSS and installed new GNSS co-located with Rod Surface Elevation Tables (RSET) to better understand the balance of subsidence and sedimentation in the coastal zone in SW Bangladesh, which is less affected by the active tectonic boundaries to the north and the east. The continuous GNSSs installed in 2003 and 2012 were mounted on reinforced concrete building roofs. GPS stations in the area yield subsidence rate estimates of 3-7 mm/y. To densify the subsidence data, in early 2020 we resurveyed 48 concrete Survey of Bangladesh geodetic monuments in SW Bangladesh that were installed in 2002. Although only measured at the start and end of the period, the time span between the two measurements is ~18 years enabling us to estimate subsidence over this timespan.
Preliminary results show that about ½ the sites yielded very high subsidence rates; repeat measurements confirm the suspicion that the monuments at these sites are unstable and have undergone localized subsidence from settling or anthropogenic activity. The remaining sites show an increase in subsidence from the NW to the SE, consistent with estimates of average Holocene subsidence (Grall et al., 2018). However, rates from the campaign stations are much higher than those from continuous GNSS sites, but only slightly higher than an RSET site. We interpret that the continuous building GNSS omit very shallow compaction-related subsidence, while RSETs neglect deep subsidence. This is further reinforced by results from a compaction meter consisting of 6 wells from 20 to 300 m depth with vertical optical fiber strainmeters in each well. They show a decrease in compaction with depth. While initial results require further investigation, we highlight the importance of multiple methodologies for interpreting subsidence rates--deep, shallow, natural, anthropogenic--in vulnerable delta regions.
How to cite: Steckler, M. S., Oryan, B., Jaman, Md. H., Mondal, D. R., Grall, C., Wilson, C. A., Akhter, S. H., DeWolf, S., and Goodbred, S. L.: Recent measurements of subsidence in the Ganges-Brahmaputra Delta, Bangladesh, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6562, https://doi.org/10.5194/egusphere-egu21-6562, 2021.
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Deltas, the low-lying land at rivers mouths, are sensitive to the delicate balance between sea level rise, land subsidence and sedimentation. Bangladesh and the Ganges-Brahmaputra Delta (GBD) have been highlighted as a region at risk from sea level rise, but reliable estimates of land subsidence have been limited. While early studies in the GBD suggested high rates of relative sea level rise, recent papers estimate more modest rates. Our objective is to better quantify the magnitude, spatial variability, and depth variation of compaction and subsidence in the GBD in order to better evaluate the processes controlling it and the pattern of relative sea level rise in this vulnerable region.
With support from the Bangladesh Water Development Board, we have rehabilitated previously installed GNSS and installed new GNSS co-located with Rod Surface Elevation Tables (RSET) to better understand the balance of subsidence and sedimentation in the coastal zone in SW Bangladesh, which is less affected by the active tectonic boundaries to the north and the east. The continuous GNSSs installed in 2003 and 2012 were mounted on reinforced concrete building roofs. GPS stations in the area yield subsidence rate estimates of 3-7 mm/y. To densify the subsidence data, in early 2020 we resurveyed 48 concrete Survey of Bangladesh geodetic monuments in SW Bangladesh that were installed in 2002. Although only measured at the start and end of the period, the time span between the two measurements is ~18 years enabling us to estimate subsidence over this timespan.
Preliminary results show that about ½ the sites yielded very high subsidence rates; repeat measurements confirm the suspicion that the monuments at these sites are unstable and have undergone localized subsidence from settling or anthropogenic activity. The remaining sites show an increase in subsidence from the NW to the SE, consistent with estimates of average Holocene subsidence (Grall et al., 2018). However, rates from the campaign stations are much higher than those from continuous GNSS sites, but only slightly higher than an RSET site. We interpret that the continuous building GNSS omit very shallow compaction-related subsidence, while RSETs neglect deep subsidence. This is further reinforced by results from a compaction meter consisting of 6 wells from 20 to 300 m depth with vertical optical fiber strainmeters in each well. They show a decrease in compaction with depth. While initial results require further investigation, we highlight the importance of multiple methodologies for interpreting subsidence rates--deep, shallow, natural, anthropogenic--in vulnerable delta regions.
How to cite: Steckler, M. S., Oryan, B., Jaman, Md. H., Mondal, D. R., Grall, C., Wilson, C. A., Akhter, S. H., DeWolf, S., and Goodbred, S. L.: Recent measurements of subsidence in the Ganges-Brahmaputra Delta, Bangladesh, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6562, https://doi.org/10.5194/egusphere-egu21-6562, 2021.
EGU21-13928 | vPICO presentations | GM6.9
Impacts of poldering: elevation change, sediment dynamics, and subsidence in the natural and human-altered Ganges Brahmaputra tidal deltaplainCarol Wilson, Sharmin Akter, Masud Rana, Michael Steckler, and Bar Oryan
In the Ganges-Brahmaputra Delta (GBD) and other tide-dominated low-lying regions, periodic tidal and cyclonic storm surge flooding of the land surface promotes sediment accretion and surface elevation gain which offsets elevation losses from eustatic sea level rise and subsidence. However, over the past several decades, anthropogenic modification of the GBD tidal deltaplain through embankment construction has precluded sediment delivery to densely populated embanked islands, locally-termed polders, resulting in landscapes 1-1.5 m lower than adjacent natural mangrove platforms. Recent discussion on GBD sustainability includes whether land surfaces (natural or anthropogenic) are keeping pace with local sea-level rise rates, and the quantification of continued elevation change, vertical accretion, and land subsidence. To provide local-scale, longitudinal trends of landscape dynamics, an array of Rod Surface Elevation Tables (RSETs) and sediment marker horizons was deployed in natural and embanked settings near Polder #32 and monitored seasonally over the past 6 years (expanded throughout the SW delta in 2019). These data are compared to existing and new co-located continuous GPS measurements (also expanded 2019). Near Polder #32, elevation gain is taking place in both natural and embanked regions (1-3 cm/yr), though it appears to be slightly greater (30%) within the poldered areas. This may be due to increased accommodation space and/or embankment sloughing. There also is a distinct seasonal pattern in both regions, with greater elevation change documented after the wet monsoon season (May-Sept), and either less elevation gain, or even elevation loss after the winter dry season (Jan-May). Elevation gain is a direct result of exceptionally large sediment vertical accretion (2-3 cm/yr), as measured from marker horizons and sediment tiles, and rates appear to be keeping pace with local effective sea-level rise documented by Pethick and Orford (2013). Seasonal shallow subsidence (0.8-1.1 cm/yr) is also observed, exacerbated in poldered regions during the dry season. These measurements of shallow subsidence are 30-50% greater than deeper subsidence measured with GPS (0.3-0.7 cm/yr) but consistent with resurveys of geodetic monuments (see Steckler et al. abstract). Preliminary results delta-wide show shallow subsidence can be as much as 3 cm over the course of one year. These data provide critical information to local stakeholders about the natural versus human-altered delta dynamics, and have cross-disciplinary implications for ecological productivity, social well-being, and flood risk mitigation.
How to cite: Wilson, C., Akter, S., Rana, M., Steckler, M., and Oryan, B.: Impacts of poldering: elevation change, sediment dynamics, and subsidence in the natural and human-altered Ganges Brahmaputra tidal deltaplain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13928, https://doi.org/10.5194/egusphere-egu21-13928, 2021.
In the Ganges-Brahmaputra Delta (GBD) and other tide-dominated low-lying regions, periodic tidal and cyclonic storm surge flooding of the land surface promotes sediment accretion and surface elevation gain which offsets elevation losses from eustatic sea level rise and subsidence. However, over the past several decades, anthropogenic modification of the GBD tidal deltaplain through embankment construction has precluded sediment delivery to densely populated embanked islands, locally-termed polders, resulting in landscapes 1-1.5 m lower than adjacent natural mangrove platforms. Recent discussion on GBD sustainability includes whether land surfaces (natural or anthropogenic) are keeping pace with local sea-level rise rates, and the quantification of continued elevation change, vertical accretion, and land subsidence. To provide local-scale, longitudinal trends of landscape dynamics, an array of Rod Surface Elevation Tables (RSETs) and sediment marker horizons was deployed in natural and embanked settings near Polder #32 and monitored seasonally over the past 6 years (expanded throughout the SW delta in 2019). These data are compared to existing and new co-located continuous GPS measurements (also expanded 2019). Near Polder #32, elevation gain is taking place in both natural and embanked regions (1-3 cm/yr), though it appears to be slightly greater (30%) within the poldered areas. This may be due to increased accommodation space and/or embankment sloughing. There also is a distinct seasonal pattern in both regions, with greater elevation change documented after the wet monsoon season (May-Sept), and either less elevation gain, or even elevation loss after the winter dry season (Jan-May). Elevation gain is a direct result of exceptionally large sediment vertical accretion (2-3 cm/yr), as measured from marker horizons and sediment tiles, and rates appear to be keeping pace with local effective sea-level rise documented by Pethick and Orford (2013). Seasonal shallow subsidence (0.8-1.1 cm/yr) is also observed, exacerbated in poldered regions during the dry season. These measurements of shallow subsidence are 30-50% greater than deeper subsidence measured with GPS (0.3-0.7 cm/yr) but consistent with resurveys of geodetic monuments (see Steckler et al. abstract). Preliminary results delta-wide show shallow subsidence can be as much as 3 cm over the course of one year. These data provide critical information to local stakeholders about the natural versus human-altered delta dynamics, and have cross-disciplinary implications for ecological productivity, social well-being, and flood risk mitigation.
How to cite: Wilson, C., Akter, S., Rana, M., Steckler, M., and Oryan, B.: Impacts of poldering: elevation change, sediment dynamics, and subsidence in the natural and human-altered Ganges Brahmaputra tidal deltaplain, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13928, https://doi.org/10.5194/egusphere-egu21-13928, 2021.
EGU21-475 * | vPICO presentations | GM6.9 | Highlight
The physical sustainability of the coastal zone of the Ganges-Brahmaputra-Meghna delta under climatic and anthropogenic stressesStephen Darby, Md. Munsur Rahman, Anisul Haque, Robert Nicholls, and Frances Dunn
The Ganges-Brahmaputra-Meghna (GBM) delta is one of the world’s largest deltas, and consists of large areas of low flat lands formed by the deposition of sediment from the GBM rivers. However, recent estimates have projected between 200~1000 mm of climate-driven sea-level rise by the end of the 21st century, at an average rate of ~6 mm/yr. Eustatic sea-level rise is further compounded by subsidence of the delta, which in the coastal fringes varies from 0.2 to 7.5 mm/yr, at an average value of ~2.0 mm/yr. Therefore, the combined effect of sea-level rise and subsidence (termed relative sea-level rise, RSLR) is around 8.0 mm/yr. Such high values of RSLR raise the question of whether sediment deposition on the surface of the delta is sufficient to maintain the delta surface above sea level. Moreover, as the total fluvial sediment influx to the GBM delta system is known to be decreasing, the retained portion of fluvial sediment on the delta surface is also likely decreasing, reducing the potential to offset RSLR. Within this context, the potential of various interventions geared at promoting greater retention of sediment on the delta surface is explored using numerical experiments under different flow-sediment regime and anthropogenic interventions. We find that for the existing, highly managed, conditions, the retained portion of fluvial sediment on the delta surface varies between 22% and 50% during average (when about 20% of the total floodplain in the country is inundated) and extreme (> 60% of the total floodplain in the country is inundated) flood years, respectively. However, the degree to which sediment has the potential to be deposited on the delta surface increases by up to 10% when existing anthropogenic interventions such as polders that act as barriers to delta-plain sedimentation are removed. While dismantling existing interventions is not a politically realistic proposition, more quasi-natural conditions can be reestablished through local- sediment management using tidal river management, cross dams, dredging, bandal-like structures and/or combinations of the above measures.
How to cite: Darby, S., Rahman, Md. M., Haque, A., Nicholls, R., and Dunn, F.: The physical sustainability of the coastal zone of the Ganges-Brahmaputra-Meghna delta under climatic and anthropogenic stresses, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-475, https://doi.org/10.5194/egusphere-egu21-475, 2021.
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The Ganges-Brahmaputra-Meghna (GBM) delta is one of the world’s largest deltas, and consists of large areas of low flat lands formed by the deposition of sediment from the GBM rivers. However, recent estimates have projected between 200~1000 mm of climate-driven sea-level rise by the end of the 21st century, at an average rate of ~6 mm/yr. Eustatic sea-level rise is further compounded by subsidence of the delta, which in the coastal fringes varies from 0.2 to 7.5 mm/yr, at an average value of ~2.0 mm/yr. Therefore, the combined effect of sea-level rise and subsidence (termed relative sea-level rise, RSLR) is around 8.0 mm/yr. Such high values of RSLR raise the question of whether sediment deposition on the surface of the delta is sufficient to maintain the delta surface above sea level. Moreover, as the total fluvial sediment influx to the GBM delta system is known to be decreasing, the retained portion of fluvial sediment on the delta surface is also likely decreasing, reducing the potential to offset RSLR. Within this context, the potential of various interventions geared at promoting greater retention of sediment on the delta surface is explored using numerical experiments under different flow-sediment regime and anthropogenic interventions. We find that for the existing, highly managed, conditions, the retained portion of fluvial sediment on the delta surface varies between 22% and 50% during average (when about 20% of the total floodplain in the country is inundated) and extreme (> 60% of the total floodplain in the country is inundated) flood years, respectively. However, the degree to which sediment has the potential to be deposited on the delta surface increases by up to 10% when existing anthropogenic interventions such as polders that act as barriers to delta-plain sedimentation are removed. While dismantling existing interventions is not a politically realistic proposition, more quasi-natural conditions can be reestablished through local- sediment management using tidal river management, cross dams, dredging, bandal-like structures and/or combinations of the above measures.
How to cite: Darby, S., Rahman, Md. M., Haque, A., Nicholls, R., and Dunn, F.: The physical sustainability of the coastal zone of the Ganges-Brahmaputra-Meghna delta under climatic and anthropogenic stresses, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-475, https://doi.org/10.5194/egusphere-egu21-475, 2021.
EGU21-1404 | vPICO presentations | GM6.9 | Highlight
Potential social-ecological development of coastal Bangladesh through the 21st centuryAttila N. Lazar, Robert J. Nicholls, Craig W. Hutton, Andres Payo, Helen Adams, Anisul Haque, Derek Clarke, Mashfiqus Salehin, Alistair Hunt, Andrew Allan, W. Neil Adger, and M. Munsur Rahman
Deltas occupy only 1% of global land surface area, but contain 7% of the global human population (ca. 500 million). The influence of changing and interacting climates, demography, economy, land use and coastal/catchment management on deltaic social-ecological systems is complex and little understood. We apply a new and innovative integrated assessment model: The Delta Dynamic Integrated Emulator Model (ΔDIEM) to coastal Bangladesh to explore a range of plausible future scenarios and quantify the sensitivities of selected environmental and socio-economic outcomes to key external and internal drivers. ΔDIEM is a tightly coupled integrated assessment platform considering climate and environmental change, demographic changes, economic changes, household decision making and governance, and designed to support the delta planning in Bangladesh. ΔDIEM allows the testing of a large number of water-based structural and policy interventions within a robust scenario framework, as well as quantify different development trajectories and their trade-offs. In this sensitivity analysis, we quantified the impact of (i) climate (precipitation, temperature and runoff), (ii) relative sea-level rise, (iii) cyclone frequency, (iv) embankment maintenance, (v) population size, (vi) economic changes at household level such as selling price of crops, cost of food, etc., (vii) land cover, and (viii) farming practices on trajectories of inundated area, soil salinity, rice productivity, poverty, income inequality and GDP/capita, assuming two contrasting scenarios in a more Positive and a more Negative World. Trajectories of these plausible futures showed a clear separation and the long-term trends are greatly influenced by the combinations of scenario assumptions. Our systemic results indicate a diverse potential set of futures for coastal Bangladesh, where good governance and adaptation could effectively mitigate the threat of sea-level rise-induced catastrophic inundation and other adverse impacts of the changing climate. However, societal inequality requires special attention otherwise climate-sensitive population groups may be left behind.
How to cite: Lazar, A. N., Nicholls, R. J., Hutton, C. W., Payo, A., Adams, H., Haque, A., Clarke, D., Salehin, M., Hunt, A., Allan, A., Adger, W. N., and Rahman, M. M.: Potential social-ecological development of coastal Bangladesh through the 21st century, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1404, https://doi.org/10.5194/egusphere-egu21-1404, 2021.
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Deltas occupy only 1% of global land surface area, but contain 7% of the global human population (ca. 500 million). The influence of changing and interacting climates, demography, economy, land use and coastal/catchment management on deltaic social-ecological systems is complex and little understood. We apply a new and innovative integrated assessment model: The Delta Dynamic Integrated Emulator Model (ΔDIEM) to coastal Bangladesh to explore a range of plausible future scenarios and quantify the sensitivities of selected environmental and socio-economic outcomes to key external and internal drivers. ΔDIEM is a tightly coupled integrated assessment platform considering climate and environmental change, demographic changes, economic changes, household decision making and governance, and designed to support the delta planning in Bangladesh. ΔDIEM allows the testing of a large number of water-based structural and policy interventions within a robust scenario framework, as well as quantify different development trajectories and their trade-offs. In this sensitivity analysis, we quantified the impact of (i) climate (precipitation, temperature and runoff), (ii) relative sea-level rise, (iii) cyclone frequency, (iv) embankment maintenance, (v) population size, (vi) economic changes at household level such as selling price of crops, cost of food, etc., (vii) land cover, and (viii) farming practices on trajectories of inundated area, soil salinity, rice productivity, poverty, income inequality and GDP/capita, assuming two contrasting scenarios in a more Positive and a more Negative World. Trajectories of these plausible futures showed a clear separation and the long-term trends are greatly influenced by the combinations of scenario assumptions. Our systemic results indicate a diverse potential set of futures for coastal Bangladesh, where good governance and adaptation could effectively mitigate the threat of sea-level rise-induced catastrophic inundation and other adverse impacts of the changing climate. However, societal inequality requires special attention otherwise climate-sensitive population groups may be left behind.
How to cite: Lazar, A. N., Nicholls, R. J., Hutton, C. W., Payo, A., Adams, H., Haque, A., Clarke, D., Salehin, M., Hunt, A., Allan, A., Adger, W. N., and Rahman, M. M.: Potential social-ecological development of coastal Bangladesh through the 21st century, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1404, https://doi.org/10.5194/egusphere-egu21-1404, 2021.
EGU21-11090 | vPICO presentations | GM6.9
The future of the Sundarbans mangroves in IndiaSugata Hazra, Sourav Samanta, Ananya Halder, Robert Nicholls, and Jon French
The Sundarbans Biosphere Reserve is situated near Kolkata in the western part of the Ganges-Brahmaputra Delta. The Sundarbans mangroves together with the areas in Bangladesh are the world’s largest mangrove forest and home to the iconic Royal Bengal Tiger. It is a Ramsar and World Heritage site. Over the last 20 years the mangroves have retreated from 10 to 50 m/yr along the open coast with the loss of 145 km2 area of the biosphere reserve , 40% of which constitute the mangrove forest. This erosion reflects a response to waves in the Bay of Bengaland relative sea-level rise of about 5 mm/yr since 1948 which increased further during the last decade. In percentage terms this observed forest land loss is manageable. However, it will continue and almost certainly accelerate with sea-level rise. As well as open coast erosion, inundation will also occur within the mangroves. Hence over many decades,Sundarbans mangroves will be progressively degraded endangering their iconic species. We are using these observed data and the Sea Level Affecting Marshes Model (SLAMM)to explore possible trajectories of the Sundarbans evolution under different sea-level rise scenarios and management interventions. The areas to the north are densely populated and increasingly influenced by the expansion of Kolkata. Discussions with stakeholders suggest a managed retreat does not seem feasible or practical due to the large displaced populations.The paper will discuss theinter linkages of the slow onset hazard in a sinking and shrinking delta to explore pathways to achieve sustainable outcomes in south Asian deltas.
How to cite: Hazra, S., Samanta, S., Halder, A., Nicholls, R., and French, J.: The future of the Sundarbans mangroves in India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11090, https://doi.org/10.5194/egusphere-egu21-11090, 2021.
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The Sundarbans Biosphere Reserve is situated near Kolkata in the western part of the Ganges-Brahmaputra Delta. The Sundarbans mangroves together with the areas in Bangladesh are the world’s largest mangrove forest and home to the iconic Royal Bengal Tiger. It is a Ramsar and World Heritage site. Over the last 20 years the mangroves have retreated from 10 to 50 m/yr along the open coast with the loss of 145 km2 area of the biosphere reserve , 40% of which constitute the mangrove forest. This erosion reflects a response to waves in the Bay of Bengaland relative sea-level rise of about 5 mm/yr since 1948 which increased further during the last decade. In percentage terms this observed forest land loss is manageable. However, it will continue and almost certainly accelerate with sea-level rise. As well as open coast erosion, inundation will also occur within the mangroves. Hence over many decades,Sundarbans mangroves will be progressively degraded endangering their iconic species. We are using these observed data and the Sea Level Affecting Marshes Model (SLAMM)to explore possible trajectories of the Sundarbans evolution under different sea-level rise scenarios and management interventions. The areas to the north are densely populated and increasingly influenced by the expansion of Kolkata. Discussions with stakeholders suggest a managed retreat does not seem feasible or practical due to the large displaced populations.The paper will discuss theinter linkages of the slow onset hazard in a sinking and shrinking delta to explore pathways to achieve sustainable outcomes in south Asian deltas.
How to cite: Hazra, S., Samanta, S., Halder, A., Nicholls, R., and French, J.: The future of the Sundarbans mangroves in India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11090, https://doi.org/10.5194/egusphere-egu21-11090, 2021.
EGU21-14104 | vPICO presentations | GM6.9 | Highlight
Shrinking Ecosystem Services in a Sinking Delta – Maintaining livelihoods in the Sundarbans Biosphere Reserve, IndiaOindrila Basu, Isha Das, Sudipa Pal, Tim Daw, and Sugata Hazra
A range of ecosystem services provide critical direct benefits to poor households living in the Sundarban Biosphere Reserve in India. These include artisanal fishing in creeks and rivers, crab collection, prawn seed collection, brackish and fresh-water aquaculture, fuel, fodder and honey collection from forests, and marine fishing in mechanized and non mechanized boats. The roles of these ecosystem services are largely invisible to official data. Triangulating between available statistics, key informant interviews and a new household survey, we estimate that nearly 30% of the 4.6 million population, mostly poor people rely on these ecosystem services. Ecosystem services supplement traditional rainfed agriculture, providing over 30% of household livelihood requirements. The availability of these ecosystem services is declining in per-capita terms due to the rapidly rising population in addition to ecosystem degradation. The area and health of mangrove is affected by sea level rise, differential subsidence, reduction of sediment and freshwater supply due to human obstruction and abstraction, increased salinity, high intensity cyclones, monsoon instability and temperature rise. Under a business as usual scenario, sharp decline of provisioning and regulating ecosystem services available per capita by 2030 is envisaged resulting in the threatening to increase poverty in the Biosphere Reserve. We review policy options to protect and enhance these critical ecosystem services for poor households including restoration of the estuarine mangrove habitat through river reconnection and rejuvenation and fresh water provisioning and desalination, scientific plantation and shore protection using building with nature concept, regulating marine fishery and aquaculture practices , land use planning and population realignment.
How to cite: Basu, O., Das, I., Pal, S., Daw, T., and Hazra, S.: Shrinking Ecosystem Services in a Sinking Delta – Maintaining livelihoods in the Sundarbans Biosphere Reserve, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14104, https://doi.org/10.5194/egusphere-egu21-14104, 2021.
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A range of ecosystem services provide critical direct benefits to poor households living in the Sundarban Biosphere Reserve in India. These include artisanal fishing in creeks and rivers, crab collection, prawn seed collection, brackish and fresh-water aquaculture, fuel, fodder and honey collection from forests, and marine fishing in mechanized and non mechanized boats. The roles of these ecosystem services are largely invisible to official data. Triangulating between available statistics, key informant interviews and a new household survey, we estimate that nearly 30% of the 4.6 million population, mostly poor people rely on these ecosystem services. Ecosystem services supplement traditional rainfed agriculture, providing over 30% of household livelihood requirements. The availability of these ecosystem services is declining in per-capita terms due to the rapidly rising population in addition to ecosystem degradation. The area and health of mangrove is affected by sea level rise, differential subsidence, reduction of sediment and freshwater supply due to human obstruction and abstraction, increased salinity, high intensity cyclones, monsoon instability and temperature rise. Under a business as usual scenario, sharp decline of provisioning and regulating ecosystem services available per capita by 2030 is envisaged resulting in the threatening to increase poverty in the Biosphere Reserve. We review policy options to protect and enhance these critical ecosystem services for poor households including restoration of the estuarine mangrove habitat through river reconnection and rejuvenation and fresh water provisioning and desalination, scientific plantation and shore protection using building with nature concept, regulating marine fishery and aquaculture practices , land use planning and population realignment.
How to cite: Basu, O., Das, I., Pal, S., Daw, T., and Hazra, S.: Shrinking Ecosystem Services in a Sinking Delta – Maintaining livelihoods in the Sundarbans Biosphere Reserve, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14104, https://doi.org/10.5194/egusphere-egu21-14104, 2021.
EGU21-16485 | vPICO presentations | GM6.9
What is driving conversion of land to aquaculture in the Indian Sundarbans?Tim M. Daw, Sandip Giri, Partho Protim Mondal, Sourav Samanta, Sugata Hazra, Craig Hutton, Duncan D. Hornby, Andrew Harfoot, Kasturi Mukherjee, and Radhika Gupta
Land in the Indian Sundarbans Biosphere Reserve (SBR) has been extensively (and illegally) converted from agriculture to aquaculture over the last two decades, with implications for Sustainable Development Goals addressing food, poverty, employment, terrestrial and marine ecosystems and inequality. The economic returns from aquaculture are higher than agriculture, but more unequally shared, demand for labour is lower (and often fullfilled by non-local workers) and the expansion of brackish water aquaculture, in particular can contribute to the salinization of land through seepage from ponds, and intentional water management to bring saline water to farms. While remote sensing can demonstrate the conversion, the drivers behind are less clear. Much literature, along with commonly articulated stakeholder perspectives strongly suggest that sea-level rise and cyclone impacts lead to salinization, resulting in reduced agricultural productivity, leading farmers to convert to saline aquaculture as an adaptation. However, this is unclear in the Indian Sundarbans where the highest rates of conversion are not in areas which have suffered saline inundation. SBR-wide factors that affect rates of conversion include international demand for prawns, technology development and transfer, availability of seed, legal frameworks and land tenure. At a more local level, connectivity (for inputs and for marketing product), proximity to water sources, levels of cyclone inundation, salinity and agricultural productivity, existing aquaculture areas, extension services and local government (dis)incentives may explain spatial patterns of differing conversion rates. In this paper we use a two-decade long timeseries of remotely sensed data on land cover and agricultural productivity along with spatially explicit data on connectivity to evaluate which factors were most associated with conversion from agriculture to aquaculture in the past two decades. We then project future possible conversion based on scenarios of how these drivers may change over the the next decade and discuss their implications for Sustainable Development Goals.
How to cite: Daw, T. M., Giri, S., Mondal, P. P., Samanta, S., Hazra, S., Hutton, C., Hornby, D. D., Harfoot, A., Mukherjee, K., and Gupta, R.: What is driving conversion of land to aquaculture in the Indian Sundarbans?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16485, https://doi.org/10.5194/egusphere-egu21-16485, 2021.
Land in the Indian Sundarbans Biosphere Reserve (SBR) has been extensively (and illegally) converted from agriculture to aquaculture over the last two decades, with implications for Sustainable Development Goals addressing food, poverty, employment, terrestrial and marine ecosystems and inequality. The economic returns from aquaculture are higher than agriculture, but more unequally shared, demand for labour is lower (and often fullfilled by non-local workers) and the expansion of brackish water aquaculture, in particular can contribute to the salinization of land through seepage from ponds, and intentional water management to bring saline water to farms. While remote sensing can demonstrate the conversion, the drivers behind are less clear. Much literature, along with commonly articulated stakeholder perspectives strongly suggest that sea-level rise and cyclone impacts lead to salinization, resulting in reduced agricultural productivity, leading farmers to convert to saline aquaculture as an adaptation. However, this is unclear in the Indian Sundarbans where the highest rates of conversion are not in areas which have suffered saline inundation. SBR-wide factors that affect rates of conversion include international demand for prawns, technology development and transfer, availability of seed, legal frameworks and land tenure. At a more local level, connectivity (for inputs and for marketing product), proximity to water sources, levels of cyclone inundation, salinity and agricultural productivity, existing aquaculture areas, extension services and local government (dis)incentives may explain spatial patterns of differing conversion rates. In this paper we use a two-decade long timeseries of remotely sensed data on land cover and agricultural productivity along with spatially explicit data on connectivity to evaluate which factors were most associated with conversion from agriculture to aquaculture in the past two decades. We then project future possible conversion based on scenarios of how these drivers may change over the the next decade and discuss their implications for Sustainable Development Goals.
How to cite: Daw, T. M., Giri, S., Mondal, P. P., Samanta, S., Hazra, S., Hutton, C., Hornby, D. D., Harfoot, A., Mukherjee, K., and Gupta, R.: What is driving conversion of land to aquaculture in the Indian Sundarbans?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16485, https://doi.org/10.5194/egusphere-egu21-16485, 2021.
EGU21-8764 | vPICO presentations | GM6.9
A framework for the Integrated Assessment of SDG trade-offs in the Sundarbans Biosphere Reserve.Charlotte Marcinko, Robert Nicholls, Tim Daw, Sugata Hazra, Craig Hutton, Chris Hill, Derek Clarke, Andy Harfoot, Oindrila Basu, Isha Das, Sandip Giri, Sudipa Pal, and Partho Mondal
The United Nations Sustainable Development Goals (SDGs) and their corresponding targets are significantly interconnected, with many interactions, synergies and trade-offs between individual goals across multiple temporal and spatial scales. We propose a framework for the Integrated Assessment Modelling (IAM) of a complex deltaic socio-ecological system in order to analyse such SDG interactions. We focus on the Sundarbans Biosphere Reserve (SBR), India within the Ganges-Brahmaputra-Meghna Delta. It is densely populated with 4.4 million people (2011), high levels of poverty and a strong dependence on rural livelihoods. It is only 50 km from the growing megacity of Kolkata (about 15 million people in 2020). The area also includes the Indian portion of the world’s largest mangrove forest – the Sundarbans – hosting the iconic Bengal Tiger. Like all deltaic systems, this area is subject to multiple drivers of environmental change operating across different scales. The IAM framework is designed to investigate current and future trends in socio-environmental change and explore associated policy impacts, considering a broad range of sub-thematic SDG indicators. Integration is achieved through the soft coupling of multiple sub-models, knowledge and data of relevant environmental and socio-economic processes. The following elements are explicitly considered: (1) agriculture; (2) aquaculture; (3) mangroves; (4) fisheries; and (5) multidimensional poverty. Key questions that can be addressed include the implications of changing monsoon patterns, trade-offs between agriculture and aquaculture, or the future of the Sundarbans mangroves under sea-level rise and different management strategies, including trade-offs with land use to the north. The novel high-resolution analysis of SDG interactions allowed by the IAM will provide stakeholders and policy makers the opportunity to prioritize and explore the SDG targets that are most relevant to the SBR and provide a foundation for further integrated analysis.
How to cite: Marcinko, C., Nicholls, R., Daw, T., Hazra, S., Hutton, C., Hill, C., Clarke, D., Harfoot, A., Basu, O., Das, I., Giri, S., Pal, S., and Mondal, P.: A framework for the Integrated Assessment of SDG trade-offs in the Sundarbans Biosphere Reserve., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8764, https://doi.org/10.5194/egusphere-egu21-8764, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The United Nations Sustainable Development Goals (SDGs) and their corresponding targets are significantly interconnected, with many interactions, synergies and trade-offs between individual goals across multiple temporal and spatial scales. We propose a framework for the Integrated Assessment Modelling (IAM) of a complex deltaic socio-ecological system in order to analyse such SDG interactions. We focus on the Sundarbans Biosphere Reserve (SBR), India within the Ganges-Brahmaputra-Meghna Delta. It is densely populated with 4.4 million people (2011), high levels of poverty and a strong dependence on rural livelihoods. It is only 50 km from the growing megacity of Kolkata (about 15 million people in 2020). The area also includes the Indian portion of the world’s largest mangrove forest – the Sundarbans – hosting the iconic Bengal Tiger. Like all deltaic systems, this area is subject to multiple drivers of environmental change operating across different scales. The IAM framework is designed to investigate current and future trends in socio-environmental change and explore associated policy impacts, considering a broad range of sub-thematic SDG indicators. Integration is achieved through the soft coupling of multiple sub-models, knowledge and data of relevant environmental and socio-economic processes. The following elements are explicitly considered: (1) agriculture; (2) aquaculture; (3) mangroves; (4) fisheries; and (5) multidimensional poverty. Key questions that can be addressed include the implications of changing monsoon patterns, trade-offs between agriculture and aquaculture, or the future of the Sundarbans mangroves under sea-level rise and different management strategies, including trade-offs with land use to the north. The novel high-resolution analysis of SDG interactions allowed by the IAM will provide stakeholders and policy makers the opportunity to prioritize and explore the SDG targets that are most relevant to the SBR and provide a foundation for further integrated analysis.
How to cite: Marcinko, C., Nicholls, R., Daw, T., Hazra, S., Hutton, C., Hill, C., Clarke, D., Harfoot, A., Basu, O., Das, I., Giri, S., Pal, S., and Mondal, P.: A framework for the Integrated Assessment of SDG trade-offs in the Sundarbans Biosphere Reserve., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8764, https://doi.org/10.5194/egusphere-egu21-8764, 2021.
EGU21-9305 | vPICO presentations | GM6.9
Sustainable Deltas in the AnthropoceneRobert Nicholls, Neil Adger, Craig Hutton, Susan Hanson, Attila Lázár, Katharine Vincent, Andrew Allan, Emma Tompkins, Iñaki Arto, Munsur Rahman, Sugata Hazra, Sam Codjoe, and Stephen Darby
Populous deltas exemplify many of the diverse social and environmental changes and challenges that are emerging across the planet during the Anthropocene. Loss of relative elevation due to relative sea-level rise (combining climate and subsidence effects) is one major threat, but there are others such as catchment changes (e.g., water extraction and dam construction) which reduce water and sediment inputs. Rapid socio-economic changes within a delta (e.g., migration, urbanisation, economic transition and land use change) are also widespread and frequently add further pressures on the environmental resources contained within delta systems. There are long histories of evolving adaptation practice at household to community level. In the long-term (i.e. 2100 and beyond), given relative sea-level rise, there are three distinct (but not necessarily mutually exclusive) policy choices for deltas: (i) retreat and progressive abandonment of the coastal zone; (ii) protection with ever-higher defences, growing pumping needs, and residual risk issues; or (iii) raise land elevation by controlled sedimentation. Building elevation is an attractive option if sufficient sediment is available, and there are now a few innovative examples that show it can be delivered to the delta surface— for example, through strategic raising of agricultural and natural areas with controlled sedimentation. One challenge is to accomplish this in a way which does not disrupt the livelihoods of the delta residents. Further is sufficient sediment available now or in the future, and what about growing urban areas where flood defence is likely to remain the norm? This raises the question about the trade-off between elevation and wealth. Many deltas cope with ‘lost elevation’ via defences: the Netherlands is most advanced in this approach, but such defences are expensive, require access to technology, and require sophisticated governance arrangements to deliver. A range of potential adaptation options at different scales and with different levels of cost will be required to sustain delta futures. This presentation examines potential adaptation options and trade-offs and delta trajectories in a range of examples including the Volta delta, Ghana, the Mahanadi delta, India and the Ganges-Brahmaputra-Meghna delta, India and Bangladesh.
How to cite: Nicholls, R., Adger, N., Hutton, C., Hanson, S., Lázár, A., Vincent, K., Allan, A., Tompkins, E., Arto, I., Rahman, M., Hazra, S., Codjoe, S., and Darby, S.: Sustainable Deltas in the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9305, https://doi.org/10.5194/egusphere-egu21-9305, 2021.
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Populous deltas exemplify many of the diverse social and environmental changes and challenges that are emerging across the planet during the Anthropocene. Loss of relative elevation due to relative sea-level rise (combining climate and subsidence effects) is one major threat, but there are others such as catchment changes (e.g., water extraction and dam construction) which reduce water and sediment inputs. Rapid socio-economic changes within a delta (e.g., migration, urbanisation, economic transition and land use change) are also widespread and frequently add further pressures on the environmental resources contained within delta systems. There are long histories of evolving adaptation practice at household to community level. In the long-term (i.e. 2100 and beyond), given relative sea-level rise, there are three distinct (but not necessarily mutually exclusive) policy choices for deltas: (i) retreat and progressive abandonment of the coastal zone; (ii) protection with ever-higher defences, growing pumping needs, and residual risk issues; or (iii) raise land elevation by controlled sedimentation. Building elevation is an attractive option if sufficient sediment is available, and there are now a few innovative examples that show it can be delivered to the delta surface— for example, through strategic raising of agricultural and natural areas with controlled sedimentation. One challenge is to accomplish this in a way which does not disrupt the livelihoods of the delta residents. Further is sufficient sediment available now or in the future, and what about growing urban areas where flood defence is likely to remain the norm? This raises the question about the trade-off between elevation and wealth. Many deltas cope with ‘lost elevation’ via defences: the Netherlands is most advanced in this approach, but such defences are expensive, require access to technology, and require sophisticated governance arrangements to deliver. A range of potential adaptation options at different scales and with different levels of cost will be required to sustain delta futures. This presentation examines potential adaptation options and trade-offs and delta trajectories in a range of examples including the Volta delta, Ghana, the Mahanadi delta, India and the Ganges-Brahmaputra-Meghna delta, India and Bangladesh.
How to cite: Nicholls, R., Adger, N., Hutton, C., Hanson, S., Lázár, A., Vincent, K., Allan, A., Tompkins, E., Arto, I., Rahman, M., Hazra, S., Codjoe, S., and Darby, S.: Sustainable Deltas in the Anthropocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9305, https://doi.org/10.5194/egusphere-egu21-9305, 2021.
GM6.10 – The future of estuaries and deltas: natural processes and human interference
EGU21-967 * | vPICO presentations | GM6.10 | Highlight
Sediment retention in river deltas and feedbacks with delta morphologyJaap Nienhuis, Juan Paniagua-Arroyave, Frances Dunn, Sagy Cohen, and Torbjorn Tornqvist
Fluvial sediments have collectively formed about 900,000 km2 of deltaic land since Holocene sea-level rise slowed down. The rate at which deltas have retained fluvial sediment to build deltaic land, however, has varied greatly between different deltas. Here we quantify sediment retention in the delta topset and foreset for 3,556 deltas globally. We estimate retention from data on delta morphology and cross-sectional area, combined with WBMSed data on fluvial suspended sediment supply. Deltas, on average, retain 25±2% (standard error of the mean) of the fluvial sediment in their topset and 31±2% in their foreset. Because topset sediment retention reduces the sediment delivery to the river mouth, it sets up a feedback with processes that build delta morphology. Waves reduce topset sediment retention whereas tides increase it. Tide dominated deltas retain 61±24% on their topset, on average, compared to 21±3% and 24±2% for river- and wave-dominated deltas, respectively. Larger deltas trap more sediment, but not in comparison to their larger sediment loads, making them relatively inefficient sediment traps.
How to cite: Nienhuis, J., Paniagua-Arroyave, J., Dunn, F., Cohen, S., and Tornqvist, T.: Sediment retention in river deltas and feedbacks with delta morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-967, https://doi.org/10.5194/egusphere-egu21-967, 2021.
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Fluvial sediments have collectively formed about 900,000 km2 of deltaic land since Holocene sea-level rise slowed down. The rate at which deltas have retained fluvial sediment to build deltaic land, however, has varied greatly between different deltas. Here we quantify sediment retention in the delta topset and foreset for 3,556 deltas globally. We estimate retention from data on delta morphology and cross-sectional area, combined with WBMSed data on fluvial suspended sediment supply. Deltas, on average, retain 25±2% (standard error of the mean) of the fluvial sediment in their topset and 31±2% in their foreset. Because topset sediment retention reduces the sediment delivery to the river mouth, it sets up a feedback with processes that build delta morphology. Waves reduce topset sediment retention whereas tides increase it. Tide dominated deltas retain 61±24% on their topset, on average, compared to 21±3% and 24±2% for river- and wave-dominated deltas, respectively. Larger deltas trap more sediment, but not in comparison to their larger sediment loads, making them relatively inefficient sediment traps.
How to cite: Nienhuis, J., Paniagua-Arroyave, J., Dunn, F., Cohen, S., and Tornqvist, T.: Sediment retention in river deltas and feedbacks with delta morphology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-967, https://doi.org/10.5194/egusphere-egu21-967, 2021.
EGU21-1441 | vPICO presentations | GM6.10
A Tale of Two Deltas: Comparative Study on the Effects of Dam Regulation on Deltaic Hydrological Regime and Morphological EvolutionWeilun Gao, Dongxue Li, Mawusi Amenuvor, Yao Tong, Dongdong Shao, and Baoshan Cui
Deltas are among the most populous areas and most productive ecosystems on Earth. Despite their critical importance for human society and coastal ecosystems, many of the world’s deltas are drowning due to substantial decrease in sediment supply, sea level rise, etc. Previous studies have demonstrated the effects of dam regulation on the hydrological regime and morphological evolution of river deltas. However, past attention was mostly paid to individual deltas or deltas at a global scale, while comparative studies on selected deltas are scarce in the literature. In this study, a comparative study on two wave-influenced deltas, namely, the Volta River Delta in Ghana and the Yellow River Delta in China, was conducted. The trend of change of the annual river discharge and sediment load of the two deltas before and after the construction of the major dams were analyzed, and the resultant effects on deltaic morphological evolution were also examined and compared between the two deltas. The results show that the average annual river discharge and sediment load and their inter-annual variation decreased significantly after the construction of major upstream dams for both deltas. However, presumably due to the differences in reservoir capacity and upstream location of the dams, the sediment load of the Volta River Delta decreased abruptly to <10% of the sediment load in the pre-dam period after the construction of the Akosombo Dam in 1964 and became stable afterwards, whereas the sediment load of the Yellow River Delta decreased substantially to ~10% of pre-dam level but in a more gradual stepwise manner since the 1950s. As a result, after the intense shoreline retreat in the 1960s, the delta area of the Volta River Delta appeared to adjust to the reduced yet stable sediment load and shift to a new quasi-equilibrium with minimal change (maximum 0.53%). On the contrary, the Yellow River Delta still kept prograding at the river mouth given the current sediment load. However, it is foreseeable that if the trend of sediment reduction persists, it may potentially turn net delta progradation to erosion and further into a new quasi-equilibrium like the Volta River Delta. Our study provides a new perspective for understanding the future evolution of the Yellow River Delta as well as other deltas around the world that share similar characteristics and forcing factors.
How to cite: Gao, W., Li, D., Amenuvor, M., Tong, Y., Shao, D., and Cui, B.: A Tale of Two Deltas: Comparative Study on the Effects of Dam Regulation on Deltaic Hydrological Regime and Morphological Evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1441, https://doi.org/10.5194/egusphere-egu21-1441, 2021.
Deltas are among the most populous areas and most productive ecosystems on Earth. Despite their critical importance for human society and coastal ecosystems, many of the world’s deltas are drowning due to substantial decrease in sediment supply, sea level rise, etc. Previous studies have demonstrated the effects of dam regulation on the hydrological regime and morphological evolution of river deltas. However, past attention was mostly paid to individual deltas or deltas at a global scale, while comparative studies on selected deltas are scarce in the literature. In this study, a comparative study on two wave-influenced deltas, namely, the Volta River Delta in Ghana and the Yellow River Delta in China, was conducted. The trend of change of the annual river discharge and sediment load of the two deltas before and after the construction of the major dams were analyzed, and the resultant effects on deltaic morphological evolution were also examined and compared between the two deltas. The results show that the average annual river discharge and sediment load and their inter-annual variation decreased significantly after the construction of major upstream dams for both deltas. However, presumably due to the differences in reservoir capacity and upstream location of the dams, the sediment load of the Volta River Delta decreased abruptly to <10% of the sediment load in the pre-dam period after the construction of the Akosombo Dam in 1964 and became stable afterwards, whereas the sediment load of the Yellow River Delta decreased substantially to ~10% of pre-dam level but in a more gradual stepwise manner since the 1950s. As a result, after the intense shoreline retreat in the 1960s, the delta area of the Volta River Delta appeared to adjust to the reduced yet stable sediment load and shift to a new quasi-equilibrium with minimal change (maximum 0.53%). On the contrary, the Yellow River Delta still kept prograding at the river mouth given the current sediment load. However, it is foreseeable that if the trend of sediment reduction persists, it may potentially turn net delta progradation to erosion and further into a new quasi-equilibrium like the Volta River Delta. Our study provides a new perspective for understanding the future evolution of the Yellow River Delta as well as other deltas around the world that share similar characteristics and forcing factors.
How to cite: Gao, W., Li, D., Amenuvor, M., Tong, Y., Shao, D., and Cui, B.: A Tale of Two Deltas: Comparative Study on the Effects of Dam Regulation on Deltaic Hydrological Regime and Morphological Evolution, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1441, https://doi.org/10.5194/egusphere-egu21-1441, 2021.
EGU21-1639 | vPICO presentations | GM6.10 | Highlight
Coastal flooding protection will change salt-marsh sedimentation dynamicsDavide Tognin, Andrea D'Alpaos, Marco Marani, and Luca Carniello
Coastal wetlands lie at the interface between submerged and emerged environments and therefore represent unique yet delicate ecosystems. Their existence, resulting from complex interactions between hydrodynamics and sediment dynamics, is challenged by increasing rates of sea-level rise, lowered fluvial sediment input as well as an increasing anthropogenic pressure. The future survival of these peculiar morphologies is becoming even more complicated, because of the construction and planning of coastal defence structures designed to protect urban areas from flooding. Important examples are the flood protection systems built to protect New Orleans (USA), the river Scheldt Estuary (The Netherlands) and Venice (Italy). In this context, understanding the physical processes on which coastal marshes are grounded and how engineering measures can alter them is of extreme importance in order to plan conservation interventions.
To understand marsh sedimentation dynamics in flood-regulated environments, we investigated through field observations and modelling the effect of the storm-surge barrier designed to protect the city of Venice, the so-called Mo.S.E. system, which has in fact become operational since October 2020.
Sedimentation measurements in different salt marshes of the Venice lagoon carried out in the period October 2018-October 2020 show that more than 70% of yearly sedimentation accumulates during storm-surge conditions, despite their short duration. Moreover, the sedimentation rate displays a highly non-linear increase with marsh inundation intensity, due to the interplay between higher water levels and greater suspended sediment concentration. Barrier operations during storm surges to avoid flooding of urban areas will reduce water levels and marsh inundation. Therefore, we computed sedimentation in a flood-regulated scenario for the same observation period, using the relation we obtained between tidal forcing and sedimentation rate. Our results show that some occasional closures during intense storm surges (70 hours/year on average) suffice to reduce the yearly sedimentation of the same order of magnitude of the relative sea-level rise rate experienced by the Venice lagoon during the last century (2.5 mm/y).
We conclude that storm-surge barrier operations can dangerously reduce salt-marsh vertical accretion rate, thus challenging wetland survival in face of increasing sea-level rise.
How to cite: Tognin, D., D'Alpaos, A., Marani, M., and Carniello, L.: Coastal flooding protection will change salt-marsh sedimentation dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1639, https://doi.org/10.5194/egusphere-egu21-1639, 2021.
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Coastal wetlands lie at the interface between submerged and emerged environments and therefore represent unique yet delicate ecosystems. Their existence, resulting from complex interactions between hydrodynamics and sediment dynamics, is challenged by increasing rates of sea-level rise, lowered fluvial sediment input as well as an increasing anthropogenic pressure. The future survival of these peculiar morphologies is becoming even more complicated, because of the construction and planning of coastal defence structures designed to protect urban areas from flooding. Important examples are the flood protection systems built to protect New Orleans (USA), the river Scheldt Estuary (The Netherlands) and Venice (Italy). In this context, understanding the physical processes on which coastal marshes are grounded and how engineering measures can alter them is of extreme importance in order to plan conservation interventions.
To understand marsh sedimentation dynamics in flood-regulated environments, we investigated through field observations and modelling the effect of the storm-surge barrier designed to protect the city of Venice, the so-called Mo.S.E. system, which has in fact become operational since October 2020.
Sedimentation measurements in different salt marshes of the Venice lagoon carried out in the period October 2018-October 2020 show that more than 70% of yearly sedimentation accumulates during storm-surge conditions, despite their short duration. Moreover, the sedimentation rate displays a highly non-linear increase with marsh inundation intensity, due to the interplay between higher water levels and greater suspended sediment concentration. Barrier operations during storm surges to avoid flooding of urban areas will reduce water levels and marsh inundation. Therefore, we computed sedimentation in a flood-regulated scenario for the same observation period, using the relation we obtained between tidal forcing and sedimentation rate. Our results show that some occasional closures during intense storm surges (70 hours/year on average) suffice to reduce the yearly sedimentation of the same order of magnitude of the relative sea-level rise rate experienced by the Venice lagoon during the last century (2.5 mm/y).
We conclude that storm-surge barrier operations can dangerously reduce salt-marsh vertical accretion rate, thus challenging wetland survival in face of increasing sea-level rise.
How to cite: Tognin, D., D'Alpaos, A., Marani, M., and Carniello, L.: Coastal flooding protection will change salt-marsh sedimentation dynamics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1639, https://doi.org/10.5194/egusphere-egu21-1639, 2021.
EGU21-3302 | vPICO presentations | GM6.10
Potential Morphologic Responses of Tropical River Deltas in Colombia to Future Sediment Supply ScenariosJuan F. Paniagua-Arroyave, Jaap H. Nienhuis, and Frances E. Dunn
Riverine sediment yield changes by human-induced catchment alterations can have important implications for river delta morphology. Here, we assess the potential response of 99 tropical deltas along the Caribbean and Pacific coasts of Colombia to projected human land use intensifications by deforestation and river damming. We assess delta morphology through the balance of wave, tidal, and (modern and future) river sediment transport processes at their mouths. We find that most Colombian deltas along the Caribbean coast are wave-dominated, except for large catchments with high riverine sediment load, which are river-dominated. Most deltas are wave-river dominated along the Pacific coast, with few examples of river-tide and wave-tide dominance. We predict Colombian deltas to become more wave and tide-dominated under river damming scenarios. In contrast, deforestation scenarios suggested virtually no future morphological changes.
How to cite: Paniagua-Arroyave, J. F., Nienhuis, J. H., and Dunn, F. E.: Potential Morphologic Responses of Tropical River Deltas in Colombia to Future Sediment Supply Scenarios, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3302, https://doi.org/10.5194/egusphere-egu21-3302, 2021.
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Riverine sediment yield changes by human-induced catchment alterations can have important implications for river delta morphology. Here, we assess the potential response of 99 tropical deltas along the Caribbean and Pacific coasts of Colombia to projected human land use intensifications by deforestation and river damming. We assess delta morphology through the balance of wave, tidal, and (modern and future) river sediment transport processes at their mouths. We find that most Colombian deltas along the Caribbean coast are wave-dominated, except for large catchments with high riverine sediment load, which are river-dominated. Most deltas are wave-river dominated along the Pacific coast, with few examples of river-tide and wave-tide dominance. We predict Colombian deltas to become more wave and tide-dominated under river damming scenarios. In contrast, deforestation scenarios suggested virtually no future morphological changes.
How to cite: Paniagua-Arroyave, J. F., Nienhuis, J. H., and Dunn, F. E.: Potential Morphologic Responses of Tropical River Deltas in Colombia to Future Sediment Supply Scenarios, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3302, https://doi.org/10.5194/egusphere-egu21-3302, 2021.
EGU21-4441 | vPICO presentations | GM6.10
Analysis of tidal average saturated suspended sediment concentration of cohesive sediment in the Yangtze EstuaryJunyu Tao, Peng Hu, Wei Li, and Zhiguo He
It is generally believed that sediment erosion and deposition can’t occur simultaneously, which is also reflected in the classical Partheniades-Krone formulas used to calculate erosion and deposition flux. In this study, the erosion and deposition fluxes of cohesive sediment are integrated in the tidal period respectively, and when they are equal, the corresponding suspended cohesive sediment concentration is called ‘tidal average saturated concentration of cohesive sediment’. Theoretical analysis of the factors affecting the saturated concentration indicates that a large erosion coefficient results in a high saturated concentration level. The corresponding critical erosion and deposition shear stresses (i.e., τe and τd) at saturated concentration have many possibilities. Therefore, it is understandable that good agreement of suspended sediment concentration between simulation and observation have been obtained by adjusting τe and τd in the previous numerical simulation calibration. According to the relative magnitude of τe and τd at saturated concentration, the erosion and deposition fluxes of cohesive sediment can be divided into four situations: weak erosion (i.e., τe > τd), intense erosion (i.e., τe < τd), intense deposition (i.e., τe < τd), and weak deposition (i.e., τe > τd ). A two-dimensional numerical model is applied to calculate the temporal and spatial variation of the saturated concentration of cohesive sediment in the Yangtze Estuary. Simulation results shows the following findings. 1) The impact of the fraction of the kth size class in the surface (top) layer of bed material on erosion flux of non-uniform cohesive sediment is necessary to be considered. Otherwise, the calculated saturated concentration of cohesive sediment is greater than the measured. 2) The differences between saturated concentration and the field calculated/measured suspended sediment concentration can be applied to infer bed erosion/deposition characteristics to some extent, and compared it with the measured erosion/deposition result, which in turn verifies the values of τe and τd in the model. This finding provides insights for the following research on transport and diffusion of cohesive sediment in estuary and coastal areas.
How to cite: Tao, J., Hu, P., Li, W., and He, Z.: Analysis of tidal average saturated suspended sediment concentration of cohesive sediment in the Yangtze Estuary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4441, https://doi.org/10.5194/egusphere-egu21-4441, 2021.
It is generally believed that sediment erosion and deposition can’t occur simultaneously, which is also reflected in the classical Partheniades-Krone formulas used to calculate erosion and deposition flux. In this study, the erosion and deposition fluxes of cohesive sediment are integrated in the tidal period respectively, and when they are equal, the corresponding suspended cohesive sediment concentration is called ‘tidal average saturated concentration of cohesive sediment’. Theoretical analysis of the factors affecting the saturated concentration indicates that a large erosion coefficient results in a high saturated concentration level. The corresponding critical erosion and deposition shear stresses (i.e., τe and τd) at saturated concentration have many possibilities. Therefore, it is understandable that good agreement of suspended sediment concentration between simulation and observation have been obtained by adjusting τe and τd in the previous numerical simulation calibration. According to the relative magnitude of τe and τd at saturated concentration, the erosion and deposition fluxes of cohesive sediment can be divided into four situations: weak erosion (i.e., τe > τd), intense erosion (i.e., τe < τd), intense deposition (i.e., τe < τd), and weak deposition (i.e., τe > τd ). A two-dimensional numerical model is applied to calculate the temporal and spatial variation of the saturated concentration of cohesive sediment in the Yangtze Estuary. Simulation results shows the following findings. 1) The impact of the fraction of the kth size class in the surface (top) layer of bed material on erosion flux of non-uniform cohesive sediment is necessary to be considered. Otherwise, the calculated saturated concentration of cohesive sediment is greater than the measured. 2) The differences between saturated concentration and the field calculated/measured suspended sediment concentration can be applied to infer bed erosion/deposition characteristics to some extent, and compared it with the measured erosion/deposition result, which in turn verifies the values of τe and τd in the model. This finding provides insights for the following research on transport and diffusion of cohesive sediment in estuary and coastal areas.
How to cite: Tao, J., Hu, P., Li, W., and He, Z.: Analysis of tidal average saturated suspended sediment concentration of cohesive sediment in the Yangtze Estuary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4441, https://doi.org/10.5194/egusphere-egu21-4441, 2021.
EGU21-5140 | vPICO presentations | GM6.10
Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level riseFrances E. Dunn and Philip S. J. Minderhoud
As one of the largest deltas in the world, the Mekong delta is home to over 17 million people and supports internationally important agriculture. Recently deposited sediment compacts and causes subsidence in deltas, so they require regular sediment input to maintain elevation relative to sea level. These processes are complicated by human activities, which prevent sediment deposition indirectly through reducing fluvial sediment supply and directly through the construction of flood defence infrastructure on deltas, impeding floods which deliver sediment to the land. Additionally, anthropogenic activities increase the rate of subsidence through the extraction of groundwater and other land-use practices.
This research shows the potential for fluvial sediment delivery to compensate for sea-level rise and subsidence in the Mekong delta over the 21st century. We use detailed elevation data and subsidence scenarios in combination with regional sea-level rise and fluvial sediment flux projections to quantify the potential for maintaining elevation relative to sea level in the Mekong delta. We present four examples of localised sedimentation scenarios in specific areas, for which we quantified the potential effectiveness of fluvial sediment deposition for offsetting relative sea-level rise. The presented sediment-based adaptation strategies are complicated by existing land use, therefore a change in water and sediment management is required to effectively use natural resources and employ these adaptation methods. The presented approach could be an exemplar to assess sedimentation strategy feasibility in other delta systems worldwide that are under threat from sea-level rise.
How to cite: Dunn, F. E. and Minderhoud, P. S. J.: Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level rise, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5140, https://doi.org/10.5194/egusphere-egu21-5140, 2021.
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As one of the largest deltas in the world, the Mekong delta is home to over 17 million people and supports internationally important agriculture. Recently deposited sediment compacts and causes subsidence in deltas, so they require regular sediment input to maintain elevation relative to sea level. These processes are complicated by human activities, which prevent sediment deposition indirectly through reducing fluvial sediment supply and directly through the construction of flood defence infrastructure on deltas, impeding floods which deliver sediment to the land. Additionally, anthropogenic activities increase the rate of subsidence through the extraction of groundwater and other land-use practices.
This research shows the potential for fluvial sediment delivery to compensate for sea-level rise and subsidence in the Mekong delta over the 21st century. We use detailed elevation data and subsidence scenarios in combination with regional sea-level rise and fluvial sediment flux projections to quantify the potential for maintaining elevation relative to sea level in the Mekong delta. We present four examples of localised sedimentation scenarios in specific areas, for which we quantified the potential effectiveness of fluvial sediment deposition for offsetting relative sea-level rise. The presented sediment-based adaptation strategies are complicated by existing land use, therefore a change in water and sediment management is required to effectively use natural resources and employ these adaptation methods. The presented approach could be an exemplar to assess sedimentation strategy feasibility in other delta systems worldwide that are under threat from sea-level rise.
How to cite: Dunn, F. E. and Minderhoud, P. S. J.: Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level rise, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5140, https://doi.org/10.5194/egusphere-egu21-5140, 2021.
EGU21-6964 | vPICO presentations | GM6.10
A study on the dynamic process of fluid mud and its effect on siltation in the Yangtze Estuary Deepwater ChannelYue Li, Peng Hu, and Ji Li
The Yangtze Estuary Deepwater Channel Project has brought great economic and social benefits since its completion, but the siltation problem is still worthy of attention. In order to investigate the mechanisms of fluid mud in the estuary and to study the influence of fluid mud on siltation in the Yangtze Estuary Deepwater Channel, a two-dimensional physically-enhanced two-layer flow model will be developed in this paper. The model includes two series of governing equations which are about environment fluid and fluid mud, respectively. The model is based on the unstructured grid, and the governing equations are discretized by the finite volume method, and the improved LTS/GMaTS technology is used to improve the computational efficiency. Firstly, an experiment that the fluid mud was flowing underwater along a gentle slope is reconstructed by the two-layer model. It shows the ability of the model to describe the simple movement of fluid mud. Secondly, the model is applied to Yangtze Estuary. Without the fluid mud layer, the model can be simplified as a tide-current model. The reliability of the tidal current and tide level is verified, and it means the model can describe the tide accurately. Based on this, the process of formation, transport, and break-down of fluid mud is simulated and its effect on the siltation in the Yangtze Estuary Deepwater Channel is estimated.
How to cite: Li, Y., Hu, P., and Li, J.: A study on the dynamic process of fluid mud and its effect on siltation in the Yangtze Estuary Deepwater Channel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6964, https://doi.org/10.5194/egusphere-egu21-6964, 2021.
The Yangtze Estuary Deepwater Channel Project has brought great economic and social benefits since its completion, but the siltation problem is still worthy of attention. In order to investigate the mechanisms of fluid mud in the estuary and to study the influence of fluid mud on siltation in the Yangtze Estuary Deepwater Channel, a two-dimensional physically-enhanced two-layer flow model will be developed in this paper. The model includes two series of governing equations which are about environment fluid and fluid mud, respectively. The model is based on the unstructured grid, and the governing equations are discretized by the finite volume method, and the improved LTS/GMaTS technology is used to improve the computational efficiency. Firstly, an experiment that the fluid mud was flowing underwater along a gentle slope is reconstructed by the two-layer model. It shows the ability of the model to describe the simple movement of fluid mud. Secondly, the model is applied to Yangtze Estuary. Without the fluid mud layer, the model can be simplified as a tide-current model. The reliability of the tidal current and tide level is verified, and it means the model can describe the tide accurately. Based on this, the process of formation, transport, and break-down of fluid mud is simulated and its effect on the siltation in the Yangtze Estuary Deepwater Channel is estimated.
How to cite: Li, Y., Hu, P., and Li, J.: A study on the dynamic process of fluid mud and its effect on siltation in the Yangtze Estuary Deepwater Channel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6964, https://doi.org/10.5194/egusphere-egu21-6964, 2021.
EGU21-8290 | vPICO presentations | GM6.10
Large-scale scour in response to tidal dominance in estuariesJasper Leuven, Daan van Keulen, Jaap Nienhuis, Alberto Canestrelli, and Ton Hoitink
Channel beds in estuaries and deltas often exhibit a local depth maximum at a location close to the coast. There are two known causes of large-scale (i.e. >10 river widths along-channel) channel bed scours: width constriction and draw down during river discharge extremes, both creating a local flow acceleration. Here, we systematically investigate a potential third mechanism. We study the effect of tidal dominance on the equilibrium channel bed in estuaries with a 1D-morphodynamic model. In estuaries, a morphodynamic equibrium is reached when the net (seaward) transport matches the upstream supply along the entire reach. The residual (river) current and river-tide interactions create seaward transport. Herein, river-tide interactions represent the seaward advection of tide-induced suspended sediment by the river flow. Tidal asymmetry typically creates landward transport. The main reason for scour formation is the amplification of tidal flow through funnelling of tidal energy. Only for a scouring profile the drop in river induced current magnitude reduces the river-tide interaction term, so that the net sediment transport matches the upstream sediment transport. When tidal influence is relatively large, and when channel convergence is strong, a equilibrium is only obtained with a scouring profile. We propose a predictor dependent on the width convergence, quantified as SB, and on the ratio between the specific peak tidal discharge at the mouth and the specific river discharge at the landward boundary (qtide/qriver). Scours develop if (qtide/qriver)/SB exceeds 0.3. These results are independent of scale and allow the prediction of scour in estuaries under future changes.
How to cite: Leuven, J., van Keulen, D., Nienhuis, J., Canestrelli, A., and Hoitink, T.: Large-scale scour in response to tidal dominance in estuaries, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8290, https://doi.org/10.5194/egusphere-egu21-8290, 2021.
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Channel beds in estuaries and deltas often exhibit a local depth maximum at a location close to the coast. There are two known causes of large-scale (i.e. >10 river widths along-channel) channel bed scours: width constriction and draw down during river discharge extremes, both creating a local flow acceleration. Here, we systematically investigate a potential third mechanism. We study the effect of tidal dominance on the equilibrium channel bed in estuaries with a 1D-morphodynamic model. In estuaries, a morphodynamic equibrium is reached when the net (seaward) transport matches the upstream supply along the entire reach. The residual (river) current and river-tide interactions create seaward transport. Herein, river-tide interactions represent the seaward advection of tide-induced suspended sediment by the river flow. Tidal asymmetry typically creates landward transport. The main reason for scour formation is the amplification of tidal flow through funnelling of tidal energy. Only for a scouring profile the drop in river induced current magnitude reduces the river-tide interaction term, so that the net sediment transport matches the upstream sediment transport. When tidal influence is relatively large, and when channel convergence is strong, a equilibrium is only obtained with a scouring profile. We propose a predictor dependent on the width convergence, quantified as SB, and on the ratio between the specific peak tidal discharge at the mouth and the specific river discharge at the landward boundary (qtide/qriver). Scours develop if (qtide/qriver)/SB exceeds 0.3. These results are independent of scale and allow the prediction of scour in estuaries under future changes.
How to cite: Leuven, J., van Keulen, D., Nienhuis, J., Canestrelli, A., and Hoitink, T.: Large-scale scour in response to tidal dominance in estuaries, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8290, https://doi.org/10.5194/egusphere-egu21-8290, 2021.
EGU21-9173 | vPICO presentations | GM6.10
Flow and Stratification in a Bedrock Confined EstuaryAmanda Wild and Eva Kwoll
EGU21-9498 | vPICO presentations | GM6.10 | Highlight
Effects of mean sea level rise and tidal flat growth on tides and storm surge events in the Elbe estuaryTara Mahavadi, Elisabeth Rudolph, Rita Seiffert, and Norbert Winkel
Future mean sea level rise will influence tidal dynamics and storm surge events in estuaries. The bathymetry in estuaries and coastal areas will also be affected by mean sea level rise, since it is in a morphodynamic equilibrium with hydrodynamic forces. Tidal flats, which are an important component of coastal protection, will grow to a certain extent with mean sea level rise in case of sufficient sediment availability.
With the help of a highly resolved hydrodynamic-numerical model of the German Bight (North Sea), we analyse the potential influence of mean sea level rise and vertical growth of tidal flats on tidal dynamics and storm surge events in the Elbe estuary.
The results show an increase of tidal amplitude and storm surge water levels due to mean sea level rise. A bathymetric rise of tidal flats in the German Bight and the mouth of the Elbe estuary leads to a decrease in storm surge water level and tidal amplitude compared to the scenario with sole mean sea level rise without a change in bathymetry. Further analyses show, how geometric parameters of the Elbe estuary are changing due to mean sea level rise and tidal flat growth. These changes in geometry influence tidal dynamics and can therefore be an explanation for the observed changes in tidal amplitude and storm surge water levels.
These findings enable a better understanding of future changes in the Elbe estuary and support coastal managers in decision making processes concerning adaptation options to reduce the impacts of climate change.
How to cite: Mahavadi, T., Rudolph, E., Seiffert, R., and Winkel, N.: Effects of mean sea level rise and tidal flat growth on tides and storm surge events in the Elbe estuary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9498, https://doi.org/10.5194/egusphere-egu21-9498, 2021.
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Future mean sea level rise will influence tidal dynamics and storm surge events in estuaries. The bathymetry in estuaries and coastal areas will also be affected by mean sea level rise, since it is in a morphodynamic equilibrium with hydrodynamic forces. Tidal flats, which are an important component of coastal protection, will grow to a certain extent with mean sea level rise in case of sufficient sediment availability.
With the help of a highly resolved hydrodynamic-numerical model of the German Bight (North Sea), we analyse the potential influence of mean sea level rise and vertical growth of tidal flats on tidal dynamics and storm surge events in the Elbe estuary.
The results show an increase of tidal amplitude and storm surge water levels due to mean sea level rise. A bathymetric rise of tidal flats in the German Bight and the mouth of the Elbe estuary leads to a decrease in storm surge water level and tidal amplitude compared to the scenario with sole mean sea level rise without a change in bathymetry. Further analyses show, how geometric parameters of the Elbe estuary are changing due to mean sea level rise and tidal flat growth. These changes in geometry influence tidal dynamics and can therefore be an explanation for the observed changes in tidal amplitude and storm surge water levels.
These findings enable a better understanding of future changes in the Elbe estuary and support coastal managers in decision making processes concerning adaptation options to reduce the impacts of climate change.
How to cite: Mahavadi, T., Rudolph, E., Seiffert, R., and Winkel, N.: Effects of mean sea level rise and tidal flat growth on tides and storm surge events in the Elbe estuary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9498, https://doi.org/10.5194/egusphere-egu21-9498, 2021.
EGU21-13180 | vPICO presentations | GM6.10 | Highlight
A global database of flood-protection levees on river deltas (openDELvE)Joey O'Dell, Jaap H. Nienhuis, Jana R. Cox, Douglas A. Edmonds, and Paolo Scussolini
Global flood modelling requires standardised global flood-protection levee datasets. Current datasets, however, are generally confined to territorial boundaries (national datasets) and are scarcely made public. Here we report on our effort to collect and standardise flood-protection levee data for river deltas from various sources to create a single, open source and FAIR-aligned global dynamic evolving river levee data environment (openDELvE).
openDELvE aggregates data from national databases (including the USACE National Levee Database, and the UK EA Asset Information Management System, amongst others) as well as data collected from reports, maps, and satellite imagery. We report primarily the land areas that the levees have been designed to protect, and where additional data is available, the location of levees and unified attributes. openDELvE currently contains 1601 mapped leveed area polygons distributed over 152 deltas, covering 28% of globally defined delta area. Out of the 152 deltas, which cover a total delta area of 239,043 km2, the levees registered in the database protect a land area of 42,342 km2. Additionally, more extensive data has been collected from a selection of freely accessible public national databases (mostly the UK and USA, and some of Australia) spanning 5,089 km of levees with additional unified attributes (e.g. levee height, crest width, construction material), and a semi-automated process is being used to extend and develop this layer.
The data is published aligned to FAIR-standards and is open-source, with an interactive viewing platform to supplement the data which is targeted for use in global river delta modelling and research. The viewing platform for the database incorporates a community-driven revision tool to encourage ongoing improvement and refinement of delta levee data, which can be extended to future projects as required.
How to cite: O'Dell, J., Nienhuis, J. H., Cox, J. R., Edmonds, D. A., and Scussolini, P.: A global database of flood-protection levees on river deltas (openDELvE), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13180, https://doi.org/10.5194/egusphere-egu21-13180, 2021.
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Global flood modelling requires standardised global flood-protection levee datasets. Current datasets, however, are generally confined to territorial boundaries (national datasets) and are scarcely made public. Here we report on our effort to collect and standardise flood-protection levee data for river deltas from various sources to create a single, open source and FAIR-aligned global dynamic evolving river levee data environment (openDELvE).
openDELvE aggregates data from national databases (including the USACE National Levee Database, and the UK EA Asset Information Management System, amongst others) as well as data collected from reports, maps, and satellite imagery. We report primarily the land areas that the levees have been designed to protect, and where additional data is available, the location of levees and unified attributes. openDELvE currently contains 1601 mapped leveed area polygons distributed over 152 deltas, covering 28% of globally defined delta area. Out of the 152 deltas, which cover a total delta area of 239,043 km2, the levees registered in the database protect a land area of 42,342 km2. Additionally, more extensive data has been collected from a selection of freely accessible public national databases (mostly the UK and USA, and some of Australia) spanning 5,089 km of levees with additional unified attributes (e.g. levee height, crest width, construction material), and a semi-automated process is being used to extend and develop this layer.
The data is published aligned to FAIR-standards and is open-source, with an interactive viewing platform to supplement the data which is targeted for use in global river delta modelling and research. The viewing platform for the database incorporates a community-driven revision tool to encourage ongoing improvement and refinement of delta levee data, which can be extended to future projects as required.
How to cite: O'Dell, J., Nienhuis, J. H., Cox, J. R., Edmonds, D. A., and Scussolini, P.: A global database of flood-protection levees on river deltas (openDELvE), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13180, https://doi.org/10.5194/egusphere-egu21-13180, 2021.
EGU21-13640 | vPICO presentations | GM6.10
The Future of a Cold Regions Deltaic Ecosystem Influenced by Multiple Hydrological StressorsDaniel Peters, Wendy Monk, and Donald Baird
The Peace-Athabasca Delta (PAD) in one of the largest (~6000 km2) freshwater deltaic ecosystem in the world. This low relief, deltaic floodplain formed at the confluence of the Peace-Athabasca-Birch rivers the west end of Lake Athabasca in northwestern Canada. Small changes in water level/depth have important implications for surface water connectivity and associated habitat quality The floodplains contain more than 1000 wetland-lake basins with varying degrees of connectivity to the main flow system. Hydroperiod is influenced by occasional ice-jam and open-water inundations that recharge wetland basins. This culturally important and biologically rich delta is a Ramsar Convention Wetland Site of International Importance, and is a key feature of the Wood Buffalo National Park (WBNP) that is listed as a UNESCO World Heritage Site. The PAD ecosystem is influenced by contributing basin and local scale hydrological stressors from flow regulation (eg, hydroelectric dam, weirs), water and land use (eg, oil sands mining) and climate change.
Growing concern regarding increased cumulative effects on the delta led Indigenous Peoples petitioning UNESCO World Heritage Committee (WNC) to reassess the protection status of the park. The WBNP Action Plan was developed to address 17 UNESCO WHC recommendations to ensure maintenance of Outstanding Universal Value of the Park. One key set of recommendations is to: 1) Conduct environmental flows assessments, to the highest international standard, in order to identify water flows needed to sustain the ecological functioning of the PAD under current and projected development and climate change; 2) Establish adequate baseline hydrological information for PAD assessments.
A significant scientific effort has been invested in the last four decades, particularly since 2010, in improving our understanding the relationship between streamflow, landscape controls and aquatic ecology in this cold-regions delta. This information is key to assess historical and present states, learn from past development to inform planned development, and prepare for anticipated future hydro-ecological changes. However, several key questions arise regarding what is the best approach to preparing for the future and managing such a complex system, what management options are possible within an environmental flow framework given known hydrological stressors, and what future ecosystem state does society want for the delta. The goal of this presentation focused on the PAD is threefold: i) Provide an overview of major hydro-ecological research and water management; ii) Assess the potential applicability of riverine environmental flow frameworks to deltaic floodplain environments; and iii) Explore the development of an environmental flow/water level framework and tools necessary to assess and manage changes to the aquatic ecology of this internationally important deltaic ecosystem.
How to cite: Peters, D., Monk, W., and Baird, D.: The Future of a Cold Regions Deltaic Ecosystem Influenced by Multiple Hydrological Stressors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13640, https://doi.org/10.5194/egusphere-egu21-13640, 2021.
The Peace-Athabasca Delta (PAD) in one of the largest (~6000 km2) freshwater deltaic ecosystem in the world. This low relief, deltaic floodplain formed at the confluence of the Peace-Athabasca-Birch rivers the west end of Lake Athabasca in northwestern Canada. Small changes in water level/depth have important implications for surface water connectivity and associated habitat quality The floodplains contain more than 1000 wetland-lake basins with varying degrees of connectivity to the main flow system. Hydroperiod is influenced by occasional ice-jam and open-water inundations that recharge wetland basins. This culturally important and biologically rich delta is a Ramsar Convention Wetland Site of International Importance, and is a key feature of the Wood Buffalo National Park (WBNP) that is listed as a UNESCO World Heritage Site. The PAD ecosystem is influenced by contributing basin and local scale hydrological stressors from flow regulation (eg, hydroelectric dam, weirs), water and land use (eg, oil sands mining) and climate change.
Growing concern regarding increased cumulative effects on the delta led Indigenous Peoples petitioning UNESCO World Heritage Committee (WNC) to reassess the protection status of the park. The WBNP Action Plan was developed to address 17 UNESCO WHC recommendations to ensure maintenance of Outstanding Universal Value of the Park. One key set of recommendations is to: 1) Conduct environmental flows assessments, to the highest international standard, in order to identify water flows needed to sustain the ecological functioning of the PAD under current and projected development and climate change; 2) Establish adequate baseline hydrological information for PAD assessments.
A significant scientific effort has been invested in the last four decades, particularly since 2010, in improving our understanding the relationship between streamflow, landscape controls and aquatic ecology in this cold-regions delta. This information is key to assess historical and present states, learn from past development to inform planned development, and prepare for anticipated future hydro-ecological changes. However, several key questions arise regarding what is the best approach to preparing for the future and managing such a complex system, what management options are possible within an environmental flow framework given known hydrological stressors, and what future ecosystem state does society want for the delta. The goal of this presentation focused on the PAD is threefold: i) Provide an overview of major hydro-ecological research and water management; ii) Assess the potential applicability of riverine environmental flow frameworks to deltaic floodplain environments; and iii) Explore the development of an environmental flow/water level framework and tools necessary to assess and manage changes to the aquatic ecology of this internationally important deltaic ecosystem.
How to cite: Peters, D., Monk, W., and Baird, D.: The Future of a Cold Regions Deltaic Ecosystem Influenced by Multiple Hydrological Stressors, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13640, https://doi.org/10.5194/egusphere-egu21-13640, 2021.
EGU21-16281 | vPICO presentations | GM6.10
Pathways of change in the socio-shysical dynamics of the Western Indian Ocean deltasPaolo Paron, Stephanie Duvail, Olivier Hamerlynck, Dominque Hervé, Dinis Juizo, Simon Mwansasu, Wanja Nyingi, and Laurent Robison
We present the output of a research combining field based, expert knowledge and remote sensing, based on Google Earth Engine, aimed at the identification of the rates of changes and pathways during the past 35 years, in four Western Indian Ocean River Catchments and Deltas: Tana River in Kenya, Rufiji River in Tanzania, Limpopo River in Mozambique and Betsiboka River in Madagascar. These findings are a set of preliminary results of the collaborative and multidisciplinary effort produced within the GDRI-Sud network DELTAS and as a follow-up of the West Indian Ocean Deltas Exchange and Research network (WIODER) project that brought together the National Museum of Kenya, , University of Dar Es Salaam in Tanzania, University Eduardo Mondlane in Mozambique, Centre National de Recherches sur l'Environnement in Madagascar, University of Southampton in UK, IHE Delft in the Netherlands, Institut de Recherche pour le Développement in France, and International Development Research Centre in Canada and Kenya.
We highlight the similarities in the physical environment and, where possible, also in the socio-economic-political environments that are leading the current changes, potentially affecting resilience of the local population and their sustainable development.
We focused on the substantial changes in the following aspects: precipitation seasonality, flooding patterns and frequency, land cover, dry forest cover, mangrove cover, crop production, fish population, human population, human migration flow, frequency of human conflicts within the delta population.
The observed changes call for reflection given the IPCC projections in climate towards an aridification of the Southern Africa river basins and a wetter condition in the Eastern Africa region. Some signals of these climatic forecast are already recorded in both regions and will be explored in the DIDEM project.
How to cite: Paron, P., Duvail, S., Hamerlynck, O., Hervé, D., Juizo, D., Mwansasu, S., Nyingi, W., and Robison, L.: Pathways of change in the socio-shysical dynamics of the Western Indian Ocean deltas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16281, https://doi.org/10.5194/egusphere-egu21-16281, 2021.
We present the output of a research combining field based, expert knowledge and remote sensing, based on Google Earth Engine, aimed at the identification of the rates of changes and pathways during the past 35 years, in four Western Indian Ocean River Catchments and Deltas: Tana River in Kenya, Rufiji River in Tanzania, Limpopo River in Mozambique and Betsiboka River in Madagascar. These findings are a set of preliminary results of the collaborative and multidisciplinary effort produced within the GDRI-Sud network DELTAS and as a follow-up of the West Indian Ocean Deltas Exchange and Research network (WIODER) project that brought together the National Museum of Kenya, , University of Dar Es Salaam in Tanzania, University Eduardo Mondlane in Mozambique, Centre National de Recherches sur l'Environnement in Madagascar, University of Southampton in UK, IHE Delft in the Netherlands, Institut de Recherche pour le Développement in France, and International Development Research Centre in Canada and Kenya.
We highlight the similarities in the physical environment and, where possible, also in the socio-economic-political environments that are leading the current changes, potentially affecting resilience of the local population and their sustainable development.
We focused on the substantial changes in the following aspects: precipitation seasonality, flooding patterns and frequency, land cover, dry forest cover, mangrove cover, crop production, fish population, human population, human migration flow, frequency of human conflicts within the delta population.
The observed changes call for reflection given the IPCC projections in climate towards an aridification of the Southern Africa river basins and a wetter condition in the Eastern Africa region. Some signals of these climatic forecast are already recorded in both regions and will be explored in the DIDEM project.
How to cite: Paron, P., Duvail, S., Hamerlynck, O., Hervé, D., Juizo, D., Mwansasu, S., Nyingi, W., and Robison, L.: Pathways of change in the socio-shysical dynamics of the Western Indian Ocean deltas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16281, https://doi.org/10.5194/egusphere-egu21-16281, 2021.
EGU21-16435 | vPICO presentations | GM6.10
Intertidal floodplain controls on centennial-scale morphological channel developmentReinier Schrijvershof, Bas van Maren, Bart Vermeulen, and Ton Hoitink
Intertidal areas disappear in deltas worldwide because of land reclamations. This greatly impacts delta morphology because the presence and physiological characteristics of intertidal areas determine the tidal regime and, as a result, residual sediment transport patterns in tidal basins. Understanding how the interaction between intertidal areas and channels in tidal basins influence morphodynamics is therefore important to predict morphological development and to assess the resilience of delta’s to changing boundary conditions.
In the Ems estuary (The Netherlands), the gradual embankment of a large intertidal embayment altered the planform and cross-sectional geometry of the estuary, leading to changes in the tidal regime and associated residual sediment transport patterns. As early as 1952, it was already suggested that these changes eventually caused a shift towards an alternative historical development of the geometric configuration of the channels; from a multiple to a single channel system.
This study shows through centennial-scale morphological modelling that the observed system shift can be hind-casted, while conserving model validity by comparison to the observed gross morphodynamics trends. The results indicate that the system shift is indeed driven by land reclamations. This provides a unique case to study the processes leading to the observed developments and evaluate the value of tidal-asymmetry based stability relationships to predict regime shifts in estuarine development.
How to cite: Schrijvershof, R., van Maren, B., Vermeulen, B., and Hoitink, T.: Intertidal floodplain controls on centennial-scale morphological channel development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16435, https://doi.org/10.5194/egusphere-egu21-16435, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Intertidal areas disappear in deltas worldwide because of land reclamations. This greatly impacts delta morphology because the presence and physiological characteristics of intertidal areas determine the tidal regime and, as a result, residual sediment transport patterns in tidal basins. Understanding how the interaction between intertidal areas and channels in tidal basins influence morphodynamics is therefore important to predict morphological development and to assess the resilience of delta’s to changing boundary conditions.
In the Ems estuary (The Netherlands), the gradual embankment of a large intertidal embayment altered the planform and cross-sectional geometry of the estuary, leading to changes in the tidal regime and associated residual sediment transport patterns. As early as 1952, it was already suggested that these changes eventually caused a shift towards an alternative historical development of the geometric configuration of the channels; from a multiple to a single channel system.
This study shows through centennial-scale morphological modelling that the observed system shift can be hind-casted, while conserving model validity by comparison to the observed gross morphodynamics trends. The results indicate that the system shift is indeed driven by land reclamations. This provides a unique case to study the processes leading to the observed developments and evaluate the value of tidal-asymmetry based stability relationships to predict regime shifts in estuarine development.
How to cite: Schrijvershof, R., van Maren, B., Vermeulen, B., and Hoitink, T.: Intertidal floodplain controls on centennial-scale morphological channel development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16435, https://doi.org/10.5194/egusphere-egu21-16435, 2021.
EGU21-16444 | vPICO presentations | GM6.10
Binding the Ganges-Brahmaputra-Meghna Braids: A review of geomorphic change in the world's largest deltaAmelia Paszkowski, Steven Goodbred Jr, Edoardo Borgomeo, M. Shah Alam Khan, and Jim W. Hall
The Ganges-Brahmaputra-Meghna (GBM) rivers deliver the greatest sediment flux to the world’s oceans, generating the Earth’s largest delta system, which is home to over 170 million people. Despite its scale and complexity, the GBM delta system remains a relatively under-researched region, with geomorphic dynamics often overlooked in studies of its vulnerability. A synthesis of these research efforts remains absent, resulting in most geomorphic studies being spatially, temporally, and topically fragmented. In this research, we therefore bind these studies together, providing a holistic, delta-wide account of the GBM’s prevailing dynamics and evolution, as well as identify key areas for future research. We built a sample of 427 peer-reviewed articles published from 1863 to 2020, and applied the Driver-Pressure-State-Impact-Response (DPSIR) framework to the geomorphic dynamics of the delta. We find that the delta has been responding to complex natural and anthropogenic perturbations in the form of subsidence, shifting river flows and sedimentation patterns. These processes subsequently impact on the extent and magnitude of flooding, result in losses to biodiversity, and most critically, severely disrupt local livelihoods. Amongst other key systemic gaps identified in this research, this study finds that (i) the GBM delta is typically assessed and modelled as a physical system with limited recognition of the dynamic interaction with human actions; and (ii) only 5% of studies assessed how the morphology of the delta may change in the future. Ultimately, this systematic review argues that although climate change and sea-level rise remain major concerns for the delta in the coming decades, multi-scale management and policy decisions have a more direct influence on the future geomorphic balance of the GBM delta.
How to cite: Paszkowski, A., Goodbred Jr, S., Borgomeo, E., Khan, M. S. A., and W. Hall, J.: Binding the Ganges-Brahmaputra-Meghna Braids: A review of geomorphic change in the world's largest delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16444, https://doi.org/10.5194/egusphere-egu21-16444, 2021.
The Ganges-Brahmaputra-Meghna (GBM) rivers deliver the greatest sediment flux to the world’s oceans, generating the Earth’s largest delta system, which is home to over 170 million people. Despite its scale and complexity, the GBM delta system remains a relatively under-researched region, with geomorphic dynamics often overlooked in studies of its vulnerability. A synthesis of these research efforts remains absent, resulting in most geomorphic studies being spatially, temporally, and topically fragmented. In this research, we therefore bind these studies together, providing a holistic, delta-wide account of the GBM’s prevailing dynamics and evolution, as well as identify key areas for future research. We built a sample of 427 peer-reviewed articles published from 1863 to 2020, and applied the Driver-Pressure-State-Impact-Response (DPSIR) framework to the geomorphic dynamics of the delta. We find that the delta has been responding to complex natural and anthropogenic perturbations in the form of subsidence, shifting river flows and sedimentation patterns. These processes subsequently impact on the extent and magnitude of flooding, result in losses to biodiversity, and most critically, severely disrupt local livelihoods. Amongst other key systemic gaps identified in this research, this study finds that (i) the GBM delta is typically assessed and modelled as a physical system with limited recognition of the dynamic interaction with human actions; and (ii) only 5% of studies assessed how the morphology of the delta may change in the future. Ultimately, this systematic review argues that although climate change and sea-level rise remain major concerns for the delta in the coming decades, multi-scale management and policy decisions have a more direct influence on the future geomorphic balance of the GBM delta.
How to cite: Paszkowski, A., Goodbred Jr, S., Borgomeo, E., Khan, M. S. A., and W. Hall, J.: Binding the Ganges-Brahmaputra-Meghna Braids: A review of geomorphic change in the world's largest delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16444, https://doi.org/10.5194/egusphere-egu21-16444, 2021.
GM7.6 – Cold Regions Geomorphology
EGU21-9198 | vPICO presentations | GM7.6
Chronology of the deglaciation of the Zackenberg area, NE GreenlandJulia Nieves Garcia de Oteyza de Ciria, Marc Oliva, David Palacios, Jose Maria Fernández-Fernández, Irene Schimmelpfennig, Nuria Andrés, Dermot Antoniades, Hanne Christiansen, Ole Humlum, Laëtitia Léanni, Jesús Ruiz-Fernández, and Vincent Jomelli
The Greenland Ice Sheet (GrIS) plays a key role in the global climate system. Its response to recent warming concerns the scientific community due to its potential contribution to the global sea-level rise, oceanographic changes and the related heat distribution in the atmosphere. Therefore, a better understanding of the GrIS response to past glacial oscillations can provide insights into its sensitivity to rapidly changing climates. Past natural GrIS dynamics are still poorly constrained, and there are important knowledge gaps in the spatio-temporal pattern of its past fluctuations, especially on the NE margins, in response to climate variability. Here, we present new records of past GRIS extents and a detailed space-time reconstruction of the deglaciation process in the Zackenberg Valley (74ºN, 20ºE), NE Greenland, based on geomorphological mapping combined with a new dataset of 39 10Be cosmic-ray exposure (CRE) ages of moraine boulders, polished surfaces, and erratic boulders. Our dataset records glacial oscillations from the Last Glacial Cycle to the Early Holocene. Geomorphic evidence at the summit surfaces reveal that glaciers were significantly thicker (>800 m) at ca. 80 ka, when valleys and fjords were ice-covered and only the highest peaks remained ice-free. The Zackenberg outlet glacier must have been slightly smaller during the Last Glacial Maximum, although no glacial records of this period were found. Samples from moraine boulders indicate rapid and massive deglaciation of the Zackenberg Valley slopes by ca. 14 ka, during the Bølling-Allerød interstadial. Ice thinning exposed the upper and intermediate slopes surrounding the valley floor, while stabilization phases within the long-term glacial retreat favoured the development of several moraine ridges. At the end of the Younger Dryas, by ca. 12 ka, a glacier readvance favoured the development of the lowest moraine ridges of the slopes, connected with the outermost moraine system on the valley floor. Within the limits of this moraine, a debris-covered glacier formed due to the intense paraglacial readjustment of rock slopes and moraines triggered by glacier thinning. This process favoured the degradation of the moraine ridges on the slopes, supplying large amounts of debris to the shrinking glacier. By ~10.5 ka, the last remnants of glacial ice disappeared from the Zackenberg Valley floor, exposing polished bedrock outcrops and leaving scattered erratic boulders. Higher temperatures also favoured the irregular collapse of the debris-covered glacier, transforming this area into a hummocky terrain. This deglaciation chronology shows a particularly intense recession during the Bølling-Allerød and Early Holocene, a path that is broadly similar to that observed in other sites across NE Greenland.
How to cite: Garcia de Oteyza de Ciria, J. N., Oliva, M., Palacios, D., Fernández-Fernández, J. M., Schimmelpfennig, I., Andrés, N., Antoniades, D., Christiansen, H., Humlum, O., Léanni, L., Ruiz-Fernández, J., and Jomelli, V.: Chronology of the deglaciation of the Zackenberg area, NE Greenland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9198, https://doi.org/10.5194/egusphere-egu21-9198, 2021.
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The Greenland Ice Sheet (GrIS) plays a key role in the global climate system. Its response to recent warming concerns the scientific community due to its potential contribution to the global sea-level rise, oceanographic changes and the related heat distribution in the atmosphere. Therefore, a better understanding of the GrIS response to past glacial oscillations can provide insights into its sensitivity to rapidly changing climates. Past natural GrIS dynamics are still poorly constrained, and there are important knowledge gaps in the spatio-temporal pattern of its past fluctuations, especially on the NE margins, in response to climate variability. Here, we present new records of past GRIS extents and a detailed space-time reconstruction of the deglaciation process in the Zackenberg Valley (74ºN, 20ºE), NE Greenland, based on geomorphological mapping combined with a new dataset of 39 10Be cosmic-ray exposure (CRE) ages of moraine boulders, polished surfaces, and erratic boulders. Our dataset records glacial oscillations from the Last Glacial Cycle to the Early Holocene. Geomorphic evidence at the summit surfaces reveal that glaciers were significantly thicker (>800 m) at ca. 80 ka, when valleys and fjords were ice-covered and only the highest peaks remained ice-free. The Zackenberg outlet glacier must have been slightly smaller during the Last Glacial Maximum, although no glacial records of this period were found. Samples from moraine boulders indicate rapid and massive deglaciation of the Zackenberg Valley slopes by ca. 14 ka, during the Bølling-Allerød interstadial. Ice thinning exposed the upper and intermediate slopes surrounding the valley floor, while stabilization phases within the long-term glacial retreat favoured the development of several moraine ridges. At the end of the Younger Dryas, by ca. 12 ka, a glacier readvance favoured the development of the lowest moraine ridges of the slopes, connected with the outermost moraine system on the valley floor. Within the limits of this moraine, a debris-covered glacier formed due to the intense paraglacial readjustment of rock slopes and moraines triggered by glacier thinning. This process favoured the degradation of the moraine ridges on the slopes, supplying large amounts of debris to the shrinking glacier. By ~10.5 ka, the last remnants of glacial ice disappeared from the Zackenberg Valley floor, exposing polished bedrock outcrops and leaving scattered erratic boulders. Higher temperatures also favoured the irregular collapse of the debris-covered glacier, transforming this area into a hummocky terrain. This deglaciation chronology shows a particularly intense recession during the Bølling-Allerød and Early Holocene, a path that is broadly similar to that observed in other sites across NE Greenland.
How to cite: Garcia de Oteyza de Ciria, J. N., Oliva, M., Palacios, D., Fernández-Fernández, J. M., Schimmelpfennig, I., Andrés, N., Antoniades, D., Christiansen, H., Humlum, O., Léanni, L., Ruiz-Fernández, J., and Jomelli, V.: Chronology of the deglaciation of the Zackenberg area, NE Greenland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9198, https://doi.org/10.5194/egusphere-egu21-9198, 2021.
EGU21-15752 | vPICO presentations | GM7.6
Geomorphology, hydrology, and chronology of Early Holocene jökulhlaups along the Hvítá River and Gullfoss waterfall, IcelandGreta Wells, Sheryl Luzzadder-Beach, Timothy Beach, Thorsteinn Saemundsson, and Andrew Dugmore
Glacial outburst floods (jökulhlaups) have occurred across Earth throughout the Quaternary, often leaving a geomorphologic, sedimentological, and climatic legacy that extends far beyond the source region and can persist for millennia. Furthermore, they pose an increasing geohazard in glaciated landscapes worldwide due to climate-driven ice retreat. Iceland experiences more frequent jökulhlaups than nearly anywhere on Earth, though most research focuses on floods triggered by subglacial volcanic and geothermal activity. However, abundant evidence also exists for non-volcanogenic floods from proglacial lakes, which may serve as a better analogue for most global jökulhlaups.
As the Icelandic Ice Sheet retreated across Iceland in the Late Pleistocene-Early Holocene, meltwater lakes formed at ice margins and periodically drained in jökulhlaups. Some of the most catastrophic floods drained from ice-dammed Glacial Lake Kjölur, surging across southwestern Iceland from the interior highlands to the Atlantic Ocean. These floods left extensive geomorphologic evidence along the modern-day course of the Hvítá River, including canyon systems, scoured bedrock, boulder deposits, and Gullfoss—Iceland’s most famous waterfall. The largest events reached an estimated peak discharge on the order of 105 m3 s-1, ranking them among the largest known floods in Iceland and on Earth. Yet, all our evidence for the Kjölur jökulhlaups comes from only one publication from a quarter-century ago.
This project employs a combination of field, modelling, and laboratory methods to better constrain flood timing and dynamics at this underexplored site. This talk synthesizes geomorphologic field mapping, HEC-RAS hydraulic simulations and paleohydraulic calculations, and cosmogenic nuclide exposure dates to reconstruct Kjölur jökulhlaup routing, hydrology, and chronology. It situates these events within the context of Pleistocene-Holocene Icelandic Ice Sheet retreat and paleoenvironmental change, presenting a series of scenarios of ice margin position, glacial lake extent, and jökulhlaup drainage. Finally, it assesses the Kjölur jökulhlaups as an analogue to contemporary glacial outburst floods in other Arctic and alpine regions in terms of flood frequency, dynamics, and landscape impact.
How to cite: Wells, G., Luzzadder-Beach, S., Beach, T., Saemundsson, T., and Dugmore, A.: Geomorphology, hydrology, and chronology of Early Holocene jökulhlaups along the Hvítá River and Gullfoss waterfall, Iceland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15752, https://doi.org/10.5194/egusphere-egu21-15752, 2021.
Glacial outburst floods (jökulhlaups) have occurred across Earth throughout the Quaternary, often leaving a geomorphologic, sedimentological, and climatic legacy that extends far beyond the source region and can persist for millennia. Furthermore, they pose an increasing geohazard in glaciated landscapes worldwide due to climate-driven ice retreat. Iceland experiences more frequent jökulhlaups than nearly anywhere on Earth, though most research focuses on floods triggered by subglacial volcanic and geothermal activity. However, abundant evidence also exists for non-volcanogenic floods from proglacial lakes, which may serve as a better analogue for most global jökulhlaups.
As the Icelandic Ice Sheet retreated across Iceland in the Late Pleistocene-Early Holocene, meltwater lakes formed at ice margins and periodically drained in jökulhlaups. Some of the most catastrophic floods drained from ice-dammed Glacial Lake Kjölur, surging across southwestern Iceland from the interior highlands to the Atlantic Ocean. These floods left extensive geomorphologic evidence along the modern-day course of the Hvítá River, including canyon systems, scoured bedrock, boulder deposits, and Gullfoss—Iceland’s most famous waterfall. The largest events reached an estimated peak discharge on the order of 105 m3 s-1, ranking them among the largest known floods in Iceland and on Earth. Yet, all our evidence for the Kjölur jökulhlaups comes from only one publication from a quarter-century ago.
This project employs a combination of field, modelling, and laboratory methods to better constrain flood timing and dynamics at this underexplored site. This talk synthesizes geomorphologic field mapping, HEC-RAS hydraulic simulations and paleohydraulic calculations, and cosmogenic nuclide exposure dates to reconstruct Kjölur jökulhlaup routing, hydrology, and chronology. It situates these events within the context of Pleistocene-Holocene Icelandic Ice Sheet retreat and paleoenvironmental change, presenting a series of scenarios of ice margin position, glacial lake extent, and jökulhlaup drainage. Finally, it assesses the Kjölur jökulhlaups as an analogue to contemporary glacial outburst floods in other Arctic and alpine regions in terms of flood frequency, dynamics, and landscape impact.
How to cite: Wells, G., Luzzadder-Beach, S., Beach, T., Saemundsson, T., and Dugmore, A.: Geomorphology, hydrology, and chronology of Early Holocene jökulhlaups along the Hvítá River and Gullfoss waterfall, Iceland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15752, https://doi.org/10.5194/egusphere-egu21-15752, 2021.
EGU21-12172 | vPICO presentations | GM7.6
Palaeoclimatic and morphodynamic implications of Holocene boulder-dominated periglacial and paraglacial landforms in Rondane, South NorwayPhilipp Marr, Stefan Winkler, Svein Olaf Dahl, and Jörg Löffler
Periglacial, paraglacial and related boulder-dominated landforms constitute a valuable, but often unexplored source of palaeoclimatic and morphodynamic information. The timing of landform formation and stabilization can be linked to past cold climatic conditions which offers the possibility to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, paraglacial alluvial fan, rock-slope failure) in Rondane, eastern South Norway for the first time. On the basis of an old and young control point a local calibration curve was established from which surface exposure ages of each landform were calculated. The investigation of formation, stabilization and age of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its connectivity to landform evolution. The obtained SHD age estimates range from 11.15 ± 1.22 to 3.99 ± 1.52 ka which shows their general inactive and relict character. Most surface exposure ages of the sorted stripes cluster between 9.62 ± 1.36 and 9.01 ± 1.21 ka and appear to have stabilized towards the end of the ‘Erdalen Event’ or in the following warm period prior to ‘Finse Event’. The blockfield age with 8.40 ± 1.16 ka indicates landform stabilization during ‘Finse Event’, around the onset of the Holocene Thermal Maximum (~8.0–5.0 ka). The paraglacial alluvial fan with its four subsites shows age ranges from 8.51 ± 1.63 to 3.99 ± 1.52 ka. The old exposure age points to fan aggradation follow regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Surface exposure age of the rock-slope failure with 7.39 ± 0.74 ka falls into a transitional climate period towards the Holocene Thermal Maximum (~8.0–5.0 ka). This indicates that climate-driven factors such as decreasing permafrost depth and/or increasing hydrological pressure negatively influence slope stability. Our obtained first surface exposure ages from boulder-dominated landforms in Rondane give important insights to better understand the palaeoclimatic variability in the Holocene.
How to cite: Marr, P., Winkler, S., Dahl, S. O., and Löffler, J.: Palaeoclimatic and morphodynamic implications of Holocene boulder-dominated periglacial and paraglacial landforms in Rondane, South Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12172, https://doi.org/10.5194/egusphere-egu21-12172, 2021.
Periglacial, paraglacial and related boulder-dominated landforms constitute a valuable, but often unexplored source of palaeoclimatic and morphodynamic information. The timing of landform formation and stabilization can be linked to past cold climatic conditions which offers the possibility to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, paraglacial alluvial fan, rock-slope failure) in Rondane, eastern South Norway for the first time. On the basis of an old and young control point a local calibration curve was established from which surface exposure ages of each landform were calculated. The investigation of formation, stabilization and age of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its connectivity to landform evolution. The obtained SHD age estimates range from 11.15 ± 1.22 to 3.99 ± 1.52 ka which shows their general inactive and relict character. Most surface exposure ages of the sorted stripes cluster between 9.62 ± 1.36 and 9.01 ± 1.21 ka and appear to have stabilized towards the end of the ‘Erdalen Event’ or in the following warm period prior to ‘Finse Event’. The blockfield age with 8.40 ± 1.16 ka indicates landform stabilization during ‘Finse Event’, around the onset of the Holocene Thermal Maximum (~8.0–5.0 ka). The paraglacial alluvial fan with its four subsites shows age ranges from 8.51 ± 1.63 to 3.99 ± 1.52 ka. The old exposure age points to fan aggradation follow regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Surface exposure age of the rock-slope failure with 7.39 ± 0.74 ka falls into a transitional climate period towards the Holocene Thermal Maximum (~8.0–5.0 ka). This indicates that climate-driven factors such as decreasing permafrost depth and/or increasing hydrological pressure negatively influence slope stability. Our obtained first surface exposure ages from boulder-dominated landforms in Rondane give important insights to better understand the palaeoclimatic variability in the Holocene.
How to cite: Marr, P., Winkler, S., Dahl, S. O., and Löffler, J.: Palaeoclimatic and morphodynamic implications of Holocene boulder-dominated periglacial and paraglacial landforms in Rondane, South Norway, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12172, https://doi.org/10.5194/egusphere-egu21-12172, 2021.
EGU21-4757 | vPICO presentations | GM7.6
The impact of internal thermal regime of glaciers on climate caused advance and retreatErik Schytt Mannerfelt and Per Holmlund
Most glaciers in Sweden have polythermal temperature regimes, where a temperate core of ice is overlain by a cold surface layer. The cold surface layer prolongs the response time of a glacier, and therefore increases the time it takes for a glacier to start advancing during a cooling climate trend. In the late 1980s and 1990s, some glaciers in Sweden advanced due to prolonged periods of positive mass balance, for example Storglaciären. However, far from all glaciers advanced during this period, coincidentally relating to their cold surface layer thickness. This raises the question: what factors drive how and when a polythermal glacier advances, and what climatic signals can be read from traces of past advances and extents? Here, four polythermal glaciers are described in detail since the early 1900s, when they were close to, or at, their largest Holocene extents. These glaciers lie in relatively similar settings, and thus share many resemblances, but also show many differences. How these glaciers have changed since the early 1900s, how they look today, and what landforms they have left behind, provides an opportunity to explore factors behind their responses. The four studied glaciers are: Mikkaglaciären, Storglaciären, Rabots glaciär, and Mårmaglaciären. The dynamics of glaciers retreating are much better understood than glaciers advancing, as the overwhelming majority of existing data have been collected since the latter 1900s half, during a period of overall negative mass balance. The aim of the study is to describe the current properties of the studied glaciers. Using this knowledge and the landform assemblages in their glacier forefields, we suggest explanations to how they might have responded to climate change in the past and possible causes for differences in their response.
How to cite: Schytt Mannerfelt, E. and Holmlund, P.: The impact of internal thermal regime of glaciers on climate caused advance and retreat, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4757, https://doi.org/10.5194/egusphere-egu21-4757, 2021.
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Most glaciers in Sweden have polythermal temperature regimes, where a temperate core of ice is overlain by a cold surface layer. The cold surface layer prolongs the response time of a glacier, and therefore increases the time it takes for a glacier to start advancing during a cooling climate trend. In the late 1980s and 1990s, some glaciers in Sweden advanced due to prolonged periods of positive mass balance, for example Storglaciären. However, far from all glaciers advanced during this period, coincidentally relating to their cold surface layer thickness. This raises the question: what factors drive how and when a polythermal glacier advances, and what climatic signals can be read from traces of past advances and extents? Here, four polythermal glaciers are described in detail since the early 1900s, when they were close to, or at, their largest Holocene extents. These glaciers lie in relatively similar settings, and thus share many resemblances, but also show many differences. How these glaciers have changed since the early 1900s, how they look today, and what landforms they have left behind, provides an opportunity to explore factors behind their responses. The four studied glaciers are: Mikkaglaciären, Storglaciären, Rabots glaciär, and Mårmaglaciären. The dynamics of glaciers retreating are much better understood than glaciers advancing, as the overwhelming majority of existing data have been collected since the latter 1900s half, during a period of overall negative mass balance. The aim of the study is to describe the current properties of the studied glaciers. Using this knowledge and the landform assemblages in their glacier forefields, we suggest explanations to how they might have responded to climate change in the past and possible causes for differences in their response.
How to cite: Schytt Mannerfelt, E. and Holmlund, P.: The impact of internal thermal regime of glaciers on climate caused advance and retreat, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4757, https://doi.org/10.5194/egusphere-egu21-4757, 2021.
EGU21-14010 | vPICO presentations | GM7.6
Iceberg dynamics in a proglacial lake in Austria quantified by time-lapse photographyFelix Bernsteiner and Andreas Kellerer-Pirklbauer
The recession of glaciers reveals a dynamic landscape exposed to high rates of hydrological and geomorphological modifications. Such deglaciation processes caused the formation of a 0.3 km² large proglacial lake (named Pasterzensee) near the terminus of Pasterze Glacier, Austria, during the last two decades. The evolution of the proglacial lake was accompanied by several buoyant calving events. The process of buoyant calving formed numerous floating dead ice bodies referred to as icebergs which covered a maximum of 7.3 % of the entire proglacial lake basin in November 2018.
Despite the existence of icebergs at some proglacial lakes in the European Alps, little is known about the evolution and life span of icebergs in proglacial lakes in the European Alps. The aim of this study was to reduce this research gap by (a) quantifying the evolution of such alpine icebergs during two different time scales and by (b) analysing the relationship between iceberg evolution and motion at the lake with meteorological conditions. At a long-term scale, one single iceberg was monitored during the period 01.09.2017-30.09.2019. At a short-term scale, all icebergs were studied during one single day (16.06.2019).
The most important data source for this study were time-lapse optical imagery from an automatic camera overlooking the entire proglacial lake (GROHAG). The used camera is a Roundshot Livecam Generation 2 (Seitz, Switzerland). Photographic imagery is captured every five minutes (during daylight) from a location 310 m above lake level and 450 m northeast of the lake margin. For the long-term analysis, a total number of 386 pictures of the lake were processed. For the short-term analysis, 97 pictures were analysed to reveal the dynamics of 84 icebergs during one single day. The oblique time-lapse images were transformed into orthorectified photos using a rectification algorithm which considers the camera properties and the lake surface geometry. Iceberg size and centroid coordinates were mapped in all generated orthophotos. In addition, meteorological data (ZAMG Vienna) was provided by a nearby automatic weather station, located at the glacier tongue of Pasterze Glacier some 1.1 km northwest of the lake margin.
Results indicate that the monitoring of one iceberg over a period of 25 months revealed highest melting rates from June to August, low melting rates from September to November and no measurable melting when the lake surface is frozen. Horizontal iceberg displacement is rising with decreasing iceberg size throughout the study period. The analysed iceberg formed during the detachment of a debris covered ice peninsula with an initial size of 7250 m² and was last identifiable at a size of 240 m². Monitoring lake-wide iceberg movement for one day shows that wind is the main influence on horizontal iceberg displacement. The existence of a strong valley wind, caused by a diurnal warming cycle, is observed. This wind system decouples the iceberg movement from the constant katabatic glacier wind, recorded by the weather station. Frequent jumps in movement rates, which are not explained by wind data, suggest that iceberg grounding is a common process influencing subaquatic lake morphology.
How to cite: Bernsteiner, F. and Kellerer-Pirklbauer, A.: Iceberg dynamics in a proglacial lake in Austria quantified by time-lapse photography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14010, https://doi.org/10.5194/egusphere-egu21-14010, 2021.
The recession of glaciers reveals a dynamic landscape exposed to high rates of hydrological and geomorphological modifications. Such deglaciation processes caused the formation of a 0.3 km² large proglacial lake (named Pasterzensee) near the terminus of Pasterze Glacier, Austria, during the last two decades. The evolution of the proglacial lake was accompanied by several buoyant calving events. The process of buoyant calving formed numerous floating dead ice bodies referred to as icebergs which covered a maximum of 7.3 % of the entire proglacial lake basin in November 2018.
Despite the existence of icebergs at some proglacial lakes in the European Alps, little is known about the evolution and life span of icebergs in proglacial lakes in the European Alps. The aim of this study was to reduce this research gap by (a) quantifying the evolution of such alpine icebergs during two different time scales and by (b) analysing the relationship between iceberg evolution and motion at the lake with meteorological conditions. At a long-term scale, one single iceberg was monitored during the period 01.09.2017-30.09.2019. At a short-term scale, all icebergs were studied during one single day (16.06.2019).
The most important data source for this study were time-lapse optical imagery from an automatic camera overlooking the entire proglacial lake (GROHAG). The used camera is a Roundshot Livecam Generation 2 (Seitz, Switzerland). Photographic imagery is captured every five minutes (during daylight) from a location 310 m above lake level and 450 m northeast of the lake margin. For the long-term analysis, a total number of 386 pictures of the lake were processed. For the short-term analysis, 97 pictures were analysed to reveal the dynamics of 84 icebergs during one single day. The oblique time-lapse images were transformed into orthorectified photos using a rectification algorithm which considers the camera properties and the lake surface geometry. Iceberg size and centroid coordinates were mapped in all generated orthophotos. In addition, meteorological data (ZAMG Vienna) was provided by a nearby automatic weather station, located at the glacier tongue of Pasterze Glacier some 1.1 km northwest of the lake margin.
Results indicate that the monitoring of one iceberg over a period of 25 months revealed highest melting rates from June to August, low melting rates from September to November and no measurable melting when the lake surface is frozen. Horizontal iceberg displacement is rising with decreasing iceberg size throughout the study period. The analysed iceberg formed during the detachment of a debris covered ice peninsula with an initial size of 7250 m² and was last identifiable at a size of 240 m². Monitoring lake-wide iceberg movement for one day shows that wind is the main influence on horizontal iceberg displacement. The existence of a strong valley wind, caused by a diurnal warming cycle, is observed. This wind system decouples the iceberg movement from the constant katabatic glacier wind, recorded by the weather station. Frequent jumps in movement rates, which are not explained by wind data, suggest that iceberg grounding is a common process influencing subaquatic lake morphology.
How to cite: Bernsteiner, F. and Kellerer-Pirklbauer, A.: Iceberg dynamics in a proglacial lake in Austria quantified by time-lapse photography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14010, https://doi.org/10.5194/egusphere-egu21-14010, 2021.
EGU21-2196 | vPICO presentations | GM7.6 | Highlight
Permafrost vulnerability to contemporary climate changes in Eastern Chukotka coastal plains (NE Russia)Alexey Maslakov, Nina Komova, Evgeny Egorov, Polina Mikhaylyukova, Mikhail Grishchenko, and Larisa Zotova
Recent permafrost degradation is detected in many cold regions of the world. This process is due to surface lowering caused by ice-rich sediments thaw and massive ice beds melt. Eastern Chukotka coastal plains polygon is one of the key sites for studying climate change's impact on permafrost conditions and human activity. This region is the habitat of indigenous people, concentrated in the coastal villages. The study site is approximately 400 km2 in area and characterized by a variety of landscape, geomorphological, and permafrost conditions. Using remote sensing data, field observations, and shallow drilling results, we ranked and delineated the areas on their susceptibility to thermokarst, thermal erosion, and solifluction activation due to the further air temperature increasing and potential human disturbances. Spatial analysis on current thaw settlement rates combined with drilling data allowed us to map the areas with a high concentration of surficial massive ice beds. These studies provide a better understanding of permafrost conditions in Eastern Chukotka and its response to human impact and climate change.
How to cite: Maslakov, A., Komova, N., Egorov, E., Mikhaylyukova, P., Grishchenko, M., and Zotova, L.: Permafrost vulnerability to contemporary climate changes in Eastern Chukotka coastal plains (NE Russia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2196, https://doi.org/10.5194/egusphere-egu21-2196, 2021.
Recent permafrost degradation is detected in many cold regions of the world. This process is due to surface lowering caused by ice-rich sediments thaw and massive ice beds melt. Eastern Chukotka coastal plains polygon is one of the key sites for studying climate change's impact on permafrost conditions and human activity. This region is the habitat of indigenous people, concentrated in the coastal villages. The study site is approximately 400 km2 in area and characterized by a variety of landscape, geomorphological, and permafrost conditions. Using remote sensing data, field observations, and shallow drilling results, we ranked and delineated the areas on their susceptibility to thermokarst, thermal erosion, and solifluction activation due to the further air temperature increasing and potential human disturbances. Spatial analysis on current thaw settlement rates combined with drilling data allowed us to map the areas with a high concentration of surficial massive ice beds. These studies provide a better understanding of permafrost conditions in Eastern Chukotka and its response to human impact and climate change.
How to cite: Maslakov, A., Komova, N., Egorov, E., Mikhaylyukova, P., Grishchenko, M., and Zotova, L.: Permafrost vulnerability to contemporary climate changes in Eastern Chukotka coastal plains (NE Russia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2196, https://doi.org/10.5194/egusphere-egu21-2196, 2021.
EGU21-7878 | vPICO presentations | GM7.6
New findings regarding the ground air circulation by chimney effect in low-altitude permafrost susceptible porous screes (Detunata Goală, Romanian Carpathians)Răzvan Popescu, Alfred Vespremeanu-Stroe, Mirela Vasile, Ilie Andrian, Sabina Calisevici, and Bogdan Niculiță
Seasonally differentiated ground air circulation in low altitude porous talus slopes from temperate regions known as chimney circulation creates the conditions for permafrost development in their lower parts well below the regional permafrost altitudinal limit. So far it was shown that the cold air adsorption and warm air exfiltration areas during winter correspond to the lower and upper areas respectively of talus slopes and that they are quite stable and regular in extent and shape. New aerial survey in early winter at Detunata Goală scree with a complex talus slope-rock glacier morphology performed immediately in the days following light snow falls allowed the precise detection of warm air areas positions, shape and temporal changes within hours and days. Several triangular-shaped stripes were found to occur continuously from lower to upper parts of talus slopes and morphometric analysis on a high resolution UAV-derived DEM revealed that they correspond to 1the central longitudinal axis of debris cones composing the talus slopes. Thermal monitoring of air between the blocks was also performed at the location of these stripes where a thermal gradient was found to occur: the atmospheric/ground air temperature contrast increases upwards and towards the axis of talus cones reaching a maximum of >10 °C (+5.3 °C in the ground versus -5 °C outside). In the rock glacier lobe area, the warm air evacuation is different and presents a linear configuration. This work discusses the relation between the morphometry of the deposit and warm air evacuation areas and their short term thermal regime. Also, it discusses new geophysical investigations results (electrical resistivity tomography and seismic refraction tomography) performed at the end of the warm season of 2020 in the coldest area of the scree.
How to cite: Popescu, R., Vespremeanu-Stroe, A., Vasile, M., Andrian, I., Calisevici, S., and Niculiță, B.: New findings regarding the ground air circulation by chimney effect in low-altitude permafrost susceptible porous screes (Detunata Goală, Romanian Carpathians), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7878, https://doi.org/10.5194/egusphere-egu21-7878, 2021.
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Seasonally differentiated ground air circulation in low altitude porous talus slopes from temperate regions known as chimney circulation creates the conditions for permafrost development in their lower parts well below the regional permafrost altitudinal limit. So far it was shown that the cold air adsorption and warm air exfiltration areas during winter correspond to the lower and upper areas respectively of talus slopes and that they are quite stable and regular in extent and shape. New aerial survey in early winter at Detunata Goală scree with a complex talus slope-rock glacier morphology performed immediately in the days following light snow falls allowed the precise detection of warm air areas positions, shape and temporal changes within hours and days. Several triangular-shaped stripes were found to occur continuously from lower to upper parts of talus slopes and morphometric analysis on a high resolution UAV-derived DEM revealed that they correspond to 1the central longitudinal axis of debris cones composing the talus slopes. Thermal monitoring of air between the blocks was also performed at the location of these stripes where a thermal gradient was found to occur: the atmospheric/ground air temperature contrast increases upwards and towards the axis of talus cones reaching a maximum of >10 °C (+5.3 °C in the ground versus -5 °C outside). In the rock glacier lobe area, the warm air evacuation is different and presents a linear configuration. This work discusses the relation between the morphometry of the deposit and warm air evacuation areas and their short term thermal regime. Also, it discusses new geophysical investigations results (electrical resistivity tomography and seismic refraction tomography) performed at the end of the warm season of 2020 in the coldest area of the scree.
How to cite: Popescu, R., Vespremeanu-Stroe, A., Vasile, M., Andrian, I., Calisevici, S., and Niculiță, B.: New findings regarding the ground air circulation by chimney effect in low-altitude permafrost susceptible porous screes (Detunata Goală, Romanian Carpathians), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7878, https://doi.org/10.5194/egusphere-egu21-7878, 2021.
EGU21-12588 | vPICO presentations | GM7.6
Ground thermal contrasts and variability at an alpine pyramidal peak in central Austria (Innerer Knorrkogel, Venediger Mountains)Andreas Kellerer-Pirklbauer and Gerhard Karl Lieb
Ground temperatures in alpine environments are severely influenced by slope orientation (aspect), slope inclination, local topoclimatic conditions, and thermal properties of the rock material. Small differences in one of these factors may substantially impact the ground thermal regime, weathering by freeze-thaw action or the occurrence of permafrost. To improve the understanding of differences, variations, and ranges of ground temperatures at single mountain summits, we studied the ground thermal conditions at a triangle-shaped (plan view), moderately steep pyramidal peak over a two-year period (2018-2020).
We installed 18 monitoring sites with 23 sensors near the summit of Innerer Knorrkogel (2882m asl), in summer 2018 with one- and multi-channel datalogger (Geoprecision). All three mountain ridges (east-, northwest-, and southwest-facing) and flanks (northeast-, west-, and south-facing) were instrumented with one-channel dataloggers at two different elevations (2840 and 2860m asl) at each ridge/flank to monitor ground surface temperatures. Three bedrock temperature monitoring sites with shallow boreholes (40cm) equipped with three sensors per site at each of the three mountain flanks (2870m asl) were established. Additionally, two ground surface temperature monitoring sites were installed at the summit.
Results show remarkable differences in mean annual ground temperatures (MAGT) between the 23 different sensors and the two years despite the small spatial extent (0.023 km²) and elevation differences (46m). Intersite variability at the entire mountain pyramid was 3.74°C in 2018/19 (mean MAGT: -0.40°C; minimum: -1.78°C; maximum: 1.96°C;) and 3.27°C in 2019/20 (mean MAGT: 0.08°C; minimum: -1.54°C; maximum: 1,73°C;). Minimum was in both years at the northeast-facing flank, maximum at the south-facing flank. In all but three sites, the second monitoring year was warmer than the first one (mean +0.48°C) related to atmospheric differences and site-specific snow conditions. The comparison of the MAGT-values of the two years (MAGT-2018/19 minus MAGT-2019/20) revealed large thermal inhomogeneities in the mountain summit ranging from +0.65° (2018/19 warmer than 2019/20) to -1.76°C (2018/19 colder than 2019/20) at identical sensors. Temperature ranges at the three different aspects but at equal elevations were 1.7-2.2°C at ridges and 1.8-3.7°C at flanks for single years. The higher temperature range for flank-sites is related to seasonal snow cover effects combined with higher radiation at sun-exposed sites. Although the ground temperature was substantially higher in the second year, the snow cover difference between the two years was variable. Some sites experienced longer snow cover periods in the second year 2019/20 (up to +85 days) whereas at other sites the opposite was observed (up to -85 days). Other frost weathering-related indicators (diurnal freeze-thaw cycles, frost-cracking window) show also large intersite and interannual differences.
Our study shows that the thermal regime at a triangle-shaped moderately steep pyramidal peak is very heterogeneous between different aspects and landforms (ridge/flank/summit) and between two monitoring years confirming earlier monitoring and modelling results. Due to high intersite and interannual variabilities, temperature-related processes such as frost-weathering can vary largely between neighbouring sites. Our study highlights the need for systematic and long-term ground temperature monitoring in alpine terrain to improve the understanding of small- to medium-scale temperature variabilities.
How to cite: Kellerer-Pirklbauer, A. and Lieb, G. K.: Ground thermal contrasts and variability at an alpine pyramidal peak in central Austria (Innerer Knorrkogel, Venediger Mountains), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12588, https://doi.org/10.5194/egusphere-egu21-12588, 2021.
Ground temperatures in alpine environments are severely influenced by slope orientation (aspect), slope inclination, local topoclimatic conditions, and thermal properties of the rock material. Small differences in one of these factors may substantially impact the ground thermal regime, weathering by freeze-thaw action or the occurrence of permafrost. To improve the understanding of differences, variations, and ranges of ground temperatures at single mountain summits, we studied the ground thermal conditions at a triangle-shaped (plan view), moderately steep pyramidal peak over a two-year period (2018-2020).
We installed 18 monitoring sites with 23 sensors near the summit of Innerer Knorrkogel (2882m asl), in summer 2018 with one- and multi-channel datalogger (Geoprecision). All three mountain ridges (east-, northwest-, and southwest-facing) and flanks (northeast-, west-, and south-facing) were instrumented with one-channel dataloggers at two different elevations (2840 and 2860m asl) at each ridge/flank to monitor ground surface temperatures. Three bedrock temperature monitoring sites with shallow boreholes (40cm) equipped with three sensors per site at each of the three mountain flanks (2870m asl) were established. Additionally, two ground surface temperature monitoring sites were installed at the summit.
Results show remarkable differences in mean annual ground temperatures (MAGT) between the 23 different sensors and the two years despite the small spatial extent (0.023 km²) and elevation differences (46m). Intersite variability at the entire mountain pyramid was 3.74°C in 2018/19 (mean MAGT: -0.40°C; minimum: -1.78°C; maximum: 1.96°C;) and 3.27°C in 2019/20 (mean MAGT: 0.08°C; minimum: -1.54°C; maximum: 1,73°C;). Minimum was in both years at the northeast-facing flank, maximum at the south-facing flank. In all but three sites, the second monitoring year was warmer than the first one (mean +0.48°C) related to atmospheric differences and site-specific snow conditions. The comparison of the MAGT-values of the two years (MAGT-2018/19 minus MAGT-2019/20) revealed large thermal inhomogeneities in the mountain summit ranging from +0.65° (2018/19 warmer than 2019/20) to -1.76°C (2018/19 colder than 2019/20) at identical sensors. Temperature ranges at the three different aspects but at equal elevations were 1.7-2.2°C at ridges and 1.8-3.7°C at flanks for single years. The higher temperature range for flank-sites is related to seasonal snow cover effects combined with higher radiation at sun-exposed sites. Although the ground temperature was substantially higher in the second year, the snow cover difference between the two years was variable. Some sites experienced longer snow cover periods in the second year 2019/20 (up to +85 days) whereas at other sites the opposite was observed (up to -85 days). Other frost weathering-related indicators (diurnal freeze-thaw cycles, frost-cracking window) show also large intersite and interannual differences.
Our study shows that the thermal regime at a triangle-shaped moderately steep pyramidal peak is very heterogeneous between different aspects and landforms (ridge/flank/summit) and between two monitoring years confirming earlier monitoring and modelling results. Due to high intersite and interannual variabilities, temperature-related processes such as frost-weathering can vary largely between neighbouring sites. Our study highlights the need for systematic and long-term ground temperature monitoring in alpine terrain to improve the understanding of small- to medium-scale temperature variabilities.
How to cite: Kellerer-Pirklbauer, A. and Lieb, G. K.: Ground thermal contrasts and variability at an alpine pyramidal peak in central Austria (Innerer Knorrkogel, Venediger Mountains), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12588, https://doi.org/10.5194/egusphere-egu21-12588, 2021.
EGU21-9369 * | vPICO presentations | GM7.6 | Highlight
Alpine headwall erosion: Insights from cosmogenic nuclide concentrations in supraglacial debris coverKatharina Wetterauer, Dirk Scherler, Leif S. Anderson, and Hella Wittmann
Debris-covered glaciers are fed from steep bedrock hillslopes that tower above the ice. These headwalls are eroded by rockfalls and rock avalanches, mobilizing fractured bedrock, which is subsequently deposited on the ice surface along the sides of valley glaciers and transported downglacier on and in the ice. Where glaciers join, marginal debris merges to form medial moraines. Due to the conveyor-belt-nature of glacier ablation zones, debris tends to be older downglacier and, for typical Alpine glaciers, single deposits may persist on the glacier surface for hundreds to a few thousand years.
Recent observations in high-alpine glacial environments suggest that rock walls are increasingly destabilized due to climate warming. An increase in headwall erosion and debris deposition onto glacier surfaces will modify glacial mass balances, as surface debris cover alters the rate at which underlying ice melts. Consequently, we expect that the response of debris-covered glaciers to climate change is likely also related to the response of headwalls to climate change.
In this context, we quantify headwall retreat rates by measuring the concentration of in situ-produced cosmogenic 10Be in debris samples collected from a partly debris-covered Swiss valley glacier. By systematic downglacier-sampling of two parallel medial moraines, we aim to assess changes in headwall erosion through time for small and delineated source areas. Our results indicate that indeed, nuclide concentrations along the medial moraines vary with time: downglacier and further back in time deposits have higher nuclide concentrations, whereas upglacier and more recently deposits have lower concentrations. Currently, we explore possible processes which could account for 10Be concentration changes through time, other than changes in erosion rates. These include the sensitivity of 10Be concentrations to supraglacial transport time and to temporal and spatial changes in nuclide production rates on the deglaciating headwalls. First analyses reveal, however, that neither the additional accumulation of 10Be during transport nor changes in source area production rates associated with the uncovering of formerly ice covered headwall parts alone can account for the observed trend.
How to cite: Wetterauer, K., Scherler, D., Anderson, L. S., and Wittmann, H.: Alpine headwall erosion: Insights from cosmogenic nuclide concentrations in supraglacial debris cover , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9369, https://doi.org/10.5194/egusphere-egu21-9369, 2021.
Debris-covered glaciers are fed from steep bedrock hillslopes that tower above the ice. These headwalls are eroded by rockfalls and rock avalanches, mobilizing fractured bedrock, which is subsequently deposited on the ice surface along the sides of valley glaciers and transported downglacier on and in the ice. Where glaciers join, marginal debris merges to form medial moraines. Due to the conveyor-belt-nature of glacier ablation zones, debris tends to be older downglacier and, for typical Alpine glaciers, single deposits may persist on the glacier surface for hundreds to a few thousand years.
Recent observations in high-alpine glacial environments suggest that rock walls are increasingly destabilized due to climate warming. An increase in headwall erosion and debris deposition onto glacier surfaces will modify glacial mass balances, as surface debris cover alters the rate at which underlying ice melts. Consequently, we expect that the response of debris-covered glaciers to climate change is likely also related to the response of headwalls to climate change.
In this context, we quantify headwall retreat rates by measuring the concentration of in situ-produced cosmogenic 10Be in debris samples collected from a partly debris-covered Swiss valley glacier. By systematic downglacier-sampling of two parallel medial moraines, we aim to assess changes in headwall erosion through time for small and delineated source areas. Our results indicate that indeed, nuclide concentrations along the medial moraines vary with time: downglacier and further back in time deposits have higher nuclide concentrations, whereas upglacier and more recently deposits have lower concentrations. Currently, we explore possible processes which could account for 10Be concentration changes through time, other than changes in erosion rates. These include the sensitivity of 10Be concentrations to supraglacial transport time and to temporal and spatial changes in nuclide production rates on the deglaciating headwalls. First analyses reveal, however, that neither the additional accumulation of 10Be during transport nor changes in source area production rates associated with the uncovering of formerly ice covered headwall parts alone can account for the observed trend.
How to cite: Wetterauer, K., Scherler, D., Anderson, L. S., and Wittmann, H.: Alpine headwall erosion: Insights from cosmogenic nuclide concentrations in supraglacial debris cover , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9369, https://doi.org/10.5194/egusphere-egu21-9369, 2021.
EGU21-15023 | vPICO presentations | GM7.6 | Highlight
Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc massif using in situ cosmogenic 3He-10Be-14CDonovan P. Dennis, Dirk Scherler, Samuel Niedermann, Kristina Hippe, Hella Wittmann, Ludovic Ravanel, Marissa Tremblay, Benny Guralnik, and Maarten Lupker
The erosion of cold bedrock hillslopes in alpine environments depends not only on rates of frost weathering and accumulated rock damage, but additionally on the removal of the weathered material from the bedrock surface. In the Mont Blanc massif, steep bedrock faces with exposure ages sometimes much older than 50,000 years sit in close proximity to actively-eroding rockwalls, suggesting a more complex relationship between temperature and erosion rates than encompassed by the proposed “frost-cracking window.” Stochastic events like rockfalls and rock avalanches, despite their rarity, contribute a non-trivial proportion of the total sediment budget in alpine permafrost regions, adding to the contribution from background “steady-state” erosion. Employing a methodology based on the combination of in-situ cosmogenic nuclides 3He -10Be-14C, we test the temperature-dependence of high-alpine erosion while taking into account erosional stochasticity.
From cosmogenic 10Be concentrations of amalgamated samples collected on the Aiguille du Midi (3842 m a.s.l.) in the Mont Blanc massif, we find an order of magnitude difference in erosion rate across the peak’s surface. Our preliminary measured erosion rates, ranging between appx. 0.03 mm yr-1 and 1.0 mm yr-1, correlate neither with modern temperature measurements from borehole thermistors, nor with our current estimates of bedrock cosmogenic 3He-derived paleotemperatures. The corresponding cosmogenic 14C/10Be ratios (between 1.70 and 4.0) for these erosion rates indicate that our measurements are not biased by recent stochastic rockfall events. Our current results therefore suggest that on geomorphic timescales, bedrock hillslope erosion rates are not set solely by rates of frost-cracking, but rather by the combined effects of frost-cracking and permafrost thaw-induced rockfalls. These insights are relevant both for short-term monitoring of alpine permafrost and associated geohazards under a warming climate, as well as studies of proposed “buzzsaws” operating on glacial-interglacial timescales.
How to cite: Dennis, D. P., Scherler, D., Niedermann, S., Hippe, K., Wittmann, H., Ravanel, L., Tremblay, M., Guralnik, B., and Lupker, M.: Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc massif using in situ cosmogenic 3He-10Be-14C, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15023, https://doi.org/10.5194/egusphere-egu21-15023, 2021.
The erosion of cold bedrock hillslopes in alpine environments depends not only on rates of frost weathering and accumulated rock damage, but additionally on the removal of the weathered material from the bedrock surface. In the Mont Blanc massif, steep bedrock faces with exposure ages sometimes much older than 50,000 years sit in close proximity to actively-eroding rockwalls, suggesting a more complex relationship between temperature and erosion rates than encompassed by the proposed “frost-cracking window.” Stochastic events like rockfalls and rock avalanches, despite their rarity, contribute a non-trivial proportion of the total sediment budget in alpine permafrost regions, adding to the contribution from background “steady-state” erosion. Employing a methodology based on the combination of in-situ cosmogenic nuclides 3He -10Be-14C, we test the temperature-dependence of high-alpine erosion while taking into account erosional stochasticity.
From cosmogenic 10Be concentrations of amalgamated samples collected on the Aiguille du Midi (3842 m a.s.l.) in the Mont Blanc massif, we find an order of magnitude difference in erosion rate across the peak’s surface. Our preliminary measured erosion rates, ranging between appx. 0.03 mm yr-1 and 1.0 mm yr-1, correlate neither with modern temperature measurements from borehole thermistors, nor with our current estimates of bedrock cosmogenic 3He-derived paleotemperatures. The corresponding cosmogenic 14C/10Be ratios (between 1.70 and 4.0) for these erosion rates indicate that our measurements are not biased by recent stochastic rockfall events. Our current results therefore suggest that on geomorphic timescales, bedrock hillslope erosion rates are not set solely by rates of frost-cracking, but rather by the combined effects of frost-cracking and permafrost thaw-induced rockfalls. These insights are relevant both for short-term monitoring of alpine permafrost and associated geohazards under a warming climate, as well as studies of proposed “buzzsaws” operating on glacial-interglacial timescales.
How to cite: Dennis, D. P., Scherler, D., Niedermann, S., Hippe, K., Wittmann, H., Ravanel, L., Tremblay, M., Guralnik, B., and Lupker, M.: Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc massif using in situ cosmogenic 3He-10Be-14C, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15023, https://doi.org/10.5194/egusphere-egu21-15023, 2021.
EGU21-9653 | vPICO presentations | GM7.6
Rock glacier sediment, kinematics and geomorphometry: a study case from the Eastern Italian AlpsFederica Minotti, Christian Kofler, Bernhard Gems, Volkmar Mair, and Francesco Comiti
Rock glaciers are important geomorphological structures of high mountain environments and fundamental indicators for permafrost. They consist of unconsolidated rock debris – generally derived from talus or till - held together by ice, moving slowly downslope due to the gravitation in combination with uncountable freeze-thaw-cycles in the active layer. The downslope movement of rock glaciers leads to lobate structures with depressed areas as well as ridges where the sediments tend to accumulate, creating a typical surface morphology defined as "ridges and furrows". This study focuses on the analysis of one rock glacier system located in the Pfitsch/Vizze valley (South Tyrol), in the Eastern Italian Alps. The debris in this area comprises exclusively the granitic Central Gneiss of the Tauern window. Rock glacier sediment derives from talus, consisting essentially of more or less foliated to planar angular material, which was essentially formed by frost weathering. The size and shape of sediments present at the surface of the rock glacier system were analyzed in correlation with displacement and geomorphometry, with the hypothesis that sediments shape and size at different sites across the rock glacier might relate to its past and present dynamics. The displacement analyses were carried out to quantify rock glaciers movements during the last 20 years, and the geomorphometrical characteristics were investigated to identify specific geometrical attributes that may be linked to internal ice changes.
Clasts analysis showed how rock glacier sediments are very heterogeneous, with dimensions being mainly determined by transport distance, and sphericity and roundness by lithology. A role of sediments characteristics on displacement rate did not turn out evident. Convexities and concavities observed on the study site are apparently created respectively by the accumulation of sediments and the collapse of the structure due to the internal ice melting. Indeed, the recent, marked increase in air temperature observed in the last decades in the Alps has likely caused an accelerated ice melting in the less protected – in terms of solar radiation – rock glaciers, as is the case for our study area. Sediments here are no longer bound by ice and have become rather unstable. Therefore, the monitoring of rock glaciers is fundamental to anticipate future changes in the type and magnitude of natural hazards originating at high elevations, as thicker layers of sediments are becoming increasingly unstable.
How to cite: Minotti, F., Kofler, C., Gems, B., Mair, V., and Comiti, F.: Rock glacier sediment, kinematics and geomorphometry: a study case from the Eastern Italian Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9653, https://doi.org/10.5194/egusphere-egu21-9653, 2021.
Rock glaciers are important geomorphological structures of high mountain environments and fundamental indicators for permafrost. They consist of unconsolidated rock debris – generally derived from talus or till - held together by ice, moving slowly downslope due to the gravitation in combination with uncountable freeze-thaw-cycles in the active layer. The downslope movement of rock glaciers leads to lobate structures with depressed areas as well as ridges where the sediments tend to accumulate, creating a typical surface morphology defined as "ridges and furrows". This study focuses on the analysis of one rock glacier system located in the Pfitsch/Vizze valley (South Tyrol), in the Eastern Italian Alps. The debris in this area comprises exclusively the granitic Central Gneiss of the Tauern window. Rock glacier sediment derives from talus, consisting essentially of more or less foliated to planar angular material, which was essentially formed by frost weathering. The size and shape of sediments present at the surface of the rock glacier system were analyzed in correlation with displacement and geomorphometry, with the hypothesis that sediments shape and size at different sites across the rock glacier might relate to its past and present dynamics. The displacement analyses were carried out to quantify rock glaciers movements during the last 20 years, and the geomorphometrical characteristics were investigated to identify specific geometrical attributes that may be linked to internal ice changes.
Clasts analysis showed how rock glacier sediments are very heterogeneous, with dimensions being mainly determined by transport distance, and sphericity and roundness by lithology. A role of sediments characteristics on displacement rate did not turn out evident. Convexities and concavities observed on the study site are apparently created respectively by the accumulation of sediments and the collapse of the structure due to the internal ice melting. Indeed, the recent, marked increase in air temperature observed in the last decades in the Alps has likely caused an accelerated ice melting in the less protected – in terms of solar radiation – rock glaciers, as is the case for our study area. Sediments here are no longer bound by ice and have become rather unstable. Therefore, the monitoring of rock glaciers is fundamental to anticipate future changes in the type and magnitude of natural hazards originating at high elevations, as thicker layers of sediments are becoming increasingly unstable.
How to cite: Minotti, F., Kofler, C., Gems, B., Mair, V., and Comiti, F.: Rock glacier sediment, kinematics and geomorphometry: a study case from the Eastern Italian Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9653, https://doi.org/10.5194/egusphere-egu21-9653, 2021.
EGU21-14788 | vPICO presentations | GM7.6
Monitoring the dynamics of an alpine rock glacier with repeated UAV and GNSS dataFrancesca Bearzot, Roberto Garzonio, Biagio Di Mauro, Christian Hauck, Reynald Delaloye, Umberto Morra Di Cella, Edoardo Cremonese, Paolo Pogliotti, Giovanni Battista Crosta, Roberto Colombo, Paolo Frattini, and Micol Rossini
Time series of rock glaciers (RG) movements in the European Alps indicate an acceleration in permafrost creep in recent decades in relation to an increase in ground temperatures and water content. In this work, we analyse the geomorphological changes of an active RG located in the Western European Alps, in Valtournenche Valley (AO, Italy).
Five photogrammetric surveys were realized on the RG between 2015 to 2019, using a senseFly eBee RTK and a DJI Phantom 4 UAVs. During UAV acquisitions, 21 ground control points were placed all over the study area and their coordinates were measured in GNSS RTK mode, for georeferencing each photogrammetric model. The monitoring activity also includes GNSS campaigns, carried out annually since 2012, which provides high accurate surface displacement measurements but limited to 54 points. In addition, in July 2015 two Electrical Resistivity Tomography profiles were performed, with the Wenner-Schlumberger configuration, to identify the internal structure and potential ground ice content inside the main body of the RG.
The Structure-from-Motion technique was used to generate orthophotos and digital surface models with a resolution of 5 cm/px. Successively, we estimated the three-dimensional change of the surface displacements (surface lowering and accumulation processes) of the RG comparing pairs of point clouds, using the Multiscale Model to Model Cloud Comparison (M3C2 plug-in). A first evaluation of the horizontal surface velocity was computed identifying corresponding features manually on the orthophotos through time and a second assessment was performed based on repeated GNSS campaigns. Surface velocity obtained by orthophotos manual identifications is validated against repeated GNSS measurements. The analysis shows a good correlation at all magnitudes with a R2 equal to 0.988 and RMSE of 26 cm.
The RG shows a clear distinction in creep dynamics between a faster western part (values up to 1.8 m/y) and a slower eastern part, with values below 0.1 m/y in the most upstream part. Considering the period 2012-2020, maximum peak of surface velocity is reached in 2015, followed by a velocity decrease until 2017-2018 when the smallest movements are recorded. However, the following two years (2018-2019 and 2019-2020) are marked by a gradual increase in surface horizontal velocity. The absence of significant of any significant movement in the upstream part is related to the lack of permafrost consecutive to the development and advance of a local glacier during the Little Ice Age. The slower eastern part is almost gently inclined and corresponds to a currently degrading part of the RG, with an ice melt-induced subsidence of up to 5 cm/year. The faster area is also the steepest, where the driving stress is also the largest. The presence of the frozen ground at depth, probably its structure and thermal state, but also the topographical settings are the main factors explaining the current RG flow pattern.
How to cite: Bearzot, F., Garzonio, R., Di Mauro, B., Hauck, C., Delaloye, R., Morra Di Cella, U., Cremonese, E., Pogliotti, P., Crosta, G. B., Colombo, R., Frattini, P., and Rossini, M.: Monitoring the dynamics of an alpine rock glacier with repeated UAV and GNSS data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14788, https://doi.org/10.5194/egusphere-egu21-14788, 2021.
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Time series of rock glaciers (RG) movements in the European Alps indicate an acceleration in permafrost creep in recent decades in relation to an increase in ground temperatures and water content. In this work, we analyse the geomorphological changes of an active RG located in the Western European Alps, in Valtournenche Valley (AO, Italy).
Five photogrammetric surveys were realized on the RG between 2015 to 2019, using a senseFly eBee RTK and a DJI Phantom 4 UAVs. During UAV acquisitions, 21 ground control points were placed all over the study area and their coordinates were measured in GNSS RTK mode, for georeferencing each photogrammetric model. The monitoring activity also includes GNSS campaigns, carried out annually since 2012, which provides high accurate surface displacement measurements but limited to 54 points. In addition, in July 2015 two Electrical Resistivity Tomography profiles were performed, with the Wenner-Schlumberger configuration, to identify the internal structure and potential ground ice content inside the main body of the RG.
The Structure-from-Motion technique was used to generate orthophotos and digital surface models with a resolution of 5 cm/px. Successively, we estimated the three-dimensional change of the surface displacements (surface lowering and accumulation processes) of the RG comparing pairs of point clouds, using the Multiscale Model to Model Cloud Comparison (M3C2 plug-in). A first evaluation of the horizontal surface velocity was computed identifying corresponding features manually on the orthophotos through time and a second assessment was performed based on repeated GNSS campaigns. Surface velocity obtained by orthophotos manual identifications is validated against repeated GNSS measurements. The analysis shows a good correlation at all magnitudes with a R2 equal to 0.988 and RMSE of 26 cm.
The RG shows a clear distinction in creep dynamics between a faster western part (values up to 1.8 m/y) and a slower eastern part, with values below 0.1 m/y in the most upstream part. Considering the period 2012-2020, maximum peak of surface velocity is reached in 2015, followed by a velocity decrease until 2017-2018 when the smallest movements are recorded. However, the following two years (2018-2019 and 2019-2020) are marked by a gradual increase in surface horizontal velocity. The absence of significant of any significant movement in the upstream part is related to the lack of permafrost consecutive to the development and advance of a local glacier during the Little Ice Age. The slower eastern part is almost gently inclined and corresponds to a currently degrading part of the RG, with an ice melt-induced subsidence of up to 5 cm/year. The faster area is also the steepest, where the driving stress is also the largest. The presence of the frozen ground at depth, probably its structure and thermal state, but also the topographical settings are the main factors explaining the current RG flow pattern.
How to cite: Bearzot, F., Garzonio, R., Di Mauro, B., Hauck, C., Delaloye, R., Morra Di Cella, U., Cremonese, E., Pogliotti, P., Crosta, G. B., Colombo, R., Frattini, P., and Rossini, M.: Monitoring the dynamics of an alpine rock glacier with repeated UAV and GNSS data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14788, https://doi.org/10.5194/egusphere-egu21-14788, 2021.
EGU21-14661 | vPICO presentations | GM7.6
A complementary kinematic approach to inventory rock glaciers applied to case studies of the Swiss and Italian AlpsAldo Bertone, Chloé Barboux, Francesco Brardinoni, Reynald Delaloye, Volkmar Mair, Gabriel Pellegrinon, Tania Monier, and Tazio Strozzi
Rock glaciers are the best visual expression of creeping mountain permafrost. Their dynamics, which largely depend on climatic forcing, provide information about the mountain permafrost and may locally pose risk to infrastructures.
The International Permafrost Association (IPA) Action Group on Rock glacier inventories and kinematics, launched in 2018, fosters the activities of a research network focused on the definition of standardized guidelines for inventorying rock glaciers, including information on rock-glacier displacement rate. The ESA Permafrost_CCI project further sustains this initiative, and proposes a standardized method to implement kinematics-based rock glacier inventories.
The proposed method exploits interferometric data from spaceborne Synthetic Aperture Radar (InSAR) to derive the kinematic information of existing or newly-compiled rock glacier inventories. In particular, areas identified as slope movements within rock glacier polygons are delineated on interferograms as “moving areas”, and are assigned a velocity class. Subsequently, a specific kinematic class is assigned to each rock glacier unit according to the velocity class and extension of the relevant moving areas.
This method is applied on two regions: the Western part of the Swiss Alps and the South-Western part of the South Tyrol (Italian Alps). Both are located at the same latitude, with rock glaciers in the Swiss part lying at slightly higher altitudes, and experiencing higher mean annual precipitation. Rock glacier polygons were drawn from existing inventories, the kinematic information was extracted exploiting InSAR data acquired between 2018 and 2019 from the Sentinel-1 constellation.
In the Swiss and Italian parts, we inventoried 660 and 783 moving areas (1443 in total). Collectively, it was possible to assign a kinematic attribute to 913 rock glaciers, providing a more objective and quantitative activity classification (compared to the qualitative active, inactive, and relict categories). In the Swiss part, 14% of the rock glaciers are moving in the magnitude order of a meter/year or faster, 43% in the magnitude order of one to several dm/yr, 36% from one to several cm/yr, the others are with unreliable movements (7%). In the Italian part, these percentages are 1% (meter/year or faster), 42% (one to several dm/yr), 39% (one to several cm/yr) and 18% (no reliable), respectively. Preliminary analyses on the Italian part are conducted on 467 additional rock glaciers recognized as geomorphologically relict: 68% are not moving or not moving fast enough to be detected, 9% have sectors moving up to several cm/yr, and the remaining 23% of relict rock glaciers have no reliable information on movement.
Preliminary results show how this approach allows to provide complementary kinematic information to the geomorphological approach, improving the knowledge on the activity status in a given time and in a given region. Since several studies have reported trends towards displacement acceleration, applying this approach over long periods will allow assessing the response of a wide selection of landforms to (warmer) climatic forcing. Furthermore, this approach is a very useful tool to help select representative rock glaciers of a region, on which to apply more accurate monitoring approaches.
How to cite: Bertone, A., Barboux, C., Brardinoni, F., Delaloye, R., Mair, V., Pellegrinon, G., Monier, T., and Strozzi, T.: A complementary kinematic approach to inventory rock glaciers applied to case studies of the Swiss and Italian Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14661, https://doi.org/10.5194/egusphere-egu21-14661, 2021.
Rock glaciers are the best visual expression of creeping mountain permafrost. Their dynamics, which largely depend on climatic forcing, provide information about the mountain permafrost and may locally pose risk to infrastructures.
The International Permafrost Association (IPA) Action Group on Rock glacier inventories and kinematics, launched in 2018, fosters the activities of a research network focused on the definition of standardized guidelines for inventorying rock glaciers, including information on rock-glacier displacement rate. The ESA Permafrost_CCI project further sustains this initiative, and proposes a standardized method to implement kinematics-based rock glacier inventories.
The proposed method exploits interferometric data from spaceborne Synthetic Aperture Radar (InSAR) to derive the kinematic information of existing or newly-compiled rock glacier inventories. In particular, areas identified as slope movements within rock glacier polygons are delineated on interferograms as “moving areas”, and are assigned a velocity class. Subsequently, a specific kinematic class is assigned to each rock glacier unit according to the velocity class and extension of the relevant moving areas.
This method is applied on two regions: the Western part of the Swiss Alps and the South-Western part of the South Tyrol (Italian Alps). Both are located at the same latitude, with rock glaciers in the Swiss part lying at slightly higher altitudes, and experiencing higher mean annual precipitation. Rock glacier polygons were drawn from existing inventories, the kinematic information was extracted exploiting InSAR data acquired between 2018 and 2019 from the Sentinel-1 constellation.
In the Swiss and Italian parts, we inventoried 660 and 783 moving areas (1443 in total). Collectively, it was possible to assign a kinematic attribute to 913 rock glaciers, providing a more objective and quantitative activity classification (compared to the qualitative active, inactive, and relict categories). In the Swiss part, 14% of the rock glaciers are moving in the magnitude order of a meter/year or faster, 43% in the magnitude order of one to several dm/yr, 36% from one to several cm/yr, the others are with unreliable movements (7%). In the Italian part, these percentages are 1% (meter/year or faster), 42% (one to several dm/yr), 39% (one to several cm/yr) and 18% (no reliable), respectively. Preliminary analyses on the Italian part are conducted on 467 additional rock glaciers recognized as geomorphologically relict: 68% are not moving or not moving fast enough to be detected, 9% have sectors moving up to several cm/yr, and the remaining 23% of relict rock glaciers have no reliable information on movement.
Preliminary results show how this approach allows to provide complementary kinematic information to the geomorphological approach, improving the knowledge on the activity status in a given time and in a given region. Since several studies have reported trends towards displacement acceleration, applying this approach over long periods will allow assessing the response of a wide selection of landforms to (warmer) climatic forcing. Furthermore, this approach is a very useful tool to help select representative rock glaciers of a region, on which to apply more accurate monitoring approaches.
How to cite: Bertone, A., Barboux, C., Brardinoni, F., Delaloye, R., Mair, V., Pellegrinon, G., Monier, T., and Strozzi, T.: A complementary kinematic approach to inventory rock glaciers applied to case studies of the Swiss and Italian Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14661, https://doi.org/10.5194/egusphere-egu21-14661, 2021.
EGU21-11682 | vPICO presentations | GM7.6
Inferring rock glacier genesis and dynamics from age-layer modelling and borehole age-profileGwendolyn J.-M. C. Leysinger Vieli, Andreas Vieli, and Alessandro Cicoira
The genesis of rock glaciers differs fundamentally from ‘normal’ glaciers and results in much older landforms that are often reaching ages of several millennia. Recent datings of rock glacier material from boreholes indicate early Holocene ages for rock glaciers and allow the derivation of age-depth profiles at the borehole location. We use here a 2-dimensional numerical modelling approach that calculates age-layers (isochrones) within the rock glacier body and that considers the accretion, melt and flow-advection of rock glacier material. We apply this model to the case of Lazaun rock glacier (Southern Ötztal Alps) for which a well dated profile from a borehole exists, with ages at the bottom older than 9000 years (Krainer et al. 2015). With our modelling we are able to reproduce the observed age-depth profiles well and are able to infer a long-term accumulation rate that is around 1 cm/yr which is an order of magnitude higher than a previous estimate that does not account for deformation. The modelling is consistent with the classic rock glacier genesis of material accretion in the upstream talus slope and confirms the dominance of deformation in the shear-zone at the bottom layer of the rock glacier.
We conclude that combining age-layer modelling with dated depth-profiles of rock glaciers allows for important new insights into our understanding of rock glacier evolution and dynamics.
REFERENCES
Krainer, K., Bressan, D., Dietre, B., Haas, J., Hajdas, I., Lang, K. & Tonidandel, D. (2015). A 10,300-year-old permafrost core from the active rock glacier Lazaun, southern Oetztal Alps (South Tyrol, Northern Italy). Quaternary Research, 83 , 324-335.
How to cite: Leysinger Vieli, G. J.-M. C., Vieli, A., and Cicoira, A.: Inferring rock glacier genesis and dynamics from age-layer modelling and borehole age-profile, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11682, https://doi.org/10.5194/egusphere-egu21-11682, 2021.
The genesis of rock glaciers differs fundamentally from ‘normal’ glaciers and results in much older landforms that are often reaching ages of several millennia. Recent datings of rock glacier material from boreholes indicate early Holocene ages for rock glaciers and allow the derivation of age-depth profiles at the borehole location. We use here a 2-dimensional numerical modelling approach that calculates age-layers (isochrones) within the rock glacier body and that considers the accretion, melt and flow-advection of rock glacier material. We apply this model to the case of Lazaun rock glacier (Southern Ötztal Alps) for which a well dated profile from a borehole exists, with ages at the bottom older than 9000 years (Krainer et al. 2015). With our modelling we are able to reproduce the observed age-depth profiles well and are able to infer a long-term accumulation rate that is around 1 cm/yr which is an order of magnitude higher than a previous estimate that does not account for deformation. The modelling is consistent with the classic rock glacier genesis of material accretion in the upstream talus slope and confirms the dominance of deformation in the shear-zone at the bottom layer of the rock glacier.
We conclude that combining age-layer modelling with dated depth-profiles of rock glaciers allows for important new insights into our understanding of rock glacier evolution and dynamics.
REFERENCES
Krainer, K., Bressan, D., Dietre, B., Haas, J., Hajdas, I., Lang, K. & Tonidandel, D. (2015). A 10,300-year-old permafrost core from the active rock glacier Lazaun, southern Oetztal Alps (South Tyrol, Northern Italy). Quaternary Research, 83 , 324-335.
How to cite: Leysinger Vieli, G. J.-M. C., Vieli, A., and Cicoira, A.: Inferring rock glacier genesis and dynamics from age-layer modelling and borehole age-profile, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11682, https://doi.org/10.5194/egusphere-egu21-11682, 2021.
EGU21-2627 | vPICO presentations | GM7.6
Reconstruction of the dynamics and origin of rock glaciers in an Alpine environmentBenjamin Lehmann, Robert S. Anderson, Xavier Bodin, Pierre G. Valla, and Julien Carcaillet
Rock glaciers are one of the most frequent cryospheric landform in mid-latitude mountain ranges. They influence the evolution of alpine environments on short (years to decades) and long (centuries to millennia) time scales. As a visible expression of mountain permafrost [1] as well as an important water reserve in the form of ground ice [2], rock glaciers are seen as increasingly important in the evolution of geomorphology and hydrology of mountain systems in the context of climate change and deglaciation [3, 4]. On longer time scales, rock glaciers transport boulders produced by the erosion of the headwall upstream and downstream and therefore participate in shaping mountain slopes [5]. Despite their importance, the dynamics and origin of rock glaciers are poorly understood.
In this study, we propose to address two questions:
1) How does the dynamics of rock glaciers change over time?
2) What is the origin of rock glaciers and what is their influence on the evolution of alpine environments?
These two questions require an evaluation of the surface velocity field of rock glaciers by relating short and long time scales. To solve this problem, we combine complementary methods including remote sensing, geochronology with a mechanical model of rock glacier dynamics. We apply this approach to the rock glacier complex of the Vallon de la Route in the Massif du Combeynot (French alps).
In order to reconstruct the displacement field of the rock glacier on modern time scales, we used remote sensing methods (i.e., image correlation and InSAR). Over longer periods (103 to 104 years), we used cosmogenic terrestrial nuclides (TCN) dating. By applying this methodology to boulder surfaces at different positions along the central flow line of the rock glacier, from the headwall to its terminus, we will be able to convert the exposure ages into surface displacement. The use of dynamic modelling of rock glaciers [6] will allow us to relate the surface kinematics to short to long time scales. It will then be possible to discuss the age, origin of rock glaciers and how topo-climatic and geomorphological processes control their evolution in Alpine environment.
[1] Barsch, D.: Rockglaciers. Indicators for the Present and Former Geoecology in High Mountain Environments, Springer series in physical environment vol. 16, Springer, Berlin, Heidelberg, 1996.
[2] Jones, D. B., Harrison, S., Anderson, K., and Whalley, W. B.: Rock glaciers and mountain hydrology: A review, Earth-Sci Rev, 193, 66–90, 2019.
[3] Haeberli, W., Schaub, Y., and Huggel, C.: Increasing risks related to landslides from degrading permafrost into new lakes in deglaciating mountain ranges, Geomorphology, 293, 405–417, 2017.
[4] Knight, J., Harrison, S., and Jones, D. B.: Rock glaciers and the geomorphological evolution of deglacierizing mountains, Geomorphology, 324, 14–24, 2019.
[5] MacGregor, K.R., Anderson, R.S., Waddington, E.D.: Numerical modeling of glacial erosion and headwall processes in alpine valleys. Geomorphology 103 (2):189–204, 2009.
[6] Anderson, R. S., Anderson, L. S., Armstrong, W. H., Rossi, M. W., & Crump, S. E.: Glaciation of alpine valleys: The glacier–debris-covered glacier–rock glacier continuum. Geomorphology, 311, 127-142, 2018.
How to cite: Lehmann, B., Anderson, R. S., Bodin, X., Valla, P. G., and Carcaillet, J.: Reconstruction of the dynamics and origin of rock glaciers in an Alpine environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2627, https://doi.org/10.5194/egusphere-egu21-2627, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Rock glaciers are one of the most frequent cryospheric landform in mid-latitude mountain ranges. They influence the evolution of alpine environments on short (years to decades) and long (centuries to millennia) time scales. As a visible expression of mountain permafrost [1] as well as an important water reserve in the form of ground ice [2], rock glaciers are seen as increasingly important in the evolution of geomorphology and hydrology of mountain systems in the context of climate change and deglaciation [3, 4]. On longer time scales, rock glaciers transport boulders produced by the erosion of the headwall upstream and downstream and therefore participate in shaping mountain slopes [5]. Despite their importance, the dynamics and origin of rock glaciers are poorly understood.
In this study, we propose to address two questions:
1) How does the dynamics of rock glaciers change over time?
2) What is the origin of rock glaciers and what is their influence on the evolution of alpine environments?
These two questions require an evaluation of the surface velocity field of rock glaciers by relating short and long time scales. To solve this problem, we combine complementary methods including remote sensing, geochronology with a mechanical model of rock glacier dynamics. We apply this approach to the rock glacier complex of the Vallon de la Route in the Massif du Combeynot (French alps).
In order to reconstruct the displacement field of the rock glacier on modern time scales, we used remote sensing methods (i.e., image correlation and InSAR). Over longer periods (103 to 104 years), we used cosmogenic terrestrial nuclides (TCN) dating. By applying this methodology to boulder surfaces at different positions along the central flow line of the rock glacier, from the headwall to its terminus, we will be able to convert the exposure ages into surface displacement. The use of dynamic modelling of rock glaciers [6] will allow us to relate the surface kinematics to short to long time scales. It will then be possible to discuss the age, origin of rock glaciers and how topo-climatic and geomorphological processes control their evolution in Alpine environment.
[1] Barsch, D.: Rockglaciers. Indicators for the Present and Former Geoecology in High Mountain Environments, Springer series in physical environment vol. 16, Springer, Berlin, Heidelberg, 1996.
[2] Jones, D. B., Harrison, S., Anderson, K., and Whalley, W. B.: Rock glaciers and mountain hydrology: A review, Earth-Sci Rev, 193, 66–90, 2019.
[3] Haeberli, W., Schaub, Y., and Huggel, C.: Increasing risks related to landslides from degrading permafrost into new lakes in deglaciating mountain ranges, Geomorphology, 293, 405–417, 2017.
[4] Knight, J., Harrison, S., and Jones, D. B.: Rock glaciers and the geomorphological evolution of deglacierizing mountains, Geomorphology, 324, 14–24, 2019.
[5] MacGregor, K.R., Anderson, R.S., Waddington, E.D.: Numerical modeling of glacial erosion and headwall processes in alpine valleys. Geomorphology 103 (2):189–204, 2009.
[6] Anderson, R. S., Anderson, L. S., Armstrong, W. H., Rossi, M. W., & Crump, S. E.: Glaciation of alpine valleys: The glacier–debris-covered glacier–rock glacier continuum. Geomorphology, 311, 127-142, 2018.
How to cite: Lehmann, B., Anderson, R. S., Bodin, X., Valla, P. G., and Carcaillet, J.: Reconstruction of the dynamics and origin of rock glaciers in an Alpine environment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2627, https://doi.org/10.5194/egusphere-egu21-2627, 2021.
GM7.7 – Mountain and ice sheet glaciations potential and diversity: Glacial landforms and their palaeoclimatic interpretation
EGU21-8924 | vPICO presentations | GM7.7 | Highlight
Evidence for Holocene ice sheet history from geomorphology, cosmogenic isotopes, and bird vomit, East Antarctica.Mike Bentley, Dominic Hodgson, Andy Hein, Steve Binnie, and Steve Moreton
The post-LGM thinning history of the East Antarctic Ice Sheet is not yet well constrained. Here we report some integrated observations and analyses that constrain the ice sheet thinning history in Western Dronning Maud Land and Coats Land, adjacent to the easternmost Weddell Sea, which is a key area of uncertainty in ice sheet reconstructions. Geomorphological observations show a distinct series of weathering zones with fresh erratics only found in a relatively narrow zone above the present ice sheet margin. We report cosmogenic surface exposure dates of erratics in the different weathering zones, using 10Be and in situ 14C. We further report a large number of radiocarbon ages on sub-fossil bird vomit (regurgitated proventricular stomach oil, sometimes termed ‘mumiyo’) from nesting snow petrels (Pagodroma nivea) which record periods of ice sheet absence. Together these analyses allow us to determine a more tightly constrained thinning history of the ice sheet in this sector. We discuss the implications of this thinning history for geologically-based ice sheet reconstructions and for ice sheet models.
How to cite: Bentley, M., Hodgson, D., Hein, A., Binnie, S., and Moreton, S.: Evidence for Holocene ice sheet history from geomorphology, cosmogenic isotopes, and bird vomit, East Antarctica., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8924, https://doi.org/10.5194/egusphere-egu21-8924, 2021.
The post-LGM thinning history of the East Antarctic Ice Sheet is not yet well constrained. Here we report some integrated observations and analyses that constrain the ice sheet thinning history in Western Dronning Maud Land and Coats Land, adjacent to the easternmost Weddell Sea, which is a key area of uncertainty in ice sheet reconstructions. Geomorphological observations show a distinct series of weathering zones with fresh erratics only found in a relatively narrow zone above the present ice sheet margin. We report cosmogenic surface exposure dates of erratics in the different weathering zones, using 10Be and in situ 14C. We further report a large number of radiocarbon ages on sub-fossil bird vomit (regurgitated proventricular stomach oil, sometimes termed ‘mumiyo’) from nesting snow petrels (Pagodroma nivea) which record periods of ice sheet absence. Together these analyses allow us to determine a more tightly constrained thinning history of the ice sheet in this sector. We discuss the implications of this thinning history for geologically-based ice sheet reconstructions and for ice sheet models.
How to cite: Bentley, M., Hodgson, D., Hein, A., Binnie, S., and Moreton, S.: Evidence for Holocene ice sheet history from geomorphology, cosmogenic isotopes, and bird vomit, East Antarctica., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8924, https://doi.org/10.5194/egusphere-egu21-8924, 2021.
EGU21-47 | vPICO presentations | GM7.7
Fennoscandian Ice Sheet glaciation in northwest Arctic Russia during the Last Glacial-Interglacial TransitionBenjamin Boyes, Danni Pearce, and Lorna Linch
Previous attempts to reconstruct the glacial history of the last Fennoscandian Ice sheet (FIS) in northwest Arctic Russia have resulted in various Last Glacial-Interglacial Transition (c. 20-10 ka) scenarios, suggesting that the Kola Peninsula was glaciated by the FIS, the Ponoy Ice Cap, or the Kara Sea Ice Sheet. The conflicting glacial interpretations have stemmed, in part, from the use of low-resolution geomorphological and geological maps. The advent of high-resolution remotely-sensed imagery warrants a new glacial reconstruction of ice sheet dynamics in northwest Arctic Russia: we therefore present initial glacial interpretations based on new high-resolution geomorphological mapping.
Geomorphological mapping using high-resolution ArcticDEM and PlanetScope imagery has identified >245,000 glacial landforms, significantly increasing the volume and detail of geomorphological data in the region. Over 66,000 subglacial bedforms (subglacial lineations and subglacial ribs) are used to construct flowsets, which demonstrate that ice flowed from the Scandinavian mountains in the west and across the shield terrain of the Kola Peninsula. Moreover, four possible palaeo-ice streams are identified in the region. Mapping individual moraine hummocks, rather than hummocky moraine spreads as in previous mapping attempts, reveals multiple ice margins across the Kola Peninsula. A noteworthy ~25 km wide belt of hummocky moraines aligned north-south across the Kola Peninsula is tentatively attributed to the Younger Dryas (c. 12.8-11.9 ka) ice marginal zone. The so-called “ring-and-ridge” hummock moraines that are predominantly observed within this ice marginal zone suggest down-wasting and stagnant ice margins. The meltwater landform record also reveals subglacial channel networks along the northern coastline that suggest warm-based conditions of the ice sheet may have been induced by warm currents in the Barents Sea during the last glacial-interglacial transition.
This research will provide crucial empirical data for validating numerical model simulations of the FIS, which in turn will further our understanding of ice sheet dynamics in other Arctic, Antarctic, and Alpine regions.
How to cite: Boyes, B., Pearce, D., and Linch, L.: Fennoscandian Ice Sheet glaciation in northwest Arctic Russia during the Last Glacial-Interglacial Transition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-47, https://doi.org/10.5194/egusphere-egu21-47, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Previous attempts to reconstruct the glacial history of the last Fennoscandian Ice sheet (FIS) in northwest Arctic Russia have resulted in various Last Glacial-Interglacial Transition (c. 20-10 ka) scenarios, suggesting that the Kola Peninsula was glaciated by the FIS, the Ponoy Ice Cap, or the Kara Sea Ice Sheet. The conflicting glacial interpretations have stemmed, in part, from the use of low-resolution geomorphological and geological maps. The advent of high-resolution remotely-sensed imagery warrants a new glacial reconstruction of ice sheet dynamics in northwest Arctic Russia: we therefore present initial glacial interpretations based on new high-resolution geomorphological mapping.
Geomorphological mapping using high-resolution ArcticDEM and PlanetScope imagery has identified >245,000 glacial landforms, significantly increasing the volume and detail of geomorphological data in the region. Over 66,000 subglacial bedforms (subglacial lineations and subglacial ribs) are used to construct flowsets, which demonstrate that ice flowed from the Scandinavian mountains in the west and across the shield terrain of the Kola Peninsula. Moreover, four possible palaeo-ice streams are identified in the region. Mapping individual moraine hummocks, rather than hummocky moraine spreads as in previous mapping attempts, reveals multiple ice margins across the Kola Peninsula. A noteworthy ~25 km wide belt of hummocky moraines aligned north-south across the Kola Peninsula is tentatively attributed to the Younger Dryas (c. 12.8-11.9 ka) ice marginal zone. The so-called “ring-and-ridge” hummock moraines that are predominantly observed within this ice marginal zone suggest down-wasting and stagnant ice margins. The meltwater landform record also reveals subglacial channel networks along the northern coastline that suggest warm-based conditions of the ice sheet may have been induced by warm currents in the Barents Sea during the last glacial-interglacial transition.
This research will provide crucial empirical data for validating numerical model simulations of the FIS, which in turn will further our understanding of ice sheet dynamics in other Arctic, Antarctic, and Alpine regions.
How to cite: Boyes, B., Pearce, D., and Linch, L.: Fennoscandian Ice Sheet glaciation in northwest Arctic Russia during the Last Glacial-Interglacial Transition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-47, https://doi.org/10.5194/egusphere-egu21-47, 2021.
EGU21-584 | vPICO presentations | GM7.7
Downscaling CESM2 in CLM5 to Hindcast Pre-Industrial Equilibrium Line Altitude for Tropical MountainsNicholas Heavens
Highland environments are rarely preserved in the geological record, particularly from as early as the Paleozoic Era. However, several stratigraphic locations are now known which definitely or potentially preserve such environments near the paleoequator during the Late Carboniferous and Early Permian Periods, during which the Earth was in the depths of an icehouse climate like that of the Pliocene and Pleistocene Epochs, the Late Paleozoic Ice Age (LPIA). Several of these locations contain evidence of mountain glaciation at altitudes below 2000 m, leading to questions about the significance of tropical mountain glaciation for global climate during this interval of geologic time. However, climate model simulations for the LPIA have not been able to simulate mountain glaciation like that inferred from the geological record, possibly because of low resolution, incorrect boundary conditions, or climate model bias resulting from incomplete representation of moist convective processes impacting tropical lapse rates.
The overarching purpose of this study is to develop a climate modeling framework that enables the significance of mountain glaciation for global paleoclimate to be evaluated. Ideally, such a framework would allow low-resolution global model output to be downscaled to the scale of a mountain range to calculate the equilibrium line altitude and similar parameters, enabling evidence of mountain glaciation in the deep past to be used to constrain/tune the low-resolution global models. While this study was designed to inform a specific problem in deep time paleoclimate, its results are likely broadly applicable to assessing how well mountain glaciation is captured by global climate modeling of the past, present, and future.
Here, I present a framework in which the CMIP6 pre-industrial control simulation for the Community Earth System Model version 2 (CESM2) at 0.9°x1.25° resolution is used to generate a data atmosphere for the Community Land Model version 5 (CLM5) run at 0.01° resolution in 10 tropical and 1 mid-latitude domain to study the surface mass balance over the domain. For computational reasons, glaciation is assumed to cover a small portion of each grid cell, but surface mass balance still can be evaluated. Topographic boundary conditions come from GMTED2010, but most other information is directly interpolated from the CESM2 simulation. CLM5 simulations require a fixed lapse rate to be assumed, which is varied in each CLM5 simulation across six different values. The CLM5 simulation output along with the mean tropical lapse rate in the CESM2 simulation is then used to evaluate the various biases of this framework in comparison with estimated pre-industrial equilibrium line altitudes for the studied domains.
This work is supported by the National Science Foundation (USA) under grant EAR-1849754.
How to cite: Heavens, N.: Downscaling CESM2 in CLM5 to Hindcast Pre-Industrial Equilibrium Line Altitude for Tropical Mountains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-584, https://doi.org/10.5194/egusphere-egu21-584, 2021.
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Highland environments are rarely preserved in the geological record, particularly from as early as the Paleozoic Era. However, several stratigraphic locations are now known which definitely or potentially preserve such environments near the paleoequator during the Late Carboniferous and Early Permian Periods, during which the Earth was in the depths of an icehouse climate like that of the Pliocene and Pleistocene Epochs, the Late Paleozoic Ice Age (LPIA). Several of these locations contain evidence of mountain glaciation at altitudes below 2000 m, leading to questions about the significance of tropical mountain glaciation for global climate during this interval of geologic time. However, climate model simulations for the LPIA have not been able to simulate mountain glaciation like that inferred from the geological record, possibly because of low resolution, incorrect boundary conditions, or climate model bias resulting from incomplete representation of moist convective processes impacting tropical lapse rates.
The overarching purpose of this study is to develop a climate modeling framework that enables the significance of mountain glaciation for global paleoclimate to be evaluated. Ideally, such a framework would allow low-resolution global model output to be downscaled to the scale of a mountain range to calculate the equilibrium line altitude and similar parameters, enabling evidence of mountain glaciation in the deep past to be used to constrain/tune the low-resolution global models. While this study was designed to inform a specific problem in deep time paleoclimate, its results are likely broadly applicable to assessing how well mountain glaciation is captured by global climate modeling of the past, present, and future.
Here, I present a framework in which the CMIP6 pre-industrial control simulation for the Community Earth System Model version 2 (CESM2) at 0.9°x1.25° resolution is used to generate a data atmosphere for the Community Land Model version 5 (CLM5) run at 0.01° resolution in 10 tropical and 1 mid-latitude domain to study the surface mass balance over the domain. For computational reasons, glaciation is assumed to cover a small portion of each grid cell, but surface mass balance still can be evaluated. Topographic boundary conditions come from GMTED2010, but most other information is directly interpolated from the CESM2 simulation. CLM5 simulations require a fixed lapse rate to be assumed, which is varied in each CLM5 simulation across six different values. The CLM5 simulation output along with the mean tropical lapse rate in the CESM2 simulation is then used to evaluate the various biases of this framework in comparison with estimated pre-industrial equilibrium line altitudes for the studied domains.
This work is supported by the National Science Foundation (USA) under grant EAR-1849754.
How to cite: Heavens, N.: Downscaling CESM2 in CLM5 to Hindcast Pre-Industrial Equilibrium Line Altitude for Tropical Mountains, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-584, https://doi.org/10.5194/egusphere-egu21-584, 2021.
EGU21-691 | vPICO presentations | GM7.7
Deglaciation of the central sector of the Cordilleran Ice Sheet in northern British ColumbiaHelen Dulfer and Martin Margold
The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet at the Last Glacial Maximum. Numerical modelling studies of the CIS during the last glacial-interglacial cycle indicate the central sector of this ice sheet, located in mountainous northern British Columbia, played an important role during both the advance and retreat phases. Additionally, the models indicate that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. The abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the subsequent cooling caused the expansion of alpine glaciers across the former central sector of the CIS. However, the mountainous terrain and remote location have thus far impeded our understanding of this important region of the CIS, and the ice sheet configuration during the Late Glacial remains poorly constrained.
Here we use the glacial landform record to reconstruct the deglaciation dynamics of the central sector of the CIS during the Late Pleistocene climate reversals. Numerous high elevation meltwater channels suggests the early emergence of mountain peaks above the ice sheet and the configuration of ice marginal landforms, particularly lateral meltwater channels, eskers, kame terraces and ice-contact deltas, allows the westward retreat of the ice margin to be traced towards ice dispersal centres in the Skeena and Coast mountains. Hundreds of arcuate, sharp-crested terminal moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS and numerical dating indicates that this readvance occurred during the Late Glacial period. Additionally, at some locations, cross-cutting relationships preserve the interaction of the local readvance glaciers with the trunk glaciers of the CIS, allowing the extent of the central sector of the CIS during the Late Glacial period to be reconstructed for the first time.
How to cite: Dulfer, H. and Margold, M.: Deglaciation of the central sector of the Cordilleran Ice Sheet in northern British Columbia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-691, https://doi.org/10.5194/egusphere-egu21-691, 2021.
The Cordilleran Ice Sheet (CIS) repeatedly covered western Canada during the Pleistocene and attained a volume and area similar to that of the present-day Greenland Ice Sheet at the Last Glacial Maximum. Numerical modelling studies of the CIS during the last glacial-interglacial cycle indicate the central sector of this ice sheet, located in mountainous northern British Columbia, played an important role during both the advance and retreat phases. Additionally, the models indicate that the rapid climate oscillations at the end of the Pleistocene had a dramatic effect on the CIS. The abrupt warming at the onset of the Bølling-Allerød caused significant thinning of the ice sheet, resulting in a fifty percent reduction in mass, while the subsequent cooling caused the expansion of alpine glaciers across the former central sector of the CIS. However, the mountainous terrain and remote location have thus far impeded our understanding of this important region of the CIS, and the ice sheet configuration during the Late Glacial remains poorly constrained.
Here we use the glacial landform record to reconstruct the deglaciation dynamics of the central sector of the CIS during the Late Pleistocene climate reversals. Numerous high elevation meltwater channels suggests the early emergence of mountain peaks above the ice sheet and the configuration of ice marginal landforms, particularly lateral meltwater channels, eskers, kame terraces and ice-contact deltas, allows the westward retreat of the ice margin to be traced towards ice dispersal centres in the Skeena and Coast mountains. Hundreds of arcuate, sharp-crested terminal moraines delineate the extent of alpine glaciers, ice caps and ice fields that regrew on mountain peaks above the CIS and numerical dating indicates that this readvance occurred during the Late Glacial period. Additionally, at some locations, cross-cutting relationships preserve the interaction of the local readvance glaciers with the trunk glaciers of the CIS, allowing the extent of the central sector of the CIS during the Late Glacial period to be reconstructed for the first time.
How to cite: Dulfer, H. and Margold, M.: Deglaciation of the central sector of the Cordilleran Ice Sheet in northern British Columbia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-691, https://doi.org/10.5194/egusphere-egu21-691, 2021.
EGU21-771 | vPICO presentations | GM7.7
Timing and Extent of Late Quaternary Glaciation in the Ahuriri River Valley, Southern Alps, New ZealandLevan Tielidze, Shaun Eaves, Kevin Norton, and Andrew Mackintosh
Some valleys in South Island, New Zealand already have a number of well-dated glacier records. However, understanding of the precise timing of old glacial events in many valleys still remains poor. For this purpose, the cosmogenic 10Be surface exposure dating technique was used to constrain the timing and extent of late Quaternary glaciation in the Ahuriri River valley, Southern Alps, New Zealand. The 33 10Be surface-exposure ages from two different moraine complexes range from 16.6±0.4 ka to 19.7±0.5 ka suggesting rapid glacier recession (~17 km) during the last deglaciation.
Field observation and geomorphological mapping were also used to investigate the extent and drivers of glaciation in this valley. For the final step, we created detail and comprehensive map of the glacial geomorphology in an area covered by palaeo Ahuriri Glacier, in the central Southern Alps. Geomorphological mapping from high-resolution aerial imagery, large scale topographical maps, average resolution DEM, and several field investigations allowed us to produce the 1:38,000 scale map for the entire study site covering an area of about 532 km2.
This newly created map along with the new 10Be surface exposure dataset will help us in better understanding of past glacier-climate interactions in the Southern Alps and in the Southern Hemisphere in general.
How to cite: Tielidze, L., Eaves, S., Norton, K., and Mackintosh, A.: Timing and Extent of Late Quaternary Glaciation in the Ahuriri River Valley, Southern Alps, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-771, https://doi.org/10.5194/egusphere-egu21-771, 2021.
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Some valleys in South Island, New Zealand already have a number of well-dated glacier records. However, understanding of the precise timing of old glacial events in many valleys still remains poor. For this purpose, the cosmogenic 10Be surface exposure dating technique was used to constrain the timing and extent of late Quaternary glaciation in the Ahuriri River valley, Southern Alps, New Zealand. The 33 10Be surface-exposure ages from two different moraine complexes range from 16.6±0.4 ka to 19.7±0.5 ka suggesting rapid glacier recession (~17 km) during the last deglaciation.
Field observation and geomorphological mapping were also used to investigate the extent and drivers of glaciation in this valley. For the final step, we created detail and comprehensive map of the glacial geomorphology in an area covered by palaeo Ahuriri Glacier, in the central Southern Alps. Geomorphological mapping from high-resolution aerial imagery, large scale topographical maps, average resolution DEM, and several field investigations allowed us to produce the 1:38,000 scale map for the entire study site covering an area of about 532 km2.
This newly created map along with the new 10Be surface exposure dataset will help us in better understanding of past glacier-climate interactions in the Southern Alps and in the Southern Hemisphere in general.
How to cite: Tielidze, L., Eaves, S., Norton, K., and Mackintosh, A.: Timing and Extent of Late Quaternary Glaciation in the Ahuriri River Valley, Southern Alps, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-771, https://doi.org/10.5194/egusphere-egu21-771, 2021.
EGU21-975 | vPICO presentations | GM7.7
Dynamics of the last Scandinavian Ice Sheet’s southernmost sector revealed by the pattern of ice streamsIzabela Szuman, Jakub Z. Kalita, Marek W. Ewertowski, Chris D. Clark, and Stephen J. Livingstone
The Polish sector of the last Scandinavian Ice Sheet is a key area for studying ice sheet drainage and decay from its local Last Glacial Maximum (LGM) extent, as it is located at the terrestrial terminus of the large and dynamic Baltic Ice Stream Complex. Geomorphological mapping, based on a 0.4 m LIDAR digital elevation model, revealed about 940 streamlined bedforms, many of which are shown for the first time and consisting of mega-scale glacial lineations and drumlins. The lineation flow-sets together with associated landforms were used to identify seventeen ice streams, occupying 80% of the study area. We demonstrated that subtle topographic variations played an important role in influencing ice sheet dynamics. Variations in ice dynamics were a response to external climatic forcing that controlled deglaciation at the ice sheet scale as well as internal reorganisation due to the influence of topography, subglacial hydrology and glacier thermal regime. During the local LGM, the southern sector of the Scandinavian Ice Sheet in Poland was dominated by four simultaneously operating ice streams, likely active for several millennia, followed by fast active recession interrupted by three main periods of ice stream stagnation. Increased ice flow
dynamics during the period of the Young Baltic advances is suggested to be caused by variations in subglacial hydrology and the polythermal structure of the ice sheet.
How to cite: Szuman, I., Kalita, J. Z., Ewertowski, M. W., Clark, C. D., and Livingstone, S. J.: Dynamics of the last Scandinavian Ice Sheet’s southernmost sector revealed by the pattern of ice streams , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-975, https://doi.org/10.5194/egusphere-egu21-975, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The Polish sector of the last Scandinavian Ice Sheet is a key area for studying ice sheet drainage and decay from its local Last Glacial Maximum (LGM) extent, as it is located at the terrestrial terminus of the large and dynamic Baltic Ice Stream Complex. Geomorphological mapping, based on a 0.4 m LIDAR digital elevation model, revealed about 940 streamlined bedforms, many of which are shown for the first time and consisting of mega-scale glacial lineations and drumlins. The lineation flow-sets together with associated landforms were used to identify seventeen ice streams, occupying 80% of the study area. We demonstrated that subtle topographic variations played an important role in influencing ice sheet dynamics. Variations in ice dynamics were a response to external climatic forcing that controlled deglaciation at the ice sheet scale as well as internal reorganisation due to the influence of topography, subglacial hydrology and glacier thermal regime. During the local LGM, the southern sector of the Scandinavian Ice Sheet in Poland was dominated by four simultaneously operating ice streams, likely active for several millennia, followed by fast active recession interrupted by three main periods of ice stream stagnation. Increased ice flow
dynamics during the period of the Young Baltic advances is suggested to be caused by variations in subglacial hydrology and the polythermal structure of the ice sheet.
How to cite: Szuman, I., Kalita, J. Z., Ewertowski, M. W., Clark, C. D., and Livingstone, S. J.: Dynamics of the last Scandinavian Ice Sheet’s southernmost sector revealed by the pattern of ice streams , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-975, https://doi.org/10.5194/egusphere-egu21-975, 2021.
EGU21-1153 | vPICO presentations | GM7.7
Reconstructing the Holocene glacial history of northern NorwayJoshua Leigh, Chris Stokes, David Evans, Richard Jones, Liss Andreassen, and Rachel Carr
Detailed investigations into Holocene glacier fluctuations are a fundamental tool in developing reliable reconstructions of past climate variability and the detection of global climate change. There are, however, many mountain areas that have escaped detailed scrutiny. Here we present a large-scale glacial geomorphological and geochronological study of the central Troms and Finnmark county region in Arctic Norway (covering an area of 6,810 km2) in order to reconstruct glacier change from the early Holocene to present. We undertake the first glacial chronological study in the Rotsund Valley, central Troms and Finnmark county, based on moraine dating using a combination of absolute, calibrated, and relative age dating techniques (terrestrial cosmogenic nuclide dating (TCND), Schmidt hammer dating, and soil chronosequencing). Together with our chronological data, our detailed mapping from a much wider area reveals a complex picture of early-Holocene deglaciation and late-Holocene glacier re-advance and we postulate that specific moraine formations are linked to key climatic events including: the Erdalen Event (between 10,100 and 9,700 cal. yrs. BP), the Finse / ‘8.2 ka' Event (between 8,500 and 8,000 cal. yrs. BP), and the Neoglacial (from ~4,500 cal. yrs. BP to the LIA maximum).
How to cite: Leigh, J., Stokes, C., Evans, D., Jones, R., Andreassen, L., and Carr, R.: Reconstructing the Holocene glacial history of northern Norway , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1153, https://doi.org/10.5194/egusphere-egu21-1153, 2021.
Detailed investigations into Holocene glacier fluctuations are a fundamental tool in developing reliable reconstructions of past climate variability and the detection of global climate change. There are, however, many mountain areas that have escaped detailed scrutiny. Here we present a large-scale glacial geomorphological and geochronological study of the central Troms and Finnmark county region in Arctic Norway (covering an area of 6,810 km2) in order to reconstruct glacier change from the early Holocene to present. We undertake the first glacial chronological study in the Rotsund Valley, central Troms and Finnmark county, based on moraine dating using a combination of absolute, calibrated, and relative age dating techniques (terrestrial cosmogenic nuclide dating (TCND), Schmidt hammer dating, and soil chronosequencing). Together with our chronological data, our detailed mapping from a much wider area reveals a complex picture of early-Holocene deglaciation and late-Holocene glacier re-advance and we postulate that specific moraine formations are linked to key climatic events including: the Erdalen Event (between 10,100 and 9,700 cal. yrs. BP), the Finse / ‘8.2 ka' Event (between 8,500 and 8,000 cal. yrs. BP), and the Neoglacial (from ~4,500 cal. yrs. BP to the LIA maximum).
How to cite: Leigh, J., Stokes, C., Evans, D., Jones, R., Andreassen, L., and Carr, R.: Reconstructing the Holocene glacial history of northern Norway , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1153, https://doi.org/10.5194/egusphere-egu21-1153, 2021.
EGU21-2163 | vPICO presentations | GM7.7
The sediment-landform assemblage in the forefield of the Gepatsch Glacier, Tirol, Austria and its preservation potentialDaniel Le Heron, Bethan Davies, Lars Scharfenberg, Christoph Kettler, Michael Ketterman, Gerit Griesmeier, Rhiannon Quinn, Lukas Eder, Xiaoshuai Chen, Thomas Vandyk, and Marie Busfield
Ongoing monitoring of the Gepatsch Glacier, Tirol (Austria) consists of a multifaceted, interdisciplinary project which aims to characterise short term (diurnal in the summer melt season) and longer term (annual to decadal) changes to the glacier snout and forefield in the context of a rapid retreating valley glacier. The glacial valley and forefield comprises amphibolites, para- and orthogneisses that have been smoothed and striated into whalebacks, compound bedrock-sediment bedforms (crag and tail structures), flutes, and annual moraines. The glacial sediments and landforms are undergoing incision and terrace development by meltwater streams. As part of a long term goal to characterise the rates of erosion, sedimentation, and re-deposition, we return to the same site each year in mid-July to collect airborne data with an UAV (Mavic Pro drone) that allows us to produce orthophotos and digital elevation models. We compute the daily and annual elevation changes, allowing us determine zones of erosion and deposition. Measureable evidence for erosion of flutes in the immediate glacial forefield has occurred over a 12-month time period. Till deposited within the last 20 years has undergone substantial mass wasting and re-deposition as subaerial mass flows, or reworked into stream deposits. The lee side of many whaleback structures completely lacks subglacial sediment, and contains instead a sand and gravel deposit interpreted to result from waterlain deposition. Thus, this case study area offers insight into the rates of erosion and deposition in a complex, proglacial setting, allowing some of these processes to be quantified for the first time. This approach is expected to yield a better understanding of the preservation potential of proglacial sedimentary facies, and hence their preservation potential in Earth’s sedimentary record.
How to cite: Le Heron, D., Davies, B., Scharfenberg, L., Kettler, C., Ketterman, M., Griesmeier, G., Quinn, R., Eder, L., Chen, X., Vandyk, T., and Busfield, M.: The sediment-landform assemblage in the forefield of the Gepatsch Glacier, Tirol, Austria and its preservation potential, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2163, https://doi.org/10.5194/egusphere-egu21-2163, 2021.
Ongoing monitoring of the Gepatsch Glacier, Tirol (Austria) consists of a multifaceted, interdisciplinary project which aims to characterise short term (diurnal in the summer melt season) and longer term (annual to decadal) changes to the glacier snout and forefield in the context of a rapid retreating valley glacier. The glacial valley and forefield comprises amphibolites, para- and orthogneisses that have been smoothed and striated into whalebacks, compound bedrock-sediment bedforms (crag and tail structures), flutes, and annual moraines. The glacial sediments and landforms are undergoing incision and terrace development by meltwater streams. As part of a long term goal to characterise the rates of erosion, sedimentation, and re-deposition, we return to the same site each year in mid-July to collect airborne data with an UAV (Mavic Pro drone) that allows us to produce orthophotos and digital elevation models. We compute the daily and annual elevation changes, allowing us determine zones of erosion and deposition. Measureable evidence for erosion of flutes in the immediate glacial forefield has occurred over a 12-month time period. Till deposited within the last 20 years has undergone substantial mass wasting and re-deposition as subaerial mass flows, or reworked into stream deposits. The lee side of many whaleback structures completely lacks subglacial sediment, and contains instead a sand and gravel deposit interpreted to result from waterlain deposition. Thus, this case study area offers insight into the rates of erosion and deposition in a complex, proglacial setting, allowing some of these processes to be quantified for the first time. This approach is expected to yield a better understanding of the preservation potential of proglacial sedimentary facies, and hence their preservation potential in Earth’s sedimentary record.
How to cite: Le Heron, D., Davies, B., Scharfenberg, L., Kettler, C., Ketterman, M., Griesmeier, G., Quinn, R., Eder, L., Chen, X., Vandyk, T., and Busfield, M.: The sediment-landform assemblage in the forefield of the Gepatsch Glacier, Tirol, Austria and its preservation potential, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2163, https://doi.org/10.5194/egusphere-egu21-2163, 2021.
EGU21-2923 | vPICO presentations | GM7.7
Post-LGM evolution of the Dora Baltea glacial system and paleoclimatic implications in the Western Italian AlpsElena Serra, Pierre G. Valla, Natacha Gribenski, Fabio Magrani, Julien Carcaillet, and Philip Deline
Alpine glaciers repeatedly advanced and retreated from the high Alps to the forelands during the Quaternary and most recently reached their maximum extent and thickness during the Last Glacial Maximum (LGM, 26.5-19.0 ka ago) [1]. After the LGM, glaciers abandoned the Alpine foreland and retreated within the internal valleys. However, post-LGM withdrawal was not continuous but interrupted by stages of ice stasis or re-advance (stadials [2]), related to episodes of temporary climatic cooling. Glacial landforms and deposits associated to post-LGM ice stadials have been recognised across the Alps [2]. Our study contributes to this line of research by quantitatively reconstructing the age and configuration of several ice stages from the LGM to the Holocene, within the Dora Baltea (DB) catchment (SW Alps, Italy).
Following a detailed geomorphological mapping of glacial landforms and deposits, sixteen erratic boulders and two glacially-polished bedrocks were sampled along the DB valley for in-situ 10Be surface-exposure dating, and five samples for luminescence dating were collected from fluvio-lacustrine and fluvio-glacial deposits. The obtained chronologies, combined with recalculated 10Be surface-exposure ages from previous works in the study area [1, 3, 4, 5], constrain seven post-LGM ice stages in the DB valley. The first three retreat stages occurred between the end of the LGM and the early Lateglacial, probably with rapid ice decay. The following three stages correspond to the well-known Gschnitz, Daun and Egesen Alpine Lateglacial stadials [2], while we also identified a late-Holocene ice re-advance in the upstream DB catchment.
Paleo-ice configurations of each stage (including the LGM) were obtained with a semi-automatic ArcGIS routine (similar approach to GlaRe ArcGIS toolbox [6]), based on the areal interpolation of 2D ice surface profiles generated through Profiler v.2 [7]. Glacier equilibrium-line altitudes (ELAs) were computed for the eight 3D ice surface reconstructions [8], with the aim of deriving potential paleoclimatic implications of the different reconstructed ice stages in comparison to other paleoclimatic proxies.
References
[1] Wirsig, C. et al., 2016, Quaternary Science Reviews.
[2] Ivy-ochs, S., 2015, Cuadernos de Investigación Geográfica.
[3] Gianotti, F. et al., 2015, Alpine and Mediterranean Quaternary.
[4] Deline, P. et al., 2015, Quaternary Science Reviews.
[5] Le Roy, M., 2012. Université Grenoble Alpes.
[6] Pellitero, R. et al., 2016, Computers and Geosciences.
[7] Benn, D., Hulton, N., 2010, Quaternary Science Reviews.
[8] Pellitero, R. et al., 2015, Computers and Geosciences.
How to cite: Serra, E., Valla, P. G., Gribenski, N., Magrani, F., Carcaillet, J., and Deline, P.: Post-LGM evolution of the Dora Baltea glacial system and paleoclimatic implications in the Western Italian Alps , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2923, https://doi.org/10.5194/egusphere-egu21-2923, 2021.
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Alpine glaciers repeatedly advanced and retreated from the high Alps to the forelands during the Quaternary and most recently reached their maximum extent and thickness during the Last Glacial Maximum (LGM, 26.5-19.0 ka ago) [1]. After the LGM, glaciers abandoned the Alpine foreland and retreated within the internal valleys. However, post-LGM withdrawal was not continuous but interrupted by stages of ice stasis or re-advance (stadials [2]), related to episodes of temporary climatic cooling. Glacial landforms and deposits associated to post-LGM ice stadials have been recognised across the Alps [2]. Our study contributes to this line of research by quantitatively reconstructing the age and configuration of several ice stages from the LGM to the Holocene, within the Dora Baltea (DB) catchment (SW Alps, Italy).
Following a detailed geomorphological mapping of glacial landforms and deposits, sixteen erratic boulders and two glacially-polished bedrocks were sampled along the DB valley for in-situ 10Be surface-exposure dating, and five samples for luminescence dating were collected from fluvio-lacustrine and fluvio-glacial deposits. The obtained chronologies, combined with recalculated 10Be surface-exposure ages from previous works in the study area [1, 3, 4, 5], constrain seven post-LGM ice stages in the DB valley. The first three retreat stages occurred between the end of the LGM and the early Lateglacial, probably with rapid ice decay. The following three stages correspond to the well-known Gschnitz, Daun and Egesen Alpine Lateglacial stadials [2], while we also identified a late-Holocene ice re-advance in the upstream DB catchment.
Paleo-ice configurations of each stage (including the LGM) were obtained with a semi-automatic ArcGIS routine (similar approach to GlaRe ArcGIS toolbox [6]), based on the areal interpolation of 2D ice surface profiles generated through Profiler v.2 [7]. Glacier equilibrium-line altitudes (ELAs) were computed for the eight 3D ice surface reconstructions [8], with the aim of deriving potential paleoclimatic implications of the different reconstructed ice stages in comparison to other paleoclimatic proxies.
References
[1] Wirsig, C. et al., 2016, Quaternary Science Reviews.
[2] Ivy-ochs, S., 2015, Cuadernos de Investigación Geográfica.
[3] Gianotti, F. et al., 2015, Alpine and Mediterranean Quaternary.
[4] Deline, P. et al., 2015, Quaternary Science Reviews.
[5] Le Roy, M., 2012. Université Grenoble Alpes.
[6] Pellitero, R. et al., 2016, Computers and Geosciences.
[7] Benn, D., Hulton, N., 2010, Quaternary Science Reviews.
[8] Pellitero, R. et al., 2015, Computers and Geosciences.
How to cite: Serra, E., Valla, P. G., Gribenski, N., Magrani, F., Carcaillet, J., and Deline, P.: Post-LGM evolution of the Dora Baltea glacial system and paleoclimatic implications in the Western Italian Alps , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2923, https://doi.org/10.5194/egusphere-egu21-2923, 2021.
EGU21-3827 | vPICO presentations | GM7.7
Ice-dammed lakes of Scandinavia - a key to the pattern and chronology of the final decay of the Scandinavian Ice SheetCarl Regnéll, Robin Blomdin, Bradley W. Goodfellow, Sarah L. Greenwood, Richard Gyllencreutz, Jan Mangerud, Henrik Mikko, Gustaf Peterson Becher, Joachim Regnéll, John Inge Svendsen, and Christian Öhrling
Here we present the use of ice-dammed lake-related landforms and sediments for reconstructing the final phases of decay of the Scandinavian Ice Sheet.
In the late stages of the deglaciation, extensive glacial lakes were dammed between the easterly retreating Scandinavian Ice Sheet and the water divide within the mountains to the west. Using high-resolution airborne LiDAR-data, shorelines and other landforms relating to these ice-dammed lakes have now been discovered over larger areas and in greater numbers than previously known, opening a treasure trove of palaeoglaciological information of vast potential for reconstructing the final decay phase of the Scandinavian Ice Sheet.
The geomorphological imprint of the ice-dammed lakes is of particular importance in northern Scandinavia, as geological evidence pertaining unequivocally to the final ice sheet decay is sparse. Its interpretation is complicated since the ice sheet is thought to have mainly been cold-based during final decay, inhibiting sliding at the ice-bed interface and limiting the construction (or destruction) of landforms indicative of the changing shape and flow of the ice sheet. Furthermore, dated sediment sequences marking the onset of ice-free conditions are woefully few in northern Scandinavia. Likewise, available cosmogenic nuclide exposure dates provide high age uncertainty and inadequate geographical cover, leaving the timing and location of final ice sheet decay still elusive.
Using examples from northern and central Scandinavia, we show that ice-dammed lakes are an intricate part of the deglacial dynamics and show how mapping and dating them offer a solution to these problems. Even with a frozen ice-bed interface, surface melting and meltwater drainage creates landforms unequivocally associated with ice sheet decay: drainage channels, dammed lake shorelines, and deltas. Meltwater drainage routes and ice-dammed lakes are therefore powerful tools for reconstructing a disintegrating ice sheet; a ponded lake reveals the location of its requisite ice-dam, and drainage pathways reveal ice-free conditions. A dated sequence of ice-dammed lake sediments can therefore constrain both ice and lake coverage at that time for a much larger area than the dated site itself. Furthermore, the extent of different ice-dammed lake stages and their requisite ice-damming positions enables the pattern of ice margin change to be traced, and the relative age of ice-marginal positions determined using cross-cutting relations. The shorelines’ present-day tilts are also used to inform patterns and magnitudes of postglacial isostatic uplift, information otherwise lacking from the continental interior but of particular importance for modelling former ice sheet volumes and understanding the crustal response to ice sheet loading. Reconstructing the extents and timing of ice-dammed lakes and the study of related landforms and deposits can therefore greatly improve our understanding of the final decay of the Scandinavian Ice Sheet and provide potential analogues for the predicted future behaviours of modern ice sheets.
How to cite: Regnéll, C., Blomdin, R., Goodfellow, B. W., Greenwood, S. L., Gyllencreutz, R., Mangerud, J., Mikko, H., Peterson Becher, G., Regnéll, J., Svendsen, J. I., and Öhrling, C.: Ice-dammed lakes of Scandinavia - a key to the pattern and chronology of the final decay of the Scandinavian Ice Sheet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3827, https://doi.org/10.5194/egusphere-egu21-3827, 2021.
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Here we present the use of ice-dammed lake-related landforms and sediments for reconstructing the final phases of decay of the Scandinavian Ice Sheet.
In the late stages of the deglaciation, extensive glacial lakes were dammed between the easterly retreating Scandinavian Ice Sheet and the water divide within the mountains to the west. Using high-resolution airborne LiDAR-data, shorelines and other landforms relating to these ice-dammed lakes have now been discovered over larger areas and in greater numbers than previously known, opening a treasure trove of palaeoglaciological information of vast potential for reconstructing the final decay phase of the Scandinavian Ice Sheet.
The geomorphological imprint of the ice-dammed lakes is of particular importance in northern Scandinavia, as geological evidence pertaining unequivocally to the final ice sheet decay is sparse. Its interpretation is complicated since the ice sheet is thought to have mainly been cold-based during final decay, inhibiting sliding at the ice-bed interface and limiting the construction (or destruction) of landforms indicative of the changing shape and flow of the ice sheet. Furthermore, dated sediment sequences marking the onset of ice-free conditions are woefully few in northern Scandinavia. Likewise, available cosmogenic nuclide exposure dates provide high age uncertainty and inadequate geographical cover, leaving the timing and location of final ice sheet decay still elusive.
Using examples from northern and central Scandinavia, we show that ice-dammed lakes are an intricate part of the deglacial dynamics and show how mapping and dating them offer a solution to these problems. Even with a frozen ice-bed interface, surface melting and meltwater drainage creates landforms unequivocally associated with ice sheet decay: drainage channels, dammed lake shorelines, and deltas. Meltwater drainage routes and ice-dammed lakes are therefore powerful tools for reconstructing a disintegrating ice sheet; a ponded lake reveals the location of its requisite ice-dam, and drainage pathways reveal ice-free conditions. A dated sequence of ice-dammed lake sediments can therefore constrain both ice and lake coverage at that time for a much larger area than the dated site itself. Furthermore, the extent of different ice-dammed lake stages and their requisite ice-damming positions enables the pattern of ice margin change to be traced, and the relative age of ice-marginal positions determined using cross-cutting relations. The shorelines’ present-day tilts are also used to inform patterns and magnitudes of postglacial isostatic uplift, information otherwise lacking from the continental interior but of particular importance for modelling former ice sheet volumes and understanding the crustal response to ice sheet loading. Reconstructing the extents and timing of ice-dammed lakes and the study of related landforms and deposits can therefore greatly improve our understanding of the final decay of the Scandinavian Ice Sheet and provide potential analogues for the predicted future behaviours of modern ice sheets.
How to cite: Regnéll, C., Blomdin, R., Goodfellow, B. W., Greenwood, S. L., Gyllencreutz, R., Mangerud, J., Mikko, H., Peterson Becher, G., Regnéll, J., Svendsen, J. I., and Öhrling, C.: Ice-dammed lakes of Scandinavia - a key to the pattern and chronology of the final decay of the Scandinavian Ice Sheet, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3827, https://doi.org/10.5194/egusphere-egu21-3827, 2021.
EGU21-4573 | vPICO presentations | GM7.7
Late Pleistocene ice field on Jakupica Mt. (North Macedonia): extent and timing glaciationZsófia Ruszkiczay-Rüdiger, Zoltán Kern, Marjan Temovski, Balázs Madarász, Ivica Milevski, Johannes Lachner, and Peter Steier
Since the 19th century, geomorphological studies in the currently mainly unglaciated central Balkan Peninsula described extended glacial landforms and repeated glaciations. With the growing number of numerical ages an ambiguous picture has formed concerning the timing of the most extended glaciation and also on the glacier response to the cooling phases (e.g. Younger Dryas) during the last deglaciation of these mountain ranges.
This study provides 10Be cosmic ray exposure ages of a succession of glacial landforms in the Jakupica Mt. (North Macedonia), aiming to improve the understanding of Late Pleistocene glacier development in the area [1].
In the Jakupica Mt. (~41.7° N, ~21.4 E; Solunska Glava, 2540 m asl) a large plateau glacier was reconstructed (max. area ~45 km2, max thickness: ~300 m), where three main ice accumulation areas could be delineated [2]. The study area comprises six northeastward facing, formerly glaciated valleys. Two of these valleys emerge from the plateau, one stands separate, and the remaining three are topographically separated by a relatively flat NNW-SSE oriented ridge. During the most extensive glacial stages, these three valleys were fed by ice overflowing above this ridge from the plateau. The lowest mapped moraines are descending down to 1550-1700 m asl suggesting the former existence of glacier tongues of ~3 km length. The large plateau ice and the complicated system of confluences makes glacier reconstructions and equilibrium line altitude (ELA) calculations challenging. Thus, the ELAs were preliminary estimated based on the maximum elevation of the lowermost lateral moraines, leading to ELA values of 1800±50 m a.s.l. for the most extended phase.
The maximum ice extent outlined by the lowest mapped moraines descending down to 1550-1500 m asl. occurred around ~24-19 ka (n=5), in agreement with the timing of the Last Glacial Maximum. During the Lateglacial, the exposure ages are getting younger by the glacier recession up to the moraines at ~1820 m asl (~19-14 ka, n=15). However, the highest sampled landforms (~2200 m asl) provided ages with a large scatter between ~25 and ~5 ka (n=6). This large scatter and the observed bias towards old ages are most probably the result of inherited cosmogenic nuclide concentrations within the rock. Consequently, 10Be exposure ages alone are apparently not suitable to determine the age of final deglaciation of this mountain. Similar conditions have been observed in the Retezat Mts (Southern Carpathians, Romania) [3].
This research was supported by the NKFIH FK124807 and GINOP-2.3.2-15-2016-00009 projects and by the Radiate Transnational Access 19001688-ST.
[1] Ruszkiczay-Rüdiger et al., 2020. Last deglaciation in the central Balkan Peninsula: Geochronological evidence from Jablanica Mt. (North Macedonia). Geomorphology 351: 106985
[2] Temovski et al., 2019. Glacial geomorphology of the northeastern part of the Jakupica Mountain, Macedonia, Central Balkan Peninsula. GRA 21, EGU2019-7822
[3] Ruszkiczay-Rüdiger et al., 2018. Glacier reconstruction, deglaciation chronology and paleo-environment reconstruction, Retezat Mountains, Southern Carpathians, Romania. Geologica Balcanica; Abstracts of the XXI. CBGA Congress, Salzburg, 10-13 September; p. 240-241.
How to cite: Ruszkiczay-Rüdiger, Z., Kern, Z., Temovski, M., Madarász, B., Milevski, I., Lachner, J., and Steier, P.: Late Pleistocene ice field on Jakupica Mt. (North Macedonia): extent and timing glaciation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4573, https://doi.org/10.5194/egusphere-egu21-4573, 2021.
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Since the 19th century, geomorphological studies in the currently mainly unglaciated central Balkan Peninsula described extended glacial landforms and repeated glaciations. With the growing number of numerical ages an ambiguous picture has formed concerning the timing of the most extended glaciation and also on the glacier response to the cooling phases (e.g. Younger Dryas) during the last deglaciation of these mountain ranges.
This study provides 10Be cosmic ray exposure ages of a succession of glacial landforms in the Jakupica Mt. (North Macedonia), aiming to improve the understanding of Late Pleistocene glacier development in the area [1].
In the Jakupica Mt. (~41.7° N, ~21.4 E; Solunska Glava, 2540 m asl) a large plateau glacier was reconstructed (max. area ~45 km2, max thickness: ~300 m), where three main ice accumulation areas could be delineated [2]. The study area comprises six northeastward facing, formerly glaciated valleys. Two of these valleys emerge from the plateau, one stands separate, and the remaining three are topographically separated by a relatively flat NNW-SSE oriented ridge. During the most extensive glacial stages, these three valleys were fed by ice overflowing above this ridge from the plateau. The lowest mapped moraines are descending down to 1550-1700 m asl suggesting the former existence of glacier tongues of ~3 km length. The large plateau ice and the complicated system of confluences makes glacier reconstructions and equilibrium line altitude (ELA) calculations challenging. Thus, the ELAs were preliminary estimated based on the maximum elevation of the lowermost lateral moraines, leading to ELA values of 1800±50 m a.s.l. for the most extended phase.
The maximum ice extent outlined by the lowest mapped moraines descending down to 1550-1500 m asl. occurred around ~24-19 ka (n=5), in agreement with the timing of the Last Glacial Maximum. During the Lateglacial, the exposure ages are getting younger by the glacier recession up to the moraines at ~1820 m asl (~19-14 ka, n=15). However, the highest sampled landforms (~2200 m asl) provided ages with a large scatter between ~25 and ~5 ka (n=6). This large scatter and the observed bias towards old ages are most probably the result of inherited cosmogenic nuclide concentrations within the rock. Consequently, 10Be exposure ages alone are apparently not suitable to determine the age of final deglaciation of this mountain. Similar conditions have been observed in the Retezat Mts (Southern Carpathians, Romania) [3].
This research was supported by the NKFIH FK124807 and GINOP-2.3.2-15-2016-00009 projects and by the Radiate Transnational Access 19001688-ST.
[1] Ruszkiczay-Rüdiger et al., 2020. Last deglaciation in the central Balkan Peninsula: Geochronological evidence from Jablanica Mt. (North Macedonia). Geomorphology 351: 106985
[2] Temovski et al., 2019. Glacial geomorphology of the northeastern part of the Jakupica Mountain, Macedonia, Central Balkan Peninsula. GRA 21, EGU2019-7822
[3] Ruszkiczay-Rüdiger et al., 2018. Glacier reconstruction, deglaciation chronology and paleo-environment reconstruction, Retezat Mountains, Southern Carpathians, Romania. Geologica Balcanica; Abstracts of the XXI. CBGA Congress, Salzburg, 10-13 September; p. 240-241.
How to cite: Ruszkiczay-Rüdiger, Z., Kern, Z., Temovski, M., Madarász, B., Milevski, I., Lachner, J., and Steier, P.: Late Pleistocene ice field on Jakupica Mt. (North Macedonia): extent and timing glaciation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4573, https://doi.org/10.5194/egusphere-egu21-4573, 2021.
EGU21-5523 | vPICO presentations | GM7.7
Reconstructing LGM paleoglaciers and their ELAs along the southern fringe of the Eastern European AlpsLukas Rettig, Francesco Ferrarese, Giovanni Monegato, Paolo Mozzi, and Matteo Spagnolo
The reconstruction of paleoglaciers and specifically the calculation of their equilibrium line altitude (ELA) is an important source of quantitative paleoclimatic information in mountainous regions. During the Last Glacial Maximum (LGM), the prealpine massifs in the south-eastern part of the Alpine chain (Venetian Prealps, Carnic Prealps and Julian Prealps) hosted several small valley glaciers and local ice caps that were isolated from the larger ice-streams occupying the major valleys. Because of their small size and independent dynamics these glaciers can be considered as excellent indicators of local climatic conditions. Although this potential has long been recognised and the sediments and landforms related to these glaciations have been mapped in a few areas, a regional perspective on this type of glaciation is still lacking. This is primarily due to the wide range of methods of ELA reconstructions that has been applied historically, which makes a solid comparison between different localities difficult.
Here, we present a detailed re-evaluation of local LGM glaciation in the south-eastern Alps based on a large-scale survey of remote sensing data and targeted field work at selected localities. Recently developed GIS tools were applied for the reconstruction of paleoglacier geometries and ELAs (Pellitero et al. 2015, 2016). The obtained values are used both to discuss regional climatic patterns during the LGM and site-specific topographic factors. A specific focus is set on the Monte Cavallo group, where glacial sediments from the LGM are covering a thick sequence of interstadial lacustrine deposits. A set of new radiocarbon dates from this succession provides a first chronological control on the onset of glacier expansion in this part of the Alpine chain.
References:
Pellitero, R. et al. 2015. A GIS tool for automatic calculation of glacier equilibrium-line altitudes. Computers & Geosciences 82: 55-62.
Pellitero, R. et al. 2016. GlaRe, a GIS tool to reconstruct the 3D surface of palaeoglaciers. Computers & Geosciences 94: 77-85.
How to cite: Rettig, L., Ferrarese, F., Monegato, G., Mozzi, P., and Spagnolo, M.: Reconstructing LGM paleoglaciers and their ELAs along the southern fringe of the Eastern European Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5523, https://doi.org/10.5194/egusphere-egu21-5523, 2021.
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The reconstruction of paleoglaciers and specifically the calculation of their equilibrium line altitude (ELA) is an important source of quantitative paleoclimatic information in mountainous regions. During the Last Glacial Maximum (LGM), the prealpine massifs in the south-eastern part of the Alpine chain (Venetian Prealps, Carnic Prealps and Julian Prealps) hosted several small valley glaciers and local ice caps that were isolated from the larger ice-streams occupying the major valleys. Because of their small size and independent dynamics these glaciers can be considered as excellent indicators of local climatic conditions. Although this potential has long been recognised and the sediments and landforms related to these glaciations have been mapped in a few areas, a regional perspective on this type of glaciation is still lacking. This is primarily due to the wide range of methods of ELA reconstructions that has been applied historically, which makes a solid comparison between different localities difficult.
Here, we present a detailed re-evaluation of local LGM glaciation in the south-eastern Alps based on a large-scale survey of remote sensing data and targeted field work at selected localities. Recently developed GIS tools were applied for the reconstruction of paleoglacier geometries and ELAs (Pellitero et al. 2015, 2016). The obtained values are used both to discuss regional climatic patterns during the LGM and site-specific topographic factors. A specific focus is set on the Monte Cavallo group, where glacial sediments from the LGM are covering a thick sequence of interstadial lacustrine deposits. A set of new radiocarbon dates from this succession provides a first chronological control on the onset of glacier expansion in this part of the Alpine chain.
References:
Pellitero, R. et al. 2015. A GIS tool for automatic calculation of glacier equilibrium-line altitudes. Computers & Geosciences 82: 55-62.
Pellitero, R. et al. 2016. GlaRe, a GIS tool to reconstruct the 3D surface of palaeoglaciers. Computers & Geosciences 94: 77-85.
How to cite: Rettig, L., Ferrarese, F., Monegato, G., Mozzi, P., and Spagnolo, M.: Reconstructing LGM paleoglaciers and their ELAs along the southern fringe of the Eastern European Alps, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5523, https://doi.org/10.5194/egusphere-egu21-5523, 2021.
EGU21-7086 | vPICO presentations | GM7.7
Evolution of recently deglaciated high mountain landforms in the Eastern AnatoliaRoberto Sergio Azzoni, Irene Bollati, Manuela Pelfini, Mehmet Akif Sarıkaya, and Andrea Zerboni
High mountain environments and especially proglacial systems, which are areas defined by subtracting modern glacier outlines from Little Ice Age (LIA) limits, are among the most dynamic geomorphic contexts on Earth. They are extremely sensitive to ongoing climate change and its consequences are especially intense – yet relatively poorly investigated – at middle-low latitudes, as in the case of the circum-Mediterranean mountainous contexts. This area (excluding the Alps) encompasses recently deglaciated ground from the borders of the Mediterranean Sea and comprises more than hundred ice bodies dramatically receding since their LIA extension. Most of these glaciers are completely disappeared leaving extensive proglacial areas, which differs from those described in the Alps for the timing and types of ongoing processes. Here, we present and discuss the unique characteristics of such dynamic proglacial contexts, focusing on recently deglaciated high mountain areas of Southeast Turkey that are affected by fast geomorphological evolution tuned by their specific climatic and geological settings. We compare two areas differing for climatic, structural, and lithological settings: i) the Mount Ararat/Ağrı Dağı (5137 m a.s.l.), a stratovolcano, and ii) the Cilo mountain range (up to 4116 m a.s.l.), characterized by a limestone bedrock. Since the LIA, the two areas underwent different trajectories of evolution and different rates of geomorphic processes. High-resolution satellite data from Pleiades and SPOT 6 platforms permit to investigate the overprint of specific local factors (volcanism, tectonic, and topography) on climate-driven surface evolution explains the specific evolution of each proglacial area.
How to cite: Azzoni, R. S., Bollati, I., Pelfini, M., Sarıkaya, M. A., and Zerboni, A.: Evolution of recently deglaciated high mountain landforms in the Eastern Anatolia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7086, https://doi.org/10.5194/egusphere-egu21-7086, 2021.
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High mountain environments and especially proglacial systems, which are areas defined by subtracting modern glacier outlines from Little Ice Age (LIA) limits, are among the most dynamic geomorphic contexts on Earth. They are extremely sensitive to ongoing climate change and its consequences are especially intense – yet relatively poorly investigated – at middle-low latitudes, as in the case of the circum-Mediterranean mountainous contexts. This area (excluding the Alps) encompasses recently deglaciated ground from the borders of the Mediterranean Sea and comprises more than hundred ice bodies dramatically receding since their LIA extension. Most of these glaciers are completely disappeared leaving extensive proglacial areas, which differs from those described in the Alps for the timing and types of ongoing processes. Here, we present and discuss the unique characteristics of such dynamic proglacial contexts, focusing on recently deglaciated high mountain areas of Southeast Turkey that are affected by fast geomorphological evolution tuned by their specific climatic and geological settings. We compare two areas differing for climatic, structural, and lithological settings: i) the Mount Ararat/Ağrı Dağı (5137 m a.s.l.), a stratovolcano, and ii) the Cilo mountain range (up to 4116 m a.s.l.), characterized by a limestone bedrock. Since the LIA, the two areas underwent different trajectories of evolution and different rates of geomorphic processes. High-resolution satellite data from Pleiades and SPOT 6 platforms permit to investigate the overprint of specific local factors (volcanism, tectonic, and topography) on climate-driven surface evolution explains the specific evolution of each proglacial area.
How to cite: Azzoni, R. S., Bollati, I., Pelfini, M., Sarıkaya, M. A., and Zerboni, A.: Evolution of recently deglaciated high mountain landforms in the Eastern Anatolia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7086, https://doi.org/10.5194/egusphere-egu21-7086, 2021.
EGU21-7104 | vPICO presentations | GM7.7
The Gröbminger Mitterberg (Austria): A time machine to the pre-LGM?Gerit E.U. Griesmeier, Jürgen M. Reitner, and Daniel P. Le Heron
The Last Glacial Maximum (LGM) is well understood in many parts of the European Alps, but open questions remain concerning glacial phases prior to the LGM as the record is fragmentary. The Gröbminger Mitterberg (GM), located among the Enns Valley in Styria (Austria) is one such location where pre-LGM glacial and paraglacial processes can be studied. The GM emerges roughly 200 m from the Enns Valley floor and is situated between unmetamorphosed Mesozoic carbonates in the north and crystalline basement units in the south. Strata occur below a cover of up to more than 10 m thick basal till attributed to the LGM. The sedimentary record rests on the phyllites and greenschists that crop out at the steep southern flank of the GM. The sediment consists of an assortment of pebble-sand deposits with individual sand lenses, sand bodies with climbing ripples and undulose bedding, and fine-sand/silt laminated strata. In grain-supported intervals, cracked pebbles occur, which are interpreted to record subglacial loading. Cross-bedding orientations, together with the limited amount of unmetamorphosed carbonate pebbles in the sequence, imply that sediment was sourced from the GM and deposited at its margins, rather than from surrounding mountains towards the centre of the Enns Valley. Three depositional regimes have been recognised: deltaic sediment (both distal sands with ripples and proximal, cross-bedded gravel), lake bottom sediment (laminated fine-sand and silt) and fluvial deposits (channels with basal lag deposits and local cross bedding). The delta facies testify to the presence of lacustrine conditions. By analogy to the Unterangerberg in the Inn Valley (Tyrol, Austria; Starnberger et al. 2013), the following sequence of events is proposed. Before the LGM, sediment derived from the wider catchment area accumulated in the Enns Valley in lakes and rivers. Aggradation within the whole Enns valley resulted in deposition on the present day GM. During the LGM, the large Enns Glacier eroded much of the sediment record, especially around the GM. Deposits on top of the GM were then concealed by > 10 m thick diamicts and thereby preserved. Future age dating of the sediments will provide a better-constrained chronology to the sequence of events proposed above.
How to cite: Griesmeier, G. E. U., Reitner, J. M., and Le Heron, D. P.: The Gröbminger Mitterberg (Austria): A time machine to the pre-LGM?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7104, https://doi.org/10.5194/egusphere-egu21-7104, 2021.
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The Last Glacial Maximum (LGM) is well understood in many parts of the European Alps, but open questions remain concerning glacial phases prior to the LGM as the record is fragmentary. The Gröbminger Mitterberg (GM), located among the Enns Valley in Styria (Austria) is one such location where pre-LGM glacial and paraglacial processes can be studied. The GM emerges roughly 200 m from the Enns Valley floor and is situated between unmetamorphosed Mesozoic carbonates in the north and crystalline basement units in the south. Strata occur below a cover of up to more than 10 m thick basal till attributed to the LGM. The sedimentary record rests on the phyllites and greenschists that crop out at the steep southern flank of the GM. The sediment consists of an assortment of pebble-sand deposits with individual sand lenses, sand bodies with climbing ripples and undulose bedding, and fine-sand/silt laminated strata. In grain-supported intervals, cracked pebbles occur, which are interpreted to record subglacial loading. Cross-bedding orientations, together with the limited amount of unmetamorphosed carbonate pebbles in the sequence, imply that sediment was sourced from the GM and deposited at its margins, rather than from surrounding mountains towards the centre of the Enns Valley. Three depositional regimes have been recognised: deltaic sediment (both distal sands with ripples and proximal, cross-bedded gravel), lake bottom sediment (laminated fine-sand and silt) and fluvial deposits (channels with basal lag deposits and local cross bedding). The delta facies testify to the presence of lacustrine conditions. By analogy to the Unterangerberg in the Inn Valley (Tyrol, Austria; Starnberger et al. 2013), the following sequence of events is proposed. Before the LGM, sediment derived from the wider catchment area accumulated in the Enns Valley in lakes and rivers. Aggradation within the whole Enns valley resulted in deposition on the present day GM. During the LGM, the large Enns Glacier eroded much of the sediment record, especially around the GM. Deposits on top of the GM were then concealed by > 10 m thick diamicts and thereby preserved. Future age dating of the sediments will provide a better-constrained chronology to the sequence of events proposed above.
How to cite: Griesmeier, G. E. U., Reitner, J. M., and Le Heron, D. P.: The Gröbminger Mitterberg (Austria): A time machine to the pre-LGM?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7104, https://doi.org/10.5194/egusphere-egu21-7104, 2021.
EGU21-7706 | vPICO presentations | GM7.7
The extent, timing and palaeoclimatic significance of Late-glacial and Holocene snowpatches and glaciers in the Marrakech High Atlas, MoroccoBenjamin Bell, Philip Hughes, William Fletcher, Roger Braithwaite, Henk Cornelissen, David Fink, and Ali Rhoujjati
Pleistocene glaciers were extensive in the Marrakech High Atlas, Morocco. Today, semi-permanent snowpatches survive in topoclimatic settings and there is evidence of niche glaciers as recently as the Little Ice Age and early 20th Century. However, little is known about the state of permanent snow and niche glaciers through the Holocene. One hypothesis is that Little Ice Age glaciers were the largest snow and ice masses since the end of the Late-glacial (Younger Dryas 12.9-11.7 ka). Another possibility is that snow and ice expanded to similar or greater extents at other points in the Holocene.
To test these hypotheses, moraine boulders have been sampled on moraine successions in the highest parts of the High Atlas, including moraine successions in front of the névé permanent below the north-facing cliffs of Tazaghart (3890 m a.s.l.), a semi-permanent snowpatch that survives many summers today. This site is bounded by prominent moraine ridges with no soil development and no lichens on surface boulders. Several other high-level sites have been targeted and over 40 samples are currently being processed for 10Be and 36Cl exposure dating. Establishing the relative difference in extent and altitude of Late-glacial and the most recent glaciers in the High Atlas is important for understanding landscape and climate evolution in high mountain areas in the subtropics (31ºN).
The dated geomorphological records for late-lying snow and glaciers will be compared to high-resolution 14C dated continuous parasequences from sediment cores from marshes at the Yagour Plateau and Oukaïmeden, both high-level sites in the High Atlas (~2700 m a.s.l.). The proximity of these sites (5-30 km, respectively) from the snowpatch/glacier sites will provide an important independent record of environmental change, spanning the Late-glacial and Holocene. This geomorphological record of former glaciers and snowpatches (moraines and pronival ramparts) is inherently fragmentary in time and the continuous core records from these alpine marshes will provide crucial insights into changing moisture conditions over time, which at these altitudes are closely related to the extent and volume of snowpack.
The climates associated with perennial snow cover and niche glaciers, and the associated annual snowpack melt, will be quantified using degree-day modelling. This allows melt rates to be predicted and this can be compared against observed modern climate in the High Atlas region. This involves interrogation of existing meteorological datasets from across the High Atlas and the development of algorithms for interpolation and extrapolation to ungauged higher altitudes.
Changes in the nature of the cryosphere through time in the High Atlas Mountains is crucial for understanding human activity and socioeconomic development in the wider region. Today, snowmelt from the High Atlas represents the most important ground water recharge used for a wide variety of purposes. Understanding changes in snow conditions, and as a consequence the behaviour of niche glaciers, in the High Atlas through the Holocene has important implications not only for water supply for humans but also for biological refugia and the evolution of cold-adapted flora and fauna.
How to cite: Bell, B., Hughes, P., Fletcher, W., Braithwaite, R., Cornelissen, H., Fink, D., and Rhoujjati, A.: The extent, timing and palaeoclimatic significance of Late-glacial and Holocene snowpatches and glaciers in the Marrakech High Atlas, Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7706, https://doi.org/10.5194/egusphere-egu21-7706, 2021.
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Pleistocene glaciers were extensive in the Marrakech High Atlas, Morocco. Today, semi-permanent snowpatches survive in topoclimatic settings and there is evidence of niche glaciers as recently as the Little Ice Age and early 20th Century. However, little is known about the state of permanent snow and niche glaciers through the Holocene. One hypothesis is that Little Ice Age glaciers were the largest snow and ice masses since the end of the Late-glacial (Younger Dryas 12.9-11.7 ka). Another possibility is that snow and ice expanded to similar or greater extents at other points in the Holocene.
To test these hypotheses, moraine boulders have been sampled on moraine successions in the highest parts of the High Atlas, including moraine successions in front of the névé permanent below the north-facing cliffs of Tazaghart (3890 m a.s.l.), a semi-permanent snowpatch that survives many summers today. This site is bounded by prominent moraine ridges with no soil development and no lichens on surface boulders. Several other high-level sites have been targeted and over 40 samples are currently being processed for 10Be and 36Cl exposure dating. Establishing the relative difference in extent and altitude of Late-glacial and the most recent glaciers in the High Atlas is important for understanding landscape and climate evolution in high mountain areas in the subtropics (31ºN).
The dated geomorphological records for late-lying snow and glaciers will be compared to high-resolution 14C dated continuous parasequences from sediment cores from marshes at the Yagour Plateau and Oukaïmeden, both high-level sites in the High Atlas (~2700 m a.s.l.). The proximity of these sites (5-30 km, respectively) from the snowpatch/glacier sites will provide an important independent record of environmental change, spanning the Late-glacial and Holocene. This geomorphological record of former glaciers and snowpatches (moraines and pronival ramparts) is inherently fragmentary in time and the continuous core records from these alpine marshes will provide crucial insights into changing moisture conditions over time, which at these altitudes are closely related to the extent and volume of snowpack.
The climates associated with perennial snow cover and niche glaciers, and the associated annual snowpack melt, will be quantified using degree-day modelling. This allows melt rates to be predicted and this can be compared against observed modern climate in the High Atlas region. This involves interrogation of existing meteorological datasets from across the High Atlas and the development of algorithms for interpolation and extrapolation to ungauged higher altitudes.
Changes in the nature of the cryosphere through time in the High Atlas Mountains is crucial for understanding human activity and socioeconomic development in the wider region. Today, snowmelt from the High Atlas represents the most important ground water recharge used for a wide variety of purposes. Understanding changes in snow conditions, and as a consequence the behaviour of niche glaciers, in the High Atlas through the Holocene has important implications not only for water supply for humans but also for biological refugia and the evolution of cold-adapted flora and fauna.
How to cite: Bell, B., Hughes, P., Fletcher, W., Braithwaite, R., Cornelissen, H., Fink, D., and Rhoujjati, A.: The extent, timing and palaeoclimatic significance of Late-glacial and Holocene snowpatches and glaciers in the Marrakech High Atlas, Morocco, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7706, https://doi.org/10.5194/egusphere-egu21-7706, 2021.
EGU21-7861 | vPICO presentations | GM7.7
The deglacial dynamics of the Laurentide and Cordilleran ice sheets in the Mackenzie Mountains, Northwest Territories, CanadaBenjamin J Stoker, Martin Margold, Duane G. Froese, and John C. Gosse
The northwestern sector of the Laurentide Ice Sheet coalesced with the Cordilleran Ice Sheet over the southern Mackenzie Mountains, and with local montane glaciers along the eastern slopes of the Mackenzie Mountains. Numerical modelling studies have identified rapid ice sheet thinning in this region as a major contributor to Meltwater Pulse 1A. Despite advances in remote sensing and numerical dating methods, the configuration and chronology of the northwestern sector of the Laurentide Ice Sheet have not been reconstructed in detail. The last available studies date back to the 1990s, when field surveys and mapping from aerial imagery were used to reconstruct the glacial history in the Mackenzie Mountains. Cross-cutting relations between glacial landforms and a series of 36Cl cosmogenic nuclide dates were used to propose a deglacial model involving a significant readvance of the Laurentide Ice Sheet in the region. However, the chronological evidence supporting the readvance is uncertain because the individual ages are few and poorly clustered. Here we present an updated map of the glacial limits during the local Last Glacial Maximum and the recessional record in the Mackenzie Mountains, based on glacial geomorphological mapping from the ArcticDEM. We provide sixteen new 10Be dates from four sites that were previously glaciated by the Laurentide Ice Sheet to constrain the deglacial sequence across the region. These dates indicate ice sheet detachment from the eastern Mackenzie Mountains at ~16 ka as summits in the mountain front became ice-free. The Mackenzie Valley at ~ 65 °N became ice-free at ~ 14 – 13 ka, towards the end of the Bølling-Allerød warm period. Combining these dates with existing 10Be dates, these chronological constraints on the deglaciation of the Laurentide Ice Sheet allow us to reinterpret landform relations in the Mackenzie Mountains in order to reconstruct the ice sheet retreat. Our reconstruction provides updated constraints on the LGM extent, and the timing and pattern of deglaciation in the Mackenzie Mountains. This new understanding is useful to future efforts to quantify past sea-level contributions from the western Laurentide Ice Sheet.
How to cite: Stoker, B. J., Margold, M., Froese, D. G., and Gosse, J. C.: The deglacial dynamics of the Laurentide and Cordilleran ice sheets in the Mackenzie Mountains, Northwest Territories, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7861, https://doi.org/10.5194/egusphere-egu21-7861, 2021.
The northwestern sector of the Laurentide Ice Sheet coalesced with the Cordilleran Ice Sheet over the southern Mackenzie Mountains, and with local montane glaciers along the eastern slopes of the Mackenzie Mountains. Numerical modelling studies have identified rapid ice sheet thinning in this region as a major contributor to Meltwater Pulse 1A. Despite advances in remote sensing and numerical dating methods, the configuration and chronology of the northwestern sector of the Laurentide Ice Sheet have not been reconstructed in detail. The last available studies date back to the 1990s, when field surveys and mapping from aerial imagery were used to reconstruct the glacial history in the Mackenzie Mountains. Cross-cutting relations between glacial landforms and a series of 36Cl cosmogenic nuclide dates were used to propose a deglacial model involving a significant readvance of the Laurentide Ice Sheet in the region. However, the chronological evidence supporting the readvance is uncertain because the individual ages are few and poorly clustered. Here we present an updated map of the glacial limits during the local Last Glacial Maximum and the recessional record in the Mackenzie Mountains, based on glacial geomorphological mapping from the ArcticDEM. We provide sixteen new 10Be dates from four sites that were previously glaciated by the Laurentide Ice Sheet to constrain the deglacial sequence across the region. These dates indicate ice sheet detachment from the eastern Mackenzie Mountains at ~16 ka as summits in the mountain front became ice-free. The Mackenzie Valley at ~ 65 °N became ice-free at ~ 14 – 13 ka, towards the end of the Bølling-Allerød warm period. Combining these dates with existing 10Be dates, these chronological constraints on the deglaciation of the Laurentide Ice Sheet allow us to reinterpret landform relations in the Mackenzie Mountains in order to reconstruct the ice sheet retreat. Our reconstruction provides updated constraints on the LGM extent, and the timing and pattern of deglaciation in the Mackenzie Mountains. This new understanding is useful to future efforts to quantify past sea-level contributions from the western Laurentide Ice Sheet.
How to cite: Stoker, B. J., Margold, M., Froese, D. G., and Gosse, J. C.: The deglacial dynamics of the Laurentide and Cordilleran ice sheets in the Mackenzie Mountains, Northwest Territories, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7861, https://doi.org/10.5194/egusphere-egu21-7861, 2021.
EGU21-9752 | vPICO presentations | GM7.7
Assessing the performance of geophysical survey techniques for characterising the subsurface around glacier marginsHannah Watts, Adam Booth, Benedict Reinardy, Siobhan Killingbeck, Peter Jansson, Roger Clark, and Atle Nesje
Glacier forelands contain valuable information on past glacier dynamics and associated climatic conditions, particularly at small mountain glaciers where responses to climate change are rapid. To maximize the potential of glacial landforms as palaeoclimate indicators, a thorough understanding of the controls on landform genesis and subsequent evolution is required. Traditionally, such landforms have been studied using glacial geological techniques such as sedimentary logging. While these provide valuable in situ information they have numerous limitations, namely poor availability and spatial extent of exposures. Near-surface geophysics provides an efficient and non-invasive means of studying subsurface conditions in numerous sedimentary settings, offering spatially extensive information on substrate material properties and architecture. However, the logistically challenging terrain, remote location and complex structure of proglacial environments has limited the development of geophysical techniques for studying the internal architecture of glacial landforms.
Here, we explore the application of three geophysical methods to investigate proglacial substrates: ground penetrating radar (GPR), seismic refraction and multi-channel analysis of surface waves (MASW). Three sites with contrasting sediment properties were surveyed at the foreland of Midtdalsbreen glacier in southern Norway; (a) a 100 m2 area of glaciotectonised sandy sediments, (b) a ~2 m high lateral moraine ridge containing stratified silts, sands, and gravel and (c) a terminal moraine ridge with a peak crest height of ~5 m and an open blockwork of cobbles and boulders at its surface. At all sites, we deployed 25 MHz and 100 MHz GPR antennas and undertook seismic surveys with 50−75 m long geophone spreads and a sledge-hammer source to sample to target depths of around 10−15 m. Through comparing the results from sites (a) to (c), we assess the capabilities and limitations of each of the aforementioned techniques for proglacial substrate imaging and characterisation, we analyse how their performances vary across these settings and outline factors that contribute to a successful geophysical investigation.
The ease of analysis and achievable investigation depths of the geophysical data and the applicability of seismic interpretation methods varied considerably depending on the surface terrain and structural complexity of the site. Our results show how the combination of GPR and seismic data can assist with the internal characterisation of glacial moraines when a relatively simple subsurface structure is present. However, basic seismic inversions likely lack the sophistication to resolve seismic structure in all but the simplest of layered models. We offer suggestions on how to optimise field time in more complex settings, where more sophisticated seismic inversion algorithms (e.g. tomography) or 3-D GPR surveys could be better-suited.
Our experience should help advance the use of geophysics in proglacial studies. It should serve as a guide for future survey planning, and help avoid typical pitfalls such that field time can be optimised. It is hoped that geophysical survey methods will play an increasing role in the understanding of proglacial sedimentary landforms and their associated palaeoenvironments.
How to cite: Watts, H., Booth, A., Reinardy, B., Killingbeck, S., Jansson, P., Clark, R., and Nesje, A.: Assessing the performance of geophysical survey techniques for characterising the subsurface around glacier margins , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9752, https://doi.org/10.5194/egusphere-egu21-9752, 2021.
Glacier forelands contain valuable information on past glacier dynamics and associated climatic conditions, particularly at small mountain glaciers where responses to climate change are rapid. To maximize the potential of glacial landforms as palaeoclimate indicators, a thorough understanding of the controls on landform genesis and subsequent evolution is required. Traditionally, such landforms have been studied using glacial geological techniques such as sedimentary logging. While these provide valuable in situ information they have numerous limitations, namely poor availability and spatial extent of exposures. Near-surface geophysics provides an efficient and non-invasive means of studying subsurface conditions in numerous sedimentary settings, offering spatially extensive information on substrate material properties and architecture. However, the logistically challenging terrain, remote location and complex structure of proglacial environments has limited the development of geophysical techniques for studying the internal architecture of glacial landforms.
Here, we explore the application of three geophysical methods to investigate proglacial substrates: ground penetrating radar (GPR), seismic refraction and multi-channel analysis of surface waves (MASW). Three sites with contrasting sediment properties were surveyed at the foreland of Midtdalsbreen glacier in southern Norway; (a) a 100 m2 area of glaciotectonised sandy sediments, (b) a ~2 m high lateral moraine ridge containing stratified silts, sands, and gravel and (c) a terminal moraine ridge with a peak crest height of ~5 m and an open blockwork of cobbles and boulders at its surface. At all sites, we deployed 25 MHz and 100 MHz GPR antennas and undertook seismic surveys with 50−75 m long geophone spreads and a sledge-hammer source to sample to target depths of around 10−15 m. Through comparing the results from sites (a) to (c), we assess the capabilities and limitations of each of the aforementioned techniques for proglacial substrate imaging and characterisation, we analyse how their performances vary across these settings and outline factors that contribute to a successful geophysical investigation.
The ease of analysis and achievable investigation depths of the geophysical data and the applicability of seismic interpretation methods varied considerably depending on the surface terrain and structural complexity of the site. Our results show how the combination of GPR and seismic data can assist with the internal characterisation of glacial moraines when a relatively simple subsurface structure is present. However, basic seismic inversions likely lack the sophistication to resolve seismic structure in all but the simplest of layered models. We offer suggestions on how to optimise field time in more complex settings, where more sophisticated seismic inversion algorithms (e.g. tomography) or 3-D GPR surveys could be better-suited.
Our experience should help advance the use of geophysics in proglacial studies. It should serve as a guide for future survey planning, and help avoid typical pitfalls such that field time can be optimised. It is hoped that geophysical survey methods will play an increasing role in the understanding of proglacial sedimentary landforms and their associated palaeoenvironments.
How to cite: Watts, H., Booth, A., Reinardy, B., Killingbeck, S., Jansson, P., Clark, R., and Nesje, A.: Assessing the performance of geophysical survey techniques for characterising the subsurface around glacier margins , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9752, https://doi.org/10.5194/egusphere-egu21-9752, 2021.
EGU21-9883 | vPICO presentations | GM7.7
New Late Glacial and Holocene 36Cl and 10Be moraine chronologies from sub-Antarctic Kerguelen ArchipelagoJoanna Charton, Vincent Jomelli, Irene Schimmelpfennig, Deborah Verfaillie, Vincent Favier, Guillaume Delpech, Régis Braucher, Pierre-Henri Blard, Vincent Rinterknecht, Léo Chassiot, Georges Aumaître, Didier L. Bourlès, and Karim Keddadouche
The Kerguelen Archipelago (49°S, 69°E) is an excellent location for the study of multi-millennial glacier fluctuations, since it is the largest still glaciated emerged area (552 km2 in 2001) in the sub-Antarctic sector of the Indian Ocean, where many glacio-geomorphological formations such as moraines may be dated. To investigate the so-far little-known Late Glacial and the Holocene glacier fluctuations in Kerguelen, we apply cosmogenic nuclide dating of moraines in 3 glacial valleys: Val Travers valley, Ampere glacier valley and Arago glacier valley. We use in situ 36Cl dating of the basaltic moraine boulders at the first two sites, and 10Be dating of the quartz-bearing syenite boulders at the third site. The new 36Cl and 10Be exposure ages provide time constraints over the last 17,000 years. A glacial advance was highlighted during the Late Glacial at 14.4 ± 1.4 ka ago, probably linked to the Antarctic Cold Reversal event. These results are consistent with those previously obtained on the archipelago (Jomelli et al., 2017, 2018; Charton et al., 2020) and more generally those from other the sub-Antarctic regions (e.g. Sagredo et al., 2018). This suggests that all glaciers at this latitude were broadly sensitive to this specific climatic signal. No Early nor Mid Holocene advances were evidenced in Kerguelen glacier evolution during the Holocene due to missing moraines that may have formed in these specific periods. Radiocarbon-dated peat, published in the 1990s, provides evidence of less extensive glacier extents during the Early Holocene than during the Late Holocene (Frenot et al., 1997). Finally, glaciers seem to have re-advanced only during the Late Holocene, especially within the last millennium, at ⁓1 ka, ⁓620 years and ⁓390 years (Verfaillie et al., submitted). A comparison of this new dataset with the available 10Be ages from other sub-Antarctic regions allows for the identification of 3 different glacier evolution patterns during the Holocene. The glacial fluctuations experienced by Kerguelen glaciers seems particularly uncommon, and are likely due to its singular location in the Southern Indian Ocean. Finally, climatic factors that may explain the Kerguelen glacier evolution (temperature, precipitation) are discussed. To this end, we investigate the chronology of glacier advance/retreat periods with (i) the variation in atmospheric temperatures recorded in ice cores in Antarctica and (ii) the variation in precipitation (Southern Westerly Winds, Southern Annular Mode).
Charton et al., 2020 : Ant. Sci. 1-13
Frenot et al., 1997 : C.R. Acad. Sci. Paris Life Sciences 320, 567-573
Jomelli et al., 2017 : Quat. Sci. Rev. 162, 128-144
Jomelli et al., 2018 : Quat. Sci. Rev. 183, 110-123
Sagredo et al., 2018 : Quat Sci. Rev. 188, 160-166
Verfaillie et al., submitted
How to cite: Charton, J., Jomelli, V., Schimmelpfennig, I., Verfaillie, D., Favier, V., Delpech, G., Braucher, R., Blard, P.-H., Rinterknecht, V., Chassiot, L., Aumaître, G., Bourlès, D. L., and Keddadouche, K.: New Late Glacial and Holocene 36Cl and 10Be moraine chronologies from sub-Antarctic Kerguelen Archipelago, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9883, https://doi.org/10.5194/egusphere-egu21-9883, 2021.
The Kerguelen Archipelago (49°S, 69°E) is an excellent location for the study of multi-millennial glacier fluctuations, since it is the largest still glaciated emerged area (552 km2 in 2001) in the sub-Antarctic sector of the Indian Ocean, where many glacio-geomorphological formations such as moraines may be dated. To investigate the so-far little-known Late Glacial and the Holocene glacier fluctuations in Kerguelen, we apply cosmogenic nuclide dating of moraines in 3 glacial valleys: Val Travers valley, Ampere glacier valley and Arago glacier valley. We use in situ 36Cl dating of the basaltic moraine boulders at the first two sites, and 10Be dating of the quartz-bearing syenite boulders at the third site. The new 36Cl and 10Be exposure ages provide time constraints over the last 17,000 years. A glacial advance was highlighted during the Late Glacial at 14.4 ± 1.4 ka ago, probably linked to the Antarctic Cold Reversal event. These results are consistent with those previously obtained on the archipelago (Jomelli et al., 2017, 2018; Charton et al., 2020) and more generally those from other the sub-Antarctic regions (e.g. Sagredo et al., 2018). This suggests that all glaciers at this latitude were broadly sensitive to this specific climatic signal. No Early nor Mid Holocene advances were evidenced in Kerguelen glacier evolution during the Holocene due to missing moraines that may have formed in these specific periods. Radiocarbon-dated peat, published in the 1990s, provides evidence of less extensive glacier extents during the Early Holocene than during the Late Holocene (Frenot et al., 1997). Finally, glaciers seem to have re-advanced only during the Late Holocene, especially within the last millennium, at ⁓1 ka, ⁓620 years and ⁓390 years (Verfaillie et al., submitted). A comparison of this new dataset with the available 10Be ages from other sub-Antarctic regions allows for the identification of 3 different glacier evolution patterns during the Holocene. The glacial fluctuations experienced by Kerguelen glaciers seems particularly uncommon, and are likely due to its singular location in the Southern Indian Ocean. Finally, climatic factors that may explain the Kerguelen glacier evolution (temperature, precipitation) are discussed. To this end, we investigate the chronology of glacier advance/retreat periods with (i) the variation in atmospheric temperatures recorded in ice cores in Antarctica and (ii) the variation in precipitation (Southern Westerly Winds, Southern Annular Mode).
Charton et al., 2020 : Ant. Sci. 1-13
Frenot et al., 1997 : C.R. Acad. Sci. Paris Life Sciences 320, 567-573
Jomelli et al., 2017 : Quat. Sci. Rev. 162, 128-144
Jomelli et al., 2018 : Quat. Sci. Rev. 183, 110-123
Sagredo et al., 2018 : Quat Sci. Rev. 188, 160-166
Verfaillie et al., submitted
How to cite: Charton, J., Jomelli, V., Schimmelpfennig, I., Verfaillie, D., Favier, V., Delpech, G., Braucher, R., Blard, P.-H., Rinterknecht, V., Chassiot, L., Aumaître, G., Bourlès, D. L., and Keddadouche, K.: New Late Glacial and Holocene 36Cl and 10Be moraine chronologies from sub-Antarctic Kerguelen Archipelago, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9883, https://doi.org/10.5194/egusphere-egu21-9883, 2021.
EGU21-10398 | vPICO presentations | GM7.7
The timing of deglaciation from mountain summits to cirques in Wales: 10Be and 26Al exposure dates from Cadair IdrisPhilip Hughes, Neil Glasser, David Fink, Jason Dortch, Reka Fülöp, Klaus Wilcken, and Toshiyuki Fujioka
Cosmogenic 10Be and 26Al exposure ages from 20 erratic samples collected from Cadair Idris (893 m), a mountain in southern Snowdonia, Wales, provide evidence for the timing of deglaciation from summits to cirques at the end of the Late Pleistocene. The summit of the mountain is characterised by intensely modified frost-shattered surfaces that have long been identified as a representing a former nunatak. Numerous glacially-transported quartz boulders on the highest ground indicate that ice overran the summit at some point in the Pleistocene. Two quartz boulders, one with preserved striations, sampled at c. 856 m near the summit of Cadair Idris yielded consistent 10Be and 26Al paired exposure ages of 75 ka to 60 ka (using a high-latitude sea level 10Be spallation production rate of 4.20 at/g/y, scaled by the Lal/Stone scheme). A glacially polished bedrock quartzite outcrop at 735 m gave an age of 17.5 ka. Immediately below this, cirque and down-valley recessional moraine ages, covering an elevation of 480 m to 350 m ranged from 10 to 15 ka respectively.
These results confirm that Cadair Idris was overridden by the Welsh Ice Cap during marine isotope stage (MIS) 4, when ice was thicker than at the global last glacial maximum (LGM) in MIS 2. This is consistent with findings from northern Snowdonia. The highest Welsh summits, including Cadair Idris, emerged above a thinning Welsh Ice Cap (British Irish Ice Sheet) during the transition from MIS 4 to 3. The summit area above ~800 m then stood as nunataks above the LGM ice sheet surface in MIS 2. The Welsh Ice Cap then rapidly thinned over Cadair Idris at ~20-17 ka based on ages from high-level ice-moulded bedrockThis is supported by more new ages from high-level paired erratics and bedrock samples on several other mountains throughout Snowdonia, leading to a phase of alpine-style deglaciation. Valley glaciers initiated their retreat up-valley from ~17 to 14 ka after Heinrich Event 1. A later phase of glacier stabilisation or still stand formation produced classic cirque moraines near the rim of a present cirque lake basin (480 m elevation) yielding 10Be ages of 13-10 ka during the Younger Dryas.
How to cite: Hughes, P., Glasser, N., Fink, D., Dortch, J., Fülöp, R., Wilcken, K., and Fujioka, T.: The timing of deglaciation from mountain summits to cirques in Wales: 10Be and 26Al exposure dates from Cadair Idris, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10398, https://doi.org/10.5194/egusphere-egu21-10398, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
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Cosmogenic 10Be and 26Al exposure ages from 20 erratic samples collected from Cadair Idris (893 m), a mountain in southern Snowdonia, Wales, provide evidence for the timing of deglaciation from summits to cirques at the end of the Late Pleistocene. The summit of the mountain is characterised by intensely modified frost-shattered surfaces that have long been identified as a representing a former nunatak. Numerous glacially-transported quartz boulders on the highest ground indicate that ice overran the summit at some point in the Pleistocene. Two quartz boulders, one with preserved striations, sampled at c. 856 m near the summit of Cadair Idris yielded consistent 10Be and 26Al paired exposure ages of 75 ka to 60 ka (using a high-latitude sea level 10Be spallation production rate of 4.20 at/g/y, scaled by the Lal/Stone scheme). A glacially polished bedrock quartzite outcrop at 735 m gave an age of 17.5 ka. Immediately below this, cirque and down-valley recessional moraine ages, covering an elevation of 480 m to 350 m ranged from 10 to 15 ka respectively.
These results confirm that Cadair Idris was overridden by the Welsh Ice Cap during marine isotope stage (MIS) 4, when ice was thicker than at the global last glacial maximum (LGM) in MIS 2. This is consistent with findings from northern Snowdonia. The highest Welsh summits, including Cadair Idris, emerged above a thinning Welsh Ice Cap (British Irish Ice Sheet) during the transition from MIS 4 to 3. The summit area above ~800 m then stood as nunataks above the LGM ice sheet surface in MIS 2. The Welsh Ice Cap then rapidly thinned over Cadair Idris at ~20-17 ka based on ages from high-level ice-moulded bedrockThis is supported by more new ages from high-level paired erratics and bedrock samples on several other mountains throughout Snowdonia, leading to a phase of alpine-style deglaciation. Valley glaciers initiated their retreat up-valley from ~17 to 14 ka after Heinrich Event 1. A later phase of glacier stabilisation or still stand formation produced classic cirque moraines near the rim of a present cirque lake basin (480 m elevation) yielding 10Be ages of 13-10 ka during the Younger Dryas.
How to cite: Hughes, P., Glasser, N., Fink, D., Dortch, J., Fülöp, R., Wilcken, K., and Fujioka, T.: The timing of deglaciation from mountain summits to cirques in Wales: 10Be and 26Al exposure dates from Cadair Idris, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10398, https://doi.org/10.5194/egusphere-egu21-10398, 2021.
EGU21-11494 | vPICO presentations | GM7.7
The transition from the Late Glacial to the Early Holocene and its expression in moraine records of the Silvretta MassifSandra M. Braumann, Joerg M. Schaefer, Stephanie M. Neuhuber, and Markus Fiebig
Mountain glaciers and their preserved moraine records provide important insights into periods when climate conditions favored glacier advance or stabilization. Comprehensive mapping of moraines in glacier forefields elucidates the spatial distribution of former ice margins. Numerical age dating of moraines, in turn, constrains the timing of moraine formation intervals. A combination of both methods allows reconstructing the evolution of mountain glaciers across time and space and links today’s alpine geomorphology with climate of the past.
Here, we present glacier reconstructions from two adjacent valleys in the northern Silvretta Massif (Austrian Alps). Both, the Jamtal and the Laraintal, exhibit multiple prominent moraine ridges outboard the Little Ice Age (LIA) moraine and inboard presumable Late Glacial ice margins. By applying 10Be surface exposure dating to these moraines, we decipher the response of Silvretta glaciers to the transition from glacial to interglacial climatic conditions.
Pronounced double-ridge structures in lateral and terminal positions outside the LIA moraines were dated and yield landform ages of 11.3 ±0.8 kyrs (n=12) and 10.8 ±0.8 kyrs (n=9). This age pattern is consistent across both valleys and implies two significant moraine formation intervals during the earliest Holocene that overlap within uncertainties. Additional samples (n=6) were collected along presumable LIA ice margins. Four of them indeed produced LIA ages with three of them suggesting a culmination in the second half of the 18th century CE (mean age: 260 ±25 yrs). This result is in good agreement with 10Be ages from a recent study at an adjacent site, which indicate a LIA advance around 260 ±30 yrs. The remaining two ages coincide with a phase of cooler temperatures and increased precipitation in Europe from the 4th to 6th century, a climate episode, which is often associated with the fall of the Roman Empire and with the migration period in Europe.
We interpret the sets of Early Holocene moraines as evidence of brief cold lapses, which punctuated the general warming trend at the beginning of the Holocene, with the Preboreal Oscillation (PBO; c. 11,300 to 11,150 cal BP) being the most prominent one. Moraine formation intervals during the Early Holocene have been reported in the wider Alpine region and at other places in the northern hemisphere (e.g. North America, Scandinavia, Greenland). Annual mean temperatures certainly differed at each of these places, but synchronous phases of glacier advances or stabilization are recorded across the northern hemisphere during the Early Holocene. We suggest that freshwater input into the Atlantic Ocean caused phases of temporary weakening of the Atlantic Meridional Overturning Circulation (AMOC), which lead to episodes of relative cooling in the northern hemisphere. This cooling phases are preserved in the Early Holocene moraine sets that we mapped and dated in the Silvretta region.
How to cite: Braumann, S. M., Schaefer, J. M., Neuhuber, S. M., and Fiebig, M.: The transition from the Late Glacial to the Early Holocene and its expression in moraine records of the Silvretta Massif, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11494, https://doi.org/10.5194/egusphere-egu21-11494, 2021.
Mountain glaciers and their preserved moraine records provide important insights into periods when climate conditions favored glacier advance or stabilization. Comprehensive mapping of moraines in glacier forefields elucidates the spatial distribution of former ice margins. Numerical age dating of moraines, in turn, constrains the timing of moraine formation intervals. A combination of both methods allows reconstructing the evolution of mountain glaciers across time and space and links today’s alpine geomorphology with climate of the past.
Here, we present glacier reconstructions from two adjacent valleys in the northern Silvretta Massif (Austrian Alps). Both, the Jamtal and the Laraintal, exhibit multiple prominent moraine ridges outboard the Little Ice Age (LIA) moraine and inboard presumable Late Glacial ice margins. By applying 10Be surface exposure dating to these moraines, we decipher the response of Silvretta glaciers to the transition from glacial to interglacial climatic conditions.
Pronounced double-ridge structures in lateral and terminal positions outside the LIA moraines were dated and yield landform ages of 11.3 ±0.8 kyrs (n=12) and 10.8 ±0.8 kyrs (n=9). This age pattern is consistent across both valleys and implies two significant moraine formation intervals during the earliest Holocene that overlap within uncertainties. Additional samples (n=6) were collected along presumable LIA ice margins. Four of them indeed produced LIA ages with three of them suggesting a culmination in the second half of the 18th century CE (mean age: 260 ±25 yrs). This result is in good agreement with 10Be ages from a recent study at an adjacent site, which indicate a LIA advance around 260 ±30 yrs. The remaining two ages coincide with a phase of cooler temperatures and increased precipitation in Europe from the 4th to 6th century, a climate episode, which is often associated with the fall of the Roman Empire and with the migration period in Europe.
We interpret the sets of Early Holocene moraines as evidence of brief cold lapses, which punctuated the general warming trend at the beginning of the Holocene, with the Preboreal Oscillation (PBO; c. 11,300 to 11,150 cal BP) being the most prominent one. Moraine formation intervals during the Early Holocene have been reported in the wider Alpine region and at other places in the northern hemisphere (e.g. North America, Scandinavia, Greenland). Annual mean temperatures certainly differed at each of these places, but synchronous phases of glacier advances or stabilization are recorded across the northern hemisphere during the Early Holocene. We suggest that freshwater input into the Atlantic Ocean caused phases of temporary weakening of the Atlantic Meridional Overturning Circulation (AMOC), which lead to episodes of relative cooling in the northern hemisphere. This cooling phases are preserved in the Early Holocene moraine sets that we mapped and dated in the Silvretta region.
How to cite: Braumann, S. M., Schaefer, J. M., Neuhuber, S. M., and Fiebig, M.: The transition from the Late Glacial to the Early Holocene and its expression in moraine records of the Silvretta Massif, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11494, https://doi.org/10.5194/egusphere-egu21-11494, 2021.
GM8.2 – Drylands: paleoenvironmental and geomorphic perspectives and challenges
EGU21-8586 | vPICO presentations | GM8.2 | Highlight
Eurasian drylands and the conceptual model of loess landscapesFrank Lehmkuhl, Ulrich Hambach, Janina J. Nett, Philipp Schulte, Zdzislaw Jary, Tobias Sprafke, Pierre Antoine, Lara Wacha, Andrea Zerboni, Jan Hošek, and Slobodan Marković
At least 10% of the Earth surface and large areas of the Eurasian continent are covered by aeolian silt and sand deposits. The origin and distribution of these deposits is indicative for the (paleo-) environment and represent an important edaphic factor for eco-zone evolution, which in turn controls past and present land use.
Here we present a conceptual model of loess landscapes in relation to past and present drylands based on the spatial analysis of loess and loess facies' in Europe (Lehmkuhl et al., 2020). Corners of our conceptual 'loess-triangle' represent three eco-zones (nival, humid, and arid environments) peripheral to 'typical' loess formation (placed in the center). The modes of loess formation are controlled by climatic factors, namely water availability and temperature, which also constrain the prevailing vegetation: Mode 1 - Periglacial and tundra loess; Mode 2 - Temperate and subtropical loess; Mode 3 - Desert margin loess. In-between these three peripheral modes of loess facies we illustrate that ‘typical’, continuous and silt dominated loess formation takes place.
At the Chinese Loess Plateau, there is a gradual transition in grain-size from the humid regions in the south and southeast to the semi-arid and arid regions in the northwest (from Mode 2 towards typical loess and Mode 3). Reduced vegetation cover at desert margins, along dry riverbeds and lakes leads to increased aeolian deflation facilitating also mid- and long-distance transport of silt-sized particles. The resulting deposits range from silty loess to sandier loess in the direction of increasing aridity towards the deserts in Central Asia and in China. This transition towards the desert margin loess can be found also in eastern and southeastern Europe towards Central Asia, e.g. at the Sea of Azov and the Caspian Lowlands. Furthermore, in northern Mongolia and Siberia periglacial or mountain / tundra loess appears (Mode 1).
The concept also has relevance if used vertically: At higher elevations in semi-arid regions of central-eastern Europe and Asia (e.g. at the eastern margin of the Tibetan Plateau and the western part of the Qilian Shan) humidity controlled forest belts do not contain any loess deposits. However, in the rather high mountains and plateaus of arid Central Asia, mountain loess close to typical loess can be found. The uppermost boundary of loess is periglacial loess (Mode 1), whereas the lowermost parts are desert margin loess (Mode 3). For these regions, there are still debates on the influence of glaciers and deserts on loess formation.
Lehmkuhl et al. (in press). Loess landscapes of Europe – Mapping, geomorphology, and zonal differentiation. Earth-Science Reviews, Doi: https://doi.org/10.1016/j.earscirev.2020.103496
How to cite: Lehmkuhl, F., Hambach, U., Nett, J. J., Schulte, P., Jary, Z., Sprafke, T., Antoine, P., Wacha, L., Zerboni, A., Hošek, J., and Marković, S.: Eurasian drylands and the conceptual model of loess landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8586, https://doi.org/10.5194/egusphere-egu21-8586, 2021.
At least 10% of the Earth surface and large areas of the Eurasian continent are covered by aeolian silt and sand deposits. The origin and distribution of these deposits is indicative for the (paleo-) environment and represent an important edaphic factor for eco-zone evolution, which in turn controls past and present land use.
Here we present a conceptual model of loess landscapes in relation to past and present drylands based on the spatial analysis of loess and loess facies' in Europe (Lehmkuhl et al., 2020). Corners of our conceptual 'loess-triangle' represent three eco-zones (nival, humid, and arid environments) peripheral to 'typical' loess formation (placed in the center). The modes of loess formation are controlled by climatic factors, namely water availability and temperature, which also constrain the prevailing vegetation: Mode 1 - Periglacial and tundra loess; Mode 2 - Temperate and subtropical loess; Mode 3 - Desert margin loess. In-between these three peripheral modes of loess facies we illustrate that ‘typical’, continuous and silt dominated loess formation takes place.
At the Chinese Loess Plateau, there is a gradual transition in grain-size from the humid regions in the south and southeast to the semi-arid and arid regions in the northwest (from Mode 2 towards typical loess and Mode 3). Reduced vegetation cover at desert margins, along dry riverbeds and lakes leads to increased aeolian deflation facilitating also mid- and long-distance transport of silt-sized particles. The resulting deposits range from silty loess to sandier loess in the direction of increasing aridity towards the deserts in Central Asia and in China. This transition towards the desert margin loess can be found also in eastern and southeastern Europe towards Central Asia, e.g. at the Sea of Azov and the Caspian Lowlands. Furthermore, in northern Mongolia and Siberia periglacial or mountain / tundra loess appears (Mode 1).
The concept also has relevance if used vertically: At higher elevations in semi-arid regions of central-eastern Europe and Asia (e.g. at the eastern margin of the Tibetan Plateau and the western part of the Qilian Shan) humidity controlled forest belts do not contain any loess deposits. However, in the rather high mountains and plateaus of arid Central Asia, mountain loess close to typical loess can be found. The uppermost boundary of loess is periglacial loess (Mode 1), whereas the lowermost parts are desert margin loess (Mode 3). For these regions, there are still debates on the influence of glaciers and deserts on loess formation.
Lehmkuhl et al. (in press). Loess landscapes of Europe – Mapping, geomorphology, and zonal differentiation. Earth-Science Reviews, Doi: https://doi.org/10.1016/j.earscirev.2020.103496
How to cite: Lehmkuhl, F., Hambach, U., Nett, J. J., Schulte, P., Jary, Z., Sprafke, T., Antoine, P., Wacha, L., Zerboni, A., Hošek, J., and Marković, S.: Eurasian drylands and the conceptual model of loess landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8586, https://doi.org/10.5194/egusphere-egu21-8586, 2021.
EGU21-5284 | vPICO presentations | GM8.2
New insights into Southern Caucasian glacial-interglacial climate conditions inferred from Quaternary gastropod faunasChristiane Richter
New insights into Southern Caucasian glacial-interglacial climate conditions inferred from Quaternary gastropod faunas
Dr. Christiane Richter1, Dr. Daniel Wolf1, Dipl.-Biol. Frank Walther2, Dr. Stefan Meng3, Dr. Lilit Sahakyan4, M. Sc. Tilmann Wolpert5, Prof. Dr. Markus Fuchs5, Prof. Dr. Michael Zech1, Prof. Dr. Dominik Faust1
1Dresden University of Technology, Helmholtzstr. 10, 01069 Dresden, Germany
2 University Hamburg, Centrum für Naturkunde, Martin-Luther-Platz 3, 20146 Hamburg, Germany
3 Ernst-Moritz-Arndt-University Greifswald, Friedrich-Ludwig-Jahn-Str. 17a, 17489 Greifswald, Germany
4 National Academy of Sciences of the Republic of Armenia, Baghramyan Ave. 24a, 0019 Yerevan,
Armenia
5 Justus-Liebig-University Giessen, Senckenbergstr. 1, 35390 Gießen, Germany
We present our latest results from gastropod analyses conducted on loess palaeosol sequences from northeast Armenia (Southern Caucasia) covering at least three glacial-interglacial cycles. The ecostratigraphy shows significant patterns of species composition related to the succession of pedocomplexes and loess, respectively. Pedocomplexes included species that can be associated with highgrass- to forest-steppe biomes, indicating increased humidity for these sections compared to loess layers. In contrast, loess layers that relate to glacial periods are associated with gastropod species of semidesert environments with shrub- and shortgrass-steppes, indicating semiarid to arid conditions. Furthermore, the loess deposits do not show any evidence for cold-adapted gastropod species. Therefore we suggest that average July temperatures in the study area were above 10°C, even during periods of loess deposition. We propose, that the limiting factor for bios during glacial periods was aridity, rather than temperature. In addition, we observe environmental differences between the various glacial times, with our results indicating a trend towards steadily increasing aridity in Southern Caucasia across the Middle to Late Pleistocene.
How to cite: Richter, C.: New insights into Southern Caucasian glacial-interglacial climate conditions inferred from Quaternary gastropod faunas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5284, https://doi.org/10.5194/egusphere-egu21-5284, 2021.
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New insights into Southern Caucasian glacial-interglacial climate conditions inferred from Quaternary gastropod faunas
Dr. Christiane Richter1, Dr. Daniel Wolf1, Dipl.-Biol. Frank Walther2, Dr. Stefan Meng3, Dr. Lilit Sahakyan4, M. Sc. Tilmann Wolpert5, Prof. Dr. Markus Fuchs5, Prof. Dr. Michael Zech1, Prof. Dr. Dominik Faust1
1Dresden University of Technology, Helmholtzstr. 10, 01069 Dresden, Germany
2 University Hamburg, Centrum für Naturkunde, Martin-Luther-Platz 3, 20146 Hamburg, Germany
3 Ernst-Moritz-Arndt-University Greifswald, Friedrich-Ludwig-Jahn-Str. 17a, 17489 Greifswald, Germany
4 National Academy of Sciences of the Republic of Armenia, Baghramyan Ave. 24a, 0019 Yerevan,
Armenia
5 Justus-Liebig-University Giessen, Senckenbergstr. 1, 35390 Gießen, Germany
We present our latest results from gastropod analyses conducted on loess palaeosol sequences from northeast Armenia (Southern Caucasia) covering at least three glacial-interglacial cycles. The ecostratigraphy shows significant patterns of species composition related to the succession of pedocomplexes and loess, respectively. Pedocomplexes included species that can be associated with highgrass- to forest-steppe biomes, indicating increased humidity for these sections compared to loess layers. In contrast, loess layers that relate to glacial periods are associated with gastropod species of semidesert environments with shrub- and shortgrass-steppes, indicating semiarid to arid conditions. Furthermore, the loess deposits do not show any evidence for cold-adapted gastropod species. Therefore we suggest that average July temperatures in the study area were above 10°C, even during periods of loess deposition. We propose, that the limiting factor for bios during glacial periods was aridity, rather than temperature. In addition, we observe environmental differences between the various glacial times, with our results indicating a trend towards steadily increasing aridity in Southern Caucasia across the Middle to Late Pleistocene.
How to cite: Richter, C.: New insights into Southern Caucasian glacial-interglacial climate conditions inferred from Quaternary gastropod faunas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5284, https://doi.org/10.5194/egusphere-egu21-5284, 2021.
EGU21-14882 | vPICO presentations | GM8.2
Holocene dust accumulation in the southern Levant: the role of local sources and fixation processesAmir Sandler and Bernhard Lucke
Initial soils covering archaeological ruins in the southern Levant include fine grain size fractions that may stem from aeolian sediments. Thus, ruins could act as effective dust traps which preserved rare Holocene aeolian records. We assessed physical parameters and chemical composition of initial soils covering archaeological ruins in the Negev and southern Jordan, including clay mineralogy and Sr- and Nd-isotopes, which we compared with modern dust from collectors installed close to the sites. A significant contribution from local weathered rocks could be observed in southern Jordan. In the Negev, the contribution of rocks was negligible, probably due to greater rock hardness and abundant biological crusts sealing surfaces. However, loessial paleosols surrounding the sampled archaeological ruins were "recycled" in the Negev. Compared to modern settled dust, archaeological soils in southern Jordan are enriched with various major and trace elements associated with clays and oxide coatings of fine silt particles. This was not due to in-situ weathering, which was found to be minimal. However, site-specific fixation processes may explain variations of dust records at the studied sites. In addition, modern dust samples associated with precipitation, in particular snow, were found associated with higher amounts of major and trace elements. Initial soils covering ruins in the southern Levant therefore suggest that the formation of soils in desert fringes may less be a function of dust supply, but more of dust deposition and fixation processes. There are multiple, local and regional dust sources and dust-generating processes active in drylands, but deep loessial soils form only when dust fixation is effective.
How to cite: Sandler, A. and Lucke, B.: Holocene dust accumulation in the southern Levant: the role of local sources and fixation processes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14882, https://doi.org/10.5194/egusphere-egu21-14882, 2021.
Initial soils covering archaeological ruins in the southern Levant include fine grain size fractions that may stem from aeolian sediments. Thus, ruins could act as effective dust traps which preserved rare Holocene aeolian records. We assessed physical parameters and chemical composition of initial soils covering archaeological ruins in the Negev and southern Jordan, including clay mineralogy and Sr- and Nd-isotopes, which we compared with modern dust from collectors installed close to the sites. A significant contribution from local weathered rocks could be observed in southern Jordan. In the Negev, the contribution of rocks was negligible, probably due to greater rock hardness and abundant biological crusts sealing surfaces. However, loessial paleosols surrounding the sampled archaeological ruins were "recycled" in the Negev. Compared to modern settled dust, archaeological soils in southern Jordan are enriched with various major and trace elements associated with clays and oxide coatings of fine silt particles. This was not due to in-situ weathering, which was found to be minimal. However, site-specific fixation processes may explain variations of dust records at the studied sites. In addition, modern dust samples associated with precipitation, in particular snow, were found associated with higher amounts of major and trace elements. Initial soils covering ruins in the southern Levant therefore suggest that the formation of soils in desert fringes may less be a function of dust supply, but more of dust deposition and fixation processes. There are multiple, local and regional dust sources and dust-generating processes active in drylands, but deep loessial soils form only when dust fixation is effective.
How to cite: Sandler, A. and Lucke, B.: Holocene dust accumulation in the southern Levant: the role of local sources and fixation processes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14882, https://doi.org/10.5194/egusphere-egu21-14882, 2021.
EGU21-15919 | vPICO presentations | GM8.2
The aggradation process of transversal dunes since late-Pleistocene in Badain Jaran Desert, northwest China revealed by OSL datingQinjing Shen and Zhongping Lai
Transversal dunes are widespread in many deserts, but the application of these un-stabilized dunes in the palaeoclimate region is limited. Because transversal dunes normally migrate too fast, which means this kind of dune has a low possibility to record long period paleoclimate information. Nevertheless, both model simulations and field observation demonstrate that larger (higher) dunes containing a greater mass of sand have longer turn-over times. If so, there may be particular giant transversal dunes, in which long periods of climate changes are actually preserved and could be used as geoproxy to reconstruct paleoenvironment changes.
The Badain Jaran desert, situated in north-western China, features the tallest dunes (about 480 m) on the earth. More than 50% of the sand sea is covered by transversal dunes with an average height of 200 to 300 m. Here, we investigated two representative mega-dunes in the center of the desert and took 22 OSL samples systematically to try to reconstruct the deposition history of these two mega-dunes. Our result demonstrates that one of the dunes is formed since ~62 ka, with two phases of superposed dunes dated to 26~32 ka and modern time. Another mage-dune started to deposited from 29 ka and climbed by early to middle Holocene superposed-dunes and modern ones. Furthermore, while other active sand seas preserve scarcely aeolian sand deposited during the LGM period (Last Glacial Maximum: 26.5-19.0 ka BP), 11 of our 22 OSL dating results fall into the LGM period, which indicates that mega-dunes in the Badain Jaran desert continue aggradation during LGM. In that case，we speculate there are at least three factors facilitating the mega-dunes in Badain Jaran desert different from other transversal dunes that can preserve LGM sediments. (1) Badain Jaran desert, situated in a relatively subsiding basin, has a favor deposition condition; (2) The desert is close to the aeolian sand provenance area, an alluvial fan stored abundant silt-sand material derived from the southeast Tibet; (3) the shallow buried wet sand in Badain Jaran desert may promote the formation of the mega-dunes and reduce their migration speed, so that extend the turn-over times of the mega-dunes.
How to cite: Shen, Q. and Lai, Z.: The aggradation process of transversal dunes since late-Pleistocene in Badain Jaran Desert, northwest China revealed by OSL dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15919, https://doi.org/10.5194/egusphere-egu21-15919, 2021.
Transversal dunes are widespread in many deserts, but the application of these un-stabilized dunes in the palaeoclimate region is limited. Because transversal dunes normally migrate too fast, which means this kind of dune has a low possibility to record long period paleoclimate information. Nevertheless, both model simulations and field observation demonstrate that larger (higher) dunes containing a greater mass of sand have longer turn-over times. If so, there may be particular giant transversal dunes, in which long periods of climate changes are actually preserved and could be used as geoproxy to reconstruct paleoenvironment changes.
The Badain Jaran desert, situated in north-western China, features the tallest dunes (about 480 m) on the earth. More than 50% of the sand sea is covered by transversal dunes with an average height of 200 to 300 m. Here, we investigated two representative mega-dunes in the center of the desert and took 22 OSL samples systematically to try to reconstruct the deposition history of these two mega-dunes. Our result demonstrates that one of the dunes is formed since ~62 ka, with two phases of superposed dunes dated to 26~32 ka and modern time. Another mage-dune started to deposited from 29 ka and climbed by early to middle Holocene superposed-dunes and modern ones. Furthermore, while other active sand seas preserve scarcely aeolian sand deposited during the LGM period (Last Glacial Maximum: 26.5-19.0 ka BP), 11 of our 22 OSL dating results fall into the LGM period, which indicates that mega-dunes in the Badain Jaran desert continue aggradation during LGM. In that case，we speculate there are at least three factors facilitating the mega-dunes in Badain Jaran desert different from other transversal dunes that can preserve LGM sediments. (1) Badain Jaran desert, situated in a relatively subsiding basin, has a favor deposition condition; (2) The desert is close to the aeolian sand provenance area, an alluvial fan stored abundant silt-sand material derived from the southeast Tibet; (3) the shallow buried wet sand in Badain Jaran desert may promote the formation of the mega-dunes and reduce their migration speed, so that extend the turn-over times of the mega-dunes.
How to cite: Shen, Q. and Lai, Z.: The aggradation process of transversal dunes since late-Pleistocene in Badain Jaran Desert, northwest China revealed by OSL dating, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15919, https://doi.org/10.5194/egusphere-egu21-15919, 2021.
EGU21-8276 | vPICO presentations | GM8.2
Star dunes: Global distribution, characteristics and formationManuel Herzog and Olaf Bubenzer
The distribution, characteristics and formation of mega-dune forms (esp. star dunes) is, compared to smaller dune forms, for example barchans and linear dunes, much more complex and still poorly investigated. Although occurring globally nearly in all sand seas (ergs), due to their location in often remote and hyper-arid environments and their complexity, they are highly underrepresented in recent research. Last methodological research and reviews, apart from regional case studies (e.g. Zhang et al. 2016), were published decades ago (e.g. Lancaster 1989). In consequence, definitions and development theories remain more or less constant over time, describing star dunes of pyramidal shape with three to four arms, of significant size and mostly situated in depositional centers. Recognized by most researcher, their formation seems to be bound to a regional wind system with a high directional variability by concurrent and sufficient sediment availability. However, a modern assessment of the global star dune distribution is missing.
Therefore, we will present first results of an analysis of global star dune occurrence and distribution via freely available and also highly resolute satellite data provided by Google Earth and ESRI base map services in order to summarize their locations, morphometric characteristics as well as their environmental setting and to explore similarities and differences. Overall, an assessment of a global star dune inventory can lead to a more precise morphometric description, definition, and a better comparison of these dune forms and therefore can contribute to a better understanding of their evolution.
Lancaster, N. (1989). Star dunes. Progress in Physical Geography 13, 67-91.
Zhang, W., Qu, J., Tan, L., Jing, Z., Bian, K. and Niu, Q. (2016). Environmental dynamics of a star dune. Geomorphology 273, 28-38.
How to cite: Herzog, M. and Bubenzer, O.: Star dunes: Global distribution, characteristics and formation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8276, https://doi.org/10.5194/egusphere-egu21-8276, 2021.
The distribution, characteristics and formation of mega-dune forms (esp. star dunes) is, compared to smaller dune forms, for example barchans and linear dunes, much more complex and still poorly investigated. Although occurring globally nearly in all sand seas (ergs), due to their location in often remote and hyper-arid environments and their complexity, they are highly underrepresented in recent research. Last methodological research and reviews, apart from regional case studies (e.g. Zhang et al. 2016), were published decades ago (e.g. Lancaster 1989). In consequence, definitions and development theories remain more or less constant over time, describing star dunes of pyramidal shape with three to four arms, of significant size and mostly situated in depositional centers. Recognized by most researcher, their formation seems to be bound to a regional wind system with a high directional variability by concurrent and sufficient sediment availability. However, a modern assessment of the global star dune distribution is missing.
Therefore, we will present first results of an analysis of global star dune occurrence and distribution via freely available and also highly resolute satellite data provided by Google Earth and ESRI base map services in order to summarize their locations, morphometric characteristics as well as their environmental setting and to explore similarities and differences. Overall, an assessment of a global star dune inventory can lead to a more precise morphometric description, definition, and a better comparison of these dune forms and therefore can contribute to a better understanding of their evolution.
Lancaster, N. (1989). Star dunes. Progress in Physical Geography 13, 67-91.
Zhang, W., Qu, J., Tan, L., Jing, Z., Bian, K. and Niu, Q. (2016). Environmental dynamics of a star dune. Geomorphology 273, 28-38.
How to cite: Herzog, M. and Bubenzer, O.: Star dunes: Global distribution, characteristics and formation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8276, https://doi.org/10.5194/egusphere-egu21-8276, 2021.
EGU21-3262 | vPICO presentations | GM8.2
Aeolian-fluvial sediments and landscapes along the northwestern Negev Dunefield (Israel) margins since the late PleistoceneLotem Robins, Joel Roskin, Lupeng Yu, and Noam Greenbaum
Dunefield margins are prone to changing domination between aeolian and fluvial systems. Dominating aeolian systems divert or block fluvial systems or/and reduce their erosional forces often leading to amplified sedimentation by a wide range of unique aeolian-fluvial (A-F) sediments. Other arid environments are mainly dominated by eroding ephemeral fluvial systems that usually characterized by sediment degradation.
The late Pleistocene encroachment of vegetated linear dunes into the northwestern Negev desert dunefield (Israel) comprised a distinct period of aeolian domination upon ephemeral drainage systems originating in the loess-clad Central Negev highlands. This study analyzes the sediments, geomorphology and landscape evolution caused by A-F processes along dunefield margins, in particular sediments deposited by dune-dammed water bodies slightly upstream of the dunefield edge and between VLDs, using high-resolution field mapping, relative (portable) and absolute OSL dating, stratigraphy and sedimentological analyses. These sediments have been generally mapped as playa sediments, understood to be deposited in a fluvial-dominated environment.
Six main A-F sediment types were identified and interpreted: (a) Aeolian sand appears to be remnants of fluvial eroded VLD. (b) Fluvial sand originates from dune erosion and deposited nearby. (c) Massive loam to silty-clay loam relates to abrupt changes in the hydraulic parameters (width/depth ratio and water losses through infiltration) which induce sudden change in flow velocity, resulting in unsorted massive deposits of upstream loess and other desert soil bedload. (d) Couplets, similar to the massive loam, contains loess and upstream sediments deposited in a standing water body. (e) Laminated silty-clay-loam units were identified only between VLDs. (f) High-energy fluvial deposits, which contain loam, sand and pebbles, with a clear erosional boundary that mark the upstream edge of A-F sedimentation.
The landscape of the Negev dunefield margins developed since the late Pleistocene by short-term aeolian domination, which gradually changed into fluvial domination during the Holocene. Dune-damming depositions occurred during this transition. First outside the dunefield, then propagated downstream into the dunefield. Fluvial aggradation of A-F sediments resulted in a vast playa-like flats, that following dune-dam breaching underwent incision, let alone in small (~<20 km2) basins.
How to cite: Robins, L., Roskin, J., Yu, L., and Greenbaum, N.: Aeolian-fluvial sediments and landscapes along the northwestern Negev Dunefield (Israel) margins since the late Pleistocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3262, https://doi.org/10.5194/egusphere-egu21-3262, 2021.
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Dunefield margins are prone to changing domination between aeolian and fluvial systems. Dominating aeolian systems divert or block fluvial systems or/and reduce their erosional forces often leading to amplified sedimentation by a wide range of unique aeolian-fluvial (A-F) sediments. Other arid environments are mainly dominated by eroding ephemeral fluvial systems that usually characterized by sediment degradation.
The late Pleistocene encroachment of vegetated linear dunes into the northwestern Negev desert dunefield (Israel) comprised a distinct period of aeolian domination upon ephemeral drainage systems originating in the loess-clad Central Negev highlands. This study analyzes the sediments, geomorphology and landscape evolution caused by A-F processes along dunefield margins, in particular sediments deposited by dune-dammed water bodies slightly upstream of the dunefield edge and between VLDs, using high-resolution field mapping, relative (portable) and absolute OSL dating, stratigraphy and sedimentological analyses. These sediments have been generally mapped as playa sediments, understood to be deposited in a fluvial-dominated environment.
Six main A-F sediment types were identified and interpreted: (a) Aeolian sand appears to be remnants of fluvial eroded VLD. (b) Fluvial sand originates from dune erosion and deposited nearby. (c) Massive loam to silty-clay loam relates to abrupt changes in the hydraulic parameters (width/depth ratio and water losses through infiltration) which induce sudden change in flow velocity, resulting in unsorted massive deposits of upstream loess and other desert soil bedload. (d) Couplets, similar to the massive loam, contains loess and upstream sediments deposited in a standing water body. (e) Laminated silty-clay-loam units were identified only between VLDs. (f) High-energy fluvial deposits, which contain loam, sand and pebbles, with a clear erosional boundary that mark the upstream edge of A-F sedimentation.
The landscape of the Negev dunefield margins developed since the late Pleistocene by short-term aeolian domination, which gradually changed into fluvial domination during the Holocene. Dune-damming depositions occurred during this transition. First outside the dunefield, then propagated downstream into the dunefield. Fluvial aggradation of A-F sediments resulted in a vast playa-like flats, that following dune-dam breaching underwent incision, let alone in small (~<20 km2) basins.
How to cite: Robins, L., Roskin, J., Yu, L., and Greenbaum, N.: Aeolian-fluvial sediments and landscapes along the northwestern Negev Dunefield (Israel) margins since the late Pleistocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3262, https://doi.org/10.5194/egusphere-egu21-3262, 2021.
EGU21-7502 | vPICO presentations | GM8.2
Distribution of fluvial sediment yields in hyper-arid areas, exemplified by Nahal Nehushtan, IsraelRachel Armoza-Zvuloni, Yanai Shlomi, Itay Abadi, Rachamim Shem-Tov, and Jonathan B. Laronne
Floods rarely occur in hyper-arid deserts and little is known about the magnitude and frequency of sediment delivery from their basins, despite their importance to changes to the landscape as well as to infrastructures and engineering activities. Sediment yield from the Nahal Nehushtan watershed (15.7 km2) located in the Timna Valley in southern Israel, was determined by assessing stratigraphic sections in its 60-year reservoir deposits. Stratigraphic correlation between event couplets allowed quantification of sediment yields representing 13 former flash-flood events. Based on the sediment volume in the reservoir, the 24.6 t km-2 y-1 average sediment yield is the lowest among other studied warm deserts. Among the event layers, five are voluminously small and seven are medium-sized. The thickest layer, deposited by a flash flood caused by a single short rain event, contributed 29% of the total sediment yield. This demonstrates the overarching effect of medium magnitude events on the rate of sediment production in a hyper-arid setting. Based on event reservoir sedimentation from watersheds located in several hyper-arid areas in the Middle East and North America, sediment load increases with drainage area as expected; however, sediment yield does not decrease with drainage area, as was shown for arid environments. Overall, mean annual sediment yield is very low and increases with flood frequency, with considerable variation generated by local characteristics. Our quantitative results together with previous studies of hyper-arid areas, provide complementary evidence of fluvial sediment transport - the main landscape designer in fluvial desert landscapes.
How to cite: Armoza-Zvuloni, R., Shlomi, Y., Abadi, I., Shem-Tov, R., and Laronne, J. B.: Distribution of fluvial sediment yields in hyper-arid areas, exemplified by Nahal Nehushtan, Israel , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7502, https://doi.org/10.5194/egusphere-egu21-7502, 2021.
Floods rarely occur in hyper-arid deserts and little is known about the magnitude and frequency of sediment delivery from their basins, despite their importance to changes to the landscape as well as to infrastructures and engineering activities. Sediment yield from the Nahal Nehushtan watershed (15.7 km2) located in the Timna Valley in southern Israel, was determined by assessing stratigraphic sections in its 60-year reservoir deposits. Stratigraphic correlation between event couplets allowed quantification of sediment yields representing 13 former flash-flood events. Based on the sediment volume in the reservoir, the 24.6 t km-2 y-1 average sediment yield is the lowest among other studied warm deserts. Among the event layers, five are voluminously small and seven are medium-sized. The thickest layer, deposited by a flash flood caused by a single short rain event, contributed 29% of the total sediment yield. This demonstrates the overarching effect of medium magnitude events on the rate of sediment production in a hyper-arid setting. Based on event reservoir sedimentation from watersheds located in several hyper-arid areas in the Middle East and North America, sediment load increases with drainage area as expected; however, sediment yield does not decrease with drainage area, as was shown for arid environments. Overall, mean annual sediment yield is very low and increases with flood frequency, with considerable variation generated by local characteristics. Our quantitative results together with previous studies of hyper-arid areas, provide complementary evidence of fluvial sediment transport - the main landscape designer in fluvial desert landscapes.
How to cite: Armoza-Zvuloni, R., Shlomi, Y., Abadi, I., Shem-Tov, R., and Laronne, J. B.: Distribution of fluvial sediment yields in hyper-arid areas, exemplified by Nahal Nehushtan, Israel , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7502, https://doi.org/10.5194/egusphere-egu21-7502, 2021.
EGU21-3438 | vPICO presentations | GM8.2
The potential of small mountain river systems for paleoenvironmental reconstructions in drylands - An example from the Binaloud Mountains in northeastern IranAzra Khosravichenar, Morteza Fattahi, Hamideh Amini, and Hans von Suchodoletz
Fluvial sediments are valuable paleoenvironmental archives of the Quaternary. Since besides environmental factors they are also affected by local tectonics or intrinsic processes, large instead of small catchments should be studied. In drylands covering ca. 45% of the global terrestrial surface large river systems are generally missing, and most river systems are small rivers originating from mountain ranges. Their sediments are potentially interesting paleoenvironmental archives, but are often affected by intensive tectonics. During this study, to obtain a robust regional paleoenvironmental signal a small river system in the southwestern Binaloud Mountains in semi-arid NE Iran was exemplarily studied with a combined approach that encompassed both alluvial fan and catchment. By using geomorphological mapping and numerical dating, fluvial aggradation followed by incision was independently identified in larger areas or in different parts of the river system ca. 95–88 ka, 40 ka, 20 ka, around/after the Pleistocene/Holocene transition and possibly ca. 2.6 ka. These could be linked with regional and over-regional paleoenvironmental data. Furthermore, large boulders on the alluvial fan suggest anthropogenic destabilisation of the catchment during the last decades. Despite strong local tectonics the fluvial dynamics was mostly controlled by paleoenvironmental changes and human activity. This indicates that despite their small size, such river systems form valuable paleoenvironmental archives in drylands where other archive types are largely missing.
How to cite: Khosravichenar, A., Fattahi, M., Amini, H., and von Suchodoletz, H.: The potential of small mountain river systems for paleoenvironmental reconstructions in drylands - An example from the Binaloud Mountains in northeastern Iran, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3438, https://doi.org/10.5194/egusphere-egu21-3438, 2021.
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Fluvial sediments are valuable paleoenvironmental archives of the Quaternary. Since besides environmental factors they are also affected by local tectonics or intrinsic processes, large instead of small catchments should be studied. In drylands covering ca. 45% of the global terrestrial surface large river systems are generally missing, and most river systems are small rivers originating from mountain ranges. Their sediments are potentially interesting paleoenvironmental archives, but are often affected by intensive tectonics. During this study, to obtain a robust regional paleoenvironmental signal a small river system in the southwestern Binaloud Mountains in semi-arid NE Iran was exemplarily studied with a combined approach that encompassed both alluvial fan and catchment. By using geomorphological mapping and numerical dating, fluvial aggradation followed by incision was independently identified in larger areas or in different parts of the river system ca. 95–88 ka, 40 ka, 20 ka, around/after the Pleistocene/Holocene transition and possibly ca. 2.6 ka. These could be linked with regional and over-regional paleoenvironmental data. Furthermore, large boulders on the alluvial fan suggest anthropogenic destabilisation of the catchment during the last decades. Despite strong local tectonics the fluvial dynamics was mostly controlled by paleoenvironmental changes and human activity. This indicates that despite their small size, such river systems form valuable paleoenvironmental archives in drylands where other archive types are largely missing.
How to cite: Khosravichenar, A., Fattahi, M., Amini, H., and von Suchodoletz, H.: The potential of small mountain river systems for paleoenvironmental reconstructions in drylands - An example from the Binaloud Mountains in northeastern Iran, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3438, https://doi.org/10.5194/egusphere-egu21-3438, 2021.
EGU21-2325 | vPICO presentations | GM8.2
Luminescence dating Hajar Mountain alluvial fan systems, northern OmanSam Woor, Julie Durcan, Ash Parton, and David Thomas
The alluvial/fluvial fan systems of northern Oman act as sensitive geoproxy records of Late Quaternary palaeohydrology and past landscape evolution, offering records of palaeoenvironmental change which cannot be reconstructed from nearby speleothem records alone (Parton et al., 2013). These systems also provide evidence for the important link between the changing abundance of freshwater in the Arabian interior and the dispersal of anatomically modern humans (AMHs) out of Africa (Rosenberg et al., 2012). Limited previous luminescence dating analyses have reported fan activation west of the Hajar during insolation maxima and monsoon intensification throughout the Late Quaternary (Parton et al., 2015). However, there are currently no studies to date which present chronologies for the fan systems to the east of the Hajar Mountains.
We present the first luminescence based chronology for the fan systems to the east of the Hajar Mountains, providing landform scale data on fan behaviour, including spatial-temporal complexity and variability. This facilitates comparison of the temporal response of fans east and west of the mountains, including differential responses to external forcing. Ages will also be compared with regional palaeoenvironmental and palaeoclimatic records, to inform landscape reconstructions in northern Oman during the late Quaternary.
References
Rosenberg, T.M., Preusser, F., Blechschmidt, I., Fleitmann, D., Jagher, R. and Matter, A., 2012. Late Pleistocene palaeolake in the interior of Oman: a potential key area for the dispersal of anatomically modern humans out‐of‐Africa?. Journal of Quaternary Science, 27(1), pp.13-16.
Parton, A., Farrant, A.R., Leng, M.J., Schwenninger, J.L., Rose, J.I., Uerpmann, H.P. and Parker, A.G., 2013. An early MIS 3 pluvial phase in Southeast Arabia: climatic and archaeological implications. Quaternary International, 300, pp.62-74.
Parton, A., Farrant, A.R., Leng, M.J., Telfer, M.W., Groucutt, H.S., Petraglia, M.D. and Parker, A.G., 2015. Alluvial fan records from southeast Arabia reveal multiple windows for human dispersal. Geology, 43(4), pp.295-298.
How to cite: Woor, S., Durcan, J., Parton, A., and Thomas, D.: Luminescence dating Hajar Mountain alluvial fan systems, northern Oman , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2325, https://doi.org/10.5194/egusphere-egu21-2325, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The alluvial/fluvial fan systems of northern Oman act as sensitive geoproxy records of Late Quaternary palaeohydrology and past landscape evolution, offering records of palaeoenvironmental change which cannot be reconstructed from nearby speleothem records alone (Parton et al., 2013). These systems also provide evidence for the important link between the changing abundance of freshwater in the Arabian interior and the dispersal of anatomically modern humans (AMHs) out of Africa (Rosenberg et al., 2012). Limited previous luminescence dating analyses have reported fan activation west of the Hajar during insolation maxima and monsoon intensification throughout the Late Quaternary (Parton et al., 2015). However, there are currently no studies to date which present chronologies for the fan systems to the east of the Hajar Mountains.
We present the first luminescence based chronology for the fan systems to the east of the Hajar Mountains, providing landform scale data on fan behaviour, including spatial-temporal complexity and variability. This facilitates comparison of the temporal response of fans east and west of the mountains, including differential responses to external forcing. Ages will also be compared with regional palaeoenvironmental and palaeoclimatic records, to inform landscape reconstructions in northern Oman during the late Quaternary.
References
Rosenberg, T.M., Preusser, F., Blechschmidt, I., Fleitmann, D., Jagher, R. and Matter, A., 2012. Late Pleistocene palaeolake in the interior of Oman: a potential key area for the dispersal of anatomically modern humans out‐of‐Africa?. Journal of Quaternary Science, 27(1), pp.13-16.
Parton, A., Farrant, A.R., Leng, M.J., Schwenninger, J.L., Rose, J.I., Uerpmann, H.P. and Parker, A.G., 2013. An early MIS 3 pluvial phase in Southeast Arabia: climatic and archaeological implications. Quaternary International, 300, pp.62-74.
Parton, A., Farrant, A.R., Leng, M.J., Telfer, M.W., Groucutt, H.S., Petraglia, M.D. and Parker, A.G., 2015. Alluvial fan records from southeast Arabia reveal multiple windows for human dispersal. Geology, 43(4), pp.295-298.
How to cite: Woor, S., Durcan, J., Parton, A., and Thomas, D.: Luminescence dating Hajar Mountain alluvial fan systems, northern Oman , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2325, https://doi.org/10.5194/egusphere-egu21-2325, 2021.
EGU21-2525 | vPICO presentations | GM8.2
Active earth-surface processes following rainfall events in the southern Namib Desert – Insights from the Kaukausib catchment by means of remote sensingFelix Henselowsky, Tobias Ullmann, Max Engel, and Olaf Bubenzer
Active earth-surface processes in desert environments can be well studied by utilizing recent spaceborne remote sensing imagery e.g. from the European Sentinel Missions. Insights on these processes are important to serve as modern analogues for the long-term landscape evolution of drylands and the preservation of paleoenvironmental archives. The multi-sensor fusion of latest earth-observation data, e.g. multispectral optical imagery, Synthetic Aperture Radar (SAR) data and/or digital elevation models (DEM´s), allows to distinguish landforms between very young and active to stable – presumably older – geomorphological units, the co-existence of which is a striking phenomenon in arid environments. Based upon this methodological approach, the current landscape dynamics in the hyper-arid southern Namib Desert are studied in a key area for past, current and future environmental changes in desert environments of the Southern Hemisphere: the Kaukausib catchment.
The Kaukausib catchment, located in-between two major atmospheric circulation patterns with tropical (summer rainfall) and extratropical (winter rainfall) influence, is highly sensitive to changes and interactions of both climate systems. The catchment is bounded by the Great Escarpment and receives no discharge from the higher hinterland. As such, fluvial activity and resulting landforms are related to local precipitation only. Consequently, the landform inventory of this distinct catchment is a unique recorder of recent and past climate dynamics of the Southern African drylands.
Preliminary investigations identified the high sensitivity of the Kaukausib catchment to recent short-term environmental changes. Rare extraordinary rainfall events, exceeding the average annual amount of less than 50 mm, lead to temporary changes in vegetation cover and density. These events seem to occur in a frequency of 6–11 years, at least during the last 30 years. They are mostly associated with atmospheric interaction of the tropical and extratropical circulation patterns in spring and autumn, e.g. in April 2006 with an unusual northward position of a cut-off-low from the temperate climate system in phase with a Temperate Tropical Through from the tropics unusually far south. The spatio-temporal changes of vegetation cover subsequent to these extraordinary rainfalls are studied by analyzing time series of Landsat 5. Vegetation vitality has its maximum three months after the rainfalls, where in some regions a rather dense cover of annual and ephemeral grass occurred (Henselowsky et al. 2019 Z. f. Geomorph https://doi.org/10.1127/zfg_suppl/2019/0552).
In addition, fluvial events following rainfalls in 2020 and 2018 are studied using Sentinel-1 data to identify short-term surface changes, but also to detect presumable stable sediment surfaces. Sporadic fluvial activity in turn is revealed by investigating signal differences in SAR intensity and InSAR coherence before and after fluvial activity. Information on channel activity is interpreted in the context of the morphometric characteristics and first field-investigations in the Anib and Arasab Pan. These pans limit the current runoff of the upper Kaukausib and represent the largest sediment basins of the southern Namib Desert. Therefore, the identification of current surface processes and sediment provenances, identified by spectral indices of optical satellite data, sets the baseline for future in-depth investigation of its sedimentary record and paleoenvironmental changes in the Kaukausib catchment.
How to cite: Henselowsky, F., Ullmann, T., Engel, M., and Bubenzer, O.: Active earth-surface processes following rainfall events in the southern Namib Desert – Insights from the Kaukausib catchment by means of remote sensing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2525, https://doi.org/10.5194/egusphere-egu21-2525, 2021.
Active earth-surface processes in desert environments can be well studied by utilizing recent spaceborne remote sensing imagery e.g. from the European Sentinel Missions. Insights on these processes are important to serve as modern analogues for the long-term landscape evolution of drylands and the preservation of paleoenvironmental archives. The multi-sensor fusion of latest earth-observation data, e.g. multispectral optical imagery, Synthetic Aperture Radar (SAR) data and/or digital elevation models (DEM´s), allows to distinguish landforms between very young and active to stable – presumably older – geomorphological units, the co-existence of which is a striking phenomenon in arid environments. Based upon this methodological approach, the current landscape dynamics in the hyper-arid southern Namib Desert are studied in a key area for past, current and future environmental changes in desert environments of the Southern Hemisphere: the Kaukausib catchment.
The Kaukausib catchment, located in-between two major atmospheric circulation patterns with tropical (summer rainfall) and extratropical (winter rainfall) influence, is highly sensitive to changes and interactions of both climate systems. The catchment is bounded by the Great Escarpment and receives no discharge from the higher hinterland. As such, fluvial activity and resulting landforms are related to local precipitation only. Consequently, the landform inventory of this distinct catchment is a unique recorder of recent and past climate dynamics of the Southern African drylands.
Preliminary investigations identified the high sensitivity of the Kaukausib catchment to recent short-term environmental changes. Rare extraordinary rainfall events, exceeding the average annual amount of less than 50 mm, lead to temporary changes in vegetation cover and density. These events seem to occur in a frequency of 6–11 years, at least during the last 30 years. They are mostly associated with atmospheric interaction of the tropical and extratropical circulation patterns in spring and autumn, e.g. in April 2006 with an unusual northward position of a cut-off-low from the temperate climate system in phase with a Temperate Tropical Through from the tropics unusually far south. The spatio-temporal changes of vegetation cover subsequent to these extraordinary rainfalls are studied by analyzing time series of Landsat 5. Vegetation vitality has its maximum three months after the rainfalls, where in some regions a rather dense cover of annual and ephemeral grass occurred (Henselowsky et al. 2019 Z. f. Geomorph https://doi.org/10.1127/zfg_suppl/2019/0552).
In addition, fluvial events following rainfalls in 2020 and 2018 are studied using Sentinel-1 data to identify short-term surface changes, but also to detect presumable stable sediment surfaces. Sporadic fluvial activity in turn is revealed by investigating signal differences in SAR intensity and InSAR coherence before and after fluvial activity. Information on channel activity is interpreted in the context of the morphometric characteristics and first field-investigations in the Anib and Arasab Pan. These pans limit the current runoff of the upper Kaukausib and represent the largest sediment basins of the southern Namib Desert. Therefore, the identification of current surface processes and sediment provenances, identified by spectral indices of optical satellite data, sets the baseline for future in-depth investigation of its sedimentary record and paleoenvironmental changes in the Kaukausib catchment.
How to cite: Henselowsky, F., Ullmann, T., Engel, M., and Bubenzer, O.: Active earth-surface processes following rainfall events in the southern Namib Desert – Insights from the Kaukausib catchment by means of remote sensing, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2525, https://doi.org/10.5194/egusphere-egu21-2525, 2021.
EGU21-12511 | vPICO presentations | GM8.2
Middle Holocene environmental reconstruction and climatic inferences through multi-proxy records from Seymareh lake sediments (Zagros Mts., Iran)Michele Delchiaro, Giulia Iacobucci, Francesco Troiani, Marta Della Seta, Paolo Ballato, and Luca Aldega
The Seymareh landslide is the largest rock slope failure (44 Gm3) ever recorded on the exposed Earth surface. It detached ∼10 ka BP from the northeastern flank of the Kabir-Kuh anticline (Zagros Mts., Iran) originating the natural dam responsible for the formation of a three-lake system (Seymareh, Jaidar, and Balmak lakes, with an area of 259, 46, and 5 km2, respectively). The lake system persisted for ∼3000 yr during the Holocene before its emptying phase due to overflow. A sedimentation rate of 21 mm yr−1 was estimated for the Seymareh lacustrine deposits, which increased during the early stage of lake emptying because of enhanced sediment yield from the lake tributaries.
To reconstruct the climatic and environmental impact on the lake infilling, we reviewed the geomorphology of the basins and combined the results with multi-proxy records from a 30 m thick lacustrine sequence in Seymareh Lake. Major analyses comprise grain size analysis, carbon and oxygen stable isotopes of carbonate-bearing sediments, and X-ray diffraction analysis of clay minerals.
Lake overflowing is largely accepted as the main response to variations in water discharge and sediment supply since the alternation from dry to wet phases enhances sediment mobilization along hillslopes decreasing the accommodation space in the downstream sedimentary basins. In this regard, during the early-middle Holocene, the Seymareh area, as well as the entire Middle East, was affected by short-term climate changes at the millennial-scale, as testified by both paleoecological and archaeological evidence. Indeed, several records from Iranian lakes (i.e., Mirabad, Zeribar, Urmia) well documented the temperature and the moisture conditions of the western Zagros Mountains during the Holocene. During the early Holocene, the precipitation remained low up to 6 ka BP, reaching the driest condition around 8-8.2 ka BP. The impact of this abrupt climate change is evident across West Asia, where the first large villages with domesticated cereals and sheeps disappeared, converting to small hamlets and starting habitat-tracking. As regards the Seymareh area, a more irregular distribution of rainfalls and their increasing seasonality may support rhexistasy conditions, during which the scarce vegetation cover enhances both the hillslope erosion and sedimentation rate in the basins, most likely contributing to the overflow of Seymareh Lake.
How to cite: Delchiaro, M., Iacobucci, G., Troiani, F., Della Seta, M., Ballato, P., and Aldega, L.: Middle Holocene environmental reconstruction and climatic inferences through multi-proxy records from Seymareh lake sediments (Zagros Mts., Iran), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12511, https://doi.org/10.5194/egusphere-egu21-12511, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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The Seymareh landslide is the largest rock slope failure (44 Gm3) ever recorded on the exposed Earth surface. It detached ∼10 ka BP from the northeastern flank of the Kabir-Kuh anticline (Zagros Mts., Iran) originating the natural dam responsible for the formation of a three-lake system (Seymareh, Jaidar, and Balmak lakes, with an area of 259, 46, and 5 km2, respectively). The lake system persisted for ∼3000 yr during the Holocene before its emptying phase due to overflow. A sedimentation rate of 21 mm yr−1 was estimated for the Seymareh lacustrine deposits, which increased during the early stage of lake emptying because of enhanced sediment yield from the lake tributaries.
To reconstruct the climatic and environmental impact on the lake infilling, we reviewed the geomorphology of the basins and combined the results with multi-proxy records from a 30 m thick lacustrine sequence in Seymareh Lake. Major analyses comprise grain size analysis, carbon and oxygen stable isotopes of carbonate-bearing sediments, and X-ray diffraction analysis of clay minerals.
Lake overflowing is largely accepted as the main response to variations in water discharge and sediment supply since the alternation from dry to wet phases enhances sediment mobilization along hillslopes decreasing the accommodation space in the downstream sedimentary basins. In this regard, during the early-middle Holocene, the Seymareh area, as well as the entire Middle East, was affected by short-term climate changes at the millennial-scale, as testified by both paleoecological and archaeological evidence. Indeed, several records from Iranian lakes (i.e., Mirabad, Zeribar, Urmia) well documented the temperature and the moisture conditions of the western Zagros Mountains during the Holocene. During the early Holocene, the precipitation remained low up to 6 ka BP, reaching the driest condition around 8-8.2 ka BP. The impact of this abrupt climate change is evident across West Asia, where the first large villages with domesticated cereals and sheeps disappeared, converting to small hamlets and starting habitat-tracking. As regards the Seymareh area, a more irregular distribution of rainfalls and their increasing seasonality may support rhexistasy conditions, during which the scarce vegetation cover enhances both the hillslope erosion and sedimentation rate in the basins, most likely contributing to the overflow of Seymareh Lake.
How to cite: Delchiaro, M., Iacobucci, G., Troiani, F., Della Seta, M., Ballato, P., and Aldega, L.: Middle Holocene environmental reconstruction and climatic inferences through multi-proxy records from Seymareh lake sediments (Zagros Mts., Iran), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12511, https://doi.org/10.5194/egusphere-egu21-12511, 2021.
EGU21-3390 | vPICO presentations | GM8.2
Mongolian dryland paleoenvironment and paleoclimate issues : calibrations and applicability of GDGT and pollen reconstructions over the Late Holocene.Lucas Dugerdil, Sébastien Joannin, Odile Peyron, Isabelle Jouffroy-Bapicot, Boris Vannière, Boldgiv Bazartseren, Julia Unkelbach, Hermann Behling, and Guillemette Ménot
Our understanding of climate changes throughout the Holocene is hampered by representativeness in sedimentary archives. Potential production and preservation biases of the markers are identified by comparing these proxies with modern environments. It is important to conduct robust calibrations on each biome. These calibrations use large database dominated by forest samples. The Mongolian plateau is especially characterized by low annual precipitation and continental annual air temperature. The characterization of the climate system of this area is crucial for the understanding of Holocene Monsoon Oscillations. This study focuses on the calibration of proxy-climate relationships for pollen and glycerol dialkyl glycerol tetraethers (GDGTs) by comparing large published Eurasian calibrations with a set of 49 new surface samples (moss polster, soil and mud from temporary dry pond). These calibrations are then cross-validated by an independent dataset of top-core samples and applied to two Late Holocene paleosequences in the Altai mountains and the Qaidam basin. We show that: (1) preserved pollen assemblages are clearly imprinted on the extremities of the ecosystem range but mitigated and unclear on the ecotones; (2) for both proxies, inferred relationships depend on the geographical range covered by the calibration database as well as on the nature of samples; (3) even if local calibrations suffer from reduced amplitude of climatic parameter due to local homogeneity, they better reflect actual climate than the global ones by reducing the limits for saturation impact, (4) a bias in climatic reconstructions is induced by the over-parameterization of the models and (5) paleoclimate values reconstructed here are consistent with Mongolia-China Late Holocene climate trends, and validate the application of local calibrations for both pollen and GDGTs. We encourage the application of this surface calibration method to reconstruct paleoclimate and especially consolidate our understanding of the Holocene climate and environment variations in Arid Central Asia.
How to cite: Dugerdil, L., Joannin, S., Peyron, O., Jouffroy-Bapicot, I., Vannière, B., Bazartseren, B., Unkelbach, J., Behling, H., and Ménot, G.: Mongolian dryland paleoenvironment and paleoclimate issues : calibrations and applicability of GDGT and pollen reconstructions over the Late Holocene., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3390, https://doi.org/10.5194/egusphere-egu21-3390, 2021.
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Our understanding of climate changes throughout the Holocene is hampered by representativeness in sedimentary archives. Potential production and preservation biases of the markers are identified by comparing these proxies with modern environments. It is important to conduct robust calibrations on each biome. These calibrations use large database dominated by forest samples. The Mongolian plateau is especially characterized by low annual precipitation and continental annual air temperature. The characterization of the climate system of this area is crucial for the understanding of Holocene Monsoon Oscillations. This study focuses on the calibration of proxy-climate relationships for pollen and glycerol dialkyl glycerol tetraethers (GDGTs) by comparing large published Eurasian calibrations with a set of 49 new surface samples (moss polster, soil and mud from temporary dry pond). These calibrations are then cross-validated by an independent dataset of top-core samples and applied to two Late Holocene paleosequences in the Altai mountains and the Qaidam basin. We show that: (1) preserved pollen assemblages are clearly imprinted on the extremities of the ecosystem range but mitigated and unclear on the ecotones; (2) for both proxies, inferred relationships depend on the geographical range covered by the calibration database as well as on the nature of samples; (3) even if local calibrations suffer from reduced amplitude of climatic parameter due to local homogeneity, they better reflect actual climate than the global ones by reducing the limits for saturation impact, (4) a bias in climatic reconstructions is induced by the over-parameterization of the models and (5) paleoclimate values reconstructed here are consistent with Mongolia-China Late Holocene climate trends, and validate the application of local calibrations for both pollen and GDGTs. We encourage the application of this surface calibration method to reconstruct paleoclimate and especially consolidate our understanding of the Holocene climate and environment variations in Arid Central Asia.
How to cite: Dugerdil, L., Joannin, S., Peyron, O., Jouffroy-Bapicot, I., Vannière, B., Bazartseren, B., Unkelbach, J., Behling, H., and Ménot, G.: Mongolian dryland paleoenvironment and paleoclimate issues : calibrations and applicability of GDGT and pollen reconstructions over the Late Holocene., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3390, https://doi.org/10.5194/egusphere-egu21-3390, 2021.
EGU21-16409 | vPICO presentations | GM8.2
Former humid phases in the southwestern Arabian peninsula: climatic and environmental implications of the tufa record over the last 250 ka from the Harrat Al Birk, Saudi Arabia.Abi Stone, Diana Sahy, Robyn Inglis, Ian Candy, Abdullah Alsharekh, and Anthony Sinclair
Little is known about the tufa deposits within the volcanic Harrats of western Saudi Arabia. This research aims to characterise the fossil tufa system and examine its utility as a palaeoenvironmental archive. This requires us to understand the conditions under which the tufa was deposited. In particular, to ascertain whether they are cool, freshwater tufa, or geothermal travertine. In this presentation we show the extent of the tufa within the basin, describe the stratigraphy and settings, as well as their composition and petrology, alongside U-Th chronological control for a selection of suitable subsamples
The samples are composed of low-Mg calcium-carbonate and their 87Sr/86Sr composition shows there has been water-rock interaction with the mafic metavolcanic Neoproterzoic bedrock as well as metamorphosed marine carbonates from the Arabian Escarpment at the head of the Wadi Dabsa catchment. Their δ13C composition (-6.3 to -12.9 ‰) is indicative of a meteoric water and soil signature, rather than a geothermal source.
The tufa deposits are widespread within the Wadi Dabsa Basin, with at least three phases of deposition, recorded at the basin surface, within incised wadi channels and in a downstream fan region. In some locations, the size of tufa-cemented fluvial bedload represents very high magnitude events, whilst the lacustrine to paludal facies indicate more quiescent phases of increased moisture availability. The U-Th dating indicates that the basin was wet during interglacial stages (Marine Oxygen Isotope Stags [MIS] 7 and 5) with some indication, given the error ranges on dates from multiple-subsamples, that deposition occurred primarily during interstadials (e.g. MIS 5e, 5c and 5a). The MIS 7 age is from a vug-fill tufa deposits within an extensive tufa cascade, which indicates the cascade itself pre-dates MIS 7.
The major concentration of artefacts (> 3000) in this basin make it one of the richest Palaeolithic assemblages so far recorded in southwest Saudi Arabia (Foulds et al., 2015; Inglis et al., 2019). This site is ~ 6 km from the current coastline, which is inland from the MIS 5e shorelines in this region (Inglis, pers comm), and these sites with freshwater mean it is important to continue to consider coastal sites as corridors with habitable landscapes for hominins.
References
Foulds, F., A. Shuttleworth, A. Sinclair, A. M. Alsharekh, S. Al Ghamdi, R. H. Inglis, G.N. Bailey (2017) A large handaxe from Wadi Dabsa and early hominin adaptations within the Arabian Peninsula. Antiquity. 91:1421–1434.
Inglis, R. H., Fanning, P. C., Stone, A., Barford, D. N., Sinclair, A., Hsing-Chung, C., Alsharekh, A., Bailey, G. (2019). Palaeolithic artefact deposits at Wadi Dabsa, Saudi Arabia: A multi-scalar geoarchaeological approach to building an interpretive framework. Geoarchaeology 34(3), 272-294.
How to cite: Stone, A., Sahy, D., Inglis, R., Candy, I., Alsharekh, A., and Sinclair, A.: Former humid phases in the southwestern Arabian peninsula: climatic and environmental implications of the tufa record over the last 250 ka from the Harrat Al Birk, Saudi Arabia. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16409, https://doi.org/10.5194/egusphere-egu21-16409, 2021.
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Little is known about the tufa deposits within the volcanic Harrats of western Saudi Arabia. This research aims to characterise the fossil tufa system and examine its utility as a palaeoenvironmental archive. This requires us to understand the conditions under which the tufa was deposited. In particular, to ascertain whether they are cool, freshwater tufa, or geothermal travertine. In this presentation we show the extent of the tufa within the basin, describe the stratigraphy and settings, as well as their composition and petrology, alongside U-Th chronological control for a selection of suitable subsamples
The samples are composed of low-Mg calcium-carbonate and their 87Sr/86Sr composition shows there has been water-rock interaction with the mafic metavolcanic Neoproterzoic bedrock as well as metamorphosed marine carbonates from the Arabian Escarpment at the head of the Wadi Dabsa catchment. Their δ13C composition (-6.3 to -12.9 ‰) is indicative of a meteoric water and soil signature, rather than a geothermal source.
The tufa deposits are widespread within the Wadi Dabsa Basin, with at least three phases of deposition, recorded at the basin surface, within incised wadi channels and in a downstream fan region. In some locations, the size of tufa-cemented fluvial bedload represents very high magnitude events, whilst the lacustrine to paludal facies indicate more quiescent phases of increased moisture availability. The U-Th dating indicates that the basin was wet during interglacial stages (Marine Oxygen Isotope Stags [MIS] 7 and 5) with some indication, given the error ranges on dates from multiple-subsamples, that deposition occurred primarily during interstadials (e.g. MIS 5e, 5c and 5a). The MIS 7 age is from a vug-fill tufa deposits within an extensive tufa cascade, which indicates the cascade itself pre-dates MIS 7.
The major concentration of artefacts (> 3000) in this basin make it one of the richest Palaeolithic assemblages so far recorded in southwest Saudi Arabia (Foulds et al., 2015; Inglis et al., 2019). This site is ~ 6 km from the current coastline, which is inland from the MIS 5e shorelines in this region (Inglis, pers comm), and these sites with freshwater mean it is important to continue to consider coastal sites as corridors with habitable landscapes for hominins.
References
Foulds, F., A. Shuttleworth, A. Sinclair, A. M. Alsharekh, S. Al Ghamdi, R. H. Inglis, G.N. Bailey (2017) A large handaxe from Wadi Dabsa and early hominin adaptations within the Arabian Peninsula. Antiquity. 91:1421–1434.
Inglis, R. H., Fanning, P. C., Stone, A., Barford, D. N., Sinclair, A., Hsing-Chung, C., Alsharekh, A., Bailey, G. (2019). Palaeolithic artefact deposits at Wadi Dabsa, Saudi Arabia: A multi-scalar geoarchaeological approach to building an interpretive framework. Geoarchaeology 34(3), 272-294.
How to cite: Stone, A., Sahy, D., Inglis, R., Candy, I., Alsharekh, A., and Sinclair, A.: Former humid phases in the southwestern Arabian peninsula: climatic and environmental implications of the tufa record over the last 250 ka from the Harrat Al Birk, Saudi Arabia. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16409, https://doi.org/10.5194/egusphere-egu21-16409, 2021.
EGU21-3350 | vPICO presentations | GM8.2 | Highlight
Listen to a spectre – the potential role of environmental seismology in desert process researchMichael Dietze
Desert research has a bold track record in deciphering the evolution of landforms. While iconic objects such as inselbergs, yardangs, wadis or dune fields have attracted the attention of scientists for decades and inspired them to develop numerous formation concepts, it is the actual processes, which are suggested to govern their formation, that are usually quite hard to survey as they happen in nature. This amiguitity is due to the often unpredictable, event based, rapid yet episodic nature of their occurrence. While dedicated devices for measuring these processes inevitably exist, they are either confronted with a small spatial footprint (point measurement) or temporal discontinuousity (time lapse data), or even both of these drawbacks. As a consequence, important processes like flash floods, bedload agitation, mass movement on hillslopes, thermal weathering, dune migration rate and mechanism, or averaged information about ground moisture change, substrate rheology, and temperature diffusion can be studied as they happen under natural conditions only in exceptional cases.
Here I summarise recent developments from the field of environmental seismology, an emerging discipline that studies the seismic signals emitted by Earth surface processes, with a focus on existing and potential applications to desert environments. I present seismic approaches to detecting, tracking and quantifying flash floods and the sediment they convey, provide an overview of the capabilites of seismology to survey hillslope activity at the catchment scale, and discuss the potential to monitor surface and subsurface activity at the plot scale. The overarching aim of the contribution is to foster a discussion about potential research questions that could be tackled in future joint (i.e., established and seismic sensor) instrumentation projects.
How to cite: Dietze, M.: Listen to a spectre – the potential role of environmental seismology in desert process research, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3350, https://doi.org/10.5194/egusphere-egu21-3350, 2021.
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Desert research has a bold track record in deciphering the evolution of landforms. While iconic objects such as inselbergs, yardangs, wadis or dune fields have attracted the attention of scientists for decades and inspired them to develop numerous formation concepts, it is the actual processes, which are suggested to govern their formation, that are usually quite hard to survey as they happen in nature. This amiguitity is due to the often unpredictable, event based, rapid yet episodic nature of their occurrence. While dedicated devices for measuring these processes inevitably exist, they are either confronted with a small spatial footprint (point measurement) or temporal discontinuousity (time lapse data), or even both of these drawbacks. As a consequence, important processes like flash floods, bedload agitation, mass movement on hillslopes, thermal weathering, dune migration rate and mechanism, or averaged information about ground moisture change, substrate rheology, and temperature diffusion can be studied as they happen under natural conditions only in exceptional cases.
Here I summarise recent developments from the field of environmental seismology, an emerging discipline that studies the seismic signals emitted by Earth surface processes, with a focus on existing and potential applications to desert environments. I present seismic approaches to detecting, tracking and quantifying flash floods and the sediment they convey, provide an overview of the capabilites of seismology to survey hillslope activity at the catchment scale, and discuss the potential to monitor surface and subsurface activity at the plot scale. The overarching aim of the contribution is to foster a discussion about potential research questions that could be tackled in future joint (i.e., established and seismic sensor) instrumentation projects.
How to cite: Dietze, M.: Listen to a spectre – the potential role of environmental seismology in desert process research, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3350, https://doi.org/10.5194/egusphere-egu21-3350, 2021.
EGU21-7788 | vPICO presentations | GM8.2
The climatic, topographic and litho-tectonic characteristics of badlands in TurkeyAydogan Avcioglu, Tolga Gorum, Abdullah Akbas, Mariano Moreno de las Heras, and Omer Yetemen
Badland areas are present in all continents, excluding Antarctica, and play a critical role in establishing local erosion and sedimentation rates. The presence of unconsolidated rocks (e.g., marls, sandstone, mudstone etc.) is a major driver controlling the distribution of badlands, which together with other environmental components, such as climate, tectonics, vegetation, and topography, determine their forms and processes. The mutual interaction of controlling factors in badlands areas provides a basis for developing a holistic approach to clarify their distribution patterns. Turkey's geodynamic evolution has led to the emergence of marine sedimentary rocks, pyroclastics, and continental clastics, especially in line with the uplift of the Anatolian Plateau and volcanism during the last 8 Ma.
This study aims to explore the country-scale distribution of badlands and the controlling factors of this badland distribution in Turkey. Remarkably wide badlands landscapes (4494 km2) have been visually inspected using Google Earth ProTM to further digitize and extract geomorphological units by applying high-resolution multispectral images provided by WorldView-4/Maxar Technology and CNES/Airbus. To obtain exact boundaries, we eliminated contiguous flat areas surrounding the identified badlands by using red relief image map (RRIM) mosaics that express surface concavity and convexity combined with topographic slope derived from a digital elevation model of 5-m spatial resolution. Last, to determine the controlling factors of badlands distribution, we have compiled a global data set comprising 1-km resolution layers of mean annual precipitation, temperature and precipitation seasonality, aridity, NDVI, rainfall erosivity factor, elevation, and majority values of regional lithology in sub-catchments units. The enhanced investigation of the complex relationship that expresses the controlling factors of badlands distribution, has been conducted by K-means unsupervised cluster analysis.
Our comprehensive regional analyses exploring the distribution and environmental attributes of major Turkish badlands identified five different groups or clusters of badlands that display spatial coherence with climatic and tectonic settings. We argue that Turkey's climatic and topographic transition zones, varying from Mediterranean climate dominated areas to the more arid Central Anatolian Plateau, and tectonically‑induced topographic barriers play a relevant role in discriminating these groups of badlands. Moreover, the Anatolian diversity of sedimentary rocks, which consists of Neogene and Paleogene continental clastics, volcano clastics & pyroclastics, and lacustrine deposits, makes an essential contribution to the identified, extensive badland distribution.
This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329. The financial support received from TUBITAK does not mean that the content of the publication is approved in a scientific sense by TUBITAK.
How to cite: Avcioglu, A., Gorum, T., Akbas, A., Moreno de las Heras, M., and Yetemen, O.: The climatic, topographic and litho-tectonic characteristics of badlands in Turkey, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7788, https://doi.org/10.5194/egusphere-egu21-7788, 2021.
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Badland areas are present in all continents, excluding Antarctica, and play a critical role in establishing local erosion and sedimentation rates. The presence of unconsolidated rocks (e.g., marls, sandstone, mudstone etc.) is a major driver controlling the distribution of badlands, which together with other environmental components, such as climate, tectonics, vegetation, and topography, determine their forms and processes. The mutual interaction of controlling factors in badlands areas provides a basis for developing a holistic approach to clarify their distribution patterns. Turkey's geodynamic evolution has led to the emergence of marine sedimentary rocks, pyroclastics, and continental clastics, especially in line with the uplift of the Anatolian Plateau and volcanism during the last 8 Ma.
This study aims to explore the country-scale distribution of badlands and the controlling factors of this badland distribution in Turkey. Remarkably wide badlands landscapes (4494 km2) have been visually inspected using Google Earth ProTM to further digitize and extract geomorphological units by applying high-resolution multispectral images provided by WorldView-4/Maxar Technology and CNES/Airbus. To obtain exact boundaries, we eliminated contiguous flat areas surrounding the identified badlands by using red relief image map (RRIM) mosaics that express surface concavity and convexity combined with topographic slope derived from a digital elevation model of 5-m spatial resolution. Last, to determine the controlling factors of badlands distribution, we have compiled a global data set comprising 1-km resolution layers of mean annual precipitation, temperature and precipitation seasonality, aridity, NDVI, rainfall erosivity factor, elevation, and majority values of regional lithology in sub-catchments units. The enhanced investigation of the complex relationship that expresses the controlling factors of badlands distribution, has been conducted by K-means unsupervised cluster analysis.
Our comprehensive regional analyses exploring the distribution and environmental attributes of major Turkish badlands identified five different groups or clusters of badlands that display spatial coherence with climatic and tectonic settings. We argue that Turkey's climatic and topographic transition zones, varying from Mediterranean climate dominated areas to the more arid Central Anatolian Plateau, and tectonically‑induced topographic barriers play a relevant role in discriminating these groups of badlands. Moreover, the Anatolian diversity of sedimentary rocks, which consists of Neogene and Paleogene continental clastics, volcano clastics & pyroclastics, and lacustrine deposits, makes an essential contribution to the identified, extensive badland distribution.
This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329. The financial support received from TUBITAK does not mean that the content of the publication is approved in a scientific sense by TUBITAK.
How to cite: Avcioglu, A., Gorum, T., Akbas, A., Moreno de las Heras, M., and Yetemen, O.: The climatic, topographic and litho-tectonic characteristics of badlands in Turkey, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7788, https://doi.org/10.5194/egusphere-egu21-7788, 2021.
GM9.12 – Interactions between tectonics, climate and surface processes from mountain belts to basins
EGU21-233 | vPICO presentations | GM9.12 | Highlight
Megathrust shear force limits mountain height at convergent plate marginsArmin Dielforder
The shear force along convergent plate boundary faults, called megathrusts, determines the height of mountain ranges that can be mechanically sustained. However, whether the true height of mountain ranges corresponds to this tectonically supported elevation is debated. In particular, climate-dependent erosional processes are often assumed to exert a first-order control on mountain height, although this assumption has remained difficult to validate. To address this issue, I first constrained the shear force along active megathrusts from their rheological properties and then determined the tectonically supported elevation using a force balance model. This analysis revealed that the height of mountain ranges around the globe matches the tectonically supported elevation, irrespective of climatic conditions and the rate of erosion. This finding indicates that the height of mountain ranges is effectively limited by the megathrust shear force and implies that global differences in mountain height are at first-order tectonically controlled. Thus, temporal variations in mountain height should reflect long-term changes in the force balance rather than changes in climate.
How to cite: Dielforder, A.: Megathrust shear force limits mountain height at convergent plate margins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-233, https://doi.org/10.5194/egusphere-egu21-233, 2021.
The shear force along convergent plate boundary faults, called megathrusts, determines the height of mountain ranges that can be mechanically sustained. However, whether the true height of mountain ranges corresponds to this tectonically supported elevation is debated. In particular, climate-dependent erosional processes are often assumed to exert a first-order control on mountain height, although this assumption has remained difficult to validate. To address this issue, I first constrained the shear force along active megathrusts from their rheological properties and then determined the tectonically supported elevation using a force balance model. This analysis revealed that the height of mountain ranges around the globe matches the tectonically supported elevation, irrespective of climatic conditions and the rate of erosion. This finding indicates that the height of mountain ranges is effectively limited by the megathrust shear force and implies that global differences in mountain height are at first-order tectonically controlled. Thus, temporal variations in mountain height should reflect long-term changes in the force balance rather than changes in climate.
How to cite: Dielforder, A.: Megathrust shear force limits mountain height at convergent plate margins, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-233, https://doi.org/10.5194/egusphere-egu21-233, 2021.
EGU21-8243 | vPICO presentations | GM9.12
Surface processes control on orogenic evolution: inferences from 3D coupled numerical models and observations from the India-Eurasia collision zoneLuuk van Agtmaal, Attila Balazs, Dave May, and Taras Gerya
The inherent links between tectonics, surface processes and climatic variations have long since been recognised as the main drivers for the evolution of orogens. Oceanic and continental subduction and collision processes lead to distinct topographic signals. Simultaneously, different climatic forcing factors and denudation rates substantially modify the style of deformation leading to different stress and thermal fields, strain localisation and even deep mantle evolution. An ideal area where the above-mentioned processes and their connections can be studied is the India-Eurasia collision zone.
Understanding the complex interplay between tectonics, erosion, sediment transportation and deposition requires the coupled application of thermo-mechanical and surface processes modelling techniques. To this aim, we used a 3D coupled numerical modelling approach. The influence of different plate convergence, erosion and sedimentation rates has been tested by the thermo-mechanical code I3ELVIS (Gerya and Yuen, 2007) coupled to the diffusion-advection based (FDSPM) surface processes model.
We show preliminary results to demonstrate that the diffusion-advection erosion implementation has significant effects on local and regional mass redistribution and topographic evolution within narrow, curved, high orogens such as the Himalayas and their syntaxes, where erosion is a dominant forcing factor. We also discuss possible implications from different erosion/sedimentation implementations such as DAC (Ueda et al., 2015; Goren et al., 2014) in combination with the reference thermo-mechanical model to analyse changes in orogenic development as a consequence of different erosional processes in more detail.
References:
Gerya, T. V., & Yuen, D. A. (2007). Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems. Physics of the Earth and Planetary Interiors, 163(1-4), 83-105.
Ueda, K., Willett, S. D., Gerya, T., & Ruh, J. (2015). Geomorphological–thermo-mechanical modeling: Application to orogenic wedge dynamics. Tectonophysics, 659, 12-30.
Goren, L., Willett, S. D., Herman, F., & Braun, J. (2014). Coupled numerical–analytical approach to landscape evolution modeling. Earth Surface Processes and Landforms, 39(4), 522-545.
How to cite: van Agtmaal, L., Balazs, A., May, D., and Gerya, T.: Surface processes control on orogenic evolution: inferences from 3D coupled numerical models and observations from the India-Eurasia collision zone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8243, https://doi.org/10.5194/egusphere-egu21-8243, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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The inherent links between tectonics, surface processes and climatic variations have long since been recognised as the main drivers for the evolution of orogens. Oceanic and continental subduction and collision processes lead to distinct topographic signals. Simultaneously, different climatic forcing factors and denudation rates substantially modify the style of deformation leading to different stress and thermal fields, strain localisation and even deep mantle evolution. An ideal area where the above-mentioned processes and their connections can be studied is the India-Eurasia collision zone.
Understanding the complex interplay between tectonics, erosion, sediment transportation and deposition requires the coupled application of thermo-mechanical and surface processes modelling techniques. To this aim, we used a 3D coupled numerical modelling approach. The influence of different plate convergence, erosion and sedimentation rates has been tested by the thermo-mechanical code I3ELVIS (Gerya and Yuen, 2007) coupled to the diffusion-advection based (FDSPM) surface processes model.
We show preliminary results to demonstrate that the diffusion-advection erosion implementation has significant effects on local and regional mass redistribution and topographic evolution within narrow, curved, high orogens such as the Himalayas and their syntaxes, where erosion is a dominant forcing factor. We also discuss possible implications from different erosion/sedimentation implementations such as DAC (Ueda et al., 2015; Goren et al., 2014) in combination with the reference thermo-mechanical model to analyse changes in orogenic development as a consequence of different erosional processes in more detail.
References:
Gerya, T. V., & Yuen, D. A. (2007). Robust characteristics method for modelling multiphase visco-elasto-plastic thermo-mechanical problems. Physics of the Earth and Planetary Interiors, 163(1-4), 83-105.
Ueda, K., Willett, S. D., Gerya, T., & Ruh, J. (2015). Geomorphological–thermo-mechanical modeling: Application to orogenic wedge dynamics. Tectonophysics, 659, 12-30.
Goren, L., Willett, S. D., Herman, F., & Braun, J. (2014). Coupled numerical–analytical approach to landscape evolution modeling. Earth Surface Processes and Landforms, 39(4), 522-545.
How to cite: van Agtmaal, L., Balazs, A., May, D., and Gerya, T.: Surface processes control on orogenic evolution: inferences from 3D coupled numerical models and observations from the India-Eurasia collision zone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8243, https://doi.org/10.5194/egusphere-egu21-8243, 2021.
EGU21-16009 | vPICO presentations | GM9.12
The (un)balance between tectonic and erosion in analog accretionary wedgesRiccardo Reitano, Claudio Faccenna, Francesca Funiciello, Fabio Corbi, Pietro Sternai, Sean D. Willett, Riccardo Lanari, and Andrea Sembroni
In convergent systems, tectonics, erosion, and sedimentation control orogenic evolution. The nature of the interaction between these factors is still to be unraveled, because of their complex feedback that goes through different time and spatial scales. Here, we try to bind tectonics, erosion, and sedimentation by running laboratory-scale coupled analog models of landscape evolution, in which both tectonic forcing and surface processes are modeled, trying to unravel the nature of these multiple-interrelated processes. The analog apparatus consists of a rectangular box filled with a water-saturated granular material. The deformation is imposed by the movement of a rigid piston (backstop), while surface processes are triggered by simulated rainfall and runoff. We systematically vary the convergence velocity and the rainfall rate, testing how different boundary conditions affect the balance between tectonics and surface processes and the onset of steady-state configurations. We measure the competition between input fluxes (tectonics) and output fluxes (erosion) of material. The results show how analog models never achieve a steady-state configuration in which tectonic rates are perfectly balanced by erosion rates. Tectonics add more material to the accretionary wedge than is removed by erosion (about 2-5 times more). Still, erosional fluxes seem to reach an equilibrium with the applied tectonic flux. The foreland is always overfilled with sediments, and we argued how the storage of sediments in front of a wedge can strongly divert the orogenic system from the “classical” steady state configuration. This work analyzes which are the main differences between analog and theoretical models and if/how the results coming from analog models can be exportable when interpreting natural landscape morphologies and force balance.
How to cite: Reitano, R., Faccenna, C., Funiciello, F., Corbi, F., Sternai, P., Willett, S. D., Lanari, R., and Sembroni, A.: The (un)balance between tectonic and erosion in analog accretionary wedges, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16009, https://doi.org/10.5194/egusphere-egu21-16009, 2021.
In convergent systems, tectonics, erosion, and sedimentation control orogenic evolution. The nature of the interaction between these factors is still to be unraveled, because of their complex feedback that goes through different time and spatial scales. Here, we try to bind tectonics, erosion, and sedimentation by running laboratory-scale coupled analog models of landscape evolution, in which both tectonic forcing and surface processes are modeled, trying to unravel the nature of these multiple-interrelated processes. The analog apparatus consists of a rectangular box filled with a water-saturated granular material. The deformation is imposed by the movement of a rigid piston (backstop), while surface processes are triggered by simulated rainfall and runoff. We systematically vary the convergence velocity and the rainfall rate, testing how different boundary conditions affect the balance between tectonics and surface processes and the onset of steady-state configurations. We measure the competition between input fluxes (tectonics) and output fluxes (erosion) of material. The results show how analog models never achieve a steady-state configuration in which tectonic rates are perfectly balanced by erosion rates. Tectonics add more material to the accretionary wedge than is removed by erosion (about 2-5 times more). Still, erosional fluxes seem to reach an equilibrium with the applied tectonic flux. The foreland is always overfilled with sediments, and we argued how the storage of sediments in front of a wedge can strongly divert the orogenic system from the “classical” steady state configuration. This work analyzes which are the main differences between analog and theoretical models and if/how the results coming from analog models can be exportable when interpreting natural landscape morphologies and force balance.
How to cite: Reitano, R., Faccenna, C., Funiciello, F., Corbi, F., Sternai, P., Willett, S. D., Lanari, R., and Sembroni, A.: The (un)balance between tectonic and erosion in analog accretionary wedges, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16009, https://doi.org/10.5194/egusphere-egu21-16009, 2021.
EGU21-15983 | vPICO presentations | GM9.12
Stable isotope composition of fluid inclusions in quartz minerals : New method for paleoaltimetryRaphaël Melis, Véronique Gardien, Gweltaz Mahéo, Christophe Lécuyer, Philippe-Hervé Leloup, Patrick Jame, and Eric Bonjour
Paleoaltimetry is a powerful tool to study tectonic, climate and surface processes interactions. Indeed, stable isotope composition of meteoric water can be correlated with the elevation of reliefs. The δ18O and δD of orogenic rainfall decrease while the elevation increase. Current paleoaltimetric methods based on stable isotope, including the study of pedogenic carbonates and micas associated with fault or shear zones, represent an indirect way to obtain stable isotope « paleometeoric fluid » composition. These methods do not provide simultaneously the δ18O and δD values implying the use of isotope exchange equation, source of signficant errors (up to +/- 1000m).
We have developed a new method which allow to directly acces at both the δ18O and δD of « paleometeoric » fluids with a good precision and margin of error less than +/- 200m . This method has been developed on the stable isotope composition of fluid inclusion trapped in quartz veins. The developed experimental protocol allows to extract small quantity of fluid (~10mL) and directly analyse both the δ18O and δD with a OA-ICOS Spectroscopy. Tested on 18 Miocene alpine quartz veins from the Mont-Blanc and the Chenaillet massifs the stable isotope composition of the fluids fit very well with meteoric isotopic signature and highlight the robustness of stable isotope ratio through geological time.
More over, our results indicate that Miocene precipitation was way more positive (-4,8 to -9 ‰ for δ18O and -38,2 to 68,8‰ for δD) in the Mont-Blanc massif area than modern precipitation (-12,9 to -18 ‰ for δ18O and -101,1 to -144,25‰ for δD) which indicate that the massif was still at low elevation at this time. In contrast the « paleoprecipitation » of the Chenaillet massif fall in the same range than modern precipitation (-83 to -120,3 ‰ for δD and -11,8 to -16,9 ‰ for δ18O) which indicate this massif has already reached his present altitude (~ 2500m).
How to cite: Melis, R., Gardien, V., Mahéo, G., Lécuyer, C., Leloup, P.-H., Jame, P., and Bonjour, E.: Stable isotope composition of fluid inclusions in quartz minerals : New method for paleoaltimetry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15983, https://doi.org/10.5194/egusphere-egu21-15983, 2021.
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Paleoaltimetry is a powerful tool to study tectonic, climate and surface processes interactions. Indeed, stable isotope composition of meteoric water can be correlated with the elevation of reliefs. The δ18O and δD of orogenic rainfall decrease while the elevation increase. Current paleoaltimetric methods based on stable isotope, including the study of pedogenic carbonates and micas associated with fault or shear zones, represent an indirect way to obtain stable isotope « paleometeoric fluid » composition. These methods do not provide simultaneously the δ18O and δD values implying the use of isotope exchange equation, source of signficant errors (up to +/- 1000m).
We have developed a new method which allow to directly acces at both the δ18O and δD of « paleometeoric » fluids with a good precision and margin of error less than +/- 200m . This method has been developed on the stable isotope composition of fluid inclusion trapped in quartz veins. The developed experimental protocol allows to extract small quantity of fluid (~10mL) and directly analyse both the δ18O and δD with a OA-ICOS Spectroscopy. Tested on 18 Miocene alpine quartz veins from the Mont-Blanc and the Chenaillet massifs the stable isotope composition of the fluids fit very well with meteoric isotopic signature and highlight the robustness of stable isotope ratio through geological time.
More over, our results indicate that Miocene precipitation was way more positive (-4,8 to -9 ‰ for δ18O and -38,2 to 68,8‰ for δD) in the Mont-Blanc massif area than modern precipitation (-12,9 to -18 ‰ for δ18O and -101,1 to -144,25‰ for δD) which indicate that the massif was still at low elevation at this time. In contrast the « paleoprecipitation » of the Chenaillet massif fall in the same range than modern precipitation (-83 to -120,3 ‰ for δD and -11,8 to -16,9 ‰ for δ18O) which indicate this massif has already reached his present altitude (~ 2500m).
How to cite: Melis, R., Gardien, V., Mahéo, G., Lécuyer, C., Leloup, P.-H., Jame, P., and Bonjour, E.: Stable isotope composition of fluid inclusions in quartz minerals : New method for paleoaltimetry, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15983, https://doi.org/10.5194/egusphere-egu21-15983, 2021.
EGU21-3135 | vPICO presentations | GM9.12
Resolving thermal histories via multi-kinetic apatite fission track data: A case study from Phanerozoic strata within the Peel Plateau NWT, CanadaJennifer Spalding, Jeremy Powell, David Schneider, and Karen Fallas
Resolving the thermal history of sedimentary basins through geological time is essential when evaluating the maturity of source rocks within petroleum systems. Traditional methods used to estimate maximum burial temperatures in prospective sedimentary basin such as and vitrinite reflectance (%Ro) are unable to constrain the timing and duration of thermal events. In comparison, low-temperature thermochronology methods, such as apatite fission track thermochronology (AFT), can resolve detailed thermal histories within a temperature range corresponding to oil and gas generation. In the Peel Plateau of the Northwest Territories, Canada, Phanerozoic sedimentary strata exhibit oil-stained outcrops, gas seeps, and bitumen occurrences. Presently, the timing of hydrocarbon maturation events are poorly constrained, as a regional unconformity at the base of Cretaceous foreland basin strata indicates that underlying Devonian source rocks may have undergone a burial and unroofing event prior to the Cretaceous. Published organic thermal maturity values from wells within the study area range from 1.59 and 2.46 %Ro for Devonian strata and 0.54 and 1.83 %Ro within Lower Cretaceous strata. Herein, we have resolved the thermal history of the Peel Plateau through multi-kinetic AFT thermochronology. Three samples from Upper Devonian, Lower Cretaceous and Upper Cretaceous strata have pooled AFT ages of 61.0 ± 5.1 Ma, 59.5 ± 5.2 and 101.6 ± 6.7 Ma, respectively, and corresponding U-Pb ages of 497.4 ± 17.5 Ma (MSWD: 7.4), 353.5 ± 13.5 Ma (MSWD: 3.1) and 261.2 ± 8.5 Ma (MSWD: 5.9). All AFT data fail the χ2 test, suggesting AFT ages do not comprise a single statistically significant population, whereas U-Pb ages reflect the pre-depositional history of the samples and are likely from various provenances. Apatite chemistry is known to control the temperature and rates at which fission tracks undergo thermal annealing. The rmro parameter uses grain specific chemistry to predict apatite’s kinetic behaviour and is used to identify kinetic populations within samples. Grain chemistry was measured via electron microprobe analysis to derive rmro values and each sample was separated into two kinetic populations that pass the χ2 test: a less retentive population with ages ranging from 49.3 ± 9.3 Ma to 36.4 ± 4.7 Ma, and a more retentive population with ages ranging from 157.7 ± 19 Ma to 103.3 ± 11.8 Ma, with rmr0 benchmarks ranging from 0.79 and 0.82. Thermal history models reveal Devonian strata reached maximum burial temperatures (~165°C-185°C) prior to late Paleozoic to Mesozoic unroofing, and reheated to lower temperatures (~75°C-110°C) in the Late Cretaceous to Paleogene. Both Cretaceous samples record maximum burial temperatures (75°C-95°C) also during the Late Cretaceous to Paleogene. These new data indicate that Devonian source rocks matured prior to deposition of Cretaceous strata and that subsequent burial and heating during the Cretaceous to Paleogene was limited to the low-temperature threshold of the oil window. Integrating multi-kinetic AFT data with traditional methods in petroleum geosciences can help unravel complex thermal histories of sedimentary basins. Applying these methods elsewhere can improve the characterisation of petroleum systems.
How to cite: Spalding, J., Powell, J., Schneider, D., and Fallas, K.: Resolving thermal histories via multi-kinetic apatite fission track data: A case study from Phanerozoic strata within the Peel Plateau NWT, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3135, https://doi.org/10.5194/egusphere-egu21-3135, 2021.
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Resolving the thermal history of sedimentary basins through geological time is essential when evaluating the maturity of source rocks within petroleum systems. Traditional methods used to estimate maximum burial temperatures in prospective sedimentary basin such as and vitrinite reflectance (%Ro) are unable to constrain the timing and duration of thermal events. In comparison, low-temperature thermochronology methods, such as apatite fission track thermochronology (AFT), can resolve detailed thermal histories within a temperature range corresponding to oil and gas generation. In the Peel Plateau of the Northwest Territories, Canada, Phanerozoic sedimentary strata exhibit oil-stained outcrops, gas seeps, and bitumen occurrences. Presently, the timing of hydrocarbon maturation events are poorly constrained, as a regional unconformity at the base of Cretaceous foreland basin strata indicates that underlying Devonian source rocks may have undergone a burial and unroofing event prior to the Cretaceous. Published organic thermal maturity values from wells within the study area range from 1.59 and 2.46 %Ro for Devonian strata and 0.54 and 1.83 %Ro within Lower Cretaceous strata. Herein, we have resolved the thermal history of the Peel Plateau through multi-kinetic AFT thermochronology. Three samples from Upper Devonian, Lower Cretaceous and Upper Cretaceous strata have pooled AFT ages of 61.0 ± 5.1 Ma, 59.5 ± 5.2 and 101.6 ± 6.7 Ma, respectively, and corresponding U-Pb ages of 497.4 ± 17.5 Ma (MSWD: 7.4), 353.5 ± 13.5 Ma (MSWD: 3.1) and 261.2 ± 8.5 Ma (MSWD: 5.9). All AFT data fail the χ2 test, suggesting AFT ages do not comprise a single statistically significant population, whereas U-Pb ages reflect the pre-depositional history of the samples and are likely from various provenances. Apatite chemistry is known to control the temperature and rates at which fission tracks undergo thermal annealing. The rmro parameter uses grain specific chemistry to predict apatite’s kinetic behaviour and is used to identify kinetic populations within samples. Grain chemistry was measured via electron microprobe analysis to derive rmro values and each sample was separated into two kinetic populations that pass the χ2 test: a less retentive population with ages ranging from 49.3 ± 9.3 Ma to 36.4 ± 4.7 Ma, and a more retentive population with ages ranging from 157.7 ± 19 Ma to 103.3 ± 11.8 Ma, with rmr0 benchmarks ranging from 0.79 and 0.82. Thermal history models reveal Devonian strata reached maximum burial temperatures (~165°C-185°C) prior to late Paleozoic to Mesozoic unroofing, and reheated to lower temperatures (~75°C-110°C) in the Late Cretaceous to Paleogene. Both Cretaceous samples record maximum burial temperatures (75°C-95°C) also during the Late Cretaceous to Paleogene. These new data indicate that Devonian source rocks matured prior to deposition of Cretaceous strata and that subsequent burial and heating during the Cretaceous to Paleogene was limited to the low-temperature threshold of the oil window. Integrating multi-kinetic AFT data with traditional methods in petroleum geosciences can help unravel complex thermal histories of sedimentary basins. Applying these methods elsewhere can improve the characterisation of petroleum systems.
How to cite: Spalding, J., Powell, J., Schneider, D., and Fallas, K.: Resolving thermal histories via multi-kinetic apatite fission track data: A case study from Phanerozoic strata within the Peel Plateau NWT, Canada, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3135, https://doi.org/10.5194/egusphere-egu21-3135, 2021.
EGU21-12030 | vPICO presentations | GM9.12
Magnetostratigraphy of the Yili Basin indicates Late Cenozonic activity of the Tianshan Mountain, northwestern ChinaLiu Xiaoyan, Yuan Sihua, Jin Chunsheng, Bai Xiangdong, Jiang Jiyi, Zhao Zhenghong, and Li Ying
The Yili basin, sandwiched in the Northern and Southern Tianshan Mountain, is an ideal area to study the eroded histories at the Northern Tianshan Mountain during the late Cenozoic. Massive works have been done on tectonic deformation and uplift in this region. However, due to the lack of biostratigraphic data and effective dating marks, the uplifting time limit of the Tianshan Mountain are still argued by many researchers. In order to constrain the uplift history in the west Tianshan Mountain and provid the late Cenozoic time scale, we carried out a series of studies in the Chinese Yili Basin, fortunately, we acquired a drilling core with a depth of 500 m in the Quarternary depocenter in this basin, which provides the basis for the relevant studies. These results offered basic geological data for protecting against and mitigating earthquake disasters.
A magnetic stratigraphic study was carried out on the drilling core, combined with three OSL dating data from a natural section adjacent to the drilling hole, an effective time scale was established. There are three main results as follows: (1)The polarity sequences shows 5 normal and 5 reverse polarity zones which can be readily correlated with the Geomagnetic Polarity Time Scale (GPTS2012), dating the core from 3.11Ma to 12Ka. (2) The B/M boundary of magnetic strata in the 500m core in western Yili basin is located in the core 80m and M/G line is located in the core 400m. (3) The sedimentation rate in the western Yili Basin increased rapidly at two periods, ~1.17 to 1.07Ma and ~2.13 to 1.77Ma.
According to the regional reference data, the peak deposition rate in the range of ~ 2.13 to 1.77Ma is closely related to the Xiyu movement in Northwest China, as a corollary, the sedimentation rate should decrease with the end of Xiyu Movement after ~1.77Ma. Another obvious lithofacies change from ~1.17 to 1.07Ma illustrates there should be a tectonic event in the Tian shan region. This Middle Pleistocene uplift can also be evidenced by the age of volcanism in the Qaidam Basin (northeastern Tibetan Plateau), the existence of thick conglomerate deposits surrounding the uplifted plateau, and the increased sedimentation rate of lacustrine deposits in the between ~1.1 and ~0.9Ma ago, followed by the loess and marine records.
How to cite: Xiaoyan, L., Sihua, Y., Chunsheng, J., Xiangdong, B., Jiyi, J., Zhenghong, Z., and Ying, L.: Magnetostratigraphy of the Yili Basin indicates Late Cenozonic activity of the Tianshan Mountain, northwestern China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12030, https://doi.org/10.5194/egusphere-egu21-12030, 2021.
The Yili basin, sandwiched in the Northern and Southern Tianshan Mountain, is an ideal area to study the eroded histories at the Northern Tianshan Mountain during the late Cenozoic. Massive works have been done on tectonic deformation and uplift in this region. However, due to the lack of biostratigraphic data and effective dating marks, the uplifting time limit of the Tianshan Mountain are still argued by many researchers. In order to constrain the uplift history in the west Tianshan Mountain and provid the late Cenozoic time scale, we carried out a series of studies in the Chinese Yili Basin, fortunately, we acquired a drilling core with a depth of 500 m in the Quarternary depocenter in this basin, which provides the basis for the relevant studies. These results offered basic geological data for protecting against and mitigating earthquake disasters.
A magnetic stratigraphic study was carried out on the drilling core, combined with three OSL dating data from a natural section adjacent to the drilling hole, an effective time scale was established. There are three main results as follows: (1)The polarity sequences shows 5 normal and 5 reverse polarity zones which can be readily correlated with the Geomagnetic Polarity Time Scale (GPTS2012), dating the core from 3.11Ma to 12Ka. (2) The B/M boundary of magnetic strata in the 500m core in western Yili basin is located in the core 80m and M/G line is located in the core 400m. (3) The sedimentation rate in the western Yili Basin increased rapidly at two periods, ~1.17 to 1.07Ma and ~2.13 to 1.77Ma.
According to the regional reference data, the peak deposition rate in the range of ~ 2.13 to 1.77Ma is closely related to the Xiyu movement in Northwest China, as a corollary, the sedimentation rate should decrease with the end of Xiyu Movement after ~1.77Ma. Another obvious lithofacies change from ~1.17 to 1.07Ma illustrates there should be a tectonic event in the Tian shan region. This Middle Pleistocene uplift can also be evidenced by the age of volcanism in the Qaidam Basin (northeastern Tibetan Plateau), the existence of thick conglomerate deposits surrounding the uplifted plateau, and the increased sedimentation rate of lacustrine deposits in the between ~1.1 and ~0.9Ma ago, followed by the loess and marine records.
How to cite: Xiaoyan, L., Sihua, Y., Chunsheng, J., Xiangdong, B., Jiyi, J., Zhenghong, Z., and Ying, L.: Magnetostratigraphy of the Yili Basin indicates Late Cenozonic activity of the Tianshan Mountain, northwestern China, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12030, https://doi.org/10.5194/egusphere-egu21-12030, 2021.
EGU21-2145 | vPICO presentations | GM9.12
Late Cenozoic two-phase rapid exhumation of the Daliang Mountains, Southeastern Tibetan PlateauHaijia Lei, Xiaoming Shen, Xijun Liu, Xiudang Tang, and Shiming Zhang
The southeastern Tibetan Plateau experienced significant tectonic uplift, fault activity, climate change and reorgnization of fluvial systems during the late Cenozoic. All these processes were probably accompanied by rapid rock exhumation. Therefore, rock exhumation history in this region could provide a key to reveal the interaction between tectonics, climate and surface processes. Here, we report new apatite and zircon (U-Th)/He dates from a ~1200 m granite vertical profile, located at Shimian county in the Daliang Mountains, southeastern Tibetan Plateau. The age-elevation relationship and thermal history simulation exhibit a two-phase rock exhumation history, one at ~25 Ma (~1 km/Myr) and a second moderate exhumation from ~15 Ma to present (~ 0.2 km/Myr). This two-phase rapid exhumation history is consistent with that of Longmen Shan and Jiulong in the adjacent areas. For the first phase in Oligocene, abundant geological evidence indicates that it was related to the regional uplift caused by the transpressional deformation during India-Asia convergence. However, there are two distinct explanations for the rapid exhumation from ~15 Ma to present: one group suggested this exhumation was related to the rapid river incision caused by regional uplift; By contrast, based on paleo-altimetry data another group proposed the uplift was ceased before the late Miocene in southeastern Tibetan Plateau, and then the enhanced rainfall caused by the East Asian monsoon resulted in rapid exhumation since the Middle Miocene. Our study suggests that the fast exhumation in southeastern Tibetan Plateau since ~15 Ma cannot be attributed solely to the regional uplift or the intensification of Asian monsoon. Combined with the activity history of the Anninghe fault in the study area and the East Asian monsoon evolution history, we suggest that the regional rock exhumation of southeastern Tibetean Plateau since the Middle Miocene could be the result of the combination of tectonic activity and climate change.
How to cite: Lei, H., Shen, X., Liu, X., Tang, X., and Zhang, S.: Late Cenozoic two-phase rapid exhumation of the Daliang Mountains, Southeastern Tibetan Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2145, https://doi.org/10.5194/egusphere-egu21-2145, 2021.
Please decide on your access
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The southeastern Tibetan Plateau experienced significant tectonic uplift, fault activity, climate change and reorgnization of fluvial systems during the late Cenozoic. All these processes were probably accompanied by rapid rock exhumation. Therefore, rock exhumation history in this region could provide a key to reveal the interaction between tectonics, climate and surface processes. Here, we report new apatite and zircon (U-Th)/He dates from a ~1200 m granite vertical profile, located at Shimian county in the Daliang Mountains, southeastern Tibetan Plateau. The age-elevation relationship and thermal history simulation exhibit a two-phase rock exhumation history, one at ~25 Ma (~1 km/Myr) and a second moderate exhumation from ~15 Ma to present (~ 0.2 km/Myr). This two-phase rapid exhumation history is consistent with that of Longmen Shan and Jiulong in the adjacent areas. For the first phase in Oligocene, abundant geological evidence indicates that it was related to the regional uplift caused by the transpressional deformation during India-Asia convergence. However, there are two distinct explanations for the rapid exhumation from ~15 Ma to present: one group suggested this exhumation was related to the rapid river incision caused by regional uplift; By contrast, based on paleo-altimetry data another group proposed the uplift was ceased before the late Miocene in southeastern Tibetan Plateau, and then the enhanced rainfall caused by the East Asian monsoon resulted in rapid exhumation since the Middle Miocene. Our study suggests that the fast exhumation in southeastern Tibetan Plateau since ~15 Ma cannot be attributed solely to the regional uplift or the intensification of Asian monsoon. Combined with the activity history of the Anninghe fault in the study area and the East Asian monsoon evolution history, we suggest that the regional rock exhumation of southeastern Tibetean Plateau since the Middle Miocene could be the result of the combination of tectonic activity and climate change.
How to cite: Lei, H., Shen, X., Liu, X., Tang, X., and Zhang, S.: Late Cenozoic two-phase rapid exhumation of the Daliang Mountains, Southeastern Tibetan Plateau, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2145, https://doi.org/10.5194/egusphere-egu21-2145, 2021.
EGU21-16290 | vPICO presentations | GM9.12
Insights of Spatiotemporal evolution of Yamuna Valley, Garhwal Himalaya: Derived from Fission track dating and Morphotectonic analysisPrerna Gahlaut and Ramesh Chandra Patel
Substantial set of recent documentation with sophisticated statistical and analog models have recognized dynamic interchange between subsurface crustal distortion and exogenic erosional processes as the root of geomorphic evolution of Himalaya. Low temperature thermochronology provides insights to enumerate nature and timing of tectonic course from extracted thermal records of vertical moving rock block over geological past. In present study, we used Apatite fission track technique to calculated exhumation rates of Yamuna valley, Garhwal Himalaya. AFT ages of Lesser Himalaya Sequence of Purola region various between 4.0 ±0.8 myr to 9.5±0.6 myr. While AFT ages of LHS along Yamuna River varies form 2.3±0.5 myr to 5.6±0.6 myr and exhumation rates are 2.3-1.2 mm/yr. calculated age of Apatite sample near Main Central Thrust (MCT) is 2.3±0.5 myr which exhumed at the rate of 2.3 mm/yr. Exhumation rates of Purola region are 0.8-1.6 mm/yr.
To link the exhumation rates with present day morphology we used 2 methods; 1) Calculate morphotectonic parameters of Yamuna River valley; 2) compare our AFT ages and exhumation rates with early studies. Drainage pattern in the tectonically active zone is vigorously susceptible to mechanisms such as folding, faulting and basin tilting. Such deformation processes influence the phase of geomorphology, drainage pattern, river incision, elongation, asymmetry, and diversion. Mathematical quantification of drainage morphology elucidate spatio-temporal effect of tectonics. Morphotectonic parameters are stream length gradient index (SL), valley floor height to width ratio (Vf), asymmetry factor (Af), basin shape index (BS) and hypsometric integral (HI) extracted from SRTM DEM with resolution of 30m and are calculated in ArcGIS 10.3. These parameters further integrated to define a single Indaex of relative Active Tectonic (IRAT). Value of IRAT is very high in upper Yamunotri region and low to moderate in Purola region. The exhumation rates are further compared with erosion rates from early studies. Erosion rates derived from 10Be nuclides (Scherler et al 2014) show very slow erosion rate in Purola region (~ 0.13±0.01 mm/yr) while for Yamunotri region higher erosion rate (>4.9 mm/yr) is recorded. These erosion rates are attributed to subsurface geometry of MCT.
All three approaches together construct an evolution record of study area over geological past. Exhumation history of Apatite and erosion rates from early studies conclude Yamuna river valley, specifically upper region of valley is very active while Purola region is less active. Morphotectonic parameters harmoniously present similar picture. These combined study point toward relegate control of climate and dominance of ongoing sub-surficial deformation along MCT in Yamuna River valley on geological time scale.
How to cite: Gahlaut, P. and Chandra Patel, R.: Insights of Spatiotemporal evolution of Yamuna Valley, Garhwal Himalaya: Derived from Fission track dating and Morphotectonic analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16290, https://doi.org/10.5194/egusphere-egu21-16290, 2021.
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Substantial set of recent documentation with sophisticated statistical and analog models have recognized dynamic interchange between subsurface crustal distortion and exogenic erosional processes as the root of geomorphic evolution of Himalaya. Low temperature thermochronology provides insights to enumerate nature and timing of tectonic course from extracted thermal records of vertical moving rock block over geological past. In present study, we used Apatite fission track technique to calculated exhumation rates of Yamuna valley, Garhwal Himalaya. AFT ages of Lesser Himalaya Sequence of Purola region various between 4.0 ±0.8 myr to 9.5±0.6 myr. While AFT ages of LHS along Yamuna River varies form 2.3±0.5 myr to 5.6±0.6 myr and exhumation rates are 2.3-1.2 mm/yr. calculated age of Apatite sample near Main Central Thrust (MCT) is 2.3±0.5 myr which exhumed at the rate of 2.3 mm/yr. Exhumation rates of Purola region are 0.8-1.6 mm/yr.
To link the exhumation rates with present day morphology we used 2 methods; 1) Calculate morphotectonic parameters of Yamuna River valley; 2) compare our AFT ages and exhumation rates with early studies. Drainage pattern in the tectonically active zone is vigorously susceptible to mechanisms such as folding, faulting and basin tilting. Such deformation processes influence the phase of geomorphology, drainage pattern, river incision, elongation, asymmetry, and diversion. Mathematical quantification of drainage morphology elucidate spatio-temporal effect of tectonics. Morphotectonic parameters are stream length gradient index (SL), valley floor height to width ratio (Vf), asymmetry factor (Af), basin shape index (BS) and hypsometric integral (HI) extracted from SRTM DEM with resolution of 30m and are calculated in ArcGIS 10.3. These parameters further integrated to define a single Indaex of relative Active Tectonic (IRAT). Value of IRAT is very high in upper Yamunotri region and low to moderate in Purola region. The exhumation rates are further compared with erosion rates from early studies. Erosion rates derived from 10Be nuclides (Scherler et al 2014) show very slow erosion rate in Purola region (~ 0.13±0.01 mm/yr) while for Yamunotri region higher erosion rate (>4.9 mm/yr) is recorded. These erosion rates are attributed to subsurface geometry of MCT.
All three approaches together construct an evolution record of study area over geological past. Exhumation history of Apatite and erosion rates from early studies conclude Yamuna river valley, specifically upper region of valley is very active while Purola region is less active. Morphotectonic parameters harmoniously present similar picture. These combined study point toward relegate control of climate and dominance of ongoing sub-surficial deformation along MCT in Yamuna River valley on geological time scale.
How to cite: Gahlaut, P. and Chandra Patel, R.: Insights of Spatiotemporal evolution of Yamuna Valley, Garhwal Himalaya: Derived from Fission track dating and Morphotectonic analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16290, https://doi.org/10.5194/egusphere-egu21-16290, 2021.
EGU21-9121 | vPICO presentations | GM9.12
Topographic response to Neogene variations in slab geometry, climate and drainage reorganization in the Northern Andes of ColombiaNicolas Perez-Consuegra, Richard Ott, Gregory D. Hoke, Jorge Pedro Galve, and Jose Vicente Pérez–Peña
The tropical Northern Andes of Colombia are one the world's most biodiverse places, offering an ideal location for unraveling the linkages between the geodynamic forces that build topography and the evolution of the biota that inhabit it. In this study, we utilize a geomorphic analysis to characterize the topography of the Western and Central Cordilleras of the Northern Andes. We supplement our topographic analysis with erosion rate estimates based on gauged suspended sediment loads and river incision rates from volcanic sequences. In the northern segment of the Central Cordillera, an elevated low-relief surface (2,500m in elevation, ~40x110 km in size) with uniform lithology and surrounded by knickpoints, indicates a recent increase in rock and surface uplift rate. Whereas, the southern segment of the Central Cordillera shows substantially higher local relief and mostly well graded river profiles consistent with longer term uplift stability. These changes in the topography fit with the proposed location of a slab tear and flat slab subduction under the northern Central Cordillera, as well as with a major transition in the channel slope of the Cauca River. We identify several areas of major drainage reorganization, including captures and divide migrations that are supported by our erosion and incision rate estimates. We identify slab flattening as the most likely cause of strong and recent uplift in the Northern Andes leading to ~2 km of surface uplift since 8–4 Ma. Large scale drainage reorganization of major rivers is probably mainly driven by changes in upper plate deformation in relation to development of the flat slab subduction geometry; however, other factors such as climate and emplacement of volcanic rocks likely play secondary roles in this process. Several isolated biologic observations above the area of slab flattening suggest that surface uplift isolated former lowland species on the high elevation plateaus, and drainage reorganization may have driven diversification of aquatic species.
How to cite: Perez-Consuegra, N., Ott, R., Hoke, G. D., Galve, J. P., and Pérez–Peña, J. V.: Topographic response to Neogene variations in slab geometry, climate and drainage reorganization in the Northern Andes of Colombia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9121, https://doi.org/10.5194/egusphere-egu21-9121, 2021.
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The tropical Northern Andes of Colombia are one the world's most biodiverse places, offering an ideal location for unraveling the linkages between the geodynamic forces that build topography and the evolution of the biota that inhabit it. In this study, we utilize a geomorphic analysis to characterize the topography of the Western and Central Cordilleras of the Northern Andes. We supplement our topographic analysis with erosion rate estimates based on gauged suspended sediment loads and river incision rates from volcanic sequences. In the northern segment of the Central Cordillera, an elevated low-relief surface (2,500m in elevation, ~40x110 km in size) with uniform lithology and surrounded by knickpoints, indicates a recent increase in rock and surface uplift rate. Whereas, the southern segment of the Central Cordillera shows substantially higher local relief and mostly well graded river profiles consistent with longer term uplift stability. These changes in the topography fit with the proposed location of a slab tear and flat slab subduction under the northern Central Cordillera, as well as with a major transition in the channel slope of the Cauca River. We identify several areas of major drainage reorganization, including captures and divide migrations that are supported by our erosion and incision rate estimates. We identify slab flattening as the most likely cause of strong and recent uplift in the Northern Andes leading to ~2 km of surface uplift since 8–4 Ma. Large scale drainage reorganization of major rivers is probably mainly driven by changes in upper plate deformation in relation to development of the flat slab subduction geometry; however, other factors such as climate and emplacement of volcanic rocks likely play secondary roles in this process. Several isolated biologic observations above the area of slab flattening suggest that surface uplift isolated former lowland species on the high elevation plateaus, and drainage reorganization may have driven diversification of aquatic species.
How to cite: Perez-Consuegra, N., Ott, R., Hoke, G. D., Galve, J. P., and Pérez–Peña, J. V.: Topographic response to Neogene variations in slab geometry, climate and drainage reorganization in the Northern Andes of Colombia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9121, https://doi.org/10.5194/egusphere-egu21-9121, 2021.
EGU21-3520 | vPICO presentations | GM9.12
Evaluating the influence of erosion and tectonic processes on California’s topography by measuring its fractal dimension and anisotropy across scalesHervé Guillon, Belize Lane, Colin F. Byrne, Gregory B. Pasternack, and Samuel Sandoval Solis
Roughness is paramount in Earth sciences, and landscapes, laboratory alluvial fans, river bed elevation, bedload transport and the friction laws of fluid mechanics all exhibit a fractal behavior described by a scale-persistent roughness. Yet, for a given landscape, the exact meaning of statistical roughness, or fractal dimension, remains unclear. The fractal dimension of topography is mainly understood as two end-members: at large spatial scales, it describes tectonic processes; at small spatial scales it describes erosion processes. In this study, we nuance this description by identifying the spatial scale at which erosion processes are inadequately described by fractal dimension and provide quantitative bounds on the meaning of the statistical roughness of topography at scales from 0.25 km to 100 km using three lines of evidence. First, we leverage spatial statistics to evaluate the auto-correlation structure of topographic statistical roughness across the physiographically diverse state of California, USA. Second, we identify the down-slope and across-slope directions using two-dimensional Fourier analysis, and measure the anisotropy of topography by evaluating statistical roughness in each direction. Third, we perform a spatial correlation analysis between statistical roughness and the Péclet number which describes the balance between diffusion and incision processes. Our preliminary results indicate that correlation between statistical roughness and Péclet number fades at scales greater than 4.6 km. In addition, auto-correlation saturation occurs for statistical roughness at scales greater than 16.5 km. Hence our analysis provides a more nuanced description of the statistical roughness of topography: it represents erosion processes at scales up to 4.6 km while being dominated by tectonics at scales greater than 16.5 km.
How to cite: Guillon, H., Lane, B., Byrne, C. F., Pasternack, G. B., and Sandoval Solis, S.: Evaluating the influence of erosion and tectonic processes on California’s topography by measuring its fractal dimension and anisotropy across scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3520, https://doi.org/10.5194/egusphere-egu21-3520, 2021.
Roughness is paramount in Earth sciences, and landscapes, laboratory alluvial fans, river bed elevation, bedload transport and the friction laws of fluid mechanics all exhibit a fractal behavior described by a scale-persistent roughness. Yet, for a given landscape, the exact meaning of statistical roughness, or fractal dimension, remains unclear. The fractal dimension of topography is mainly understood as two end-members: at large spatial scales, it describes tectonic processes; at small spatial scales it describes erosion processes. In this study, we nuance this description by identifying the spatial scale at which erosion processes are inadequately described by fractal dimension and provide quantitative bounds on the meaning of the statistical roughness of topography at scales from 0.25 km to 100 km using three lines of evidence. First, we leverage spatial statistics to evaluate the auto-correlation structure of topographic statistical roughness across the physiographically diverse state of California, USA. Second, we identify the down-slope and across-slope directions using two-dimensional Fourier analysis, and measure the anisotropy of topography by evaluating statistical roughness in each direction. Third, we perform a spatial correlation analysis between statistical roughness and the Péclet number which describes the balance between diffusion and incision processes. Our preliminary results indicate that correlation between statistical roughness and Péclet number fades at scales greater than 4.6 km. In addition, auto-correlation saturation occurs for statistical roughness at scales greater than 16.5 km. Hence our analysis provides a more nuanced description of the statistical roughness of topography: it represents erosion processes at scales up to 4.6 km while being dominated by tectonics at scales greater than 16.5 km.
How to cite: Guillon, H., Lane, B., Byrne, C. F., Pasternack, G. B., and Sandoval Solis, S.: Evaluating the influence of erosion and tectonic processes on California’s topography by measuring its fractal dimension and anisotropy across scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3520, https://doi.org/10.5194/egusphere-egu21-3520, 2021.
EGU21-3281 | vPICO presentations | GM9.12
Landscape Records 25 Million Years of Tectonic Evolution at an Oblique Convergent Margin, Marlborough Fault System, New ZealandAlison Duvall, Phaedra Upton, Camille Collett, Sarah Harbert, Seth Williams, Rebecca Flowers, Gregory Tucker, John Stone, and Sean LaHusen
The landscape at the NE end of the South Island, New Zealand, records oblique plate collision over the last 25 million years. Using low-temperature thermochronology, geomorphic analyses, and cosmogenic 10Be data, we document the landscape response to tectonics over long (106) and short (102 – 103) timescales in the Marlborough Fault System (MFS) and related Kaikōura Mountains. Our results indicate two broad stages of landscape evolution that reflect a changing plate boundary through time. In the eastern MFS, Miocene folding above blind thrust faults generated prominent Kaikōura Mountain peaks and formed major transverse rivers early in the plate collision history. By the Pliocene, rotation of the plate boundary led to a transition to dextral strike-slip faulting and widespread uplift that led to cycles of river channel offset, deflection and capture of tributaries draining across active faults, and headward erosion and captures by major transverse rivers within the western MFS. Despite clear evidence of recent rearrangement of the western MFS drainage network, rivers in this region still flow parallel to older faults, rather than along orthogonal traces of younger, active strike-slip faults. Such drainage patterns emphasize the importance of river entrenchment, showing that once rivers establish themselves along a structural grain, their capture or avulsion becomes difficult, even when exposed to new weakening and tectonic strain. Over short timescales (hundreds to thousands of years), apparent catchment-wide average erosion rates derived from 10Be data show an increase from SW to NE, along strike of the Seaward Kaikōura Range. These rates mirror spatial increases in elevation, slope, channel steepness, and coseismic landslides, demonstrating that both landscape and geochronology patterns are consistent with an increase in rock uplift rate toward a subduction front that is presently locked on its southern end. Remarkably, the form of the topography, hillslopes, and rivers across much of the MFS appears to faithfully record the complex and changing tectonic history of a long-lived, oblique convergent plate boundary.
How to cite: Duvall, A., Upton, P., Collett, C., Harbert, S., Williams, S., Flowers, R., Tucker, G., Stone, J., and LaHusen, S.: Landscape Records 25 Million Years of Tectonic Evolution at an Oblique Convergent Margin, Marlborough Fault System, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3281, https://doi.org/10.5194/egusphere-egu21-3281, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The landscape at the NE end of the South Island, New Zealand, records oblique plate collision over the last 25 million years. Using low-temperature thermochronology, geomorphic analyses, and cosmogenic 10Be data, we document the landscape response to tectonics over long (106) and short (102 – 103) timescales in the Marlborough Fault System (MFS) and related Kaikōura Mountains. Our results indicate two broad stages of landscape evolution that reflect a changing plate boundary through time. In the eastern MFS, Miocene folding above blind thrust faults generated prominent Kaikōura Mountain peaks and formed major transverse rivers early in the plate collision history. By the Pliocene, rotation of the plate boundary led to a transition to dextral strike-slip faulting and widespread uplift that led to cycles of river channel offset, deflection and capture of tributaries draining across active faults, and headward erosion and captures by major transverse rivers within the western MFS. Despite clear evidence of recent rearrangement of the western MFS drainage network, rivers in this region still flow parallel to older faults, rather than along orthogonal traces of younger, active strike-slip faults. Such drainage patterns emphasize the importance of river entrenchment, showing that once rivers establish themselves along a structural grain, their capture or avulsion becomes difficult, even when exposed to new weakening and tectonic strain. Over short timescales (hundreds to thousands of years), apparent catchment-wide average erosion rates derived from 10Be data show an increase from SW to NE, along strike of the Seaward Kaikōura Range. These rates mirror spatial increases in elevation, slope, channel steepness, and coseismic landslides, demonstrating that both landscape and geochronology patterns are consistent with an increase in rock uplift rate toward a subduction front that is presently locked on its southern end. Remarkably, the form of the topography, hillslopes, and rivers across much of the MFS appears to faithfully record the complex and changing tectonic history of a long-lived, oblique convergent plate boundary.
How to cite: Duvall, A., Upton, P., Collett, C., Harbert, S., Williams, S., Flowers, R., Tucker, G., Stone, J., and LaHusen, S.: Landscape Records 25 Million Years of Tectonic Evolution at an Oblique Convergent Margin, Marlborough Fault System, New Zealand, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3281, https://doi.org/10.5194/egusphere-egu21-3281, 2021.
EGU21-6089 | vPICO presentations | GM9.12
Geologic structures control geomorphic patterns: Linking rectangular drainage evolution, underground pipe systems, and clastic dikesLiran Goren, Matanya Hamawi, Amit Mushkin, and Tsafrir Levi
Rectangular drainage networks are characterized by right-angle channel bends and confluences. The formation of the rectangular pattern is commonly associated with orthogonal sets of fractures, making rectangular drainages an outstanding example of structurally controlled landform evolution. However, the association between geologic structures and rectangular patterns remains circumstantial. So far, no specific mechanisms were suggested to explain the linkage between the emergent right-angle bends and confluences and the preexisting fracture system. This gap is particularly significant for planetary rectangular drainages, where the association with preexisting structures can not be directly observed.
We investigated the mechanistic linkages between geologic structures and the geomorphic drainage pattern in the hyper-arid Ami'az Plain located within the Dead Sea Basin in SE Israel. The Ami'az Plain is incised by a seemingly rectangular canyon system and is also penetrated by hundreds of sub-vertical clastic dikes (mode-I opening cracks infilled with sedimentary material), that reach a width of up to 0.18 m. Additionally, many caves and cavities extend from the banks and heads of the canyon system. Based on field surveys and analysis of a high resolution LiDAR based DEM, we mapped and characterized the Ami’az Plain drainage network and associated geomorphic structures including sinkholes. Our analysis revealed that the canyon system exhibits rectangular characteristics and its tributaries share dominant orientations with the strike of the clastic dikes. Surface and subsurface mapping assisted by Ground scanning LiDAR, together with field experiments, demonstrated that the caves and sinkholes are spatially associated with clastic dikes and that the caves formed by piping erosion along dikes.
Based on these findings, we propose a three-component hydrologic-geomorphic model for the formation of the Ami’az Plain rectangular drainage network: First, clastic dikes act as efficient infiltration pathways for surface runoff into the subsurface, where subsurface flow along clastic dikes induces internal erosion and forms piping caves. Second, collapses of cave roofs create sinkholes. Coalescence of sinkholes and seepage erosion in places where dikes intersect canyon banks and canyon heads generate new tributaries and extend existing ones. Finally, fluvial erosion and bank collapse modify the drainage network. Our observations and model emphasize the critical role of subsurface erosion and the formation of caves and sinkholes in linking fractures to drainage pattern evolution. This linkage could be highly consequential for our understanding of rectangular drainage evolution on planetary and terrestrial surfaces.
How to cite: Goren, L., Hamawi, M., Mushkin, A., and Levi, T.: Geologic structures control geomorphic patterns: Linking rectangular drainage evolution, underground pipe systems, and clastic dikes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6089, https://doi.org/10.5194/egusphere-egu21-6089, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Rectangular drainage networks are characterized by right-angle channel bends and confluences. The formation of the rectangular pattern is commonly associated with orthogonal sets of fractures, making rectangular drainages an outstanding example of structurally controlled landform evolution. However, the association between geologic structures and rectangular patterns remains circumstantial. So far, no specific mechanisms were suggested to explain the linkage between the emergent right-angle bends and confluences and the preexisting fracture system. This gap is particularly significant for planetary rectangular drainages, where the association with preexisting structures can not be directly observed.
We investigated the mechanistic linkages between geologic structures and the geomorphic drainage pattern in the hyper-arid Ami'az Plain located within the Dead Sea Basin in SE Israel. The Ami'az Plain is incised by a seemingly rectangular canyon system and is also penetrated by hundreds of sub-vertical clastic dikes (mode-I opening cracks infilled with sedimentary material), that reach a width of up to 0.18 m. Additionally, many caves and cavities extend from the banks and heads of the canyon system. Based on field surveys and analysis of a high resolution LiDAR based DEM, we mapped and characterized the Ami’az Plain drainage network and associated geomorphic structures including sinkholes. Our analysis revealed that the canyon system exhibits rectangular characteristics and its tributaries share dominant orientations with the strike of the clastic dikes. Surface and subsurface mapping assisted by Ground scanning LiDAR, together with field experiments, demonstrated that the caves and sinkholes are spatially associated with clastic dikes and that the caves formed by piping erosion along dikes.
Based on these findings, we propose a three-component hydrologic-geomorphic model for the formation of the Ami’az Plain rectangular drainage network: First, clastic dikes act as efficient infiltration pathways for surface runoff into the subsurface, where subsurface flow along clastic dikes induces internal erosion and forms piping caves. Second, collapses of cave roofs create sinkholes. Coalescence of sinkholes and seepage erosion in places where dikes intersect canyon banks and canyon heads generate new tributaries and extend existing ones. Finally, fluvial erosion and bank collapse modify the drainage network. Our observations and model emphasize the critical role of subsurface erosion and the formation of caves and sinkholes in linking fractures to drainage pattern evolution. This linkage could be highly consequential for our understanding of rectangular drainage evolution on planetary and terrestrial surfaces.
How to cite: Goren, L., Hamawi, M., Mushkin, A., and Levi, T.: Geologic structures control geomorphic patterns: Linking rectangular drainage evolution, underground pipe systems, and clastic dikes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6089, https://doi.org/10.5194/egusphere-egu21-6089, 2021.
EGU21-1322 | vPICO presentations | GM9.12
Topographic disequilibrium, landscape dynamics and active tectonics: an example from the Bhutan HimalayasMartine Simoes, Timothée Sassolas-Serrayet, Rodolphe Cattin, Romain Le Roux-Mallouf, Matthieu Ferry, and Dowchu Drukpa
The quantification of active tectonics from geomorphological and morphometric approaches most often implies that erosion and tectonics have reached a certain balance. Such equilibrium conditions may however be seldom found in nature, in particular because drainage basins may be quite dynamic even though tectonic and climatic conditions remain constant. Here, we document this drainage dynamics from the particular case example of the Bhutan Himalayas. Evidence for out-of-equilibrium morphologies have for long been noticed in Bhutan, from major (> 1 km high) river knickpoints and from the existence of high-altitude low-relief regions within the mountain hinterland. These peculiar morphologies were generally interpreted as representing a recent change in climatic and/or tectonic conditions. To further characterize these morphologies and their dynamics, and from there discuss their origin and meaning, we perform field observations and a detailed quantitative morphometric analysis using Chi plots and Gilbert metrics of drainages over various spatial scales, from major Himalayan rivers to local streams draining the low-relief regions. We first find that the river network is highly dynamic and unstable. Our results emphasize that the morphology of Bhutan does not result from a general wave of incision propagating upstream, as expected from most previous interpretations. Also, the specific spatial organization in which all major knickpoints and low-relief regions are located along a longitudinal band in the Bhutan hinterland, whatever their spatial scale and the dimensions of the associated drainage basins, calls for a common local supporting mechanism most probably related to active tectonic uplift. Our results emphasize the need for a precise documentation of landscape dynamics and disequilibrium over various spatial scales as a first-order step in morpho-tectonic studies of active landscapes.
How to cite: Simoes, M., Sassolas-Serrayet, T., Cattin, R., Le Roux-Mallouf, R., Ferry, M., and Drukpa, D.: Topographic disequilibrium, landscape dynamics and active tectonics: an example from the Bhutan Himalayas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1322, https://doi.org/10.5194/egusphere-egu21-1322, 2021.
The quantification of active tectonics from geomorphological and morphometric approaches most often implies that erosion and tectonics have reached a certain balance. Such equilibrium conditions may however be seldom found in nature, in particular because drainage basins may be quite dynamic even though tectonic and climatic conditions remain constant. Here, we document this drainage dynamics from the particular case example of the Bhutan Himalayas. Evidence for out-of-equilibrium morphologies have for long been noticed in Bhutan, from major (> 1 km high) river knickpoints and from the existence of high-altitude low-relief regions within the mountain hinterland. These peculiar morphologies were generally interpreted as representing a recent change in climatic and/or tectonic conditions. To further characterize these morphologies and their dynamics, and from there discuss their origin and meaning, we perform field observations and a detailed quantitative morphometric analysis using Chi plots and Gilbert metrics of drainages over various spatial scales, from major Himalayan rivers to local streams draining the low-relief regions. We first find that the river network is highly dynamic and unstable. Our results emphasize that the morphology of Bhutan does not result from a general wave of incision propagating upstream, as expected from most previous interpretations. Also, the specific spatial organization in which all major knickpoints and low-relief regions are located along a longitudinal band in the Bhutan hinterland, whatever their spatial scale and the dimensions of the associated drainage basins, calls for a common local supporting mechanism most probably related to active tectonic uplift. Our results emphasize the need for a precise documentation of landscape dynamics and disequilibrium over various spatial scales as a first-order step in morpho-tectonic studies of active landscapes.
How to cite: Simoes, M., Sassolas-Serrayet, T., Cattin, R., Le Roux-Mallouf, R., Ferry, M., and Drukpa, D.: Topographic disequilibrium, landscape dynamics and active tectonics: an example from the Bhutan Himalayas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1322, https://doi.org/10.5194/egusphere-egu21-1322, 2021.
EGU21-7384 | vPICO presentations | GM9.12
Missing evidence for landscape transience induced by tectonic forcing since the Late Quaternary in the steep marginal escarpments of the Korean PeninsulaJongmin Byun
Steep and narrow escarpments develop along the eastern margin of the Korean Peninsula. They are compartments of a passive continental margin and thus have been considered tectonically stable. In contrast to the traditional notion, geomorphic markers indicative of the enhanced tectonic uplift since the Late Quaternary (i.e., coastal terraces at several different altitudes) have been observed along the eastern coastal areas of the peninsula. Therefore, the steep escarpments in the eastern margin are assumed to be tectonically reactivated. However, the spatial magnitude and timing of the reactivation and how the escarpments have responded to the reactivation have not been well studied. Knickzone is a typical geomorphic marker, which has long been utilized for deciphering the history and distribution of tectonics. Here, we examined the knickzones of the marginal escarpments, where transient knickzones are likely to be observed, in order to understand the spatial pattern of the Late Quaternary reactivation and its effects on the evolution of the marginal escarpments. We used SRTM 1 arc-second DEMs, satellite images with fine resolution, and geological maps to identify and classify knickzones. We also conducted field surveys for the verification of the identified knickzones. As a result of the knickzone analysis, 46 knickzones were identified in the study catchments. Their mean length and gradient are 461 m and 0.19 m/m, respectively. Most knickzones are at relatively high altitudes (i.e., median elevation 532 m) and thus are placed far from the coast. According to the classification of the identified knickzones, they are formed mainly due to varying rock types (11) or changes in lithologic features of the same rock type (e.g., weathering degree of rocks) (31). Few of them are associated with the accumulation of coarse sediments at a channel junction (3) and meander neck cut-off (1). This result implies that all identified knickzones in the study catchments are stationary rather than transient. Consequently, it postulates that the Late Quaternary tectonic forcing was insufficient to generate any transient knickzone. Otherwise, potential transient knickzones due to the reactivation might have disappeared rapidly during their upstream migration, which seems highly relevant to the high concavity of the stream profiles in the drainage basins of the escarpments. Additionally, the result suggests that transient knickzone is not a good indicator for interpreting the responses of the marginal escarpments to the reactivation during the Late Quaternary.
How to cite: Byun, J.: Missing evidence for landscape transience induced by tectonic forcing since the Late Quaternary in the steep marginal escarpments of the Korean Peninsula, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7384, https://doi.org/10.5194/egusphere-egu21-7384, 2021.
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Steep and narrow escarpments develop along the eastern margin of the Korean Peninsula. They are compartments of a passive continental margin and thus have been considered tectonically stable. In contrast to the traditional notion, geomorphic markers indicative of the enhanced tectonic uplift since the Late Quaternary (i.e., coastal terraces at several different altitudes) have been observed along the eastern coastal areas of the peninsula. Therefore, the steep escarpments in the eastern margin are assumed to be tectonically reactivated. However, the spatial magnitude and timing of the reactivation and how the escarpments have responded to the reactivation have not been well studied. Knickzone is a typical geomorphic marker, which has long been utilized for deciphering the history and distribution of tectonics. Here, we examined the knickzones of the marginal escarpments, where transient knickzones are likely to be observed, in order to understand the spatial pattern of the Late Quaternary reactivation and its effects on the evolution of the marginal escarpments. We used SRTM 1 arc-second DEMs, satellite images with fine resolution, and geological maps to identify and classify knickzones. We also conducted field surveys for the verification of the identified knickzones. As a result of the knickzone analysis, 46 knickzones were identified in the study catchments. Their mean length and gradient are 461 m and 0.19 m/m, respectively. Most knickzones are at relatively high altitudes (i.e., median elevation 532 m) and thus are placed far from the coast. According to the classification of the identified knickzones, they are formed mainly due to varying rock types (11) or changes in lithologic features of the same rock type (e.g., weathering degree of rocks) (31). Few of them are associated with the accumulation of coarse sediments at a channel junction (3) and meander neck cut-off (1). This result implies that all identified knickzones in the study catchments are stationary rather than transient. Consequently, it postulates that the Late Quaternary tectonic forcing was insufficient to generate any transient knickzone. Otherwise, potential transient knickzones due to the reactivation might have disappeared rapidly during their upstream migration, which seems highly relevant to the high concavity of the stream profiles in the drainage basins of the escarpments. Additionally, the result suggests that transient knickzone is not a good indicator for interpreting the responses of the marginal escarpments to the reactivation during the Late Quaternary.
How to cite: Byun, J.: Missing evidence for landscape transience induced by tectonic forcing since the Late Quaternary in the steep marginal escarpments of the Korean Peninsula, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7384, https://doi.org/10.5194/egusphere-egu21-7384, 2021.
EGU21-15982 | vPICO presentations | GM9.12
Looking for the hidden morphological signature of active faults in a Low Strain Rate region: clues from the eastern Kachchh region (NW India)Eshaan Srivastava, Nicolò Parrino, Javed Malik, Fabrizio Pepe, and Pierfrancesco Burrato
The Kachchh region (NW India), a pericratonic rift basin delimited by E-W trending major thrust faults, is a Low Strain Rate region[PB1] . In this area, the tectonic forcing magnitude is stronger enough to trigger infrequent significant earthquakes but not enough to overprint the climatic forcing signature. As a consequence, the active faults sources of the largest seismic events are largely poorly known and their geomorphic signature is subdued.
Instrumental and paleoseismological evidence highlights that the eastern part of Kachchh experienced a significant number of seismic events such as the 1819-06-16 Allah Bund earthquake (Mw 7.8, also known as the Rann of Kutch earthquake), the 1956-07-21 Anjar earthquake (Mw 6.1), the 2001-01-26 Bhuj earthquake (Mw 7.6) and the 2006 events (Mw 5.0 and 5.6 earthquake occurred along Island Belt Fault and Gedi fault).
In this region, the unavailability of useful outcrop information due to a significant climatic overprinting of the fault’s morphological signatures hampers the detection and parametrization of actively deforming faults.
For this reason, in this ongoing work, we propose a multidisciplinary approach, aimed at detecting active geological structures and their related [PB2] surface deformation, which mainly consists of quantitative tectonic geomorphology and paleoseismological analyses and structural interpretation and modelling. Preliminary results are a morphotectonic evolution model and 3D fault model of the study area. Finally, we stress the concept that only a multidisciplinary approach could provide useful information to understand better the highly debated active tectonic framework of the study area.
How to cite: Srivastava, E., Parrino, N., Malik, J., Pepe, F., and Burrato, P.: Looking for the hidden morphological signature of active faults in a Low Strain Rate region: clues from the eastern Kachchh region (NW India) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15982, https://doi.org/10.5194/egusphere-egu21-15982, 2021.
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The Kachchh region (NW India), a pericratonic rift basin delimited by E-W trending major thrust faults, is a Low Strain Rate region[PB1] . In this area, the tectonic forcing magnitude is stronger enough to trigger infrequent significant earthquakes but not enough to overprint the climatic forcing signature. As a consequence, the active faults sources of the largest seismic events are largely poorly known and their geomorphic signature is subdued.
Instrumental and paleoseismological evidence highlights that the eastern part of Kachchh experienced a significant number of seismic events such as the 1819-06-16 Allah Bund earthquake (Mw 7.8, also known as the Rann of Kutch earthquake), the 1956-07-21 Anjar earthquake (Mw 6.1), the 2001-01-26 Bhuj earthquake (Mw 7.6) and the 2006 events (Mw 5.0 and 5.6 earthquake occurred along Island Belt Fault and Gedi fault).
In this region, the unavailability of useful outcrop information due to a significant climatic overprinting of the fault’s morphological signatures hampers the detection and parametrization of actively deforming faults.
For this reason, in this ongoing work, we propose a multidisciplinary approach, aimed at detecting active geological structures and their related [PB2] surface deformation, which mainly consists of quantitative tectonic geomorphology and paleoseismological analyses and structural interpretation and modelling. Preliminary results are a morphotectonic evolution model and 3D fault model of the study area. Finally, we stress the concept that only a multidisciplinary approach could provide useful information to understand better the highly debated active tectonic framework of the study area.
How to cite: Srivastava, E., Parrino, N., Malik, J., Pepe, F., and Burrato, P.: Looking for the hidden morphological signature of active faults in a Low Strain Rate region: clues from the eastern Kachchh region (NW India) , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15982, https://doi.org/10.5194/egusphere-egu21-15982, 2021.
EGU21-10469 | vPICO presentations | GM9.12
Active back-arc thrust in North West Java, IndonesiaSonny Aribowo, Laurent Husson, Danny H. Natawidjaja, Christine Authemayou, Mudrik R. Daryono, Anggraini R. Puji, Pierre G. Valla, Astyka Pamumpuni, Dadan D. Wardhana, and Gino de Gelder
The Baribis-Kendeng Fault System crosscuts the northern part of Java Island (Indonesia). It seems that the fault systems is the continuation westward from the active Flores thrust in the northern offshore of the Lesser Sunda Islands. While the Flores thrust in the east is well documented as an active fault in the back-arc platform (e.g., source of the 2018 Lombok 6.9 Mw earthquake), the nature, timing, and activity of the Baribis-Kendeng Fault Systems, particularly the Baribis Fault Zone (BFZ) in the westernmost part of the system remain elusive. Yet, understanding the geological risk associated with the BFZ is crucial, as it crosscuts densely-populated regions, possibly up to 30 million inhabitants in the megalopolis of Jakarta. Previous studies mostly identified the BFZ by first-order morphotectonic observations, as well as large-scale geodetic and seismotectonic investigations, and assigned historical earthquakes (estimated up to 8.5 Mw in 1780) in northern Java to the BFZ. Ground-truthing the structure and activity of the BFZ from geological arguments is a cornerstone to evaluate associated geohazards.
We first focus on the Cikamurang Ridge, nearly at the eastern part of the BFZ, where uplifted Pliocene-Recent sediment sequences outcrop. Morphotectonic data include an 8-m resolution digital elevation model that we used to map fault lineaments and calculate the channel steepness index of the rivers crossing the mapped fault segments. Field data, including paleoseismological trenching at the central part of Cikamurang Ridge and sediment dating (OSL and radiocarbon) provide temporal constraints on the BFZ activity. Subsurface geophysical data include seismic reflection and resistivity imaging provide better image of the fault geometry in the sub-surface.
Our results suggest that the BFZ has been active in the Cikamurang Ridge during the late-Pleistocene to Holocene times, with deformed sediment sequences dated between 55 and 7 ka. Eastward, the BFZ crosses the Cisanggarung River where the fault deformed ~13-ka old sediments. Westward of the Cikamurang Ridge, both fault lineament interpretation and channel steepness index indicates that the fault continues from Subang regency to Jatiluhur and reaches the area between Jakarta and Bogor. Even though in the area between Jakarta and Bogor the surficial trace of the BFZ is not as clear as the Cikamurang and Subang, the seismic reflection data reveal the blind fault propagation fold. We conclude that the BFZ has a high seismic hazard that requires a careful risk evaluation along its trace, as it threats the numerous infrastructures of the extremely densely-populated West Java. Comparing to the Flores back-arc thrust, the existence of the BFZ indicate the whole island of Java affected with the back-arc compressive regime as well as the existence of the Kendeng Fault Zone, in the easternmost of the Baribis-Kendeng Fault Systems.
How to cite: Aribowo, S., Husson, L., Natawidjaja, D. H., Authemayou, C., Daryono, M. R., Puji, A. R., Valla, P. G., Pamumpuni, A., Wardhana, D. D., and de Gelder, G.: Active back-arc thrust in North West Java, Indonesia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10469, https://doi.org/10.5194/egusphere-egu21-10469, 2021.
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The Baribis-Kendeng Fault System crosscuts the northern part of Java Island (Indonesia). It seems that the fault systems is the continuation westward from the active Flores thrust in the northern offshore of the Lesser Sunda Islands. While the Flores thrust in the east is well documented as an active fault in the back-arc platform (e.g., source of the 2018 Lombok 6.9 Mw earthquake), the nature, timing, and activity of the Baribis-Kendeng Fault Systems, particularly the Baribis Fault Zone (BFZ) in the westernmost part of the system remain elusive. Yet, understanding the geological risk associated with the BFZ is crucial, as it crosscuts densely-populated regions, possibly up to 30 million inhabitants in the megalopolis of Jakarta. Previous studies mostly identified the BFZ by first-order morphotectonic observations, as well as large-scale geodetic and seismotectonic investigations, and assigned historical earthquakes (estimated up to 8.5 Mw in 1780) in northern Java to the BFZ. Ground-truthing the structure and activity of the BFZ from geological arguments is a cornerstone to evaluate associated geohazards.
We first focus on the Cikamurang Ridge, nearly at the eastern part of the BFZ, where uplifted Pliocene-Recent sediment sequences outcrop. Morphotectonic data include an 8-m resolution digital elevation model that we used to map fault lineaments and calculate the channel steepness index of the rivers crossing the mapped fault segments. Field data, including paleoseismological trenching at the central part of Cikamurang Ridge and sediment dating (OSL and radiocarbon) provide temporal constraints on the BFZ activity. Subsurface geophysical data include seismic reflection and resistivity imaging provide better image of the fault geometry in the sub-surface.
Our results suggest that the BFZ has been active in the Cikamurang Ridge during the late-Pleistocene to Holocene times, with deformed sediment sequences dated between 55 and 7 ka. Eastward, the BFZ crosses the Cisanggarung River where the fault deformed ~13-ka old sediments. Westward of the Cikamurang Ridge, both fault lineament interpretation and channel steepness index indicates that the fault continues from Subang regency to Jatiluhur and reaches the area between Jakarta and Bogor. Even though in the area between Jakarta and Bogor the surficial trace of the BFZ is not as clear as the Cikamurang and Subang, the seismic reflection data reveal the blind fault propagation fold. We conclude that the BFZ has a high seismic hazard that requires a careful risk evaluation along its trace, as it threats the numerous infrastructures of the extremely densely-populated West Java. Comparing to the Flores back-arc thrust, the existence of the BFZ indicate the whole island of Java affected with the back-arc compressive regime as well as the existence of the Kendeng Fault Zone, in the easternmost of the Baribis-Kendeng Fault Systems.
How to cite: Aribowo, S., Husson, L., Natawidjaja, D. H., Authemayou, C., Daryono, M. R., Puji, A. R., Valla, P. G., Pamumpuni, A., Wardhana, D. D., and de Gelder, G.: Active back-arc thrust in North West Java, Indonesia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10469, https://doi.org/10.5194/egusphere-egu21-10469, 2021.
EGU21-13578 | vPICO presentations | GM9.12
Morphotectonic evidence for widespread active faulting in southern MongoliaJorien L.N. van der Wal, Veit Nottebaum, Georg Stauch, Steven A. Binnie, Ochirbat Batkhishig, Frank Lehmkuhl, and Klaus Reicherter
Four M~8 earthquakes in the 20th century reflect active deformation in western Mongolia as a result of far-field stresses related to the India-Eurasia collision. Historic seismicity indicates that deformation localises around the relatively rigid Hangay dome in central Mongolia, however, tectonic lineaments in the surrounding Valley of Lakes basins suggest more widespread and diffuse deformation. In southern Mongolia, seismicity clusters around the Bogd fault, which ruptured during the 1957 Mw 8.1 Gobi Altai earthquake. To determine whether the kinematics interpreted from this earthquake are regionally representative, especially in consideration of the heterogeneity of intraplate tectonics, we expand the spatial scale of tectonic studies to range between the Gobi Altai and Hangay massifs. We do this by combining observations from regional and local digital elevation models, ground-penetrating radar analyses, geological and geomorphological field data, and seismic reflection data. Additionally, we increase the temporal scale of palaeoseismic studies up until the Middle Pleistocene through OSL and surface exposure dating, to compare the effects of tectonic processes to those of Quaternary climate variations on landscape evolution. We show that reverse and oblique strands of the Bogd fault accommodate <0.3 mm/yr vertical slip rates along the northern margin of the transpressive Gobi Altai massif. Four ~E-W striking faults in the seismically quiescent Valley of Gobi Lakes each have the potential for M~7 earthquakes and they are likely part of a left-lateral strike-slip system rooted at depth. Although cumulatively, the Valley of Gobi Lakes faults are deforming at a regionally representative ~0.3 mm/yr vertical slip rate, recurrence intervals of major earthquakes are much longer than those determined along the Bogd fault (~5-80 ka vs. 3-5 ka). Overall, we interpret the Valley of Gobi Lakes faults to have played a large role in drainage reorganisation and Middle Pleistocene to modern landscape evolution. Sub-surface faults interpreted from seismic reflection data and associated geomorphological irregularities in the Orog Nuur Basin indicate two NW-SE striking lineaments that may connect the Valley of Gobi Lakes fault system to the Bogd fault system. Our observations suggest a more complex and extensive fault system in southern Mongolia than previously expected and the geometry and potential connectivity of faults indicates a continuing northward progression of transpressive deformation from the Gobi Altai towards the Hangay. The obscurity of active deformation in the Valley of Gobi Lakes is likely due to faster erosion and deposition rates and this highlights the importance of understanding the interplay between tectonic, climatic and geomorphological processes and their effects on the landscape system. We suggest that, especially in slowly deforming, intraplate regions, an increase of spatial and temporal scales of active tectonic research is necessary to improve interpretations of tectonically altered landforms, palaeo-environmental reconstructions, and seismic hazard assessments.
How to cite: van der Wal, J. L. N., Nottebaum, V., Stauch, G., Binnie, S. A., Batkhishig, O., Lehmkuhl, F., and Reicherter, K.: Morphotectonic evidence for widespread active faulting in southern Mongolia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13578, https://doi.org/10.5194/egusphere-egu21-13578, 2021.
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Four M~8 earthquakes in the 20th century reflect active deformation in western Mongolia as a result of far-field stresses related to the India-Eurasia collision. Historic seismicity indicates that deformation localises around the relatively rigid Hangay dome in central Mongolia, however, tectonic lineaments in the surrounding Valley of Lakes basins suggest more widespread and diffuse deformation. In southern Mongolia, seismicity clusters around the Bogd fault, which ruptured during the 1957 Mw 8.1 Gobi Altai earthquake. To determine whether the kinematics interpreted from this earthquake are regionally representative, especially in consideration of the heterogeneity of intraplate tectonics, we expand the spatial scale of tectonic studies to range between the Gobi Altai and Hangay massifs. We do this by combining observations from regional and local digital elevation models, ground-penetrating radar analyses, geological and geomorphological field data, and seismic reflection data. Additionally, we increase the temporal scale of palaeoseismic studies up until the Middle Pleistocene through OSL and surface exposure dating, to compare the effects of tectonic processes to those of Quaternary climate variations on landscape evolution. We show that reverse and oblique strands of the Bogd fault accommodate <0.3 mm/yr vertical slip rates along the northern margin of the transpressive Gobi Altai massif. Four ~E-W striking faults in the seismically quiescent Valley of Gobi Lakes each have the potential for M~7 earthquakes and they are likely part of a left-lateral strike-slip system rooted at depth. Although cumulatively, the Valley of Gobi Lakes faults are deforming at a regionally representative ~0.3 mm/yr vertical slip rate, recurrence intervals of major earthquakes are much longer than those determined along the Bogd fault (~5-80 ka vs. 3-5 ka). Overall, we interpret the Valley of Gobi Lakes faults to have played a large role in drainage reorganisation and Middle Pleistocene to modern landscape evolution. Sub-surface faults interpreted from seismic reflection data and associated geomorphological irregularities in the Orog Nuur Basin indicate two NW-SE striking lineaments that may connect the Valley of Gobi Lakes fault system to the Bogd fault system. Our observations suggest a more complex and extensive fault system in southern Mongolia than previously expected and the geometry and potential connectivity of faults indicates a continuing northward progression of transpressive deformation from the Gobi Altai towards the Hangay. The obscurity of active deformation in the Valley of Gobi Lakes is likely due to faster erosion and deposition rates and this highlights the importance of understanding the interplay between tectonic, climatic and geomorphological processes and their effects on the landscape system. We suggest that, especially in slowly deforming, intraplate regions, an increase of spatial and temporal scales of active tectonic research is necessary to improve interpretations of tectonically altered landforms, palaeo-environmental reconstructions, and seismic hazard assessments.
How to cite: van der Wal, J. L. N., Nottebaum, V., Stauch, G., Binnie, S. A., Batkhishig, O., Lehmkuhl, F., and Reicherter, K.: Morphotectonic evidence for widespread active faulting in southern Mongolia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13578, https://doi.org/10.5194/egusphere-egu21-13578, 2021.
EGU21-15425 | vPICO presentations | GM9.12
Elusive active faults in a low strain rate region (Sicily, Italy): hints from a multidisciplinary land-to-sea approachNicolò Parrino, Fabrizio Pepe, Pierfrancesco Burrato, Gino Dardanelli, Cipriano Di Maggio, Marta Corradino, and Claudia Pipitone
Low Strain Rate regions (LSRr), i.e., areas deforming at a 1 mm/yr rate or less, represent the most globally widespread areas that host important cities and high-vulnerable anthropogenic assets. The occurrence of infrequent but high-magnitude earthquakes suggests that identifying active structures in the LSRr is one of the primary challenges for both the scientific community and modern societies.
In such regions, one of the main issues in identifying active faults is the lack of useful outcrop data due to the anthropogenic and climate overprinting of the faults morphological signature. In this work, we propose a multidisciplinary approach designed to detect active geological structures and their related deformation. To test this approach, we selected as a natural laboratory an LSRr located between two major cities of Sicily (southern Italy). This area lies into the northern sector of the Apennine-Maghrebian fold and thrust belt and its offshore prolongation.
Our approach consists of quantitative morphotectonic, offshore and onshore tectonostratigraphic and GNSS joint analyses. The main achieved results are 1) the first evidence of active, shallow-sited, NNW-trending transpressive blind faults that extends partially offshore for about 30 km, which décollement levels located at about 3 and 1 km depth, respectively and their 3D model, 2) a morphotectonic evolution model, that represents where and how these geologic structures drove the landscape evolution of the study area. Finally, we highlight that only a multidisciplinary approach could be useful for detecting and parametrising active faults in slow deforming areas that cross the coastline physical limit.
How to cite: Parrino, N., Pepe, F., Burrato, P., Dardanelli, G., Di Maggio, C., Corradino, M., and Pipitone, C.: Elusive active faults in a low strain rate region (Sicily, Italy): hints from a multidisciplinary land-to-sea approach , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15425, https://doi.org/10.5194/egusphere-egu21-15425, 2021.
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Low Strain Rate regions (LSRr), i.e., areas deforming at a 1 mm/yr rate or less, represent the most globally widespread areas that host important cities and high-vulnerable anthropogenic assets. The occurrence of infrequent but high-magnitude earthquakes suggests that identifying active structures in the LSRr is one of the primary challenges for both the scientific community and modern societies.
In such regions, one of the main issues in identifying active faults is the lack of useful outcrop data due to the anthropogenic and climate overprinting of the faults morphological signature. In this work, we propose a multidisciplinary approach designed to detect active geological structures and their related deformation. To test this approach, we selected as a natural laboratory an LSRr located between two major cities of Sicily (southern Italy). This area lies into the northern sector of the Apennine-Maghrebian fold and thrust belt and its offshore prolongation.
Our approach consists of quantitative morphotectonic, offshore and onshore tectonostratigraphic and GNSS joint analyses. The main achieved results are 1) the first evidence of active, shallow-sited, NNW-trending transpressive blind faults that extends partially offshore for about 30 km, which décollement levels located at about 3 and 1 km depth, respectively and their 3D model, 2) a morphotectonic evolution model, that represents where and how these geologic structures drove the landscape evolution of the study area. Finally, we highlight that only a multidisciplinary approach could be useful for detecting and parametrising active faults in slow deforming areas that cross the coastline physical limit.
How to cite: Parrino, N., Pepe, F., Burrato, P., Dardanelli, G., Di Maggio, C., Corradino, M., and Pipitone, C.: Elusive active faults in a low strain rate region (Sicily, Italy): hints from a multidisciplinary land-to-sea approach , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15425, https://doi.org/10.5194/egusphere-egu21-15425, 2021.
EGU21-10283 | vPICO presentations | GM9.12
Fluctuating Lake Levels in Rift Basins and its Impact on Extensional TectonicsApril Allen Langhans, Robert Moucha, and Michael Keith Paciga
The feedback between climate driven processes; weathering, erosion, sediment transport, and deposition, and extensional tectonics is limited to a few studies (Burov and Cloething, 1997; Burov and Poliakov, 2001; Bialas and Buck, 2009; Theunissen and Huismans, 2019; Andrés-Martínez et al., 2019) despite these processes having been shown to impact the stress state and deformation along active orogens (Koons, 1989; Molnar and England, 1990; Avouac and Burov, 1996; Willett, 1999). Here we utilize a fully coupled landscape evolution and thermomechanical extensional model to investigate the potential impact on faulting and extension due to lake loading changes driven by changes in climate on processional timescales. Fault analyses focusing on heave, throw, and magnitude of dip on faults generated within each model are used to characterize individual faults response to stress changes and rift basin evolution. Preliminary results indicate that fluctuations in lake levels in response to climate change may impact the lithospheric stress state by changing both fault and basin geometries within an extensional basin.
How to cite: Allen Langhans, A., Moucha, R., and Paciga, M. K.: Fluctuating Lake Levels in Rift Basins and its Impact on Extensional Tectonics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10283, https://doi.org/10.5194/egusphere-egu21-10283, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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The feedback between climate driven processes; weathering, erosion, sediment transport, and deposition, and extensional tectonics is limited to a few studies (Burov and Cloething, 1997; Burov and Poliakov, 2001; Bialas and Buck, 2009; Theunissen and Huismans, 2019; Andrés-Martínez et al., 2019) despite these processes having been shown to impact the stress state and deformation along active orogens (Koons, 1989; Molnar and England, 1990; Avouac and Burov, 1996; Willett, 1999). Here we utilize a fully coupled landscape evolution and thermomechanical extensional model to investigate the potential impact on faulting and extension due to lake loading changes driven by changes in climate on processional timescales. Fault analyses focusing on heave, throw, and magnitude of dip on faults generated within each model are used to characterize individual faults response to stress changes and rift basin evolution. Preliminary results indicate that fluctuations in lake levels in response to climate change may impact the lithospheric stress state by changing both fault and basin geometries within an extensional basin.
How to cite: Allen Langhans, A., Moucha, R., and Paciga, M. K.: Fluctuating Lake Levels in Rift Basins and its Impact on Extensional Tectonics, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10283, https://doi.org/10.5194/egusphere-egu21-10283, 2021.
EGU21-6612 | vPICO presentations | GM9.12
Orographic precipitation patterns, stream power, and river longitudinal profiles: Predictions and implications for detecting climate’s influence in mountain landscapesJoel Leonard and Kelin Whipple
Dynamic climates featuring spatially and temporally variable precipitation patterns are ubiquitous in mountain settings. To understand the role of climate on landscape evolution in such settings, and how climate change-related signals might be translated into the sedimentary realm, this variability must be addressed. Here, we present an analysis of how spatial gradients and temporal changes in rainfall combine to affect both the steady state form and transient evolution of river profiles of large transverse river basins as predicted by the stream power model. Where rainfall is uniform, the stream power model predicts that topographic metrics, like fluvial relief and normalized channel steepness index (ksn), vary inversely and monotonically with rainfall at steady state. In contrast, we find that these relationships are more complex and can be inverted in many circumstances, even at steady state, in the presence of orographic rainfall gradients. An important consequence of this is that correlations between average rainfall (climate) and topography are always weaker in catchments that experience rainfall gradients relative to expectations based on uniformly distributed rainfall. Moreover, dispersion caused by rainfall gradients is systematic, varying both with the polarity (i.e., generally increasing vs. decreasing downstream) and intensity of the gradient. Therefore, even in quasi-steady-state, rainfall gradients have the potential to obscure or distort the influence of climate on landscapes if they are not accounted for. In addition, we find that temporal changes in spatially variable rainfall patterns can produce complex erosional and morphological responses that can be contrary to expectations based on the change in mean rainfall. Specifically, enhanced incision and surface uplift may occur simultaneously in different parts of a landscape in a pattern that evolves during the transient response to climate change, complicating prediction of the net erosional and topographic response to climate change. Thus, transient responses to the orographic distribution of rainfall may misleadingly appear inconsistent with erosional or morphological responses expected for a relative change in average climate. Additionally, topographic indications of transient adjustment, even to a dramatic change in orographic precipitation, can be subtle enough that a landscape can appear to be in quasi-steady-state. In such cases, spatial gradients in erosion rate driven by a change in orographic precipitation pattern may be mistakenly interpreted as recording spatial gradients in rock uplift rate, potentially at once obscuring an important influence of climate and misinterpreting tectonic drivers of landscape evolution. Finally, we explore the use of a variant of normalized channel steepness index (ksn-q) that is able to incorporate the influence of spatially variable in rainfall based on the stream power model. Importantly, we find that ksn-q preforms well to help diagnose and quantify the role of climate acting in a landscape, in particular during transient adjustment to changes in rainfall patterns where the standard channel steepness metric (ksn) may be misleading.
How to cite: Leonard, J. and Whipple, K.: Orographic precipitation patterns, stream power, and river longitudinal profiles: Predictions and implications for detecting climate’s influence in mountain landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6612, https://doi.org/10.5194/egusphere-egu21-6612, 2021.
Dynamic climates featuring spatially and temporally variable precipitation patterns are ubiquitous in mountain settings. To understand the role of climate on landscape evolution in such settings, and how climate change-related signals might be translated into the sedimentary realm, this variability must be addressed. Here, we present an analysis of how spatial gradients and temporal changes in rainfall combine to affect both the steady state form and transient evolution of river profiles of large transverse river basins as predicted by the stream power model. Where rainfall is uniform, the stream power model predicts that topographic metrics, like fluvial relief and normalized channel steepness index (ksn), vary inversely and monotonically with rainfall at steady state. In contrast, we find that these relationships are more complex and can be inverted in many circumstances, even at steady state, in the presence of orographic rainfall gradients. An important consequence of this is that correlations between average rainfall (climate) and topography are always weaker in catchments that experience rainfall gradients relative to expectations based on uniformly distributed rainfall. Moreover, dispersion caused by rainfall gradients is systematic, varying both with the polarity (i.e., generally increasing vs. decreasing downstream) and intensity of the gradient. Therefore, even in quasi-steady-state, rainfall gradients have the potential to obscure or distort the influence of climate on landscapes if they are not accounted for. In addition, we find that temporal changes in spatially variable rainfall patterns can produce complex erosional and morphological responses that can be contrary to expectations based on the change in mean rainfall. Specifically, enhanced incision and surface uplift may occur simultaneously in different parts of a landscape in a pattern that evolves during the transient response to climate change, complicating prediction of the net erosional and topographic response to climate change. Thus, transient responses to the orographic distribution of rainfall may misleadingly appear inconsistent with erosional or morphological responses expected for a relative change in average climate. Additionally, topographic indications of transient adjustment, even to a dramatic change in orographic precipitation, can be subtle enough that a landscape can appear to be in quasi-steady-state. In such cases, spatial gradients in erosion rate driven by a change in orographic precipitation pattern may be mistakenly interpreted as recording spatial gradients in rock uplift rate, potentially at once obscuring an important influence of climate and misinterpreting tectonic drivers of landscape evolution. Finally, we explore the use of a variant of normalized channel steepness index (ksn-q) that is able to incorporate the influence of spatially variable in rainfall based on the stream power model. Importantly, we find that ksn-q preforms well to help diagnose and quantify the role of climate acting in a landscape, in particular during transient adjustment to changes in rainfall patterns where the standard channel steepness metric (ksn) may be misleading.
How to cite: Leonard, J. and Whipple, K.: Orographic precipitation patterns, stream power, and river longitudinal profiles: Predictions and implications for detecting climate’s influence in mountain landscapes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6612, https://doi.org/10.5194/egusphere-egu21-6612, 2021.
EGU21-9250 | vPICO presentations | GM9.12
Active thrusting and glacial controls recorded by stratigraphic unconformities in a Quaternary foreland basin (Po basin, Northern Italy)Chiara Zuffetti and Riccardo Bersezio
In active foreland basins, stratigraphic unconformities develop on the flanks and crests of the uplifting thrust-related structures and correspond to correlative conformities in the adjacent depocenters. The geometrical, morphological, stratigraphic, sedimentological, and petrographic attributes of unconformities and associated sediments are highly variable from the uplifting to the subsiding basin sectors. In Quaternary continental foreland basins, landscape evolution, sedimentation, and the nature of the geological boundaries are controlled by the competing turnovers of climate (i.e. glacial advances and retreats) and tectonics (i.e. steady-state uplift/subsidence vs. unsteady deformation increments).
In order to recognize the fingerprints of tectonic and climatic factors on the nature of the stratigraphic unconformities, we studied the Pleistocene shallow marine (Calabrian) to alluvial and glacio-fluvial sediments (Calabrian-Latest Pleistocene) associated to the active external arc of the N-Apennine thrusts in the Quaternary Po basin of Lombardy (N-Italy).
A set of intra-basin reliefs corresponding to ramp-folds was the key-site to describe the nature and attributes of the exposed Pleistocene unconformities and stratigraphy. We integrated different-scale geological, sedimentological, stratigraphic, geo-pedological, geomorphological, and structural field surveys, constrained by C14 and OSL age determinations, to down-trace the stratigraphic boundaries to the subsurface and to assist correlation of borehole logs and geophysical images. The surface facies associations of the stratigraphic units were compared to the litho-textural associations of their subsurface equivalents to draw the best fitting surface-subsurface model, which was constrained to the geological evolution and chronostratigraphy. A hierarchic 3D geological model was computed by the potential field method, which includes the 4D attributes of the stratigraphic boundaries and unconformities organized into three hierarchic orders. Among them, five Quaternary high-rank, and seven intermediate-rank unconformities were recognized.
The high-rank unconformities (Gelasian, intra-Calabrian, Early-Middle Pleistocene, Late Pleistocene and Latest Pleistocene-Holocene unconformities) are erosional, angular (high angle), composite, diachronous surfaces. They originated in front of and above the uplifting ramp-folds, where the discrete, polyphase, and unsteady propagation stages of the blind outermost Apennines arc directly controlled sedimentation, erosion, and accommodation patterns. The intermediate- and low-rank stratigraphic boundaries are either: (i) stratigraphic surfaces of erosion and deposition, occasionally with low-angle unconformity; (ii) stratigraphic surfaces of aggradation (covered by late Pleistocene loess units at places); (iii) morphological surfaces of stabilization marked by (paleo-) soils. These attributes and the 3D relations with the high-rank unconformities show that these surfaces formed during steady uplift/subsidence increments and/or at times or sites of tectonic quiescence. In these cases, the development of erosion surfaces, facies and provenance changes are not associated to tectonic-induced angles, wedging or fanning of sedimentary units. Chronological constraints link these changes to the regional advances and retreats of the Pleistocene alpine glaciers, suggesting that the intermediate-rank surfaces are mostly dependent on the major climate changes, while the low-rank ones relate to depositional unsteadiness, either autocyclic or short-term allocyclic.
How to cite: Zuffetti, C. and Bersezio, R.: Active thrusting and glacial controls recorded by stratigraphic unconformities in a Quaternary foreland basin (Po basin, Northern Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9250, https://doi.org/10.5194/egusphere-egu21-9250, 2021.
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In active foreland basins, stratigraphic unconformities develop on the flanks and crests of the uplifting thrust-related structures and correspond to correlative conformities in the adjacent depocenters. The geometrical, morphological, stratigraphic, sedimentological, and petrographic attributes of unconformities and associated sediments are highly variable from the uplifting to the subsiding basin sectors. In Quaternary continental foreland basins, landscape evolution, sedimentation, and the nature of the geological boundaries are controlled by the competing turnovers of climate (i.e. glacial advances and retreats) and tectonics (i.e. steady-state uplift/subsidence vs. unsteady deformation increments).
In order to recognize the fingerprints of tectonic and climatic factors on the nature of the stratigraphic unconformities, we studied the Pleistocene shallow marine (Calabrian) to alluvial and glacio-fluvial sediments (Calabrian-Latest Pleistocene) associated to the active external arc of the N-Apennine thrusts in the Quaternary Po basin of Lombardy (N-Italy).
A set of intra-basin reliefs corresponding to ramp-folds was the key-site to describe the nature and attributes of the exposed Pleistocene unconformities and stratigraphy. We integrated different-scale geological, sedimentological, stratigraphic, geo-pedological, geomorphological, and structural field surveys, constrained by C14 and OSL age determinations, to down-trace the stratigraphic boundaries to the subsurface and to assist correlation of borehole logs and geophysical images. The surface facies associations of the stratigraphic units were compared to the litho-textural associations of their subsurface equivalents to draw the best fitting surface-subsurface model, which was constrained to the geological evolution and chronostratigraphy. A hierarchic 3D geological model was computed by the potential field method, which includes the 4D attributes of the stratigraphic boundaries and unconformities organized into three hierarchic orders. Among them, five Quaternary high-rank, and seven intermediate-rank unconformities were recognized.
The high-rank unconformities (Gelasian, intra-Calabrian, Early-Middle Pleistocene, Late Pleistocene and Latest Pleistocene-Holocene unconformities) are erosional, angular (high angle), composite, diachronous surfaces. They originated in front of and above the uplifting ramp-folds, where the discrete, polyphase, and unsteady propagation stages of the blind outermost Apennines arc directly controlled sedimentation, erosion, and accommodation patterns. The intermediate- and low-rank stratigraphic boundaries are either: (i) stratigraphic surfaces of erosion and deposition, occasionally with low-angle unconformity; (ii) stratigraphic surfaces of aggradation (covered by late Pleistocene loess units at places); (iii) morphological surfaces of stabilization marked by (paleo-) soils. These attributes and the 3D relations with the high-rank unconformities show that these surfaces formed during steady uplift/subsidence increments and/or at times or sites of tectonic quiescence. In these cases, the development of erosion surfaces, facies and provenance changes are not associated to tectonic-induced angles, wedging or fanning of sedimentary units. Chronological constraints link these changes to the regional advances and retreats of the Pleistocene alpine glaciers, suggesting that the intermediate-rank surfaces are mostly dependent on the major climate changes, while the low-rank ones relate to depositional unsteadiness, either autocyclic or short-term allocyclic.
How to cite: Zuffetti, C. and Bersezio, R.: Active thrusting and glacial controls recorded by stratigraphic unconformities in a Quaternary foreland basin (Po basin, Northern Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9250, https://doi.org/10.5194/egusphere-egu21-9250, 2021.
EGU21-10781 | vPICO presentations | GM9.12
Pleistocene to Holocene river terraces in the Tropoja Basin (northeastern Albania) record tectonic and climatic fluctuations modulated by drainage integration processes.Lorenzo Gemignani, Benedict Mittelbach, Daniel Simon, Kristina Hippe, Marc Grund, Alexander Rohrmann, and Mark Handy
River terraces provide insight into the spatial-temporal patterns of transient tectonic and climatic forcings. The Tropoja Basin is located at the junction of the Dinaride-Albanide-Hellenide belt in north-eastern Albania and is part of the hanging wall of the Shkoder Peja Normal Fault (SPNF) system, which accommodated orogen-parallel extension since Early- to Mid-Miocene times. The basin features Plio-Pleistocene fill comprising lacustrine deposits (Pliocene) overlain by sub-horizontal layers of carbonate-rich conglomerates and marl that are interlayered by reddish clay. We found that this fill was incised by at least three generations of river terraces (T1-T3). The controls on river terrace formation within the area, i.e. faulting, climate events and drainage evolution, have been unclear so far. In this study, we date the river terraces within the Tropoja Basin with 36Cl-cosmogenic-nuclide depth-profiles dating and combine these results with further fluvial geomorphic analysis of digital elevation models (DEM) to assess the process of terrace formation in the light of region-wide drainage basin reorganization.
36Cl-depth-profiles dating yield ages of ~ 8.8 ka for the youngest terrace (T1) and ~ 15.4 ka for the intermediate terrace level (T2), indicating that both terraces formed after the Last Glacial Maximum (LGM). Imbrication of conglomeratic clasts in terrace T2 suggests that the paleo flow was southwest directed at the time of deposition followed by a high incision rate of ~7 mm/yr. Also, we checked for activity of the SPNF and its potential impact on terrace formation in the basin by calculating normalised channel steepness index (Ksn) for streams crossing the fault. We found that Ksn-values do not change across that part of SPNF, thus indicating inactivity of the fault in the late Pleistocene to Holocene times. Instead, Ksn-values correlate well with the upper limit of the ice sheet of the LGM of the Valbona Valley. Despite the recent inactivity of the SPNF, the fault might have controlled the spatial fluvial bedrock competence by emplacing carbonates in the footwall adjacent to ophiolites and mélange in the hanging wall forming the floor of the Tropoja Basin. Chi-values of the regional river network in the Tropoja Basin (includes the Valbona and Gashit Rivers, parts of the Drin River system) reveals that the basin was internally drained.
We conclude that the Pleistocene fill of the Tropoje Basin post-dates most, if not all normal faulting. The time difference between Mio-Pliocene normal faulting and Pleistocene filling of the basin suggests that sedimentation and incision were controlled directly by climate and basin connectivity through the river network to the regional base-level of the Adriatic Sea. Internally drained, the basin led to lake formation prior the LGM where at times reconnected with regional base-level of the Adriatic Sea after via the Drin River system. This transient evolution of the river network was characterised by basin filling and potential river over-spilling leading to drainage integration events with increased headward erosion and river entrenchment.
How to cite: Gemignani, L., Mittelbach, B., Simon, D., Hippe, K., Grund, M., Rohrmann, A., and Handy, M.: Pleistocene to Holocene river terraces in the Tropoja Basin (northeastern Albania) record tectonic and climatic fluctuations modulated by drainage integration processes. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10781, https://doi.org/10.5194/egusphere-egu21-10781, 2021.
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Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
River terraces provide insight into the spatial-temporal patterns of transient tectonic and climatic forcings. The Tropoja Basin is located at the junction of the Dinaride-Albanide-Hellenide belt in north-eastern Albania and is part of the hanging wall of the Shkoder Peja Normal Fault (SPNF) system, which accommodated orogen-parallel extension since Early- to Mid-Miocene times. The basin features Plio-Pleistocene fill comprising lacustrine deposits (Pliocene) overlain by sub-horizontal layers of carbonate-rich conglomerates and marl that are interlayered by reddish clay. We found that this fill was incised by at least three generations of river terraces (T1-T3). The controls on river terrace formation within the area, i.e. faulting, climate events and drainage evolution, have been unclear so far. In this study, we date the river terraces within the Tropoja Basin with 36Cl-cosmogenic-nuclide depth-profiles dating and combine these results with further fluvial geomorphic analysis of digital elevation models (DEM) to assess the process of terrace formation in the light of region-wide drainage basin reorganization.
36Cl-depth-profiles dating yield ages of ~ 8.8 ka for the youngest terrace (T1) and ~ 15.4 ka for the intermediate terrace level (T2), indicating that both terraces formed after the Last Glacial Maximum (LGM). Imbrication of conglomeratic clasts in terrace T2 suggests that the paleo flow was southwest directed at the time of deposition followed by a high incision rate of ~7 mm/yr. Also, we checked for activity of the SPNF and its potential impact on terrace formation in the basin by calculating normalised channel steepness index (Ksn) for streams crossing the fault. We found that Ksn-values do not change across that part of SPNF, thus indicating inactivity of the fault in the late Pleistocene to Holocene times. Instead, Ksn-values correlate well with the upper limit of the ice sheet of the LGM of the Valbona Valley. Despite the recent inactivity of the SPNF, the fault might have controlled the spatial fluvial bedrock competence by emplacing carbonates in the footwall adjacent to ophiolites and mélange in the hanging wall forming the floor of the Tropoja Basin. Chi-values of the regional river network in the Tropoja Basin (includes the Valbona and Gashit Rivers, parts of the Drin River system) reveals that the basin was internally drained.
We conclude that the Pleistocene fill of the Tropoje Basin post-dates most, if not all normal faulting. The time difference between Mio-Pliocene normal faulting and Pleistocene filling of the basin suggests that sedimentation and incision were controlled directly by climate and basin connectivity through the river network to the regional base-level of the Adriatic Sea. Internally drained, the basin led to lake formation prior the LGM where at times reconnected with regional base-level of the Adriatic Sea after via the Drin River system. This transient evolution of the river network was characterised by basin filling and potential river over-spilling leading to drainage integration events with increased headward erosion and river entrenchment.
How to cite: Gemignani, L., Mittelbach, B., Simon, D., Hippe, K., Grund, M., Rohrmann, A., and Handy, M.: Pleistocene to Holocene river terraces in the Tropoja Basin (northeastern Albania) record tectonic and climatic fluctuations modulated by drainage integration processes. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10781, https://doi.org/10.5194/egusphere-egu21-10781, 2021.
EGU21-15164 | vPICO presentations | GM9.12
High-resolution topography of the uplifting Huon Peninsula (Papua New Guinea) reveals high interstadial sea-levels over the past ~400 kaGino de Gelder, Laurent Husson, Anne-Morwenn Pastier, Denovan Chauveau, David Fernández-Blanco, Tamara Pico, Christine Authemayou, and Kevin Pedoja
Quaternary sea-level curves provide crucial insights to constrain tectonic and climatic processes, but require calibration with geological constraints that are particularly scarce for cold periods prior to the last glacial-interglacial cycle. To derive such constraints, we re-visit the Huon Peninsula in Papua New Guinea, which is a classic coral reef terrace (CRT) site that was used for the earliest relative sea-level (RSL) curves. We use digital surface models calculated from 0.5m Pleiades satellite imagery to improve RSL constraints, and unlike previous studies, we find that large-scale tilting of the terrace sequence is generally N-directed. This implies that RSL estimates are several meters higher than previously thought for most highstands over the past ~125 ka. We use the large-scale geometry of the terrace sequence to estimate sea-level highstands up to ~400 ka, and our results suggest that global mean sea-level curves derived from oxygen isotopes consistently underestimate sea-level during the relatively cold Marine Isotope Stages 3, 5a, 5c, 6, 9a and 11a, up to ~10-20 m. We use coral reef models to show that our age interpretation is consistent with the overall terrace sequence morphology, and fits between models and topography improve when adjusting sea-level highstands according to our findings.
How to cite: de Gelder, G., Husson, L., Pastier, A.-M., Chauveau, D., Fernández-Blanco, D., Pico, T., Authemayou, C., and Pedoja, K.: High-resolution topography of the uplifting Huon Peninsula (Papua New Guinea) reveals high interstadial sea-levels over the past ~400 ka, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15164, https://doi.org/10.5194/egusphere-egu21-15164, 2021.
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Quaternary sea-level curves provide crucial insights to constrain tectonic and climatic processes, but require calibration with geological constraints that are particularly scarce for cold periods prior to the last glacial-interglacial cycle. To derive such constraints, we re-visit the Huon Peninsula in Papua New Guinea, which is a classic coral reef terrace (CRT) site that was used for the earliest relative sea-level (RSL) curves. We use digital surface models calculated from 0.5m Pleiades satellite imagery to improve RSL constraints, and unlike previous studies, we find that large-scale tilting of the terrace sequence is generally N-directed. This implies that RSL estimates are several meters higher than previously thought for most highstands over the past ~125 ka. We use the large-scale geometry of the terrace sequence to estimate sea-level highstands up to ~400 ka, and our results suggest that global mean sea-level curves derived from oxygen isotopes consistently underestimate sea-level during the relatively cold Marine Isotope Stages 3, 5a, 5c, 6, 9a and 11a, up to ~10-20 m. We use coral reef models to show that our age interpretation is consistent with the overall terrace sequence morphology, and fits between models and topography improve when adjusting sea-level highstands according to our findings.
How to cite: de Gelder, G., Husson, L., Pastier, A.-M., Chauveau, D., Fernández-Blanco, D., Pico, T., Authemayou, C., and Pedoja, K.: High-resolution topography of the uplifting Huon Peninsula (Papua New Guinea) reveals high interstadial sea-levels over the past ~400 ka, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15164, https://doi.org/10.5194/egusphere-egu21-15164, 2021.
EGU21-2915 | vPICO presentations | GM9.12
Defining denudation rate of carbonate rocks using cosmogenic 36Cl in the Taurus Mountain, S-SW TurkeyKhadijeh Hashemi, M. Akif Sarıkaya, and Klaus M. Wilcken
Denudation of carbonate terrains occurs by the contribution of both chemical and mechanical weathering. In-situ cosmogenic 36Cl is a robust proxy to quantify the long-term total denudation rate of carbonate rocks. In this study, we defined the steady-state denudation rate of carbonate bedrock using 36Cl for 105-106 years under the temperate Mediterranean to semi-arid climate in and around the Taurus Mountain Range, S-SW Turkey. We collected 13 samples from different lithological units; Jurassic-Cretaceous neritic limestone in the temperate western Taurus, Miocene neritic limestone in the semi-arid Central Taurus, and Mesozoic marbles in the continental part of Central Taurus. The calculated denudation rates range from 28.9 ± 1.4 mm/ka in the Mediterranean coastal range to 1.6 ± 0.1 mm/ka towards northern continental/rain shadow. We compared the denudation rates with a range of parameters such as topographic, climatic, lithologic and mechanical properties of rocks. For almost all samples denudation rate increases with elevation, with two exceptions with the highest rates despite their lower elevations. This high denudation rates could be due to their proximity to the sea. Our results showed that denudation rates decrease with increasing distance from the coast. All denudation rates showed a positive correlation with mean annual precipitation (MAP ~ 400-760 mm) as suggested by other studies worldwide. Annual temperatures (MAT ~ 6-16 °C), however, has a negative correlation with the denudation rates, i.e. the highest denudations occur in the low temperatures (MAT ~ 6-8 °C). The mechanical strength of the rocks was measured with a Schmidt hammer in the field. The high rebound values of Schmidt hammer, indicating the high mechanical strength, correlate with low denudation rates. Nevertheless, the mechanical strength of the carbonate bedrock is not as effective as precipitation or available moisture on denudation rates. This could be shown by two samples close to the Mediterranean which both have high mechanical strength nonetheless show the highest denudation rates. In conclusion, our study suggests that carbonate bedrock denudation in Taurus Mountain correlates with high elevation (~ 1900-2250 m), high precipitation (~ 700-800 mm), low temperatures (~ 6-8 °C) and short distances from the Mediterranean coast.
How to cite: Hashemi, K., Sarıkaya, M. A., and Wilcken, K. M.: Defining denudation rate of carbonate rocks using cosmogenic 36Cl in the Taurus Mountain, S-SW Turkey, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2915, https://doi.org/10.5194/egusphere-egu21-2915, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Denudation of carbonate terrains occurs by the contribution of both chemical and mechanical weathering. In-situ cosmogenic 36Cl is a robust proxy to quantify the long-term total denudation rate of carbonate rocks. In this study, we defined the steady-state denudation rate of carbonate bedrock using 36Cl for 105-106 years under the temperate Mediterranean to semi-arid climate in and around the Taurus Mountain Range, S-SW Turkey. We collected 13 samples from different lithological units; Jurassic-Cretaceous neritic limestone in the temperate western Taurus, Miocene neritic limestone in the semi-arid Central Taurus, and Mesozoic marbles in the continental part of Central Taurus. The calculated denudation rates range from 28.9 ± 1.4 mm/ka in the Mediterranean coastal range to 1.6 ± 0.1 mm/ka towards northern continental/rain shadow. We compared the denudation rates with a range of parameters such as topographic, climatic, lithologic and mechanical properties of rocks. For almost all samples denudation rate increases with elevation, with two exceptions with the highest rates despite their lower elevations. This high denudation rates could be due to their proximity to the sea. Our results showed that denudation rates decrease with increasing distance from the coast. All denudation rates showed a positive correlation with mean annual precipitation (MAP ~ 400-760 mm) as suggested by other studies worldwide. Annual temperatures (MAT ~ 6-16 °C), however, has a negative correlation with the denudation rates, i.e. the highest denudations occur in the low temperatures (MAT ~ 6-8 °C). The mechanical strength of the rocks was measured with a Schmidt hammer in the field. The high rebound values of Schmidt hammer, indicating the high mechanical strength, correlate with low denudation rates. Nevertheless, the mechanical strength of the carbonate bedrock is not as effective as precipitation or available moisture on denudation rates. This could be shown by two samples close to the Mediterranean which both have high mechanical strength nonetheless show the highest denudation rates. In conclusion, our study suggests that carbonate bedrock denudation in Taurus Mountain correlates with high elevation (~ 1900-2250 m), high precipitation (~ 700-800 mm), low temperatures (~ 6-8 °C) and short distances from the Mediterranean coast.
How to cite: Hashemi, K., Sarıkaya, M. A., and Wilcken, K. M.: Defining denudation rate of carbonate rocks using cosmogenic 36Cl in the Taurus Mountain, S-SW Turkey, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2915, https://doi.org/10.5194/egusphere-egu21-2915, 2021.
EGU21-12607 | vPICO presentations | GM9.12
Denudation response of the Mediterranean Alpine Ranges to the Quaternary glacial cyclesPierre-Henri Blard, Stéphane Molliex, Apolline Mariotti, Julien Charreau, Gwenaël Jouet, Samuel Toucanne, and Stephan Jorry
It is important to better understand how climatic fluctuations modified denudation, in particular during the large amplitude glacial cycles of the Quaternary, not only because denudation is thought to be a long-term climate pacer, but also because available denudation records are contradictory and sometimes underconstrained. To make progress on this question, we present here a compilation of 10Be-derived denudation rates from 6 boreholes and cores drilled in offshore sediments from two alpine massifs of the Mediterranean Sea: Southern Alps (Var River) and Corsica (Golo River). This original dataset of 60 10Be samples from well-dated sedimentary archives documents at high resolution (1 kyr in some sections) the denudation variability over the last 3 million years of the alpine reliefs, with a special focus on the last five 100 kyr glacial cycles. Our new record brings two main results:
1) At the million years timescale, the appearance of the Quaternary glaciations at the Plio-Pleistocene transition (2.6 Ma) had a negligible impact on the mean 10Be-derived denudation rates of Mediterranean Alpine reliefs. This observation is in good agreement with other 10Be-denudation rates records from Asia (Tianshan and Himalaya) that report a limited impact of the Pleistocene climatic transition (Puchol et al., 2017; Charreau et al., 2020; Lenard et al., 2020), but at odds with other regions of the American Cordilleras, where tectonic may have played a role (Stock et al., 2004; Granger and Schaller, 2014).
2) At the glacial-interglacial cycles timescale, our high resolution 10Be data over the last 500 kys reveal that glacial maxima enhanced denudation compared to interglacial periods. However, this impact is variable in space and time, different denudation responses being observed between Southern Alps and Corsica. This contrasted behavior appears to be controlled by the velocity of paleoglaciers. Glacier flow being determined by the combined impact of paleoclimate and basin reliefs, this mechanism is responsible for a non-linear response of denudation to glacier fluctuations. This may explain why glaciations had regionally variable impacts on denudation (Mariotti et al., 2021).
References
Charreau, J. et al. (2020) Basin Research. doi: 10.1111/bre.12511; Granger, D. E. and Schaller, M. (2014) Elements, doi: 10.2113/gselements.10.5.369; Lenard, S. J. P. et al. (2020) Nature Geoscience, doi: 10.1038/s41561-020-0585-2; Mariotti, A. et al. (2021) Nature Geoscience, doi: 10.1038/s41561-020-00672-2; Puchol, N. et al. (2017) Bulletin of the Geological Society of America, doi: 10.1130/B31475.1; Stock, G. M., et al. (2004) Geology, doi: 10.1130/G20197.1.
How to cite: Blard, P.-H., Molliex, S., Mariotti, A., Charreau, J., Jouet, G., Toucanne, S., and Jorry, S.: Denudation response of the Mediterranean Alpine Ranges to the Quaternary glacial cycles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12607, https://doi.org/10.5194/egusphere-egu21-12607, 2021.
It is important to better understand how climatic fluctuations modified denudation, in particular during the large amplitude glacial cycles of the Quaternary, not only because denudation is thought to be a long-term climate pacer, but also because available denudation records are contradictory and sometimes underconstrained. To make progress on this question, we present here a compilation of 10Be-derived denudation rates from 6 boreholes and cores drilled in offshore sediments from two alpine massifs of the Mediterranean Sea: Southern Alps (Var River) and Corsica (Golo River). This original dataset of 60 10Be samples from well-dated sedimentary archives documents at high resolution (1 kyr in some sections) the denudation variability over the last 3 million years of the alpine reliefs, with a special focus on the last five 100 kyr glacial cycles. Our new record brings two main results:
1) At the million years timescale, the appearance of the Quaternary glaciations at the Plio-Pleistocene transition (2.6 Ma) had a negligible impact on the mean 10Be-derived denudation rates of Mediterranean Alpine reliefs. This observation is in good agreement with other 10Be-denudation rates records from Asia (Tianshan and Himalaya) that report a limited impact of the Pleistocene climatic transition (Puchol et al., 2017; Charreau et al., 2020; Lenard et al., 2020), but at odds with other regions of the American Cordilleras, where tectonic may have played a role (Stock et al., 2004; Granger and Schaller, 2014).
2) At the glacial-interglacial cycles timescale, our high resolution 10Be data over the last 500 kys reveal that glacial maxima enhanced denudation compared to interglacial periods. However, this impact is variable in space and time, different denudation responses being observed between Southern Alps and Corsica. This contrasted behavior appears to be controlled by the velocity of paleoglaciers. Glacier flow being determined by the combined impact of paleoclimate and basin reliefs, this mechanism is responsible for a non-linear response of denudation to glacier fluctuations. This may explain why glaciations had regionally variable impacts on denudation (Mariotti et al., 2021).
References
Charreau, J. et al. (2020) Basin Research. doi: 10.1111/bre.12511; Granger, D. E. and Schaller, M. (2014) Elements, doi: 10.2113/gselements.10.5.369; Lenard, S. J. P. et al. (2020) Nature Geoscience, doi: 10.1038/s41561-020-0585-2; Mariotti, A. et al. (2021) Nature Geoscience, doi: 10.1038/s41561-020-00672-2; Puchol, N. et al. (2017) Bulletin of the Geological Society of America, doi: 10.1130/B31475.1; Stock, G. M., et al. (2004) Geology, doi: 10.1130/G20197.1.
How to cite: Blard, P.-H., Molliex, S., Mariotti, A., Charreau, J., Jouet, G., Toucanne, S., and Jorry, S.: Denudation response of the Mediterranean Alpine Ranges to the Quaternary glacial cycles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12607, https://doi.org/10.5194/egusphere-egu21-12607, 2021.
EGU21-9389 | vPICO presentations | GM9.12
Not every large glacial episode lowers valley bottoms: inisghts from the cave systems of the Tatra Mts (the Western Carpathians)Jacek Szczygieł, Helena Hercman, Gregory Hoke, Michał Gąsiorowski, Marcin Błaszczyk, and Artur Sobczyk
The Tatra mountains, the northernmost portion of the Central Western Carpathians, host a stunning alpine landscape despite an average elevation that rises 1.4 km above the surrounding lowlands. Regional geomorphology studies on both sides of the range correlate various landforms interpreted to be glacial in origin with all each of the eight major Alpine glacial events based largely landscape position, and in some cases geochronologic constraints. This regional relative chronology assumes that wet-based mountain glaciers are efficient agents of erosion and each successive glaciation lowered the valleys within the Tatra. While the tendency of subsequent glaciations to obscure evidence of previous events makes it difficult to study the work done by past glacial episodes, the cave networks on the northern side of the Tatra offer a way to evaluate the amount and timing of valley lowering with U-series dating of speleothems. Epiphreatic and paleophreatic caves that developed near the water table and dried out as valley deepening occurred can serve as excellent recorders of the valley incision history.
Speleothems were collected from a number of cave levels present throughout the northern Tatra, of which only a subset were suitable for U-series geochronology. The oldest speleothems collected in active epiphreatic passages on the valley bottom level from each valley are consistently between 284-325 ka (MIS 8-9). This shows that the modern karst drainage system of the Tatra was established prior to the late Middle Pleistocene, and the cave conduits changed to epiphreatic or vadose conditions between 280 and 330 ka. Since the lowest cave level is at or below the modern valley floor, we can conclude that no valley incision occurred after ~330 ka, which includes both the penultimate and last glaciations periods. Clearly, the regional glacial chronologies in the Tatra must be reassessed. The implications of our findings demonstrate that the assumption of successive valley lowering should not be assumed and that even the extensive MIS2 glaciation did not result in valley lowering despite its size.
How to cite: Szczygieł, J., Hercman, H., Hoke, G., Gąsiorowski, M., Błaszczyk, M., and Sobczyk, A.: Not every large glacial episode lowers valley bottoms: inisghts from the cave systems of the Tatra Mts (the Western Carpathians), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9389, https://doi.org/10.5194/egusphere-egu21-9389, 2021.
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The Tatra mountains, the northernmost portion of the Central Western Carpathians, host a stunning alpine landscape despite an average elevation that rises 1.4 km above the surrounding lowlands. Regional geomorphology studies on both sides of the range correlate various landforms interpreted to be glacial in origin with all each of the eight major Alpine glacial events based largely landscape position, and in some cases geochronologic constraints. This regional relative chronology assumes that wet-based mountain glaciers are efficient agents of erosion and each successive glaciation lowered the valleys within the Tatra. While the tendency of subsequent glaciations to obscure evidence of previous events makes it difficult to study the work done by past glacial episodes, the cave networks on the northern side of the Tatra offer a way to evaluate the amount and timing of valley lowering with U-series dating of speleothems. Epiphreatic and paleophreatic caves that developed near the water table and dried out as valley deepening occurred can serve as excellent recorders of the valley incision history.
Speleothems were collected from a number of cave levels present throughout the northern Tatra, of which only a subset were suitable for U-series geochronology. The oldest speleothems collected in active epiphreatic passages on the valley bottom level from each valley are consistently between 284-325 ka (MIS 8-9). This shows that the modern karst drainage system of the Tatra was established prior to the late Middle Pleistocene, and the cave conduits changed to epiphreatic or vadose conditions between 280 and 330 ka. Since the lowest cave level is at or below the modern valley floor, we can conclude that no valley incision occurred after ~330 ka, which includes both the penultimate and last glaciations periods. Clearly, the regional glacial chronologies in the Tatra must be reassessed. The implications of our findings demonstrate that the assumption of successive valley lowering should not be assumed and that even the extensive MIS2 glaciation did not result in valley lowering despite its size.
How to cite: Szczygieł, J., Hercman, H., Hoke, G., Gąsiorowski, M., Błaszczyk, M., and Sobczyk, A.: Not every large glacial episode lowers valley bottoms: inisghts from the cave systems of the Tatra Mts (the Western Carpathians), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9389, https://doi.org/10.5194/egusphere-egu21-9389, 2021.
EGU21-3702 | vPICO presentations | GM9.12
Climatic controls on mountain glacier basal thermal regimes dictate spatial patterns of glacial erosionJingtao Lai and Alison Anders
The basal thermal regime of glaciers is a first-order control on the spatial patterns of glacial erosion. Polythermal glaciers contain both cold-based portions that protect bedrock from erosion and warm-based portions that actively erode bedrock. Climatic controls on the thermal structures of mountain glaciers and the spatial patterns of glacial erosion has received little study. In this study, we aim to fill this gap by modeling the impact of various climatic conditions on glacier basal thermal regimes and patterns of glacial erosion in mountainous regions. We couple a sliding-dependent glacial erosion model with the Parallel Ice Sheet Model (PISM) to simulate the evolution of the glacier basal thermal regime and glacial erosion in a synthetic landscape. We find that glacial erosion patterns follow the patterns of the basal thermal regime. Cold temperature leads to limited glacial erosion at high elevations due to cold-based conditions. Increasing precipitation could overcome the impact of cold temperature on the basal thermal regime by accumulating thick ice and lowering the melting point of ice at the base of glaciers. High precipitation rates, therefore, tend to cause warm-based conditions at high elevations, resulting in intensive erosion near the peak of the mountain range. Previous studies often assess the impact of climate on the spatial patterns of glacial erosion by integrating climatic conditions into the equilibrium line altitudes (ELAs) of glaciers, and glacial erosion is suggested to be maximal around the ELAs. However, our results show that different climatic conditions could produce glaciers with similar ELAs but different patterns of basal thermal regime and glacial erosion, suggesting that there might not be any direct correlation between ELAs and glacial erosion patterns.
How to cite: Lai, J. and Anders, A.: Climatic controls on mountain glacier basal thermal regimes dictate spatial patterns of glacial erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3702, https://doi.org/10.5194/egusphere-egu21-3702, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The basal thermal regime of glaciers is a first-order control on the spatial patterns of glacial erosion. Polythermal glaciers contain both cold-based portions that protect bedrock from erosion and warm-based portions that actively erode bedrock. Climatic controls on the thermal structures of mountain glaciers and the spatial patterns of glacial erosion has received little study. In this study, we aim to fill this gap by modeling the impact of various climatic conditions on glacier basal thermal regimes and patterns of glacial erosion in mountainous regions. We couple a sliding-dependent glacial erosion model with the Parallel Ice Sheet Model (PISM) to simulate the evolution of the glacier basal thermal regime and glacial erosion in a synthetic landscape. We find that glacial erosion patterns follow the patterns of the basal thermal regime. Cold temperature leads to limited glacial erosion at high elevations due to cold-based conditions. Increasing precipitation could overcome the impact of cold temperature on the basal thermal regime by accumulating thick ice and lowering the melting point of ice at the base of glaciers. High precipitation rates, therefore, tend to cause warm-based conditions at high elevations, resulting in intensive erosion near the peak of the mountain range. Previous studies often assess the impact of climate on the spatial patterns of glacial erosion by integrating climatic conditions into the equilibrium line altitudes (ELAs) of glaciers, and glacial erosion is suggested to be maximal around the ELAs. However, our results show that different climatic conditions could produce glaciers with similar ELAs but different patterns of basal thermal regime and glacial erosion, suggesting that there might not be any direct correlation between ELAs and glacial erosion patterns.
How to cite: Lai, J. and Anders, A.: Climatic controls on mountain glacier basal thermal regimes dictate spatial patterns of glacial erosion, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3702, https://doi.org/10.5194/egusphere-egu21-3702, 2021.
EGU21-13626 | vPICO presentations | GM9.12
The interplay between climate, sea-levels and erosion carved in Baltic rauks - complicated love story from GotlandMateusz C. Strzelecki, Filip Duszyński, Sebastian Tyszkowski, and Łukasz Zbucki
Gotland and its sister island Faro are one of the hidden gems of Baltic Sea rocky coastal landscapes. The most intriguing, both in terms of morphology and evolution, landforms found along local coasts are rauks or raukars. Those limestone (remnants of Silurian reefs) stacks and pinnacles not only tower above present-day rocky shore platforms and beaches but also appear across numerous uplifted marine terraces and inland slopes. Rauks in often occur in groups or fields called raukfält. Surprisingly, those peculiar landforms have been to some extent neglected by geomorphologists and awaited in-depth study of their micro-relief and potential of the well-preserved marine notches to reconstruct past sea-level and environmental conditions operating on rocky coasts over the Holocene. It is important to note that marine notches are commonly treated as one of the best sea-level indicators, as they form close to the local tidal range.
In our paper, we present the results of the most recent mapping of raukars fields in key localities in northern Gotland and Faro including Langhammars, Digerhuvud, Gamla Hamn, Lergrav and Asundens. We measured the shape and elevation of marine notches above present-sea level using Terrestrial Laser Scanning and characterized the degree of weathering of rock surface of raukars bases and well-preserved notches using Schmidt hammer rock tests. In addition to morphometric and geotechnical tests, we monitored modern rates of downwearing of shore platform constitution base of rauks and tops of the local cliffs and rocky escarpments. We discuss the results of selected field surveys with well-established climatic reconstructions and the recently constructed Holocene shore displacement curves of Gotland. We hypothesize that the shape of detected notches not only indicate positions of former sea-levels but also could give us an insight into the differences in the efficiency of erosional and weathering processes operating on rauk surface (notch formation) during periods of different salinity and water temperature, characteristic for Holocene evolution of Baltic Sea.
This is the contribution to the National Science Centre in Poland project ‘RAUK- forgotten witness of Holocene sea-level changes and development of Baltic rocky coasts’ (UMO-2016/21/D/ST10/01976).
How to cite: Strzelecki, M. C., Duszyński, F., Tyszkowski, S., and Zbucki, Ł.: The interplay between climate, sea-levels and erosion carved in Baltic rauks - complicated love story from Gotland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13626, https://doi.org/10.5194/egusphere-egu21-13626, 2021.
Gotland and its sister island Faro are one of the hidden gems of Baltic Sea rocky coastal landscapes. The most intriguing, both in terms of morphology and evolution, landforms found along local coasts are rauks or raukars. Those limestone (remnants of Silurian reefs) stacks and pinnacles not only tower above present-day rocky shore platforms and beaches but also appear across numerous uplifted marine terraces and inland slopes. Rauks in often occur in groups or fields called raukfält. Surprisingly, those peculiar landforms have been to some extent neglected by geomorphologists and awaited in-depth study of their micro-relief and potential of the well-preserved marine notches to reconstruct past sea-level and environmental conditions operating on rocky coasts over the Holocene. It is important to note that marine notches are commonly treated as one of the best sea-level indicators, as they form close to the local tidal range.
In our paper, we present the results of the most recent mapping of raukars fields in key localities in northern Gotland and Faro including Langhammars, Digerhuvud, Gamla Hamn, Lergrav and Asundens. We measured the shape and elevation of marine notches above present-sea level using Terrestrial Laser Scanning and characterized the degree of weathering of rock surface of raukars bases and well-preserved notches using Schmidt hammer rock tests. In addition to morphometric and geotechnical tests, we monitored modern rates of downwearing of shore platform constitution base of rauks and tops of the local cliffs and rocky escarpments. We discuss the results of selected field surveys with well-established climatic reconstructions and the recently constructed Holocene shore displacement curves of Gotland. We hypothesize that the shape of detected notches not only indicate positions of former sea-levels but also could give us an insight into the differences in the efficiency of erosional and weathering processes operating on rauk surface (notch formation) during periods of different salinity and water temperature, characteristic for Holocene evolution of Baltic Sea.
This is the contribution to the National Science Centre in Poland project ‘RAUK- forgotten witness of Holocene sea-level changes and development of Baltic rocky coasts’ (UMO-2016/21/D/ST10/01976).
How to cite: Strzelecki, M. C., Duszyński, F., Tyszkowski, S., and Zbucki, Ł.: The interplay between climate, sea-levels and erosion carved in Baltic rauks - complicated love story from Gotland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13626, https://doi.org/10.5194/egusphere-egu21-13626, 2021.
EGU21-9231 | vPICO presentations | GM9.12
Patchy bedrock explained: Tectonic fracture control on landscape evolution patterns in south-Central ChileEmma Lodes, Dirk Scherler, Hella Wittmann, and Renee Van Dongen
Rock fracturing induced by tectonic deformation is thought to promote faster denudation in more highly fractured areas by lowering grain size and directing the flow of water. That the density and pattern of fractures in a landscape play a role in controlling erosion and landscape evolution has been known for over a century, but not until recently do we have tools, like cosmogenic nuclides, to quantify erosion rates in places with varying fracture densities. In the Nahuelbuta Range in south-central Chile, we observed that >30-m thick regolith exists next to patches of unweathered bedrock. We hypothesize that the density of fractures dictates the pace and patterns of chemical weathering, regolith conversion, and erosion in the Nahuelbuta Range. To test this, we used in situ cosmogenic 10Be to obtain denudation rates from amalgamated samples of bedrock, corestones and soils, and measured fracture density and orientation, as well as hillslope boulder size in several sites in the Nahuelbuta Range. We found that more highly fractured areas indeed have higher denudation rates than less fractured areas, and that bedrock denudation rates are ~10 m/Myr while soil denudation rates are ~30 m/Myr, suggesting that soil-covered areas may be sites of higher fracture density at depth. Fractures have orientations that match mapped faults across the Nahuelbuta range, and thus are considered to be tectonically-induced. In addition, both fracture and fault orientations match the orientation of streams incising the range, suggesting that fractures control stream channel orientation by weakening bedrock and thus directing flow.
How to cite: Lodes, E., Scherler, D., Wittmann, H., and Van Dongen, R.: Patchy bedrock explained: Tectonic fracture control on landscape evolution patterns in south-Central Chile , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9231, https://doi.org/10.5194/egusphere-egu21-9231, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Rock fracturing induced by tectonic deformation is thought to promote faster denudation in more highly fractured areas by lowering grain size and directing the flow of water. That the density and pattern of fractures in a landscape play a role in controlling erosion and landscape evolution has been known for over a century, but not until recently do we have tools, like cosmogenic nuclides, to quantify erosion rates in places with varying fracture densities. In the Nahuelbuta Range in south-central Chile, we observed that >30-m thick regolith exists next to patches of unweathered bedrock. We hypothesize that the density of fractures dictates the pace and patterns of chemical weathering, regolith conversion, and erosion in the Nahuelbuta Range. To test this, we used in situ cosmogenic 10Be to obtain denudation rates from amalgamated samples of bedrock, corestones and soils, and measured fracture density and orientation, as well as hillslope boulder size in several sites in the Nahuelbuta Range. We found that more highly fractured areas indeed have higher denudation rates than less fractured areas, and that bedrock denudation rates are ~10 m/Myr while soil denudation rates are ~30 m/Myr, suggesting that soil-covered areas may be sites of higher fracture density at depth. Fractures have orientations that match mapped faults across the Nahuelbuta range, and thus are considered to be tectonically-induced. In addition, both fracture and fault orientations match the orientation of streams incising the range, suggesting that fractures control stream channel orientation by weakening bedrock and thus directing flow.
How to cite: Lodes, E., Scherler, D., Wittmann, H., and Van Dongen, R.: Patchy bedrock explained: Tectonic fracture control on landscape evolution patterns in south-Central Chile , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9231, https://doi.org/10.5194/egusphere-egu21-9231, 2021.
EGU21-9886 | vPICO presentations | GM9.12
Studying bedrock fracture and weathering patterns with cosmic-ray induced muon particlesMarko Holma, Pertti Sarala, Adrian M. Hall, Pasi Kuusiniemi, Hiroyuki K.M. Tanaka, and Deszo Varga
Subsurface fracturing and weathering in bedrock are typically studied and imaged with conventional remote geophysical techniques. We introduce a new technique, muography, for carrying out such studies. This technique is based on the detection of atmospheric cosmic-ray induced muon particles after they pass through rock. The method plots the attenuation of muon flux in materials of different thickness and density (simply, dense materials “stop” more muons). The raw muon flux is translated into 2D images and 3D models showing variations in mean densities in a visually meaningful manner. As a rule of thumb, a 1% density difference between two rock bodies yields approximately 3% difference in the respective muon fluxes. The muographic density maps cover the Volume of Interest (VOI) that is located between the muon detector(s) and the source of muons (sky). Hence, the detector must be installed behind the VOI. Appropriate settings for muography include the sides of mountains, hills, cliffs and gorges, and in tunnels or boreholes below the ground surface.
Muography provides an interesting new opportunity to study and remotely image subsurface fracturing and weathering. Understanding fracturing and weathering is important as they control, for example, erosion, soil formation, the stability of rock and soil slopes, and stability of tunnels. Weathering also has a link to past climates, palaeogeographic reconstructions, and natural geochemical cycles. Weathered bedrock is also a target for mineral exploration. Due to these reasons, we are planning field surveys in northern Finland. These surveys are also used for fine-tuning the muon detector’s operational parameters and to improve its current design to cope with operating conditions in the Arctic. The survey area around Vuotso lies within the ice-divide zone of the Fennoscandian ice sheet, a zone of low glacial erosion through the Pleistocene. We have identified two survey targets: (i) a tor-studded granite dome at Riestovaara, with extensive granite outcrops that show curved sheet joints and (ii) Mäkärä, a rare-earth mineral prospect in the Tana Belt where amphibolites and garnet–biotite gneisses are covered by thick kaolinitic saprolites of pre-Pleistocene age and overlain by clay-rich till enriched in La and Y. Reconnaissance muon surveys across these contrasting terrains can be calibrated against a wealth of existing GTK data from field mapping and boreholes. The muon survey aims to provide important new subsurface information on fracture patterns at depth on the Riestovaara dome and on deep weathering patterns at Mäkärä. Muography has potential to become a fundamental tool for low-cost subsurface surveying, with applications in geomorphology, mineral exploration, and civil and mining engineering.
How to cite: Holma, M., Sarala, P., Hall, A. M., Kuusiniemi, P., Tanaka, H. K. M., and Varga, D.: Studying bedrock fracture and weathering patterns with cosmic-ray induced muon particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9886, https://doi.org/10.5194/egusphere-egu21-9886, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Subsurface fracturing and weathering in bedrock are typically studied and imaged with conventional remote geophysical techniques. We introduce a new technique, muography, for carrying out such studies. This technique is based on the detection of atmospheric cosmic-ray induced muon particles after they pass through rock. The method plots the attenuation of muon flux in materials of different thickness and density (simply, dense materials “stop” more muons). The raw muon flux is translated into 2D images and 3D models showing variations in mean densities in a visually meaningful manner. As a rule of thumb, a 1% density difference between two rock bodies yields approximately 3% difference in the respective muon fluxes. The muographic density maps cover the Volume of Interest (VOI) that is located between the muon detector(s) and the source of muons (sky). Hence, the detector must be installed behind the VOI. Appropriate settings for muography include the sides of mountains, hills, cliffs and gorges, and in tunnels or boreholes below the ground surface.
Muography provides an interesting new opportunity to study and remotely image subsurface fracturing and weathering. Understanding fracturing and weathering is important as they control, for example, erosion, soil formation, the stability of rock and soil slopes, and stability of tunnels. Weathering also has a link to past climates, palaeogeographic reconstructions, and natural geochemical cycles. Weathered bedrock is also a target for mineral exploration. Due to these reasons, we are planning field surveys in northern Finland. These surveys are also used for fine-tuning the muon detector’s operational parameters and to improve its current design to cope with operating conditions in the Arctic. The survey area around Vuotso lies within the ice-divide zone of the Fennoscandian ice sheet, a zone of low glacial erosion through the Pleistocene. We have identified two survey targets: (i) a tor-studded granite dome at Riestovaara, with extensive granite outcrops that show curved sheet joints and (ii) Mäkärä, a rare-earth mineral prospect in the Tana Belt where amphibolites and garnet–biotite gneisses are covered by thick kaolinitic saprolites of pre-Pleistocene age and overlain by clay-rich till enriched in La and Y. Reconnaissance muon surveys across these contrasting terrains can be calibrated against a wealth of existing GTK data from field mapping and boreholes. The muon survey aims to provide important new subsurface information on fracture patterns at depth on the Riestovaara dome and on deep weathering patterns at Mäkärä. Muography has potential to become a fundamental tool for low-cost subsurface surveying, with applications in geomorphology, mineral exploration, and civil and mining engineering.
How to cite: Holma, M., Sarala, P., Hall, A. M., Kuusiniemi, P., Tanaka, H. K. M., and Varga, D.: Studying bedrock fracture and weathering patterns with cosmic-ray induced muon particles, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9886, https://doi.org/10.5194/egusphere-egu21-9886, 2021.
EGU21-1235 | vPICO presentations | GM9.12
Mo mobility in lateritic weathering profiles overlying ultramafic rocks of the East Sulawesi Ophiolite, IndonesiaAdrianus Damanik, Martin Wille, Martin Grosjean, Sri Yudawati Cahyarini, and Hendrik Vogel
Molybdenum (Mo) isotopes are known as sensitive recorders for changes in redox conditions because the oxidized form of Mo (Mo VI) is more soluble, whereas its reduced form is more particle reactive. Previous studies suggest that Mo isotopic fractionation during the weathering process is controlled by atmospheric input, Mo host, and bedrock composition. However, Mo isotopic variation and processes influencing fractionation in weathering profiles overlying ultramafic bedrock, the early Earth analog, have yet to be explored. This study explores for the first time (1) Mo behavior and (2) isotopic fractionation in two representative and intensely-weathered lateritic profiles overlying ultramafic bedrock of the East Sulawesi Ophiolite, Indonesia. Mo concentrations measured on samples obtained from laterite successions studied here range between 60 - 537 ppb and are overall higher compared to bedrock values ranging between 9 - 45 ppb. The Mo isotope compositions of laterite samples vary between -0.043‰ to -0.161‰ δ98MoNIST3134. The overall close to mantle Mo isotopic composition of the laterite samples, their small Mo isotope variability, and the covariation between Mo and Ti concentrations suggest low mobility of Mo during chemical weathering and laterite formation. This low Mo mobility is likely a consequence of a) the low Mo concentration of the ultramafic protolith and b) adsorption of Mo to secondary Fe-Oxides during laterite formation under oxic weathering conditions.
How to cite: Damanik, A., Wille, M., Grosjean, M., Cahyarini, S. Y., and Vogel, H.: Mo mobility in lateritic weathering profiles overlying ultramafic rocks of the East Sulawesi Ophiolite, Indonesia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1235, https://doi.org/10.5194/egusphere-egu21-1235, 2021.
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Molybdenum (Mo) isotopes are known as sensitive recorders for changes in redox conditions because the oxidized form of Mo (Mo VI) is more soluble, whereas its reduced form is more particle reactive. Previous studies suggest that Mo isotopic fractionation during the weathering process is controlled by atmospheric input, Mo host, and bedrock composition. However, Mo isotopic variation and processes influencing fractionation in weathering profiles overlying ultramafic bedrock, the early Earth analog, have yet to be explored. This study explores for the first time (1) Mo behavior and (2) isotopic fractionation in two representative and intensely-weathered lateritic profiles overlying ultramafic bedrock of the East Sulawesi Ophiolite, Indonesia. Mo concentrations measured on samples obtained from laterite successions studied here range between 60 - 537 ppb and are overall higher compared to bedrock values ranging between 9 - 45 ppb. The Mo isotope compositions of laterite samples vary between -0.043‰ to -0.161‰ δ98MoNIST3134. The overall close to mantle Mo isotopic composition of the laterite samples, their small Mo isotope variability, and the covariation between Mo and Ti concentrations suggest low mobility of Mo during chemical weathering and laterite formation. This low Mo mobility is likely a consequence of a) the low Mo concentration of the ultramafic protolith and b) adsorption of Mo to secondary Fe-Oxides during laterite formation under oxic weathering conditions.
How to cite: Damanik, A., Wille, M., Grosjean, M., Cahyarini, S. Y., and Vogel, H.: Mo mobility in lateritic weathering profiles overlying ultramafic rocks of the East Sulawesi Ophiolite, Indonesia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1235, https://doi.org/10.5194/egusphere-egu21-1235, 2021.
EGU21-12398 | vPICO presentations | GM9.12
The late-Holocene records of sediment provenance/weathering in the Wular Lake catchment, Northwest HimalayaNafees Ahmad, Satinder Pal Singh, and Aasif Mohmad Lone
The Wular Lake (area ~189 km2) in the Kashmir Valley (area ~16,000 km2) is fed by the Jhelum River, which is a large Himalayan tributary of the Indus River. The lake catchment seasonally receives precipitation from tropical (Indian Summer Monsoon, ISM) and subtropical (Western Disturbances, WD) moisture sources. Thus, the lake sediments provide a unique opportunity to explore the high-resolution archive of the synoptic-scale weathering intensity and pattern in the Northwest Himalaya under past hydroclimatic conditions. In this study, radiogenic Sr and Nd isotope compositions and lithic fractions (sand, silt, and clay) have been determined on detrital phases of a 2.2 m long sediment core retrieved from the Wular Lake. The 14C-AMS chronology of this core presents the sedimentary records of the last 4.2 ka. The Sr and Nd isotope data indicate that the lake sediments deposited during the late-Holocene are mostly sourced from the Tethyan Himalaya rather than other major lithologies. The marginal downcore variations of ±1.5 εNd unit (except two anomalous datapoints with large uncertainties at 0.8 ka and 2.0 ka) reveal no major shifts in the sediment provenance during the late-Holocene. On the other hand, the significant downcore variations are observed in 87Sr/86Sr (>0.001–0.004) showing well-resolved periods of higher and lower values than the late-Holocene average. The 87Sr/86Sr data unbiased by the grain-size sorting and carbonate contents seem to indicate a temporal dominance of chemical and physical modes of silicate weathering in the Northwest Himalaya before and after ~2 ka, respectively. Interestingly, an abrupt shift in the 87Sr/86Sr data during the Little Ice Age (~0.4–0.1 ka) reveals a multi-decadal response of the silicate weathering intensity in synchrony with the northern hemisphere temperature anomaly.
How to cite: Ahmad, N., Singh, S. P., and Lone, A. M.: The late-Holocene records of sediment provenance/weathering in the Wular Lake catchment, Northwest Himalaya, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12398, https://doi.org/10.5194/egusphere-egu21-12398, 2021.
The Wular Lake (area ~189 km2) in the Kashmir Valley (area ~16,000 km2) is fed by the Jhelum River, which is a large Himalayan tributary of the Indus River. The lake catchment seasonally receives precipitation from tropical (Indian Summer Monsoon, ISM) and subtropical (Western Disturbances, WD) moisture sources. Thus, the lake sediments provide a unique opportunity to explore the high-resolution archive of the synoptic-scale weathering intensity and pattern in the Northwest Himalaya under past hydroclimatic conditions. In this study, radiogenic Sr and Nd isotope compositions and lithic fractions (sand, silt, and clay) have been determined on detrital phases of a 2.2 m long sediment core retrieved from the Wular Lake. The 14C-AMS chronology of this core presents the sedimentary records of the last 4.2 ka. The Sr and Nd isotope data indicate that the lake sediments deposited during the late-Holocene are mostly sourced from the Tethyan Himalaya rather than other major lithologies. The marginal downcore variations of ±1.5 εNd unit (except two anomalous datapoints with large uncertainties at 0.8 ka and 2.0 ka) reveal no major shifts in the sediment provenance during the late-Holocene. On the other hand, the significant downcore variations are observed in 87Sr/86Sr (>0.001–0.004) showing well-resolved periods of higher and lower values than the late-Holocene average. The 87Sr/86Sr data unbiased by the grain-size sorting and carbonate contents seem to indicate a temporal dominance of chemical and physical modes of silicate weathering in the Northwest Himalaya before and after ~2 ka, respectively. Interestingly, an abrupt shift in the 87Sr/86Sr data during the Little Ice Age (~0.4–0.1 ka) reveals a multi-decadal response of the silicate weathering intensity in synchrony with the northern hemisphere temperature anomaly.
How to cite: Ahmad, N., Singh, S. P., and Lone, A. M.: The late-Holocene records of sediment provenance/weathering in the Wular Lake catchment, Northwest Himalaya, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12398, https://doi.org/10.5194/egusphere-egu21-12398, 2021.
EGU21-11995 | vPICO presentations | GM9.12
Continental weathering using combined Hf-Nd isotope system and clay mineralogy: new insights for the Late Cretaceous climatePauline Corentin, Emmanuelle Puceat, Pierre Pellenard, Nicolas Freslon, Michel Guiraud, Justine Blondet, Thierry Adatte, and Germain Bayon
The Late Cretaceous period records a pronounced decrease in marine temperatures at a global scale initiating the last greenhouse-icehouse transition, whose origin still remains enigmatic. Continental weathering represents a major sink of atmospheric CO2 through silicate weathering reactions yet the importance of this process in the Late Cretaceous cooling has only been scarcely explored.
In this study we explore the impact of the eastern South American margin uplift, concomitant to the long-term Late Cretaceous cooling, on the evolution of chemical weathering of the Brazilian margin, using a new proxy of silicate weathering based on the coupled Lu-Hf and Sm-Nd isotope systems in clays. This proxy, expressed as ΔεHf, has been recently calibrated in modern environments (Bayon et al., 2016) but has only been scarcely applied to deep-time environments. This proxy, applied on sediments from DSDP site 356 on the São Paulo Plateau, highlights a marked increase in silicate chemical weathering of the southeastern Brazilian margin from the Santonian to the Maastrichtian, also supported by the evolution of the chemical index of alteration (CIA) and clay mineralogy.
This increase follows an episode of enhanced mechanical erosion of the margin revealed in the Turonian to Santonian by an increase of primary clay mineral (illite, chlorite) and Ti/Al ratio, linked to the tectonic uplift of the margin. Clay mineral assemblages additionally point to an evolution of local climatic conditions from arid to a more hydrolysing climate following this episode, that we link to a “rain shadow effect” affecting the eastern side of the newly formed relief that would have enhanced chemical weathering of the margin.
Importantly the temporal coincidence of the increase in chemical weathering depicted here with the marked acceleration of the global cooling recorded worldwide during the Campanian points to a potentially important role of this process on the overall climate decline initiating the descent into our icehouse climate mode. Although records from additional sites are needed to establish the spatial extent of the margin affected by this process, our new dataset brings new insights about the impact of tectonic forcing on climate.
Bayon et al. (2016) EPSL 438, p. 25-36.
How to cite: Corentin, P., Puceat, E., Pellenard, P., Freslon, N., Guiraud, M., Blondet, J., Adatte, T., and Bayon, G.: Continental weathering using combined Hf-Nd isotope system and clay mineralogy: new insights for the Late Cretaceous climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11995, https://doi.org/10.5194/egusphere-egu21-11995, 2021.
The Late Cretaceous period records a pronounced decrease in marine temperatures at a global scale initiating the last greenhouse-icehouse transition, whose origin still remains enigmatic. Continental weathering represents a major sink of atmospheric CO2 through silicate weathering reactions yet the importance of this process in the Late Cretaceous cooling has only been scarcely explored.
In this study we explore the impact of the eastern South American margin uplift, concomitant to the long-term Late Cretaceous cooling, on the evolution of chemical weathering of the Brazilian margin, using a new proxy of silicate weathering based on the coupled Lu-Hf and Sm-Nd isotope systems in clays. This proxy, expressed as ΔεHf, has been recently calibrated in modern environments (Bayon et al., 2016) but has only been scarcely applied to deep-time environments. This proxy, applied on sediments from DSDP site 356 on the São Paulo Plateau, highlights a marked increase in silicate chemical weathering of the southeastern Brazilian margin from the Santonian to the Maastrichtian, also supported by the evolution of the chemical index of alteration (CIA) and clay mineralogy.
This increase follows an episode of enhanced mechanical erosion of the margin revealed in the Turonian to Santonian by an increase of primary clay mineral (illite, chlorite) and Ti/Al ratio, linked to the tectonic uplift of the margin. Clay mineral assemblages additionally point to an evolution of local climatic conditions from arid to a more hydrolysing climate following this episode, that we link to a “rain shadow effect” affecting the eastern side of the newly formed relief that would have enhanced chemical weathering of the margin.
Importantly the temporal coincidence of the increase in chemical weathering depicted here with the marked acceleration of the global cooling recorded worldwide during the Campanian points to a potentially important role of this process on the overall climate decline initiating the descent into our icehouse climate mode. Although records from additional sites are needed to establish the spatial extent of the margin affected by this process, our new dataset brings new insights about the impact of tectonic forcing on climate.
Bayon et al. (2016) EPSL 438, p. 25-36.
How to cite: Corentin, P., Puceat, E., Pellenard, P., Freslon, N., Guiraud, M., Blondet, J., Adatte, T., and Bayon, G.: Continental weathering using combined Hf-Nd isotope system and clay mineralogy: new insights for the Late Cretaceous climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11995, https://doi.org/10.5194/egusphere-egu21-11995, 2021.
EGU21-14888 | vPICO presentations | GM9.12 | Highlight
Increased land surface reactivity as the driver of Neogene coolingFriedhelm von Blanckenburg, Jeremy K. Caves-Rugenstein, and Daniel E. Ibarra
Long-term cooling, pCO2 decline, and the establishment of permanent, polar ice sheets in the Neogenehas frequently been attributed to increased uplift and erosion of mountains and consequent increases in silicate weathering, which removes atmospheric CO2. However, an increasing weathering flux is incompatible with a balanced atmospheric CO2budget [1]. For example, a weathering increase scaled to frequently invoked erosional increase [2] would have removed nearly all carbon from the atmosphere. Further, the marine 10Be/9Be proxy indicates constant silicate weathering fluxes over the past 10 Ma [3].
Rather, as volcanic CO2 emissions have been largely constant yet atmospheric CO2 decreased, as indicated by the marine 11B/10B proxy, an increase in “land surface reactivity” has likely driven global cooling [4]. Land surface reactivity quantifies the likelihood of weathering zone material to react with carbon derived from atmospheric CO2 and represents the degree of coupling between weathering and climate. That surface reactivity has increased during the Neogene is confirmed by the stable 7Li/6Li seawater proxy, which increases during the Neogene. The question we now need to address is thus: what has caused the increase in land surface reactivity? What is needed is an increased availability of Ca and Mg-rich primary minerals in the global critical zone. This could have come about by 1) an increased exposure of mafic volcanic rock; 2) supply of fresh glacial debris; 3) widespread rejuvenation of the continental land surface by faulting; 4) more efficient mineral dissolution by biota; or 5) an increase in erosion rate with or without mountain uplift. Only explanation 1) can be discounted as this hypothesis fails to satisfy the marine Sr and Os radiogenic isotope records. Explanations 2 – 5 remain. In all of these the role of erosion is to remove weathered material. Indeed, parsimonious geochemical models are roughly compatible with a doubling in global erosional mass flux since 10 Ma [1].
(1) Caves Rugenstein, J.K., D.E. Ibarra, and F. von Blanckenburg, Neogene cooling driven by land surface reactivity rather than increased weathering fluxes. Nature, 2019.
(2) Molnar, P., Late Cenozoic increase in accumulation rates of terrestrial sediment: how might climate change have affected erosion rates? Ann. Rev. Earth Planet. Sc., 2004.
(3) Willenbring, J.K. and F. von Blanckenburg, Long-term stability of global erosion rates and weathering during late-Cenozoic cooling. Nature, 2010.
(4) Kump, L.R. and M.A. Arthur, Global chemical erosion during the Cenozoic: Weatherability balances the budgets, in Tectonic Uplift and Climate Change. 1997.
How to cite: von Blanckenburg, F., Caves-Rugenstein, J. K., and Ibarra, D. E.: Increased land surface reactivity as the driver of Neogene cooling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14888, https://doi.org/10.5194/egusphere-egu21-14888, 2021.
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Long-term cooling, pCO2 decline, and the establishment of permanent, polar ice sheets in the Neogenehas frequently been attributed to increased uplift and erosion of mountains and consequent increases in silicate weathering, which removes atmospheric CO2. However, an increasing weathering flux is incompatible with a balanced atmospheric CO2budget [1]. For example, a weathering increase scaled to frequently invoked erosional increase [2] would have removed nearly all carbon from the atmosphere. Further, the marine 10Be/9Be proxy indicates constant silicate weathering fluxes over the past 10 Ma [3].
Rather, as volcanic CO2 emissions have been largely constant yet atmospheric CO2 decreased, as indicated by the marine 11B/10B proxy, an increase in “land surface reactivity” has likely driven global cooling [4]. Land surface reactivity quantifies the likelihood of weathering zone material to react with carbon derived from atmospheric CO2 and represents the degree of coupling between weathering and climate. That surface reactivity has increased during the Neogene is confirmed by the stable 7Li/6Li seawater proxy, which increases during the Neogene. The question we now need to address is thus: what has caused the increase in land surface reactivity? What is needed is an increased availability of Ca and Mg-rich primary minerals in the global critical zone. This could have come about by 1) an increased exposure of mafic volcanic rock; 2) supply of fresh glacial debris; 3) widespread rejuvenation of the continental land surface by faulting; 4) more efficient mineral dissolution by biota; or 5) an increase in erosion rate with or without mountain uplift. Only explanation 1) can be discounted as this hypothesis fails to satisfy the marine Sr and Os radiogenic isotope records. Explanations 2 – 5 remain. In all of these the role of erosion is to remove weathered material. Indeed, parsimonious geochemical models are roughly compatible with a doubling in global erosional mass flux since 10 Ma [1].
(1) Caves Rugenstein, J.K., D.E. Ibarra, and F. von Blanckenburg, Neogene cooling driven by land surface reactivity rather than increased weathering fluxes. Nature, 2019.
(2) Molnar, P., Late Cenozoic increase in accumulation rates of terrestrial sediment: how might climate change have affected erosion rates? Ann. Rev. Earth Planet. Sc., 2004.
(3) Willenbring, J.K. and F. von Blanckenburg, Long-term stability of global erosion rates and weathering during late-Cenozoic cooling. Nature, 2010.
(4) Kump, L.R. and M.A. Arthur, Global chemical erosion during the Cenozoic: Weatherability balances the budgets, in Tectonic Uplift and Climate Change. 1997.
How to cite: von Blanckenburg, F., Caves-Rugenstein, J. K., and Ibarra, D. E.: Increased land surface reactivity as the driver of Neogene cooling, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14888, https://doi.org/10.5194/egusphere-egu21-14888, 2021.
EGU21-2264 | vPICO presentations | GM9.12
Ocean alkalinity enhancement as a tool to mitigate ocean acidification and facilitate CO2 uptake from the atmosphereJakob Rønning and Carolin Löscher
Anthropogenic global warming over the last century has led to a steady increase of CO2 in the atmosphere. One of the consequences of increasing CO2 concentrations is ocean acidification, a phenomenon problematic to marine biodiversity and biogeochemistry. The ocean reservoir takes up 25% of CO2 from the atmosphere both chemically and biologically. This potential can be made use of to promote CO2 uptake from the atmosphere while mitigating ocean acidification and protecting biodiversity using negative emission technologies associated with the ocean. We have investigated the potential of various alkaline minerals to stabilize seawater pH overtime on a small scale. Those alkaline minerals were predicted to be appropriate for ocean alkalinity enhancement and can offer a toolset to mitigate CO2 from the atmosphere. Specifically, we have examined how chalk, calcite, dolomite, limestone, and olivine affects seawater pH and total alkalinity (TA) on timescales of several months. Thereby, we could identify two promising minerals, dolomite and olivine, and develop a strategy for mineral additions to buffer the seawater pH. Importantly, the often proposed had an unexpected opposite impact and massively lowered the seawater pH over a timescale of 100 days. The identified advantageous minerals will inform our experiments on primary producer cultures and natural consortia.
How to cite: Rønning, J. and Löscher, C.: Ocean alkalinity enhancement as a tool to mitigate ocean acidification and facilitate CO2 uptake from the atmosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2264, https://doi.org/10.5194/egusphere-egu21-2264, 2021.
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Anthropogenic global warming over the last century has led to a steady increase of CO2 in the atmosphere. One of the consequences of increasing CO2 concentrations is ocean acidification, a phenomenon problematic to marine biodiversity and biogeochemistry. The ocean reservoir takes up 25% of CO2 from the atmosphere both chemically and biologically. This potential can be made use of to promote CO2 uptake from the atmosphere while mitigating ocean acidification and protecting biodiversity using negative emission technologies associated with the ocean. We have investigated the potential of various alkaline minerals to stabilize seawater pH overtime on a small scale. Those alkaline minerals were predicted to be appropriate for ocean alkalinity enhancement and can offer a toolset to mitigate CO2 from the atmosphere. Specifically, we have examined how chalk, calcite, dolomite, limestone, and olivine affects seawater pH and total alkalinity (TA) on timescales of several months. Thereby, we could identify two promising minerals, dolomite and olivine, and develop a strategy for mineral additions to buffer the seawater pH. Importantly, the often proposed had an unexpected opposite impact and massively lowered the seawater pH over a timescale of 100 days. The identified advantageous minerals will inform our experiments on primary producer cultures and natural consortia.
How to cite: Rønning, J. and Löscher, C.: Ocean alkalinity enhancement as a tool to mitigate ocean acidification and facilitate CO2 uptake from the atmosphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2264, https://doi.org/10.5194/egusphere-egu21-2264, 2021.
GM9.14 – Investigating deep-Earth dynamics through time and space using surface observations.
EGU21-13996 | vPICO presentations | GM9.14
Linking exhumation, paleo-relief, and rift formation to magmatic processes in the Western Snake River Plain, IdahoJessica Stanley and Kelsey Wetzel
Southwest Idaho has experienced substantial topographic changes over the Cenozoic that are reflections of complex tectonic and mantle processes. The western Snake River Plain (WSRP) in southwest Idaho has been characterized as an intracontinental rift basin but differs markedly in topography and style from other western Cordilleran extensional structures. It also differs in orientation and structural style from the down warped lava plain of the eastern Snake River Plain that follows the path of the Yellowstone hotspot (YHS). Potential magmatic drivers for WSRP formation include the ~12-10 Ma Bruneau-Jarbidge eruptive center of the YHS or the ~17-16 Ma Columbia River Basalt (CRB) large igneous province. To better constrain the timing and style of rifting in the region we sampled granitoid bedrock from Cretaceous and Eocene-aged plutons from the flanks of the WSRP to detail their exhumation history with apatite (U-Th)/He (AHe) thermochronometry. We present new AHe dates from seventeen samples, with cooling dates ranging range from 7 Ma to 55 Ma. The majority of cooling dates for the Cretaceous plutons are Eocene, and the Eocene intrusions yield Miocene dates. The AHe dates provide thermochronological evidence of rapid cooling and exhumation of the Idaho batholith during the Eocene. This supports the presence a high relief landscape in Idaho associated with regional uplift due to Farallon slab rollback and Challis magmatism. We also find evidence for a post-Eocene decrease in relief, seen in the negative slope on date-elevation relationships in the southwest flank of the WSRP. Our AHe dates indicate limited exhumation on the flanks of the WSRP during Miocene rift formation. We interpret this to be evidence of extension dominated by magmatic intrusions and intrabasin faults rather than basin-bounding faults. Miocene AHe dates show rapid exhumation along the Middle Fork Boise River that had begun by ~17 Ma. We take this to indicate focused incision along the river due to base level fall in the WSRP and the timing suggests that CRB activity was responsible for initiation of WSRP formation
How to cite: Stanley, J. and Wetzel, K.: Linking exhumation, paleo-relief, and rift formation to magmatic processes in the Western Snake River Plain, Idaho, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13996, https://doi.org/10.5194/egusphere-egu21-13996, 2021.
Southwest Idaho has experienced substantial topographic changes over the Cenozoic that are reflections of complex tectonic and mantle processes. The western Snake River Plain (WSRP) in southwest Idaho has been characterized as an intracontinental rift basin but differs markedly in topography and style from other western Cordilleran extensional structures. It also differs in orientation and structural style from the down warped lava plain of the eastern Snake River Plain that follows the path of the Yellowstone hotspot (YHS). Potential magmatic drivers for WSRP formation include the ~12-10 Ma Bruneau-Jarbidge eruptive center of the YHS or the ~17-16 Ma Columbia River Basalt (CRB) large igneous province. To better constrain the timing and style of rifting in the region we sampled granitoid bedrock from Cretaceous and Eocene-aged plutons from the flanks of the WSRP to detail their exhumation history with apatite (U-Th)/He (AHe) thermochronometry. We present new AHe dates from seventeen samples, with cooling dates ranging range from 7 Ma to 55 Ma. The majority of cooling dates for the Cretaceous plutons are Eocene, and the Eocene intrusions yield Miocene dates. The AHe dates provide thermochronological evidence of rapid cooling and exhumation of the Idaho batholith during the Eocene. This supports the presence a high relief landscape in Idaho associated with regional uplift due to Farallon slab rollback and Challis magmatism. We also find evidence for a post-Eocene decrease in relief, seen in the negative slope on date-elevation relationships in the southwest flank of the WSRP. Our AHe dates indicate limited exhumation on the flanks of the WSRP during Miocene rift formation. We interpret this to be evidence of extension dominated by magmatic intrusions and intrabasin faults rather than basin-bounding faults. Miocene AHe dates show rapid exhumation along the Middle Fork Boise River that had begun by ~17 Ma. We take this to indicate focused incision along the river due to base level fall in the WSRP and the timing suggests that CRB activity was responsible for initiation of WSRP formation
How to cite: Stanley, J. and Wetzel, K.: Linking exhumation, paleo-relief, and rift formation to magmatic processes in the Western Snake River Plain, Idaho, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13996, https://doi.org/10.5194/egusphere-egu21-13996, 2021.
EGU21-10257 | vPICO presentations | GM9.14 | Highlight
The Global Heat Flow Database: a collaborative and fundamental revision process to ensure comprehensible and reliable heat-flow recordsSven Fuchs, Graeme Beardsmore, Paolo Chiozzi, Orlando Miguel Espinoza-Ojeda, Gianluca Gola, Will Gosnold, Robert Harris, Sam Jennings, 'Shaowen Liu, Raquel Negrete-Aranda, Florian Neumann, Ben Norden, Jeffrey Poort, Dušan Rajver, Labani Ray, Maria Richards, Jared Smith, Akiko Tanaka, and Massimo Verdoya
The compilation of global heat-flow data is currently under major revision by the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). Heat flow represents a fundamental parameter in thermal studies, e.g., the evolution of hydrocarbons or mineral and geothermal resources. Comparable, comprehensible and reliable heat-flow data are of utmost interest also for geophysical and geological studies on the global scale. Here, we present the first results of a stepwise revision of the IHFC Global Heat Flow Database based on a researcher driven, collaborative approach. The first step comprises the review and revision of the most recent database structure established in 1976. The revised structure of the Global Heat Flow Database considers the demands and opportunities presented by the evolution of scientific work, digitization and the breakthroughs in database technologies over the past decades. Based on the new structure, the existing dataset will be re-assessed and new data incorporated. By supporting the ideas of FAIR and open data principles, the new database facilitates interoperability with external data services, like DOI and IGSN numbers, and other data resources (e.g., world geological map, world stratigraphic system, and International Ocean Drilling Program data). We give an overview of the new database and introduce the community workflow of global heat-flow data revision.
How to cite: Fuchs, S., Beardsmore, G., Chiozzi, P., Espinoza-Ojeda, O. M., Gola, G., Gosnold, W., Harris, R., Jennings, S., Liu, '., Negrete-Aranda, R., Neumann, F., Norden, B., Poort, J., Rajver, D., Ray, L., Richards, M., Smith, J., Tanaka, A., and Verdoya, M.: The Global Heat Flow Database: a collaborative and fundamental revision process to ensure comprehensible and reliable heat-flow records, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10257, https://doi.org/10.5194/egusphere-egu21-10257, 2021.
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The compilation of global heat-flow data is currently under major revision by the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). Heat flow represents a fundamental parameter in thermal studies, e.g., the evolution of hydrocarbons or mineral and geothermal resources. Comparable, comprehensible and reliable heat-flow data are of utmost interest also for geophysical and geological studies on the global scale. Here, we present the first results of a stepwise revision of the IHFC Global Heat Flow Database based on a researcher driven, collaborative approach. The first step comprises the review and revision of the most recent database structure established in 1976. The revised structure of the Global Heat Flow Database considers the demands and opportunities presented by the evolution of scientific work, digitization and the breakthroughs in database technologies over the past decades. Based on the new structure, the existing dataset will be re-assessed and new data incorporated. By supporting the ideas of FAIR and open data principles, the new database facilitates interoperability with external data services, like DOI and IGSN numbers, and other data resources (e.g., world geological map, world stratigraphic system, and International Ocean Drilling Program data). We give an overview of the new database and introduce the community workflow of global heat-flow data revision.
How to cite: Fuchs, S., Beardsmore, G., Chiozzi, P., Espinoza-Ojeda, O. M., Gola, G., Gosnold, W., Harris, R., Jennings, S., Liu, '., Negrete-Aranda, R., Neumann, F., Norden, B., Poort, J., Rajver, D., Ray, L., Richards, M., Smith, J., Tanaka, A., and Verdoya, M.: The Global Heat Flow Database: a collaborative and fundamental revision process to ensure comprehensible and reliable heat-flow records, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10257, https://doi.org/10.5194/egusphere-egu21-10257, 2021.
EGU21-591 | vPICO presentations | GM9.14
Climatic control on the Southern Andean volcanic arc locationVeleda Astarte Paiva Muller, Pietro Sternai, and Christian Sue
The Southern Andes Volcanic zone (SVZ) is located between latitudes 33-46°S in the western margin of the South American continental plate, above the subducting Nazca oceanic plate. Although the slab dip angle is constant (~25°) along strike, the distance between the volcanic arc and the subduction trench decreases southward. In the northern segment (33-41°S) the volcanoes are co-located with the main orogenic water divide, whereas in the southern segment (41-46°S) the water divide is shifted eastward and the volcanic arc is shifted westward. The eastward water divide migration in the southern segment is explained by an orographic effect due to the westerlies winds, which causes high precipitation (>2 m/yr) and erosion rates (>1.5 mm/yr) on the upwind side of the orogen. Thermomechanical visco-elasto-plastic numerical models exploring the effects of the topographic shift on the magma upwelling path explain the westward migration of the volcanic arc. Results show that when the topographic barrier is shifted to the east with respect to a central magmatic source, asymmetric strain due to the magma emplacement into the crust drives preferential westward magma upwelling. The southern segment of the SVZ is proximal to an important strike slip fault system, the Liquiñe-Ofqui fault zone. We propose that the (re-)activation of these fracture zone on the western side of the Southern Andes is related to the orographic migration of the water divide during magma upwelling. This conclusion is further supported by the lack of structures accommodating magma emplacement/eruption and volcanoes east of the water divide. If correct, this is the first-recognized example of a climatic control on the location of a volcanic arc in convergent settings.
How to cite: Paiva Muller, V. A., Sternai, P., and Sue, C.: Climatic control on the Southern Andean volcanic arc location, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-591, https://doi.org/10.5194/egusphere-egu21-591, 2021.
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The Southern Andes Volcanic zone (SVZ) is located between latitudes 33-46°S in the western margin of the South American continental plate, above the subducting Nazca oceanic plate. Although the slab dip angle is constant (~25°) along strike, the distance between the volcanic arc and the subduction trench decreases southward. In the northern segment (33-41°S) the volcanoes are co-located with the main orogenic water divide, whereas in the southern segment (41-46°S) the water divide is shifted eastward and the volcanic arc is shifted westward. The eastward water divide migration in the southern segment is explained by an orographic effect due to the westerlies winds, which causes high precipitation (>2 m/yr) and erosion rates (>1.5 mm/yr) on the upwind side of the orogen. Thermomechanical visco-elasto-plastic numerical models exploring the effects of the topographic shift on the magma upwelling path explain the westward migration of the volcanic arc. Results show that when the topographic barrier is shifted to the east with respect to a central magmatic source, asymmetric strain due to the magma emplacement into the crust drives preferential westward magma upwelling. The southern segment of the SVZ is proximal to an important strike slip fault system, the Liquiñe-Ofqui fault zone. We propose that the (re-)activation of these fracture zone on the western side of the Southern Andes is related to the orographic migration of the water divide during magma upwelling. This conclusion is further supported by the lack of structures accommodating magma emplacement/eruption and volcanoes east of the water divide. If correct, this is the first-recognized example of a climatic control on the location of a volcanic arc in convergent settings.
How to cite: Paiva Muller, V. A., Sternai, P., and Sue, C.: Climatic control on the Southern Andean volcanic arc location, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-591, https://doi.org/10.5194/egusphere-egu21-591, 2021.
EGU21-6130 | vPICO presentations | GM9.14
Onset of Carnegie Ridge subduction from low-temperature thermochronologyAudrey Margirier, Manfred Strecker, Peter Reiners, Ismael Casado, Stuart Thomson, Sarah George, and Alexandra Alvarado
Cenozoic growth of the Andes has been strongly influenced by subduction dynamics, inherited crustal heterogeneities, and the superposed effects of climate. Subduction of the Carnegie Ridge in Ecuador has impacted late Cenozoic magmatism and tectonic activity, including the formation of a crustal sliver escaping northward. However, the relationship between ridge subduction and topographic growth has remained unclear. We present new thermochronological data from the Western Cordillera of Ecuador to (1) pinpoint the timing of ridge subduction, and (2) evaluate the role of ridge subduction in prompting growth of the Ecuadorian Andes. Time-temperature inverse modeling of our results shows two phases of cooling separated by tectonic quiescence. The first cooling phase immediately post-dates magmatism in the Western Cordillera, and hence we attribute it to magmatic cooling. The second cooling phase starts at ~6-5 Ma. This we associate with onset of enhanced exhumation at this time in the Western Cordillera, synchronous with the last cooling phase in the Eastern Cordillera. Based on our thermal modeling and thermochronological age patterns along geological cross-sections we propose that recent crustal shortening and rock uplift triggered exhumation of Western Ecuadorian Andes starting at ~6-5 Ma. We suggest that the onset of Carnegie Ridge subduction in the latest Miocene increased the coupling at the subduction interface and promoted shortening and regional rock uplift in the northern Andes. Overall, our new thermochronological results highlight the pivotal role of bathymetric anomalies in distinct upper-plate deformation processes at non-collisional convergent plate margins.
How to cite: Margirier, A., Strecker, M., Reiners, P., Casado, I., Thomson, S., George, S., and Alvarado, A.: Onset of Carnegie Ridge subduction from low-temperature thermochronology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6130, https://doi.org/10.5194/egusphere-egu21-6130, 2021.
Cenozoic growth of the Andes has been strongly influenced by subduction dynamics, inherited crustal heterogeneities, and the superposed effects of climate. Subduction of the Carnegie Ridge in Ecuador has impacted late Cenozoic magmatism and tectonic activity, including the formation of a crustal sliver escaping northward. However, the relationship between ridge subduction and topographic growth has remained unclear. We present new thermochronological data from the Western Cordillera of Ecuador to (1) pinpoint the timing of ridge subduction, and (2) evaluate the role of ridge subduction in prompting growth of the Ecuadorian Andes. Time-temperature inverse modeling of our results shows two phases of cooling separated by tectonic quiescence. The first cooling phase immediately post-dates magmatism in the Western Cordillera, and hence we attribute it to magmatic cooling. The second cooling phase starts at ~6-5 Ma. This we associate with onset of enhanced exhumation at this time in the Western Cordillera, synchronous with the last cooling phase in the Eastern Cordillera. Based on our thermal modeling and thermochronological age patterns along geological cross-sections we propose that recent crustal shortening and rock uplift triggered exhumation of Western Ecuadorian Andes starting at ~6-5 Ma. We suggest that the onset of Carnegie Ridge subduction in the latest Miocene increased the coupling at the subduction interface and promoted shortening and regional rock uplift in the northern Andes. Overall, our new thermochronological results highlight the pivotal role of bathymetric anomalies in distinct upper-plate deformation processes at non-collisional convergent plate margins.
How to cite: Margirier, A., Strecker, M., Reiners, P., Casado, I., Thomson, S., George, S., and Alvarado, A.: Onset of Carnegie Ridge subduction from low-temperature thermochronology, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6130, https://doi.org/10.5194/egusphere-egu21-6130, 2021.
EGU21-7172 | vPICO presentations | GM9.14
4 Ma-long uplift cycles of the southern Peru forearc since Late MioceneVincent Regard, Joseph Martinod, Marianne Saillard, Sébastien Carretier, Laetitia Leanni, Gérard Hérail, Laurence Audin, and Kevin Pedoja
We explore the coastal morphology along an uplifting 500 km-long coastal segment of the Central Andes, between the cities of Chala (Peru) and Arica (Chile). We use accurate DEM and field surveys to extract sequences of uplifted shorelines along the study area. In addition, we consider continental pediment surfaces that limit both the geographical and vertical extent of the marine landforms. We establish a chronology based on published dates for marine landforms and pediment surfaces. We expand this corpus with new 10Be data on uplifted shore platforms. The last 12 Ma are marked by three periods of coastal stability or subsidence dated ~12-11 Ma, ~8-7 Ma and ~5-2.5 Ma ago. The uplift that accumulated between these stability periods has been ~1000 m since 11 Ma; its rate can reach 0.25 mm/a (m/ka). For the last period of uplift only, during the last 800 ka, the forearc uplift has been accurately recorded by the carving of numerous coastal sequences. Within these sequences, we correlated the marine terraces with the sea level highstands (interglacial stages and sub-stages) up to MIS 19 (790 ka), i.e., with a resolution of ~100 ka. The uplift rate for this last period of uplift increases westward from 0.18 mm/a at the Peru-Chile border to ~0.25 mm/a in the center of the study area. It further increases northwestward, up to 0.45 mm/a, due to the influence of the Nazca Ridge. In this study, we document an unusual forearc cyclic uplift with ~4 Ma-long cycles. This periodicity corresponds to the predictions made by Menant et al. (2020) based on numerical models, and could be related to episodic tectonic underplating (subducting slab stripping) beneath the coastal forearc area.
How to cite: Regard, V., Martinod, J., Saillard, M., Carretier, S., Leanni, L., Hérail, G., Audin, L., and Pedoja, K.: 4 Ma-long uplift cycles of the southern Peru forearc since Late Miocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7172, https://doi.org/10.5194/egusphere-egu21-7172, 2021.
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We explore the coastal morphology along an uplifting 500 km-long coastal segment of the Central Andes, between the cities of Chala (Peru) and Arica (Chile). We use accurate DEM and field surveys to extract sequences of uplifted shorelines along the study area. In addition, we consider continental pediment surfaces that limit both the geographical and vertical extent of the marine landforms. We establish a chronology based on published dates for marine landforms and pediment surfaces. We expand this corpus with new 10Be data on uplifted shore platforms. The last 12 Ma are marked by three periods of coastal stability or subsidence dated ~12-11 Ma, ~8-7 Ma and ~5-2.5 Ma ago. The uplift that accumulated between these stability periods has been ~1000 m since 11 Ma; its rate can reach 0.25 mm/a (m/ka). For the last period of uplift only, during the last 800 ka, the forearc uplift has been accurately recorded by the carving of numerous coastal sequences. Within these sequences, we correlated the marine terraces with the sea level highstands (interglacial stages and sub-stages) up to MIS 19 (790 ka), i.e., with a resolution of ~100 ka. The uplift rate for this last period of uplift increases westward from 0.18 mm/a at the Peru-Chile border to ~0.25 mm/a in the center of the study area. It further increases northwestward, up to 0.45 mm/a, due to the influence of the Nazca Ridge. In this study, we document an unusual forearc cyclic uplift with ~4 Ma-long cycles. This periodicity corresponds to the predictions made by Menant et al. (2020) based on numerical models, and could be related to episodic tectonic underplating (subducting slab stripping) beneath the coastal forearc area.
How to cite: Regard, V., Martinod, J., Saillard, M., Carretier, S., Leanni, L., Hérail, G., Audin, L., and Pedoja, K.: 4 Ma-long uplift cycles of the southern Peru forearc since Late Miocene, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7172, https://doi.org/10.5194/egusphere-egu21-7172, 2021.
EGU21-13740 | vPICO presentations | GM9.14 | Highlight
Differential uplift of three Pliocene sea level indicator sites in southern Argentina driven by upwelling asthenosphere through the Patagonian slab windowAndrew Hollyday, Jacqueline Austermann, Andrew Lloyd, Mark Hoggard, Fred Richards, and Alessio Rovere
Bivalve and gastropod shell beds deposited during the Early Pliocene (4.69-5.23 Ma) occur in uplifted outcrops (36 – 180 m above sea level) along the east coast of Patagonian Argentina. These rock units provide a record of sea level during a geologic period when atmospheric CO2 and temperatures were higher than today. As such, reconstructing the elevation of global mean sea level (GMSL) during this time allows us to better understand how sensitive ice sheets are to increased past and future warming. However, reconstructing GMSL from local sea level indicators is hindered by effects such as mantle dynamic topography and glacial isostatic adjustment (GIA) that cause local sea level to deviate from the global mean. Here we use geodynamic modeling to better understand this complex dynamic setting and quantify the amount of uplift along this coastline.
Despite being located on a relatively stable passive margin, significant variations in the elevation of the paleo shoreline indicators imply that the underlying convecting mantle is deforming the coastline. In particular, the subduction of the Chile Rise beginning ~18 Ma beneath Patagonia has generated a slab window underneath this region through which hot asthenosphere ascends. However, the former slab is still present deeper in the mantle, which causes a complex interplay between the downwelling slab and the upwelling asthenosphere. To quantify the effects of dynamic topography change since the Pliocene, we run 3D mantle convection simulations using the code ASPECT. We initialize our global model with a composite temperature structure derived from recent tomographic studies and a calibrated parameterization of upper mantle anelasticity. Independent estimates of pressure and temperature from thermobarometric calculations of proximal Pali-Aike xenoliths agree with the thermal structure of the tomography-based Earth model. We back-advect temperature perturbations and extract the resulting change in dynamic topography. Pairing GIA models and a suite of convection simulations in which we vary the viscosity and buoyancy structure with the observed differential paleo shoreline elevations allows us to forward model the most likely scenario for uplift along this coast.
How to cite: Hollyday, A., Austermann, J., Lloyd, A., Hoggard, M., Richards, F., and Rovere, A.: Differential uplift of three Pliocene sea level indicator sites in southern Argentina driven by upwelling asthenosphere through the Patagonian slab window , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13740, https://doi.org/10.5194/egusphere-egu21-13740, 2021.
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Bivalve and gastropod shell beds deposited during the Early Pliocene (4.69-5.23 Ma) occur in uplifted outcrops (36 – 180 m above sea level) along the east coast of Patagonian Argentina. These rock units provide a record of sea level during a geologic period when atmospheric CO2 and temperatures were higher than today. As such, reconstructing the elevation of global mean sea level (GMSL) during this time allows us to better understand how sensitive ice sheets are to increased past and future warming. However, reconstructing GMSL from local sea level indicators is hindered by effects such as mantle dynamic topography and glacial isostatic adjustment (GIA) that cause local sea level to deviate from the global mean. Here we use geodynamic modeling to better understand this complex dynamic setting and quantify the amount of uplift along this coastline.
Despite being located on a relatively stable passive margin, significant variations in the elevation of the paleo shoreline indicators imply that the underlying convecting mantle is deforming the coastline. In particular, the subduction of the Chile Rise beginning ~18 Ma beneath Patagonia has generated a slab window underneath this region through which hot asthenosphere ascends. However, the former slab is still present deeper in the mantle, which causes a complex interplay between the downwelling slab and the upwelling asthenosphere. To quantify the effects of dynamic topography change since the Pliocene, we run 3D mantle convection simulations using the code ASPECT. We initialize our global model with a composite temperature structure derived from recent tomographic studies and a calibrated parameterization of upper mantle anelasticity. Independent estimates of pressure and temperature from thermobarometric calculations of proximal Pali-Aike xenoliths agree with the thermal structure of the tomography-based Earth model. We back-advect temperature perturbations and extract the resulting change in dynamic topography. Pairing GIA models and a suite of convection simulations in which we vary the viscosity and buoyancy structure with the observed differential paleo shoreline elevations allows us to forward model the most likely scenario for uplift along this coast.
How to cite: Hollyday, A., Austermann, J., Lloyd, A., Hoggard, M., Richards, F., and Rovere, A.: Differential uplift of three Pliocene sea level indicator sites in southern Argentina driven by upwelling asthenosphere through the Patagonian slab window , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13740, https://doi.org/10.5194/egusphere-egu21-13740, 2021.
EGU21-15505 | vPICO presentations | GM9.14 | Highlight
Global Continental Residual TopographySimon Stephenson, Mark Hoggard, and Nicky White
Convective circulation in the mantle supports some fraction of Earth’s topography. It is challenging to observe this topographic expression of mantle convection because it is contaminated by crustal and lithospheric isostatic processes. In the oceanic realm, residual bathymetry has been calculated by removing the effects of sedimentary and crustal thickness variations and comparing to the well-known plate cooling trend, revealing sub-plate topographic support that is up to 1–2 km in amplitude and varies on wavelengths of ~1000 km. On the continents, crustal thickness and density variations support a much larger fraction of topography. Similarly, the density and thickness of the lithospheric mantle do not follow a simple predictive relationship. It is therefore significantly more challenging to calculate the component of sub-plate topographic support in the continental realm. Here, we assemble a database of > 20,000 continental crustal thickness estimates from published active and passive source seismic experiments with a goal of exploring the topographic expression of crustal, lithospheric, and sub-plate mantle structure. A subset of these studies provides constraints on crustal seismic velocity structure which can be used to estimate local density structure of the continental crust. We exploit a database of laboratory-determined density and velocity measurements of crustal rocks to develop a velocity to density conversion scheme. We use these constraints on crustal structure to remove the effects of crustal thickness and density variations and calculate an estimate of residual topography that arises from mantle processes. We compare these values of residual topography to an independent, tomographically derived map of lithospheric thickness. We find that residual topography is negatively correlated with lithospheric mantle thickness, which is expected and consistent with oceanic lithospheric observations. Next, we exploit a pressure and temperature-dependent density parametrisation to calculate and remove the expected topographic contribution of the lithospheric mantle. This approach demonstrates that up to 3 km of residual topography is positively correlated with lithospheric thickness even after removing the effects of cooling and thickening of the plate, indicating that compositional factors may lead to decreasing density with increasing lithospheric thickness. This relationship is in broad agreement with constraints on lithospheric mantle composition from xenoliths. Our analysis demonstrates the importance of accounting for lithospheric structure in the continental realm in constraining the sub-plate, dynamic contribution to Earth’s topography. An important corollary is that changes to the density and thickness of lithospheric mantle drive rapid vertical motions of the Earth’s surface which are increasingly recognised as causes of regional epeirogenic uplift.
How to cite: Stephenson, S., Hoggard, M., and White, N.: Global Continental Residual Topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15505, https://doi.org/10.5194/egusphere-egu21-15505, 2021.
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Convective circulation in the mantle supports some fraction of Earth’s topography. It is challenging to observe this topographic expression of mantle convection because it is contaminated by crustal and lithospheric isostatic processes. In the oceanic realm, residual bathymetry has been calculated by removing the effects of sedimentary and crustal thickness variations and comparing to the well-known plate cooling trend, revealing sub-plate topographic support that is up to 1–2 km in amplitude and varies on wavelengths of ~1000 km. On the continents, crustal thickness and density variations support a much larger fraction of topography. Similarly, the density and thickness of the lithospheric mantle do not follow a simple predictive relationship. It is therefore significantly more challenging to calculate the component of sub-plate topographic support in the continental realm. Here, we assemble a database of > 20,000 continental crustal thickness estimates from published active and passive source seismic experiments with a goal of exploring the topographic expression of crustal, lithospheric, and sub-plate mantle structure. A subset of these studies provides constraints on crustal seismic velocity structure which can be used to estimate local density structure of the continental crust. We exploit a database of laboratory-determined density and velocity measurements of crustal rocks to develop a velocity to density conversion scheme. We use these constraints on crustal structure to remove the effects of crustal thickness and density variations and calculate an estimate of residual topography that arises from mantle processes. We compare these values of residual topography to an independent, tomographically derived map of lithospheric thickness. We find that residual topography is negatively correlated with lithospheric mantle thickness, which is expected and consistent with oceanic lithospheric observations. Next, we exploit a pressure and temperature-dependent density parametrisation to calculate and remove the expected topographic contribution of the lithospheric mantle. This approach demonstrates that up to 3 km of residual topography is positively correlated with lithospheric thickness even after removing the effects of cooling and thickening of the plate, indicating that compositional factors may lead to decreasing density with increasing lithospheric thickness. This relationship is in broad agreement with constraints on lithospheric mantle composition from xenoliths. Our analysis demonstrates the importance of accounting for lithospheric structure in the continental realm in constraining the sub-plate, dynamic contribution to Earth’s topography. An important corollary is that changes to the density and thickness of lithospheric mantle drive rapid vertical motions of the Earth’s surface which are increasingly recognised as causes of regional epeirogenic uplift.
How to cite: Stephenson, S., Hoggard, M., and White, N.: Global Continental Residual Topography, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15505, https://doi.org/10.5194/egusphere-egu21-15505, 2021.
EGU21-8822 | vPICO presentations | GM9.14
Exploiting a paleobiological database to constrain sub-plate support: Examples from western North America, northeast Brazil and northern AfricaVictoria Milanez Fernandes and Gareth Roberts
The shape of the Earth's surface is the result of complex interactions between deep and surface processes operating on a range of spatial and temporal scales. However, generating sufficient geological observations at the spatial and temporal scales relevant to investigating deep-Earth processes (~100–1000 km, ~1–100 Ma) remains a challenge. To address this challenge, I exploit a paleobiological database to generate a new compilation of >24,000 spot measurements of net surface uplift across all continents. The present-day elevation of marine fossil assemblages that crop out at the Earth’s surface provides a direct constraint on the timing and amplitude of net surface uplift on geological timescales. I explore how these surface observations can be used to explore the evolution of sub-plate processes in three key regions: Western North America, Borborema Province in northeast Brazil, and Northern Africa. This new data compilation provides self-consistent, and in places high resolution measurements for Cretaceous to Recent net uplift. Geophysical observations (e.g., free-air gravity, shear-wave topography) and isostatic calculations are combined with net uplift measurements from these regions to explore how mantle thermal anomalies and lithospheric thinning might generate the observed uplift patterns. Uncertainties associated with paleo-bathymetry, post-deposition compaction and glacio-eustasy are assessed. The results emphasise the importance of large inventories of paleobiological data for understanding the history of tectonic and mantle convective processes as expressed at the Earth's surface.
How to cite: Milanez Fernandes, V. and Roberts, G.: Exploiting a paleobiological database to constrain sub-plate support: Examples from western North America, northeast Brazil and northern Africa, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8822, https://doi.org/10.5194/egusphere-egu21-8822, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The shape of the Earth's surface is the result of complex interactions between deep and surface processes operating on a range of spatial and temporal scales. However, generating sufficient geological observations at the spatial and temporal scales relevant to investigating deep-Earth processes (~100–1000 km, ~1–100 Ma) remains a challenge. To address this challenge, I exploit a paleobiological database to generate a new compilation of >24,000 spot measurements of net surface uplift across all continents. The present-day elevation of marine fossil assemblages that crop out at the Earth’s surface provides a direct constraint on the timing and amplitude of net surface uplift on geological timescales. I explore how these surface observations can be used to explore the evolution of sub-plate processes in three key regions: Western North America, Borborema Province in northeast Brazil, and Northern Africa. This new data compilation provides self-consistent, and in places high resolution measurements for Cretaceous to Recent net uplift. Geophysical observations (e.g., free-air gravity, shear-wave topography) and isostatic calculations are combined with net uplift measurements from these regions to explore how mantle thermal anomalies and lithospheric thinning might generate the observed uplift patterns. Uncertainties associated with paleo-bathymetry, post-deposition compaction and glacio-eustasy are assessed. The results emphasise the importance of large inventories of paleobiological data for understanding the history of tectonic and mantle convective processes as expressed at the Earth's surface.
How to cite: Milanez Fernandes, V. and Roberts, G.: Exploiting a paleobiological database to constrain sub-plate support: Examples from western North America, northeast Brazil and northern Africa, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8822, https://doi.org/10.5194/egusphere-egu21-8822, 2021.
EGU21-9165 | vPICO presentations | GM9.14
Geomorphic imprints of dynamic topography and intraplate tectonism in central AustraliaJohn Jansen, Mike Sandiford, Toshiyuki Fujioka, Timothy Cohen, Martin Struck, Suzanne Anderson, Robert Anderson, and David Egholm
The Finke River in central Australia is counted among the world’s oldest drainage systems, raising the prospect that it holds a geomorphic record relevant to testing ideas about the role of sub-lithospheric mantle flow in shaping the Australian landscape. The Finke’s upper reaches preserve an enigmatic set of intertwined active and relict gorges that suggest a complex history of incision, aggradation and re-incision. We measured cosmogenic 10Be and 26Al in fluvial gravels stored in the gorges, and we applied a Markov chain Monte Carlo-based inversion model to test two limiting-case hypotheses about the timing of the gravel deposition and exhumation. Our results suggest that the nuclide memory contained within the gravels was essentially erased during protracted sediment storage. Previous studies attribute landscape evolution to the intensified post-Miocene aridity in tune with the perception that central Australia experienced limited deformation during the Cenozoic. However, the close correlation between drainage network patterns and the gravity field leads us to propose, instead, that incision/aggradation phases in the upper Finke are driven by a flexural response (at ~102 km length scales) to extreme uncompensated loads embedded in the crust. Further, we suggest that dynamic mantle processes have deformed the central Australian topography over longer (~103 km) wavelengths via the in-situ stress field, with horizontal stress variations of order 1–10 MPa. Acting together, these crustal and sub-lithospheric structures have imposed to-and-fro tilting on the Finke, triggering the phases of incision/aggradation on a million-year timescale that created the unusual intertwined bedrock gorges. The amplitude of topographic responses in the upper Finke to inferred variations in end-loading on the plate helps resolve an ongoing debate about the effective elastic thickness of the central Australian lithosphere to no more than 35 km.
How to cite: Jansen, J., Sandiford, M., Fujioka, T., Cohen, T., Struck, M., Anderson, S., Anderson, R., and Egholm, D.: Geomorphic imprints of dynamic topography and intraplate tectonism in central Australia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9165, https://doi.org/10.5194/egusphere-egu21-9165, 2021.
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The Finke River in central Australia is counted among the world’s oldest drainage systems, raising the prospect that it holds a geomorphic record relevant to testing ideas about the role of sub-lithospheric mantle flow in shaping the Australian landscape. The Finke’s upper reaches preserve an enigmatic set of intertwined active and relict gorges that suggest a complex history of incision, aggradation and re-incision. We measured cosmogenic 10Be and 26Al in fluvial gravels stored in the gorges, and we applied a Markov chain Monte Carlo-based inversion model to test two limiting-case hypotheses about the timing of the gravel deposition and exhumation. Our results suggest that the nuclide memory contained within the gravels was essentially erased during protracted sediment storage. Previous studies attribute landscape evolution to the intensified post-Miocene aridity in tune with the perception that central Australia experienced limited deformation during the Cenozoic. However, the close correlation between drainage network patterns and the gravity field leads us to propose, instead, that incision/aggradation phases in the upper Finke are driven by a flexural response (at ~102 km length scales) to extreme uncompensated loads embedded in the crust. Further, we suggest that dynamic mantle processes have deformed the central Australian topography over longer (~103 km) wavelengths via the in-situ stress field, with horizontal stress variations of order 1–10 MPa. Acting together, these crustal and sub-lithospheric structures have imposed to-and-fro tilting on the Finke, triggering the phases of incision/aggradation on a million-year timescale that created the unusual intertwined bedrock gorges. The amplitude of topographic responses in the upper Finke to inferred variations in end-loading on the plate helps resolve an ongoing debate about the effective elastic thickness of the central Australian lithosphere to no more than 35 km.
How to cite: Jansen, J., Sandiford, M., Fujioka, T., Cohen, T., Struck, M., Anderson, S., Anderson, R., and Egholm, D.: Geomorphic imprints of dynamic topography and intraplate tectonism in central Australia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9165, https://doi.org/10.5194/egusphere-egu21-9165, 2021.
EGU21-16512 | vPICO presentations | GM9.14
African Epeirogeny in the Geomorphic RecordConor O'Malley, Nicky White, Gareth Roberts, and Simon Stephenson
A range of geological evidence documents the growth of African topography as a result of sub-plate support throughout Cenozoic times. Recent studies used inverse modeling of drainage networks governed by the linear stream power law to quantify the spatio-temporal history of uplift and erosion across the continent. Here, we test predictions of this uplift rate history by applying it as tectonic forcing to naturalistic landscape evolution simulations. These simulations parameterise dynamic drainage reorganisation, track sedimentary flux, and permit variable erodibility, none of which are feasible in inverse models. Modelled topography, river profiles, drainage planforms and sedimentary flux patterns broadly match observations. We test the sensitivity of forward model prediction to variations in erodilibity by employing spatio-temporally variable precipitation rate. Forward model predictions are relatively robust to even large excursions, suggesting landscapes contain internal feedbacks which modulate these effects and permit close recovery of the geomorphic record of uplift. Wavelet power spectral analysis reveals observed African river profiles are self-similar at wavelengths >~ 100 km, meaning longest-wavelength features have the highest amplitudes. At shorter wavelengths, spectral slopes increase, implying sharper features are generated only at wavelengths <~ 100km. Synthetic fluvial profiles recovered from simple landscape evolution models driven by uplift forcing obtained from inverse modeling of observed river profiles are self-similar across all wavelengths. This self-similarity solely reflects the tectonic forcing applied. When noise in erodibility or uplift rate forcing is added to forward simulations, power spectra of resulting fluvial profiles more closely approximate spectra of observed profiles. Thus sharp signals in observed river profiles arise from factors which do not correlate between neighbouring tributaries, e.g. lithological constrasts, self-forming hydraulic shocks, or human alteration. The recoverability of regional uplift from observed fluvial profiles is made possible by the fact that most topographic power is generated by regional uplift and resides at long-wavelengths.
How to cite: O'Malley, C., White, N., Roberts, G., and Stephenson, S.: African Epeirogeny in the Geomorphic Record, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16512, https://doi.org/10.5194/egusphere-egu21-16512, 2021.
A range of geological evidence documents the growth of African topography as a result of sub-plate support throughout Cenozoic times. Recent studies used inverse modeling of drainage networks governed by the linear stream power law to quantify the spatio-temporal history of uplift and erosion across the continent. Here, we test predictions of this uplift rate history by applying it as tectonic forcing to naturalistic landscape evolution simulations. These simulations parameterise dynamic drainage reorganisation, track sedimentary flux, and permit variable erodibility, none of which are feasible in inverse models. Modelled topography, river profiles, drainage planforms and sedimentary flux patterns broadly match observations. We test the sensitivity of forward model prediction to variations in erodilibity by employing spatio-temporally variable precipitation rate. Forward model predictions are relatively robust to even large excursions, suggesting landscapes contain internal feedbacks which modulate these effects and permit close recovery of the geomorphic record of uplift. Wavelet power spectral analysis reveals observed African river profiles are self-similar at wavelengths >~ 100 km, meaning longest-wavelength features have the highest amplitudes. At shorter wavelengths, spectral slopes increase, implying sharper features are generated only at wavelengths <~ 100km. Synthetic fluvial profiles recovered from simple landscape evolution models driven by uplift forcing obtained from inverse modeling of observed river profiles are self-similar across all wavelengths. This self-similarity solely reflects the tectonic forcing applied. When noise in erodibility or uplift rate forcing is added to forward simulations, power spectra of resulting fluvial profiles more closely approximate spectra of observed profiles. Thus sharp signals in observed river profiles arise from factors which do not correlate between neighbouring tributaries, e.g. lithological constrasts, self-forming hydraulic shocks, or human alteration. The recoverability of regional uplift from observed fluvial profiles is made possible by the fact that most topographic power is generated by regional uplift and resides at long-wavelengths.
How to cite: O'Malley, C., White, N., Roberts, G., and Stephenson, S.: African Epeirogeny in the Geomorphic Record, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16512, https://doi.org/10.5194/egusphere-egu21-16512, 2021.
EGU21-12331 | vPICO presentations | GM9.14
Escarpment retreat on a viscoelastic lithosphereGregory Ruetenik and Robert Moucha
Rift escarpments have long been the subject of coupled geodynamic/landscape evolution studies. Many of these studies have shown that the flexural unloading response of the lithosphere plays a significant role in the rate of divide migration and the longevity of the escarpment topography, with lower elastic thickness values allowing for more localized isostatic rebound of the lithosphere in response to erosional unloading. However, rift escarpments are thought to last hundreds of millions of years, and therefore the lithosphere may exhibit viscoelastic behavior on this timescale. Here we present a simplified model of a viscoelastic response to erosional unloading during escarpment evolution, and show that this drastically alters the behavior of the escarpment system. Specifically, the escarpment retreat rate is significantly reduced, and topography maintained, when compared to a purely flexural model. Additionally, the area in front of the retreating the scarp (i.e., seaward of the scarp) experience delayed uplift response and topographic rejuvenation many millions of years after the divide passes.
How to cite: Ruetenik, G. and Moucha, R.: Escarpment retreat on a viscoelastic lithosphere , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12331, https://doi.org/10.5194/egusphere-egu21-12331, 2021.
Rift escarpments have long been the subject of coupled geodynamic/landscape evolution studies. Many of these studies have shown that the flexural unloading response of the lithosphere plays a significant role in the rate of divide migration and the longevity of the escarpment topography, with lower elastic thickness values allowing for more localized isostatic rebound of the lithosphere in response to erosional unloading. However, rift escarpments are thought to last hundreds of millions of years, and therefore the lithosphere may exhibit viscoelastic behavior on this timescale. Here we present a simplified model of a viscoelastic response to erosional unloading during escarpment evolution, and show that this drastically alters the behavior of the escarpment system. Specifically, the escarpment retreat rate is significantly reduced, and topography maintained, when compared to a purely flexural model. Additionally, the area in front of the retreating the scarp (i.e., seaward of the scarp) experience delayed uplift response and topographic rejuvenation many millions of years after the divide passes.
How to cite: Ruetenik, G. and Moucha, R.: Escarpment retreat on a viscoelastic lithosphere , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12331, https://doi.org/10.5194/egusphere-egu21-12331, 2021.
EGU21-1562 | vPICO presentations | GM9.14
A search for constraints on lithospheric net rotation in 2D convection simulationsSuzanne Atkins and Nicolas Coltice
Net rotation is the process whereby the entire lithosphere can rotate with respect to the Earth’s mantle. The plates and continents retain their location with respect to each other, but they change their position with respect to global reference frames such as the Earth’s magnetic dipole, and structures in the Earth’s mantle such as plumes and hotspots. Constraining lithospheric net rotation is therefore one factor in building an absolute plate motion model. However, the amount of net rotation occurring at present day is poorly contained, and the drivers of net rotation are very poorly understood. Many absolute plate motion models therefore attempt to minimise net rotation, because there is no way to constrain rotation in the geological past.
In previous geodynamical studies, the presence of thick continents and large viscosity contrasts were found to be controlling factors in the development of net rotation. We investigate the effects of different convection parameters and tectonic states on the magnitude and evolution of net rotation in 2D simulations. The use of 2D simulations allows us to run enough simulations to study a wide range of model parameters. We intend to compare our 2D conclusions with 3D simulations, to investigate how much of a difference the third dimension makes.
We find that net rotation varies on much shorter timescales than any other geodynamic feature. Net rotation is not cleanly correlated with any tectonic behaviours or settings, and that the magnitude and duration is unpredictable. We do however find that the distribution of net rotation within the lifetime of a particular simulation is Gaussian, with standard deviation dependent on the viscosity structure and contrasts of the simulation, in agreement with previous studies. However, in contrast to previous studies, the presence and thickness of continents makes very little difference to the speed of lithospheric rotation, although this may be because we are working in 2D. If the 2D results are also relevant in 3D, net rotation is a continuously varying and unpredictable value, but with a predictable statistical range. This may provide a way to better constrain net rotation for plate motion models.
How to cite: Atkins, S. and Coltice, N.: A search for constraints on lithospheric net rotation in 2D convection simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1562, https://doi.org/10.5194/egusphere-egu21-1562, 2021.
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Net rotation is the process whereby the entire lithosphere can rotate with respect to the Earth’s mantle. The plates and continents retain their location with respect to each other, but they change their position with respect to global reference frames such as the Earth’s magnetic dipole, and structures in the Earth’s mantle such as plumes and hotspots. Constraining lithospheric net rotation is therefore one factor in building an absolute plate motion model. However, the amount of net rotation occurring at present day is poorly contained, and the drivers of net rotation are very poorly understood. Many absolute plate motion models therefore attempt to minimise net rotation, because there is no way to constrain rotation in the geological past.
In previous geodynamical studies, the presence of thick continents and large viscosity contrasts were found to be controlling factors in the development of net rotation. We investigate the effects of different convection parameters and tectonic states on the magnitude and evolution of net rotation in 2D simulations. The use of 2D simulations allows us to run enough simulations to study a wide range of model parameters. We intend to compare our 2D conclusions with 3D simulations, to investigate how much of a difference the third dimension makes.
We find that net rotation varies on much shorter timescales than any other geodynamic feature. Net rotation is not cleanly correlated with any tectonic behaviours or settings, and that the magnitude and duration is unpredictable. We do however find that the distribution of net rotation within the lifetime of a particular simulation is Gaussian, with standard deviation dependent on the viscosity structure and contrasts of the simulation, in agreement with previous studies. However, in contrast to previous studies, the presence and thickness of continents makes very little difference to the speed of lithospheric rotation, although this may be because we are working in 2D. If the 2D results are also relevant in 3D, net rotation is a continuously varying and unpredictable value, but with a predictable statistical range. This may provide a way to better constrain net rotation for plate motion models.
How to cite: Atkins, S. and Coltice, N.: A search for constraints on lithospheric net rotation in 2D convection simulations, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1562, https://doi.org/10.5194/egusphere-egu21-1562, 2021.
EGU21-13574 | vPICO presentations | GM9.14
Relative Timing of the Eocene Global Reorganization of Plate Motions: New Results for Pacific Plate Hotspot TracksKevin Gaastra and Richard Gordon
To improve modeling of deep-earth dynamics it is important to understand changes in the arrangements of plate boundaries, especially trenches accommodating subduction, and major changes in tectonic plate motion. Here we focus on the sequence of key surface events in Eocene time that likely coincide with changes in deep-earth dynamics. In particular, we develop methods of analysis of seamount locations and age dates using a small number of adjustable parameters (10 per chain) on the Pacific plate with a focus on the timing of the Hawaiian-Emperor bend relative to the timing of other major Eocene tectonic changes.
We find that motion between hotspots differs insignificantly from zero with rates of 2±4 mm/a (±2σ) for 0-48 Ma and 26±34 mm/a (±2σ) for 48-80 Ma. Relative to a mean Pacific hotspot reference frame, nominal rates of motion of the Hawaii, Louisville, and Rurutu hotspots are ~5 mm/a and differ insignificantly from zero. We conclude that plumes underlying these Pacific hotspots are more stable in a convecting mantle than previously inferred.
We estimate the locations and ages (with uncertainties) of bends in Pacific hotspot chains using a novel inversion method. The location of the ~60° change in trend at the Hawaiian-Emperor bend is well constrained within ~50-80 km (=2σ), but the location of the bends in the Louisville and Rurutu hotspots are more uncertain. If the uncertainty in the location of the bend in the Louisville chain is included, we find no significant difference in age between the bends of different Pacific hotspot chains. The best-fitting assumed-coeval age for the bends is 47.4±1.0 Ma (±2σ), which is indistinguishable from the age of the C21o geomagnetic reversal. The age of the bend is younger than the initiation of subduction in the Western Pacific, but approximately coeval with changes in Pacific and circum-Pacific relative plate motion. Changes to the tectonic system near the age of the bend are not limited to the Pacific basin. The smooth-rough transition flanking the Carlsberg Ridge records a threshold in the decreasing spreading rate between India and Africa, thought to record the onset of the collision of India with Eurasia, and is constrained to be between C21y and C20o (46 Ma and 43 Ma) in age. Nearly simultaneously, South America and Australia began to diverge more rapidly from Antarctica. The Eocene bend in Pacific hotspot chains may be the most evident feature recording a global re-organization of plate motions and mantle circulation possibly caused by the earlier collision of India and Eurasia or initiation of western Pacific subduction.
How to cite: Gaastra, K. and Gordon, R.: Relative Timing of the Eocene Global Reorganization of Plate Motions: New Results for Pacific Plate Hotspot Tracks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13574, https://doi.org/10.5194/egusphere-egu21-13574, 2021.
To improve modeling of deep-earth dynamics it is important to understand changes in the arrangements of plate boundaries, especially trenches accommodating subduction, and major changes in tectonic plate motion. Here we focus on the sequence of key surface events in Eocene time that likely coincide with changes in deep-earth dynamics. In particular, we develop methods of analysis of seamount locations and age dates using a small number of adjustable parameters (10 per chain) on the Pacific plate with a focus on the timing of the Hawaiian-Emperor bend relative to the timing of other major Eocene tectonic changes.
We find that motion between hotspots differs insignificantly from zero with rates of 2±4 mm/a (±2σ) for 0-48 Ma and 26±34 mm/a (±2σ) for 48-80 Ma. Relative to a mean Pacific hotspot reference frame, nominal rates of motion of the Hawaii, Louisville, and Rurutu hotspots are ~5 mm/a and differ insignificantly from zero. We conclude that plumes underlying these Pacific hotspots are more stable in a convecting mantle than previously inferred.
We estimate the locations and ages (with uncertainties) of bends in Pacific hotspot chains using a novel inversion method. The location of the ~60° change in trend at the Hawaiian-Emperor bend is well constrained within ~50-80 km (=2σ), but the location of the bends in the Louisville and Rurutu hotspots are more uncertain. If the uncertainty in the location of the bend in the Louisville chain is included, we find no significant difference in age between the bends of different Pacific hotspot chains. The best-fitting assumed-coeval age for the bends is 47.4±1.0 Ma (±2σ), which is indistinguishable from the age of the C21o geomagnetic reversal. The age of the bend is younger than the initiation of subduction in the Western Pacific, but approximately coeval with changes in Pacific and circum-Pacific relative plate motion. Changes to the tectonic system near the age of the bend are not limited to the Pacific basin. The smooth-rough transition flanking the Carlsberg Ridge records a threshold in the decreasing spreading rate between India and Africa, thought to record the onset of the collision of India with Eurasia, and is constrained to be between C21y and C20o (46 Ma and 43 Ma) in age. Nearly simultaneously, South America and Australia began to diverge more rapidly from Antarctica. The Eocene bend in Pacific hotspot chains may be the most evident feature recording a global re-organization of plate motions and mantle circulation possibly caused by the earlier collision of India and Eurasia or initiation of western Pacific subduction.
How to cite: Gaastra, K. and Gordon, R.: Relative Timing of the Eocene Global Reorganization of Plate Motions: New Results for Pacific Plate Hotspot Tracks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13574, https://doi.org/10.5194/egusphere-egu21-13574, 2021.
EGU21-13842 | vPICO presentations | GM9.14
Dynamics of arc-continent collision: the role of crustal-mantle dynamics on controlling the spatio-temporal evolution of stressAndres Felipe Rodriguez Corcho, Sara Morón, Rebecca Farrington, Romain Beucher, Louis Moresi, and Camilo Montes
Arc-continent collision is the process by which intra-oceanic arc crust is accreted to continental margins and the most important mechanism that enables the growth of the continental crust since Phanerozoic times. We use numerical visco-plastic mechanical models to explore: (i) the role of lithospheric-mantle dynamics in controlling the spatio-temporal evolution of stress in arc-continent collision settings, and (ii) the role of density contrasts in the evolution of the stress regime. We performed a series of simulations only varying the thickness of the arc based on natural examples as the arc thickness controls the buoyancy of intra-oceanic arcs. Therefore, we investigated a range of density contrasts between the arc and the continental plate. Modelling results show that arc-continent collision can evolve into two contrasting scenarios: (i) slab-anchoring and arc transference in dense arcs where the density contrast between the arc and the adjacent continental lithosphere is above -3% (15-31 km in thickness); and (ii) slab break-off in buoyant arcs where the density contrast between the arc and the adjacent continental lithosphere is below -3% (32-35 km in thickness). We conclude that the large-scale mantle return flow emerged from slab-anchoring facilitates the simultaneous occurrence of compression and extension in the margin by enhancing: (i) compression and lithospheric thickening of the buoyant intra-oceanic arc crust; and (ii) the density contrast between the accreted arc and the continental margin that triggers the release of a gravitational flow. In the particular case of buoyant arcs, the compressional body force applied by the deformed arc to the subducting plate drives its passive retreat. The results of our numerical modelling highlight the importance of the role of lithospheric-mantle dynamics on controlling the spatio-temporal evolution of stress.
How to cite: Rodriguez Corcho, A. F., Morón, S., Farrington, R., Beucher, R., Moresi, L., and Montes, C.: Dynamics of arc-continent collision: the role of crustal-mantle dynamics on controlling the spatio-temporal evolution of stress , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13842, https://doi.org/10.5194/egusphere-egu21-13842, 2021.
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Arc-continent collision is the process by which intra-oceanic arc crust is accreted to continental margins and the most important mechanism that enables the growth of the continental crust since Phanerozoic times. We use numerical visco-plastic mechanical models to explore: (i) the role of lithospheric-mantle dynamics in controlling the spatio-temporal evolution of stress in arc-continent collision settings, and (ii) the role of density contrasts in the evolution of the stress regime. We performed a series of simulations only varying the thickness of the arc based on natural examples as the arc thickness controls the buoyancy of intra-oceanic arcs. Therefore, we investigated a range of density contrasts between the arc and the continental plate. Modelling results show that arc-continent collision can evolve into two contrasting scenarios: (i) slab-anchoring and arc transference in dense arcs where the density contrast between the arc and the adjacent continental lithosphere is above -3% (15-31 km in thickness); and (ii) slab break-off in buoyant arcs where the density contrast between the arc and the adjacent continental lithosphere is below -3% (32-35 km in thickness). We conclude that the large-scale mantle return flow emerged from slab-anchoring facilitates the simultaneous occurrence of compression and extension in the margin by enhancing: (i) compression and lithospheric thickening of the buoyant intra-oceanic arc crust; and (ii) the density contrast between the accreted arc and the continental margin that triggers the release of a gravitational flow. In the particular case of buoyant arcs, the compressional body force applied by the deformed arc to the subducting plate drives its passive retreat. The results of our numerical modelling highlight the importance of the role of lithospheric-mantle dynamics on controlling the spatio-temporal evolution of stress.
How to cite: Rodriguez Corcho, A. F., Morón, S., Farrington, R., Beucher, R., Moresi, L., and Montes, C.: Dynamics of arc-continent collision: the role of crustal-mantle dynamics on controlling the spatio-temporal evolution of stress , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13842, https://doi.org/10.5194/egusphere-egu21-13842, 2021.
EGU21-14684 | vPICO presentations | GM9.14
The stress field model of the South China Sea calculated by sea level data from satellitesHan Shi, Jinyao Gao, Mingju Xu, and Qingsheng Guan
The South China Sea (SCS) is situated at the junction of Eurasian, Indo-Australian, and Philippine sea plates. Its stress state provides significant information about the regional tectonic structure associated with interaction among the three plates. The stress field of the SCS is composed of horizontal and vertical stress fields. We calculate the vertically averaged deviatoric stress field using horizontal gradients of gravitational potential energy obtained by high-resolution sea-surface height data (SSH) from satellite Haiyang-2A. The vertical tectonic stress field is computed based on the Bouguer gravity anomaly derived from SSH and topographic data.
The vertically averaged deviatoric stress field is consistent with the GPS velocity field, the focal mechanism, and the mantle flow stress field of the South China Sea. Moreover, it also indicates the Red River-Ailaoshan Fault zone on the west of the SCS and the Manila subduction on the east. The vertical tectonic stress field removing the influence of sediment indicates upward stress of the lithosphere in the SCS ocean basin. The stress field model therefore provides a powerful tool for understanding regional tectonic activities around the SCS.
How to cite: Shi, H., Gao, J., Xu, M., and Guan, Q.: The stress field model of the South China Sea calculated by sea level data from satellites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14684, https://doi.org/10.5194/egusphere-egu21-14684, 2021.
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The South China Sea (SCS) is situated at the junction of Eurasian, Indo-Australian, and Philippine sea plates. Its stress state provides significant information about the regional tectonic structure associated with interaction among the three plates. The stress field of the SCS is composed of horizontal and vertical stress fields. We calculate the vertically averaged deviatoric stress field using horizontal gradients of gravitational potential energy obtained by high-resolution sea-surface height data (SSH) from satellite Haiyang-2A. The vertical tectonic stress field is computed based on the Bouguer gravity anomaly derived from SSH and topographic data.
The vertically averaged deviatoric stress field is consistent with the GPS velocity field, the focal mechanism, and the mantle flow stress field of the South China Sea. Moreover, it also indicates the Red River-Ailaoshan Fault zone on the west of the SCS and the Manila subduction on the east. The vertical tectonic stress field removing the influence of sediment indicates upward stress of the lithosphere in the SCS ocean basin. The stress field model therefore provides a powerful tool for understanding regional tectonic activities around the SCS.
How to cite: Shi, H., Gao, J., Xu, M., and Guan, Q.: The stress field model of the South China Sea calculated by sea level data from satellites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14684, https://doi.org/10.5194/egusphere-egu21-14684, 2021.
EGU21-5494 | vPICO presentations | GM9.14
The Saharides: Turkic-Type Orogeny in Afro-ArabiaA. M. Celal Şengör, Nalan Lom, Cengiz Zabcı, Gürsel Sunal, and Tayfun Öner
We describe a major new Neoproterozoic orogenic system belonging to the larger Pan-African deformational realm, the Saharides, in North Africa, by using various tools such as magnetic maps and our own remote-sensing based structural interpretation to aid us in following the orogenic trend-lines in addition to a large compilation of geochronological data. The Saharides, a Turkic-type orogenic complex similar to the Altaids of central and northwestern Asia, involved major subduction accretion complexes occupying almost the entire Arabian Shield and much of Egypt and Sudan and the small inliers of such complexes farther west to and including the Ahaggar mountains. These complexes are formed at least by half from juvenile material representing at least 5 million km2 new continental crust formed during the Neoproterozoic from about 900 to 500 Ma ago. Contrary to conventional wisdom in the areas they occupy, the Saharides involved no continental collisions until the very end of their history, but evolved by subduction and strike-slip stacking of arc material mainly by pre-collisional coast-wise transport of arc fragments shaved off the Congo/Tanzania cratonic nucleus in a manner very similar to the development of the Nipponides in east Asia, parts of the North American Cordillera and the Altaids. The entire Sahara is shown to be underlain by a double orocline much like the Hercynian double orocline in western Europe and northwestern Africa and not by an hypothetical ‘Saharan Metacraton’. The method here followed may be a fruitful procedure to untangle the structure of some of the Precambrian orogenic belts before life evolved sufficiently to make biostratigraphy feasible.
How to cite: Şengör, A. M. C., Lom, N., Zabcı, C., Sunal, G., and Öner, T.: The Saharides: Turkic-Type Orogeny in Afro-Arabia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5494, https://doi.org/10.5194/egusphere-egu21-5494, 2021.
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We describe a major new Neoproterozoic orogenic system belonging to the larger Pan-African deformational realm, the Saharides, in North Africa, by using various tools such as magnetic maps and our own remote-sensing based structural interpretation to aid us in following the orogenic trend-lines in addition to a large compilation of geochronological data. The Saharides, a Turkic-type orogenic complex similar to the Altaids of central and northwestern Asia, involved major subduction accretion complexes occupying almost the entire Arabian Shield and much of Egypt and Sudan and the small inliers of such complexes farther west to and including the Ahaggar mountains. These complexes are formed at least by half from juvenile material representing at least 5 million km2 new continental crust formed during the Neoproterozoic from about 900 to 500 Ma ago. Contrary to conventional wisdom in the areas they occupy, the Saharides involved no continental collisions until the very end of their history, but evolved by subduction and strike-slip stacking of arc material mainly by pre-collisional coast-wise transport of arc fragments shaved off the Congo/Tanzania cratonic nucleus in a manner very similar to the development of the Nipponides in east Asia, parts of the North American Cordillera and the Altaids. The entire Sahara is shown to be underlain by a double orocline much like the Hercynian double orocline in western Europe and northwestern Africa and not by an hypothetical ‘Saharan Metacraton’. The method here followed may be a fruitful procedure to untangle the structure of some of the Precambrian orogenic belts before life evolved sufficiently to make biostratigraphy feasible.
How to cite: Şengör, A. M. C., Lom, N., Zabcı, C., Sunal, G., and Öner, T.: The Saharides: Turkic-Type Orogeny in Afro-Arabia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5494, https://doi.org/10.5194/egusphere-egu21-5494, 2021.
GM11.1 – Planetary Geomorphology
EGU21-3585 | vPICO presentations | GM11.1
Polygonal impact craters reveal a global fracture pattern on MercuryIsik Su Yazici and Christian Klimczak
Mercury’s surface displays a rich history in impact cratering and tectonic activity, which both provide insight into the geological evolution of the innermost planet. Global contraction, the volume decrease of the planet associated with a long, sustained period of cooling, and tidal despinning, the slowing of rotation to lock Mercury in its current 3:2 spin-orbit resonance with the sun, are both thought to have played an important role on the observed systematic variations of preferred orientations of thrust fault-related landforms across the planet. While these landforms show preferred north-south orientations in the equatorial and mid-latitudes, they show random or concentric (east-west) orientations at the poles. Other fractures, such as joints, are likely present on Mercury, too, but their expressions are too subtle to be identified unless they are utilized as crater rims during the emplacement of impact craters. Fracture sets that existed in the bedrock prior to impact are widely accepted to produce crater rims showing straight rim segments that overall result in polygonal plan-view shapes of the impact structures, with perhaps the most prominent example Meteor Crater, Arizona. To test if regional fracture sets actually governed the shape of polygonal impact craters on Mercury, we have rigorously mapped all impact craters with diameters between 20 to 400 km. A total of 7,146 impact craters were mapped using Mercury Surface Space ENvironment GEochemistry and Ranging (MESSENGER) global image and topography datasets. After analyzing the shape, lengths, and orientations of 124,671 rim segments, we assessed if these rim segments contain additional information about systematic tectonic patterns. Our results show a strong preferred east-west orientation of straight crater rims at the poles, while in the mid-latitude and equatorial regions, they only have weak north-south or random orientations. That straight crater rims to show preferred east-west orientation at the poles is consistent with observed fault orientations by previous studies. However, we observe a lack of correlation of straight crater rim orientations and mapped faults at the equatorial and mid-latitudinal regions. These results have implications for and will enable further quantitative investigations of the global tectonics and fault reactivation on Mercury.
How to cite: Yazici, I. S. and Klimczak, C.: Polygonal impact craters reveal a global fracture pattern on Mercury, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3585, https://doi.org/10.5194/egusphere-egu21-3585, 2021.
Mercury’s surface displays a rich history in impact cratering and tectonic activity, which both provide insight into the geological evolution of the innermost planet. Global contraction, the volume decrease of the planet associated with a long, sustained period of cooling, and tidal despinning, the slowing of rotation to lock Mercury in its current 3:2 spin-orbit resonance with the sun, are both thought to have played an important role on the observed systematic variations of preferred orientations of thrust fault-related landforms across the planet. While these landforms show preferred north-south orientations in the equatorial and mid-latitudes, they show random or concentric (east-west) orientations at the poles. Other fractures, such as joints, are likely present on Mercury, too, but their expressions are too subtle to be identified unless they are utilized as crater rims during the emplacement of impact craters. Fracture sets that existed in the bedrock prior to impact are widely accepted to produce crater rims showing straight rim segments that overall result in polygonal plan-view shapes of the impact structures, with perhaps the most prominent example Meteor Crater, Arizona. To test if regional fracture sets actually governed the shape of polygonal impact craters on Mercury, we have rigorously mapped all impact craters with diameters between 20 to 400 km. A total of 7,146 impact craters were mapped using Mercury Surface Space ENvironment GEochemistry and Ranging (MESSENGER) global image and topography datasets. After analyzing the shape, lengths, and orientations of 124,671 rim segments, we assessed if these rim segments contain additional information about systematic tectonic patterns. Our results show a strong preferred east-west orientation of straight crater rims at the poles, while in the mid-latitude and equatorial regions, they only have weak north-south or random orientations. That straight crater rims to show preferred east-west orientation at the poles is consistent with observed fault orientations by previous studies. However, we observe a lack of correlation of straight crater rim orientations and mapped faults at the equatorial and mid-latitudinal regions. These results have implications for and will enable further quantitative investigations of the global tectonics and fault reactivation on Mercury.
How to cite: Yazici, I. S. and Klimczak, C.: Polygonal impact craters reveal a global fracture pattern on Mercury, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3585, https://doi.org/10.5194/egusphere-egu21-3585, 2021.
EGU21-4822 | vPICO presentations | GM11.1
Longitudinal Ridges in Long Runout Landslides: on the Applicability of High-Speed Granular Flow Mechanisms.Giulia Magnarini, Thomas Mitchell, Peter Grindrod, and Liran Goren
Long runout landslides are a particular type of mass-wasting phenomena that belongs to the category of surface processes associated with rapid strain rates. The reduction of friction that has to be invoked to explain their high velocities and exceptional travel distance over nearly horizontal surfaces has yet to find satisfactory explanation. Inspired by fault mechanics studies, thermally-activated mechanisms can explain the dynamic frictional strength loss during sliding along the initial failure surface and the early development of velocities higher than expected. However, as slides continue moving along nearly horizontal valley floors, the weakening mechanisms required to sustain their exceptional behaviour are less certain.
Long runout landslides are found ubiquitous in our solar system and the slow erosion rates that operate on extraterrestrial planetary bodies allow the preservation of their geomorphological record. The availability of the latest high-resolution imagery of the surface of Mars and the Moon allows to conduct detailed morphometric analysis not so granted on our planet. On the other hand, on Earth, the partial loss of the geomorphological record due to fast erosion rates is compensated by the accessibility of sites that enable us to conduct field work. In order to better understand the mechanisms responsible for the apparent friction weakening we use a comparative planetary geology approach, in the attempt to link the morphology and the internal structures of long runout landslide deposits to the mechanisms involved during the emplacement of such catastrophic events.
We focused on the distinctive longitudinal ridges that mark the surface of the landslide deposits. The formation mechanism of longitudinal ridges in long runout landslides has been proposed to require ice, as this low friction material would allow the spreading of the deposit, causing the development of longitudinal ridges by tensile deformation of the slide. However, ice-free laboratory experiments on rapid granular flows have demonstrated that longitudinal ridges can form as a consequence of helicoidal cells that generate from a mechanical instability, which onset requires a rough surface and a velocity threshold to be surpassed. Moreover, such experiments have showed that the wavelength of the longitudinal ridges is always 2 to 3 times the thickness of the flow.
We here present the results from three case studies: the 63-km-long Coprates Labe landslide in Valles Marineris on Mars; the 4-km-long El Magnifico landslide in Chile, Earth; and the 50-km-long Tsiolkovskiy crater landslide, at the far side of the Moon. We found that the wavelength of the longitudinal ridges is consistently 2 to 3 times the thickness of the landslide deposit, in agreement with experimental work on rapid granular flows. The recurrence of such scaling relationship suggests a scale- and environment-independent mechanism. We discuss the applicability of high-speed granular flow convection-style mechanisms to long runout landslides and speculate on the existence of an alternative vibration-assisted mechanism.
How to cite: Magnarini, G., Mitchell, T., Grindrod, P., and Goren, L.: Longitudinal Ridges in Long Runout Landslides: on the Applicability of High-Speed Granular Flow Mechanisms., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4822, https://doi.org/10.5194/egusphere-egu21-4822, 2021.
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Long runout landslides are a particular type of mass-wasting phenomena that belongs to the category of surface processes associated with rapid strain rates. The reduction of friction that has to be invoked to explain their high velocities and exceptional travel distance over nearly horizontal surfaces has yet to find satisfactory explanation. Inspired by fault mechanics studies, thermally-activated mechanisms can explain the dynamic frictional strength loss during sliding along the initial failure surface and the early development of velocities higher than expected. However, as slides continue moving along nearly horizontal valley floors, the weakening mechanisms required to sustain their exceptional behaviour are less certain.
Long runout landslides are found ubiquitous in our solar system and the slow erosion rates that operate on extraterrestrial planetary bodies allow the preservation of their geomorphological record. The availability of the latest high-resolution imagery of the surface of Mars and the Moon allows to conduct detailed morphometric analysis not so granted on our planet. On the other hand, on Earth, the partial loss of the geomorphological record due to fast erosion rates is compensated by the accessibility of sites that enable us to conduct field work. In order to better understand the mechanisms responsible for the apparent friction weakening we use a comparative planetary geology approach, in the attempt to link the morphology and the internal structures of long runout landslide deposits to the mechanisms involved during the emplacement of such catastrophic events.
We focused on the distinctive longitudinal ridges that mark the surface of the landslide deposits. The formation mechanism of longitudinal ridges in long runout landslides has been proposed to require ice, as this low friction material would allow the spreading of the deposit, causing the development of longitudinal ridges by tensile deformation of the slide. However, ice-free laboratory experiments on rapid granular flows have demonstrated that longitudinal ridges can form as a consequence of helicoidal cells that generate from a mechanical instability, which onset requires a rough surface and a velocity threshold to be surpassed. Moreover, such experiments have showed that the wavelength of the longitudinal ridges is always 2 to 3 times the thickness of the flow.
We here present the results from three case studies: the 63-km-long Coprates Labe landslide in Valles Marineris on Mars; the 4-km-long El Magnifico landslide in Chile, Earth; and the 50-km-long Tsiolkovskiy crater landslide, at the far side of the Moon. We found that the wavelength of the longitudinal ridges is consistently 2 to 3 times the thickness of the landslide deposit, in agreement with experimental work on rapid granular flows. The recurrence of such scaling relationship suggests a scale- and environment-independent mechanism. We discuss the applicability of high-speed granular flow convection-style mechanisms to long runout landslides and speculate on the existence of an alternative vibration-assisted mechanism.
How to cite: Magnarini, G., Mitchell, T., Grindrod, P., and Goren, L.: Longitudinal Ridges in Long Runout Landslides: on the Applicability of High-Speed Granular Flow Mechanisms., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4822, https://doi.org/10.5194/egusphere-egu21-4822, 2021.
EGU21-4803 | vPICO presentations | GM11.1
Pre-landslide topographic reconstruction using a Digital Elevation Model from CaSSIS onboard the Trace Gas Orbiter.Anthony Guimpier, Susan Conway, Maurizio Pajola, Alice Lucchetti, Emanuele Simioni, Cristina Re, Nicolas Mangold, Nicolas Thomas, and Gabriele Cremonese and the CaSSIS team
Landslides are common features on the surface of Mars. They have morphologies that resemble debris slides, mudflows [1], or giant rock avalanches [e.g., 2] on Earth. They can mobilise large quantities of material up to 1012 m3 and spread over areas of up to 109 m2 [e.g., 3].
The topography before the landslide event occurred is required to both estimate the volume of mobilised material and quantify the distribution and thickness of the deposit. The mass distribution of the deposit can also be used to compare with 3D flow simulations of landslides [e.g. 1, 3]. However, on Mars there are no landslides that have known topographic data before the event occurred, hence we have to rely on topographic reconstruction.
This type of reconstruction, which we have already carried out using HiRISE (High Resolution Imaging Science Experiment) Digital Elevation Models (DEM) with 1-2 m vertical resolution [e.g., 1], has never been undertaken using DEMs with 4-5 m vertical resolution derived from CaSSIS (Colour and Stereo Surface Imaging System) stereo pairs [4]. CaSSIS uses a 180° camera rotation to capture stereo images of a given site in a single pass. DEMs are then generated using 3DPD (three Dimensional reconstruction of Planetary Data) software [5].
Our aim is to test whether a landslide reconstruction can be carried out with a CaSSIS DEM. For our purpose we use a 6 km long landslide in Baetis Chaos region, Mars.
Our reconstruction consists of three main steps: 1) We first calculate contour lines. 2) Reconstructed contour lines are then drawn by connecting contour lines on either side of the boundary taking into account the overall topography outside the landslide. 3) Then, the reconstructed contour lines are converted into points at intervals equal to the spatial resolution of the DEM. These points are then interpolated using a natural neighbour algorithm to calculate a new DEM without the landslide. We were able to estimate that the landslide in Baetis Chaos has a volume of 108 m3 and the deposit has a maximum thickness of 200 m using CaSSIS data.
Our successful reconstruction using a CaSSIS DEM increases the potential coverage of high-resolution stereo-topographic data beyond those already available with CTX and/or HiRISE. The resolution CaSSIS DEMs fills a gap in the topographic data currently available for studying landslides. Landslides > 15 km long can be studied with MOLA or HRSC data, and landslides < 5 km long can be studied using HiRISE data. Now, landslides and other landforms 5-15 km can be studied using CaSSIS data with equivalent quality to CTX stereo-topography.
Acknowledgement: CaSSIS is a project of the University of Bern, with instrument hardware development supported by INAF/Astronomical Observatory of Padova (ASI-INAF agreement n.2020-17-HH.0), and the Space Research Center (CBK) in Warsaw.
References: [1] A. Guimpier et al. (In review) PSS. [2] G. Magnarini et al. (2019) Nature Communications. [3] G.B. Crosta et al. (2018) ESS, 5, 89–119. [4] A. Lucas et al. (2014) Nature Communications. [5] E. Simioni et al. (In press) PSS.
How to cite: Guimpier, A., Conway, S., Pajola, M., Lucchetti, A., Simioni, E., Re, C., Mangold, N., Thomas, N., and Cremonese, G. and the CaSSIS team: Pre-landslide topographic reconstruction using a Digital Elevation Model from CaSSIS onboard the Trace Gas Orbiter., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4803, https://doi.org/10.5194/egusphere-egu21-4803, 2021.
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Landslides are common features on the surface of Mars. They have morphologies that resemble debris slides, mudflows [1], or giant rock avalanches [e.g., 2] on Earth. They can mobilise large quantities of material up to 1012 m3 and spread over areas of up to 109 m2 [e.g., 3].
The topography before the landslide event occurred is required to both estimate the volume of mobilised material and quantify the distribution and thickness of the deposit. The mass distribution of the deposit can also be used to compare with 3D flow simulations of landslides [e.g. 1, 3]. However, on Mars there are no landslides that have known topographic data before the event occurred, hence we have to rely on topographic reconstruction.
This type of reconstruction, which we have already carried out using HiRISE (High Resolution Imaging Science Experiment) Digital Elevation Models (DEM) with 1-2 m vertical resolution [e.g., 1], has never been undertaken using DEMs with 4-5 m vertical resolution derived from CaSSIS (Colour and Stereo Surface Imaging System) stereo pairs [4]. CaSSIS uses a 180° camera rotation to capture stereo images of a given site in a single pass. DEMs are then generated using 3DPD (three Dimensional reconstruction of Planetary Data) software [5].
Our aim is to test whether a landslide reconstruction can be carried out with a CaSSIS DEM. For our purpose we use a 6 km long landslide in Baetis Chaos region, Mars.
Our reconstruction consists of three main steps: 1) We first calculate contour lines. 2) Reconstructed contour lines are then drawn by connecting contour lines on either side of the boundary taking into account the overall topography outside the landslide. 3) Then, the reconstructed contour lines are converted into points at intervals equal to the spatial resolution of the DEM. These points are then interpolated using a natural neighbour algorithm to calculate a new DEM without the landslide. We were able to estimate that the landslide in Baetis Chaos has a volume of 108 m3 and the deposit has a maximum thickness of 200 m using CaSSIS data.
Our successful reconstruction using a CaSSIS DEM increases the potential coverage of high-resolution stereo-topographic data beyond those already available with CTX and/or HiRISE. The resolution CaSSIS DEMs fills a gap in the topographic data currently available for studying landslides. Landslides > 15 km long can be studied with MOLA or HRSC data, and landslides < 5 km long can be studied using HiRISE data. Now, landslides and other landforms 5-15 km can be studied using CaSSIS data with equivalent quality to CTX stereo-topography.
Acknowledgement: CaSSIS is a project of the University of Bern, with instrument hardware development supported by INAF/Astronomical Observatory of Padova (ASI-INAF agreement n.2020-17-HH.0), and the Space Research Center (CBK) in Warsaw.
References: [1] A. Guimpier et al. (In review) PSS. [2] G. Magnarini et al. (2019) Nature Communications. [3] G.B. Crosta et al. (2018) ESS, 5, 89–119. [4] A. Lucas et al. (2014) Nature Communications. [5] E. Simioni et al. (In press) PSS.
How to cite: Guimpier, A., Conway, S., Pajola, M., Lucchetti, A., Simioni, E., Re, C., Mangold, N., Thomas, N., and Cremonese, G. and the CaSSIS team: Pre-landslide topographic reconstruction using a Digital Elevation Model from CaSSIS onboard the Trace Gas Orbiter., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4803, https://doi.org/10.5194/egusphere-egu21-4803, 2021.
EGU21-9628 | vPICO presentations | GM11.1
Molards as an analogue for ejecta-ice interactions on MarsCostanza Morino, Susan Conway, Coralie Peignaux, Antoine Lucas, Kristian Svennevig, Frances Butcher, Gioachino Roberti, Meven Philippe, and Jake Collins-May
The 125-km-diameter Hale impact crater is located in the southern hemisphere of Mars and has been dated to 1 Ga (Early to Middle Amazonian; Jones et al., 2011). It is thought to have penetrated the martian cryosphere, because it hosts landforms indicating volatile mobilisation post-impact: its ejecta are lobate and bear channels, and the interior is pervasively pitted and hosts alluvial fans (Collins-May et al. 2020; El-Maarry et al., 2013; Jones et al., 2011; Tornabene et al., 2012). Here, we test the hypothesis that conical mounds found within the ejecta are “molards” by comparing them to terrestrial analogues. Molards are conical mounds of debris resulting from the degradation of blocks of ice-rich material which have been mobilised by a landslide and are found in periglacial environments (Morino et al., 2019).
Our study area (240x180 km) is in the South-East part of the Hale impact crater ejecta (36°–39°S, 36°–31°W). We analyse the spatial and topographic distribution of the conical mounds using orbital images from 25 cm/pixel to 15 m/pixel and measure their height, width and slope using 1 m/pixel elevation data. We then compare them to conical mounds on the deposits of the 2010 Mount Meager debris avalanche, Canada (Roberti et al. 2017) and of the 2000 Paatuut landslide in western Greenland (Dahl-Jensen et al. 2004).
The conical mounds of the Hale impact crater are located at the distal boundary of the thickest part of the ejecta blanket, which reflects the spatial distribution of mounds along the distal parts of the terminal lobe of the Mount Meager debris avalanche. Furthermore, mounds in the Hale impact crater have comparable shapes and flank slopes to molards in the Mount Meager and Paatuut case studies, but are one order of magnitude bigger. This size difference is consistent with the flow-depth that transported the blocks also being one order of magnitude bigger than on Earth.
We infer that conical mounds near the Hale impact crater are a result of fragmented blocks of ice-cemented regolith produced by the impact and transported by the ejecta flows, and finally degraded into cones of debris (molards) by the loss of interstitial ice. Our interpretation supports the prevailing hypothesis that the Hale impact event penetrated the martian cryosphere and further provides important constraints on the rheology of martian ejecta deposits that can be tested by future studies and in other locations on Mars.
We acknowledge financial support for the PERMOLARDS project from French National Research Agency (ANR-19-CE01-0010).
How to cite: Morino, C., Conway, S., Peignaux, C., Lucas, A., Svennevig, K., Butcher, F., Roberti, G., Philippe, M., and Collins-May, J.: Molards as an analogue for ejecta-ice interactions on Mars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9628, https://doi.org/10.5194/egusphere-egu21-9628, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The 125-km-diameter Hale impact crater is located in the southern hemisphere of Mars and has been dated to 1 Ga (Early to Middle Amazonian; Jones et al., 2011). It is thought to have penetrated the martian cryosphere, because it hosts landforms indicating volatile mobilisation post-impact: its ejecta are lobate and bear channels, and the interior is pervasively pitted and hosts alluvial fans (Collins-May et al. 2020; El-Maarry et al., 2013; Jones et al., 2011; Tornabene et al., 2012). Here, we test the hypothesis that conical mounds found within the ejecta are “molards” by comparing them to terrestrial analogues. Molards are conical mounds of debris resulting from the degradation of blocks of ice-rich material which have been mobilised by a landslide and are found in periglacial environments (Morino et al., 2019).
Our study area (240x180 km) is in the South-East part of the Hale impact crater ejecta (36°–39°S, 36°–31°W). We analyse the spatial and topographic distribution of the conical mounds using orbital images from 25 cm/pixel to 15 m/pixel and measure their height, width and slope using 1 m/pixel elevation data. We then compare them to conical mounds on the deposits of the 2010 Mount Meager debris avalanche, Canada (Roberti et al. 2017) and of the 2000 Paatuut landslide in western Greenland (Dahl-Jensen et al. 2004).
The conical mounds of the Hale impact crater are located at the distal boundary of the thickest part of the ejecta blanket, which reflects the spatial distribution of mounds along the distal parts of the terminal lobe of the Mount Meager debris avalanche. Furthermore, mounds in the Hale impact crater have comparable shapes and flank slopes to molards in the Mount Meager and Paatuut case studies, but are one order of magnitude bigger. This size difference is consistent with the flow-depth that transported the blocks also being one order of magnitude bigger than on Earth.
We infer that conical mounds near the Hale impact crater are a result of fragmented blocks of ice-cemented regolith produced by the impact and transported by the ejecta flows, and finally degraded into cones of debris (molards) by the loss of interstitial ice. Our interpretation supports the prevailing hypothesis that the Hale impact event penetrated the martian cryosphere and further provides important constraints on the rheology of martian ejecta deposits that can be tested by future studies and in other locations on Mars.
We acknowledge financial support for the PERMOLARDS project from French National Research Agency (ANR-19-CE01-0010).
How to cite: Morino, C., Conway, S., Peignaux, C., Lucas, A., Svennevig, K., Butcher, F., Roberti, G., Philippe, M., and Collins-May, J.: Molards as an analogue for ejecta-ice interactions on Mars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9628, https://doi.org/10.5194/egusphere-egu21-9628, 2021.
EGU21-12574 | vPICO presentations | GM11.1
Comparison of the Uzboi Vallis and Nirgal Vallis (Mars) using swath analysisAndrás Szilágyi-Sándor and Balázs Székely
The presumably fluvially affected surfaces of Mars provide evidence of the variety of surface processes of the past of the planet. Throughout its history, the climate has enabled the presence of liquid water several times (perhaps periodically). Watercourses and mega-river systems have ruled the surface; their tracks are still recognizable in many places. The Argyre Crater might have served as the source of such a huge river system: the Uzboi–Ladon–Morava River System (ULM), during the Late Noachian. (Dohm et al 2015) ULM is therefore fundamentally different from most of the valleys and channels of Mars as it is not an amphitheatre-headed valley, it is composed of various types of sections, and its source is connected to a large crater. In this study Uzboi Vallis, a section of ULM was studied using data from the Mars Global Surveyor's Mars Orbiter Laser Altimeter (MOLA) data. A comparison is presented of Uzboi Vallis and its tributary, Nirgal Vallis. In addition to creating the stream orders of the valleys and traditional elevation profiles, we used the swath profile analysis method. The swath analysis is fundamentally different from elevation profiles that enhance the specific Martian conditions (impact cratering, the complete absence of the biosphere, less gravity). In addition to the swath analysis completely covering the two studied areas, several regions of the catchment were specifically analyzed. According to the results obtained, the Uzboi Vallis is at least partly tectonically modified. Based on these observations, in the northeastern part, half-graben structures are hypothesized. The method of swath profile analysis, previously not applied to Martian data, proved to be useful and provided interpretable data for the surface of a planet other than Earth.
Geomorphometric studies on terrain models are found to provide interesting information paving the way towards an in-depth understanding of this mega river system. Further analysis of the ULM is planned in the near future.
Dohm, J.M., Hare, T.M., Robbins, S.J., Williams, J.-P., Soare, R.J., El-Maarry, M.R., Conway, S.J., Buczkowski, D.L., Kargel, J.S., Banks, M.E., Fairén, A.G., Schulze-Makuch, D., Komatsu, G., Miyamoto, H., Anderson, R.C., Davila, A.F., Mahaney, W.C., Fink, W., Cleaves, H.J., Yan, J., Hynek, B., Maruyama, S. (2015): Geological and hydrological histories of the Argyre province, Mars. Icarus 253:66–98.
How to cite: Szilágyi-Sándor, A. and Székely, B.: Comparison of the Uzboi Vallis and Nirgal Vallis (Mars) using swath analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12574, https://doi.org/10.5194/egusphere-egu21-12574, 2021.
The presumably fluvially affected surfaces of Mars provide evidence of the variety of surface processes of the past of the planet. Throughout its history, the climate has enabled the presence of liquid water several times (perhaps periodically). Watercourses and mega-river systems have ruled the surface; their tracks are still recognizable in many places. The Argyre Crater might have served as the source of such a huge river system: the Uzboi–Ladon–Morava River System (ULM), during the Late Noachian. (Dohm et al 2015) ULM is therefore fundamentally different from most of the valleys and channels of Mars as it is not an amphitheatre-headed valley, it is composed of various types of sections, and its source is connected to a large crater. In this study Uzboi Vallis, a section of ULM was studied using data from the Mars Global Surveyor's Mars Orbiter Laser Altimeter (MOLA) data. A comparison is presented of Uzboi Vallis and its tributary, Nirgal Vallis. In addition to creating the stream orders of the valleys and traditional elevation profiles, we used the swath profile analysis method. The swath analysis is fundamentally different from elevation profiles that enhance the specific Martian conditions (impact cratering, the complete absence of the biosphere, less gravity). In addition to the swath analysis completely covering the two studied areas, several regions of the catchment were specifically analyzed. According to the results obtained, the Uzboi Vallis is at least partly tectonically modified. Based on these observations, in the northeastern part, half-graben structures are hypothesized. The method of swath profile analysis, previously not applied to Martian data, proved to be useful and provided interpretable data for the surface of a planet other than Earth.
Geomorphometric studies on terrain models are found to provide interesting information paving the way towards an in-depth understanding of this mega river system. Further analysis of the ULM is planned in the near future.
Dohm, J.M., Hare, T.M., Robbins, S.J., Williams, J.-P., Soare, R.J., El-Maarry, M.R., Conway, S.J., Buczkowski, D.L., Kargel, J.S., Banks, M.E., Fairén, A.G., Schulze-Makuch, D., Komatsu, G., Miyamoto, H., Anderson, R.C., Davila, A.F., Mahaney, W.C., Fink, W., Cleaves, H.J., Yan, J., Hynek, B., Maruyama, S. (2015): Geological and hydrological histories of the Argyre province, Mars. Icarus 253:66–98.
How to cite: Szilágyi-Sándor, A. and Székely, B.: Comparison of the Uzboi Vallis and Nirgal Vallis (Mars) using swath analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12574, https://doi.org/10.5194/egusphere-egu21-12574, 2021.
EGU21-5832 | vPICO presentations | GM11.1
Automated Mapping of Radar-Dark Fluvial Features on Saturn's Moon, TitanElizabeth Skaggs
Titan, Saturn's moon, is the only body in our solar system besides Earth to have liquids on its surface in the form of lakes, rivers, and seas - although the liquids are mainly hydrocarbons like methane and ethane. The liquids on Titan appear to flow in similar ways to those on Earth and create comparable fluvial patterns such as meandering rivers and dendritic fluvial systems. This project utilizes SAR data obtained from the Cassini-Huygens mission via Titan Trek to identify networks of inferred fluvial systems. We focus on data swaths T28 and T29 surrounding Ligeia Mare and Kraken Mare between 210 and 360 Longitude in Titan’s northern hemisphere. Previous studies (e.g. Burr et al., 2013) interpreted fluvial networks, principally from radar-light features. We focus on radar-dark features, applying an automated technique from Yang et al (2015) to map networks of presumed fluvial origin and compare them with our own visual mapping. Yang et al. used these automated techniques to map various known fluvial systems on Earth that appear radar-dark. Our application of the technique to the Titan study area is successful in identifying features that we had mapped by hand and other features that we had not identified in our visual mapping. The technique was more successful for imagery with less noise and less successful as noise level increased. The automated technique shows great promise for more widespread, rapid identification and mapping of the fluvial network.
How to cite: Skaggs, E.: Automated Mapping of Radar-Dark Fluvial Features on Saturn's Moon, Titan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5832, https://doi.org/10.5194/egusphere-egu21-5832, 2021.
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Titan, Saturn's moon, is the only body in our solar system besides Earth to have liquids on its surface in the form of lakes, rivers, and seas - although the liquids are mainly hydrocarbons like methane and ethane. The liquids on Titan appear to flow in similar ways to those on Earth and create comparable fluvial patterns such as meandering rivers and dendritic fluvial systems. This project utilizes SAR data obtained from the Cassini-Huygens mission via Titan Trek to identify networks of inferred fluvial systems. We focus on data swaths T28 and T29 surrounding Ligeia Mare and Kraken Mare between 210 and 360 Longitude in Titan’s northern hemisphere. Previous studies (e.g. Burr et al., 2013) interpreted fluvial networks, principally from radar-light features. We focus on radar-dark features, applying an automated technique from Yang et al (2015) to map networks of presumed fluvial origin and compare them with our own visual mapping. Yang et al. used these automated techniques to map various known fluvial systems on Earth that appear radar-dark. Our application of the technique to the Titan study area is successful in identifying features that we had mapped by hand and other features that we had not identified in our visual mapping. The technique was more successful for imagery with less noise and less successful as noise level increased. The automated technique shows great promise for more widespread, rapid identification and mapping of the fluvial network.
How to cite: Skaggs, E.: Automated Mapping of Radar-Dark Fluvial Features on Saturn's Moon, Titan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5832, https://doi.org/10.5194/egusphere-egu21-5832, 2021.
EGU21-6865 | vPICO presentations | GM11.1
Paleohydraulic investigation of the Ebro Basin: Implications for MarsHeath Geil-Haggerty
The stratigraphy preserved in Earth’s sedimentary basins offers a record of how landscapes have evolved with time. This stratigraphy provides insights into the dynamic processes that shaped the surface of the earth. Fluvial stratigraphy contains many elements that can be used to recreate past conditions in ancient river channels. Paleohydraulic reconstruction uses measurements of fluvial stratigraphy to model the conditions in the system that created them. This allows us to answer questions related to water discharge, sediment flux, and duration of fluvial activity. These are key questions when investigated in the context of Mars. Paleohydraulic models can be used as compelling analogs for similar systems on Earth as well as Mars and other rocky planets.
This study examines what the record of Oligocene-Miocene fluvial stratigraphy in northeastern Spain’s Ebro Basin can tell us about water discharge and sediment flux across distributive fluvial systems at a basin scale. The Cenozoic stratigraphy of northeastern Spain’s triangular shaped Ebro Basin embodies a classic example of the formation of a closed sedimentary basin. The Ebro Basin contains a number of remarkably well exposed fluvial sedimentary deposits. These deposits outcrop as distinctive laterally contiguous channel sand bodies. Clastic sediment supply in the Ebro Basin is largely governed by tectonic uplift and basin subsidence related to the Pyrenean orogen with peripheral contributions from the Catalan Coast and Iberian Ranges. We test the idea that the record of conditions in the fluvial systems should reflect the record of lacustrine chemical sediments through sediment mass conservation. In order to test this hypothesis measurements of bedform height, barform height, sediment size, and paleochannel dimensions were collected in the field. Our paleohydraulic model uses previously derived theoretical and empirical relationships to recreate the conditions in these ancient fluvial systems. These results are scaled up by accounting for drainage density and intermittency in order to address the principal question at a basin scale. Paleodischarges from the fluvial sediments are comparable to those from river chemistry calculations for the lacustrine facies.
How to cite: Geil-Haggerty, H.: Paleohydraulic investigation of the Ebro Basin: Implications for Mars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6865, https://doi.org/10.5194/egusphere-egu21-6865, 2021.
The stratigraphy preserved in Earth’s sedimentary basins offers a record of how landscapes have evolved with time. This stratigraphy provides insights into the dynamic processes that shaped the surface of the earth. Fluvial stratigraphy contains many elements that can be used to recreate past conditions in ancient river channels. Paleohydraulic reconstruction uses measurements of fluvial stratigraphy to model the conditions in the system that created them. This allows us to answer questions related to water discharge, sediment flux, and duration of fluvial activity. These are key questions when investigated in the context of Mars. Paleohydraulic models can be used as compelling analogs for similar systems on Earth as well as Mars and other rocky planets.
This study examines what the record of Oligocene-Miocene fluvial stratigraphy in northeastern Spain’s Ebro Basin can tell us about water discharge and sediment flux across distributive fluvial systems at a basin scale. The Cenozoic stratigraphy of northeastern Spain’s triangular shaped Ebro Basin embodies a classic example of the formation of a closed sedimentary basin. The Ebro Basin contains a number of remarkably well exposed fluvial sedimentary deposits. These deposits outcrop as distinctive laterally contiguous channel sand bodies. Clastic sediment supply in the Ebro Basin is largely governed by tectonic uplift and basin subsidence related to the Pyrenean orogen with peripheral contributions from the Catalan Coast and Iberian Ranges. We test the idea that the record of conditions in the fluvial systems should reflect the record of lacustrine chemical sediments through sediment mass conservation. In order to test this hypothesis measurements of bedform height, barform height, sediment size, and paleochannel dimensions were collected in the field. Our paleohydraulic model uses previously derived theoretical and empirical relationships to recreate the conditions in these ancient fluvial systems. These results are scaled up by accounting for drainage density and intermittency in order to address the principal question at a basin scale. Paleodischarges from the fluvial sediments are comparable to those from river chemistry calculations for the lacustrine facies.
How to cite: Geil-Haggerty, H.: Paleohydraulic investigation of the Ebro Basin: Implications for Mars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6865, https://doi.org/10.5194/egusphere-egu21-6865, 2021.
EGU21-5971 | vPICO presentations | GM11.1
Delta Deposits on Mars: A Global PerspectiveBarbara De Toffoli, Ana-Catalina Plesa, Ernst Hauber, and Doris Breuer
The presence of delta deposits on Mars has been thoroughly demonstrated for decades and large scale mapping [1,2] highlighted the presence of several delta fans mainly located on the dichotomy boundary. While a previous delta inventory was compiled by Morgan et al. [3], we aim to update and finalize a complete mapping of delta deposits in order to allow the examination of the evolution and distribution of standing bodies of water on Mars. The objective of our project focuses on the production of a global catalogue of water-related features at the Martian surface, which are commonly studied separately or at smaller scales.
Globally, we located around 150 deltas among which many were not previously included in published literature [e.g. 1,2,4]. We then examined the deltas based on two main traits. Firstly, we measured the length of the feeding channels since it may be (i) a proxy for the duration of the aqueous activity in the channel-delta system, and (ii) proportional to the age of the delta [2]. The latter relationship links older deltas near Chryse Planitia (>3 Ga) to longer valleys, while younger deltas are usually fed by shorter valleys [2]. Secondly, we measured the elevation of the delta population and compared the obtained dataset with the hypothesized sea level elevation of -2540 ± 177 m firstly suggested by Di Achille and Hynek [1] for a northern ocean through the analysis of deltas.
We observed that, if the relationship between feeding channel length and delta age found for a sub-group of the population [2] is applicable as a rule of thumb to all deltas, many of the deposits have the potential to be Hesperian or Amazonian in age. They would thus be younger than the ocean that might have occupied the northern lowlands during the Noachian-Hesperian boundary period [1] and thus be unrelated to a global sea level range. In fact, less than half of the delta population is related to medium/long feeding channels (>30 km). Abundant pristine morphologies, both related to channels and deltas, also supports the hypothesis that part of the population is younger than Noachian. Additionally, the large variety of elevations where the deltaic deposits can be found and the very small amount of deltas included in the sea level elevation range proposed by Di Achille and Hynek [1] raise questions about the generation and environmental implications of these features, especially when seen at global scale.
[1] Di Achille, G. & Hynek, B. M., Nat. Geosci. 3, 459–463 (2010).
[2] Hauber, E. et al., J. Geophys. Res. E Planets 118, 1529–1544 (2013).
[3] Morgan, A. M., et al., Lunar Planet. Sci. Conf. (2018).
[4] Ori, G.G. et al., J. Geophys. Res. E Planets 105, 17629–17641 (2000).
How to cite: De Toffoli, B., Plesa, A.-C., Hauber, E., and Breuer, D.: Delta Deposits on Mars: A Global Perspective, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5971, https://doi.org/10.5194/egusphere-egu21-5971, 2021.
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The presence of delta deposits on Mars has been thoroughly demonstrated for decades and large scale mapping [1,2] highlighted the presence of several delta fans mainly located on the dichotomy boundary. While a previous delta inventory was compiled by Morgan et al. [3], we aim to update and finalize a complete mapping of delta deposits in order to allow the examination of the evolution and distribution of standing bodies of water on Mars. The objective of our project focuses on the production of a global catalogue of water-related features at the Martian surface, which are commonly studied separately or at smaller scales.
Globally, we located around 150 deltas among which many were not previously included in published literature [e.g. 1,2,4]. We then examined the deltas based on two main traits. Firstly, we measured the length of the feeding channels since it may be (i) a proxy for the duration of the aqueous activity in the channel-delta system, and (ii) proportional to the age of the delta [2]. The latter relationship links older deltas near Chryse Planitia (>3 Ga) to longer valleys, while younger deltas are usually fed by shorter valleys [2]. Secondly, we measured the elevation of the delta population and compared the obtained dataset with the hypothesized sea level elevation of -2540 ± 177 m firstly suggested by Di Achille and Hynek [1] for a northern ocean through the analysis of deltas.
We observed that, if the relationship between feeding channel length and delta age found for a sub-group of the population [2] is applicable as a rule of thumb to all deltas, many of the deposits have the potential to be Hesperian or Amazonian in age. They would thus be younger than the ocean that might have occupied the northern lowlands during the Noachian-Hesperian boundary period [1] and thus be unrelated to a global sea level range. In fact, less than half of the delta population is related to medium/long feeding channels (>30 km). Abundant pristine morphologies, both related to channels and deltas, also supports the hypothesis that part of the population is younger than Noachian. Additionally, the large variety of elevations where the deltaic deposits can be found and the very small amount of deltas included in the sea level elevation range proposed by Di Achille and Hynek [1] raise questions about the generation and environmental implications of these features, especially when seen at global scale.
[1] Di Achille, G. & Hynek, B. M., Nat. Geosci. 3, 459–463 (2010).
[2] Hauber, E. et al., J. Geophys. Res. E Planets 118, 1529–1544 (2013).
[3] Morgan, A. M., et al., Lunar Planet. Sci. Conf. (2018).
[4] Ori, G.G. et al., J. Geophys. Res. E Planets 105, 17629–17641 (2000).
How to cite: De Toffoli, B., Plesa, A.-C., Hauber, E., and Breuer, D.: Delta Deposits on Mars: A Global Perspective, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5971, https://doi.org/10.5194/egusphere-egu21-5971, 2021.
EGU21-1742 | vPICO presentations | GM11.1
Discordance Mapping of Argyre Basin: An Insight into the Fluvial and Subglacial Origin of Valley Networks in the Argyre Basin RegionRickbir Bahia, Anna Galofre, Stephen Covey-Crump, Merren Jones, and Neil Mitchell
Introduction: Martian valley networks are evidence for surface run-off and past water cycles on ancient Mars. Many of the networks resemble terrestrial precipitation-fed systems; however, recent analysis has found that the geometries and morphological characteristics of some valley networks are more comparable to subglacial valley formation. Subglacial valleys have morphological characteristics that make them distinct from fluvial valley systems (i.e., those formed via precipitation or sapping erosion). Unlike fluvial valley networks, which follow the surface slope of the underlying topography, sub-glacial networks are orientated in the direction of the surface slope of the overlying ice-sheet. Therefore, subglacial valleys may have orientations that are discordant with the underlying topography. Discordance analysis, a technique that compares the valley paleoslope direction and topographic slope direction, has been applied to Mars to determine areas that have undergone topographic modification since valley formation. This technique could also be a tool for identify valleys with potential sub-glacial origins.
In this study, we mapped and applied discordance analysis to valley networks in and around Argyre basin. Detailed analysis was performed on four valley networks on eastern Argyre, to determine whether their characteristics are indicative of a fluvial or sub-glacial origin.
Results: 2669 V-Shaped valleys (total length = 36155.5 km) and 45 U-Shaped valleys (total length = 2683.5 km) were identified. Most V-Shaped valleys dissect the eastern and northern rim of Argyre Basin, with fewer in the south and west. The densest northern valley networks have values up to 0.098 km-1, compared to the densest in the south with values of only 0.040 km-1. U-Shaped valleys are prominent along the south/south-west rim, but are lacking along the northern rim of Argyre.
Most valleys (47.8 %) are concordant (< 45° discordance) with present slope direction. Two dense groups of discordant valleys are present adjacent to Hale Crater and Nia Vallis. These areas display features associated with the presence of an ice-sheet/glacier – e.g., glacial moraines and eskers. Additionally, the morphology of these valley systems are consistent with a subglacial origin.
Fento Vallis and the Darwin Crater valley system are concordant with present topographic slope, and are in close proximity to one another; however, their morphologies differ greatly. Fento Vallis consists of 25 valleys (total valley length of ~ 690 km) and drainage density of 0.019 km-1. The Darwin Crater valley network consists of 49 valleys (total valley length of ~ 1351 km) and drainage density of 0.048 km-1. Fento Vallis displays features (e.g., inner channel eskers) indicative of a subglacial origin. Alternatively, the Darwin Crater System has a planform associated with fluvial activity and originates from cirque like depressions. Although the Darwin Crater system appears to have a fluvial origin, less than 100 km to the east is Pallacopas Vallis, which displays inner eskers indicating that it has a subglacial origin.
Three of the networks analysed, which are > 1000 km apart from one another, are likely subglacial in origin. Their occurrence indicates that an ice-sheet or multiple ice-sheets were present along the eastern region of Argyre throughout its history.
How to cite: Bahia, R., Galofre, A., Covey-Crump, S., Jones, M., and Mitchell, N.: Discordance Mapping of Argyre Basin: An Insight into the Fluvial and Subglacial Origin of Valley Networks in the Argyre Basin Region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1742, https://doi.org/10.5194/egusphere-egu21-1742, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Introduction: Martian valley networks are evidence for surface run-off and past water cycles on ancient Mars. Many of the networks resemble terrestrial precipitation-fed systems; however, recent analysis has found that the geometries and morphological characteristics of some valley networks are more comparable to subglacial valley formation. Subglacial valleys have morphological characteristics that make them distinct from fluvial valley systems (i.e., those formed via precipitation or sapping erosion). Unlike fluvial valley networks, which follow the surface slope of the underlying topography, sub-glacial networks are orientated in the direction of the surface slope of the overlying ice-sheet. Therefore, subglacial valleys may have orientations that are discordant with the underlying topography. Discordance analysis, a technique that compares the valley paleoslope direction and topographic slope direction, has been applied to Mars to determine areas that have undergone topographic modification since valley formation. This technique could also be a tool for identify valleys with potential sub-glacial origins.
In this study, we mapped and applied discordance analysis to valley networks in and around Argyre basin. Detailed analysis was performed on four valley networks on eastern Argyre, to determine whether their characteristics are indicative of a fluvial or sub-glacial origin.
Results: 2669 V-Shaped valleys (total length = 36155.5 km) and 45 U-Shaped valleys (total length = 2683.5 km) were identified. Most V-Shaped valleys dissect the eastern and northern rim of Argyre Basin, with fewer in the south and west. The densest northern valley networks have values up to 0.098 km-1, compared to the densest in the south with values of only 0.040 km-1. U-Shaped valleys are prominent along the south/south-west rim, but are lacking along the northern rim of Argyre.
Most valleys (47.8 %) are concordant (< 45° discordance) with present slope direction. Two dense groups of discordant valleys are present adjacent to Hale Crater and Nia Vallis. These areas display features associated with the presence of an ice-sheet/glacier – e.g., glacial moraines and eskers. Additionally, the morphology of these valley systems are consistent with a subglacial origin.
Fento Vallis and the Darwin Crater valley system are concordant with present topographic slope, and are in close proximity to one another; however, their morphologies differ greatly. Fento Vallis consists of 25 valleys (total valley length of ~ 690 km) and drainage density of 0.019 km-1. The Darwin Crater valley network consists of 49 valleys (total valley length of ~ 1351 km) and drainage density of 0.048 km-1. Fento Vallis displays features (e.g., inner channel eskers) indicative of a subglacial origin. Alternatively, the Darwin Crater System has a planform associated with fluvial activity and originates from cirque like depressions. Although the Darwin Crater system appears to have a fluvial origin, less than 100 km to the east is Pallacopas Vallis, which displays inner eskers indicating that it has a subglacial origin.
Three of the networks analysed, which are > 1000 km apart from one another, are likely subglacial in origin. Their occurrence indicates that an ice-sheet or multiple ice-sheets were present along the eastern region of Argyre throughout its history.
How to cite: Bahia, R., Galofre, A., Covey-Crump, S., Jones, M., and Mitchell, N.: Discordance Mapping of Argyre Basin: An Insight into the Fluvial and Subglacial Origin of Valley Networks in the Argyre Basin Region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1742, https://doi.org/10.5194/egusphere-egu21-1742, 2021.
EGU21-2717 | vPICO presentations | GM11.1
Sinuous Ridges and the History of Fluvial and Glaciofluvial Activity in Chukhung Crater, Tempe Terra, Mars.Frances E. G. Butcher, Matthew R. Balme, Susan J. Conway, Colman Gallagher, Neil S. Arnold, Robert D. Storrar, Stephen R. Lewis, Axel Hagermann, and Joel M. Davis
We explore the origins of a complex assemblage of sinuous ridges in Chukhung crater (38.47°N, 72.42°W), Tempe Terra, Mars, and discuss the implications of the landsystem for post-Noachian fluvial and glaciofluvial activity in this location [1].
We produced a geomorphic map of Chukhung crater using a basemap of 6 m/pixel Context Camera (CTX) images and a 75 m/pixel High Resolution Stereo Camera digital elevation model (DEM). We used 25 cm/pixel High Resolution Imaging Science Experiment images, and a 24 cm/pixel DEM generated from CTX stereopair images [2] to aid classifications of sinuous ridges into four morpho-stratigraphic subtypes. We constrained an age envelope of ~2.1–3.6 Ga for Chukhung crater using modelled ages (from crater size-frequency analyses) of units above and below it in the regional stratigraphy. We derived a minimum model age of ~330 Ma for viscous flow features (putative debris-covered glaciers) in southern Chukhung crater.
Sinuous ridges in southern Chukhung crater emerge from moraine-like deposits associated with the debris-covered glaciers. Sinuous ridges in northern Chukhung crater extend from dendritic fluvial valley networks on the crater wall. The northern sinuous ridges are most likely to be inverted palaeochannels, which comprise subaerial river sediments exhumed as ridges by erosion of surrounding materials.
Both sinuous ridge subtypes in southern Chukhung crater have numerous esker-like properties. Eskers are ridges of glaciofluvial sediment deposited in meltwater tunnels within or beneath glacial ice. One of the ridge subtypes in southern Chukhung crater is best explained as eskers because these ridges ascend the sides of their host valleys and, in places, escape over them onto adjacent plains. Post-depositional processes can cause inverted paleochannels to cross local undulations in the contemporary topography [3] but the ascent and escape over larger, pre-existing topographic divides is (as yet) not adequately explained by these mechanisms. Eskers, in contrast, form under hydraulic pressure in ice-confined tunnels, and commonly ascend valley walls and cross topographic divides. The esker-like properties of the second sinuous ridge subtype in southern Chukhung crater can also be explained under the inverted palaeochannel hypothesis so the origins of these ridges remain more ambiguous.
Chukhung crater has undergone protracted and/or episodic modification by liquid water since its formation between the early Hesperian and early Amazonian. This falls after the Noachian period (>3.7 Ga), when most major fluvial activity on Mars occurred. Esker-forming wet-based glaciation in Chukhung crater might have occurred as recently as the mid Amazonian (>330 Ma), when climate conditions are thought to have been cold and hyper-arid. Rare occurrences of eskers associated with Amazonian-aged glaciers in Mars’ mid-latitudes are attributed to transient, localised geothermal heating within tectonic rift/graben settings [4]. The location of Chukhung crater between major branches of the large Tempe Fossae volcano-tectonic rift system is consistent with this hypothesis.
References: [1] Butcher et al. 2021, Icarus 357, 114131. [2] Mayer and Kite 2016, Lunar Planet. Sci. Conf. Abstract #1241. [3] Lefort et al. 2012, J. Geophys. Res. Planets 117, E03007. [4] Butcher et al. 2017, J. Geophys. Res. Planets 122, 2445–2468.
How to cite: Butcher, F. E. G., Balme, M. R., Conway, S. J., Gallagher, C., Arnold, N. S., Storrar, R. D., Lewis, S. R., Hagermann, A., and Davis, J. M.: Sinuous Ridges and the History of Fluvial and Glaciofluvial Activity in Chukhung Crater, Tempe Terra, Mars. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2717, https://doi.org/10.5194/egusphere-egu21-2717, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
We explore the origins of a complex assemblage of sinuous ridges in Chukhung crater (38.47°N, 72.42°W), Tempe Terra, Mars, and discuss the implications of the landsystem for post-Noachian fluvial and glaciofluvial activity in this location [1].
We produced a geomorphic map of Chukhung crater using a basemap of 6 m/pixel Context Camera (CTX) images and a 75 m/pixel High Resolution Stereo Camera digital elevation model (DEM). We used 25 cm/pixel High Resolution Imaging Science Experiment images, and a 24 cm/pixel DEM generated from CTX stereopair images [2] to aid classifications of sinuous ridges into four morpho-stratigraphic subtypes. We constrained an age envelope of ~2.1–3.6 Ga for Chukhung crater using modelled ages (from crater size-frequency analyses) of units above and below it in the regional stratigraphy. We derived a minimum model age of ~330 Ma for viscous flow features (putative debris-covered glaciers) in southern Chukhung crater.
Sinuous ridges in southern Chukhung crater emerge from moraine-like deposits associated with the debris-covered glaciers. Sinuous ridges in northern Chukhung crater extend from dendritic fluvial valley networks on the crater wall. The northern sinuous ridges are most likely to be inverted palaeochannels, which comprise subaerial river sediments exhumed as ridges by erosion of surrounding materials.
Both sinuous ridge subtypes in southern Chukhung crater have numerous esker-like properties. Eskers are ridges of glaciofluvial sediment deposited in meltwater tunnels within or beneath glacial ice. One of the ridge subtypes in southern Chukhung crater is best explained as eskers because these ridges ascend the sides of their host valleys and, in places, escape over them onto adjacent plains. Post-depositional processes can cause inverted paleochannels to cross local undulations in the contemporary topography [3] but the ascent and escape over larger, pre-existing topographic divides is (as yet) not adequately explained by these mechanisms. Eskers, in contrast, form under hydraulic pressure in ice-confined tunnels, and commonly ascend valley walls and cross topographic divides. The esker-like properties of the second sinuous ridge subtype in southern Chukhung crater can also be explained under the inverted palaeochannel hypothesis so the origins of these ridges remain more ambiguous.
Chukhung crater has undergone protracted and/or episodic modification by liquid water since its formation between the early Hesperian and early Amazonian. This falls after the Noachian period (>3.7 Ga), when most major fluvial activity on Mars occurred. Esker-forming wet-based glaciation in Chukhung crater might have occurred as recently as the mid Amazonian (>330 Ma), when climate conditions are thought to have been cold and hyper-arid. Rare occurrences of eskers associated with Amazonian-aged glaciers in Mars’ mid-latitudes are attributed to transient, localised geothermal heating within tectonic rift/graben settings [4]. The location of Chukhung crater between major branches of the large Tempe Fossae volcano-tectonic rift system is consistent with this hypothesis.
References: [1] Butcher et al. 2021, Icarus 357, 114131. [2] Mayer and Kite 2016, Lunar Planet. Sci. Conf. Abstract #1241. [3] Lefort et al. 2012, J. Geophys. Res. Planets 117, E03007. [4] Butcher et al. 2017, J. Geophys. Res. Planets 122, 2445–2468.
How to cite: Butcher, F. E. G., Balme, M. R., Conway, S. J., Gallagher, C., Arnold, N. S., Storrar, R. D., Lewis, S. R., Hagermann, A., and Davis, J. M.: Sinuous Ridges and the History of Fluvial and Glaciofluvial Activity in Chukhung Crater, Tempe Terra, Mars. , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2717, https://doi.org/10.5194/egusphere-egu21-2717, 2021.
EGU21-5946 | vPICO presentations | GM11.1
Viscous Flows Formed The Branched Ridges Of Antoniadi Crater, MarsNicolas Mangold, Livio Tornabene, Susan Conway, Anthony Guimpier, Axel Noblet, Peter Fawdon, Ernst Hauber, Antoine Pommerol, and Nicolas Thomas
Antoniadi basin is a 330 km diameter Noachian basin localized in the East of Arabia Terra that contains a network of ridges with a tree-like organization. Branched ridges, such as these can form by a variety of processes including the inversion of fluvial deposits, thus potentially highlighting aqueous processes of interest for understanding Mars’ climate evolution. Here, we test this hypothesis by analyzing in details data from Colour and Stereo Surface Imaging System (CaSSIS), High Resolution Imaging Science Experiment (HiRISE) and High Resolution Stereo Camera (HRSC).
Branched ridges are up to 10 km long and from 10 to 200 m wide without obvious organization in width. The branched ridges texture is rubbly with the occurrence of blocks up to ~1 m in size and a complete lack of layering. A HiRISE elevation model shows the local slope is of 0.2° toward South, and thus contrary to the apparent network organization (assuming tributary flows). There is no indication of exhumation of these ridges from layers below the current plains surface. Our observations are not consistent with the interpretation of digitate landforms such as inverted channels: (i) The rubbly texture lacking any layering at meter scale is distinct from inverted channels as observed elsewhere on Mars. (ii) Heads of presumed inverted channels display a lobate shape unlike river springs. (iii) There is no increase in width from small branches toward North as expected for channels with increasing discharge rates downstream. (iv) The slope toward South is contrary to the inferred flow direction to the North. The detailed analysis of these branched ridges shows many characteristics difficult to reconcile with inverted channels formed by fluvial channels flowing northward. Subglacial drainages are known to locally flow against topography, but they are rarely dendritic. Assuming that deposition occurred along the current slope, thus from North to South, the organization of the network requires a control by distributary channels rather than tributary ones. Distributary channels are possible for fluvial flows, but generally limited to braiding regimes or deltaic deposits, of which no further evidence is observed here. The lobate digitate shapes of the degree 1 branches are actually more in line with deposits of viscous flows, thus as terminal branches. Such an interpretation is consistent with lava or mudflows that formed along the current topography. The next step in this study will be to determine more precisely the rheology of these unusual flows.
Acknowledgments: French authors are supported by the CNES. The authors wish to thank the spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA’s PRODEX. The instrument hardware development was also supported by the Italian Space Agency (ASI) (agreement no. I/018/12/0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the Univ. of Arizona (Lunar and Planet. Lab.) and NASA are gratefully acknowledged.
How to cite: Mangold, N., Tornabene, L., Conway, S., Guimpier, A., Noblet, A., Fawdon, P., Hauber, E., Pommerol, A., and Thomas, N.: Viscous Flows Formed The Branched Ridges Of Antoniadi Crater, Mars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5946, https://doi.org/10.5194/egusphere-egu21-5946, 2021.
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Antoniadi basin is a 330 km diameter Noachian basin localized in the East of Arabia Terra that contains a network of ridges with a tree-like organization. Branched ridges, such as these can form by a variety of processes including the inversion of fluvial deposits, thus potentially highlighting aqueous processes of interest for understanding Mars’ climate evolution. Here, we test this hypothesis by analyzing in details data from Colour and Stereo Surface Imaging System (CaSSIS), High Resolution Imaging Science Experiment (HiRISE) and High Resolution Stereo Camera (HRSC).
Branched ridges are up to 10 km long and from 10 to 200 m wide without obvious organization in width. The branched ridges texture is rubbly with the occurrence of blocks up to ~1 m in size and a complete lack of layering. A HiRISE elevation model shows the local slope is of 0.2° toward South, and thus contrary to the apparent network organization (assuming tributary flows). There is no indication of exhumation of these ridges from layers below the current plains surface. Our observations are not consistent with the interpretation of digitate landforms such as inverted channels: (i) The rubbly texture lacking any layering at meter scale is distinct from inverted channels as observed elsewhere on Mars. (ii) Heads of presumed inverted channels display a lobate shape unlike river springs. (iii) There is no increase in width from small branches toward North as expected for channels with increasing discharge rates downstream. (iv) The slope toward South is contrary to the inferred flow direction to the North. The detailed analysis of these branched ridges shows many characteristics difficult to reconcile with inverted channels formed by fluvial channels flowing northward. Subglacial drainages are known to locally flow against topography, but they are rarely dendritic. Assuming that deposition occurred along the current slope, thus from North to South, the organization of the network requires a control by distributary channels rather than tributary ones. Distributary channels are possible for fluvial flows, but generally limited to braiding regimes or deltaic deposits, of which no further evidence is observed here. The lobate digitate shapes of the degree 1 branches are actually more in line with deposits of viscous flows, thus as terminal branches. Such an interpretation is consistent with lava or mudflows that formed along the current topography. The next step in this study will be to determine more precisely the rheology of these unusual flows.
Acknowledgments: French authors are supported by the CNES. The authors wish to thank the spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA’s PRODEX. The instrument hardware development was also supported by the Italian Space Agency (ASI) (agreement no. I/018/12/0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the Univ. of Arizona (Lunar and Planet. Lab.) and NASA are gratefully acknowledged.
How to cite: Mangold, N., Tornabene, L., Conway, S., Guimpier, A., Noblet, A., Fawdon, P., Hauber, E., Pommerol, A., and Thomas, N.: Viscous Flows Formed The Branched Ridges Of Antoniadi Crater, Mars, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5946, https://doi.org/10.5194/egusphere-egu21-5946, 2021.
EGU21-6021 | vPICO presentations | GM11.1
Do Martian slopes with Recurring Slope Lineae (RSL) have a distinct topographic signature?Aharon Adam, Itai Haviv, Dan G. Blumberg, Shimrit Maman, and Amit Mushkin
Recurring Slope Lineae (RSL) are dynamic, low-albedo, slope-parallel surface features on Mars that occur mainly on steep (>25°) slopes. RSL typically display seasonal dynamics as they appear during late Martian spring, progressively grow during summer, and subsequently fade as summer ends. RSL formation mechanisms remain under debate with proposed mechanisms involving either water/brines (‘wet theories’) vs. dry granular flows within a surficial dust layer (‘dry theories’). In an attempt to distinguish between plausible RSL mechanisms, this study compares the topographic and morphologic characteristics of hillslopes with and without RSL. We suggest that a distinct topographic signature for RSL hillslopes would argue against the ‘dry’ RSL mechanisms, as RSL dynamics within a thin dust layer are not expected to significantly impact the hillslope-scale topography. In contrast, the presence of fluids on RSL hillslopes could conceivably accelerate rock weathering rates, which in turn may impact the hillslope-scale topography. Our analyses are based on HiRISE, CTX and HRSC digital terrain models (DTMs) together with geomorphic mapping using high-resolution orbital images. We focus on inner crater hillslopes and compare the topographic characteristics of RSL vs. non-RSL slopes. In addition, in order to account for the potential influence of aspect-dependent solar irradiation on hillslope processes, we also applied our analysis on adjacent ‘control’ craters that are devoid of RSL activity. Preliminary results from Palikir (-41.6°/ 202.1°E) and Rauna (35.2°/ 328°E) craters reveal that the topographic slope distribution along crater walls with RSL activity is distinct from the slope distribution along crater walls which are devoid of RSL activity. Our results appear to support increased rock-weathering rates on crater walls that presently experience RSL activity.
How to cite: Adam, A., Haviv, I., Blumberg, D. G., Maman, S., and Mushkin, A.: Do Martian slopes with Recurring Slope Lineae (RSL) have a distinct topographic signature?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6021, https://doi.org/10.5194/egusphere-egu21-6021, 2021.
Recurring Slope Lineae (RSL) are dynamic, low-albedo, slope-parallel surface features on Mars that occur mainly on steep (>25°) slopes. RSL typically display seasonal dynamics as they appear during late Martian spring, progressively grow during summer, and subsequently fade as summer ends. RSL formation mechanisms remain under debate with proposed mechanisms involving either water/brines (‘wet theories’) vs. dry granular flows within a surficial dust layer (‘dry theories’). In an attempt to distinguish between plausible RSL mechanisms, this study compares the topographic and morphologic characteristics of hillslopes with and without RSL. We suggest that a distinct topographic signature for RSL hillslopes would argue against the ‘dry’ RSL mechanisms, as RSL dynamics within a thin dust layer are not expected to significantly impact the hillslope-scale topography. In contrast, the presence of fluids on RSL hillslopes could conceivably accelerate rock weathering rates, which in turn may impact the hillslope-scale topography. Our analyses are based on HiRISE, CTX and HRSC digital terrain models (DTMs) together with geomorphic mapping using high-resolution orbital images. We focus on inner crater hillslopes and compare the topographic characteristics of RSL vs. non-RSL slopes. In addition, in order to account for the potential influence of aspect-dependent solar irradiation on hillslope processes, we also applied our analysis on adjacent ‘control’ craters that are devoid of RSL activity. Preliminary results from Palikir (-41.6°/ 202.1°E) and Rauna (35.2°/ 328°E) craters reveal that the topographic slope distribution along crater walls with RSL activity is distinct from the slope distribution along crater walls which are devoid of RSL activity. Our results appear to support increased rock-weathering rates on crater walls that presently experience RSL activity.
How to cite: Adam, A., Haviv, I., Blumberg, D. G., Maman, S., and Mushkin, A.: Do Martian slopes with Recurring Slope Lineae (RSL) have a distinct topographic signature?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6021, https://doi.org/10.5194/egusphere-egu21-6021, 2021.
EGU21-12265 | vPICO presentations | GM11.1
Polygonal frost patterned ground as a Mars analogue in Northern Victoria Land, AntarcticaCynthia Sassenroth, Ernst Hauber, Carlo Baroni, Maria Cristina Salvatore, Jean-Pierre De Vera, and Nicole Schmitz
Polygonal patterned ground is ubiquitous in the martian mid-latitudes and in the polar regions of Earth. The latitude dependence of martian patterned ground and its morphological similarity to terrestrial patterned ground suggests that thermal contraction cracking may have been the leading formation mechanism for those polygons. Due to a lack of ground truthing on martian patterned ground, the role of liquid water in its formation and weather freeze-thaw processes lead to their origin is still debated. This study uses a quantitative approach, based on geomorphometrical and soil characteristics of patterned ground in continental Antarctica and glacial deposits with low inclination of Terra Nova Bay as terrestrial analogues, to understand polygon formation in martian hyper-arid conditions. We investigated polygons in ice-free parts of the mountain range of Helliwell Hills (~71°43S / 161°2E) in continental Antarctica and the Northern Foothills in the coastal Terra Nova Bay area (74°45S / 164°E).
Field observations were made during the austral summer on the GANOVEX XI and GANOVEX XIII expeditions in Dec-Jan 2015/2016 and Oct-Nov 2018, respectively. The polygonal troughs have been mapped and digitized in ArcGIS based on high resolution satellite images. For Helliwell Hills we used World View 2 images with a pixel size of 50 cm. For Terra Nova Bay, Quickbird satellite imagery has been used with a pixel size of 60 cm. Based on these datasets, parameters such as area, perimeter, length, and width have been measured, and size, circularity, orientation, and aspect ratio of each polygon were derived from these measurements. Additionally, we used a DTM derived from World View 2 stereo imagery (ground sampling distance: 8 m) to calculate the average slope, aspect, and solar irradiation of each polygon. The quantitative analysis shows that the geomorphometric characteristics of polygons in the Helliwell Hills differ significantly from those in Terra Nova Bay. Polygons in the Helliwell Hills are significantly smaller than in Terra Nova Bay and are organized as orthogonal, random-orthogonal and hexagonal polygon networks, while all polygons in Terra Nova Bay form hexagonal polygon-net geometries. The correlation of polygon-net geometries and the slope gradient shows that hexagonal polygon-net geometries dominate in flat terrains, while orthogonal geometries have developed on steeper slopes or in the immediate proximity of sharp terrain margins such as topographic slopes. The polygons in Helliwell Hills do not display significant local relief, but overall, the polygon centres are slightly higher than the bounding cracks (i.e. high-centered polygons). In Terra Nova Bay the appearance of high centred polygons and a deeper trough is even more developed and well distinguishable on satellite images.
During the fieldwork in Helliwell Hills, excavations were made in the center of polygons and across the bounding cracks. Typically, the uppermost ∼40 cm of regolith are dry and unconsolidated. Below that, there is commonly a sharp transition to ice-cemented material or very clear ice with no bubbles. The grain size analysis indicated no significant trend of sorting. We will present the results of our analysis and compare them with selected polygon sites on Mars.
How to cite: Sassenroth, C., Hauber, E., Baroni, C., Salvatore, M. C., De Vera, J.-P., and Schmitz, N.: Polygonal frost patterned ground as a Mars analogue in Northern Victoria Land, Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12265, https://doi.org/10.5194/egusphere-egu21-12265, 2021.
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Polygonal patterned ground is ubiquitous in the martian mid-latitudes and in the polar regions of Earth. The latitude dependence of martian patterned ground and its morphological similarity to terrestrial patterned ground suggests that thermal contraction cracking may have been the leading formation mechanism for those polygons. Due to a lack of ground truthing on martian patterned ground, the role of liquid water in its formation and weather freeze-thaw processes lead to their origin is still debated. This study uses a quantitative approach, based on geomorphometrical and soil characteristics of patterned ground in continental Antarctica and glacial deposits with low inclination of Terra Nova Bay as terrestrial analogues, to understand polygon formation in martian hyper-arid conditions. We investigated polygons in ice-free parts of the mountain range of Helliwell Hills (~71°43S / 161°2E) in continental Antarctica and the Northern Foothills in the coastal Terra Nova Bay area (74°45S / 164°E).
Field observations were made during the austral summer on the GANOVEX XI and GANOVEX XIII expeditions in Dec-Jan 2015/2016 and Oct-Nov 2018, respectively. The polygonal troughs have been mapped and digitized in ArcGIS based on high resolution satellite images. For Helliwell Hills we used World View 2 images with a pixel size of 50 cm. For Terra Nova Bay, Quickbird satellite imagery has been used with a pixel size of 60 cm. Based on these datasets, parameters such as area, perimeter, length, and width have been measured, and size, circularity, orientation, and aspect ratio of each polygon were derived from these measurements. Additionally, we used a DTM derived from World View 2 stereo imagery (ground sampling distance: 8 m) to calculate the average slope, aspect, and solar irradiation of each polygon. The quantitative analysis shows that the geomorphometric characteristics of polygons in the Helliwell Hills differ significantly from those in Terra Nova Bay. Polygons in the Helliwell Hills are significantly smaller than in Terra Nova Bay and are organized as orthogonal, random-orthogonal and hexagonal polygon networks, while all polygons in Terra Nova Bay form hexagonal polygon-net geometries. The correlation of polygon-net geometries and the slope gradient shows that hexagonal polygon-net geometries dominate in flat terrains, while orthogonal geometries have developed on steeper slopes or in the immediate proximity of sharp terrain margins such as topographic slopes. The polygons in Helliwell Hills do not display significant local relief, but overall, the polygon centres are slightly higher than the bounding cracks (i.e. high-centered polygons). In Terra Nova Bay the appearance of high centred polygons and a deeper trough is even more developed and well distinguishable on satellite images.
During the fieldwork in Helliwell Hills, excavations were made in the center of polygons and across the bounding cracks. Typically, the uppermost ∼40 cm of regolith are dry and unconsolidated. Below that, there is commonly a sharp transition to ice-cemented material or very clear ice with no bubbles. The grain size analysis indicated no significant trend of sorting. We will present the results of our analysis and compare them with selected polygon sites on Mars.
How to cite: Sassenroth, C., Hauber, E., Baroni, C., Salvatore, M. C., De Vera, J.-P., and Schmitz, N.: Polygonal frost patterned ground as a Mars analogue in Northern Victoria Land, Antarctica, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12265, https://doi.org/10.5194/egusphere-egu21-12265, 2021.
EGU21-8812 * | vPICO presentations | GM11.1 | Highlight
The seasonal evolution of ices on the gullied slopes of Sisyphi Cavi on Mars using CaSSIS and HiRISE orbital imagesSusan J. Conway, Kelly Pasquon, Stephen R. Lewis, Mathieu Vincendon, Marion Massé, Jan Raack, Axel Noblet, and Meven Philippe and the CaSSIS Team
Gully systems on Mars were first reported by Malin and Edgett (Science, 2000) and because of their similarity to gullies on Earth were attributed to the action of liquid water. They are generally kilometre-scale systems where tributary alcoves lead into channel(s), which terminate in digitate deposits and/or fans. They are found on almost all steep slopes polewards of 30°N/S and are oriented towards the pole in the interval 30-40°, then occur on all slope-orientations >40° (e.g. Conway et al. 2019). Their latitudinal distribution and trends in orientation are strong indicators of a climatic factor playing a pivotal role in their formation. Repeat orbital observations have revealed changes in up to 20% of monitored gully systems (Dundas et al. 2019). When the timing of the changes can be constrained, they occur at the end of the seasonal defrosting period when carbon dioxide ice is present at the surface rendering the temperatures too cold for liquid water to be involved (Dundas et al. 2015, 2019; Pasquon et al., 2016, 2019a,b; Raack et al. 2015, 2020). Some changes involve resolvable quantities of sediment, including motion of metre-scale boulders and erosion of new channels (Dundas et al. 2015; de Haas et al. 2019; Pasquon et al., 2019a).
Here, we exploit an exceptional time series to monitor the evolution of gullies and the seasonal frost deposits in Sisyphi Cavi (68-74°S, 345°-5°E). We use image data from HiRISE (High Resolution Imaging Science Experiment; 0.25-1 m/pixel), CaSSIS (Colour and Stereo Surface Imaging System; 4.5 m/pixel) and CTX (Context; 6 m/pixel). CaSSIS has four colour filters: BLU, PAN, RED and NIR (centred on 500, 675, 836 and 937 nm respectively); where the BLU filter is particularly useful for picking up surface frosts (Tornabene et al. 2019). We find that gullies and dunes are the last surfaces to defrost in the area. Independent of slope-orientation the alcoves of the gullies defrost first, followed by their channels then their fans. A surprising result considering that intuitively defrosting should progress from the equator-facing alcoves to the equator-facing fans, then from the pole-facing fans to the pole-facing alcoves. We infer that this is a consequence of a) fans and alcoves having contrasting thermal inertia and b) alcoves having slope-facets with a range of local orientations (with some proportion being equator-facing independent of overall orientation).
We observe dark spots, dark flows and dark fans at the metre-to-ten-metre-scale. These features occur when a continuous solid slab of translucent CO2-ice is penetrated and warmed by sunlight at its base. The sublimation drives gas build-up under the slab, ruptures it, entraining dust and then depositing the dust on the surface (e.g. Kieffer et al. 2006) to form spots, flows and/or fans, depending on the context. We find that the recent activity of gullies promotes the formation of dark spots/flows/fans and are investigating the inverse relationship.
Acknowledgement: CaSSIS is a project of the University of Bern, with instrument hardware development supported by INAF/Astronomical Observatory of Padova (ASI-INAF agreement n.2020-17-HH.0), and the Space Research Center (CBK) in Warsaw.
How to cite: Conway, S. J., Pasquon, K., Lewis, S. R., Vincendon, M., Massé, M., Raack, J., Noblet, A., and Philippe, M. and the CaSSIS Team: The seasonal evolution of ices on the gullied slopes of Sisyphi Cavi on Mars using CaSSIS and HiRISE orbital images, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8812, https://doi.org/10.5194/egusphere-egu21-8812, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Gully systems on Mars were first reported by Malin and Edgett (Science, 2000) and because of their similarity to gullies on Earth were attributed to the action of liquid water. They are generally kilometre-scale systems where tributary alcoves lead into channel(s), which terminate in digitate deposits and/or fans. They are found on almost all steep slopes polewards of 30°N/S and are oriented towards the pole in the interval 30-40°, then occur on all slope-orientations >40° (e.g. Conway et al. 2019). Their latitudinal distribution and trends in orientation are strong indicators of a climatic factor playing a pivotal role in their formation. Repeat orbital observations have revealed changes in up to 20% of monitored gully systems (Dundas et al. 2019). When the timing of the changes can be constrained, they occur at the end of the seasonal defrosting period when carbon dioxide ice is present at the surface rendering the temperatures too cold for liquid water to be involved (Dundas et al. 2015, 2019; Pasquon et al., 2016, 2019a,b; Raack et al. 2015, 2020). Some changes involve resolvable quantities of sediment, including motion of metre-scale boulders and erosion of new channels (Dundas et al. 2015; de Haas et al. 2019; Pasquon et al., 2019a).
Here, we exploit an exceptional time series to monitor the evolution of gullies and the seasonal frost deposits in Sisyphi Cavi (68-74°S, 345°-5°E). We use image data from HiRISE (High Resolution Imaging Science Experiment; 0.25-1 m/pixel), CaSSIS (Colour and Stereo Surface Imaging System; 4.5 m/pixel) and CTX (Context; 6 m/pixel). CaSSIS has four colour filters: BLU, PAN, RED and NIR (centred on 500, 675, 836 and 937 nm respectively); where the BLU filter is particularly useful for picking up surface frosts (Tornabene et al. 2019). We find that gullies and dunes are the last surfaces to defrost in the area. Independent of slope-orientation the alcoves of the gullies defrost first, followed by their channels then their fans. A surprising result considering that intuitively defrosting should progress from the equator-facing alcoves to the equator-facing fans, then from the pole-facing fans to the pole-facing alcoves. We infer that this is a consequence of a) fans and alcoves having contrasting thermal inertia and b) alcoves having slope-facets with a range of local orientations (with some proportion being equator-facing independent of overall orientation).
We observe dark spots, dark flows and dark fans at the metre-to-ten-metre-scale. These features occur when a continuous solid slab of translucent CO2-ice is penetrated and warmed by sunlight at its base. The sublimation drives gas build-up under the slab, ruptures it, entraining dust and then depositing the dust on the surface (e.g. Kieffer et al. 2006) to form spots, flows and/or fans, depending on the context. We find that the recent activity of gullies promotes the formation of dark spots/flows/fans and are investigating the inverse relationship.
Acknowledgement: CaSSIS is a project of the University of Bern, with instrument hardware development supported by INAF/Astronomical Observatory of Padova (ASI-INAF agreement n.2020-17-HH.0), and the Space Research Center (CBK) in Warsaw.
How to cite: Conway, S. J., Pasquon, K., Lewis, S. R., Vincendon, M., Massé, M., Raack, J., Noblet, A., and Philippe, M. and the CaSSIS Team: The seasonal evolution of ices on the gullied slopes of Sisyphi Cavi on Mars using CaSSIS and HiRISE orbital images, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8812, https://doi.org/10.5194/egusphere-egu21-8812, 2021.
EGU21-9482 | vPICO presentations | GM11.1 | Highlight
A numerical modelling toolbox for identifying the expression of dome-forming volcanism on exoplanetsClaire Harnett, Michael Heap, and Mark Thomas
The presence of volcanism is often anecdotally used to define a “living planet”. Since dome-building volcanism on Earth occurs primarily at plate boundaries, the identification of such domes could inform on exoplanetary development. Lava domes form when extruded magma is too viscous to flow from a vent, and their morphology on Earth varies from flat, pancake lobes to steep, blocky domes. Identification of lava domes on other terrestrial planets in our Solar System indicates that they likely also exist on rocky exoplanets. Here we show, using particle-based modelling, that the diversity of lava dome morphology in our Solar System is dwarfed by the diversity expected for exoplanets. Specifically, the height-to-diameter ratio of a dome decreases as a function of increasing gravity (i.e., planetary mass and radius). For example, lava domes on high-gravity super-Earths will be extremely wide and flat and a volcanic origin may not be immediately apparent. Creating a toolbox to help identify exoplanetary volcanism will allow us to make initial estimations as to the development and habitability of these alien worlds as images become available.
How to cite: Harnett, C., Heap, M., and Thomas, M.: A numerical modelling toolbox for identifying the expression of dome-forming volcanism on exoplanets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9482, https://doi.org/10.5194/egusphere-egu21-9482, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The presence of volcanism is often anecdotally used to define a “living planet”. Since dome-building volcanism on Earth occurs primarily at plate boundaries, the identification of such domes could inform on exoplanetary development. Lava domes form when extruded magma is too viscous to flow from a vent, and their morphology on Earth varies from flat, pancake lobes to steep, blocky domes. Identification of lava domes on other terrestrial planets in our Solar System indicates that they likely also exist on rocky exoplanets. Here we show, using particle-based modelling, that the diversity of lava dome morphology in our Solar System is dwarfed by the diversity expected for exoplanets. Specifically, the height-to-diameter ratio of a dome decreases as a function of increasing gravity (i.e., planetary mass and radius). For example, lava domes on high-gravity super-Earths will be extremely wide and flat and a volcanic origin may not be immediately apparent. Creating a toolbox to help identify exoplanetary volcanism will allow us to make initial estimations as to the development and habitability of these alien worlds as images become available.
How to cite: Harnett, C., Heap, M., and Thomas, M.: A numerical modelling toolbox for identifying the expression of dome-forming volcanism on exoplanets, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9482, https://doi.org/10.5194/egusphere-egu21-9482, 2021.
EGU21-11392 | vPICO presentations | GM11.1
Geomorphometric study of Martian scoria conesFanni Vörös and Balázs Székely
Compared to Earth, the surface erosion activity of Mars is low, so Martian landscapes can survive for long time, therefore Martian surface has been observed and analysed since the earliest times of Mars research. Because the planet’s geological and mass wasting history can be studied with remote sensing, observations may provide deeper insight into the early evolution of the planet (Golombek & Bridges, 2000). Lack of precipitation, vegetation and human influence have preserved landforms of Mars that have disappeared on Earth. Yet, local sampling and analysis of rocks are not possible, the evaluation of DTM data can deliver information. Presumably all the terrestrial geological processes also took place on Mars, therefore comparative observations provide a great opportunity to study landforms similar to terrestrial features. The most important difference between terrestrial and Martian surface processes is the formation of impact craters; but volcanic processes create specific volcanic edifices too. Of course, due to the different gravity forces and the lack of some surface effects, larger volcanic forms can also be found than on Earth.
We focus on the less researched smaller volcanic edifices. The morphometric studies on terrestrial scoria cones have revealed interesting details (Wood 1979; Brož et al., 2015): properties often can be related to their chronology. This pilot project intends to gather similar knowledge on smaller Martian volcanoes. With the development of morphometric technology, we may get an increasingly accurate picture of the surface and geology of Mars (Mars Trek). Besides the description of the physical appearance of the edifices, parameter extraction may lead to their classification or grouping. These studies may pave the way characterisation of Martian cones.
Previously we have examined the morphometry of several terrestrial scoria cone areas; a relatively simple structure were chosen to reduce the number of the geomorphometric parameters. In this project we apply the same simplification: the varying resolution of DTMs, the lack of proper geological maps limit the evaluation to the simple parametrisation. Furthermore, the sizes and characteristic slopes are different, but the results are promising. The automated parameter extraction seems to be suitable for processing multiple and large number of terrain data. This is a work in progress towards an extensive geomorphometric evaluation of Martian scoria cones as well.
F.V. was supported by the ÚNKP-20-3 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund.
Brož, P., Čadek, O., Hauber, E., & Rossi, A. P. (2015). Scoria cones on Mars: Detailed investigation of morphometry based on high-resolution digital elevation models. Journal of Geophysical Research: Planets, 120(9), 1512-1527.
Golombek, M. P., & Bridges, N. T. (2000). Erosion rates on Mars and implications for climate change: Constraints from the pathfinder landing site. Journal of Geophysical Research: Planets, 105(E1), 1 841- 1 853.
Mars trek. (n.d.). NASA Solar System Treks. https://trek.nasa.gov/mars/
Wood, C. A. (1979). Monogenetic volcanoes of the terrestrial planets. Proceedings of the Tenth Lunar and Planetary Science Conference, 2815-2840.
How to cite: Vörös, F. and Székely, B.: Geomorphometric study of Martian scoria cones, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11392, https://doi.org/10.5194/egusphere-egu21-11392, 2021.
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Compared to Earth, the surface erosion activity of Mars is low, so Martian landscapes can survive for long time, therefore Martian surface has been observed and analysed since the earliest times of Mars research. Because the planet’s geological and mass wasting history can be studied with remote sensing, observations may provide deeper insight into the early evolution of the planet (Golombek & Bridges, 2000). Lack of precipitation, vegetation and human influence have preserved landforms of Mars that have disappeared on Earth. Yet, local sampling and analysis of rocks are not possible, the evaluation of DTM data can deliver information. Presumably all the terrestrial geological processes also took place on Mars, therefore comparative observations provide a great opportunity to study landforms similar to terrestrial features. The most important difference between terrestrial and Martian surface processes is the formation of impact craters; but volcanic processes create specific volcanic edifices too. Of course, due to the different gravity forces and the lack of some surface effects, larger volcanic forms can also be found than on Earth.
We focus on the less researched smaller volcanic edifices. The morphometric studies on terrestrial scoria cones have revealed interesting details (Wood 1979; Brož et al., 2015): properties often can be related to their chronology. This pilot project intends to gather similar knowledge on smaller Martian volcanoes. With the development of morphometric technology, we may get an increasingly accurate picture of the surface and geology of Mars (Mars Trek). Besides the description of the physical appearance of the edifices, parameter extraction may lead to their classification or grouping. These studies may pave the way characterisation of Martian cones.
Previously we have examined the morphometry of several terrestrial scoria cone areas; a relatively simple structure were chosen to reduce the number of the geomorphometric parameters. In this project we apply the same simplification: the varying resolution of DTMs, the lack of proper geological maps limit the evaluation to the simple parametrisation. Furthermore, the sizes and characteristic slopes are different, but the results are promising. The automated parameter extraction seems to be suitable for processing multiple and large number of terrain data. This is a work in progress towards an extensive geomorphometric evaluation of Martian scoria cones as well.
F.V. was supported by the ÚNKP-20-3 New National Excellence Program of the Ministry for Innovation and Technology from the source of the National Research, Development and Innovation Fund.
Brož, P., Čadek, O., Hauber, E., & Rossi, A. P. (2015). Scoria cones on Mars: Detailed investigation of morphometry based on high-resolution digital elevation models. Journal of Geophysical Research: Planets, 120(9), 1512-1527.
Golombek, M. P., & Bridges, N. T. (2000). Erosion rates on Mars and implications for climate change: Constraints from the pathfinder landing site. Journal of Geophysical Research: Planets, 105(E1), 1 841- 1 853.
Mars trek. (n.d.). NASA Solar System Treks. https://trek.nasa.gov/mars/
Wood, C. A. (1979). Monogenetic volcanoes of the terrestrial planets. Proceedings of the Tenth Lunar and Planetary Science Conference, 2815-2840.
How to cite: Vörös, F. and Székely, B.: Geomorphometric study of Martian scoria cones, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11392, https://doi.org/10.5194/egusphere-egu21-11392, 2021.
EGU21-11520 | vPICO presentations | GM11.1
Tracing Martian volcanic activity using crater obliteration rateSylvain Breton, Lu Pan, Cathy Quantin-Nataf, Clément Brustel, and Jessica Flahaut
Impact craters are often used to date planetary surfaces, the density of crater increasing with the exposure age of the surface. However, some geologic event, such as lava flows, do not totally “reset” the crater clock. Indeed, larger craters, rather than being totally recovered by the lava flow will be only partially filled.
In that case, the crater size frequency distribution differs from cratering models. In order to better describe crater populations, additional parameters can be included. To this purpose we build crater size and depth frequency distributions that offers a snapshot of the current degradation state of the population.
We used cratering models to interpret crater size and depth frequency distributions in terms of crater infilling rates. Using both global crater database and more local high resolution crater maps, we estimated crater obliteration rates on various Martian volcanic provinces.
Our method proven efficient to track activity of the main Martian volcanic provinces. Resurfacing rates reach several thousands of m/Gy. Pic activity differs from provinces. Syrtis and Hesperia are the oldest with the highest and oldest observed rates around 3.7 Gy. The activity of those provinces quickly decreases reaching few hundreds of m/Gy around 3.4 Gy. During Hesperian, Tharsis is the most active surface of Mars with high resurfacing until 3.3 Gy. Finally, our result shows an increase of resurfacing, reaching few hundreds of m/Gy in Amazonis planitia from 2 Gy to present.
How to cite: Breton, S., Pan, L., Quantin-Nataf, C., Brustel, C., and Flahaut, J.: Tracing Martian volcanic activity using crater obliteration rate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11520, https://doi.org/10.5194/egusphere-egu21-11520, 2021.
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Impact craters are often used to date planetary surfaces, the density of crater increasing with the exposure age of the surface. However, some geologic event, such as lava flows, do not totally “reset” the crater clock. Indeed, larger craters, rather than being totally recovered by the lava flow will be only partially filled.
In that case, the crater size frequency distribution differs from cratering models. In order to better describe crater populations, additional parameters can be included. To this purpose we build crater size and depth frequency distributions that offers a snapshot of the current degradation state of the population.
We used cratering models to interpret crater size and depth frequency distributions in terms of crater infilling rates. Using both global crater database and more local high resolution crater maps, we estimated crater obliteration rates on various Martian volcanic provinces.
Our method proven efficient to track activity of the main Martian volcanic provinces. Resurfacing rates reach several thousands of m/Gy. Pic activity differs from provinces. Syrtis and Hesperia are the oldest with the highest and oldest observed rates around 3.7 Gy. The activity of those provinces quickly decreases reaching few hundreds of m/Gy around 3.4 Gy. During Hesperian, Tharsis is the most active surface of Mars with high resurfacing until 3.3 Gy. Finally, our result shows an increase of resurfacing, reaching few hundreds of m/Gy in Amazonis planitia from 2 Gy to present.
How to cite: Breton, S., Pan, L., Quantin-Nataf, C., Brustel, C., and Flahaut, J.: Tracing Martian volcanic activity using crater obliteration rate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11520, https://doi.org/10.5194/egusphere-egu21-11520, 2021.
EGU21-11780 | vPICO presentations | GM11.1
Rheology of the Andean domes as an analog for lunar silicic constructsJessica Flahaut, Osvaldo González-Maurel, Benigno Godoy, Melissa Martinot, and Martin Guitreau
The Andean volcanoes in the Atacama Desert offer a unique environment to perform remote sensing investigations as these bare surfaces are well exposed and well preserved due to their relatively young (quaternary) ages, and to hyper-arid environmental conditions. The Atacama Desert is, in fact, the driest non-polar desert on Earth, and for this reason, it has already been previously studied as a Moon and Mars analog environment (e.g., Flahaut et al., 2017). In the present study, we compare dacitic domes from the Altiplano-Puna Volcanic Complex (APVC) of the Atacama desert with volcanic edifices which have been previously reported as possible silicic domes on the Moon.
Five Atacama domes were studied from orbit, and three of them were sampled to obtain ground truth. These features formed by monogenetic eruptions and comprise high-K dacitic to rhyodacitic compositions with SiO2 contents ranging from 66 to 68 wt%. The dome dimensions measured from ASTER DEM indicate diameters between 1.5 to 6.2 km and heights between 250 and 700 m. Similar measurements were performed on various lunar domes with the LOLA DEM and show diameters ranging from a few km to 30 km, with slopes up to 9°. To the first order, dome eruptions can be considered as the extrusion of a Bingham fluid (the cooling magma) characterized by a yield strength τ and a plastic viscosity η (e.g., Hulme, 1974). Using the dome 3D dimensions as inputs into a rheological model, we estimate apparent viscosity to be in the order of 109-1011 Pa.s for both the Atacama domes and the lunar silicic domes.
In parallel, the non-Arrhenian Newton silicate melt viscosity is calculated using the Atacama dome bulk composition and the model of Giordano et al. (2008). Resulting liquid viscosities range from 4.5 to 8 x 106 Pa.s. The difference between the apparent and actual liquid viscosity was further used to calculate the packing fraction with the Einstein-Roscoe equation, which was found to be around 0.70-0.73 for all domes.
Dacitic domes in the APVC have aspect ratios, yield strengths and apparent viscosities similar to the Gruithuisen and Mairan lunar edifices, where elevated silica contents were previously reported (Glotch et al., 2011). We thus argue that the studied domes may be good analogs for these lunar domes, which are likely made of felsic rocks. However, when comparing viscosity estimates obtained from remote sensing data (apparent viscosity) and sample analyses (liquid viscosity) for the domes, we found that they differ by several orders of magnitude. Plausible explanations, which include a high amount of crystals in the mush (suggested by the high packing fraction values) will be discussed at the conference time.
References: Flahaut J. et al. (2017), Icarus, 282, 152-173; Giordano D. et al. (2008), EPSL 271,123–134; Glotch, T. D. et al. (2011), GRL, 38, L21204; Hulme G. (1974), Geophys. Journal International, 39 (2), 361–383.
How to cite: Flahaut, J., González-Maurel, O., Godoy, B., Martinot, M., and Guitreau, M.: Rheology of the Andean domes as an analog for lunar silicic constructs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11780, https://doi.org/10.5194/egusphere-egu21-11780, 2021.
The Andean volcanoes in the Atacama Desert offer a unique environment to perform remote sensing investigations as these bare surfaces are well exposed and well preserved due to their relatively young (quaternary) ages, and to hyper-arid environmental conditions. The Atacama Desert is, in fact, the driest non-polar desert on Earth, and for this reason, it has already been previously studied as a Moon and Mars analog environment (e.g., Flahaut et al., 2017). In the present study, we compare dacitic domes from the Altiplano-Puna Volcanic Complex (APVC) of the Atacama desert with volcanic edifices which have been previously reported as possible silicic domes on the Moon.
Five Atacama domes were studied from orbit, and three of them were sampled to obtain ground truth. These features formed by monogenetic eruptions and comprise high-K dacitic to rhyodacitic compositions with SiO2 contents ranging from 66 to 68 wt%. The dome dimensions measured from ASTER DEM indicate diameters between 1.5 to 6.2 km and heights between 250 and 700 m. Similar measurements were performed on various lunar domes with the LOLA DEM and show diameters ranging from a few km to 30 km, with slopes up to 9°. To the first order, dome eruptions can be considered as the extrusion of a Bingham fluid (the cooling magma) characterized by a yield strength τ and a plastic viscosity η (e.g., Hulme, 1974). Using the dome 3D dimensions as inputs into a rheological model, we estimate apparent viscosity to be in the order of 109-1011 Pa.s for both the Atacama domes and the lunar silicic domes.
In parallel, the non-Arrhenian Newton silicate melt viscosity is calculated using the Atacama dome bulk composition and the model of Giordano et al. (2008). Resulting liquid viscosities range from 4.5 to 8 x 106 Pa.s. The difference between the apparent and actual liquid viscosity was further used to calculate the packing fraction with the Einstein-Roscoe equation, which was found to be around 0.70-0.73 for all domes.
Dacitic domes in the APVC have aspect ratios, yield strengths and apparent viscosities similar to the Gruithuisen and Mairan lunar edifices, where elevated silica contents were previously reported (Glotch et al., 2011). We thus argue that the studied domes may be good analogs for these lunar domes, which are likely made of felsic rocks. However, when comparing viscosity estimates obtained from remote sensing data (apparent viscosity) and sample analyses (liquid viscosity) for the domes, we found that they differ by several orders of magnitude. Plausible explanations, which include a high amount of crystals in the mush (suggested by the high packing fraction values) will be discussed at the conference time.
References: Flahaut J. et al. (2017), Icarus, 282, 152-173; Giordano D. et al. (2008), EPSL 271,123–134; Glotch, T. D. et al. (2011), GRL, 38, L21204; Hulme G. (1974), Geophys. Journal International, 39 (2), 361–383.
How to cite: Flahaut, J., González-Maurel, O., Godoy, B., Martinot, M., and Guitreau, M.: Rheology of the Andean domes as an analog for lunar silicic constructs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11780, https://doi.org/10.5194/egusphere-egu21-11780, 2021.
EGU21-7609 | vPICO presentations | GM11.1
Impact crater versus bioherm on the Nullarbor Plain, AustraliaMatej Lipar, Mateja Ferk, and Andrej Šmuc
The Nullarbor Plain is ~200,000 km2 large planar karst surface in southern Australia, composed of middle Cenozoic shallow-water limestones of Eucla Group. The youngest formation, covering the top of the plain, is middle Miocene extremely fossiliferous sub-tropical Nullarbor Limestone. In the late Middle Miocene the area was uplifted and exposed to terrestrial denudation and erosion since. Although the plain is in general considered extremely flat, the present geomorphological features indicate a relatively complex geomorphology formed by a combination of tectonic deformation, fluvial and aeolian activity and karst denudation. Due to the absence of orogenesis and only minor influence of post-Miocene sediment deposition, the geomorphology of the Nullarbor preserved footprints of Earth processes through a long, middle Miocene-to-present, time span.
The presence of dry climate and consequent lack of vegetation also aided for numerous meteorite findings, but no visible impact deformations have been recorded. The latter, in combination with capability of the plain to inherit/imprint old geomorphological features, and accessibility of recently built 0.4 arc sec TanDEM-X-DEM by the German Aerospace Centre, motivated the search of a possible meteorite craters with spatial analysis of the plain. The analysis of DEM images revealed a single geomorphological feature with circular uplifted rim (diameter: 1200 m – 1300 m; height: 7 m in relation to outer elevation; width: 200 – 450 m), central uplift (diameter: 500 m; height: 10 m in relation to outer elevation), and a circular trough in between (2 – 3 m higher than outer elevation). Its morphology differs from other geomorphological features observable on the Nullarbor Plain, and represents a unique phenomenon, which cannot be explained as a part of tectonic, volcanic, fluvial, karst or aeolian processes.
This feature is therefore a candidate for a possible relict of a meteorite crater, which occurrence is supported by topographical characteristics including uniqueness of the shape compared to other features on the plain. On the other hand, geological characteristics of the exposed rock within the “crater” lack any of the general diagnostic evidence for impact events (e.g., shocked quartz, brecciation), but rather indicate presence of boundstones with frame-builders preserved in in-situ position and thus suggesting the preservation of a bioherm. The occurrences of bioherms, however, are seldom individual (unlike impact craters) and more likely occur in clusters. The question remaining for this conference discussion is whether dissolutional imprinting of an impact crater could denude any of the characteristic impact structures whilst preserving the shape, or are we looking at a single bioherm preserved as a primary marine depositional feature?
ACKNOWLEDGEMENT: We acknowledge the financial support of Slovenian Research Agency (P6-0101; I0-0031; N1-0162), the Australian Speleological Federation Karst Conservation Fund and TerraSAR-X / TanDEM-X (DEM_GEOL2288).
How to cite: Lipar, M., Ferk, M., and Šmuc, A.: Impact crater versus bioherm on the Nullarbor Plain, Australia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7609, https://doi.org/10.5194/egusphere-egu21-7609, 2021.
The Nullarbor Plain is ~200,000 km2 large planar karst surface in southern Australia, composed of middle Cenozoic shallow-water limestones of Eucla Group. The youngest formation, covering the top of the plain, is middle Miocene extremely fossiliferous sub-tropical Nullarbor Limestone. In the late Middle Miocene the area was uplifted and exposed to terrestrial denudation and erosion since. Although the plain is in general considered extremely flat, the present geomorphological features indicate a relatively complex geomorphology formed by a combination of tectonic deformation, fluvial and aeolian activity and karst denudation. Due to the absence of orogenesis and only minor influence of post-Miocene sediment deposition, the geomorphology of the Nullarbor preserved footprints of Earth processes through a long, middle Miocene-to-present, time span.
The presence of dry climate and consequent lack of vegetation also aided for numerous meteorite findings, but no visible impact deformations have been recorded. The latter, in combination with capability of the plain to inherit/imprint old geomorphological features, and accessibility of recently built 0.4 arc sec TanDEM-X-DEM by the German Aerospace Centre, motivated the search of a possible meteorite craters with spatial analysis of the plain. The analysis of DEM images revealed a single geomorphological feature with circular uplifted rim (diameter: 1200 m – 1300 m; height: 7 m in relation to outer elevation; width: 200 – 450 m), central uplift (diameter: 500 m; height: 10 m in relation to outer elevation), and a circular trough in between (2 – 3 m higher than outer elevation). Its morphology differs from other geomorphological features observable on the Nullarbor Plain, and represents a unique phenomenon, which cannot be explained as a part of tectonic, volcanic, fluvial, karst or aeolian processes.
This feature is therefore a candidate for a possible relict of a meteorite crater, which occurrence is supported by topographical characteristics including uniqueness of the shape compared to other features on the plain. On the other hand, geological characteristics of the exposed rock within the “crater” lack any of the general diagnostic evidence for impact events (e.g., shocked quartz, brecciation), but rather indicate presence of boundstones with frame-builders preserved in in-situ position and thus suggesting the preservation of a bioherm. The occurrences of bioherms, however, are seldom individual (unlike impact craters) and more likely occur in clusters. The question remaining for this conference discussion is whether dissolutional imprinting of an impact crater could denude any of the characteristic impact structures whilst preserving the shape, or are we looking at a single bioherm preserved as a primary marine depositional feature?
ACKNOWLEDGEMENT: We acknowledge the financial support of Slovenian Research Agency (P6-0101; I0-0031; N1-0162), the Australian Speleological Federation Karst Conservation Fund and TerraSAR-X / TanDEM-X (DEM_GEOL2288).
How to cite: Lipar, M., Ferk, M., and Šmuc, A.: Impact crater versus bioherm on the Nullarbor Plain, Australia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7609, https://doi.org/10.5194/egusphere-egu21-7609, 2021.
EGU21-11706 | vPICO presentations | GM11.1
The Marslabor of the University of Basel: Simulation of CLUPI operations in view of the ExoMars 2022 missionTomaso Bontognali, Yardena Meister, Brigitte Kuhn, Jean-Luc Josset, Beda Hofmann, and Nikolaus Kuhn
The Close-UP Imager (CLUPI) is one of the instruments of the Rosalind Franklin rover, which will explore Mars in the framework of the ESA/Roscosmos ExoMars mission. CLUPI will be mostly used for acquiring close up-images of geological samples, identifying materials and sedimentary structures that may record information about the hypothetical existence of past extraterrestrial life. Although the technical specifications of CLUPI are well known, it is not possible to readily translate such specifications in terms of feasibility to recognize “textures of interest” at a given distance under specific light conditions on Mars. Accurate predictions are important for taking informed decisions during the tactical planning of the rover. Here, we describe the results of some mission-preparation activities, during which a camera system analogue to CLUPI has been used to photograph rocks samples in an indoor facility (i.e., the Marslabor of the University of Basel) that has been built for simulating a Martian landscape. Under different light conditions, we performed a preliminary assessment of the minimal-working-distance required for interpreting rock textures and sedimentary structures that are potentially present on Mars, including textures that allows for differentiating sedimentary rocks from igneous rocks, grains that allows for classifying sedimentary rocks based on their granulometry, and stromatolitic laminations representing morphological biosignatures. The produced data represents a first step in identifying ideal CLUPI working-distances and illumination, and in preparing an image database that will be of help for optimizing rover operations and the scientific return of CLUPI during the ExoMars 2022 mission.
How to cite: Bontognali, T., Meister, Y., Kuhn, B., Josset, J.-L., Hofmann, B., and Kuhn, N.: The Marslabor of the University of Basel: Simulation of CLUPI operations in view of the ExoMars 2022 mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11706, https://doi.org/10.5194/egusphere-egu21-11706, 2021.
The Close-UP Imager (CLUPI) is one of the instruments of the Rosalind Franklin rover, which will explore Mars in the framework of the ESA/Roscosmos ExoMars mission. CLUPI will be mostly used for acquiring close up-images of geological samples, identifying materials and sedimentary structures that may record information about the hypothetical existence of past extraterrestrial life. Although the technical specifications of CLUPI are well known, it is not possible to readily translate such specifications in terms of feasibility to recognize “textures of interest” at a given distance under specific light conditions on Mars. Accurate predictions are important for taking informed decisions during the tactical planning of the rover. Here, we describe the results of some mission-preparation activities, during which a camera system analogue to CLUPI has been used to photograph rocks samples in an indoor facility (i.e., the Marslabor of the University of Basel) that has been built for simulating a Martian landscape. Under different light conditions, we performed a preliminary assessment of the minimal-working-distance required for interpreting rock textures and sedimentary structures that are potentially present on Mars, including textures that allows for differentiating sedimentary rocks from igneous rocks, grains that allows for classifying sedimentary rocks based on their granulometry, and stromatolitic laminations representing morphological biosignatures. The produced data represents a first step in identifying ideal CLUPI working-distances and illumination, and in preparing an image database that will be of help for optimizing rover operations and the scientific return of CLUPI during the ExoMars 2022 mission.
How to cite: Bontognali, T., Meister, Y., Kuhn, B., Josset, J.-L., Hofmann, B., and Kuhn, N.: The Marslabor of the University of Basel: Simulation of CLUPI operations in view of the ExoMars 2022 mission, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11706, https://doi.org/10.5194/egusphere-egu21-11706, 2021.
GM12.7 – Geoarchaeological records of human-landscape interaction: from a nature-dominated world to the Anthropocene
EGU21-9655 | vPICO presentations | GM12.7 | Highlight
Dynamics and sustainability of the Maya socio-ecosystem of the hinterland of Naachtun, between 1500 BCE and 1000 CE (Southern Maya Lowlands, Petén, Guatemala).Cyril Castanet, Philippe Nondédéo, Lydie Dussol, Marc Testé, Louise Purdue, Julien Hiquet, Eva Lemonnier, Aline Garnier, Antoine Dorison, Noémie Tomadini, Sandrine Grouard, Hemmamuthé Goudiaby, Carlos Morales-Aguilar, Nicole Limondin-Lozouet, Julien Cavero, Anne-Lise Develle-Vincent, Christine Hatté, Philippe Lanos, Fatima Mokadem, and György Sipos
In the Southern Maya Lowlands (SML), several scientific and technical obstacles hinder the knowledge of environmental and socio-environmental dynamics, that have occurred at the scale of the territories of the cities. This includes the research topic itself (nature-culture interface), the tropical forest (morphological studies and access to the field) and the morphological and sedimentary archives (taphonomy and discontinuity). The study of the socio-ecosystem of Naachtun (150-950 CE), a Maya city of the Classic period, is not exempt from these constraints. Recently, large-scale work in SML was conducted based on LiDAR analyses and fieldwork. They have profoundly renewed our knowledge of the complexity of landscape transformation and natural environments through the action of the ancient Maya (Canuto et al. 2018). They have provided new research perspectives which allow us to examine the following questions.
How did natural resource availability (water, soil and biological resources) change in the territory of the city, with respect to climate change and social demand? How did the ancient Maya adapt their resource management strategies to these changes? How important were socio-environmental risks to the resilience and sustainability of the socio-ecosystem? In order to answer these questions, a new systemic, interdisciplinary and multiscalar research program has been implemented. It includes geoarchaeology (alluvial and agrarian), archaeogeography (LiDAR analysis, spatial analysis), palaeoecology and bioarchaeology [archaeobotany (study of phytoliths, anthrocology, pedoanthracology) zooarchaeology (vertebrate and conchyological fauna remains)], spatial archaeology (agglomeration processes, power relays), palaeodemography and geochronology (14C, OSL). Current and pre-anthropic reference frames (hydrological, pedological and ecological) have also been established.
Our results reaveal the complexity of the Maya palimpsest territories produced during the ~ 1500 BCE - 1000 CE period (Preclassic and Classic periods). Hydrosedimentary flows have fluctuated in response to climate change and anthropogenic impacts, controlling the spatiotemporal dynamics of resources (water and soils). Lake levels and erosion have fluctuated according to pluricentennial-scale periods. All compartments of the hydrosystem and the sediment system were subject to transformations, to manage water and soils. A mosaic of agricultural and agroforestry strategies was developed throughout the micro-region (morphologies, practices, cropping systems, fuel economy). Intensive wetland systems and irrigated farming systems were established in poljes, sinkholes and valleys (raised fields and drained fields). In addition, in the hilly areas, agrarian systems based on terraced agriculture, rain-fed farming systems, slash-and-burn, arboriculture and horticulture systems were established. The Maya socio-ecosystem which emerged in this micro-region lasted for more than 2500 years. It experienced shits and continuities and its dynamics are framed around six main multi-secular periods. Its decline was part of the profound changes that took place in the territories of the SML cities between 750 and 1050 CE. The sustainability of this socio-ecosystem during the demographic peak of the Late and Terminal Classic (750-950 CE), before the abandonment of the epicenter of the city of Naachtun (~950 CE), is estimated and discussed in relation to the environmental carrying capacity, social demand, climate and its own resilience.
How to cite: Castanet, C., Nondédéo, P., Dussol, L., Testé, M., Purdue, L., Hiquet, J., Lemonnier, E., Garnier, A., Dorison, A., Tomadini, N., Grouard, S., Goudiaby, H., Morales-Aguilar, C., Limondin-Lozouet, N., Cavero, J., Develle-Vincent, A.-L., Hatté, C., Lanos, P., Mokadem, F., and Sipos, G.: Dynamics and sustainability of the Maya socio-ecosystem of the hinterland of Naachtun, between 1500 BCE and 1000 CE (Southern Maya Lowlands, Petén, Guatemala)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9655, https://doi.org/10.5194/egusphere-egu21-9655, 2021.
In the Southern Maya Lowlands (SML), several scientific and technical obstacles hinder the knowledge of environmental and socio-environmental dynamics, that have occurred at the scale of the territories of the cities. This includes the research topic itself (nature-culture interface), the tropical forest (morphological studies and access to the field) and the morphological and sedimentary archives (taphonomy and discontinuity). The study of the socio-ecosystem of Naachtun (150-950 CE), a Maya city of the Classic period, is not exempt from these constraints. Recently, large-scale work in SML was conducted based on LiDAR analyses and fieldwork. They have profoundly renewed our knowledge of the complexity of landscape transformation and natural environments through the action of the ancient Maya (Canuto et al. 2018). They have provided new research perspectives which allow us to examine the following questions.
How did natural resource availability (water, soil and biological resources) change in the territory of the city, with respect to climate change and social demand? How did the ancient Maya adapt their resource management strategies to these changes? How important were socio-environmental risks to the resilience and sustainability of the socio-ecosystem? In order to answer these questions, a new systemic, interdisciplinary and multiscalar research program has been implemented. It includes geoarchaeology (alluvial and agrarian), archaeogeography (LiDAR analysis, spatial analysis), palaeoecology and bioarchaeology [archaeobotany (study of phytoliths, anthrocology, pedoanthracology) zooarchaeology (vertebrate and conchyological fauna remains)], spatial archaeology (agglomeration processes, power relays), palaeodemography and geochronology (14C, OSL). Current and pre-anthropic reference frames (hydrological, pedological and ecological) have also been established.
Our results reaveal the complexity of the Maya palimpsest territories produced during the ~ 1500 BCE - 1000 CE period (Preclassic and Classic periods). Hydrosedimentary flows have fluctuated in response to climate change and anthropogenic impacts, controlling the spatiotemporal dynamics of resources (water and soils). Lake levels and erosion have fluctuated according to pluricentennial-scale periods. All compartments of the hydrosystem and the sediment system were subject to transformations, to manage water and soils. A mosaic of agricultural and agroforestry strategies was developed throughout the micro-region (morphologies, practices, cropping systems, fuel economy). Intensive wetland systems and irrigated farming systems were established in poljes, sinkholes and valleys (raised fields and drained fields). In addition, in the hilly areas, agrarian systems based on terraced agriculture, rain-fed farming systems, slash-and-burn, arboriculture and horticulture systems were established. The Maya socio-ecosystem which emerged in this micro-region lasted for more than 2500 years. It experienced shits and continuities and its dynamics are framed around six main multi-secular periods. Its decline was part of the profound changes that took place in the territories of the SML cities between 750 and 1050 CE. The sustainability of this socio-ecosystem during the demographic peak of the Late and Terminal Classic (750-950 CE), before the abandonment of the epicenter of the city of Naachtun (~950 CE), is estimated and discussed in relation to the environmental carrying capacity, social demand, climate and its own resilience.
How to cite: Castanet, C., Nondédéo, P., Dussol, L., Testé, M., Purdue, L., Hiquet, J., Lemonnier, E., Garnier, A., Dorison, A., Tomadini, N., Grouard, S., Goudiaby, H., Morales-Aguilar, C., Limondin-Lozouet, N., Cavero, J., Develle-Vincent, A.-L., Hatté, C., Lanos, P., Mokadem, F., and Sipos, G.: Dynamics and sustainability of the Maya socio-ecosystem of the hinterland of Naachtun, between 1500 BCE and 1000 CE (Southern Maya Lowlands, Petén, Guatemala)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9655, https://doi.org/10.5194/egusphere-egu21-9655, 2021.
EGU21-12988 | vPICO presentations | GM12.7
High resolution palynofacies analysis to understand Holocene Sudanian landscapes. First data from the Bao Bolon middle valley (Senegal).Emmanuel Weisskopf, Mathilde Stern, Loubna El Madouri, David Landry, Aline Garnier, and Aziz Ballouche
Key words: Palaeoenvironments, Holocene, Palynofacies, Microcharcoal, Fire signal, Anthropisation
The Bao Bolon valley, located in a Sudano-Sahelian context and overlapping both the Gambia and Saloum river basins, in western Senegal, is subject to strong seasonal rainfall contrasts. These particular conditions are usually badly appropriate to the good conservation of sedimentary archives. Moreover, this region is well known for his important archaeological heritage which includes the megalithic necropolis of Wanar classified on the UNESCO World Heritage list.
In addition to archaeological research, paleoenvironmental studies have been carried out at the Wanar site. Fluvial archives have been investigated and provide rich sedimentary records covering the entire Holocene period. Thus, the cultural and abiotic contexts of the middle Bao Bolon valley are now well documented (Laporte et al. 2017, Stern et al. 2019). Nevertheless, the biotic aspect, i.e. the landscapes and their evolution, still remains poorly documented in this region. Ongoing studies aim to better understand the Holocene palaeoenvironments and protohistoric agro-sylvo-pastoral systems by reconstituting biotic environments.
Due to the lack of pollen material, we focus on other, more abundant, organic elements recorded in the sedimentary archives. The study of organic matter has been first conducted through the palynofacies analysis. Among the different types of organic particles, we pay special attention to microcharcoals. Microcharcoals are often the longest lasting organic matter because carbonization protects the particles from degradation (except mechanical degradation). Their analysis focuses on the relative and absolute abundance, the morphology and the size of the particles. Microcharcoals are a relevant indicator of fire signals. Fires, whatever their origin, whether they are natural or anthropogenic, contribute to the changing and shaping of environmental landscapes. Therefore, high resolution palynofacies analyses contribute to a better understanding of the physical and anthropogenic transformations of the Holocene landscapes in the Bao Bolon middle valley.
The first results show a relative permanence of the signal of vegetation fires during the Holocene. The fluctuations of this burning activity are still under study. An important change seems to take place in the second half of the twentieth century. Further studies, in particular on phytoliths are under process. They will complete the interpretation of the landscapes dynamics during the Holocene.
How to cite: Weisskopf, E., Stern, M., El Madouri, L., Landry, D., Garnier, A., and Ballouche, A.: High resolution palynofacies analysis to understand Holocene Sudanian landscapes. First data from the Bao Bolon middle valley (Senegal)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12988, https://doi.org/10.5194/egusphere-egu21-12988, 2021.
Key words: Palaeoenvironments, Holocene, Palynofacies, Microcharcoal, Fire signal, Anthropisation
The Bao Bolon valley, located in a Sudano-Sahelian context and overlapping both the Gambia and Saloum river basins, in western Senegal, is subject to strong seasonal rainfall contrasts. These particular conditions are usually badly appropriate to the good conservation of sedimentary archives. Moreover, this region is well known for his important archaeological heritage which includes the megalithic necropolis of Wanar classified on the UNESCO World Heritage list.
In addition to archaeological research, paleoenvironmental studies have been carried out at the Wanar site. Fluvial archives have been investigated and provide rich sedimentary records covering the entire Holocene period. Thus, the cultural and abiotic contexts of the middle Bao Bolon valley are now well documented (Laporte et al. 2017, Stern et al. 2019). Nevertheless, the biotic aspect, i.e. the landscapes and their evolution, still remains poorly documented in this region. Ongoing studies aim to better understand the Holocene palaeoenvironments and protohistoric agro-sylvo-pastoral systems by reconstituting biotic environments.
Due to the lack of pollen material, we focus on other, more abundant, organic elements recorded in the sedimentary archives. The study of organic matter has been first conducted through the palynofacies analysis. Among the different types of organic particles, we pay special attention to microcharcoals. Microcharcoals are often the longest lasting organic matter because carbonization protects the particles from degradation (except mechanical degradation). Their analysis focuses on the relative and absolute abundance, the morphology and the size of the particles. Microcharcoals are a relevant indicator of fire signals. Fires, whatever their origin, whether they are natural or anthropogenic, contribute to the changing and shaping of environmental landscapes. Therefore, high resolution palynofacies analyses contribute to a better understanding of the physical and anthropogenic transformations of the Holocene landscapes in the Bao Bolon middle valley.
The first results show a relative permanence of the signal of vegetation fires during the Holocene. The fluctuations of this burning activity are still under study. An important change seems to take place in the second half of the twentieth century. Further studies, in particular on phytoliths are under process. They will complete the interpretation of the landscapes dynamics during the Holocene.
How to cite: Weisskopf, E., Stern, M., El Madouri, L., Landry, D., Garnier, A., and Ballouche, A.: High resolution palynofacies analysis to understand Holocene Sudanian landscapes. First data from the Bao Bolon middle valley (Senegal)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12988, https://doi.org/10.5194/egusphere-egu21-12988, 2021.
EGU21-470 | vPICO presentations | GM12.7
Bedrock, foothills and kinship: reconstructing the funerary landscape of Eastern SudanStefano Costanzo, Filippo Brandolini, Habab Idriss Ahmed, Andrea Zerboni, and Andrea Manzo
Monumental funerary landscapes are paramount representations of the relationship between environment and superstructural human behavior. Their formation sometimes requires millennia and they cover wide territories, often adding up to complex palimpsests of monuments belonging to different time periods. In this regard, the funerary landscape of the semi-arid foothill region of Kassala (Eastern Sudan) represents a solid example. Therein, a comprehensive geoarchaeological investigation conducted by means of field survey and remote sensing allowed the creation of a regional geomorphological base-map and a dataset of funerary monuments. The latter comprises several thousand raised stone-built tombs spanning from the early first millennium AD clusters of tumuli (belonging to the pan-African traditions) to regionally exclusive variants of medieval Islamic funerary architecture (qubbas). Funerary monuments are found as eye-catching scatters of hundreds of elements along the foothills of the many rocky outcrops dotting the pediplain of the western periphery of the Eritrean Highlands. In this study, the two categories of monuments were not considered as separate burialscapes, but rather examined as a unique, diachronic funerary landscape in its relationship with the geological and geomorphological settings and constraints. Point Pattern Analysis (PPA) was employed to determine the main environmental drivers of their locations on a regional scale, as well as to assess the existence of superstructural factors acting on their aggregation at the local scale. Our results strongly suggest the presence of a geological/environmental/societal synthesis underlying the choice of monuments’ location: at the regional scale, the pattern follows a precise set of rules residing in the concomitant presence of stable, gently rolling slopes and available metamorphic rock slabs; at the local scale, the clustering is heavily conditioned by superstructural dynamics that most likely reside in kinship and collective social memory of local Beja people. We suggest that the creation of the funerary landscape of Eastern Sudan is the result of a repeated and well coded social behavior of the Beja people, semi-nomadic cattle breeders known to have inhabited the region since “time immemorial”. Despite their mobile lifestyle and cultural contact with other North African and Arabic cultures, the monumental palimpsest portrays how the funerary habits of this millennia-old society persisted almost undisturbed, valuing location and kinship over external influences.
How to cite: Costanzo, S., Brandolini, F., Ahmed, H. I., Zerboni, A., and Manzo, A.: Bedrock, foothills and kinship: reconstructing the funerary landscape of Eastern Sudan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-470, https://doi.org/10.5194/egusphere-egu21-470, 2021.
Monumental funerary landscapes are paramount representations of the relationship between environment and superstructural human behavior. Their formation sometimes requires millennia and they cover wide territories, often adding up to complex palimpsests of monuments belonging to different time periods. In this regard, the funerary landscape of the semi-arid foothill region of Kassala (Eastern Sudan) represents a solid example. Therein, a comprehensive geoarchaeological investigation conducted by means of field survey and remote sensing allowed the creation of a regional geomorphological base-map and a dataset of funerary monuments. The latter comprises several thousand raised stone-built tombs spanning from the early first millennium AD clusters of tumuli (belonging to the pan-African traditions) to regionally exclusive variants of medieval Islamic funerary architecture (qubbas). Funerary monuments are found as eye-catching scatters of hundreds of elements along the foothills of the many rocky outcrops dotting the pediplain of the western periphery of the Eritrean Highlands. In this study, the two categories of monuments were not considered as separate burialscapes, but rather examined as a unique, diachronic funerary landscape in its relationship with the geological and geomorphological settings and constraints. Point Pattern Analysis (PPA) was employed to determine the main environmental drivers of their locations on a regional scale, as well as to assess the existence of superstructural factors acting on their aggregation at the local scale. Our results strongly suggest the presence of a geological/environmental/societal synthesis underlying the choice of monuments’ location: at the regional scale, the pattern follows a precise set of rules residing in the concomitant presence of stable, gently rolling slopes and available metamorphic rock slabs; at the local scale, the clustering is heavily conditioned by superstructural dynamics that most likely reside in kinship and collective social memory of local Beja people. We suggest that the creation of the funerary landscape of Eastern Sudan is the result of a repeated and well coded social behavior of the Beja people, semi-nomadic cattle breeders known to have inhabited the region since “time immemorial”. Despite their mobile lifestyle and cultural contact with other North African and Arabic cultures, the monumental palimpsest portrays how the funerary habits of this millennia-old society persisted almost undisturbed, valuing location and kinship over external influences.
How to cite: Costanzo, S., Brandolini, F., Ahmed, H. I., Zerboni, A., and Manzo, A.: Bedrock, foothills and kinship: reconstructing the funerary landscape of Eastern Sudan, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-470, https://doi.org/10.5194/egusphere-egu21-470, 2021.
EGU21-15578 | vPICO presentations | GM12.7
Middle Bronze Age land use practices in the north-western Alpine foreland – A multi-proxy study of colluvial deposits, archaeological features and peat bogsSascha Scherer, Benjamin Höpfer, Katleen Deckers, Elske Fischer, Markus Fuchs, Ellen Kandeler, Eva Lehndorff, Johanna Lomax, Sven Marhan, Elena Marinova, Jutta Lechterbeck, Julia Meister, Christian Poll, Humay Rahimova, Manfred Rösch, Kristen Wroth, Julia Zastrow, Thomas Knopf, Thomas Scholten, and Peter Kühn
We present a multi-proxy approach to reconstruct Middle Bronze Age (MBA, 1600-1250 BCE) land use practices in the north-western Alpine foreland (SW Germany, Hegau). We combined biogeochemical proxies from multi-layered colluvial deposits and archaeobotanical and archaeozoological data within and in the surrounding of the archaeologically well-documented settlement site of Anselfingen. Offsite pollen data from two peat bogs were used to place the onsite and near-site vegetation and land use data to a regional context.
Phases of colluvial deposition were reconstructed by optically stimulated luminescence (OSL) and radiocarbon (AMS 14C) dating. The first phase of major colluviation could be correlated with MBA land use followed by phases of colluvial deposition during the Iron Age, the Medieval period, and modern times. Charcoal spectra from colluvial deposits and archaeological structures indicate MBA forest management favoring Quercus in the surrounding area north of the settlement. The analysis of faecal biomarker (5ß-stanols up to 40 %) and excavated pig bones (up to 14 %) suggest the presence of a forest pasture mainly used for pig farming. In the surrounding area south of the settlement, an arable field with a buried MBA plough horizon (2Apb) could be verified by soil micromorphological features such as very dusty clay coatings and a banded microstructure and by high concentrations of grass phytoliths from leaves and stems. Agricultural practices (e.g. ploughing) focused on five staple cereal crops (Hordeum distichon/vulgare, Triticum dicoccum, Triticum monococcum, Triticum spelta, Triticum aestivum/turgidum) as indicated by the onsite archaeobotanical records. Stilted pantries, reconstructed from MBA post-holes, were interpreted as storage facilities, while excavated heat stones are likely to indicate post-harvest processing of cereal crops and other agrarian products. Higher levels of urease activity compared to microbial biomass carbon (up to 2.1 µg N µg Cmic-1), and input of herbivorous animal faeces indicate livestock husbandry on fallow land or manuring practices. The suites of polycyclic aromatic hydrocarbons (PAHs) and their spatial distribution indicate the use of fire for various purposes, e.g. for landscape opening and maintenance, for domestic burning and for technical applications. The offsite pollen data support the onsite and near-site vegetation change. During the MBA, fire played a major role in shaping the landscape (peak of micro-charcoal during the MBA in the offsite pollen records) and anthropogenic activities promoted oak dominated forest vegetation at the expense of natural beech forests. This approves a broad regional human influence in the north-western Alpine foreland during the MBA.
Our data allow in-depth insights into the MBA subsistence economy on a local and regional scale, which was not limited to settlements at lakeshore sites. The MBA in the north-western Alpine foreland was a period of establishing settlements with sophisticated land management and land use practices also at low and mid altitude inland sites. We could further show that colluvial deposits are promising archives for the reconstruction of past land use practices.
How to cite: Scherer, S., Höpfer, B., Deckers, K., Fischer, E., Fuchs, M., Kandeler, E., Lehndorff, E., Lomax, J., Marhan, S., Marinova, E., Lechterbeck, J., Meister, J., Poll, C., Rahimova, H., Rösch, M., Wroth, K., Zastrow, J., Knopf, T., Scholten, T., and Kühn, P.: Middle Bronze Age land use practices in the north-western Alpine foreland – A multi-proxy study of colluvial deposits, archaeological features and peat bogs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15578, https://doi.org/10.5194/egusphere-egu21-15578, 2021.
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We present a multi-proxy approach to reconstruct Middle Bronze Age (MBA, 1600-1250 BCE) land use practices in the north-western Alpine foreland (SW Germany, Hegau). We combined biogeochemical proxies from multi-layered colluvial deposits and archaeobotanical and archaeozoological data within and in the surrounding of the archaeologically well-documented settlement site of Anselfingen. Offsite pollen data from two peat bogs were used to place the onsite and near-site vegetation and land use data to a regional context.
Phases of colluvial deposition were reconstructed by optically stimulated luminescence (OSL) and radiocarbon (AMS 14C) dating. The first phase of major colluviation could be correlated with MBA land use followed by phases of colluvial deposition during the Iron Age, the Medieval period, and modern times. Charcoal spectra from colluvial deposits and archaeological structures indicate MBA forest management favoring Quercus in the surrounding area north of the settlement. The analysis of faecal biomarker (5ß-stanols up to 40 %) and excavated pig bones (up to 14 %) suggest the presence of a forest pasture mainly used for pig farming. In the surrounding area south of the settlement, an arable field with a buried MBA plough horizon (2Apb) could be verified by soil micromorphological features such as very dusty clay coatings and a banded microstructure and by high concentrations of grass phytoliths from leaves and stems. Agricultural practices (e.g. ploughing) focused on five staple cereal crops (Hordeum distichon/vulgare, Triticum dicoccum, Triticum monococcum, Triticum spelta, Triticum aestivum/turgidum) as indicated by the onsite archaeobotanical records. Stilted pantries, reconstructed from MBA post-holes, were interpreted as storage facilities, while excavated heat stones are likely to indicate post-harvest processing of cereal crops and other agrarian products. Higher levels of urease activity compared to microbial biomass carbon (up to 2.1 µg N µg Cmic-1), and input of herbivorous animal faeces indicate livestock husbandry on fallow land or manuring practices. The suites of polycyclic aromatic hydrocarbons (PAHs) and their spatial distribution indicate the use of fire for various purposes, e.g. for landscape opening and maintenance, for domestic burning and for technical applications. The offsite pollen data support the onsite and near-site vegetation change. During the MBA, fire played a major role in shaping the landscape (peak of micro-charcoal during the MBA in the offsite pollen records) and anthropogenic activities promoted oak dominated forest vegetation at the expense of natural beech forests. This approves a broad regional human influence in the north-western Alpine foreland during the MBA.
Our data allow in-depth insights into the MBA subsistence economy on a local and regional scale, which was not limited to settlements at lakeshore sites. The MBA in the north-western Alpine foreland was a period of establishing settlements with sophisticated land management and land use practices also at low and mid altitude inland sites. We could further show that colluvial deposits are promising archives for the reconstruction of past land use practices.
How to cite: Scherer, S., Höpfer, B., Deckers, K., Fischer, E., Fuchs, M., Kandeler, E., Lehndorff, E., Lomax, J., Marhan, S., Marinova, E., Lechterbeck, J., Meister, J., Poll, C., Rahimova, H., Rösch, M., Wroth, K., Zastrow, J., Knopf, T., Scholten, T., and Kühn, P.: Middle Bronze Age land use practices in the north-western Alpine foreland – A multi-proxy study of colluvial deposits, archaeological features and peat bogs, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15578, https://doi.org/10.5194/egusphere-egu21-15578, 2021.
EGU21-9499 | vPICO presentations | GM12.7
A geoachaeological view on the Roman economy of Baetica – The case study Munigua (Seville, SW-Spain).André Kirchner, Nico Herrmann, Paul Matras, Iris Müller, and Julia Meister
The economy of Roman cities in Baetica, was largely diversified and depending on the city for example specialized in olive oil, halieutic or metallurgical production. The economy of the Hispano-Roman city Munigua (municipium Flavium Muniguense) was particularly based on mining and in the 1st and 2nd centuries CE Munigua was the largest producer of copper and iron in the Sierra Morena. This contribution focuses on the evaluation of soil potential for practicing agriculture and evidences for prehistoric and historic land use in the vicinity of Munigua. It aims to provide new information to the food supply strategy of Munigua and furthermore a geoarchaeological few on the diversification debate of the urban economy in the conventus Hispalensis. Applying a pedo-geomorphic approach the present study i) shows that the landscape around Munigua has the potential for an agricultural use in larger areas and would have certainly allowed a production of agricultural goods in Roman times. Additionally, the study ii) provides clear evidence for prehistoric and historic land use in region documented by multi-layered colluvial deposits and a preserved Roman hortic soil. Hence, the results pointing to a local cultivation of agricultural products as an active contribution to the food supply of Munigua. Moreover, the study provides geoarchaeological evidences supporting the concept of an economic diversification of Roman cities in Baetica province and Hispania.
How to cite: Kirchner, A., Herrmann, N., Matras, P., Müller, I., and Meister, J.: A geoachaeological view on the Roman economy of Baetica – The case study Munigua (Seville, SW-Spain)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9499, https://doi.org/10.5194/egusphere-egu21-9499, 2021.
The economy of Roman cities in Baetica, was largely diversified and depending on the city for example specialized in olive oil, halieutic or metallurgical production. The economy of the Hispano-Roman city Munigua (municipium Flavium Muniguense) was particularly based on mining and in the 1st and 2nd centuries CE Munigua was the largest producer of copper and iron in the Sierra Morena. This contribution focuses on the evaluation of soil potential for practicing agriculture and evidences for prehistoric and historic land use in the vicinity of Munigua. It aims to provide new information to the food supply strategy of Munigua and furthermore a geoarchaeological few on the diversification debate of the urban economy in the conventus Hispalensis. Applying a pedo-geomorphic approach the present study i) shows that the landscape around Munigua has the potential for an agricultural use in larger areas and would have certainly allowed a production of agricultural goods in Roman times. Additionally, the study ii) provides clear evidence for prehistoric and historic land use in region documented by multi-layered colluvial deposits and a preserved Roman hortic soil. Hence, the results pointing to a local cultivation of agricultural products as an active contribution to the food supply of Munigua. Moreover, the study provides geoarchaeological evidences supporting the concept of an economic diversification of Roman cities in Baetica province and Hispania.
How to cite: Kirchner, A., Herrmann, N., Matras, P., Müller, I., and Meister, J.: A geoachaeological view on the Roman economy of Baetica – The case study Munigua (Seville, SW-Spain)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9499, https://doi.org/10.5194/egusphere-egu21-9499, 2021.
EGU21-4816 | vPICO presentations | GM12.7
Granite Characterisation and Chronology of the Archaeological Site of Touças (North of Portugal)David Freire-Lista, Jorge Sanjurjo-Sánchez, and Gerardo Vidal Gonçalves
Stones have been essential to protect humans from weather conditions since the beginning of humanity in escarpments, caves and other dwellings. In addition, they have been used as prehistoric tools, amulets, support for rock art and inscriptions of events or laws. They have also been used for the construction of houses, warehouses, pavements, dikes, funerary monuments and sanctuaries. Foundation stones are laid at the moment when construction of the building or structure that they support starts. The dating of this moment provides useful information about the past history of human activities.
The archaeological site of Touças is located 500 meters to the northeast of Garganta village, in São Martinho de Anta, municipality of Sabrosa (North of Portugal). It consists of about 70 standing stones of granite, several granite sarcophagi, a twin carved grave in the outcropping granite, historical quarries, a well-preserved landmark of Malta military order. In addition, a historical document indicates the previous existence of a chapel in this site.
Fieldwork was carried out to determine the type of building stones used at the archaeological site. Building granite has been identified and sampled for an in-depth analytical study. Two thin sections were prepared and characterised under a Leica DM-4500-P polarisation microscope equipped with a Leica DFC290-HD digital camera and LAS-4.9 software. Eight cubic samples with dimensions of 5×5×5±0.5 cm were tested for the petrophysical characterisation of the granite (effective porosity, water absorption and bulk density) using the Natural Stone Test Method described in European standard UNE-EN 1936. Ultrasonic pulse velocity of the granite cubes was taken with a CNS Electronics PUNDIT equipment following European standard UNE-EN 14579.
Optically stimulated luminescence (OSL) was applied to the granite foundation stones of the standing stones, sarcophagi, and walls to determine their chronology. This was done by measuring the OSL signal of the surface layer of buried granite stones. The sampling was performed at night, under red light. In the lab, slides of 5 mm layer from each stone surface was removed by sawing with a diamond-impregnated wheel. The samples were crushed in a vice and crystals with a diameter in the range of 90-250 mm were extracted by sieving. All measurements were taken with an automated Risø TL/OSL-DA15 reader and a Lexsyg Research device.
The main building granite of the archaeological site is a coarse-crystal-size granite with elongated pseudo-oriented feldspars. This building granite is the same as the outcropping granite, where there is a historical quarry.
OSL dating can be applied to obtain the absolute age from the burial of stones containing quartz. The archaeological excavations carried out in 2020 revealed that the standing stones may predate the use of the site as a medieval necropolis. The foundations of a wall that could belong to the Hermes chapel have also been found.
This archaeological site presents extremely relevant evidence for the understanding of human occupation in Trás-os-Montes e Alto Douro territory.
Acknowledgements: Fundação para a Ciência e a Tecnologia (FCT) of Portugal. Stimulus of Scientific Employment, Individual Support 2017. CEECIND/03568/2017.
How to cite: Freire-Lista, D., Sanjurjo-Sánchez, J., and Vidal Gonçalves, G.: Granite Characterisation and Chronology of the Archaeological Site of Touças (North of Portugal), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4816, https://doi.org/10.5194/egusphere-egu21-4816, 2021.
Stones have been essential to protect humans from weather conditions since the beginning of humanity in escarpments, caves and other dwellings. In addition, they have been used as prehistoric tools, amulets, support for rock art and inscriptions of events or laws. They have also been used for the construction of houses, warehouses, pavements, dikes, funerary monuments and sanctuaries. Foundation stones are laid at the moment when construction of the building or structure that they support starts. The dating of this moment provides useful information about the past history of human activities.
The archaeological site of Touças is located 500 meters to the northeast of Garganta village, in São Martinho de Anta, municipality of Sabrosa (North of Portugal). It consists of about 70 standing stones of granite, several granite sarcophagi, a twin carved grave in the outcropping granite, historical quarries, a well-preserved landmark of Malta military order. In addition, a historical document indicates the previous existence of a chapel in this site.
Fieldwork was carried out to determine the type of building stones used at the archaeological site. Building granite has been identified and sampled for an in-depth analytical study. Two thin sections were prepared and characterised under a Leica DM-4500-P polarisation microscope equipped with a Leica DFC290-HD digital camera and LAS-4.9 software. Eight cubic samples with dimensions of 5×5×5±0.5 cm were tested for the petrophysical characterisation of the granite (effective porosity, water absorption and bulk density) using the Natural Stone Test Method described in European standard UNE-EN 1936. Ultrasonic pulse velocity of the granite cubes was taken with a CNS Electronics PUNDIT equipment following European standard UNE-EN 14579.
Optically stimulated luminescence (OSL) was applied to the granite foundation stones of the standing stones, sarcophagi, and walls to determine their chronology. This was done by measuring the OSL signal of the surface layer of buried granite stones. The sampling was performed at night, under red light. In the lab, slides of 5 mm layer from each stone surface was removed by sawing with a diamond-impregnated wheel. The samples were crushed in a vice and crystals with a diameter in the range of 90-250 mm were extracted by sieving. All measurements were taken with an automated Risø TL/OSL-DA15 reader and a Lexsyg Research device.
The main building granite of the archaeological site is a coarse-crystal-size granite with elongated pseudo-oriented feldspars. This building granite is the same as the outcropping granite, where there is a historical quarry.
OSL dating can be applied to obtain the absolute age from the burial of stones containing quartz. The archaeological excavations carried out in 2020 revealed that the standing stones may predate the use of the site as a medieval necropolis. The foundations of a wall that could belong to the Hermes chapel have also been found.
This archaeological site presents extremely relevant evidence for the understanding of human occupation in Trás-os-Montes e Alto Douro territory.
Acknowledgements: Fundação para a Ciência e a Tecnologia (FCT) of Portugal. Stimulus of Scientific Employment, Individual Support 2017. CEECIND/03568/2017.
How to cite: Freire-Lista, D., Sanjurjo-Sánchez, J., and Vidal Gonçalves, G.: Granite Characterisation and Chronology of the Archaeological Site of Touças (North of Portugal), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4816, https://doi.org/10.5194/egusphere-egu21-4816, 2021.
EGU21-16222 | vPICO presentations | GM12.7
The enigma on the date of the 79 AD Vesuvius eruption: lesson from grape archaeobotanical remainsAlessia D'Auria, Veronica De Micco, and Gaetano Di Pasquale
EGU21-10556 | vPICO presentations | GM12.7
Analysis between ancient human settlements and volcanic landscapes using earth observation and archaeological dataGeorge Alexandrakis, Federico Nomi, Claudia Speciale, Sandro De Vita, and Mauro Antonio Di Vito
Geological and environmental conditions that influence local topography also affect indirectly the location of human settlement dynamics. Understanding those relationships plays an important role in archaeological research related to the evolution of settlement dynamics. In the lower Tyrrhenian Islands, an important parameter is also the volcanic landscape evolution. This work aims to study the patterns of Neolithic, Cooper and Bronze Age settlements, based on known archaeological sites at the Low Tyrrhenian Islands, and to generate hypotheses about the relations of settlement patterns with the volcanic landscape. To that end, a Web-GIS database was created, which was fed with topographic, geological, geomorphological data and Earth Observation data. Geomorphological analysis, derived from digital elevation models, and earth observation products such as the SENTINEL missions, can provide useful estimations into the processes shaping landscapes and insight into the location and evolution of settlements. The analysis includes a series of different data correlation, from geomorphologic to socioeconomic, integrated by an indicator analysis. A series of thematic maps were developed to interpret why areas were selected to host settlements. Through the use of the database that was developed during the project, a set of indexes have been applied. Those included exposure and vulnerability indices for the inland and coastal areas, but also location and defensibility indices for the archaeological sites. Moreover, baseline maps for future risk estimations through a Multi-Criteria Decision Analysis System (MCDA), have been produced. The Volcanic Islands of the lower Tyrrhenian coast have a volcanic origin and were influenced, and partly still are, by explosive and effusive eruptions of various energy and types, by more or less intense deformational events, often connected with the dynamics of the volcano, and quiescent periods of varying duration. The areas under investigation present different characteristics in their geomorphological but also their societal evolution. Geomorphological data further analyzed in a ternary diagram that indicated the relative influence of each of the parameters in each area. From the diagram, it can be seen that the locations of human activities are strongly affected by past and recent volcanic activity.
Acknowledgement: This work is part of the Brains2Islands “INDAGINE MULTIDISCIPLINARE NEI CONTESTI INSULARI BASSO TIRRENICI” project Funded by FONDAZIONE CON IL SUD project number 2015-0296
How to cite: Alexandrakis, G., Nomi, F., Speciale, C., De Vita, S., and Di Vito, M. A.: Analysis between ancient human settlements and volcanic landscapes using earth observation and archaeological data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10556, https://doi.org/10.5194/egusphere-egu21-10556, 2021.
Geological and environmental conditions that influence local topography also affect indirectly the location of human settlement dynamics. Understanding those relationships plays an important role in archaeological research related to the evolution of settlement dynamics. In the lower Tyrrhenian Islands, an important parameter is also the volcanic landscape evolution. This work aims to study the patterns of Neolithic, Cooper and Bronze Age settlements, based on known archaeological sites at the Low Tyrrhenian Islands, and to generate hypotheses about the relations of settlement patterns with the volcanic landscape. To that end, a Web-GIS database was created, which was fed with topographic, geological, geomorphological data and Earth Observation data. Geomorphological analysis, derived from digital elevation models, and earth observation products such as the SENTINEL missions, can provide useful estimations into the processes shaping landscapes and insight into the location and evolution of settlements. The analysis includes a series of different data correlation, from geomorphologic to socioeconomic, integrated by an indicator analysis. A series of thematic maps were developed to interpret why areas were selected to host settlements. Through the use of the database that was developed during the project, a set of indexes have been applied. Those included exposure and vulnerability indices for the inland and coastal areas, but also location and defensibility indices for the archaeological sites. Moreover, baseline maps for future risk estimations through a Multi-Criteria Decision Analysis System (MCDA), have been produced. The Volcanic Islands of the lower Tyrrhenian coast have a volcanic origin and were influenced, and partly still are, by explosive and effusive eruptions of various energy and types, by more or less intense deformational events, often connected with the dynamics of the volcano, and quiescent periods of varying duration. The areas under investigation present different characteristics in their geomorphological but also their societal evolution. Geomorphological data further analyzed in a ternary diagram that indicated the relative influence of each of the parameters in each area. From the diagram, it can be seen that the locations of human activities are strongly affected by past and recent volcanic activity.
Acknowledgement: This work is part of the Brains2Islands “INDAGINE MULTIDISCIPLINARE NEI CONTESTI INSULARI BASSO TIRRENICI” project Funded by FONDAZIONE CON IL SUD project number 2015-0296
How to cite: Alexandrakis, G., Nomi, F., Speciale, C., De Vita, S., and Di Vito, M. A.: Analysis between ancient human settlements and volcanic landscapes using earth observation and archaeological data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10556, https://doi.org/10.5194/egusphere-egu21-10556, 2021.
EGU21-7647 | vPICO presentations | GM12.7
Finding of artisanal uses of elemental mercury in the city of Murcia in medieval timesJosé María Esbrí, Luis Mansilla-Plaza, María Jesús Sanchez-Gonzalez, and Pablo Higueras
Mercury (Hg) was used in gilding techniques since ancient times. This metal gilding technique consisted of applying an amalgam of Au and Hg to the surface of a metallic object and then removing the Hg to achieve adhesion of the Au to the support. The traditional preparation of amalgam was a mixture of Au with Hg (in a ratio of 1/8). After this preparation, the mixture usually was ground in a mortar, heated, and then cooled by pouring it into water. The paste was applied to the areas to be browned and then the piece was subjected to mild temperatures so that the Hg evaporated, leaving a thin layer of Au on the surface of the object.
The origin of this work is the discovery of an evident quantity of liquid Hg on a site under construction, near the old wall of the city of Murcia, at a level identified as from medieval times. To elucidate the origin of this Hg, a sampling of medieval materials has been carried out throughout the site, including both the area with liquid Hg, the entire area what appears to be the work room and the adjacent rooms. The sampling has been carried out using an Ejkelkamp sampler at various depths. These soil samples were analysed by Energy Dispersion X-Ray Fluorescence using a PanAlytical device. Total Hg and Hg speciation data were obtained by Atomic Absorption Spectrometry using a Lumex equipment. In addition to this, a gaseous mercury monitoring has been carried out using a portable atomic absorption equipment to search Hg sources and gaseous Hg dispersion in the atmosphere of the studied site. Results of the survey has shown an evident and intense soil Hg pollution in a small area of 2x2 m. This affected area was located near the outer wall of the medieval building and was very restricted, which suggests that it was a storage place for liquid Hg for later use in other areas. The degassing of these recently uncovered materials produced a significant dispersion of the Hg gas throughout the enclosure. In addition to this, samples of medieval materials have shown very high concentrations of Hg in the vicinity of the contaminated area, and high concentrations in the rest of the enclosure. Speciation analysis have shown that the Hg in this part of the enclosure is in the form of metacinnabar and Hg bound to humic acids, which suggests the presence of an atmosphere with extremely high concentration of gaseous Hg in medieval times that was later deposited in the soil, being fixed to its organic phase. Multielemental analysis has shown additional high concentrations of Pb, Cu and Sn, suggesting that the artisanal works in the enclosure involved these elements too. While waiting for more specific archaeology works that can corroborate it, the origin of this Hg in the area could be the storage for the realization of gilding work on metals with this element.
This work was funded by the company “Obras y Proyectos Soyma”.
How to cite: Esbrí, J. M., Mansilla-Plaza, L., Sanchez-Gonzalez, M. J., and Higueras, P.: Finding of artisanal uses of elemental mercury in the city of Murcia in medieval times, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7647, https://doi.org/10.5194/egusphere-egu21-7647, 2021.
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Mercury (Hg) was used in gilding techniques since ancient times. This metal gilding technique consisted of applying an amalgam of Au and Hg to the surface of a metallic object and then removing the Hg to achieve adhesion of the Au to the support. The traditional preparation of amalgam was a mixture of Au with Hg (in a ratio of 1/8). After this preparation, the mixture usually was ground in a mortar, heated, and then cooled by pouring it into water. The paste was applied to the areas to be browned and then the piece was subjected to mild temperatures so that the Hg evaporated, leaving a thin layer of Au on the surface of the object.
The origin of this work is the discovery of an evident quantity of liquid Hg on a site under construction, near the old wall of the city of Murcia, at a level identified as from medieval times. To elucidate the origin of this Hg, a sampling of medieval materials has been carried out throughout the site, including both the area with liquid Hg, the entire area what appears to be the work room and the adjacent rooms. The sampling has been carried out using an Ejkelkamp sampler at various depths. These soil samples were analysed by Energy Dispersion X-Ray Fluorescence using a PanAlytical device. Total Hg and Hg speciation data were obtained by Atomic Absorption Spectrometry using a Lumex equipment. In addition to this, a gaseous mercury monitoring has been carried out using a portable atomic absorption equipment to search Hg sources and gaseous Hg dispersion in the atmosphere of the studied site. Results of the survey has shown an evident and intense soil Hg pollution in a small area of 2x2 m. This affected area was located near the outer wall of the medieval building and was very restricted, which suggests that it was a storage place for liquid Hg for later use in other areas. The degassing of these recently uncovered materials produced a significant dispersion of the Hg gas throughout the enclosure. In addition to this, samples of medieval materials have shown very high concentrations of Hg in the vicinity of the contaminated area, and high concentrations in the rest of the enclosure. Speciation analysis have shown that the Hg in this part of the enclosure is in the form of metacinnabar and Hg bound to humic acids, which suggests the presence of an atmosphere with extremely high concentration of gaseous Hg in medieval times that was later deposited in the soil, being fixed to its organic phase. Multielemental analysis has shown additional high concentrations of Pb, Cu and Sn, suggesting that the artisanal works in the enclosure involved these elements too. While waiting for more specific archaeology works that can corroborate it, the origin of this Hg in the area could be the storage for the realization of gilding work on metals with this element.
This work was funded by the company “Obras y Proyectos Soyma”.
How to cite: Esbrí, J. M., Mansilla-Plaza, L., Sanchez-Gonzalez, M. J., and Higueras, P.: Finding of artisanal uses of elemental mercury in the city of Murcia in medieval times, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7647, https://doi.org/10.5194/egusphere-egu21-7647, 2021.
EGU21-15808 | vPICO presentations | GM12.7 | Highlight
The Harz Mountains and the St. Andreasberg Mining District (Germany) as a key region for an interdisciplinary Anthropocene discourseLasafam Iturrizaga
The proposal to introduce a new geological epoch, the Anthropocene, has led to an increasingly intensive discourse on the concrete evidence of anthropogenic interventions in nature, their extent and exact beginning in Geosciences and neighboring disciplines, as well as on questions of a fundamental change in man-environmental relations especially in the humanities. The concept of the Anthropocene thus has become a socio-political relevance with regard to global environmental changes and their management.
The paper uses a conceptual model to illustrate the various proposals for formalizing the Anthropocene from the geoscientific perspective on the one hand and the complex interlinking of human-nature relationships on the other hand on the base of the Harz Region (Lower Saxony, Germany) and selected type localities for the Anthropocene. The Harz and its foreland possess numerous key localities in geological, geomorphological, vegetation and cultural-historical research as well as important geoarchaeological and settlement-historical sites. At a comparatively small spatial segment of the earth surface, the transitions from a natural to a human-dominated world can be demonstrated on different spatio-temporal scales from the Paleo-Anthropocene to the current modern Anthropocene based on a broad spectrum of Quaternary paleo-archives and cultural evidences. In the northern Harz foreland, there are significant geoarchaeological sites from the Paleolithic and in the southern Harz foreland from the Middle Paleolithic, including caves and settlement relics, with far-reaching implications for early human intervention in nature. Since the Bronze Age, the Harz Region was used for mining mineral resources. Since the Middle Ages and Modern Age at the latest, the Harz Mountains have been systematically developed for mining, and not least because of the rich silver ore deposits, they have been converted into an industrial landscape. Mining landscapes with special landform assemblages emerged at the local level, which not only changed the geological underground and geomorphological relief surface partly irreversibly, but also the vegetation and the hydrological system was profoundly changed with consequences for the future ecological system. The environmental impact, but above all the indirect consequences of mining activities in the context of the import and export of goods, the migrations of workers and exchange of knowledge extended far beyond the region to the global level.
In this regard the St. Andreasberg Mining District with the UNESCO World Heritage site of the Samson Pit, one of the centers of silver mining in the Harz Mountains, was selected as a key site for demonstrating the human impact since the times of the Columbian Exchange. It shows in a paradigmatic way the anthropogenic transformation of the natural landscape in the context of regional and global environmental changes in their complex human-nature interplay. At the same time, the recent change from a mining to a tourism landscape as well as approaches of sustainable development strategies in form of modern wilderness-concepts and the use of regenerative energies based on a century old water management system provide the base for future-oriented man-environment concepts.
How to cite: Iturrizaga, L.: The Harz Mountains and the St. Andreasberg Mining District (Germany) as a key region for an interdisciplinary Anthropocene discourse, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15808, https://doi.org/10.5194/egusphere-egu21-15808, 2021.
The proposal to introduce a new geological epoch, the Anthropocene, has led to an increasingly intensive discourse on the concrete evidence of anthropogenic interventions in nature, their extent and exact beginning in Geosciences and neighboring disciplines, as well as on questions of a fundamental change in man-environmental relations especially in the humanities. The concept of the Anthropocene thus has become a socio-political relevance with regard to global environmental changes and their management.
The paper uses a conceptual model to illustrate the various proposals for formalizing the Anthropocene from the geoscientific perspective on the one hand and the complex interlinking of human-nature relationships on the other hand on the base of the Harz Region (Lower Saxony, Germany) and selected type localities for the Anthropocene. The Harz and its foreland possess numerous key localities in geological, geomorphological, vegetation and cultural-historical research as well as important geoarchaeological and settlement-historical sites. At a comparatively small spatial segment of the earth surface, the transitions from a natural to a human-dominated world can be demonstrated on different spatio-temporal scales from the Paleo-Anthropocene to the current modern Anthropocene based on a broad spectrum of Quaternary paleo-archives and cultural evidences. In the northern Harz foreland, there are significant geoarchaeological sites from the Paleolithic and in the southern Harz foreland from the Middle Paleolithic, including caves and settlement relics, with far-reaching implications for early human intervention in nature. Since the Bronze Age, the Harz Region was used for mining mineral resources. Since the Middle Ages and Modern Age at the latest, the Harz Mountains have been systematically developed for mining, and not least because of the rich silver ore deposits, they have been converted into an industrial landscape. Mining landscapes with special landform assemblages emerged at the local level, which not only changed the geological underground and geomorphological relief surface partly irreversibly, but also the vegetation and the hydrological system was profoundly changed with consequences for the future ecological system. The environmental impact, but above all the indirect consequences of mining activities in the context of the import and export of goods, the migrations of workers and exchange of knowledge extended far beyond the region to the global level.
In this regard the St. Andreasberg Mining District with the UNESCO World Heritage site of the Samson Pit, one of the centers of silver mining in the Harz Mountains, was selected as a key site for demonstrating the human impact since the times of the Columbian Exchange. It shows in a paradigmatic way the anthropogenic transformation of the natural landscape in the context of regional and global environmental changes in their complex human-nature interplay. At the same time, the recent change from a mining to a tourism landscape as well as approaches of sustainable development strategies in form of modern wilderness-concepts and the use of regenerative energies based on a century old water management system provide the base for future-oriented man-environment concepts.
How to cite: Iturrizaga, L.: The Harz Mountains and the St. Andreasberg Mining District (Germany) as a key region for an interdisciplinary Anthropocene discourse, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15808, https://doi.org/10.5194/egusphere-egu21-15808, 2021.
EGU21-4354 | vPICO presentations | GM12.7
Is there an environmental crisis in Madagascar’s highlands? Insights from the spatio-temporal evolution and demographic modelling of lavaka (large gullies)Liesa Brosens, Benjamin Campforts, Liesbet Jacobs, Vao Fenotiana Razanamahandry, Quinten Van Moerbeke, Nils Broothaerts, Tantely Razafimbelo, Tovonarivo Rafolisy, Steven Bouillon, and Gerard Govers
The Malagasy highlands are scattered with large inverse teardrop-shaped gullies called lavaka, which are by many considered as the prime indication of a currently ongoing human-induced environmental crisis. Yet, these gullies are known to have existed long before human arrival on the island, resulting in the highly debated role of anthropogenic disturbances on their formation. Here, we assess the dynamics of 700 lavaka in the lake Alaotra region from 1949 to the 2010s by using historical aerial pictures and present day satellite imagery. An overall birth to stabilization ratio of 6.1 indicates a currently rapid growing lavaka population. Observed growth-, birth- and stabilization rates allowed us to calculate a mean lavaka population age of 410 ± 40 years, and estimate that the current crisis started at 943 ± 430 cal. yr BP. This timeframe corresponds well with the “subsistence-shift”, where people move from hunting and foraging to farming and herding practices upon the introduction of cattle in the region. These findings were integrated into a novel, temporally explicit lavaka population model - building upon the observed lavaka growth-, birth- and stabilization rates and lavaka size distributions - where different environmental pressure scenarios were tested. Modelling outcomes show that the currently observed lavaka crisis largely results from a rapid increase in environmental pressure over the last centuries, likely caused by the combined effects of deforestation and overgrazing related to human population growth and the introduction of cattle. With this study we show the potential of an integrated data-modeling approach, where demographic concepts are applied to geomorphological features, allowing to link their evolution with past anthropogenically driven environmental changes.
How to cite: Brosens, L., Campforts, B., Jacobs, L., Razanamahandry, V. F., Van Moerbeke, Q., Broothaerts, N., Razafimbelo, T., Rafolisy, T., Bouillon, S., and Govers, G.: Is there an environmental crisis in Madagascar’s highlands? Insights from the spatio-temporal evolution and demographic modelling of lavaka (large gullies), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4354, https://doi.org/10.5194/egusphere-egu21-4354, 2021.
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Forward to presentation link
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The Malagasy highlands are scattered with large inverse teardrop-shaped gullies called lavaka, which are by many considered as the prime indication of a currently ongoing human-induced environmental crisis. Yet, these gullies are known to have existed long before human arrival on the island, resulting in the highly debated role of anthropogenic disturbances on their formation. Here, we assess the dynamics of 700 lavaka in the lake Alaotra region from 1949 to the 2010s by using historical aerial pictures and present day satellite imagery. An overall birth to stabilization ratio of 6.1 indicates a currently rapid growing lavaka population. Observed growth-, birth- and stabilization rates allowed us to calculate a mean lavaka population age of 410 ± 40 years, and estimate that the current crisis started at 943 ± 430 cal. yr BP. This timeframe corresponds well with the “subsistence-shift”, where people move from hunting and foraging to farming and herding practices upon the introduction of cattle in the region. These findings were integrated into a novel, temporally explicit lavaka population model - building upon the observed lavaka growth-, birth- and stabilization rates and lavaka size distributions - where different environmental pressure scenarios were tested. Modelling outcomes show that the currently observed lavaka crisis largely results from a rapid increase in environmental pressure over the last centuries, likely caused by the combined effects of deforestation and overgrazing related to human population growth and the introduction of cattle. With this study we show the potential of an integrated data-modeling approach, where demographic concepts are applied to geomorphological features, allowing to link their evolution with past anthropogenically driven environmental changes.
How to cite: Brosens, L., Campforts, B., Jacobs, L., Razanamahandry, V. F., Van Moerbeke, Q., Broothaerts, N., Razafimbelo, T., Rafolisy, T., Bouillon, S., and Govers, G.: Is there an environmental crisis in Madagascar’s highlands? Insights from the spatio-temporal evolution and demographic modelling of lavaka (large gullies), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4354, https://doi.org/10.5194/egusphere-egu21-4354, 2021.
EGU21-12389 | vPICO presentations | GM12.7
Changes in human settlement during the Mesolithic of SW Iberia motivated by the rapid inundation of the coastSusana Costas, Ana Cristina Araújo, Ana Maria Costa, and Filipa Naughton
The transition to the Late Mesolithic (c. 8.4-7 ka) in SW Iberia has been characterized as a period of profound reorganization of human settlement. Such reorganization affected various aspects of cultural behaviour and was reflected by a tendency toward a more permanent settlement, changes in the mobility patterns of the human groups and the creation of the first burial grounds. These changes were concomitant with the apparent abandonment of coastal areas and the displacement of people toward the interior of newly formed large estuaries. The motivation behind such changes has been traditionally related to environmental conditions, in particular to the occurrence of the 8.2 ka cooling event whose impact in the landscape and the availability of resources would have been abrupt in these southern latitudes. Here, we revisit all the existing archaeological evidence for the time interval encompassing 11 and 7 ka in order to environmentally frame this behavioural change, paying particular attention to the settlement spatial distribution with regard to the configuration and position of the ancient shoreline and combining this information with environmental reconstructions available for this time interval. The integration of this information suggests that after 8.5 ka the sediment depleted coast north of Lisbon seems to have been abandoned, while the SW Alentejo coast continued to be occupied during the Late Mesolithic. The occurrence of abundant top-cliff dunes along this southern littoral fringe suggests a less sediment starved coast than the northern one that could accommodate wide sandy coastal plains, inviting human communities to continue exploiting sea resources. Conversely, the northern coast appears to have been abandoned due to the rapid sea-level rise that would have flooded the coastal plain, forcing the rapid retreat of this starved and unstable coastline. Simultaneously, the inundation of the coast between 11 and 7 ka created optimal conditions in the innermost areas of the large estuaries, attracting people to these rich and more stable environments. Such circumstances would invite people to gradually move to these new locations and to use coastal settlements mostly for logistic purposes where accommodation space for their activities was available. The latter also suggests that the perception that these communities had in relation to the coastline was completely oppose to ours. For them, the coast was an important element to fulfil their diet, however, the location of their settlements relative to the ancient coast suggests that they perceived the coast as an unstable and unsafe area, which motivated them to always keep a distance or only occupy the area unaffected by such instability. In addition, their occupation attitude, based on adaptation to the landscape rather than the opposite, explains their tendency to retreat from the mobile and unstable coast. It is worth mentioning that the latter hypothesis can be partially biased because of gaps in the archaeological record, in particular because of the lack of underwater archaeological explorations, which may hide an additional and relevant part of this history.
This work was supported by the project PTDC/CTA-GFI/28949/2017 and PTDC/CTA-GEO/28941/2017, funded by the Portuguese Foundation for Science and Technology.
How to cite: Costas, S., Araújo, A. C., Costa, A. M., and Naughton, F.: Changes in human settlement during the Mesolithic of SW Iberia motivated by the rapid inundation of the coast, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12389, https://doi.org/10.5194/egusphere-egu21-12389, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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The transition to the Late Mesolithic (c. 8.4-7 ka) in SW Iberia has been characterized as a period of profound reorganization of human settlement. Such reorganization affected various aspects of cultural behaviour and was reflected by a tendency toward a more permanent settlement, changes in the mobility patterns of the human groups and the creation of the first burial grounds. These changes were concomitant with the apparent abandonment of coastal areas and the displacement of people toward the interior of newly formed large estuaries. The motivation behind such changes has been traditionally related to environmental conditions, in particular to the occurrence of the 8.2 ka cooling event whose impact in the landscape and the availability of resources would have been abrupt in these southern latitudes. Here, we revisit all the existing archaeological evidence for the time interval encompassing 11 and 7 ka in order to environmentally frame this behavioural change, paying particular attention to the settlement spatial distribution with regard to the configuration and position of the ancient shoreline and combining this information with environmental reconstructions available for this time interval. The integration of this information suggests that after 8.5 ka the sediment depleted coast north of Lisbon seems to have been abandoned, while the SW Alentejo coast continued to be occupied during the Late Mesolithic. The occurrence of abundant top-cliff dunes along this southern littoral fringe suggests a less sediment starved coast than the northern one that could accommodate wide sandy coastal plains, inviting human communities to continue exploiting sea resources. Conversely, the northern coast appears to have been abandoned due to the rapid sea-level rise that would have flooded the coastal plain, forcing the rapid retreat of this starved and unstable coastline. Simultaneously, the inundation of the coast between 11 and 7 ka created optimal conditions in the innermost areas of the large estuaries, attracting people to these rich and more stable environments. Such circumstances would invite people to gradually move to these new locations and to use coastal settlements mostly for logistic purposes where accommodation space for their activities was available. The latter also suggests that the perception that these communities had in relation to the coastline was completely oppose to ours. For them, the coast was an important element to fulfil their diet, however, the location of their settlements relative to the ancient coast suggests that they perceived the coast as an unstable and unsafe area, which motivated them to always keep a distance or only occupy the area unaffected by such instability. In addition, their occupation attitude, based on adaptation to the landscape rather than the opposite, explains their tendency to retreat from the mobile and unstable coast. It is worth mentioning that the latter hypothesis can be partially biased because of gaps in the archaeological record, in particular because of the lack of underwater archaeological explorations, which may hide an additional and relevant part of this history.
This work was supported by the project PTDC/CTA-GFI/28949/2017 and PTDC/CTA-GEO/28941/2017, funded by the Portuguese Foundation for Science and Technology.
How to cite: Costas, S., Araújo, A. C., Costa, A. M., and Naughton, F.: Changes in human settlement during the Mesolithic of SW Iberia motivated by the rapid inundation of the coast, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12389, https://doi.org/10.5194/egusphere-egu21-12389, 2021.
EGU21-3986 | vPICO presentations | GM12.7
Holocene alluvial floodplains in Belgium: from natural to human-dominated environmentsRenske Hoevers, Nils Broothaerts, Ward Swinnen, and Gert Verstraeten
Rivers and alluvial floodplains are dynamic environments that experience both natural and anthropogenic impacts. Sustainable management of these ecosystems requires a thorough understanding of the functioning of floodplains and their sensitivity to changes in driving forces, including anthropogenic land-cover change. Looking at past human-environment interactions in river catchments can help to develop such sustainable management strategies for the future.
During the Early and Middle Holocene, most floodplains in northeastern Belgium were stable environments, mainly driven by natural forces, resulting in large marshes where peat accumulated and river channels were absent or small. During the Late Holocene, these environments changed completely towards single channel meandering rivers with overbank deposits, impeding peat accumulation. These changes can to a large extent be linked to increasing human activities in the catchment. However, the timing of this change in floodplain geoecology strongly varies within and between different catchments.
Five river catchments in northeastern Belgium with varying soil properties, topographies, and durations and intensities of human impact were selected in this study, to uncover regional differences in land-cover evolution. The catchments of Dijle (750 km²), Grote Gete (300 km²) and Mombeek (90 km²) are located in the central Belgian loess belt, whereas the Grote Nete (525 km²) and Zwarte Beek catchments (50 km²) are situated in the sandy Campine region. A multi-proxy approach, including sedimentological proxies, pollen, and macrobotanical remains, was chosen to reconstruct alluvial floodplain characteristics and anthropogenic land-cover changes. We constructed a database of 27 records for these five catchments (of which 9 containing pollen, 4 containing macrobotanical remains, and 14 containing both) for which 132 radiocarbon dates in total provide a chronostratigraphic framework.
Qualitative, semi-quantitative (NMDS) and quantitative (REVEALS) analyses of the palynological data revealed regional differences in the initiation and intensity of human impact. From the Neolithic period onwards, deforestation is detected in both the loess and sandy region, although the loess belt underwent a more rapid and severe reduction of woodland. While this deforestation is accompanied by an increase in cropland in the loess region from the Bronze Age onwards, the sandy region only starts to show limited agriculture from the Iron Age onwards, related to its later and less dense human occupation.
While the amount of records and their resolution is rather low in the sandy region, the numerous and detailed records of the loess belt also allow detection of more local and short-term effects (< 200 years) of changes in human impact. A decrease in human impact during the Dark Ages, which can be related to the decreased population density in Europe during the first millennium AD, is visible: hillslope–floodplain connectivity reduced due to the regeneration of vegetation barriers, in turn lowering sediment input, which facilitated local reactivation of peat growth and regrowth of the natural alder-carr floodplain vegetation. After this temporary decrease, human impact on floodplain geoecology started to increase again up till modern times. The impact also got more direct, as peat extraction from the floodplains became common practice, especially in the sandy Campine region.
How to cite: Hoevers, R., Broothaerts, N., Swinnen, W., and Verstraeten, G.: Holocene alluvial floodplains in Belgium: from natural to human-dominated environments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3986, https://doi.org/10.5194/egusphere-egu21-3986, 2021.
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Rivers and alluvial floodplains are dynamic environments that experience both natural and anthropogenic impacts. Sustainable management of these ecosystems requires a thorough understanding of the functioning of floodplains and their sensitivity to changes in driving forces, including anthropogenic land-cover change. Looking at past human-environment interactions in river catchments can help to develop such sustainable management strategies for the future.
During the Early and Middle Holocene, most floodplains in northeastern Belgium were stable environments, mainly driven by natural forces, resulting in large marshes where peat accumulated and river channels were absent or small. During the Late Holocene, these environments changed completely towards single channel meandering rivers with overbank deposits, impeding peat accumulation. These changes can to a large extent be linked to increasing human activities in the catchment. However, the timing of this change in floodplain geoecology strongly varies within and between different catchments.
Five river catchments in northeastern Belgium with varying soil properties, topographies, and durations and intensities of human impact were selected in this study, to uncover regional differences in land-cover evolution. The catchments of Dijle (750 km²), Grote Gete (300 km²) and Mombeek (90 km²) are located in the central Belgian loess belt, whereas the Grote Nete (525 km²) and Zwarte Beek catchments (50 km²) are situated in the sandy Campine region. A multi-proxy approach, including sedimentological proxies, pollen, and macrobotanical remains, was chosen to reconstruct alluvial floodplain characteristics and anthropogenic land-cover changes. We constructed a database of 27 records for these five catchments (of which 9 containing pollen, 4 containing macrobotanical remains, and 14 containing both) for which 132 radiocarbon dates in total provide a chronostratigraphic framework.
Qualitative, semi-quantitative (NMDS) and quantitative (REVEALS) analyses of the palynological data revealed regional differences in the initiation and intensity of human impact. From the Neolithic period onwards, deforestation is detected in both the loess and sandy region, although the loess belt underwent a more rapid and severe reduction of woodland. While this deforestation is accompanied by an increase in cropland in the loess region from the Bronze Age onwards, the sandy region only starts to show limited agriculture from the Iron Age onwards, related to its later and less dense human occupation.
While the amount of records and their resolution is rather low in the sandy region, the numerous and detailed records of the loess belt also allow detection of more local and short-term effects (< 200 years) of changes in human impact. A decrease in human impact during the Dark Ages, which can be related to the decreased population density in Europe during the first millennium AD, is visible: hillslope–floodplain connectivity reduced due to the regeneration of vegetation barriers, in turn lowering sediment input, which facilitated local reactivation of peat growth and regrowth of the natural alder-carr floodplain vegetation. After this temporary decrease, human impact on floodplain geoecology started to increase again up till modern times. The impact also got more direct, as peat extraction from the floodplains became common practice, especially in the sandy Campine region.
How to cite: Hoevers, R., Broothaerts, N., Swinnen, W., and Verstraeten, G.: Holocene alluvial floodplains in Belgium: from natural to human-dominated environments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3986, https://doi.org/10.5194/egusphere-egu21-3986, 2021.
EGU21-8647 | vPICO presentations | GM12.7 | Highlight
A hydromorphic re-evaluation of Central Asia's Medieval floodwater farming civilizationsWillem Toonen, Mark Macklin, Giles Dawkes, and Julie Durcan
The Aral Sea basin in Central Asia and its major rivers the Amu Darya and Syr Darya were the center of advanced river civilizations, and a principal hub of the Silk Roads trade network. The region’s decline has been traditionally attributed to the Mongol invasion of the early-13th century CE. In this study, we demonstrate the role of changing hydroclimatic conditions on the development of these culturally influential potamic societies that were depending on floodwater farming. Radiometric dating of irrigation canal abandonment and an investigation of regional river channel dynamics at Otrār oasis, a UNESCO World Heritage site located at the confluence of the Syr Darya and Arys rivers in southern Kazakhstan, revealed that major phases of fluvial aggradation occurred between the 7th to early-9th century CE and the mid-14th to mid-16th century CE. These periods coincide with economic flourishing of the oasis, facilitated by NAO-induced wet climatic conditions and higher river flows that favored floodwater farming. Periods of abandonment of the irrigation network and cultural decline primarily correlate with fluvial entrenchment during periods of drought. As the decline of the region seems to have initiated before the arrival of Ghenghis Khan and his armies, climate change has to be considered as a pivotal factor in the region's final demise.
How to cite: Toonen, W., Macklin, M., Dawkes, G., and Durcan, J.: A hydromorphic re-evaluation of Central Asia's Medieval floodwater farming civilizations , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8647, https://doi.org/10.5194/egusphere-egu21-8647, 2021.
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The Aral Sea basin in Central Asia and its major rivers the Amu Darya and Syr Darya were the center of advanced river civilizations, and a principal hub of the Silk Roads trade network. The region’s decline has been traditionally attributed to the Mongol invasion of the early-13th century CE. In this study, we demonstrate the role of changing hydroclimatic conditions on the development of these culturally influential potamic societies that were depending on floodwater farming. Radiometric dating of irrigation canal abandonment and an investigation of regional river channel dynamics at Otrār oasis, a UNESCO World Heritage site located at the confluence of the Syr Darya and Arys rivers in southern Kazakhstan, revealed that major phases of fluvial aggradation occurred between the 7th to early-9th century CE and the mid-14th to mid-16th century CE. These periods coincide with economic flourishing of the oasis, facilitated by NAO-induced wet climatic conditions and higher river flows that favored floodwater farming. Periods of abandonment of the irrigation network and cultural decline primarily correlate with fluvial entrenchment during periods of drought. As the decline of the region seems to have initiated before the arrival of Ghenghis Khan and his armies, climate change has to be considered as a pivotal factor in the region's final demise.
How to cite: Toonen, W., Macklin, M., Dawkes, G., and Durcan, J.: A hydromorphic re-evaluation of Central Asia's Medieval floodwater farming civilizations , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8647, https://doi.org/10.5194/egusphere-egu21-8647, 2021.
EGU21-4518 | vPICO presentations | GM12.7
Flood and desiccation events reconstructed based on luminescence profiles and palaeobotanical proxies from the High Arctic lake Tenndammen, SvalbardAnastasia Poliakova, Antony G. Brown, David C.W. Sanderson, and Inger G. Alsos
We present a 700-year reconstruction of the environmental changes in the Colesdalen, Svalbard, inferred from a sediment core retrieved from lake Tenndammen (N 78°06.118; E 15°02.024). A comparison of modern and old maps revealed that the lake was artificially connected to its western tribute that now inputs additional water and sediment into the lake, but earlier lake Tenndammen was mainly fed by discharge and groundwater from the main valley. A multi-proxy approach was applied involving sedimentary ancient DNA (sedaDNA), pollen, spores, plant macrofossils, sedimentology and biogeochemistry. Establishing a chronology for this core was problematic as nine of the fourteen AMS dates were revered. However, core imaging as well as X-ray fluorescence (XRF) demonstrated clear stratification and undisturbed sediment layers. This is supported by the clear and coherent data obtained from the plant palaeo-proxies in terms of vegetation and environmental changes indicated by all proxies at the same core depths. From these observations, we inferred that lake Tenndammen experienced a number of floods which brought older sediments into the lake and produced a high proportion of the reversed dates. In order to test this hypothesis, portable optically stimulated luminescence (pOSL) and infrared stimulated luminescence (pIRSL) was employed. The pIRSL, pOSL and pIRSL/pOSL profiles suggested a series of 15 flooding and 8 drying events occurring at the depths associated with the reversed dates. However, relatively high amount of spheroidal carbonaceous particles (SCP, up to 1300 per gram of dried sediment mass) helped to improve the core chronology through a comparison with the calendar dates of the history of the coal mining and power production in Svalbard. SCP record allowed to find three tie points for the age-depth model at (1) the construction time of the power plant in 1911-1913 in Colesdalen, (2) the abrupt decrease in SCPs associated with the Second World War in 1941-1946, and (3) the highest output of the power plant in Colesdalen in the middle of the 1950s. When combined with the earlier non-reversed dates this provides an age-depth model with the basal age of the core at c. 730 cal. yr. BP and with the upper sediments deposited at c. 1950-1980s. Using this revised age-depth model, four chrono-stratigraphic units were described and, according to the data on luminescence profiling, the most intensive floods were associated with the second unit, which corresponded with the most intensive ice melting in the study area (c. 1670 - 1420 BP). The strongest drying events took place at the end of the second unit and in the first part of the third unit (c. 1655 BP). This was supported by the plant proxies with an abundance of the aquatic and swamp bryophyta Warnstorfia exannulata/Warnstorfia fluitans, algae (i.e. Closterium littorale, Cosmarium botrytis and Staurastrum punctulatum) both in the non-pollen microfossils record and the sedaDNA. This study shows that a combination of biological proxies, sedimentology and pOSL can detect flood and desiccation events, and that lake Tenndammen was a highly sensitive fluvio-lacustrine systems during the late Holocene/Anthropocene.
How to cite: Poliakova, A., Brown, A. G., Sanderson, D. C. W., and Alsos, I. G.: Flood and desiccation events reconstructed based on luminescence profiles and palaeobotanical proxies from the High Arctic lake Tenndammen, Svalbard, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4518, https://doi.org/10.5194/egusphere-egu21-4518, 2021.
We present a 700-year reconstruction of the environmental changes in the Colesdalen, Svalbard, inferred from a sediment core retrieved from lake Tenndammen (N 78°06.118; E 15°02.024). A comparison of modern and old maps revealed that the lake was artificially connected to its western tribute that now inputs additional water and sediment into the lake, but earlier lake Tenndammen was mainly fed by discharge and groundwater from the main valley. A multi-proxy approach was applied involving sedimentary ancient DNA (sedaDNA), pollen, spores, plant macrofossils, sedimentology and biogeochemistry. Establishing a chronology for this core was problematic as nine of the fourteen AMS dates were revered. However, core imaging as well as X-ray fluorescence (XRF) demonstrated clear stratification and undisturbed sediment layers. This is supported by the clear and coherent data obtained from the plant palaeo-proxies in terms of vegetation and environmental changes indicated by all proxies at the same core depths. From these observations, we inferred that lake Tenndammen experienced a number of floods which brought older sediments into the lake and produced a high proportion of the reversed dates. In order to test this hypothesis, portable optically stimulated luminescence (pOSL) and infrared stimulated luminescence (pIRSL) was employed. The pIRSL, pOSL and pIRSL/pOSL profiles suggested a series of 15 flooding and 8 drying events occurring at the depths associated with the reversed dates. However, relatively high amount of spheroidal carbonaceous particles (SCP, up to 1300 per gram of dried sediment mass) helped to improve the core chronology through a comparison with the calendar dates of the history of the coal mining and power production in Svalbard. SCP record allowed to find three tie points for the age-depth model at (1) the construction time of the power plant in 1911-1913 in Colesdalen, (2) the abrupt decrease in SCPs associated with the Second World War in 1941-1946, and (3) the highest output of the power plant in Colesdalen in the middle of the 1950s. When combined with the earlier non-reversed dates this provides an age-depth model with the basal age of the core at c. 730 cal. yr. BP and with the upper sediments deposited at c. 1950-1980s. Using this revised age-depth model, four chrono-stratigraphic units were described and, according to the data on luminescence profiling, the most intensive floods were associated with the second unit, which corresponded with the most intensive ice melting in the study area (c. 1670 - 1420 BP). The strongest drying events took place at the end of the second unit and in the first part of the third unit (c. 1655 BP). This was supported by the plant proxies with an abundance of the aquatic and swamp bryophyta Warnstorfia exannulata/Warnstorfia fluitans, algae (i.e. Closterium littorale, Cosmarium botrytis and Staurastrum punctulatum) both in the non-pollen microfossils record and the sedaDNA. This study shows that a combination of biological proxies, sedimentology and pOSL can detect flood and desiccation events, and that lake Tenndammen was a highly sensitive fluvio-lacustrine systems during the late Holocene/Anthropocene.
How to cite: Poliakova, A., Brown, A. G., Sanderson, D. C. W., and Alsos, I. G.: Flood and desiccation events reconstructed based on luminescence profiles and palaeobotanical proxies from the High Arctic lake Tenndammen, Svalbard, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4518, https://doi.org/10.5194/egusphere-egu21-4518, 2021.
EGU21-9542 | vPICO presentations | GM12.7
Revision and preliminary excavation finds of the Early Islamic Plot-and-Berm groundwater harvesting agroecosystem by ancient Caesarea, IsraelItamar Taxel and Joel Roskin
“Plot-and-Berm” (P&B) agroecosystems consist of sophisticated agricultural utilization of a high-water table within loose sand sheets, situated in agricultural hinterlands. Sunken agricultural plots between 3-6 m high sand berms coated with anthropogenic refuse/fines protect them from erosion. The plot level enables easy access to the groundwater for crop roots and shallow well construction, while refuse and organic material enrich the inert sand forming distinct grey sand-loam anthrosols. The agroecosystems require significant resources for construction and maintenance. The earliest recognized P&B agroecosystems are Early Islamic to early Crusader (9th-early 12th centuries a.d.) within several coastal sand bodies of Israel that were abandoned by unclear reasons. Similar agroecosystems in Iberia and Algeria and the southeastern Mediterranean (mawasi) coast historically date to the Middle Ages and early modern period.
Here we reexamine the unpublished data of the only previous excavation (Porath, 1975) and present field and artifactual finds along with pulsed-photon portable luminescence (PPSL) profiling from our 2020 research excavation of the agroecosystem, at the southern outskirts of ancient Caesarea in order to refine understandings on construction materials, structure types and roles, and agroecosystem function, maintenance and timespan.
Berms are found to be constructed from over 3 m thick anthropogenic-mixed sand while their grey sand-loam anthrosol coat is differentially distributed. The ~30 cm thick grey sand-loam anthrosols of the plots still possess distinct contacts with the over- and under-lying sand. Probes in the eastern margins of the agroecosystem reveal sand with Roman sherds. Structural remains include short stand-alone walls, small storage/watching structures, and a unique structure on the western-most berm overlooking the beach with a 3 m deep stone wall and grey sand loam substrate. All of the structures and earthworks possess Early Islamic ceramics along with remains from Roman-Byzantine Caesarea.
How to cite: Taxel, I. and Roskin, J.: Revision and preliminary excavation finds of the Early Islamic Plot-and-Berm groundwater harvesting agroecosystem by ancient Caesarea, Israel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9542, https://doi.org/10.5194/egusphere-egu21-9542, 2021.
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“Plot-and-Berm” (P&B) agroecosystems consist of sophisticated agricultural utilization of a high-water table within loose sand sheets, situated in agricultural hinterlands. Sunken agricultural plots between 3-6 m high sand berms coated with anthropogenic refuse/fines protect them from erosion. The plot level enables easy access to the groundwater for crop roots and shallow well construction, while refuse and organic material enrich the inert sand forming distinct grey sand-loam anthrosols. The agroecosystems require significant resources for construction and maintenance. The earliest recognized P&B agroecosystems are Early Islamic to early Crusader (9th-early 12th centuries a.d.) within several coastal sand bodies of Israel that were abandoned by unclear reasons. Similar agroecosystems in Iberia and Algeria and the southeastern Mediterranean (mawasi) coast historically date to the Middle Ages and early modern period.
Here we reexamine the unpublished data of the only previous excavation (Porath, 1975) and present field and artifactual finds along with pulsed-photon portable luminescence (PPSL) profiling from our 2020 research excavation of the agroecosystem, at the southern outskirts of ancient Caesarea in order to refine understandings on construction materials, structure types and roles, and agroecosystem function, maintenance and timespan.
Berms are found to be constructed from over 3 m thick anthropogenic-mixed sand while their grey sand-loam anthrosol coat is differentially distributed. The ~30 cm thick grey sand-loam anthrosols of the plots still possess distinct contacts with the over- and under-lying sand. Probes in the eastern margins of the agroecosystem reveal sand with Roman sherds. Structural remains include short stand-alone walls, small storage/watching structures, and a unique structure on the western-most berm overlooking the beach with a 3 m deep stone wall and grey sand loam substrate. All of the structures and earthworks possess Early Islamic ceramics along with remains from Roman-Byzantine Caesarea.
How to cite: Taxel, I. and Roskin, J.: Revision and preliminary excavation finds of the Early Islamic Plot-and-Berm groundwater harvesting agroecosystem by ancient Caesarea, Israel, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9542, https://doi.org/10.5194/egusphere-egu21-9542, 2021.
EGU21-579 | vPICO presentations | GM12.7
Enhancing the detection of buried anthropogenic features thought a cloud-computing Python procedureFilippo Brandolini, Guillem Domingo-Ribas, Andrea Zerboni, and Sam Turner
The necessity of sustainable development for landscapes has emerged as an important theme in recent decades. Moreover, past landscape reconstruction enables a better understanding of human resilience to climatic and environmental changes in different periods and locations, and illustrates examples of sustainable development in the past. Free and open-source (FOSS) datasets of satellite imagery offer considerable opportunities for landscape heritage stakeholders both for recording and monitoring activities. In this research, a completely FOSS-cloud procedure to enhance the detection of palaeo-landscape features is presented. Sentinel - 2 satellite imagery has been retrieved in the Google Earth Engine dataset collection and analysed through a Python script code realized in Google Colaboratory. A multi-temporal approach has been adopted to investigate the potential of satellite imagery to detect buried features along with Spectral Index (i.e., RGB, False Short Wave Infrared Colour and Bare Soil Index) and Spectral Decomposition analysis (i.e., Hue, Saturation and Value, Tasselled Cap Transformation and Principal Component Analysis). This procedure has been tested in the Po Plain (Northern Italy), chosen because it is characterized by human-landscape interaction since the Mid-Holocene. Thanks to its complex settlement and land-management history, the Po Plain represents an ideal laboratory to assess the potentiality of satellite imagery to enhance riverscapes’ palaeo-features. The outputs obtained can be visualized directly in the Google Colaboratory browser or downloaded via Google Drive for further graphical applications or spatial analysis. The buried features detected have been checked through the available geomorphological and archaeological literature; published case studies interpreting the occurrence of buried features served as a benchmark to validate the script code developed. This research represents one of the first applications of the GEE Python API in landscape studies. The main advantages of this procedure consist of: i) being FOSS, all the software used here are open-licensed; ii) working in cloud, no powerful hardware is necessary to run the script code; iii) high adaptability, changing the ROI is possible to calculate SI and SD outputs for any area of the world; iv) very basic coding skills are required to adapt the code to a ROI with different environmental characteristics. The development of FOSS-cloud procedures could support the identification, conservation and management of cultural and natural heritage anywhere around the world. In remote areas or where local heritage is threatened as a result of political instability, climate change or other factors, FOSS-cloud protocols can facilitate the application of new scientific methods and enable the dissemination of and access to scientific information.
How to cite: Brandolini, F., Domingo-Ribas, G., Zerboni, A., and Turner, S.: Enhancing the detection of buried anthropogenic features thought a cloud-computing Python procedure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-579, https://doi.org/10.5194/egusphere-egu21-579, 2021.
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The necessity of sustainable development for landscapes has emerged as an important theme in recent decades. Moreover, past landscape reconstruction enables a better understanding of human resilience to climatic and environmental changes in different periods and locations, and illustrates examples of sustainable development in the past. Free and open-source (FOSS) datasets of satellite imagery offer considerable opportunities for landscape heritage stakeholders both for recording and monitoring activities. In this research, a completely FOSS-cloud procedure to enhance the detection of palaeo-landscape features is presented. Sentinel - 2 satellite imagery has been retrieved in the Google Earth Engine dataset collection and analysed through a Python script code realized in Google Colaboratory. A multi-temporal approach has been adopted to investigate the potential of satellite imagery to detect buried features along with Spectral Index (i.e., RGB, False Short Wave Infrared Colour and Bare Soil Index) and Spectral Decomposition analysis (i.e., Hue, Saturation and Value, Tasselled Cap Transformation and Principal Component Analysis). This procedure has been tested in the Po Plain (Northern Italy), chosen because it is characterized by human-landscape interaction since the Mid-Holocene. Thanks to its complex settlement and land-management history, the Po Plain represents an ideal laboratory to assess the potentiality of satellite imagery to enhance riverscapes’ palaeo-features. The outputs obtained can be visualized directly in the Google Colaboratory browser or downloaded via Google Drive for further graphical applications or spatial analysis. The buried features detected have been checked through the available geomorphological and archaeological literature; published case studies interpreting the occurrence of buried features served as a benchmark to validate the script code developed. This research represents one of the first applications of the GEE Python API in landscape studies. The main advantages of this procedure consist of: i) being FOSS, all the software used here are open-licensed; ii) working in cloud, no powerful hardware is necessary to run the script code; iii) high adaptability, changing the ROI is possible to calculate SI and SD outputs for any area of the world; iv) very basic coding skills are required to adapt the code to a ROI with different environmental characteristics. The development of FOSS-cloud procedures could support the identification, conservation and management of cultural and natural heritage anywhere around the world. In remote areas or where local heritage is threatened as a result of political instability, climate change or other factors, FOSS-cloud protocols can facilitate the application of new scientific methods and enable the dissemination of and access to scientific information.
How to cite: Brandolini, F., Domingo-Ribas, G., Zerboni, A., and Turner, S.: Enhancing the detection of buried anthropogenic features thought a cloud-computing Python procedure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-579, https://doi.org/10.5194/egusphere-egu21-579, 2021.
EGU21-15296 | vPICO presentations | GM12.7
Machine Learning (Neuronal Net, Random Forest, and C5.0 single decision tree) based on pXRF data as a tool to date sediment layers of the Nile DeltaMartin Seeliger, Marina Altmeyer, Andreas Ginau, Robert Schiestl, and Jürgen Wunderlich
This paper presents the application of machine-learning techniques on pXRF data to establish a chronology for sediment cores around Tell Buto (Tell el-Fara´in) in the northwestern Nile Delta. As modern laboratories for dating techniques like OSL or 14C are rare in Egypt and sample export is restricted, we are facing a lack of opportunities to create a robust chronology, which is indispensable in modern Geoarchaeology.
Therefore, we present a new approach to transfer archaeological age information gained at the excavation at Buto to corings of the wider Buto area. Sediments of archaeological outcrops and pits with known age are measured using pXRF to create a geochemical “fingerprint” for several historic eras. Afterwards, these “fingerprints” are transferred to corings of the surrounding areas using machine-learning algorithms.
This paper presents 1) the application of three different machine-learning approaches (Neuronal Net, Random Forest, and C5.0 decision tree) to check if archaeological age information can be transferred to sediments far off the settlement mounds using pXRF data, 2) the comparison of all approaches and the evaluation if the easily anticipated decision tree and Random Forest show similar results as the “black-box system” Neuronal Net, and finally, 3) a case study that provides the results of Altmeyer et al. (in review) for Kom el-Gir, a further settlement mound little north of Buto, with a chronostratigraphic framework based on this approach.
Reference:
Altmeyer, M., Seeliger, M., Ginau, A., Schiestl, R. & J. Wunderlich (in review): Reconstruction of former channel systems in the northwestern Nile Delta (Egypt) based on corings and electrical resistivity tomography (ERT). (Submitted to E & G Quaternary Science Journal).
How to cite: Seeliger, M., Altmeyer, M., Ginau, A., Schiestl, R., and Wunderlich, J.: Machine Learning (Neuronal Net, Random Forest, and C5.0 single decision tree) based on pXRF data as a tool to date sediment layers of the Nile Delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15296, https://doi.org/10.5194/egusphere-egu21-15296, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
This paper presents the application of machine-learning techniques on pXRF data to establish a chronology for sediment cores around Tell Buto (Tell el-Fara´in) in the northwestern Nile Delta. As modern laboratories for dating techniques like OSL or 14C are rare in Egypt and sample export is restricted, we are facing a lack of opportunities to create a robust chronology, which is indispensable in modern Geoarchaeology.
Therefore, we present a new approach to transfer archaeological age information gained at the excavation at Buto to corings of the wider Buto area. Sediments of archaeological outcrops and pits with known age are measured using pXRF to create a geochemical “fingerprint” for several historic eras. Afterwards, these “fingerprints” are transferred to corings of the surrounding areas using machine-learning algorithms.
This paper presents 1) the application of three different machine-learning approaches (Neuronal Net, Random Forest, and C5.0 decision tree) to check if archaeological age information can be transferred to sediments far off the settlement mounds using pXRF data, 2) the comparison of all approaches and the evaluation if the easily anticipated decision tree and Random Forest show similar results as the “black-box system” Neuronal Net, and finally, 3) a case study that provides the results of Altmeyer et al. (in review) for Kom el-Gir, a further settlement mound little north of Buto, with a chronostratigraphic framework based on this approach.
Reference:
Altmeyer, M., Seeliger, M., Ginau, A., Schiestl, R. & J. Wunderlich (in review): Reconstruction of former channel systems in the northwestern Nile Delta (Egypt) based on corings and electrical resistivity tomography (ERT). (Submitted to E & G Quaternary Science Journal).
How to cite: Seeliger, M., Altmeyer, M., Ginau, A., Schiestl, R., and Wunderlich, J.: Machine Learning (Neuronal Net, Random Forest, and C5.0 single decision tree) based on pXRF data as a tool to date sediment layers of the Nile Delta, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15296, https://doi.org/10.5194/egusphere-egu21-15296, 2021.
GM12.8 – Visages of Geoheritage
EGU21-92 | vPICO presentations | GM12.8 | Highlight
Zoogeomorphosite: A concept for, and example of, linking geoheritage and biodiversity heritageFrançois Bétard
Zoogeomorphosites can be defined as geomorphological sites of special interest for animal biodiversity and conservation. They appear as ideal places for linking geoheritage and biodiversity heritage because of the reciprocal effects and interactions between landforms and animals. On one hand, geomorphodiversity exerts an influence on animal biodiversity at alpha, beta and gamma levels, and many landforms constitute valuable habitats for a wide range of animal species. On the other hand, animals can have direct and indirect geomorphic effects by creating specific landforms (e.g., mounds) and by influencing geomorphic processes (e.g, runoff), respectively.
The aim of this presentation is (1) to illustrate a worldwide range of sites fitting the conceptual definition of a zoogeomorphosite, with a proposed typology, and (2) to present an example of zoogeomorphological survey conducted on a site in Northwest France (Bois-des-Jarries, Vendée), where geoheritage meets with biodiversity heritage. The selected study site is a granitic geomorphosite composed of two hills with small tors and boulders outcropping at 230-260 m a.s.l., and franging a large fluvial paleo-valley of Ypresian age. The land cover is a mosaic of mixed forests and dry heathlands recognized for their high ecological interest, with many valuable species of vascular plants, birds and invertebrates. A major zoogeomorphic interest of the site is that it hosts an important population of mound-building red wood ants (Formica rufa), a regionally rare and vulnerable species responsible for an impressive collection of biogenic microlandforms (ant mounds) on a small surface (62 ha). A zoogeomorphogical survey carried out in summer 2020 on these ant mounds involved a two-stage methodology: (1) linear surveys along forest paths, in order to calculate mound densities and to proceed with a general inventory of ant mounds; (2) morphometric measurements of mounds using strip transects in 13 representative habitat types, in order to calculate mound volumes and to evaluate their evolution on a 5-years period.
119 mounds of Formica rufa have been inventoried in summer 2020 along the forest paths, indicating a density of 2-4 mounds ha–1. First results of the morphometric measurements indicate that the highest biovolumes are found in pine or mixed forest habitats, and that the geomorphology of the granitic hills (slope, aspect, height above drainage, etc.) is of major influence on their distribution and shape. In turn, ant mounds create environmental heterogeneity, or patch-scale geodiversity, highly favourable to biodiversity, notably because they offer microhabitats for various myrmecophilous insects. Finally, ant mounds can be viewed as a remarkable example of biogeomorphological heritage, hybrid and evolutionary in nature, but highly sensitive to environmental and human-induced changes (e.g., forest clear cuts, tourism pressure). Because ant mounds are an integral component of natural heritage and a key provider of ecosystem services, their inventory and protection as zoogeomorphosites – just like that of termite mounds – are of prime relevance in the wider scope of integrating geodiversity and biodiversity in nature conservation policies and strategies.
How to cite: Bétard, F.: Zoogeomorphosite: A concept for, and example of, linking geoheritage and biodiversity heritage, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-92, https://doi.org/10.5194/egusphere-egu21-92, 2021.
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Zoogeomorphosites can be defined as geomorphological sites of special interest for animal biodiversity and conservation. They appear as ideal places for linking geoheritage and biodiversity heritage because of the reciprocal effects and interactions between landforms and animals. On one hand, geomorphodiversity exerts an influence on animal biodiversity at alpha, beta and gamma levels, and many landforms constitute valuable habitats for a wide range of animal species. On the other hand, animals can have direct and indirect geomorphic effects by creating specific landforms (e.g., mounds) and by influencing geomorphic processes (e.g, runoff), respectively.
The aim of this presentation is (1) to illustrate a worldwide range of sites fitting the conceptual definition of a zoogeomorphosite, with a proposed typology, and (2) to present an example of zoogeomorphological survey conducted on a site in Northwest France (Bois-des-Jarries, Vendée), where geoheritage meets with biodiversity heritage. The selected study site is a granitic geomorphosite composed of two hills with small tors and boulders outcropping at 230-260 m a.s.l., and franging a large fluvial paleo-valley of Ypresian age. The land cover is a mosaic of mixed forests and dry heathlands recognized for their high ecological interest, with many valuable species of vascular plants, birds and invertebrates. A major zoogeomorphic interest of the site is that it hosts an important population of mound-building red wood ants (Formica rufa), a regionally rare and vulnerable species responsible for an impressive collection of biogenic microlandforms (ant mounds) on a small surface (62 ha). A zoogeomorphogical survey carried out in summer 2020 on these ant mounds involved a two-stage methodology: (1) linear surveys along forest paths, in order to calculate mound densities and to proceed with a general inventory of ant mounds; (2) morphometric measurements of mounds using strip transects in 13 representative habitat types, in order to calculate mound volumes and to evaluate their evolution on a 5-years period.
119 mounds of Formica rufa have been inventoried in summer 2020 along the forest paths, indicating a density of 2-4 mounds ha–1. First results of the morphometric measurements indicate that the highest biovolumes are found in pine or mixed forest habitats, and that the geomorphology of the granitic hills (slope, aspect, height above drainage, etc.) is of major influence on their distribution and shape. In turn, ant mounds create environmental heterogeneity, or patch-scale geodiversity, highly favourable to biodiversity, notably because they offer microhabitats for various myrmecophilous insects. Finally, ant mounds can be viewed as a remarkable example of biogeomorphological heritage, hybrid and evolutionary in nature, but highly sensitive to environmental and human-induced changes (e.g., forest clear cuts, tourism pressure). Because ant mounds are an integral component of natural heritage and a key provider of ecosystem services, their inventory and protection as zoogeomorphosites – just like that of termite mounds – are of prime relevance in the wider scope of integrating geodiversity and biodiversity in nature conservation policies and strategies.
How to cite: Bétard, F.: Zoogeomorphosite: A concept for, and example of, linking geoheritage and biodiversity heritage, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-92, https://doi.org/10.5194/egusphere-egu21-92, 2021.
EGU21-143 | vPICO presentations | GM12.8
Methodological proposal for the inventory and assessment of geoarchaeosites: Application to the middle Eure valley (Paris Basin, France).Théophile Piau, François Bétard, and Fabienne Dugast
The concept of “geoarchaeosite” has been introduced by Fouache & Rasse (2009) to identify archaeological sites located on a geomorphosite. In this work, we propose to use the expression in a larger sense as a contraction of geoarchaeological sites, i.e. sites of particular relevance for the understanding of past human-environment interactions. In our approach, the geomorphological and archaeological components of a site have the same level of importance, contrary to the classical approaches on geomorphosites which consider the archaeological interest of a site as an “additional” value. Although scientific literature replete with scattered case studies on geoarchaeosites, methodological guidelines are globally lacking to inventory and assess a collection of such geoarchaeosites for heritage conservation and/or tourism purposes.
The aim of this presentation is to propose an innovative and integrated methodology for the inventory and assessment of geoarchaeosites at a regional scale, with an example of application in the middle Eure Valley (Paris Basin, France). The first stage is the inventory which implies the identification and selection of potential geoarchaeosites considered as important sites worth being protected or managed within tourism or education projects. Two main criteria are involved in the selection process: the selected sites should be both representative of the regional geomorphological setting (spatial axis) and of the archaeological periods (temporal axis). The second stage is the assessment, itself divided into three main steps: (i) the assessment of the scientific value, calculated as the sum of the geomorphological and archaeological values; (ii) the assessment of the conservation need, including the calculation of a “vulnerability index” taking into account the intrinsic fragility of the site, the natural and human-induced threats, and the protection status; (iii) the assessment of the promotion potential, which combines the scientific and additional (cultural, aesthetic, ecological) values together with the visit conditions and potential uses for education and tourism.
In the middle Eure Valley which serves as a case study, the preliminary results derived from the proposed methodology provide a selection of geoarchaeosites with contrasted scientific values, from sites of international (e.g., Saint-Prest, Chaudon) and national rank (e.g., Chartres Cathedral and its historical quarry, the Aqueduc of Maintenon) to more confidential geoarchaeological sites of regional (e.g., megalithic site of Changé, Fort-Harrouard) and local interest (e.g., Shrine of Bû, Mormollins mill), with various degrees of vulnerability. Among the prospects that are emerging in the scope of promotional activities, is the interest of building a digital geoarchaeoheritage platform with a collaborative/participatory aim, associating Websemantics and geomatic technologies, in order to reinforce heritage ownership by local residents and stakeholders.
How to cite: Piau, T., Bétard, F., and Dugast, F.: Methodological proposal for the inventory and assessment of geoarchaeosites: Application to the middle Eure valley (Paris Basin, France)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-143, https://doi.org/10.5194/egusphere-egu21-143, 2021.
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The concept of “geoarchaeosite” has been introduced by Fouache & Rasse (2009) to identify archaeological sites located on a geomorphosite. In this work, we propose to use the expression in a larger sense as a contraction of geoarchaeological sites, i.e. sites of particular relevance for the understanding of past human-environment interactions. In our approach, the geomorphological and archaeological components of a site have the same level of importance, contrary to the classical approaches on geomorphosites which consider the archaeological interest of a site as an “additional” value. Although scientific literature replete with scattered case studies on geoarchaeosites, methodological guidelines are globally lacking to inventory and assess a collection of such geoarchaeosites for heritage conservation and/or tourism purposes.
The aim of this presentation is to propose an innovative and integrated methodology for the inventory and assessment of geoarchaeosites at a regional scale, with an example of application in the middle Eure Valley (Paris Basin, France). The first stage is the inventory which implies the identification and selection of potential geoarchaeosites considered as important sites worth being protected or managed within tourism or education projects. Two main criteria are involved in the selection process: the selected sites should be both representative of the regional geomorphological setting (spatial axis) and of the archaeological periods (temporal axis). The second stage is the assessment, itself divided into three main steps: (i) the assessment of the scientific value, calculated as the sum of the geomorphological and archaeological values; (ii) the assessment of the conservation need, including the calculation of a “vulnerability index” taking into account the intrinsic fragility of the site, the natural and human-induced threats, and the protection status; (iii) the assessment of the promotion potential, which combines the scientific and additional (cultural, aesthetic, ecological) values together with the visit conditions and potential uses for education and tourism.
In the middle Eure Valley which serves as a case study, the preliminary results derived from the proposed methodology provide a selection of geoarchaeosites with contrasted scientific values, from sites of international (e.g., Saint-Prest, Chaudon) and national rank (e.g., Chartres Cathedral and its historical quarry, the Aqueduc of Maintenon) to more confidential geoarchaeological sites of regional (e.g., megalithic site of Changé, Fort-Harrouard) and local interest (e.g., Shrine of Bû, Mormollins mill), with various degrees of vulnerability. Among the prospects that are emerging in the scope of promotional activities, is the interest of building a digital geoarchaeoheritage platform with a collaborative/participatory aim, associating Websemantics and geomatic technologies, in order to reinforce heritage ownership by local residents and stakeholders.
How to cite: Piau, T., Bétard, F., and Dugast, F.: Methodological proposal for the inventory and assessment of geoarchaeosites: Application to the middle Eure valley (Paris Basin, France)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-143, https://doi.org/10.5194/egusphere-egu21-143, 2021.
EGU21-253 | vPICO presentations | GM12.8
Assessing the ecological value of dynamic mountain geomorphositesJonathan Bussard and Elisa Giaccone
Over the last 15 years, the methodological proposals for assessing the heritage value of geomorphosites have been numerous and varied (Brilha, 2018). While some of the main criteria for assessing the geoscientific value, i.e. the interest for Earth sciences (rarity, representativeness, integrity), are mentioned in most methods, the criteria for assessing additional values (Reynard, 2005, 2009: aesthetic, ecological and cultural values) are much more heterogeneous (Mucivuna et al., 2019). There is particularly little discussion in the literature about the assessment of the ecological value of geomorphosites. Many case studies suggest to give a high score when “valuable” or “interesting” fauna and/or flora are observed, without explaining the link with a specific geomorphological landform or process. A few authors, such as Bollati et al. (2015), proposed to assess the “ecologic support role”, i.e. the impacts of geomorphological processes and landforms on vegetal and animal diversity or their contribution to ecosystem services. Despite these suggestions, there is still no detailed methodological proposal to assess the ecological value of geomorphosites based on clearly defined criteria.
The bi-directional relationship between geomorphology and biological elements of nature has been the subject of many publications and led to the development of the biogeomorphology, defined as the study of interactions between geomorphological processes and structures and living organisms, like plants, animals and microorganisms (e.g. Knox, 1972; Butler, 1995; Gorbushina, 2007). Compared to other categories of geosites, the activity of processes responsible for their formation and evolution is often a core characteristic of geomorphosites (Reynard, 2009; Pelfini and Bollati, 2014; Coratza and Hobléa, 2018) and this dynamic can have a strong influence on vegetation. This is especially the case in mountain environment, where dynamic geomorphological parameters can have various effects on vegetation distribution and community composition (Giaccone et al., 2019).
The aim of this communication is to clarify and objectivize the assessment of the ecological value of dynamic mountain geomorphosites. A complete evaluation of the ecological value should take into account the impacts of geomorphological processes and landforms on vegetation and fauna diversity. Here we propose to look further into the question of the influence of dynamic mountain geomorphosites on vegetation diversity. We suggest the definition of three criteria – disturbances, microhabitats, types of substrates – that should be used for a more accurate and objective assessment of the ecological value of this category of geomorphosites, with a particular focus on the links between geomorphology and vegetal biodiversity. We finally apply these criteria for the assessment of the ecological value of four mountain geomorphosites situated in the Vallon de Nant (Swiss Alps): a rock glacier, a moraine complex from the Younger Dryas, a side and frontal moraine from the Little Ice Age and a zone of scree slopes and avalanche deposits.
How to cite: Bussard, J. and Giaccone, E.: Assessing the ecological value of dynamic mountain geomorphosites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-253, https://doi.org/10.5194/egusphere-egu21-253, 2021.
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We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Over the last 15 years, the methodological proposals for assessing the heritage value of geomorphosites have been numerous and varied (Brilha, 2018). While some of the main criteria for assessing the geoscientific value, i.e. the interest for Earth sciences (rarity, representativeness, integrity), are mentioned in most methods, the criteria for assessing additional values (Reynard, 2005, 2009: aesthetic, ecological and cultural values) are much more heterogeneous (Mucivuna et al., 2019). There is particularly little discussion in the literature about the assessment of the ecological value of geomorphosites. Many case studies suggest to give a high score when “valuable” or “interesting” fauna and/or flora are observed, without explaining the link with a specific geomorphological landform or process. A few authors, such as Bollati et al. (2015), proposed to assess the “ecologic support role”, i.e. the impacts of geomorphological processes and landforms on vegetal and animal diversity or their contribution to ecosystem services. Despite these suggestions, there is still no detailed methodological proposal to assess the ecological value of geomorphosites based on clearly defined criteria.
The bi-directional relationship between geomorphology and biological elements of nature has been the subject of many publications and led to the development of the biogeomorphology, defined as the study of interactions between geomorphological processes and structures and living organisms, like plants, animals and microorganisms (e.g. Knox, 1972; Butler, 1995; Gorbushina, 2007). Compared to other categories of geosites, the activity of processes responsible for their formation and evolution is often a core characteristic of geomorphosites (Reynard, 2009; Pelfini and Bollati, 2014; Coratza and Hobléa, 2018) and this dynamic can have a strong influence on vegetation. This is especially the case in mountain environment, where dynamic geomorphological parameters can have various effects on vegetation distribution and community composition (Giaccone et al., 2019).
The aim of this communication is to clarify and objectivize the assessment of the ecological value of dynamic mountain geomorphosites. A complete evaluation of the ecological value should take into account the impacts of geomorphological processes and landforms on vegetation and fauna diversity. Here we propose to look further into the question of the influence of dynamic mountain geomorphosites on vegetation diversity. We suggest the definition of three criteria – disturbances, microhabitats, types of substrates – that should be used for a more accurate and objective assessment of the ecological value of this category of geomorphosites, with a particular focus on the links between geomorphology and vegetal biodiversity. We finally apply these criteria for the assessment of the ecological value of four mountain geomorphosites situated in the Vallon de Nant (Swiss Alps): a rock glacier, a moraine complex from the Younger Dryas, a side and frontal moraine from the Little Ice Age and a zone of scree slopes and avalanche deposits.
How to cite: Bussard, J. and Giaccone, E.: Assessing the ecological value of dynamic mountain geomorphosites, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-253, https://doi.org/10.5194/egusphere-egu21-253, 2021.
EGU21-2610 | vPICO presentations | GM12.8
Inventory and assessment of geoheritage in the Liguria region (Italy) within the framework of land management and developmentAndrea Ferrando, Francesco Faccini, Flavio Poggi, and Paola Coratza
Geoheritage is an important natural resource that can represent a link between geosciences and the wider public, and all over the world initiatives have emerged to protect, value and enhance it. Therefore, geoheritage assessment is a fundamental step in choosing a correct land management strategy. The Liguria Region in Northern Italy is characterized by a wide geological and geomorphological variety, encompassing an important and valuable geoheritage. In Liguria, a regional law (L.R. 39/2009) protect and enhance geodiversity and geosites, establishing the Regional Inventory of Geosites. However, an approved official inventory is still lacking. In the present work a first reasoned inventory of 120 geosites is proposed for the Liguria Region, based on field surveys and literature review. A quantitative assessment of the value and the degradation risk was carried out. The value assessment takes into account the scientific value, the additional (aesthetic and cultural) value and the potential for use value; these three values are combined to obtain a total value (Q). Nine geosites obtain a Q value higher than 4: these geosites are among the best known of the Liguria region and are already exploited for tourism, such as the Palmaria and Tino islands, the Portovenere cliffs, the Gambatesa Mine, the Mt. Ramaceto sandstones, the Fascette Gorge, the S. Bernardino karst plateau, the Capo Mortola nummulitic limestones, the ophiolite outcrops of the Beigua Geopark and Framura. The degradation risk assessment takes into account both fragility and vulnerability of the geosites. The geosites selected and assessed in the present research will be implemented in the Regional Inventory of Geosites. Moreover, the results provides the necessary ground for interested parties to take actions for the implementation of effective regional geoconservation strategy or environmental management plan.
How to cite: Ferrando, A., Faccini, F., Poggi, F., and Coratza, P.: Inventory and assessment of geoheritage in the Liguria region (Italy) within the framework of land management and development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2610, https://doi.org/10.5194/egusphere-egu21-2610, 2021.
Geoheritage is an important natural resource that can represent a link between geosciences and the wider public, and all over the world initiatives have emerged to protect, value and enhance it. Therefore, geoheritage assessment is a fundamental step in choosing a correct land management strategy. The Liguria Region in Northern Italy is characterized by a wide geological and geomorphological variety, encompassing an important and valuable geoheritage. In Liguria, a regional law (L.R. 39/2009) protect and enhance geodiversity and geosites, establishing the Regional Inventory of Geosites. However, an approved official inventory is still lacking. In the present work a first reasoned inventory of 120 geosites is proposed for the Liguria Region, based on field surveys and literature review. A quantitative assessment of the value and the degradation risk was carried out. The value assessment takes into account the scientific value, the additional (aesthetic and cultural) value and the potential for use value; these three values are combined to obtain a total value (Q). Nine geosites obtain a Q value higher than 4: these geosites are among the best known of the Liguria region and are already exploited for tourism, such as the Palmaria and Tino islands, the Portovenere cliffs, the Gambatesa Mine, the Mt. Ramaceto sandstones, the Fascette Gorge, the S. Bernardino karst plateau, the Capo Mortola nummulitic limestones, the ophiolite outcrops of the Beigua Geopark and Framura. The degradation risk assessment takes into account both fragility and vulnerability of the geosites. The geosites selected and assessed in the present research will be implemented in the Regional Inventory of Geosites. Moreover, the results provides the necessary ground for interested parties to take actions for the implementation of effective regional geoconservation strategy or environmental management plan.
How to cite: Ferrando, A., Faccini, F., Poggi, F., and Coratza, P.: Inventory and assessment of geoheritage in the Liguria region (Italy) within the framework of land management and development, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2610, https://doi.org/10.5194/egusphere-egu21-2610, 2021.
EGU21-4467 | vPICO presentations | GM12.8
Sukil River valley — a natural geological laboratoryMariia Oliinyk, Ihor Bubniak, Mykola Bihun, and Yuriy Vikhot
We present a number of geological objects located along the valley of the Sukil River, which flows within the Ivano-Frankivsk Region in the west of Ukraine. The river crosses a number of structures of the Skyba nappe and the Inner unit of the Ukrainian Carpathian foredeep, which belong to the orogen of the Outer Ukrainian Carpathians. The Outer Ukrainian Carpathians were formed as a result of alpine tectogenesis. They are composed mainly of flysch deposited in Cretaceous-Neogene basins. The foredeep is filled with sediments known as molasses.
The research objects allow to study many aspects of geology —sedimentation, fold formation, fault formation, formation of mountain systems.
Many objects in the Sukil River valley are currently being studied using the latest technologies — digital photogrammetry and terrestrial laser scanning to create virtual geological outcrops.
Unique samples of Oligocene fish remnants collected during field research are stored in the Natural History Museum of the Precarpathian Professional College of Forestry and Tourism in Bolekhiv which is located on the Sukil River. Here there are also great druses of gypsum from a local quarry. In the same town are the remains of a saltworks which was one of the oldest in the region.
Objects located in the Sukil River valley have not only scientific but also aesthetic significance. The folds from Bukivets are the object of the international geotourism route "Geocarpathians".
How to cite: Oliinyk, M., Bubniak, I., Bihun, M., and Vikhot, Y.: Sukil River valley — a natural geological laboratory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4467, https://doi.org/10.5194/egusphere-egu21-4467, 2021.
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We present a number of geological objects located along the valley of the Sukil River, which flows within the Ivano-Frankivsk Region in the west of Ukraine. The river crosses a number of structures of the Skyba nappe and the Inner unit of the Ukrainian Carpathian foredeep, which belong to the orogen of the Outer Ukrainian Carpathians. The Outer Ukrainian Carpathians were formed as a result of alpine tectogenesis. They are composed mainly of flysch deposited in Cretaceous-Neogene basins. The foredeep is filled with sediments known as molasses.
The research objects allow to study many aspects of geology —sedimentation, fold formation, fault formation, formation of mountain systems.
Many objects in the Sukil River valley are currently being studied using the latest technologies — digital photogrammetry and terrestrial laser scanning to create virtual geological outcrops.
Unique samples of Oligocene fish remnants collected during field research are stored in the Natural History Museum of the Precarpathian Professional College of Forestry and Tourism in Bolekhiv which is located on the Sukil River. Here there are also great druses of gypsum from a local quarry. In the same town are the remains of a saltworks which was one of the oldest in the region.
Objects located in the Sukil River valley have not only scientific but also aesthetic significance. The folds from Bukivets are the object of the international geotourism route "Geocarpathians".
How to cite: Oliinyk, M., Bubniak, I., Bihun, M., and Vikhot, Y.: Sukil River valley — a natural geological laboratory, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4467, https://doi.org/10.5194/egusphere-egu21-4467, 2021.
EGU21-6650 | vPICO presentations | GM12.8 | Highlight
The diverse visages of Geoheritage in Mexico City: Knowing your place, knowing your risksMarie-Noelle Guilbaud, Naara López Velásquez, José Alfredo Járquin Rojas, María del Pilar Ortega-Larrocea, Silke Cram, and Benjamin van Wyk de Vries
Geological elements in cities are usually damaged and invisible to their inhabitants, despite the wide range of benefits they provide to them. In particular, they offer them an opportunity to learn about their geological setting (= sense of place) and be aware of associated risks (= sense of risk). Such geoheritage comes in different forms that ought to be identified and described precisely in order to be preserved and used. The gigantic capital city of Mexico is settled in a paleolake basin embedded in a diverse volcanic landscape. City inhabitants face numerous hazards (floods, landslides, debris flows, subsidence, earthquakes, drought, fires) that create high risks with combined natural and anthropogenic causes due to uncontrolled city growth. The geoheritage of the city is mostly formed by monogenetic (one-event) volcanoes that are an important resource for geoconservation and geoeducation. We present two case studies that were investigated by students near their homes, which was a strategy employed during the COVID-19 pandemic to allow them to undertake field work. The first study area is a popular neighborhood (Lomas de Padierna) that was rooted in the 1970s on basaltic lavas from the ca. AD200 Xitle cone. In this highly urbanized area, the geological nature is only visible as sparse vertical outcrops along streets and small surface exposures in private gardens and road central reservations. Such sites are seldom maintained by the locals who rarely recognize their value. Debris flows during rain storms cause a chronic hazard. The second area consists of a chain of several cones, a dome and a tuff ring (Sierra Santa Catarina) located in the southeastern part of the basin, that conserves elements of the native fauna and flora. Depicted in the great landscape paintings of the Mexico basin made in the 19th century, mining activities and illegal settlements have severely degraded this site since the 1970s, even after the creation of a protected area in 1994 and a conservation area in 2003. Enhanced cone erosion causes frequent landslides affecting settlements. Data on the age and eruptive style of these volcanoes is surprisingly limited, given their importance for hazard assessment.
This work reveals the diverse visages of geoheritage in a large city, showing their low level of scientific knowledge and public appreciation, which account for their pronounced degree of degradation. Hence, the memory of past geological events, awareness of impending hazards, and vital mineral and organic resources are disappearing quickly, further increasing the risks faced by the city. The vulnerability of people to hazards can be linked to their poor knowledge of their environment. The dissemination of information on local geosites may be highly valuable to raise environmental awareness and reduce risks. In this respect, we plan to make and distribute leaflets to local schools and community centers.
How to cite: Guilbaud, M.-N., López Velásquez, N., Járquin Rojas, J. A., Ortega-Larrocea, M. P., Cram, S., and van Wyk de Vries, B.: The diverse visages of Geoheritage in Mexico City: Knowing your place, knowing your risks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6650, https://doi.org/10.5194/egusphere-egu21-6650, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Geological elements in cities are usually damaged and invisible to their inhabitants, despite the wide range of benefits they provide to them. In particular, they offer them an opportunity to learn about their geological setting (= sense of place) and be aware of associated risks (= sense of risk). Such geoheritage comes in different forms that ought to be identified and described precisely in order to be preserved and used. The gigantic capital city of Mexico is settled in a paleolake basin embedded in a diverse volcanic landscape. City inhabitants face numerous hazards (floods, landslides, debris flows, subsidence, earthquakes, drought, fires) that create high risks with combined natural and anthropogenic causes due to uncontrolled city growth. The geoheritage of the city is mostly formed by monogenetic (one-event) volcanoes that are an important resource for geoconservation and geoeducation. We present two case studies that were investigated by students near their homes, which was a strategy employed during the COVID-19 pandemic to allow them to undertake field work. The first study area is a popular neighborhood (Lomas de Padierna) that was rooted in the 1970s on basaltic lavas from the ca. AD200 Xitle cone. In this highly urbanized area, the geological nature is only visible as sparse vertical outcrops along streets and small surface exposures in private gardens and road central reservations. Such sites are seldom maintained by the locals who rarely recognize their value. Debris flows during rain storms cause a chronic hazard. The second area consists of a chain of several cones, a dome and a tuff ring (Sierra Santa Catarina) located in the southeastern part of the basin, that conserves elements of the native fauna and flora. Depicted in the great landscape paintings of the Mexico basin made in the 19th century, mining activities and illegal settlements have severely degraded this site since the 1970s, even after the creation of a protected area in 1994 and a conservation area in 2003. Enhanced cone erosion causes frequent landslides affecting settlements. Data on the age and eruptive style of these volcanoes is surprisingly limited, given their importance for hazard assessment.
This work reveals the diverse visages of geoheritage in a large city, showing their low level of scientific knowledge and public appreciation, which account for their pronounced degree of degradation. Hence, the memory of past geological events, awareness of impending hazards, and vital mineral and organic resources are disappearing quickly, further increasing the risks faced by the city. The vulnerability of people to hazards can be linked to their poor knowledge of their environment. The dissemination of information on local geosites may be highly valuable to raise environmental awareness and reduce risks. In this respect, we plan to make and distribute leaflets to local schools and community centers.
How to cite: Guilbaud, M.-N., López Velásquez, N., Járquin Rojas, J. A., Ortega-Larrocea, M. P., Cram, S., and van Wyk de Vries, B.: The diverse visages of Geoheritage in Mexico City: Knowing your place, knowing your risks, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6650, https://doi.org/10.5194/egusphere-egu21-6650, 2021.
EGU21-6658 | vPICO presentations | GM12.8
Green and golden obsidian of ‘Cerro de Las Navajas’, Hidalgo (Mexico): geoarchaeological heritage that deserves international recognitionMiguel A. Cruz-Pérez, Carles Canet, Alejandro Pastrana, Luis Carcavilla, Erika Salgado-Martínez, and Eduardo J. García-Alonso
The «Cerro de Las Navajas Obsidian» is a rock within the Comarca Minera, Hidalgo UNESCO Global Geopark, Mexico, that possesses outstanding archaeological, cultural and geological value. It exhibits a unique green-golden macroscopic hue and was exploited and traded since ca. 250 BC, by successive Mesoamerican cultures and until early Colonial times —ultimately recording the transition to a steel-based society. It is the largest deposit of its kind and the longest historical exploited site in the continent. We argue here the potential of this particular obsidian for a heritage designation that highlights its global significance; synergies derived from an international recognition may offer the chance (a) to put in value the multi-dimensional geoheritage of this obsidian, (b) to strengthen the sense of belonging among local community, (c) to require authorities to regulate obsidian mining and commercialization, under fair trade terms and compatible with conservation, research and responsible tourism, (d) to support further research on archaeology and cultural heritage linking geosciences with other disciplines, and (e) to contribute to UNESCO Global Geoparks program’s aims seeking local development and sustainability. The two last expected achievements would be relevant given the lack of legal advisory role of geoparks in geoheritage management in Mexico and its geoconservation community.
How to cite: Cruz-Pérez, M. A., Canet, C., Pastrana, A., Carcavilla, L., Salgado-Martínez, E., and García-Alonso, E. J.: Green and golden obsidian of ‘Cerro de Las Navajas’, Hidalgo (Mexico): geoarchaeological heritage that deserves international recognition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6658, https://doi.org/10.5194/egusphere-egu21-6658, 2021.
The «Cerro de Las Navajas Obsidian» is a rock within the Comarca Minera, Hidalgo UNESCO Global Geopark, Mexico, that possesses outstanding archaeological, cultural and geological value. It exhibits a unique green-golden macroscopic hue and was exploited and traded since ca. 250 BC, by successive Mesoamerican cultures and until early Colonial times —ultimately recording the transition to a steel-based society. It is the largest deposit of its kind and the longest historical exploited site in the continent. We argue here the potential of this particular obsidian for a heritage designation that highlights its global significance; synergies derived from an international recognition may offer the chance (a) to put in value the multi-dimensional geoheritage of this obsidian, (b) to strengthen the sense of belonging among local community, (c) to require authorities to regulate obsidian mining and commercialization, under fair trade terms and compatible with conservation, research and responsible tourism, (d) to support further research on archaeology and cultural heritage linking geosciences with other disciplines, and (e) to contribute to UNESCO Global Geoparks program’s aims seeking local development and sustainability. The two last expected achievements would be relevant given the lack of legal advisory role of geoparks in geoheritage management in Mexico and its geoconservation community.
How to cite: Cruz-Pérez, M. A., Canet, C., Pastrana, A., Carcavilla, L., Salgado-Martínez, E., and García-Alonso, E. J.: Green and golden obsidian of ‘Cerro de Las Navajas’, Hidalgo (Mexico): geoarchaeological heritage that deserves international recognition, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-6658, https://doi.org/10.5194/egusphere-egu21-6658, 2021.
EGU21-8355 | vPICO presentations | GM12.8
Geosite assessment in Arequipa City – Peru: UNESCO IGCP 692 project 'Geoheritage for Geohazard Resilience'Carla Lili Arias Salazar, Nélida Manrique, Rigoberto Aguilar, and Benjamin van Wyk de Vries
Arequipa, the second most populated city located in the South of Peru, is full of history, culture and is a UNESCO World Heritage site. Its natural attractions and geological diversity stand out, like the Colca and Andagua UNESCO Global Geopark, as well as geosites within the city. This provides a basis for improving the population's environmental awareness and resilience, a process that partly starts with geosite inventorying, used in socio-economic exchange with the population. For the geosite work several methods were used from the early Cendrero (1996) to most recent Brilha (2016). As a first stage, potential geosites were field identified, and we established their representativeness, integrity, rarity, scientific knowledge level and geological value. Six major potential geosites were identified: 1) Sillar quarries, 2) Rio Chili valley, 3) Misti and Chachani volcanoes viewpoint, 4) Nicholson volcano, 5) Ccapua monogenetic volcanoes, Yura Viejo, Uyupampa and 6) Domo el Volcancillo. Once identified and judged suitable for potential use and protection, the six sites were qualitatively evaluated for intrinsic value, potential for use and need for protection, thus completing more detailed information on each one. In this second stage, the process of quantifying the value and relevance establishing a ranking. The Brilha (2005) methodology was used to classify geosites as local - regional and national - international interest, The Sillar being of national - international scope, while the other geosites are of local to regional scope. To rank geosites according to their scientific value, educational potential use, tourism potential use and the risk of degradation, the Brilha (2016) methodology was used. Each site was evaluated independently, since the value of the geosite is not directly related to its potential for use or vulnerability. The ranking for scientific value and educational and tourist use is different and the Sillar and Ccapua have high risk of degradation, while the others moderate risk. We also classified each site for its natural risk to inhabitants, users and visitors, making a preliminary safety plan for each site. The process ends with a classification seeking to provide a legal basis for geoheritage management and protection. Conservation plans take into account the degradation risk to propose strategies with include safety. Community involvement was a first step, with the Sillar site users partly initiating and directing our work. We all see the geoheritage as a tool to publicize both geology and associated activities in an innovative way through geotourism and economic sustainability. Risk is managed with geosites and the benefits and dangers related to the Misti and Chachani volcanoes communicated. The process continues with constant monitoring of geosites. This aims to empower local scientists and residents, because it highlights the geological heritage, and generates "tools" for education and promote resilient communities in the face of geological hazards; in addition, diversify the alternatives for geotourism. It is part of the UNESCO IGCP Geoheritage for Resilience, project 692.
How to cite: Arias Salazar, C. L., Manrique, N., Aguilar, R., and van Wyk de Vries, B.: Geosite assessment in Arequipa City – Peru: UNESCO IGCP 692 project 'Geoheritage for Geohazard Resilience' , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8355, https://doi.org/10.5194/egusphere-egu21-8355, 2021.
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Arequipa, the second most populated city located in the South of Peru, is full of history, culture and is a UNESCO World Heritage site. Its natural attractions and geological diversity stand out, like the Colca and Andagua UNESCO Global Geopark, as well as geosites within the city. This provides a basis for improving the population's environmental awareness and resilience, a process that partly starts with geosite inventorying, used in socio-economic exchange with the population. For the geosite work several methods were used from the early Cendrero (1996) to most recent Brilha (2016). As a first stage, potential geosites were field identified, and we established their representativeness, integrity, rarity, scientific knowledge level and geological value. Six major potential geosites were identified: 1) Sillar quarries, 2) Rio Chili valley, 3) Misti and Chachani volcanoes viewpoint, 4) Nicholson volcano, 5) Ccapua monogenetic volcanoes, Yura Viejo, Uyupampa and 6) Domo el Volcancillo. Once identified and judged suitable for potential use and protection, the six sites were qualitatively evaluated for intrinsic value, potential for use and need for protection, thus completing more detailed information on each one. In this second stage, the process of quantifying the value and relevance establishing a ranking. The Brilha (2005) methodology was used to classify geosites as local - regional and national - international interest, The Sillar being of national - international scope, while the other geosites are of local to regional scope. To rank geosites according to their scientific value, educational potential use, tourism potential use and the risk of degradation, the Brilha (2016) methodology was used. Each site was evaluated independently, since the value of the geosite is not directly related to its potential for use or vulnerability. The ranking for scientific value and educational and tourist use is different and the Sillar and Ccapua have high risk of degradation, while the others moderate risk. We also classified each site for its natural risk to inhabitants, users and visitors, making a preliminary safety plan for each site. The process ends with a classification seeking to provide a legal basis for geoheritage management and protection. Conservation plans take into account the degradation risk to propose strategies with include safety. Community involvement was a first step, with the Sillar site users partly initiating and directing our work. We all see the geoheritage as a tool to publicize both geology and associated activities in an innovative way through geotourism and economic sustainability. Risk is managed with geosites and the benefits and dangers related to the Misti and Chachani volcanoes communicated. The process continues with constant monitoring of geosites. This aims to empower local scientists and residents, because it highlights the geological heritage, and generates "tools" for education and promote resilient communities in the face of geological hazards; in addition, diversify the alternatives for geotourism. It is part of the UNESCO IGCP Geoheritage for Resilience, project 692.
How to cite: Arias Salazar, C. L., Manrique, N., Aguilar, R., and van Wyk de Vries, B.: Geosite assessment in Arequipa City – Peru: UNESCO IGCP 692 project 'Geoheritage for Geohazard Resilience' , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8355, https://doi.org/10.5194/egusphere-egu21-8355, 2021.
EGU21-9054 | vPICO presentations | GM12.8 | Highlight
The geosite of Pertosa-Auletta cave: an educational journey into the underworldRosangela Addesso, Simona Cafaro, Filomena Papaleo, Rosanna Alaggio, Francescantonio D'Orilia, and Mariana Amato
The Pertosa-Auletta cave is a complex karst system of southern Italy included in the “Cilento, Vallo di Diano and Alburni” UNESCO Global Geopark as a focal geosite for the important geological heritage, the experience in geoturism management and the cultural, didactic and recreational appeal. Representing one of the most important perennial springs of the Alburni massif, since the early 1900s, this cave has played a key role within the territory of the Alburni, Cilento and Vallo di Diano National Park, so the complex welcomes thousands of visitors from all over the world every year. The site is managed by the MIdA Foundation (Integrated Environmental Museum) with the goal of education on environmental and landscape value of the caves. Geological peculiarities, historical-cultural characteristics, as well as environmental protection of the geosite are the main subjects of MIdA actions targeted to the local community and geotouristis. Thanks to the cooperation with several national and international research institutes, the Foundation contributes to the production of new knowledge and to the dissemination of results through its organization. In addition to the cave, the MidA system includes two Museums: the Speleo-Archaeological Museum and the Soil Museums, where visitors are led on a journey into the underworld. Tours and practical activities focus on multidisciplinary information about carsism, genesis of the Pertosa-Auletta cave, archeological findings in the site. A special effort is devoted to soils, precious sources of underground treasures, and ecosystem processes regulating life on the planet. The tour starts from the rocks and their properties and continues through habitats for the growth of numerous lifeforms linked to their structure and chemical composition. The complex relationshis of below-ground environments with water and other earth features are presented. The Pertosa-Auletta cave offers a good example of how people can understand the importance of a complex karst system. Inside the cave the Negro, an underground river flows and it plays an important role in the karst complex. Water and sediments of the Negro have preserved an archeological settlement on piles dating back to the Bronze Age. The presence of piles inside a cave represents one of the most characteristic features of this karst complex and is an example of different uses of the cave through the ages. During the Bronze Age, the Pertosa-Auletta cave was used for both a cultural and a living purpose. In Classical and Medieval times, the complex became a shrine, dedicated first to pagan gods related to fertility and then to the Archangel Michael. Findings are shown in the MIdA Speleo-Archeological Museum along with multimedia displays and reconstructions of the Prehistoric pile. The Pertosa-Auletta cave is also a research site on karst phenomena, hydrology and speleo-biology with important findings on vermiculations, where the evidence of microbial activity supports the possible involvement of biogenic processes in vermiculation development in karst caves.
How to cite: Addesso, R., Cafaro, S., Papaleo, F., Alaggio, R., D'Orilia, F., and Amato, M.: The geosite of Pertosa-Auletta cave: an educational journey into the underworld, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9054, https://doi.org/10.5194/egusphere-egu21-9054, 2021.
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Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The Pertosa-Auletta cave is a complex karst system of southern Italy included in the “Cilento, Vallo di Diano and Alburni” UNESCO Global Geopark as a focal geosite for the important geological heritage, the experience in geoturism management and the cultural, didactic and recreational appeal. Representing one of the most important perennial springs of the Alburni massif, since the early 1900s, this cave has played a key role within the territory of the Alburni, Cilento and Vallo di Diano National Park, so the complex welcomes thousands of visitors from all over the world every year. The site is managed by the MIdA Foundation (Integrated Environmental Museum) with the goal of education on environmental and landscape value of the caves. Geological peculiarities, historical-cultural characteristics, as well as environmental protection of the geosite are the main subjects of MIdA actions targeted to the local community and geotouristis. Thanks to the cooperation with several national and international research institutes, the Foundation contributes to the production of new knowledge and to the dissemination of results through its organization. In addition to the cave, the MidA system includes two Museums: the Speleo-Archaeological Museum and the Soil Museums, where visitors are led on a journey into the underworld. Tours and practical activities focus on multidisciplinary information about carsism, genesis of the Pertosa-Auletta cave, archeological findings in the site. A special effort is devoted to soils, precious sources of underground treasures, and ecosystem processes regulating life on the planet. The tour starts from the rocks and their properties and continues through habitats for the growth of numerous lifeforms linked to their structure and chemical composition. The complex relationshis of below-ground environments with water and other earth features are presented. The Pertosa-Auletta cave offers a good example of how people can understand the importance of a complex karst system. Inside the cave the Negro, an underground river flows and it plays an important role in the karst complex. Water and sediments of the Negro have preserved an archeological settlement on piles dating back to the Bronze Age. The presence of piles inside a cave represents one of the most characteristic features of this karst complex and is an example of different uses of the cave through the ages. During the Bronze Age, the Pertosa-Auletta cave was used for both a cultural and a living purpose. In Classical and Medieval times, the complex became a shrine, dedicated first to pagan gods related to fertility and then to the Archangel Michael. Findings are shown in the MIdA Speleo-Archeological Museum along with multimedia displays and reconstructions of the Prehistoric pile. The Pertosa-Auletta cave is also a research site on karst phenomena, hydrology and speleo-biology with important findings on vermiculations, where the evidence of microbial activity supports the possible involvement of biogenic processes in vermiculation development in karst caves.
How to cite: Addesso, R., Cafaro, S., Papaleo, F., Alaggio, R., D'Orilia, F., and Amato, M.: The geosite of Pertosa-Auletta cave: an educational journey into the underworld, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9054, https://doi.org/10.5194/egusphere-egu21-9054, 2021.
EGU21-5403 | vPICO presentations | GM12.8
Enough is enough… Can various legislative tools cause ambiguities when applied in a single area? (Case study: Hády Hill, Brno, Czech Republic)Lucie Kubalíková
Establishing legal protection to a geosite (or geodiversity site) is considered one of the key tools of how to conserve its values and how to avoid degradation and devastation. The proper management measures (usually included in care plans or other planning and strategic documentation) then help to balance the conservation needs and sustainable use of the sites and allow to gain public finances for these purposes.
In the Czech Republic, nature conservation is anchored in Act n. 114/1992 Coll. (Nature Conservation Act) which defines several levels of protected areas that can be applied also on geoheritage. However, there are other legislative tools that protect other entities (e.g. agricultural land, water, or forests). The special relationship to geodiversity has Act n. 44/1988 Coll. (Mining Act) which aims to protect the mineral deposits including their deposit areas. Various tools for the protection applied to a single area can cause ambiguities because every protected entity has different management and limitations.
This is the case of Hády Hill, an area situated in the outskirts of Brno, the second-largest city in the Czech Republic. The area is important from the Earth Science point of view (tectonics, paleontology, geomorphology, stratigraphy, hydrogeology) and has high ecological and cultural values, e.g. occurrence of endangered species linked to the subsoil, remnants of old landscape structures (orchards, pastures), historical mining, use of the building material for Brno monuments. Earth-science and ecological values are protected according to Nature Conservation Act within one National Nature Reserve, two Nature Monuments, and four Important Landscape Elements and partly included in Special Area of Conservation (according to the Habitats Directive - Council Directive 92/43/EEC). Moreover, due to the occurrence of quality limestone, which was extracted from the Middle Ages up to the end of the 20th Century, the part of the study area is declared as a reserved mineral deposit and protected deposit area (according to Mining Act). All these areas mutually overlap.
Concerning geoheritage, some phenomena still have no degree of protection, but they are included in the Database of Geological Localities (kept by the Czech Geological Survey) and proposed for legal protection.
Last but not least, the site undergoes tourist and recreational pressure which is continuously increasing due to the COVID-19 situation (lack of indoor possibilities of how to spend the free time).
To find the balance between the various conservation needs, management measures, limitations, tourist/recreation pressure, and urban development, it was necessary to do a complex analysis of the various types of protected areas and their values. Based on the SWOT analysis and Risk Assessment, the main threats, risks, and possible conflicts of interest were identified and assessed. Then, specific proposals and possible solutions were designed with an emphasis on effective geoconservation (e.g. declaration of the new or enlarging the currently protected areas), development of sustainable forms of tourism, and future rational use of an area (e.g. via volunteer activities or participative planning of management).
How to cite: Kubalíková, L.: Enough is enough… Can various legislative tools cause ambiguities when applied in a single area? (Case study: Hády Hill, Brno, Czech Republic), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5403, https://doi.org/10.5194/egusphere-egu21-5403, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Establishing legal protection to a geosite (or geodiversity site) is considered one of the key tools of how to conserve its values and how to avoid degradation and devastation. The proper management measures (usually included in care plans or other planning and strategic documentation) then help to balance the conservation needs and sustainable use of the sites and allow to gain public finances for these purposes.
In the Czech Republic, nature conservation is anchored in Act n. 114/1992 Coll. (Nature Conservation Act) which defines several levels of protected areas that can be applied also on geoheritage. However, there are other legislative tools that protect other entities (e.g. agricultural land, water, or forests). The special relationship to geodiversity has Act n. 44/1988 Coll. (Mining Act) which aims to protect the mineral deposits including their deposit areas. Various tools for the protection applied to a single area can cause ambiguities because every protected entity has different management and limitations.
This is the case of Hády Hill, an area situated in the outskirts of Brno, the second-largest city in the Czech Republic. The area is important from the Earth Science point of view (tectonics, paleontology, geomorphology, stratigraphy, hydrogeology) and has high ecological and cultural values, e.g. occurrence of endangered species linked to the subsoil, remnants of old landscape structures (orchards, pastures), historical mining, use of the building material for Brno monuments. Earth-science and ecological values are protected according to Nature Conservation Act within one National Nature Reserve, two Nature Monuments, and four Important Landscape Elements and partly included in Special Area of Conservation (according to the Habitats Directive - Council Directive 92/43/EEC). Moreover, due to the occurrence of quality limestone, which was extracted from the Middle Ages up to the end of the 20th Century, the part of the study area is declared as a reserved mineral deposit and protected deposit area (according to Mining Act). All these areas mutually overlap.
Concerning geoheritage, some phenomena still have no degree of protection, but they are included in the Database of Geological Localities (kept by the Czech Geological Survey) and proposed for legal protection.
Last but not least, the site undergoes tourist and recreational pressure which is continuously increasing due to the COVID-19 situation (lack of indoor possibilities of how to spend the free time).
To find the balance between the various conservation needs, management measures, limitations, tourist/recreation pressure, and urban development, it was necessary to do a complex analysis of the various types of protected areas and their values. Based on the SWOT analysis and Risk Assessment, the main threats, risks, and possible conflicts of interest were identified and assessed. Then, specific proposals and possible solutions were designed with an emphasis on effective geoconservation (e.g. declaration of the new or enlarging the currently protected areas), development of sustainable forms of tourism, and future rational use of an area (e.g. via volunteer activities or participative planning of management).
How to cite: Kubalíková, L.: Enough is enough… Can various legislative tools cause ambiguities when applied in a single area? (Case study: Hády Hill, Brno, Czech Republic), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5403, https://doi.org/10.5194/egusphere-egu21-5403, 2021.
EGU21-7145 | vPICO presentations | GM12.8
The Puy de Dôme: Natural or Anthropogenic? Understanding, managing and protecting an original landscape in a UNESCO World Heritage siteBenjamin van Wyk de Vries, Márton Pál, Gáspár Albert, Fanni Vörös, Pablo Grosse, and Emmanuel Delage
Humans are part of nature, so natural landscapes can contain human impacts. The limit of this natural anthropomorphic influence, where landscape stops being natural, is not defined clearly, but major infrastructure, urbanization etc. are clearly non-natural elements. When a natural feature becomes important for humans, such as the iconic Puy de Dôme volcano in central France, it tends to attract human modification. The Puy de Dôme was a Druidic and Roman sacred site, with added temples and paths. Yet, outside these, the majority of the mountain remained in a natural state, evolving by erosion, slope movement, and accumulating debris on its lower flanks. The natural state can still be seen in the detailed morphometry of its flanks. Since the turn of the 20th century, increased human activity has further modified the site, with the construction of a spiral cog railway track, and infrastructure: restaurants, observatories, military and communication buildings, including the iconic spike – that inhabitants are so attached to. Despite this increased activity, the essential natural values of the mountain have been mostly maintained, although the spiral railway track has cut / modified the natural drainage to some extent. With UNESCO World Heritage inscription in 2018, visitation is on the increase, and with more visitors, further pressure has been seen. Occasional debris flows and landslides have also become newsworthy events, impacting the railway operation. New slope stability plans have been drawn up for the cog railway and the footpaths, which have included large scale bolting of outcrops, wire meshing and rock removal. These have been implemented only very partially due to opposition from ecology and geoheritage actors.
To provide a clear picture of the natural state of the Puy de Dôme and to guide natural protection and risk management, a full geomorphological and morphometric analysis is needed. This abstract gives the first results of this work, presenting the geomorphology and morphometry, including a geomorphon and shape analysis, and 3-D Virtual Reality LiDAR topography. The resulting information allows us to determine the state of 'naturality' of the Puy de Dôme and establish the natural system and determine its anthropogenic influences. The volcano, since its eruption 11,000 years ago, has been slowly evolving under different climatic regimes, that have contributed to its present shape. Ongoing processes, which include natural-compatible pastoral and forest activity continue to shape the dome.
Despite the human presence, the volcano is large enough to presently maintain its natural evolution in the long term and adapt to changing climatic conditions. However, there are many sites of concern, where installations have the potential to alter this, and to generate enhanced risk to the geological nature and to visitors. With our analysis, we can propose management strategies that can minimize impact, can be monitored, and which can protect the geoheritage and the fragile ecology, while allowing continued access to the site. Human access needs to respect and to be adapted to the natural conditions.
How to cite: van Wyk de Vries, B., Pál, M., Albert, G., Vörös, F., Grosse, P., and Delage, E.: The Puy de Dôme: Natural or Anthropogenic? Understanding, managing and protecting an original landscape in a UNESCO World Heritage site, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7145, https://doi.org/10.5194/egusphere-egu21-7145, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
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Humans are part of nature, so natural landscapes can contain human impacts. The limit of this natural anthropomorphic influence, where landscape stops being natural, is not defined clearly, but major infrastructure, urbanization etc. are clearly non-natural elements. When a natural feature becomes important for humans, such as the iconic Puy de Dôme volcano in central France, it tends to attract human modification. The Puy de Dôme was a Druidic and Roman sacred site, with added temples and paths. Yet, outside these, the majority of the mountain remained in a natural state, evolving by erosion, slope movement, and accumulating debris on its lower flanks. The natural state can still be seen in the detailed morphometry of its flanks. Since the turn of the 20th century, increased human activity has further modified the site, with the construction of a spiral cog railway track, and infrastructure: restaurants, observatories, military and communication buildings, including the iconic spike – that inhabitants are so attached to. Despite this increased activity, the essential natural values of the mountain have been mostly maintained, although the spiral railway track has cut / modified the natural drainage to some extent. With UNESCO World Heritage inscription in 2018, visitation is on the increase, and with more visitors, further pressure has been seen. Occasional debris flows and landslides have also become newsworthy events, impacting the railway operation. New slope stability plans have been drawn up for the cog railway and the footpaths, which have included large scale bolting of outcrops, wire meshing and rock removal. These have been implemented only very partially due to opposition from ecology and geoheritage actors.
To provide a clear picture of the natural state of the Puy de Dôme and to guide natural protection and risk management, a full geomorphological and morphometric analysis is needed. This abstract gives the first results of this work, presenting the geomorphology and morphometry, including a geomorphon and shape analysis, and 3-D Virtual Reality LiDAR topography. The resulting information allows us to determine the state of 'naturality' of the Puy de Dôme and establish the natural system and determine its anthropogenic influences. The volcano, since its eruption 11,000 years ago, has been slowly evolving under different climatic regimes, that have contributed to its present shape. Ongoing processes, which include natural-compatible pastoral and forest activity continue to shape the dome.
Despite the human presence, the volcano is large enough to presently maintain its natural evolution in the long term and adapt to changing climatic conditions. However, there are many sites of concern, where installations have the potential to alter this, and to generate enhanced risk to the geological nature and to visitors. With our analysis, we can propose management strategies that can minimize impact, can be monitored, and which can protect the geoheritage and the fragile ecology, while allowing continued access to the site. Human access needs to respect and to be adapted to the natural conditions.
How to cite: van Wyk de Vries, B., Pál, M., Albert, G., Vörös, F., Grosse, P., and Delage, E.: The Puy de Dôme: Natural or Anthropogenic? Understanding, managing and protecting an original landscape in a UNESCO World Heritage site, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7145, https://doi.org/10.5194/egusphere-egu21-7145, 2021.
EGU21-7264 | vPICO presentations | GM12.8
Methods for soil enhancement in geoheritage research: a case study from Veglia-Devero Natural Park (Lepontine Alps)Anna Masseroli, Irene M. Bollati, Luca Trombino, and Manuela Pelfini
In mountain environments, the high variability of soil forming factors (i.e., parent material, climate, relief, organism, time) is responsible for the presence of different soil types, which not only contribute to the pedodiversity but are also a component of the local cultural heritage.
Up to now, scarce attention has been paid to the soil in the geoheritage/geoconservation scientific analyses.
To promote soil as element concurring to mountain geoheritage definition, we propose a strategy to include pedological topics within a multidisciplinary trail planned in the Veglia-Devero Natural Park (Lepontine Alps). The geomorphological dynamicity and environmental change affecting during times the small mountain catchment of Buscagna hydrographic basin are illustrated with a specific address to soil characteristics. The physical and chemical properties, and pedological features of soils reflect the interaction among the other ecosystem components (i.e. geology, geomorphology and vegetation), underlining the role of soil as natural archive for reconstructing landscape evolution and for achieving a more complete assessment of Late Quaternary geomorphic events, especially surface processes.
Geopedological researches carried out in the study area, allowed to detect 7 soil profiles as potential sites of pedological interest, located in safe and accessible places, along already existing hiking paths. The selected soil profiles not only mirror the main soil types that characterize the area but also represent evidence of past environmental conditions and geomorphic dynamics.
The opportunities for hikers and mountaineers, to observe the exposed soils along the Buscagna valley, thanks to the presence of erosional scarps and subsidence areas, allow also to get more awareness of the need of geoheritage conservation strategies addressed to soil, especially in the mountain landscape where soil characteristics reflect the striking influence of its forming factors.
How to cite: Masseroli, A., Bollati, I. M., Trombino, L., and Pelfini, M.: Methods for soil enhancement in geoheritage research: a case study from Veglia-Devero Natural Park (Lepontine Alps), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7264, https://doi.org/10.5194/egusphere-egu21-7264, 2021.
In mountain environments, the high variability of soil forming factors (i.e., parent material, climate, relief, organism, time) is responsible for the presence of different soil types, which not only contribute to the pedodiversity but are also a component of the local cultural heritage.
Up to now, scarce attention has been paid to the soil in the geoheritage/geoconservation scientific analyses.
To promote soil as element concurring to mountain geoheritage definition, we propose a strategy to include pedological topics within a multidisciplinary trail planned in the Veglia-Devero Natural Park (Lepontine Alps). The geomorphological dynamicity and environmental change affecting during times the small mountain catchment of Buscagna hydrographic basin are illustrated with a specific address to soil characteristics. The physical and chemical properties, and pedological features of soils reflect the interaction among the other ecosystem components (i.e. geology, geomorphology and vegetation), underlining the role of soil as natural archive for reconstructing landscape evolution and for achieving a more complete assessment of Late Quaternary geomorphic events, especially surface processes.
Geopedological researches carried out in the study area, allowed to detect 7 soil profiles as potential sites of pedological interest, located in safe and accessible places, along already existing hiking paths. The selected soil profiles not only mirror the main soil types that characterize the area but also represent evidence of past environmental conditions and geomorphic dynamics.
The opportunities for hikers and mountaineers, to observe the exposed soils along the Buscagna valley, thanks to the presence of erosional scarps and subsidence areas, allow also to get more awareness of the need of geoheritage conservation strategies addressed to soil, especially in the mountain landscape where soil characteristics reflect the striking influence of its forming factors.
How to cite: Masseroli, A., Bollati, I. M., Trombino, L., and Pelfini, M.: Methods for soil enhancement in geoheritage research: a case study from Veglia-Devero Natural Park (Lepontine Alps), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7264, https://doi.org/10.5194/egusphere-egu21-7264, 2021.
EGU21-9236 * | vPICO presentations | GM12.8 | Highlight
Inventory of geoheritage as a tool for local sustainable development in Cajón del Maipo Geopark Project, Central ChileCamilo Vergara Daskam, Cristóbal Estay Daskam, and Anthony Prior Carvajal
Cajón del Maipo is a mountainous territory located in the Andes Cordillera of central Chile (~ 5,000 km2), 50 km away from Santiago city, and is one of the most visited tourist destinations in the country. It reaches a maximum altitude of 6,570 masl, and its geology is controlled by the compressive subduction regime between the Nazca and the South American plates. In its rocks, 166 million years of geological history are recorded, and its geodiversity includes: sedimentary and igneous rocks, active stratovolcanoes, thermal springs, tectonic structures, glacial and fluvial morphologies, landslides, marine fossils, and abandoned mine shafts. The area is part of the Chilean biodiversity hotspot, and hosts an important and strained water system, with ~650 glaciers that supplies almost the entire city of Santiago with drinking and irrigation water, home to more than 7 million people.
This work shows the existing inventory of geoheritage of Cajon del Maipo, which includes 43 geosites classified in 10 geological thematic areas. Geosites were selected and assessed using a quantitative approach in the three main types of use (scientific, educational and geotouristic), and in their degradation risk. Of the inventory list, 5 geosites have international relevance, 17 national relevance, 10 regional and 11 local relevance. Additional values where highlighted associated with potential for developing geopark activities (cultural and intangible heritage, biodiversity, climate change and geological hazards), as well as legal aspects regarding protection. Combining statistical, geographical, and qualitative analysis of the previous parameters, geosites were categorized in multi labeled management classes, which are: geotourism, education, science, and conservation. For each class, management priorities and opportunities were identified, including research, protection, promotion, infrastructure habilitation, and monitoring. In the next years, this inventory must be the framework for developing a local geoheritage management plan, and the basis for the elaboration of the application dossier of Cajon del Maipo as a UNESCO Global Geopark.
Cajon del Maipo Geopark Project has been developed since 2017 with the main goals of providing economic opportunities for local community and promoting the sustainable management of natural and cultural heritage. Framed in the project Action Plan, actions and initiatives have been implemented, including: geoheritage research and geoconservation; geotourism and local products development; geoeducation programs focused on local schools; and networking at local, national, and international levels. All the mentioned initiatives are supported by the creation and the permanent updating of the Cajon del Maipo inventory of geoheritage.
How to cite: Vergara Daskam, C., Estay Daskam, C., and Prior Carvajal, A.: Inventory of geoheritage as a tool for local sustainable development in Cajón del Maipo Geopark Project, Central Chile , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9236, https://doi.org/10.5194/egusphere-egu21-9236, 2021.
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Cajón del Maipo is a mountainous territory located in the Andes Cordillera of central Chile (~ 5,000 km2), 50 km away from Santiago city, and is one of the most visited tourist destinations in the country. It reaches a maximum altitude of 6,570 masl, and its geology is controlled by the compressive subduction regime between the Nazca and the South American plates. In its rocks, 166 million years of geological history are recorded, and its geodiversity includes: sedimentary and igneous rocks, active stratovolcanoes, thermal springs, tectonic structures, glacial and fluvial morphologies, landslides, marine fossils, and abandoned mine shafts. The area is part of the Chilean biodiversity hotspot, and hosts an important and strained water system, with ~650 glaciers that supplies almost the entire city of Santiago with drinking and irrigation water, home to more than 7 million people.
This work shows the existing inventory of geoheritage of Cajon del Maipo, which includes 43 geosites classified in 10 geological thematic areas. Geosites were selected and assessed using a quantitative approach in the three main types of use (scientific, educational and geotouristic), and in their degradation risk. Of the inventory list, 5 geosites have international relevance, 17 national relevance, 10 regional and 11 local relevance. Additional values where highlighted associated with potential for developing geopark activities (cultural and intangible heritage, biodiversity, climate change and geological hazards), as well as legal aspects regarding protection. Combining statistical, geographical, and qualitative analysis of the previous parameters, geosites were categorized in multi labeled management classes, which are: geotourism, education, science, and conservation. For each class, management priorities and opportunities were identified, including research, protection, promotion, infrastructure habilitation, and monitoring. In the next years, this inventory must be the framework for developing a local geoheritage management plan, and the basis for the elaboration of the application dossier of Cajon del Maipo as a UNESCO Global Geopark.
Cajon del Maipo Geopark Project has been developed since 2017 with the main goals of providing economic opportunities for local community and promoting the sustainable management of natural and cultural heritage. Framed in the project Action Plan, actions and initiatives have been implemented, including: geoheritage research and geoconservation; geotourism and local products development; geoeducation programs focused on local schools; and networking at local, national, and international levels. All the mentioned initiatives are supported by the creation and the permanent updating of the Cajon del Maipo inventory of geoheritage.
How to cite: Vergara Daskam, C., Estay Daskam, C., and Prior Carvajal, A.: Inventory of geoheritage as a tool for local sustainable development in Cajón del Maipo Geopark Project, Central Chile , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9236, https://doi.org/10.5194/egusphere-egu21-9236, 2021.
EGU21-12127 | vPICO presentations | GM12.8
Protecting Quaternary palaeoenvironmental sites in south-east Arabia: a database approachKenta Sayama, Ash Parton, and Heather Viles
Quaternary palaeoenvironmental archives are essential for our understanding of past climate changes and humanity’s response to them. In the age of anthropogenic climate change, these sites are not only important scientifically, but also educationally to teach people about the impact of climate change, and the role it played in shaping past communities.
The landscape of the Arabian Peninsula is highly reactive to even subtle changes in climate and recent research has shown that palaeoenvironmental archives in south-east Arabia (i.e., dunes, fluvial/alluvial and palaeolake deposits, etc.) are crucial for our understanding of the role of climate change in the late-Pleistocene dispersal of early human populations out of Africa. The importance of archaeological sites in this region is increasingly recognised, with many sites benefitting from extensive research and conservation. Similarly, the rich geological history of the region has either been catalogued or protected with integration into national tourism strategies. Despite the the budding initiative of geoheritage conservation in Arabia, however, the protection of Quaternary palaeoenvironmental sites has been entirely disregarded.
With the lack of a protection framework and the continuous economic development of the region, many of these archives are under imminent threat or already destroyed. At present, no assessment has been conducted to examine the possible extent of such loss. Here we propose that a system must be established for scientists to record and highlight the potential threat of destruction of these irreplaceable archives. Also, to protect these sites effectively, we must develop a conservation strategy with an understanding of the factors that differentiate them from geoheritage sites that already enjoy protection.
For the first time, this study has compiled a database of Quaternary palaeoenvironmental archives in south-east Arabia. A total of ~300 sites in the entire region have been assessed for their risk status, with ~100 sites in the UAE assessed additionally for their scientific and educational values. Preliminary results indicate that more than 10% of sites, mostly in urban or coastal settings, have been destroyed or are under imminent threat. Furthermore, the prevailing prioritisation of conventional aesthetic values in geoheritage conservation has been identified as a major obstacle in promoting the conservation of these sites.
How to cite: Sayama, K., Parton, A., and Viles, H.: Protecting Quaternary palaeoenvironmental sites in south-east Arabia: a database approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12127, https://doi.org/10.5194/egusphere-egu21-12127, 2021.
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Quaternary palaeoenvironmental archives are essential for our understanding of past climate changes and humanity’s response to them. In the age of anthropogenic climate change, these sites are not only important scientifically, but also educationally to teach people about the impact of climate change, and the role it played in shaping past communities.
The landscape of the Arabian Peninsula is highly reactive to even subtle changes in climate and recent research has shown that palaeoenvironmental archives in south-east Arabia (i.e., dunes, fluvial/alluvial and palaeolake deposits, etc.) are crucial for our understanding of the role of climate change in the late-Pleistocene dispersal of early human populations out of Africa. The importance of archaeological sites in this region is increasingly recognised, with many sites benefitting from extensive research and conservation. Similarly, the rich geological history of the region has either been catalogued or protected with integration into national tourism strategies. Despite the the budding initiative of geoheritage conservation in Arabia, however, the protection of Quaternary palaeoenvironmental sites has been entirely disregarded.
With the lack of a protection framework and the continuous economic development of the region, many of these archives are under imminent threat or already destroyed. At present, no assessment has been conducted to examine the possible extent of such loss. Here we propose that a system must be established for scientists to record and highlight the potential threat of destruction of these irreplaceable archives. Also, to protect these sites effectively, we must develop a conservation strategy with an understanding of the factors that differentiate them from geoheritage sites that already enjoy protection.
For the first time, this study has compiled a database of Quaternary palaeoenvironmental archives in south-east Arabia. A total of ~300 sites in the entire region have been assessed for their risk status, with ~100 sites in the UAE assessed additionally for their scientific and educational values. Preliminary results indicate that more than 10% of sites, mostly in urban or coastal settings, have been destroyed or are under imminent threat. Furthermore, the prevailing prioritisation of conventional aesthetic values in geoheritage conservation has been identified as a major obstacle in promoting the conservation of these sites.
How to cite: Sayama, K., Parton, A., and Viles, H.: Protecting Quaternary palaeoenvironmental sites in south-east Arabia: a database approach, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12127, https://doi.org/10.5194/egusphere-egu21-12127, 2021.
EGU21-12493 | vPICO presentations | GM12.8
The Geodiversity of Brazil: quantification, distribution, and implications for conservation areasJuliana Silva, Jurandyr Ross, Grace Alves, Fábio de Oliveira, Marcos Antonio Nascimento, Mateus Felini, Fernando Manosso, and Diamantino Pereira
Research related to the assessment of Geodiversity is highly relevant both at the international and national levels, especially in the last 20 years. These researches aim at valuing abiotic aspects as inseparable components of natural heritage and, thus, as well as Biodiversity, must be understood and valued through the ordering of their use and Geoconservation. Geodiversity studies are developed on the basis of several approaches, from the broadest ones, which contemplate the measurement of abiotic elements in a full way, to those that assess Geoheritage through the values of Geodiversity. The present research follows the broader approach of the evaluation and analysis of the entire Geodiversity, applying the measurement of abiotic elements without their valuation, with the purpose of the spatialization of areas with greater and lesser density of the selected elements related in this research to lithology, relief and soil. For this purpose, bases produced by systematic surveys of national research institutions such as the Brazilian Institute of Geography and Statistics (IBGE) and the Geological Survey of Brazil (CPRM) were used. As a result, the mapping of the subindexes was obtained pointing from the division into 5 classes, the areas that present greater and lesser diversity of each element, as well as the synthesis map for the indexes of Geodiversity elements in Brazil, considering the three elements selected for this mapping. A spatial analysis was also carried out between the Geodiversity Index Map and the Brazilian Conservation Units, as well as the areas where Geopark Projects are being developed. The majority of the Brazilian territory presents low Geodiversity index (32%), followed by medium (28%), very low (17%), high (15%) and very high (8%). The higher indexes are found in ancient Orogenic Belts, associated with Crystalline Basement that shows broad variation of rocks, in some cases linked with soil and relief elements. Areas of medium diversity are concentrated in Cratons and Sedimentary Basins borders, and low diversity areas are found in the central regions of large Sedimentary Basins, as well as in the Pantanal Floodplain. The Conservation Units present the following percentage of Geodiversity index: very high: 12%; high:10%; medium 16%; low: 23%; very low 22%. The analysis was done taking into account the categories of Conservation Units as well, and the higher indexes were found in Natural Monuments and Wildlife Refuges (38 and 43% respectively). 8 geopark projects have predominance of very high and high Geodiversity indexes; 7 presents medium index and only one amongst the 16 presents predominance of low index. No geopark project has very low index predominant in territory. The analysis of the spatialization of the indexes was carried out from a descriptive and genetic perspective, aiming at clarifying the causes of the distribution of the abiotic elements in the Brazilian territory, being able to provide subindexes for studies in the scope of environmental services, nature and territory conservation planning.
How to cite: Silva, J., Ross, J., Alves, G., de Oliveira, F., Nascimento, M. A., Felini, M., Manosso, F., and Pereira, D.: The Geodiversity of Brazil: quantification, distribution, and implications for conservation areas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12493, https://doi.org/10.5194/egusphere-egu21-12493, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
Research related to the assessment of Geodiversity is highly relevant both at the international and national levels, especially in the last 20 years. These researches aim at valuing abiotic aspects as inseparable components of natural heritage and, thus, as well as Biodiversity, must be understood and valued through the ordering of their use and Geoconservation. Geodiversity studies are developed on the basis of several approaches, from the broadest ones, which contemplate the measurement of abiotic elements in a full way, to those that assess Geoheritage through the values of Geodiversity. The present research follows the broader approach of the evaluation and analysis of the entire Geodiversity, applying the measurement of abiotic elements without their valuation, with the purpose of the spatialization of areas with greater and lesser density of the selected elements related in this research to lithology, relief and soil. For this purpose, bases produced by systematic surveys of national research institutions such as the Brazilian Institute of Geography and Statistics (IBGE) and the Geological Survey of Brazil (CPRM) were used. As a result, the mapping of the subindexes was obtained pointing from the division into 5 classes, the areas that present greater and lesser diversity of each element, as well as the synthesis map for the indexes of Geodiversity elements in Brazil, considering the three elements selected for this mapping. A spatial analysis was also carried out between the Geodiversity Index Map and the Brazilian Conservation Units, as well as the areas where Geopark Projects are being developed. The majority of the Brazilian territory presents low Geodiversity index (32%), followed by medium (28%), very low (17%), high (15%) and very high (8%). The higher indexes are found in ancient Orogenic Belts, associated with Crystalline Basement that shows broad variation of rocks, in some cases linked with soil and relief elements. Areas of medium diversity are concentrated in Cratons and Sedimentary Basins borders, and low diversity areas are found in the central regions of large Sedimentary Basins, as well as in the Pantanal Floodplain. The Conservation Units present the following percentage of Geodiversity index: very high: 12%; high:10%; medium 16%; low: 23%; very low 22%. The analysis was done taking into account the categories of Conservation Units as well, and the higher indexes were found in Natural Monuments and Wildlife Refuges (38 and 43% respectively). 8 geopark projects have predominance of very high and high Geodiversity indexes; 7 presents medium index and only one amongst the 16 presents predominance of low index. No geopark project has very low index predominant in territory. The analysis of the spatialization of the indexes was carried out from a descriptive and genetic perspective, aiming at clarifying the causes of the distribution of the abiotic elements in the Brazilian territory, being able to provide subindexes for studies in the scope of environmental services, nature and territory conservation planning.
How to cite: Silva, J., Ross, J., Alves, G., de Oliveira, F., Nascimento, M. A., Felini, M., Manosso, F., and Pereira, D.: The Geodiversity of Brazil: quantification, distribution, and implications for conservation areas, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12493, https://doi.org/10.5194/egusphere-egu21-12493, 2021.
EGU21-12799 | vPICO presentations | GM12.8 | Highlight
From landslide characterization to nature reserve management: The Scialimata Grande landslide Geosite (Central Appennine, Italy)Gianluca Tronti, Irene Maria Bollati, Manuela Pelfini, Filippo Belisario, and Paola Fredi
The Italian territory is characterized by frequent hydrogeological instability phenomena, among which landslides, responsible for a high number of damages, are able to leave impressive marks on the landscape and to rework the physical features of a territory. Nevertheless, landslide bodies may represent key sites for thematic itineraries, educational projects, and valorization especially in protected areas. Their management can consequently become an important issue in natural reserves’ management.
Our study focuses on the territory of the "Monte Rufeno Nature Reserve" (Central Apennines, Italy), where iconic landslides are present. Here, the "Scialimata Grande di Torre Alfina" landslide, is listed in the regional Geosite database. After creating a landslide susceptibility map for the reserve territory - based on drainage density and relief energy - the analysis was focused on the Scialimata complex landslide, to define properly its scientific and educational value. The geomorphological characterization of the landslide - carried out both on the field (geomorphological survey and GPS monitoring through wooden pins) that through remote sensing techniques (UAV drone, photointerpretation) - helped the assessment of the landslide dynamism. Moreover, dendrogeomorphological and ecological characterizations were performed to understand the relations between the geomorphic dynamics and the vegetation response (i.e., ecological support role of the Geosite). The area affected by Scialimata landslide falls into the highest landslide susceptibility class. At the local scale, its recent dynamics - as resulted from the GPS field monitoring in the 2015-2018 time interval - shows a maximum downvalley displacement of 23 meters. The landslide dynamics could be driven by a rain pattern with alternated dry and extremely wet periods; moreover, leakages from the water pipeline in proximity of the landslide crowning area, may have decreased the clays cohesion. The possible influence of the landslide, on the Paglia River dynamics, downvalley, was also hypothesized. Disturbances on plants ascribable to the landsliding, as tilted trunks and exposed roots, show distribution and characters explainable not only by the complex rotational dynamism of the landslide, but also by the hypothesized piping effect in the crowning zone. The landslide is highly representative of the geomorphic dynamics affecting the natural Reserve (i.e., scientific value) and it could be classified as an active Geosite, featured by a high ecological support role (not only towards vegetation) that increases the scientific value of the site too. Since the site was also featured by a touristic trail, that underwent disruption due to landslide movement, these results could enable adequate management strategies considering educational value and safety issues.
How to cite: Tronti, G., Bollati, I. M., Pelfini, M., Belisario, F., and Fredi, P.: From landslide characterization to nature reserve management: The Scialimata Grande landslide Geosite (Central Appennine, Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12799, https://doi.org/10.5194/egusphere-egu21-12799, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The Italian territory is characterized by frequent hydrogeological instability phenomena, among which landslides, responsible for a high number of damages, are able to leave impressive marks on the landscape and to rework the physical features of a territory. Nevertheless, landslide bodies may represent key sites for thematic itineraries, educational projects, and valorization especially in protected areas. Their management can consequently become an important issue in natural reserves’ management.
Our study focuses on the territory of the "Monte Rufeno Nature Reserve" (Central Apennines, Italy), where iconic landslides are present. Here, the "Scialimata Grande di Torre Alfina" landslide, is listed in the regional Geosite database. After creating a landslide susceptibility map for the reserve territory - based on drainage density and relief energy - the analysis was focused on the Scialimata complex landslide, to define properly its scientific and educational value. The geomorphological characterization of the landslide - carried out both on the field (geomorphological survey and GPS monitoring through wooden pins) that through remote sensing techniques (UAV drone, photointerpretation) - helped the assessment of the landslide dynamism. Moreover, dendrogeomorphological and ecological characterizations were performed to understand the relations between the geomorphic dynamics and the vegetation response (i.e., ecological support role of the Geosite). The area affected by Scialimata landslide falls into the highest landslide susceptibility class. At the local scale, its recent dynamics - as resulted from the GPS field monitoring in the 2015-2018 time interval - shows a maximum downvalley displacement of 23 meters. The landslide dynamics could be driven by a rain pattern with alternated dry and extremely wet periods; moreover, leakages from the water pipeline in proximity of the landslide crowning area, may have decreased the clays cohesion. The possible influence of the landslide, on the Paglia River dynamics, downvalley, was also hypothesized. Disturbances on plants ascribable to the landsliding, as tilted trunks and exposed roots, show distribution and characters explainable not only by the complex rotational dynamism of the landslide, but also by the hypothesized piping effect in the crowning zone. The landslide is highly representative of the geomorphic dynamics affecting the natural Reserve (i.e., scientific value) and it could be classified as an active Geosite, featured by a high ecological support role (not only towards vegetation) that increases the scientific value of the site too. Since the site was also featured by a touristic trail, that underwent disruption due to landslide movement, these results could enable adequate management strategies considering educational value and safety issues.
How to cite: Tronti, G., Bollati, I. M., Pelfini, M., Belisario, F., and Fredi, P.: From landslide characterization to nature reserve management: The Scialimata Grande landslide Geosite (Central Appennine, Italy), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12799, https://doi.org/10.5194/egusphere-egu21-12799, 2021.
EGU21-13293 | vPICO presentations | GM12.8 | Highlight
The ancient city and the rising sea. Using archaeogeosites to convey climate awareness.Guido Stefano Mariani and Rita Teresa Melis
The interaction between human societies and the physical landscape is deep and widespread since the dawn of civilisation. The development of different cultures always had to take into account their physical and geological surrounding, in order to adapt to their features and exploit them in the most efficient fashion. Cultural and geological heritage are therefore often tightly linked in a relationship enhancing the meaning of both to society in many ways. Tapping into these cultural archives can provide a useful way of communicating geoheritage to the wider public through the history of human-landscape interactions. Such landmarks would effectively act as witnesses of Earth history from a human point of view and become beneficial in spreading knowledge about past and current geological processes such as climate change. With the help of archaeogeosites, integrated reconstructions where the geological and geomorphological evidence with the elements of archaeological heritage could provide an effective way of communicating to the larger public sea level dynamics at a longer scale and the effects of climate change in the present and near future.
As a case study, the late ancient city of Nora is particularly effective. Located in southwestern Sardinia (Italy), it was a seaport of great importance during the Punic and Roman periods. Its surrounding landscape is deeply influenced by the marine transgression happening since the Last Glacial Maximum. Along the coast, many landforms and stratigraphic sequences bear evidence of sea level fluctuations and the related changes in the landscape revealing the larger context in which the city was developed. Beach deposits dated to MIS5 are buried by fluvial deposits and soils indicating a much lower sea level during later stadial periods. Since the passage to the Holocene the area, dominated by fluvial and slope dynamics, is interested by the progressive rise of the coastline and the consequent land loss. The city itself was not spared from this process. While its strategic coastal position was instrumental in its rise to prominence, the exposure to a rising sea level had a great impact on its history, both during its development and later as an abandoned settlement and an archaeological site. Several human structures possibly show the necessity of shielding against a progressively more damaging wave action.
How to cite: Mariani, G. S. and Melis, R. T.: The ancient city and the rising sea. Using archaeogeosites to convey climate awareness., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13293, https://doi.org/10.5194/egusphere-egu21-13293, 2021.
The interaction between human societies and the physical landscape is deep and widespread since the dawn of civilisation. The development of different cultures always had to take into account their physical and geological surrounding, in order to adapt to their features and exploit them in the most efficient fashion. Cultural and geological heritage are therefore often tightly linked in a relationship enhancing the meaning of both to society in many ways. Tapping into these cultural archives can provide a useful way of communicating geoheritage to the wider public through the history of human-landscape interactions. Such landmarks would effectively act as witnesses of Earth history from a human point of view and become beneficial in spreading knowledge about past and current geological processes such as climate change. With the help of archaeogeosites, integrated reconstructions where the geological and geomorphological evidence with the elements of archaeological heritage could provide an effective way of communicating to the larger public sea level dynamics at a longer scale and the effects of climate change in the present and near future.
As a case study, the late ancient city of Nora is particularly effective. Located in southwestern Sardinia (Italy), it was a seaport of great importance during the Punic and Roman periods. Its surrounding landscape is deeply influenced by the marine transgression happening since the Last Glacial Maximum. Along the coast, many landforms and stratigraphic sequences bear evidence of sea level fluctuations and the related changes in the landscape revealing the larger context in which the city was developed. Beach deposits dated to MIS5 are buried by fluvial deposits and soils indicating a much lower sea level during later stadial periods. Since the passage to the Holocene the area, dominated by fluvial and slope dynamics, is interested by the progressive rise of the coastline and the consequent land loss. The city itself was not spared from this process. While its strategic coastal position was instrumental in its rise to prominence, the exposure to a rising sea level had a great impact on its history, both during its development and later as an abandoned settlement and an archaeological site. Several human structures possibly show the necessity of shielding against a progressively more damaging wave action.
How to cite: Mariani, G. S. and Melis, R. T.: The ancient city and the rising sea. Using archaeogeosites to convey climate awareness., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13293, https://doi.org/10.5194/egusphere-egu21-13293, 2021.
EGU21-13621 | vPICO presentations | GM12.8
Determinants of geoheritage conservation: Multiple correspondence analysis to explore interrelations between socio-economic and bibliometric dataBoglárka Németh and Károly Németh
Geoheritage is an emerging research subject with increasing global interest to define, characterize and quantify it in diverse geological and geomorphological settings. As being a new research subject there are great variety of conceptual approaches to do its definition and quantification. Geoheritage conservation is in the process of establishing a common ground that become necessary in the transnational collaboration for a sustainable future. Geoheritage conservation generates ever increasing number of scientific publications based on heterogenous evaluation methods with limited consensus within the field. The produced material, also part of various Big Data repositories, conceals valuable patterns and information on the level of agreement and the solution to draw the line for the acceptable level of subjectivity. Analysing bibliometric data of scientific publication appear in accessible global data bases (e.g. Web of Science) broken down to country levels allow us to find potential indicators for geoheritage designation. Finding determinants that positively influences decision makers and end users within the conservation arena helps geoscientists to achieve policy impact and increase the number of recognised and protected geological and geomorphological sites. Multiple Correspondence Analysis was used to detect and explore relationships between population, land, tourism, protected areas and bibliometric variables. The result revealed very important links between the socio-economic background and geoheritage conservation outcomes. The fact that there was no one major determinant found that would affect geoheritage conservation globally means that a common ground awaits to be established on which countries can build upon with the unique and special values local communities have to contribute toward geoheritage conservation.
The research is aligned with the goals of the “Geoheritage for Resilience” UNESCO IGPC project 692 program.
How to cite: Németh, B. and Németh, K.: Determinants of geoheritage conservation: Multiple correspondence analysis to explore interrelations between socio-economic and bibliometric data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13621, https://doi.org/10.5194/egusphere-egu21-13621, 2021.
Geoheritage is an emerging research subject with increasing global interest to define, characterize and quantify it in diverse geological and geomorphological settings. As being a new research subject there are great variety of conceptual approaches to do its definition and quantification. Geoheritage conservation is in the process of establishing a common ground that become necessary in the transnational collaboration for a sustainable future. Geoheritage conservation generates ever increasing number of scientific publications based on heterogenous evaluation methods with limited consensus within the field. The produced material, also part of various Big Data repositories, conceals valuable patterns and information on the level of agreement and the solution to draw the line for the acceptable level of subjectivity. Analysing bibliometric data of scientific publication appear in accessible global data bases (e.g. Web of Science) broken down to country levels allow us to find potential indicators for geoheritage designation. Finding determinants that positively influences decision makers and end users within the conservation arena helps geoscientists to achieve policy impact and increase the number of recognised and protected geological and geomorphological sites. Multiple Correspondence Analysis was used to detect and explore relationships between population, land, tourism, protected areas and bibliometric variables. The result revealed very important links between the socio-economic background and geoheritage conservation outcomes. The fact that there was no one major determinant found that would affect geoheritage conservation globally means that a common ground awaits to be established on which countries can build upon with the unique and special values local communities have to contribute toward geoheritage conservation.
The research is aligned with the goals of the “Geoheritage for Resilience” UNESCO IGPC project 692 program.
How to cite: Németh, B. and Németh, K.: Determinants of geoheritage conservation: Multiple correspondence analysis to explore interrelations between socio-economic and bibliometric data, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13621, https://doi.org/10.5194/egusphere-egu21-13621, 2021.
EGU21-13752 | vPICO presentations | GM12.8 | Highlight
Weathering conditions of Buddhist caves dug in soft rocks and conservation attempting from the deteriorationChiaki Oguchi, Momoko Ogawa, Kaisei Sakane, and Yasuhiko Tamura
The Taya Cave, a sacred Buddhist cave, locates in the precincts of Josenji Temple in Yokohama City, central Japan. The geologic materials of the hills surrounding the cave are soft rocks composed of early Quaternary sedimentary rocks. The cave has a complex three-layer structure with a total length of 570 m. The excavation of the cave is estimated to start in the Kamakura era around A.D. 1200. Since then, the cave became a training place for Buddhists until around 19 C. There are many Buddhist reliefs on the walls and ceiling inside the cave. Because the bedrock is extremely weak, the rocks easily break when they get wet again after drying, namely prone to slaking. Thus, weathering and deterioration have progressed in various parts of the cave. Many valuable Buddhist reliefs have damaged by exfoliation. The walls at several points in the cave have also collapsed on a small scale. Therefore, it is necessary to investigate such deteriorated parts in the cave by simple non-destructive tests of physical and mechanical properties by using Silver Schmidt hammer and ultrasonic velocity test. These measurements clarified the vulnerable points even in the main worship route of the cave. In October 2018, a stainless-steel door installed at the cave entrance to save from deterioration due to slaking. The effect of the door was verified as well by monitoring the environmental conditions inside the cave. Environmental monitoring results revealed that the temperature and humidity near the entrance changed most drastically in this cave. Although the door was closed only at night, the range of maximum and minimum values of temperature and humidity near the entrance became smaller after installation than before. Non-destructive measurements and in situ environmental monitoring are a useful way to assess weathering without damaging geoarchaeological sites.
How to cite: Oguchi, C., Ogawa, M., Sakane, K., and Tamura, Y.: Weathering conditions of Buddhist caves dug in soft rocks and conservation attempting from the deterioration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13752, https://doi.org/10.5194/egusphere-egu21-13752, 2021.
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The Taya Cave, a sacred Buddhist cave, locates in the precincts of Josenji Temple in Yokohama City, central Japan. The geologic materials of the hills surrounding the cave are soft rocks composed of early Quaternary sedimentary rocks. The cave has a complex three-layer structure with a total length of 570 m. The excavation of the cave is estimated to start in the Kamakura era around A.D. 1200. Since then, the cave became a training place for Buddhists until around 19 C. There are many Buddhist reliefs on the walls and ceiling inside the cave. Because the bedrock is extremely weak, the rocks easily break when they get wet again after drying, namely prone to slaking. Thus, weathering and deterioration have progressed in various parts of the cave. Many valuable Buddhist reliefs have damaged by exfoliation. The walls at several points in the cave have also collapsed on a small scale. Therefore, it is necessary to investigate such deteriorated parts in the cave by simple non-destructive tests of physical and mechanical properties by using Silver Schmidt hammer and ultrasonic velocity test. These measurements clarified the vulnerable points even in the main worship route of the cave. In October 2018, a stainless-steel door installed at the cave entrance to save from deterioration due to slaking. The effect of the door was verified as well by monitoring the environmental conditions inside the cave. Environmental monitoring results revealed that the temperature and humidity near the entrance changed most drastically in this cave. Although the door was closed only at night, the range of maximum and minimum values of temperature and humidity near the entrance became smaller after installation than before. Non-destructive measurements and in situ environmental monitoring are a useful way to assess weathering without damaging geoarchaeological sites.
How to cite: Oguchi, C., Ogawa, M., Sakane, K., and Tamura, Y.: Weathering conditions of Buddhist caves dug in soft rocks and conservation attempting from the deterioration, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13752, https://doi.org/10.5194/egusphere-egu21-13752, 2021.
EGU21-15024 | vPICO presentations | GM12.8
Addressing indicators for geoheritage monitoring based on degradation risk and scientific value quantitative assessmentThais S. Canesin, Paulo Pereira, Juana Vegas, Lidia Selmi, Paola Coratza, and Vanda Santos
Keywords: monitoring, criteria, degradation, geoheritage, Vale de Meios, Portugal
Monitoring is one of the main stages in geoconservation strategies, essential to guarantee
geoheritage sustainability. Nevertheless, few studies focus on geoheritage monitoring techniques
and methods, unlike the multitude of works focusing on procedures to inventory and assess the
value of geosites. Moreover, criteria used in these methods can be applied on monitoring
procedures, specifically those supporting degradation risk and scientific value quantitative
assessments. In this context, a geoheritage monitoring model is being applied in Vale de Meios
(Alcanede, Portugal), an abandoned limestone quarry with well-preserved Middle Jurassic
Theropod footprints, inside the Serras de Aire e Candeeiros Natural Park. This geosite was
previously assessed for its scientific value and vulnerability and it is included in the Portuguese
inventory of geoheritage with national and international relevance. A set of “scientific value” and
“degradation risk/vulnerability” criteria were reviewed to assess the degradation of the geosite
and used to identify the most suitable monitoring model. The “integrity” criterium used in most
methods to assess the scientific value of geosites, also credited as “conservation status”, is strictly
connected with the deterioration of the geoheritage elements in the past and present, while
degradation risk is normally referring to the threats and potential losses in the future. Fourteen
“degradation risk” assessment sub-criteria (intrinsic active processes, deterioration of geological
elements, size, extrinsic active processes, proximity to active processes, economic potential,
collectible elements potential, protection status, proximity to human activities, accessibility,
population density, visitor facilities, degradation by public use, and visitation control) can be
distributed by the main criteria fragility, natural vulnerability, anthropic vulnerability, and public
use. A detailed analysis of the criteria and the specific characteristics of each geosite support the
definition of suitable monitoring indicators. In the Vale de Meios geosite, monitoring actions
should primarily consider: active natural process, deterioration of geological elements,
accessibility, visitor facilities, degradation by public use, and visitation control in order to define
the monitoring indicators. An analysis of the conservation status over the past decades has been
carried out, using time indicators of deterioration. Long-term monitoring results will provide more
data about the geoheritage degradation though partial data show that in Vale de Meios the main
concern is related with the high natural vulnerability of the Theropod footprints, which are
exposed to natural erosion. Despite the protection status of the area and design of a plan for
visitation control measures, conservation procedures should prioritize physical protection
initiatives in the geosite management strategies.
How to cite: Canesin, T. S., Pereira, P., Vegas, J., Selmi, L., Coratza, P., and Santos, V.: Addressing indicators for geoheritage monitoring based on degradation risk and scientific value quantitative assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15024, https://doi.org/10.5194/egusphere-egu21-15024, 2021.
Keywords: monitoring, criteria, degradation, geoheritage, Vale de Meios, Portugal
Monitoring is one of the main stages in geoconservation strategies, essential to guarantee
geoheritage sustainability. Nevertheless, few studies focus on geoheritage monitoring techniques
and methods, unlike the multitude of works focusing on procedures to inventory and assess the
value of geosites. Moreover, criteria used in these methods can be applied on monitoring
procedures, specifically those supporting degradation risk and scientific value quantitative
assessments. In this context, a geoheritage monitoring model is being applied in Vale de Meios
(Alcanede, Portugal), an abandoned limestone quarry with well-preserved Middle Jurassic
Theropod footprints, inside the Serras de Aire e Candeeiros Natural Park. This geosite was
previously assessed for its scientific value and vulnerability and it is included in the Portuguese
inventory of geoheritage with national and international relevance. A set of “scientific value” and
“degradation risk/vulnerability” criteria were reviewed to assess the degradation of the geosite
and used to identify the most suitable monitoring model. The “integrity” criterium used in most
methods to assess the scientific value of geosites, also credited as “conservation status”, is strictly
connected with the deterioration of the geoheritage elements in the past and present, while
degradation risk is normally referring to the threats and potential losses in the future. Fourteen
“degradation risk” assessment sub-criteria (intrinsic active processes, deterioration of geological
elements, size, extrinsic active processes, proximity to active processes, economic potential,
collectible elements potential, protection status, proximity to human activities, accessibility,
population density, visitor facilities, degradation by public use, and visitation control) can be
distributed by the main criteria fragility, natural vulnerability, anthropic vulnerability, and public
use. A detailed analysis of the criteria and the specific characteristics of each geosite support the
definition of suitable monitoring indicators. In the Vale de Meios geosite, monitoring actions
should primarily consider: active natural process, deterioration of geological elements,
accessibility, visitor facilities, degradation by public use, and visitation control in order to define
the monitoring indicators. An analysis of the conservation status over the past decades has been
carried out, using time indicators of deterioration. Long-term monitoring results will provide more
data about the geoheritage degradation though partial data show that in Vale de Meios the main
concern is related with the high natural vulnerability of the Theropod footprints, which are
exposed to natural erosion. Despite the protection status of the area and design of a plan for
visitation control measures, conservation procedures should prioritize physical protection
initiatives in the geosite management strategies.
How to cite: Canesin, T. S., Pereira, P., Vegas, J., Selmi, L., Coratza, P., and Santos, V.: Addressing indicators for geoheritage monitoring based on degradation risk and scientific value quantitative assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15024, https://doi.org/10.5194/egusphere-egu21-15024, 2021.
EGU21-16328 | vPICO presentations | GM12.8
Maximising the leverage of geoheritage research for effective sustainability policy and territorial managementSophie Justice, Chiara LoDestro, Marco Giardino, and Jean-Baptiste Bosson
The dissemination of Geoheritage research can be reinforced by building solid partnerships between researchers and national and regional stakeholders as practical experience has shown in the Chablais UNESCO Global Geopark. Increasingly, territorial management bodies, particularly those hosting UNESCO designations such as UNESCO Global Geoparks, public agencies with environmental preservation or resource management responsibilities and managers of national or regional geoheritage inventories actively seek to build partnerships with geoheritage researchers. These entities document and manage geoheritage as part of their overall responsibilities and have wider roles than conservation bodies. The non-academic professional teams responsible for geoheritage documentation, management and awareness raising include experienced geoscientists and highly trained science communicators. Professional geoheritage stakeholders have well-developed dissemination channels with public and private sector decision makers as well as the general public and schools that complete and complement academic geoheritage communication networks.
Recent examples from the Chablais UNESCO Global Geopark demonstrate how geoheritage professionals from the local development agency have worked in partnership with geoheritage researchers to maximise the impact of new scientific research in the territory. These examples highlight how collaboration between researchers and professionals embedded in the study region can leverage research results to a wide audience: decision makers, stakeholders, local population and school children. Three case studies highlight the different partnerships and how collaborations led to improved project robustness and scope. In addition, the examples underline how early collaboration leads not only to project improvements but also transmission through highly effective embedded communication channels that complement those of geoheritage researchers.
Each case study addresses a different geosite within the Chablais UGGp with different issues and stakeholders: a retrogressive landslide at Reyvroz, dolines at Nifflon and a series of lakes of varied origin at Saint Paul en Chablais. The examples demonstrate the scope for the application and recognition of research but also the need of researchers and territorial managers to make connections early on for these projects to achieve their full potential. This permits thorough, structured dialogue between researchers and stakeholders that result in geoheritage issues being recognised, understood and incorporated into territorial management decisions and sustainable policy. This is a crucial step given that the value of the natural environment from a general public and political standpoint continues to be equated with biodiversity and ecosystemic services to the detriment of geoheritage and geosystem services.
How to cite: Justice, S., LoDestro, C., Giardino, M., and Bosson, J.-B.: Maximising the leverage of geoheritage research for effective sustainability policy and territorial management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16328, https://doi.org/10.5194/egusphere-egu21-16328, 2021.
Please decide on your access
Please use the buttons below to download the presentation materials or to visit the external website where the presentation is linked. Regarding the external link, please note that Copernicus Meetings cannot accept any liability for the content and the website you will visit.
Forward to presentation link
You are going to open an external link to the presentation as indicated by the authors. Copernicus Meetings cannot accept any liability for the content and the website you will visit.
We are sorry, but presentations are only available for users who registered for the conference. Thank you.
The dissemination of Geoheritage research can be reinforced by building solid partnerships between researchers and national and regional stakeholders as practical experience has shown in the Chablais UNESCO Global Geopark. Increasingly, territorial management bodies, particularly those hosting UNESCO designations such as UNESCO Global Geoparks, public agencies with environmental preservation or resource management responsibilities and managers of national or regional geoheritage inventories actively seek to build partnerships with geoheritage researchers. These entities document and manage geoheritage as part of their overall responsibilities and have wider roles than conservation bodies. The non-academic professional teams responsible for geoheritage documentation, management and awareness raising include experienced geoscientists and highly trained science communicators. Professional geoheritage stakeholders have well-developed dissemination channels with public and private sector decision makers as well as the general public and schools that complete and complement academic geoheritage communication networks.
Recent examples from the Chablais UNESCO Global Geopark demonstrate how geoheritage professionals from the local development agency have worked in partnership with geoheritage researchers to maximise the impact of new scientific research in the territory. These examples highlight how collaboration between researchers and professionals embedded in the study region can leverage research results to a wide audience: decision makers, stakeholders, local population and school children. Three case studies highlight the different partnerships and how collaborations led to improved project robustness and scope. In addition, the examples underline how early collaboration leads not only to project improvements but also transmission through highly effective embedded communication channels that complement those of geoheritage researchers.
Each case study addresses a different geosite within the Chablais UGGp with different issues and stakeholders: a retrogressive landslide at Reyvroz, dolines at Nifflon and a series of lakes of varied origin at Saint Paul en Chablais. The examples demonstrate the scope for the application and recognition of research but also the need of researchers and territorial managers to make connections early on for these projects to achieve their full potential. This permits thorough, structured dialogue between researchers and stakeholders that result in geoheritage issues being recognised, understood and incorporated into territorial management decisions and sustainable policy. This is a crucial step given that the value of the natural environment from a general public and political standpoint continues to be equated with biodiversity and ecosystemic services to the detriment of geoheritage and geosystem services.
How to cite: Justice, S., LoDestro, C., Giardino, M., and Bosson, J.-B.: Maximising the leverage of geoheritage research for effective sustainability policy and territorial management, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16328, https://doi.org/10.5194/egusphere-egu21-16328, 2021.