Content:
Presentation type:

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 geomorphology

Louise 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.

EGU21-948 | Presentations | GM1.1

Influence of Wildfire on Earth Surface Processes and Geomorphology

Paul 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.

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 source

Onn 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.

EGU21-3561 | Presentations | GM1.1

The Geomorphology of Life

Paolo Tarolli

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 systems

Louise 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.

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.

EGU21-14966 | Presentations | GM1.1

Evolution and hydrological importance of debris-covered glaciers and ice-debris landforms

Tobias 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.

EGU21-16314 | Presentations | GM1.1

Connectivity in geomorphology

Ronald 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.

GM1.2 – Biogeomorphology/Ecogeomorphology: process understanding and application

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 imagery

Gerben 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.

EGU21-5669 | vPICO presentations | GM1.2

Integrating biogeomorphic feedbacks in the coastal zone to bolster coastal resiliency

Cindy 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.

EGU21-11017 | vPICO presentations | GM1.2

Insights in beachrock formation mechanism using multiproxy experimental data: Case study of Diolkos, Corinth, Greece

Giannis 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.

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 morphology

Muriel 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.

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 vegetation

Sabine 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.

EGU21-10083 | vPICO presentations | GM1.2

Modeling groundwater-driven morphodynamic evolution of a gravel bed river in presence of riparian vegetation

Ilaria 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.

EGU21-12515 | vPICO presentations | GM1.2

Rock and Roll: RFID Tracking of Fluvial Bedload Transport and Interaction with Large Wood 

Miles 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.

EGU21-10684 | vPICO presentations | GM1.2

Terrestrial biospheric carbon export from rivers by bedload transport

Sophia 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.

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, Austria

Stefan 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.

EGU21-4179 | vPICO presentations | GM1.2

UAV-based cm-scale mapping of biofilms and Chl-a patterns in glacial forefields using visible band ratios

Matteo 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.

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 basin

María 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.

EGU21-7882 | vPICO presentations | GM1.2

How spatial vegetation distribution affects soil erosion and sediment transport

Malte 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.

EGU21-10183 * | vPICO presentations | GM1.2 | Highlight

Estimating the global geomorphological importance of ants in the Anthropocene

Heather 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.

EGU21-2715 | vPICO presentations | GM1.2 | Highlight

Identifying causal links between tectono-geomorphic processes and biodiversity with a coupled landscape-biodiversity evolution model

Helen 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.

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 concept

José 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.

EGU21-15820 | vPICO presentations | GM1.3

Geodiversity, Geoheritage, Geoconservation: a semantic challenge

Alizia 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.

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 Rewilding

Kenneth 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.

EGU21-13977 | vPICO presentations | GM1.3 | Highlight

Initiative to establish the International Geodiversity Day

Zbigniew 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.

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.