Mountain landscapes are beautiful, yet hazardous, and vulnerable to climate change and population growth. Not only is the study of these landscapes geomorphically captivating, but it is increasingly relevant to society. Three Grand Challenges in the study of processes, landscapes and hazards in mountain regions are (1) Understanding and predicting the response of earth surface processes to climate (2) Monitoring and early warning of extreme events such as landslides and floods and (3) Accounting for connectivity and feedbacks between hillslopes and channels in landscape evolution and hazards. We need a suite of tools and approaches to address these challenges. Harnessing the growing archive of satellite and aerial photography helps us to study landscape dynamics and response to drivers such as climate over large regions. Innovative sensor technology is needed to understand landscape dynamics at a finer scale and to develop real time warning of extreme events. Finally, we need conceptual models that capture the essence of landscape dynamics and help to forecast hazards as they slide, flow, rock and roll through the landscape.

How to cite: Bennett, G.: Sliding, flowing, rocking and rolling: Sediment and hazard cascades through mountain landscapes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4726, https://doi.org/10.5194/egusphere-egu2020-4726, 2020.

The Anthropocene is widely described as producing a rupture in the global stratigraphic signature, attributable to human activities. There is no doubt that human activities have introduced new products into the stratigraphic record; and that humans are modifying the geomorphic processes that produce the sediment which then becomes incorporated into that record. The stratigraphic literature is replete with simplistic generalisations of how sediment flux to the continental shelf is changing, such as increasing due to soil erosion or decreasing due to hydropower related sediment flux disconnection. Here we argue that human impacts on geomorphic processes in the Anthropocene are unlikely to be stationary for long enough for them to be seen consistently across the depositional record of many different environments. Illustrating this for a major inner-Alpine drainage basin, the Swiss Rhône, we show that human-driven global climate-change is indeed dramatically altering the geomorphic process regimes of Alpine environments. However, there are three broad reasons why this is unlikely to be seen in the future geological record. First, the geomorphic response that drives increased sediment delivery is transient because of the significant regime changes associated with global climate change impacts. Second, such increases are countered by other human impacts, notably those on sediment flux, which are tending to reduce the connectivity of sediment sources to downstream sediment sinks. Third, human impacts on both sediment sources and connectivity are nonstationary, driven by both exogenous factors (here illustrated by the worldwide economic shock of 2008) and endogenous ones, notably human response to the perceived problems caused by both sediment starvation and sediment over-supply. In geomorphic terms, then, there is a difference between the pervasive nature of Earth system shifts that we see in the pre-Holocene depositional record and the more ephemeral impacts of the Earth system – human coupling associated with the Anthropocene. The extent to which this is the case is likely to vary geographically and temporally as a function of the degree and nature of human impacts on geomorphic processes. Thus, the primary challenge for future prediction will be as much the prediction of the complex and reflexive nature of human response as it will be geomorphic processes themselves.

How to cite: Lane, S.: Will human impacts on Alpine geomorphic processes scale up to the depositional record?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13018, https://doi.org/10.5194/egusphere-egu2020-13018, 2020.

Geomorphology has much to contribute to the understanding of how geomorphic landscapes have responded to climatological extremes and will likely respond in the future. These contributions can be in terms of systems dynamics and their past, present and likely future responses to sudden events, tipping points or more gradual changes to natural landforms and anthropogenic structures. However, equally importantly, geomorphic contributions also include making proactive resilience and climate change adaptation decisions in order to create physical space for geomorphic systems to respond more naturally and dynamically to extremes – now or in the near (100 year) future. The choices society makes in the present – such as planning, infrastructure and engineering decisions – have a strong bearing on the physical space left to allow natural landforms to adjust to extreme events while minimizing social and economic impacts. This creates a new frontier for geomorphology science at the social, political and policy interface.  Interesting questions arise in this space, such as: How much do we expect a geomorphic system to respond dynamically to extreme forcing? i.e. How much physical space do we [planners] need for the system to respond to an extreme event? Should society see storms as catalysts for proactive adaptation? How much (physical space, i.e. geomorphic accommodation space) can we allow when realigning road or rail inland to reduce risk in future storm events? How do complex physical geomorphic systems interact with complex urban systems? Can we work with artists, landscape architects, geo-spatial, urban and social scientists to create transformative, systems-based adaptation scenarios to allow us to better live in an era of extremes? Geomorphologists are usefully contributing to improving the resilience and/or limiting deterioration or habitat loss (e.g. habitat squeeze due to sea level rise) in urban ecosystems and anthropogenic structures.  This includes geomorphic contributions to nature-based solutions, green infrastructure and the resilience of traditional engineering to extreme events.  This paper highlights some of the opportunities we have to influence and shape our future resilience to extreme events – in the present day – through interdisciplinary research and socio-geomorphology practice. We need to create windows of opportunity now for more dynamic and resilient geomorphic futures.  

How to cite: Naylor, L., Hansom, J., Mitchell, D., Fitton, J., Muir, F., Hurst, M., and Rennie, A.: Re-imagining urban coasts: a socio-geomorphology lens to enhance life in an era of extremes , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20334, https://doi.org/10.5194/egusphere-egu2020-20334, 2020.

In this presentation, we will highlight some of the overarching geomorphic dynamics of gradual and abrupt permafrost thaw using examples from Siberia, Alaska, and Canada, their role in Arctic landscapes transitioning to a warmer world, and implications for the Earth System. Northern high latitude regions are particularly vulnerable to warming and changes in climatic patterns, which leads to the thaw of ice-rich permafrost across vast Arctic and sub-Arctic landscapes. Permafrost thaw and subsequent geomorphological change directly interact with hydrology, biogeochemistry, and biology and thus have been major agents of Arctic ecosystem change since the last deglaciation. The changes are also important contributors to cumulative impacts associated with historic and current development of the Arctic, including in association with infrastructure. Today, in a rapidly warming Arctic, permafrost thaw processes, both gradual and abrupt, are accelerating in a manner comparable to the Holocene Thermal Maximum. At the same time, other environmental forcing factors, such as wildfires, precipitation, and hydrological processes, are also changing, either further reinforcing thaw dynamics or enhancing drainage and stabilizing the ground. Many of the resulting gradual and abrupt thaw processes are non-linear. Their dynamics are still poorly understood and insufficiently quantified in large-scale models due to lacking or limited representation of water-ice phase transitions during freeze-thaw cycles, ground ice distribution and loss, and challenging implementation of sub-gridcell scale interactions between frozen ground and hydrology. Gradual thaw impacts are especially pronounced in regions with an abundance of ice wedge polygons, and include changes in microtopography and extensive ponding in natural landscapes and those adjacent to infrastructure, where soils are warmed due to increased dust, flooding, snowdrifts, and altered vegetation. Abrupt thaw processes such as thermokarst and thermo-erosion represent rapid dynamics that are widespread in Arctic lowlands but poorly represented in observations and models. Characteristic landforms that result from abrupt thaw include thermokarst lakes and basins, retrogressive thaw slumps, and steep coastal bluffs. These landscape changes may be triggered by climate-driven press disturbances such as sea ice loss or increases in precipitation, pulse disturbances such as wildfires, or by anthropogenic disturbances such as road construction. When loss of excess ground ice is involved, positive feedbacks can result in a decoupling of further geomorphological change from climate. Once initiated, this may lead to continued or even accelerated growth of such features under a wide range of climate conditions, including in the high Arctic. Most abrupt thaw processes produce lasting impacts on northern permafrost landscapes that are irreversible over millennial timescales and result in the short-term mobilization of large amounts of permafrost carbon that may further contribute to climate warming.

How to cite: Grosse, G., Boike, J., Farquharson, L., Jones, B. M., Langer, M., Lantuit, H., Liljedahl, A., Nitze, I., Runge, A., Romanovsky, V. E., Schneider von Deimling, T., Vincent, W. F., and Walker, D. A. (.: Gradual and Abrupt Permafrost Thaw as Drivers of Rapid Geomorphic Change in Arctic Permafrost Regions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11772, https://doi.org/10.5194/egusphere-egu2020-11772, 2020.

Climate change is expected to alter fire regimes but also rainfall patterns. Fire is a natural process that removes vegetation and may affect soil properties, resulting in changes in overland flow and streamflow generation. Some fires cause erosion and may even cause destructive debris flow and other events, which can not only threaten lives and property but also leave lasting imprints in landscapes. The geomorphological response after fire events is a complex function of pre-fire landscape and vegetation properties, fire behavior and effects, and post-fire rainfall timing, duration and intensity. In this talk, I highlight these processes using examples of past events, and explore geomorphological response to fires in a future where both fire and rainfall may be be rather different.

How to cite: Stoof, C.: Fire effects on geomorphology: what can we expect with climate change?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18260, https://doi.org/10.5194/egusphere-egu2020-18260, 2020.

Science progresses when we are afforded with a ‘better look’ at nature. For geomorphology, the production over the last 100 years of an ever-increasingly resolved view of landscapes with topographic maps, DEMs, remote-sensing images, etc. has always been accompanied by new geomorphologic discoveries. LiDAR images of formerly glaciated landscapes reveal glacial landforms in extraordinary detail, showing previously mapped landforms in exquisite new detail (for example, end moraines, drumlins, eskers, ice-walled-lake plains etc.). Particularly important are a range of ‘mesoscale’ landforms that are better seen with LiDAR: De Geer moraines, crag-and-tail ridges, low-relief lineations, post-glacial faults, glacial hummocks, and raised shorelines to name a few. A spate of research has come out recently on such features. LiDAR images also have the potential of revealing landforms new to glacier science, of which ‘murtoos’ are an example. But LiDAR also raises the challenge of geomorphic classification. For example, glacial hummocks and glacial hummocky topography are a mesoscale landform that is known for its high variability. This variability, made more dramatic with new LiDAR images, along with the polygenetic origin of landforms called ‘hummocks’ reveals a weakness in our terminology that needs to be acknowledged and dealt with.

How to cite: Johnson, M.: The LiDAR revolution in glacial geomorphology: its gifts and challenges, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7953, https://doi.org/10.5194/egusphere-egu2020-7953, 2020.

Loess gully is the most active and changeable landform unit in the Loess Plateau of China, whose morphology has been shaped under various formation processes. During the evolution process, gullies in the Loess Plateau interacted with each other and formed an intricate network system, which was the channel for material transportation and energy transmission in this area. From the perspective of the gully evolution process, the development of gully network is dynamic because such a network gradually tends to equilibrium through continuous reorganization. During the evolutionary process, stream capture occurs when a stream or watershed is diverted from its own bed, and flows instead down the bed of a neighboring stream. The stronger and more powerful streams (in terms of channel gradient, stream velocity, discharge and kinetic energy) capture the upstream of weak streams. In the process of dynamic reorganization, the loess gullies formed different shapes and gradually evolved into a stable network structure. In this paper, several gully areas in the Loess Plateau were selected. Based on the geological background, 5 m horizontal-resolution DEM data were used to analyze these areas. The χ index was used to describe the dynamic characteristics of the gully network, which could characterize the evolution trend of the gully. Finally, the author reveals the evolution and reorganization process of the loess gully networks by comparing the χ index diagrams of different areas in different developmental stages. The results show that the area with the stable geological background is closer to the equilibrium state than the area with the complicated geological structure. In other regions, networks composed of gullies in the middle development stage are more stable than networks in the early development stage. More importantly, for two adjacent mature gully networks, the developmental trends at different locations on their watershed boundaries may be different. The results provide for an understanding of gully network evolution and reorganization process in the Loess Plateau, which also contribute to the development of a process-based gully evolution model.

Key words: Loess Plateau ; Gully Network ; Geomorphologic Evolution ; Digital Terrain Analysis

How to cite: Chen, S. and Xiong, L.: Interaction and Reorganization of Loess Gully Network Evolution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2079, https://doi.org/10.5194/egusphere-egu2020-2079, 2020.

Longitudinal river profiles have been a central if not even the most important subject in tectonic geomorphology since the 1950s. During the last decades, considerable progress has been made in unraveling the tectonic history from river profiles. Going along with the rapidly increasing availability of DEMs, however, scientists try to derive more and more information from the topography. So the quality of the DEM is still a limiting factor in many studies. In particular, local channel slopes are strongly affected by the DEM. Several approaches have been proposed in order to reduce the errors and to distinguish specific features such as knickpoints from noise of the DEM.

In this study we use DEMs with a mesh width of 1 m obtained from airborne laser scans and reduce their resolution artificially in order to analyze the effect of the mesh width on the accuracy of river profiles systematically. Based on the results, we present an idea how the errors in channel slope could be reduced with focus on narrow valleys. Going beyond the majority of the previously published approaches, our idea does not only take into account the elevation along the river profile, but also the curvature of the topography in direction normal to the valley floor.

How to cite: Hergarten, S. and Robl, J.: River profiles from digital elevation models – limitations and new ideas, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3015, https://doi.org/10.5194/egusphere-egu2020-3015, 2020.

Detailed information on rock formations and assessment of their geological structures, such as joints, faults, shears and bedding planes, are required for evaluation of rock integrity and stability. Our research demonstrates a comprehensive approach for producing high spatial resolution 3D information of rock formations from unmanned aerial vehicle (UAV) imagery for rock joint identification, and presents an innovative technique for using Terrestrial Laser Scanning (TLS) data to derive ground control points (GCPs) for geo-referencing of UAV imagery of vertical rock walls. UAV imagery was collected from a freestanding 90 m tall rock formation with a 3.5 km perimeter, via oblique rock façade scans and also at-nadir, covering a ground and rock facade area of approximately 0.32 and 0.25 km², respectively. Seventy-two GCPs were distributed around the rock for geo-referencing of the UAV imagery. As GCPs could not be deployed on vertical rock walls, a TLS system was used for identification of 93 distinct natural features as pseudo-GCPs on the rock walls. Forty scans were collected and geo-referenced from triplets of GCPs placed on the ground near the TLS system for each scan. A Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS) survey was performed on the GCPs, using a base station and a rover. Continuously Operating Reference Stations (CORS) data were used to fix the position of the base station and improve the absolute geometric position to an average and lowest accuracy of 3.3 and 18.6 mm for 177 GCPs. A total of 44 façade scans, as well as 14 low and 5 high altitude nadir-viewing UAV flights, were undertaken with a Zenmuse X3 RGB camera mounted to a DJI Matrice 100 platform, resulting in a collection of nearly 17,000 photos. The five high altitude flights were designed to include a larger area around the rock to incorporate additional GCPs, while the low altitude flights were to increase the spatial resolution of the imaged rock. Flight planning was undertaken with the Universal Ground Control Station Client application. Façade scans were flown horizontally and parallel to the rock walls at a distance of 20-30 m and at heights between 10-80 m with sidelaps >70% between horizontal flight lines and >80% forward overlap along flight lines. Façade scans were collected with a 4° viewing angle to ensure the base of the rock was included. The Agisoft MetaShape software was initially used to generate a sparse point cloud using all façade scans and nadir-viewing imagery. Geo-referencing of the UAV imagery was based on 136 GCPs, which produced an accuracy of 0.1558 m, with an addition 100 control points kept aside for independent evaluation, yielding an accuracy of 0.2018 m. Subsequent image processing was split into 14 evenly sized “chunks” to enable more efficient processing of a dense point cloud (4.33 billion points) and 3D model (mesh with 129.5 million faces and texture layer) for the entire area. The produced 3D model was found suitable for identification of rock joints larger than 1 m in length.

How to cite: Johansen, K., Tu, Y.-H., Ziliani, M., Aragon, B., Angel, Y., Stutsel, B., Al-Mashharawi, S., Lopez, O., and McCabe, M.: 3D Mapping of Rock Formations from Oblique and Nadir Viewing UAV Imagery, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4068, https://doi.org/10.5194/egusphere-egu2020-4068, 2020.

In 2020 we celebrate the 40^th anniversary of the seminal works of Wood (1980a,b) who was one of the first researchers who considered the shapes of volcanoes in a global point of view. These four decades have seen a number of new approaches that were made possible by the ever increasing computer power and the improvements in Digital Terrain Model (DTM) production. The improving resolution and accuracy of the DTMs of various volcanic fields (VF) opened the way of wide variations of volcanic geomorphometric considerations. However, the differences in approach and, even more importantly, the differences in DTM production technology and resolution make the comparative studies and especially global considerations very difficult.

We have envisioned a global geomorphometric analytical methodology to analyse cinder cone morphometry in terms of shape versus age: The aim is to establish a relationship between the age of scoria cones age and their morphometry. This is knowingly a rather difficult undertaking and we have made only the first steps yet, but our methodological advancements are always developed with this demand in mind.

For the sake of diversity, in the current study four volcanic areas were considered with different age ranges, four different resolution DEMs and different number of cones:  San Francisco Volcanic Field, Arizona, USA (SFVF, 30 m horizontal resolution, 313 pcs), the Chaîne des Puys, France (CdP,  0.5 m, 26 pcs), the central-eastern part of the Sierra Chichinautzin, Mexico (SCVF, 5 m, 152 pcs) and Kula Volcanic Field, Turkey (KVF, 12.5 m, 64 pcs). As age data we had either age ranges or measured ages of the individual cones.

A great number of derivatives (mostly related to slope angles) have been calculated for the individual cones. Their most important statistics and their distribution were computed. Irregularities and, especially, cone degradation modify the original statistical distribution; these distributions can be compared in statistical way. A quantitative distance (metric) has been introduced to study the similarity or dissimilarity of the cones.

For the comparison, we have grouped the cones in several ways – they have been observed individually, by areas and by age groups (based on previous researches). For every cone boxplot diagrams, histograms and cumulative histograms were made to detect differences together with average and median values. These age groups were subjects of the Mann – Whitney statistical test to discriminate statistically independent or dependent samples in the populations. The test showed some clear relations between erosion (shape) and age.

We created a cinder cone viewer for visualization purposes. This tool can display the aforementioned distributions and helps in picking pairs or groups of cinder cones to compare. As expected, the intra-VF comparisons are typically more successful as inter-VF comparisons. However, promising new morphometric derivatives (e.g., sectorial distributions) are under development.

Wood, C. A.: Morphometric evolution of cinder cones, J. Volcanol. Geoth. Res., 7, 387–413, 1980a.

Wood, C. A.: Morphometric analysis of cinder cone degradation, J. Volcanol. Geoth. Res., 8, 137–160, 1980b.

How to cite: Székely, B. and Vörös, F.: Studying the distributions of DTM derivatives of cinder cones: a statistical approach in volcanic morphometry, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10465, https://doi.org/10.5194/egusphere-egu2020-10465, 2020.

Landform classification is one of the most important aspects in geomorphological research, dividing the Earth’s surface into diverse geomorphological types. Thus, an accurate classification of landforms is a key procedure in describing the topographic characteristics of a given area and understanding their inner geomorphological formation processes. However, landform types are not always independent of one another due to the complexity and dynamics of interior and external forces. Furthermore, transitional landforms with gradually changing surface morphologies are widely distributed on the Earth’s surface. With this situation, classifying these complex and transitional landforms with traditional landform classification methods is hard. In this study, a deep learning (DL) algorithm was introduced, aiming at automatically classifying complex and transitional landforms. This algorithm was trained to learn and extract landform features from integrated data sources. These integrated data sources contain different combinations of imagery, digital elevation models (DEMs), and terrain derivatives. The Loess Plateau in China, which contains complex and transitional loess landforms, was selected as the study area for data training. In addition, two sample areas in the Loess Plateau with complex and transitional loess hill and ridge landforms were used to validate the classified landform types by using the proposed DL method. Meanwhile, a comparative analysis between the proposed DL and random forest (RF) methods was also conducted to investigate their capabilities in landform classification. The proposed DL approach can achieve the highest landform classification accuracy of 87% in the transitional area with data combination of DEMs and images. In addition, the proposed DL method can achieve a higher accuracy of landform classification with better defined landform boundaries compared to the RF method. The classified loess landforms indicate the different landform development stages in this area. Finally, the proposed DL method can be extended to other landform areas for classifying their complex and transitional landforms.

How to cite: Li, S., Xiong, L., Tang, G., and Strobl, J.: Deep learning-based approach for landform classification from integrated data sources of digital elevation model and imagery, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22334, https://doi.org/10.5194/egusphere-egu2020-22334, 2020.

The Tor Exhumation Approach (TEA) traditionally uses large residual granitic landforms as indicators for surface lowering over time of their surrounding landscape. This study challenged the broad applicability of this approach by using large metamorphic residual landforms instead of the traditional plutonic rock formations. We applied in-situ cosmogenic nuclide techniques (¹⁰Be) along vertical landforms (schist-tors) on the Otago upland in southern New Zealand to investigate the capabilities of the TEA within another major rock type. The aim of the investigation was to decipher surface denudation models for the last ~100 ka. The experiment was coupled with fallout radionuclides (^239+240Pu) in nearby soils to compare the Pleistocene / Holocene surface denudation rates with the Anthropocene (last ~60 years).

The surface ages of the eight investigated schist-tors was between ~20 ka and ~300 ka. This allowed the numerical modeling of continuous surface denudation rates with highest values near 0.16-0.20 [mm year^-1] (about 140–180 [t km^-2year^-1]), and over a period that has not yet been achieved. The fallout radionuclide study resulted in two different mass redistribution rates. Average soil erosion along a ridge was ~400 to ~850 [t km^-2year^-1], whereas in an adjacent valley soil deposition rates reached ~130 to ~1,500 [t km^-2year^-1]. In conclusion, this study provides a new basis on how schist-tors emerge at two different landscape positions (ridges and valleys). In addition, differences between past surface denudation rates and modern ones could be revealed.

How to cite: Raab, G., Scarciglia, F., Norton, K., Martin, A., Christl, M., Ketterer, M., and Egli, M.: Surface denudation and soil erosion over 300 ka at the Otago upland (New Zealand) using 10Be and 239+240Pu, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2911, https://doi.org/10.5194/egusphere-egu2020-2911, 2020.

A coupled accelerator mass spectrometer - gas interface system successfully has been operating at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary since 2013. Over the last 6 years more than 500 gas targets were measured below 100 µg carbon content for carbon isotopic composition. The system was tested with blanks, OxII, IAEA-C1, IAEA-C2 and IAEA-C7 standards. The performance of our instrumentation shows good agreement with other published gas-interface system data and also shows a quite good agreement with the nominal value of international standard samples.  There is a measurable but quite small memory effect after modern samples, but this does not significantly affect the final results. Typical ion currents at the low energy side were between 10-15 µA with a 5% CO₂ in He mixing ratio. The relative errors average ±6% for samples greater than or equal to 10 µgC sample with mean count rates of 300 counts per microgram C for OxII. The blank is comparable with other systems, which is 0.0050 ± 0.0018 F¹⁴C or 34000-47000 yr BP, which allows for the routine measurement of both of small environmental and archeological samples.

The research was supported by the European Union and the State of Hungary, co-financed by the European Regional Development Fund in the project of GINOP-2.3.2-15-2016- 00009 “ICER”. This work was carried out in the frame of the János Bolyai Research Scholarship (Mihály Molnár) of the Hungarian Academy of Sciences

How to cite: Molnár, M., Janovics, R., Major, I., Hubay, K., Buró, B., Varga, T., Kertész, T., Gergely, V., Veres, M., and Jull, A. J. T.: EnvironMICADAS C-14 AMS Gas ion source performance and its applications at HEKAL Laboratory, Debrecen, Hungary, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9577, https://doi.org/10.5194/egusphere-egu2020-9577, 2020.

Interpretations of surface exposure ages derived from the accumulation of cosmogenic isotopes commonly are hampered by a lack of field documentation that is necessary to identify and constrain if any post-depositional surface modifications have occurred (e.g. surface erosion, burial) that will impact age interpretations. Previous authors have discussed these issues, but the community still has not fully adopted the practice of interpreting surface exposure ages in conjunction with detailed soil stratigraphic observations. We employ this “novel” approach by documenting a soil chronosequence from the Gould wash alluvial fan sequence near Cibola, AZ to demonstrate how soil stratigraphy can provide constraints for the relative stability of depositional surfaces and can influence interpretations of TCN ages.

The Cibola chronosequence represents a range of alluvial fan ages that extend well beyond those commonly observed in the desert southwestern US (typically <100 ka) and provides evidence for extended periods of surface stability. We identified seven different alluvial fan surfaces within the sequence, documented their soil morphological and chemical properties, and dated four of the fan surfaces with ³⁶Cl depth profiles. Fan deposits largely consist of volcaniclastic alluvium derived from the local Trigo Peaks and distal Castle Dome mountain blocks and show both a reduction of bar-and-swale surface topography and an increasing expression of desert pavement with relative surface age. The soil profiles consist of Av-Bk-BCky-Cky-Ck vertical horizon sequences (~125-cm thick) in the youngest fan units to Avk-Btky-Bkym-Bky-BCky-Cky-C (~400-cm thick) in the oldest fan unit that reflect systematic changes in soil thickness, structure, rubification of B horizons, and relative accumulations of eolian derived silt, clay, and salts as a function of relative surface age.

Chlorine-36 depth profile analysis yielded variable fan ages that are largely controlled by the magnitude of allowable erosion. Model results for which input data were parameterized to optimize unconstrained erosion rates indicate surface exposure ages of 46 (2A), 114 (2B), 268 (3A), and 386 (4A) ka. These are associated with best-fit erosion rates of 0-6 mm/kyr that indicate 0-136 cm net erosion. By comparison, results for which erosion rates were constrained to ~1 mm/kyr based on soil stratigraphic observations yielded exposure ages of 41 (2A), 114 (2B), 209 (3A), and 287 (4A) ka, resulting in differences of 10-25% of the unconstrained ages. The systematic morphological trends observed in the soil profiles do not support inferences of net erosion exceeding 30 cm and therefore cannot support the results from unconstrained parameter optimization. Although statistical optimization schemes provide better model fits to the data as indicated by chi-shared minimization routines, current models cannot account for field observations or for inferred constraints on surface modifications based on cosmogenic isotope concentrations alone. That task is better suited for and required by the sampling protocol to achieve more reliable surface exposure dates.

How to cite: Sion, B., McDonald, E., and Bustarde, J.: Using Soil stratigraphic observations to constrain TCN depth profile ages of relict alluvial fan surfaces in the Sonoran Desert, USA, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10614, https://doi.org/10.5194/egusphere-egu2020-10614, 2020.

Understanding the degree of sensitivity of the Earth Surface to past climate changes is key to assess the strength of postulated links between weathering, denudation, rock uplift and climate. Numerous studies have investigated the response of surface processes to the evolution through time of temperature and precipitation, in various settings and over different time periods. In particular, an important question still actively debated concerns whether or not Late Cenozoic climate change had an effective impact on denudation rates. It is noteworthy that this Late Cenozoic climatic evolution is often described as a long-term cooling over several Ma. However, although it has been postulated to be an important control on this response, the impact of its orbitally-controlled high-frequency component has been less investigated.

Studies focusing on climate-denudation links have often been carried out in regions of high tectonic activity. Therefore, they encountered associated significant limitations, such as: (1) high denudation rates that reach the analytical limits of many measurement methods; (2) stochastic events introducing a high degree of variability in the denudation signal; and, (3) high rates of tectonic uplift that can limit the sensitivity to the low-frequency component of the climatic boundary condition. Less active tectonic settings with lower denudation rates may thus provide conditions allowing to focus specifically on the coupling between climate variations and surface processes. Additionally, approaches combining different cosmogenic nuclides have proven to be very effective to unravel changes in surface processes over several time scales.

We present a new cosmogenic nuclides dataset from the Sera do Cipo range in Minas Gerais, Brazil. The core of the range is made of resistant quarzite bedrock with a relief of 500 m with respect to the surrounding low lands, and reported denudation rates are <10 m/Ma. Streams sediments from small catchments near the summit divide, as well as clasts derived from massive quartz veins at hilltop locations, were sampled. Both ¹⁰Be and ²⁶Al concentrations were measured in the collected samples, as in such slow denudation settings the ratio between the two nuclides is sensitive to changes in denudation rates through time. A high-resolution (1 m) Digital Elevation Models was also produced from tri-stereo Pléiades satellite images. This allows to compute high resolution metrics such as hilltop curvature at the sampling sites. Hilltop denudation rates display a strong positive correlation with curvature. ²⁶Al/¹⁰Be values significantly departing from the theoretical steady state denudation ratio are interpreted at hilltop sites as reflecting the fluctuation of denudation through time. Concerning the catchments samples, the determined ratio can also be impacted by the sediment transport history along hillslopes. Combining cosmogenic nuclides and high-resolution topographic datasets, the measured concentrations were inverted to constrain the variation of denudation over the last 2 Ma. We observe a significant change in the denudation regime at 1 Ma, with different kind of responses between ridges and small catchments across the landscape.

How to cite: Godard, V., Salgado, A., Siame, L., Fleury, J., and Aster, T.: Temporal evolution of surface processes inferred from cosmogenic nuclides in a slow erosion setting, insights from the Sera do Cipo range, Brazil, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9427, https://doi.org/10.5194/egusphere-egu2020-9427, 2020.

Timothée Jautzy^1,2, Dominik Brill³, Laurent Schmitt¹, Gilles Rixhon⁴

Obtaining robust chronological data on landforms and their related deposits together with constraining rates of earth surface processes have constantly represented a major challenge in Quaternary science. In the fluvial context, Optically Stimulated Luminescence (OSL) is particularly well-established but still faces several limitations. It notably requires expensive and time-consuming sample processing and measurement, frequently resulting in a poor spatial and stratigraphical distribution of sampling which may negatively impact the chronological information. To overcome this main limitation, a Portable OSL reader (POSL) has been recently developed (Sanderson & Murphy, 2010). It consists in directly capturing a luminescence signal (counts per seconds) on unprepared sediment samples. This technique is quick and affordable but, unlike conventional OSL, is not able to yield numerical age estimates.

This contribution explores POSL capacities to provide useful relative age information on alluvial sediments from the last centuries. We study and compare 42 samples collected from three alluvial profiles located in the floodplain of a gravelly-sandy mid-sized river: the Bruche (i.e. a sub-tributary of the Upper Rhine, France). POSL stimulations, including both blue and infra-red signals, are performed in combination with grain size analysis. We observe (i) an overall increase of signal intensity with increasing depth, (ii) a very good match between blue and IR signals and (iii) no systematic correlation between signal intensity and grain size. Whilst this last point must still be confirmed (i.e. signal intensity does not primarily depend on grain size), our preliminary results positively suggest that POSL is a promising tool to provide a relative chronology for very young alluvial sediments. Furthermore, it may also provide information on geomorphic processes. These results will be combined soon to numerical dating (OSL and ¹⁴C) and compared to outcomes of a planimetric analysis to thoroughly reconstruct the historical lateral mobility of the Bruche river.

How to cite: Schmitt, L., Jautzy, T., Brill, D., and Rixhon, G.: Using the portable luminescence reader to assess the historical lateral mobility of river channels: preliminary promising results, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19218, https://doi.org/10.5194/egusphere-egu2020-19218, 2020.

For a better understanding of the recent exhumation history of the Alps and the distribution of palaeo- and recent earthquakes within the orogen, it is important to elucidate the Quaternary activity of major faults. In this study, we test the applicability of luminescence and electron spin resonance (ESR) dating, which have ultralow closure temperatures, to directly date fault gouge of the Simplon Fault. A dark grey to black, fine-grained fault gouge was sampled near Visp, Switzerland, from an outcrop that exposes rocks that formed at ductile/brittle conditions. Quartz and feldspar grains were extracted from the sample; quartz grains were used for ESR dating, whereas feldspar grains were used for infrared stimulated luminescence (IRSL) dating.

The IRSL measurements reveal that the natural post-IR IRSL signal, stimulated at 225°C (pIRIR₂₂₅) was in saturation. The pIRIR₂₂₅ signal had an extremely low saturation dose, with a characteristic saturation dose (D₀) of ~90 Gy. The natural IRSL signal at 50°C (IR₅₀) is about 80 % of the laboratory saturation, so that this signal is presumably in the field saturation. The IR₅₀ also showed a small D₀ of ~250 Gy. Although these D₀ values are unexpectedly small, the IRSL signals can be used to calculate the minimum age of the last seismic movement of the fault.

Both natural and laboratory-irradiated ESR spectra did not contain detectable Ti centre. Therefore, only the Al centre was used for ESR dating. The natural Al centre from the fault was not in saturation, with a preliminary equivalent dose value of ~1500 Gy. Since the last seismogenic movement most likely only partially reset the Al centre, the ESR age can be regarded as the maximum age of the last event.  We show that by combining luminescence and ESR dating, it is possible to narrow down the age range of the last seismic activity on the fault.

How to cite: Tsukamoto, S., Tanner, D., Brandes, C., and von Hagke, C.: Testing direct dating of Alpine faults by luminescence and ESR, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7982, https://doi.org/10.5194/egusphere-egu2020-7982, 2020.

Dating of loess deposits using optically stimulated luminescence (OSL) enable us to extract important information about the climate during the last ~150 ka. A good estimation of the dose rate during the past is essential for OSL and depends, among others, on the history of the moisture content in the proximity of the dated sample. While the current moisture content can be measured by heating/drying, the history of the moisture variations of a sample is generally unknown. Reference values reported on similar materials and climate conditions may provide a range for the expected moisture variations in the past, but these values are generally rough guesses and not depth- and time-specific.

Nuclear magnetic resonance (NMR) relaxometry targeting the hydrogens of the pore fluid can estimate the current moisture content of a sample without heating. Additionally, the NMR relaxation time distribution yields information of the expected moisture content for a given field potential (e.g. wilting point). This can help to estimate a sample-specific range of likely moisture variation in a quick (several min) and no-invasive way.

We discuss this new approach on a loess profile from Toshan (Iran) published previously by (Lauer et al., 2017) and (Vlaminck, 2018). The later pointed out inconsistencies in the obtained age model. The estimated sample specific moisture content for the wilting point (15 to 35 wt.%) provide the low boundary for the moisture content estimate, which is higher than previously assumed (5 wt.%). The new dose rate calculated for these sample specific moisture content values lead to clearly older and more consistent ages (less age inversions).

We suggest that NMR derived moisture content data is valuable for obtaining information on the moisture content of samples. Especially the minimum moisture can be derived reliably, giving more robust water content estimates for OSL dating.

References

Lauer, T., Vlaminck, S., Frechen, M., Rolf, C., Kehl, M., Sharifi, J., Lehndorff, E., Khormali, F., 2017. The Agh Band loess-palaeosol sequence – A terrestrial archive for climatic shifts during the last and penultimate glacial–interglacial cycles in a semiarid region in northern Iran. Quaternary International, Loess, soils and climate change in Iran and vicinity 429, 13–30. https://doi.org/10.1016/j.quaint.2016.01.062

Vlaminck, S., 2018. Northeastern Iranian loess and its palaeoclimatic implications (PhD Thesis). Universität zu Köln.

How to cite: Dlugosch, R., Zeeden, C., Lauer, T., and Tsukamoto, S.: Can moisture content estimates from nuclear magnetic resonance improve optically stimulated luminescence dating - first results on Loess samples from Toshan/Iran, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1493, https://doi.org/10.5194/egusphere-egu2020-1493, 2020.

The sediment rooting concept [1] relies on the potential to track individual mineral grains from their source to their ultimate sinks. Quartz is the second most abundant mineral in the Earth's crust and occurs in a broad variety of rocks and sediments. It is resistant to weathering and does not form solid solutions, thus being considered a pure mineral. However, even the purest quartz crystal contains a vast number of point defects, which may be either intrinsic (e.g., O-vacancies and related defects or Si vacancies) or due to impurities, most often as combination of monovalent (H⁺, Li⁺, and Na⁺) and trivalent (Al³⁺, Fe³⁺, and B³⁺) cations. Some of these defects remain unchanged under ionising radiation bombardment by the omnipresent natural radioactivity, while others are being transformed, generally by charge trapping. Based on the dynamics of some of these radiation sensitive defects under irradiation, quartz can be used for dating by luminescence or by electron spin resonance.

Another less explored application of these defects is fingerprinting the sources of the sediments. For provenance applications to be successful, the signals used when looking at quartz from the sediment should match the corresponding signals of quartz from host rocks, thus they should remain unchanged during transport and/or weathering.

Here we are conducting an exploratory study on quartz from loess from Central Asia (Kazakhstan and Tajikistan). This specific study site was chosen as very recent studies based on geochemical fingerprinting, grain size modelling and present-day meteorological data suggest contribution from different source areas in this Westerlies dominated region [2,3]. Consequently, this area is an ideal test site to look for spatial and temporal variability in source change. We are investigating the signature of E’ (an unpaired electron at an oxygen vacancy site) and peroxy intrinsic defect centers (nonbonding oxygen) as well as the Al-hole ([AlO₄]⁰, a hole trapped by substitutional trivalent aluminum at a silicon site) paramagnetic signals by electron spin resonance in loess samples, as well as in rock samples. We are also investigating the behaviour of these defects during laboratory experiments that aim at reproducing natural conditions during transport. While work is still in progress, we have observed a significant difference between the E’ and peroxy signals for Kazakh and Tajik samples, which is in tune with the current hypothesis regarding the dust sources in the area presented above.

References

How to cite: Timar-Gabor, A., Dave, A., and Fitzsimmons, K.: Investigations on paramagnetic centres in quartz for provenance studies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5889, https://doi.org/10.5194/egusphere-egu2020-5889, 2020.

This contribution investigates the use of the (U-Th-Sm)/He dating method to unravel the exhumation history of ultramafic ophiolite rocks. Magnetite-bearing rocks are widely distributed on the Earth's surface and are associated with a large range of geological and geodynamic settings. However, little is known of the crystallization and exhumation history of in case of oceanic accretion to orogenic zones, due to a lack of datable minerals. In the past few years, the (U-Th-Sm)/He method applied on magnetite or spinel appears to be very relevant and promising. However, the applicability of this method to access the thermal history has never been quantitatively investigated, limiting the age interpretation. To highlight the applicability and to access geological information using magnetite (U-Th-Sm)/He method (MgHe), we applied it on a well-known high-pressure low-temperature alpine ophiolite (Rocher Blanc ophiolite, Western Alps) where the P-T-t exhumation history is well constrained. A study of magnetite petrology, mineralogy and geochemistry has allowed us to characterize that magnetite crystallize at T>250°C. MgHe ages that range between apatite and zircon fission track (AFT and ZFT) ages of surrounding rocks in agreement with the known thermal sensitivity of those methods. MgHe data were co-inverted with AFT and ZFT data to determine the most robust thermal history associated with the ophiolite cooling. This first MgHe age inversion is consistent with experimental He diffusion data, opening the use of MgHe as a thermochronometer. This result allows us to refine the thermal history and to precise the geodynamical context associated to the final exhumation of this alpine ophiolite.

How to cite: Schwartz, S., Gautheron, C., Ketcham, R. A., Brunet, F., Agranier, A., and Corre, M.: Contribution of magnetite (U-Th-Sm)/He thermometer to quantify the final exhumation of high-pressure ultramafic rocks : example of the Rocher Blanc ophiolite (western Alps), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4505, https://doi.org/10.5194/egusphere-egu2020-4505, 2020.

The Cenozoic growth of the Ecuadorian Andes has been strongly influenced by the compressional reactivation of inherited crustal anisotropies, strike-slip faulting and uplift, and the erosional effects of a wet tropical climate superposed on the deforming orogen. Some authors have linked uplift in the Western Cordillera to the interaction between the South American Plate and the subduction of the oceanic Carnegie Ridge. However, recent studies have alternatively suggested that the tectonic evolution of a northward-escaping crustal sliver in western Ecuador along the Pallatanga strike-slip zone may equally well explain mountain building and topographic growth in this region. While the importance of the Pallatanga Fault has been recognized in the context of seismic hazards, its long-term impact on the development of topography and relief has not been explored in detail. To evaluate the possible roles of oceanic ridge subduction and/or strike-slip motion in prompting the growth of the Western Cordillera, we present new thermochronological data to constrain the deformational history of the Western Cordillera at different latitudes. We focus on two sites in the vicinity of the Pallatanga strike-slip fault (3°S and 1°30’S) and a location farther to the north (0°30’N). Our apatite and zircon (U-Th-Sm)/He dates range from 26.0 ± 0.4 Ma to 3.9 ± 0.1 Ma and from 23.7 ± 0.3 to 5.9 ± 0.1 Ma, respectively. The three sampled sites record a clear age-elevation relationship. The inverse modeling of apatite and zircon (U-Th-Sm)/He dates and upcoming apatite fission-track data is expected to provide new constraints on the recent uplift and exhumation history of the Western Ecuadorian Andes and thus furnish information on the paleo-geographical evolution of the northern Andes.

How to cite: Margirier, A., Reiners, P., Casado, I., Thomson, S., Alvarado, A., and Strecker, M.: Uplift history of the Western Ecuadorian Andes: new constraints from low-temperature thermochronology, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5228, https://doi.org/10.5194/egusphere-egu2020-5228, 2020.

Foreland basins represent a unique record of the evolution of mountain building processes in the adjacent hinterland. In the southern Colombian Andes and the adjacent foreland basin (i.e. Caguán-Putumayo Basin) no detrital U-Pb and heavy mineral studies have been conducted. This is due to the fact that the geochronological characterization of the basement rocks is poor, complicating the interpretation of source areas for provenance analysis.  Here we present a complete provenance study using U-Pb and Heavy mineral data. In order to gain a better understanding of the spatial distribution of the different potential basement sources we planned a characterization of the different basement provinces west of the Caguan-Putumayo basin. Here we present results from samples of active sediments (N=21), basements (N=16) and sedimentary rocks (N=4) older than Cretaceous. This characterization allowed the identification of eight (8) different domains with different age ranges. (1) The southern part of the Central Cordillera with populations of 150 - 250 m.y., (2) Southern part of the eastern flank of the Eastern Cordillera with ages around 150 - 180 m.y., (3) south of the Garzón Massif with age ranges between 1000 - 1150 m.y, (4) north of the Garzón Massif where rocks of 1500 m.y. dominate, (5) Paleozoic sedimentary rocks above the basement to the north of the Garzón Massif and the Serrania de la Macarena with a distinct population of 1300 m.y, (6). The basement of the Serrania de la Macarena with ages between 1650-1800 m, (7). The Serranía de Lindosa with ages around 500 m.y and (8). Amazonian Craton with ages between 1500 - 2000 m.y. Additionally, the relationship between Epidotes and Garnets displays a special behavior in each area. The provinces related to the Garzon Massif have a high amount of Garnets and low amount of Epidotes. On the other hand, the behavior of the areas away from the Garzon Massif is different. Based on the U-Pb detrital signal and the Epidote/Garnet relationship, we suggest that the stratigraphic intervals where we observe ages between 1000 and 1150 m.y. for the first time and high Garnet contents reflect uplift peaks of the Garzon Massif.

How to cite: Sandoval, J. R., Perez-Consuegra, N., Gomez, R. A., Mora, A., Parra, M., Valencia, V., Horton, B., Bueno, R., Reyes, A., Beltran, A., and Cardenas, A.: Spatial distribution of U-Pb ages across a basement uplift in the Northern Andes and its implications for the interpretation of the detrital record in adjacent basins., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12624, https://doi.org/10.5194/egusphere-egu2020-12624, 2020.

Detecting seismic signals and identifying their origin is more and more used for understanding environmental activity. This usually depends on a good signal/noise ratio (S/N), especially for the more distant sources.

A test area for detection and identification is the urban setting of the University of Vienna, a challenging environment with more than 4000 strong-acceleration events per day. These repetitive noise events would normally classify the site as "too noisy" for any advanced earthquake research.

With the real-time open database from Wiener Linien it is possible to attribute many of the repetitive seismic signals (e.g. on a Raspberry Shake Citizen Science Station) to the surrounding trams and train lines. The detection challenge was initiated in a Citizen Science Hackathon, where public interest sparked this research. The available train schedule and more than one year of continuous seismic records is sufficient to train and test a machine learning classifier which finds most characteristic features in the signals of commuter trains and trams, such as the energy in each frequency band.

The labeled dataset can be used to train our detection algorithm to find similar signals and to help determine whether a certain signal is present or not. An additional second seismic Raspberry Shake sensor is installed in the vicinity, to further constrain the directionality of the trains.

Studying the vibrations of train signals and solving the classification task of these repetitive patterns first can help develop robust methods
for seismically loud environments, and might lead to the detection of lower magnitude events such as regional earthquakes or landslides. 

How to cite: Hein, G., Novoselov, A., Fuchs, F., and Bokelmann, G.: Matching seismic activity with potential sources using machine Learning , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1519, https://doi.org/10.5194/egusphere-egu2020-1519, 2020.

Runoff-generated debris flow has hazardous implications for downstream communities and infrastructure in alpine landscapes. Our understanding of fluid mechanisms of debris flows is very limited, in part, by a lack of direct observations and measurements. Seismic ground motion-based observations provide new constraints on debris flow physics, but it is still not widely applied due to the missing of validated inversion models for interpreting the impact force which generates seismic ground motion. Here we propose a physical model for the high-frequency spectral distribution of impact force signal generated by debris flows. Then we present a new inversion model based on the physical model for the impact force signal and apply this to the devastating debris flows in Dongchuang, China, on 25 August 2004. The amplitude and frequency characteristics of the impact force data can enable the estimation of grain size, sediment concentration, and sediment flux. Results suggest that in-situ data from three sensors could have provided a reconstruction of sediment flux profile in the vertical direction. Meanwhile, an inversion model designed for debris flows impact force would potentially provide hydrodynamics information as well.

How to cite: Tang, H., Yan, Y., and Hu, K.: Deriving sediment transport information from debris-flow impact force signals, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13054, https://doi.org/10.5194/egusphere-egu2020-13054, 2020.

Water is a critical resource that can range from being either available in short supply or excess, causing floods. In many locations the majority of this supply is underground. In some geological terrains such as karst these underground systems transport water primarily through crack or conduit flow. Determining the subsurface locations of the dominant flowing structures and their flow rates in such karst systems is a significant challenge. The details of these complex flow networks can, for example, have a first-order control on water supply, surface floods and the locations of seasonal lakes. Current geophysical methods focus on active geophysical imaging of karst structures but usually fail in determining if such structures are flowing. In this work, we take a different approach locating flowing conduits in Irish karst via a multi-method analysis of ground vibrations from temporary deployments of passive seismic sensors. We start by testing the methodology on surface rivers.

Hydrological processes including turbulent water flow and sediment transport create ground vibrations that can be detected on seismic stations. In the initial test, we deployed two small aperture arrays of 4 and 6 three-component (3C) short-period seismometers and a short linear array beside a river with a typical flow rate of 25 m3/second. We see clear spectral peaks associated with water flow at frequencies of 10 to 40 Hz. We locate the sources for these frequency bands using both conventional beamforming array analysis and an Amplitude Source Location Method (ASLM). Before ASLM, we constrain the velocity based on array analysis. Both methodologies perform well in determining the known locations of rapid flow in the river. We then move to a test karst location where the subsurface pathways of large conduits are known through cave dives. We deploy 3C short period seismometers for a few hours. Again we see clear peaks in the seismic spectra which, using ASLM and Frequency-Dependent Polarization Analysis (FDPA), located close to the known conduits. In the station close to a known conduit, we see sustained very high-frequency signals which are in agreement with numerical simulation of crack dominated flow for secondary short narrow cracks. This work is the prelude to a larger seismic nodal deployment that will take place in the winter/spring of 2020 in the same location. Initial results from that experiment will also be presented.

How to cite: Karbala Ali, H., Bean, C., Craig, D., Li, K. L., O’Brien, G., Hickey, C., and O'Keeffe, B.: Tracking surface and subterranean water flow using continuous seismic tremor, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20833, https://doi.org/10.5194/egusphere-egu2020-20833, 2020.

How to cite: Wenner, M., Walter, F., Allstadt, K., McArdell, B., and Lockhart, A.: What ground tilt tells us about debris flow parameters, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-728, https://doi.org/10.5194/egusphere-egu2020-728, 2020.

The IRIS/PASSCAL Instrument Center is installing 5 seismic stations around the summit of Mt. Erebus, Antarctica. IRIS is funded by the National Science Foundation to install and maintain these stations long-term, a task undertaken by the Polar team at PASSCAL. The purpose of the network is to provide a baseline measurement of volcanic events and act as a fiducial array for future experiments. Each station’s instrument package comprises a data logger recording a broadband and strong-motion seismometer, and a separate data logger recording an infrasound sensor. Station state of health and near real-time data are transmitted via Iridium modems.

The Mt. Erebus network is installed between 2000 m and 3400 m elevation spaced around the volcano summit. This is a particularly harsh environment for operating autonomous seismic stations with extreme low temperatures and high winds. Station power systems need to have enough capacity to winter-over for roughly 6-months without recharge. Station enclosures need to provide sufficient insulation to keep the data logger within its temperature operating range.

To design these stations for long term, 365/24/7 operation, we leveraged proven station enclosure and power system designs developed over the last 12 years of PASSCAL engineering seismic systems for Antarctica. The Mt. Erebus station design is modular and standardized, separating the bulk of the power storage and electronics' enclosures, allowing for streamlined upgrades or additions without having to overhaul the entire station. Power for the system will rely on lead acid batteries and solar charging; forgoing higher efficiency primary lithium thionyl chloride batteries used elsewhere in Antarctica, to reduce long-term station costs.

Station health will be monitored at IRIS/PASSCAL and low sample rate (20 sps) broadband data will be captured in near-real time. Higher sample rate data are recorded locally and collected annually during the austral summer. All data will be available from the IRIS Data Management Center.

How to cite: Beaudoin, B., Arnell, K., Carpenter, P., Lingutla, N., Meyers, J., Nikolaus, K., and Roth, A.: Environmentally hardened, high-altitude, high-latitude seismic stations on Mt. Erebus, Antarctica, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1950, https://doi.org/10.5194/egusphere-egu2020-1950, 2020.

Southeastern Mongolia has limited access due to its extreme environments (long and harsh winter) and lack of infrastructure (e.g., road). Satellite remote sensing technique is one of the most effective methods to get geological information in areas where field survey is difficult. WorldView-3 (WV3), launched in August 2014, is high-spatial resolution commercial multispectral sensor developed by DigitalGlobe. WV3 measures reflected radiation in eight visible near infrared (VNIR) bands between 0.42 and 1.04 ㎛ and in eight short-wave infrared (SWIR) bands between 1.20 and 2.33, which have 1.24- and 7.5-m spatial resolution, respectively. In this study, WV3 VNIR and SWIR data were used to identify and map the various minerals in the Ikh Shankhai porphyry Cu deposit district, Mongolia.

The Ikh-Shankhai porphyry Cu deposit is located within Gurvansayhan island arc terrane in southeastern (SE) Gobi mineral belt, Mongolia. The Ikh-Shankhai district include the porphyry system containing Cu-Au with primary chalcopyrite, which is classified into disseminated type and stockwork quartz type. This district consists of Late Devonian-Early Carboniferous andesite, tuff and siltstone intruded by Carboniferous-Permian granite, granodiorite and granodiorite porphyry.

The WV 3 data were analyzed using mixture-tuned-matched filter (MTMF) which locates a known spectral signature in the presence of a mixed or unknown background. MTMF does not require knowledge of all of the spectral endmembers and is suited for used where materials with distinct spectral signatures occur within a single pixel. From the WV3 analysis result using mixture-tuned-matched filter (MTMF), we identified the location and abundance of alteration minerals. Advanced argillic minerals (alunite, kaolinite (or dickite), and pyrophyllite) were dominant in the lithocaps of the Budgat and Gashuun Khudag prospects; whereas, phyllic (illite) and propylitic (calcite and epidote) minerals were dominant in the areas surrounding the lithocaps. In addition, the distribution of ferric minerals (hematite and goethite) was mapped because of the oxidation of pyrite. Field work at the Ikh-Shankhai porphyry Cu district to evaluate the accuracy of the mineral mapping results was carried out in August, 2018. Reflectance spectra acquisition using a portable ASD TerraSpec Halo mineral identifier (the attached GPS covered a spectral range of 0.35 – 2.5 µm) was conducted in the altered outcrops of the Ikh-Shankhai porphyry Cu district. Mineral mapping results compared well with the field spectral measurements collected for the ground truth and demonstrated WV3 capability for identifying and mapping minerals associated with hydrothermal alteration. Evaluation of the WV3 mineral mapping results using ground truth data indicates, however, a difficulty in mapping spectrally similar minerals (e.g., kaolinite and dickite) due to spectral resolution limitation.

How to cite: Youngsun, S. and Kwang-Eun, K.: Mineral mapping at the Ikh Shankhai porphyry Cu deposits, Mongolia using WorldView-3 data, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2359, https://doi.org/10.5194/egusphere-egu2020-2359, 2020.

Following the large June 17 2017 landslide in Karrat Isfjord, Central West Greenland the necessity to differentiate between different kinds of seismological events has become relevant for hazard assessment. Greenland is the origin of a many different kinds of seismic signals.  In addition to the than a thousand small to moderate magnitude tectonic earthquakes, most of them ranging between ML 1.0 and 3.0 are located along the coasts of Greenland every year, many other non-tectonic events are located. This is largely possible thanks to the data collected and distributed by the Greenland Ice Sheet Monitoring Network (GLISN) federation and its members (glisn.info). The non-tectonic events include cryo-generated events, and signals from landslides as for example illustrated by the globally seen seismological signal from the Karrat 2017 landslide. It is possible to separate tectonic events from non-tectonic events, based on the characteristics of the seismological signal alone, but the signals from cryo-generated events and landslides have many similar features. In the Karrat Isfjord area, several large glaciers terminate in the sea where for example calving generate seismological events. With poor location resolution due to large station spacing in the remote areas of Greenland, the differences in the seismological signals are important to determine the cause of the events.

How to cite: Dahl-Jensen, T., Larsen, T. B., and Voss, P. H.: Non-tectonic seismological events in Greenland - Cryo-generated events and landslides, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6680, https://doi.org/10.5194/egusphere-egu2020-6680, 2020.

Rock falls are important agents of erosion shaping the topography of bedrock slopes. Despite the considerable attention rock falls get when causing damage we still lack detailed information about the triggers, lag times, seasonal and elevation-dependent rock fall occurrence. This is due to the difficulty in observing rockfalls directly as the mobilisation of rock masses occurs rapidly, infrequently and distributed at a priori unknown locations. To identify seasonal and elevation-dependent rock fall activities and characteristics and their environmental drivers and triggers in an alpine setting, we have operated a monitoring network to detect and classify rock falls in the Reintal valley, German Alps, since 2014. The Reintal is an Alpine valley in the Wetterstein massif close to the Zugspitze, Germany’s highest mountain. The Reintal observatory produces nearly continuous datasets of seismic, meteorological and camera data. To our knowledge, these datasets are one of a few that permit a systematic study of rockfall patterns and their controls over a period of several years in an alpine setting.

In this contribution, we present the layout of the observatory and the instrumental network. Six seismometers record the motion of the ground; different types of seismic signals are shown and their sources discussed. This is done in combination with the meteorological data of the two weather stations in the valley and the images of the optical and infrared cameras of the observatory. We evaluate the performance, limitations and capabilities of the observatory. In addition, we discuss how we dealt with challenges such as power consumption of the instruments in the field, data storage and data loss. Our experience with the set-up and maintenance of the observatory can help guide the design and construction of other observatories in mountain environments.

How to cite: Schöpa, A., Hovius, N., and Turowski, J.: Set-up and performance evaluation of a seismic rock fall observatory in the Alps, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14290, https://doi.org/10.5194/egusphere-egu2020-14290, 2020.

Here, we present data from lahars through the use of a 3-component broadband seismometer, accelerometer, and a video camera installed 3 m from the Lumbre channel on Volcán de Colima, Mexico to understand rheology differences within multiple events, which occurred in late 2016. We used a combination of peak frequency content, directionality, and video analysis to determine rheology changes amongst the multiple events. Our findings show that different peak frequency patterns in each seismic component correspond to differing rheologies and flow processes. For instance, in the vertical and flow parallel directions the transition from streamflow to lahar coincides with a narrow frequency distribution to wide. Conversely, the cross-channel frequency content is opposite with streamflow portraying a wide frequency distribution transitioning to a narrow distribution with the lahars. Furthermore, there is a drop in overall peak frequencies when transitioning from streamflow to lahar. The directionality ratios computed further yielded evidence for a rheologic change between streamflow and lahar. Directionality ratios >1 were calculated for each lahar, and <1 for streamflow. We go on to show that componential analyses yielded channelization or freedom of movement in the cross-channel, bedload transport in the flow parallel, and channel geology in the vertical direction are possibly the main drivers in the peak frequency output of debris flows.

How to cite: Walsh, B., Coviello, V., Capra, L., Procter, J., and Márquez-Ramirez, V.: Geophysical insights on the internal dynamics of lahars from Lumbre channel, Volcán de Colima, Mexico, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9528, https://doi.org/10.5194/egusphere-egu2020-9528, 2020.

Rockfalls affect steep slopes in several geographic regions. Different systems from remote to in-situ instruments are used for their detection and study. In this scenario, seismic signals produced by the detachment, bouncing, and rolling of rockfalls are being increasingly used for the detection and classification of such events. This is typically done by using different manual, semi-automatic and/or automatic signal processing strategies. In this work, we applied a new Deep Learning (DL) algorithm in order to test the performance on the automatic classification of seismic signals. We applied the method to seismic data acquired by a low-cost Raspberry Shake 1D seismometer (sampling rate 50Hz) in order to discriminate rockfall from not-rockfall events occurred at the Moosfluh active slope region in Wallis (CH). Here we present the methodology and show the results obtained on a continuous record of more than 2-years of seismic data. The performance accuracy of the DL approach reached values larger than 90%. Our results show that the application of DL strategies in this context can be very useful and save time on seismic data classification.

How to cite: Dazzi, N., Manconi, A., Prakash, N., and Bickel, V.: Classification of Seismic Events with Deep Learning Strategies: Insights from the Moosfluh Landslide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9734, https://doi.org/10.5194/egusphere-egu2020-9734, 2020.

How to cite: Moores, A., Townsend, B., Pigeon, S., and Somerville, T.: A Versatile and Complete Technology Platform for Autonomous Ocean Bottom Seismometry , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12051, https://doi.org/10.5194/egusphere-egu2020-12051, 2020.

Heatwaves are extended periods of extremely hot weather and high temperature that have a major impact on human health, socioeconomics and natural systems. As predicted by climate models, ongoing global warming will potentially increase the incidence, intensity and duration of summertime heatwave events. Nevertheless, heat-related health impacts are largely preventable if populations, health and social care systems and public infrastructure are prepared. Therefore, this is plausible if heatwave events are studies for which heatwave real-time monitoring and assessment are central components. It is well recognized that land surface temperature retrieved by satellite sensors is an important variable associated with heatwaves and surface warming research. Land surface temperature retrieved by satellite sensors can be observed spatially and temporally, adequate for applications needing real-time and continuous measurements in quick response. In this study, Chinese Fengyun satellite data were used to monitor the land surface thermal environment during the heatwave event in Belt and Road communities. Split-window algorithm were applied to retrieve land surface temperature from thermal sensor. Spatial temporal distributions of Land surface high temperature are monitored in West Europe, India, and Australia as examples during their high temperature weather. The result shows that monitoring the real-time heatwave hazards in quick responds help provided information to the decision makers and get insight into the thermal environment characteristics over urban areas.

How to cite: Xu, R.: Land Surface High Temperature Monitoring in Belt and Road Communities, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13486, https://doi.org/10.5194/egusphere-egu2020-13486, 2020.

Operators of broadband seismic stations, particularly in hostile locations, are restricted in experiment design and deployment time-frames by the significant constraints of historical instrumentation. Manufacturers need to move away from the strict requirements on tilt tolerance and associated performance compromises, fixed frequency responses, unfriendly interfaces, slow data downloads and power-hungry systems in favour of simple, flexible and smart instruments that allow the operator to focus on the science at hand.

This transition is already happening with the evolution of seismic monitoring towards compact technologies: rapid-response deployments have, in recent years, become more and more feasible. However, installing low-noise, broadband instruments in remote areas has remained a challenge: low-noise force-balance broadband seismometers are typically heavy and delicate. They require significant infrastructure and logistics.

By developing the standalone, compact Certimus - with the same level of performance as traditional force-balance broadband seismometers - Güralp now offers researchers the opportunity to further push the boundaries of seismic monitoring and deploy stations in more and more challenging environments.

Unique sensor components allow Certimus to function up to 90 degrees tilt, removing the need for time-consuming centring, and allowing the station to be placed in small, hand-dug shallow holes. In 1s mode, the sensor will settle quickly and reliable data can be available in a matter of hours.  The frequency range is fully configurable in the long-period corner to allow this level of flexibility: 120s, 10s and 1s to 100Hz.

Certimus offers easy ways to check installation integrity – State-of-Health and live waveforms – before leaving the site: both with the surface and the burial variants, either via Bluetooth, LCD screen or Web Interface.

Since power consumption is a major limitation, Certimus comes with an ultra-low power mode (under 300mW) and a rugged battery module to gain up to six weeks of data before retrieval – or before a permanent power supply is arranged.

All files are recorded in industry standard miniSEED format making data download and management simplistic and universal. The metadata auxiliary channels record a vast range of state of health parameters to ensure optimal qualification of the seismic data with the environmental conditions of the seismic station.

All these advanced features are gathered in a compact, lightweight case that can be carried with all its accessories in a backpack to the most inaccessible areas. Quality seismic data is made available swiftly from anywhere, anytime.

How to cite: Balon, M., Filippi, S., Mohr, S., Hill, P., and Watkiss, N.: Certimus, a seismic station optimized for rapid deployment in rugged terrain, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18637, https://doi.org/10.5194/egusphere-egu2020-18637, 2020.

Under natural conditions, the structure and development of river corridors is controlled by an interplay of hydrological, geomorphological and ecological processes. Over the past decade, the concept of biogeomorphology has become increasingly popular to describe and analyze the manifold feedback mechanisms within river systems leading to an increasing number of studies. However, the majority of this work focuses either on conceptual development or on investigations on the scales of single geomorphic units or study reaches. Only very few studies enlarge the spatial scale to entire river corridors or networks despite the fact that recent frameworks emphasize these scales to be relevant for river research and management. A recent trend in remote sensing of terrestrial ecosystem is the use of dense imagery time series to assess trends and disturbances of vegetation development. In this study, we transfer this idea to the analysis of biogeomorphological interactions within fluvial environments on large spatial scales. We take the Naryn River in Kyrgyzstan as an example for demonstrating our satellite time series approach to biogeomorphological analysis of river corridors. The Naryn is still in a natural state on an entire flow length of more than 600 km with full longitudinal and lateral connectivity. Along the central part of the catchment, the Naryn is a highly dynamic braided river system shaped by the annual summer floods of a glacial discharge regime. This makes this river ideal to study large scale biogeomorphological dynamics. In our study, we follow the well-established concept of biogeomorphological succession suggested by Dov Corenblit and his colleagues. We mapped the different succession phases in the field and used the results to derive spectral-temporal indices of the succession phases. These indices are on the one hand used for a supervised classification based on Sentinel-2 imagery. On the other hand, we use Sentinel-2 as well as the longer term Landsat imagery time series to analyze the data for statistical trends and changepoints and evaluate this regarding biogeomorphological succession and disturbance events. The results reveal that dense time series of optical satellite imagery are well suited data sources to derive indicators of biogeomorphological interactions on large spatial scales. Especially when using the recently available Sentinel-2 imagery, such indicators have the potential to analyze biogeomorphological dynamics of entire river corridors or networks in a spatially and temporally continuous way at a reasonable spatial resolution.

How to cite: Betz, F., Lauermann, M., Egger, G., and Cyffka, B.: Biogeomorphology from Space: Using optical satellite imagery time series for analyzing the dynamic interaction of vegetation and hydromorphology along the Naryn River, Kyrgyzstan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10291, https://doi.org/10.5194/egusphere-egu2020-10291, 2020.

We applied the biogeomorphic ecosystem engineers concept to the Devonian Plant Hypotheses. By linking these two ideas we want to explore how recent discoveries on the role of trees in weathering processes could support the explanation of global environmental changes in the Devonian period. The occurrence of first land plants, vascular plants, trees, and complex forest ecosystems likely changed the nature and pace of many geomorphic and pedogenic processes. For instance, intensification of biological weathering driven by vascular plants might have influenced the global climate through consumption and accumulation of a large volume of atmospheric CO2. Innovation in the form and function of trees likely strongly influenced these processes, including soil stabilization via deep root systems. Mycorrhizal relationships further influenced weathering via chemical processes. While the lack of solid evidence in the fossil record still pose a problem, the progress in our understanding of soil-weathering processes induced by trees and root systems has expanded greatly in recent years, especially in terms of their biogeomorphic functions (e.g. tree uprooting, pedoturbations, biomechanical weathering, etc.), and can provide insights and testable hypotheses regarding the role of trees in the Late Devonian.

How to cite: Pawlik, L., Buma, B., Samonil, P., Kvacek, J., Galazka, A., Kohout, P., and Malik, I.: Biological weathering by the Devonian trees, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3162, https://doi.org/10.5194/egusphere-egu2020-3162, 2020.

Macrobenthic species that live within or on top of estuarine sediments can destabilize local mud deposits through their bioturbating activities. Resulting enhanced sediment availability will affect redistribution of fines and hence large-scale morphological change. To quantify this biological control on the morphological development of estuaries, we numerically model two contrasting bioturbating species present in NW-Europe by means of our novel literature-based eco-morphodynamic model. We find significant effects of both bioturbators on local mud accumulation and bed elevation change, leading to a large-scale reduction in deposited mud and gently sloped intertidal floodplains. In turn, the species-dependent reduction of mud content redefines their habitat and leads to constricted species abundances. Our results show that species-specific macrobenthic bioturbation determines large-scale morphological change through mud redistribution. This suggests that macrobenthic species have subtly changed estuarine morphology through space and time, depending on their distribution and composition.

How to cite: Brückner, M., Schwarz, C., and Kleinhans, M.: Modelling of interactions between bioturbation and mud distribution reveals effects on large-scale estuarine morphology, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6840, https://doi.org/10.5194/egusphere-egu2020-6840, 2020.

Submerged aquatic vegetation within river and coastal environments alters the local flow hydraulics, in turn influencing sediment dynamics and bed morphology. Vegetation canopies complicate bottom topography, with flexible elements often invoking complex spatial variability. Acquisition of quantitative, long time-scale data concerning the fluid dynamics associated with flexible aquatic canopies has remained limited due to the physical and visual obstruction presented by vegetation.

The experimental based research detailed here implements a novel Refractive Index Matching (RIM) technique, combined with Particle Image Velocimetry (PIV), to acquire flow field measurements within, and above, a dynamically scaled surrogate flexible seagrass canopy. RIM provides an undistorted optical view through the vegetation canopies, facilitating the investigation of coherent flow structures and canopy dynamics at five different Reynolds numbers. A flexible vegetation canopy of length 1.4m, width 0.45m, and height 0.12m, occupied the entire width of the 2.5m long RIM flume facility at the University of Illinois. The flume was operated in a free surface mode with a flow depth of 0.36m. Results from a counterpart rigid canopy also offer comparability and broader application of these findings to a range of flow-biota environments. Transparent rods formed the rigid canopy, while the flexible canopy elements comprised of four thin polymer blades extending from a short rigid stem. Vegetation elements were placed in a staggered arrangement to form canopies with a density of 566 stems m².

The results provide insights into canopy-based turbulence processes, including mixing layer properties associated with the canopy and vortex penetration. Deflection of the canopy and its waving motion is quantified, and linked to distinct hydrodynamic differences between the rigid and flexible canopies. Spatiotemporal variability associated with deflection of the flexible canopy, combined with the plant morphology, is shown to promote the spatial heterogeneity in turbulence distribution. Elucidation of instantaneous turbulent flow structures at various time intervals also reveals the links between above-canopy and in-canopy flow processes. This research provides new insights into the hydraulic processes of complex vegetated beds, including quantification of coherent flow structure evoultion. Application of these findings will help advance our knowledge of associated sediment transport dynamics, which is essential for interpreting larger-scale morphodynamic response and its role in environmental management.

How to cite: Houseago, R. C., Hong, L., Best, J. L., Parsons, D. R., and Chamorro, L. P.: Seeing through the fluid dynamics of flexible vegetation and canopy turbulence, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19155, https://doi.org/10.5194/egusphere-egu2020-19155, 2020.

How to balance ecosystem health and economic development is essential to study sustainability of urban ecosystems. Many methods for assessing urban sustainability have been developed, among which ecological footprint analysis (EFA) has been widely applied as a promising policy and planning tool. This paper proposed a modified EFA with the local ecological footprint being justified by adapting equivalence and yield factors in context of net primary productivity (NPP) from the Miami model. Biodiversity reserves were also incorporated using GIS technology and synthetic assessment of attributes to reflect various eco- logical functions. In addition, ecological footprint deficit (EFD), implying that the productive land cannot sustain current levels of consumption for a given population, was used to reveal the extent of ecological debt, while the ecological footprint variation index (EFVI) was proposed to describe the tradeoffs between real consumption and the carrying capacity of a specific region. A case study of urban areas in the middle stream of the Yangtze River Basin showed that the per capita EFD of the Wanjiang urban belt, central Poyang Lake urban agglomeration, suburban Poyang Lake urban agglomeration, Wuhan megalopolis, Jingmen–Jingzhou–Yichang urban agglomeration, central Changsha–Zhuzou–Xiangtan urban agglomeration, and suburban Changsha–Zhuzou–Xiangtan urban agglomeration increased by 64.83%, 178.05%, 214.82%, 59.08%, 71.68%, 100.62%, and 91.06% between 2000 and 2010, respectively. The local ecological footprint pressure index (EFPI) was classified into five levels. The Poyang lake urban agglomeration was found to be in a slight deficit, while all others were in a severe deficit in 2010. Calculations of EFVI also revealed that the booming urbanization occurred at great cost to the deteriorating ecosystems between 2000 and 2010. Accordingly, relevant influence factors were investigated using a forward stepwise regression method, which indicated that ecological deficit was positively correlated with GDP, population density, and emission of industrial waste, but negatively correlated with the tertiary industry.

How to cite: Wang, H.: Ecological footprint analysis for urban agglomeration sustainability in the middle stream of the Yangtze River, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9097, https://doi.org/10.5194/egusphere-egu2020-9097, 2020.

Densely populated low-lying areas are under pressure of relative sea level rise and human impacts. Low-lying areas like most of The Netherlands were built with fluvial-marine sediment supply interacting with peat and vegetation. The morphology and sedimentological architecture of such areas is controlled by initial conditions (e.g. accommodation space), boundary conditions (fluvial-tidal discharges) and internal biogeomorphodynamic feedbacks. The relative importance of these controls varies per system and we need generic rules to better understand the past and future delta and alluvial plain evolution. Here we setup novel long-term idealized morphodynamic models including stratigraphy and vegetation to unravel the effect of initial and boundary conditions in building landscape and creating complex depositional environments. Larger accommodation space creates and preserves a bayhead delta while limited space resulted in ebb-delta growth. Fluvial-tidal discharge fluctuations promote larger levees and more crevasses, contributing to floodplain accretion. The presence of sparse vegetation (i.e. trees) also contributed to floodplain infilling and created wide levees and more crevasses. On the other hand, dense vegetated floodplain inhibits levee widening and the formation of crevasses leaving the floodplain rather starved. Our results agree with the dimensions and evolution from geological reconstructions of the Rhine Delta in The Netherlands. In general, discharge fluctuations by rivers and tides, sediment delivery and (sparse) vegetation are crucial to create more land. These findings are important for the reconstruction of past environments and sediment budget estimative as well to future management of low-lying areas where raising the land-level is a challenge.

How to cite: Boechat Albernaz, M., Roelofs, L., Pierik, H. J., and Kleinhans, M.: Biogeomorphodynamic of fluvial-tidal levees and accommodation space infilling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2988, https://doi.org/10.5194/egusphere-egu2020-2988, 2020.

Landscape change is an interplay of abiotic and biotic processes with bi-directional and interwoven relationships. Glacier foreland areas can act as open-air laboratory to observe biogeomorphic interactions. Paraglacial adjustment establishes initial conditions for ecological succession and requires constant feedbacks between plants and landscapes. Frequency and magnitude of geomorphic processes and functional composition and abundance of plants govern these responses. Up to now, biogeomorphic studies have mainly focused on the qualitative description of the relationship between biotic and abiotic processes. However, in order to test biogeomorphic concepts, it is necessary to jointly quantify (i) geomorphic process rates as a function of vegetation and (ii) successional development as a function of geomorphic conditions.

The proglacial area of the Gepatschferner (Kaunertal) in the crystalline Central Eastern Alps presents a showcase environment to investigate these interactions as the retreating glacier and highly active slope processes provide the ground for different stages of ecological succession and promotes high rates of sediment reworking within the proglacial deposits.

In this particular study, we investigate small-scale biogeomorphic interactions at 30 test sites of 2*3m size. Experimental plots are established on slopes along an ecological succession gradient that reflect different stages of erosion-vegetation interaction. To cover the abiotic condition for the plot sites morphometric characteristics and edaphic variables were determined. In order to quantify abiotic process rates, we use mechanical measurements (i.e. erosion plots) to determine sediment yield and to measure the effect of vegetation on particle size distribution. Relative Dating, historical image analysis and knowledge of glacial retreat helped to estimate time since last perturbation. A detailed vegetation survey was carried out to capture biotic conditions at the sites. Species distribution and abundance at each site, as well as plant functional types provide information on successional stage and functional diversity.

This data set provides a vital opportunity to test conceptual models on biogeomorphic succession in glacier forelands and to evaluate the bi-directional influence of primary succession on small-scale sediment transport and vice versa.

How to cite: Haselberger, S., Ohler, L. M., Junker, R. R., Otto, J.-C., and Kraushaar, S.: Quantification of biogeomorphic interactions between small-scale sediment transport and primary succession in the Gepatschferner glacier foreland, Austria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17857, https://doi.org/10.5194/egusphere-egu2020-17857, 2020.

The transport of sediment shapes rivers and deltas, and has a huge impact on natural fluvial processes and human interaction within these environments. Conservation and hydraulic engineering applications in river basins crucially depend on understanding the processes of scour, transport and deposition of sediments. The sediment entrainment process in mathematical models are typically based on laboratory experiment using clean (abiotic) sediments. However, natural sediments are rich in biological communities, often forming visible biofilms which include sticky Extracellular Polymeric Substances (EPS). The presence of biological communities has been shown to significantly increase the critical shear stress of sediment entrainment compared with clean sediment, and these communities are recognized as ‘ecosystem engineers’ as they act as bio-stabilizers. Furthermore, biofilms provide stability, such that only the most energetic conditions can remove them in a sudden catastrophic way. In this study, a one-dimensional (1D) morphodynamic model for rivers is implemented to account for the development and growth of a surface biofilm subject to variable hydrodynamic disturbances (e.g. tidal forces) and with a biofilm-dependent erodibility. The 1D form of the shallow water equations are simplified with the aid of the quasi-steady approximation and the Exner equation expressing the conservation of bed material is used to compute the changes in channel bed elevation. The effect of geochemical drivers such as light, temperature and nutrients, which affect the presence or absence and growth of a biofilm, is accounted for in the model. Previous studies have shown that when sediments are covered by biofilms, entrainment occurs via biomat failure and the carpet-like detachment of biofilm-sediment composites. Different hydrodynamic conditions are tested to investigate their role in eroding the biofilm and detaching it from the sediment surface.

How to cite: Bastianon, E., Malarkey, J., and Parsons, D.: Effect of a surface biofilm on sediment transport implemented in a 1D numerical model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19077, https://doi.org/10.5194/egusphere-egu2020-19077, 2020.

Biogeochemical weathering of stable rock surfaces in warm and cold deserts is a notable biogeomorphological process, which contribute to mineralogical transformation of rock constituents and rock disaggregation. Endolithic microorganisms (mostly bacteria, fungi and lichens) play a major role in controlling the destabilization and rejunevation of rock surfaces; but occasionally, biofilms can stabilize rock surfaces. In most of the casis, endolithic communities precipitates byproducts (e.g. oxalates) contributing to enhance discotnituity and promoting exfoliation and disaggregation. On the contrary, rock varnish can develop as an external crust protecting the underliyng rock from erosion and dissolution. In this contribution, a number of case-studies of fossil and active examples of biogeochemical weathering from warm deserts of Africa and Arabian peninsula and from Antarctica are considered. The comaprison of evidence suggests a highly differentiate –  and occasioanlly surprisingly – array of effects of endolithic communities on rock surfaces.

How to cite: Zerboni, A.: Biogeomorphology at the micro-scale: biogeochemical weathering of rock surfaces in the cold and warm deserts, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21269, https://doi.org/10.5194/egusphere-egu2020-21269, 2020.

Inland waters are major contributors to the global carbon cycle. Nowadays, new sensor technology has changed the way we study ecosystem metabolism in streams. We are able to produce long-term time series of gross primary production (GPP) and ecosystem respiration (ER) to infer drivers of the stream ecosystem metabolic regime and its seasonal timing. Despite big data availability, most studies are limited to individual stream reaches and do not allow the appreciation of metabolic regimes at the scale of entire networks, which, however, would be fundamental to properly assess the relevance of metabolic fluxes within streams and rivers for carbon cycling at the regional and global scale. Machine learning (ML) has great potential in this direction. Firstly, ML could be used to extrapolate both in time and space heterogeneous forcings (e.g., streamwater temperature (T) and photosynthetic active radiation (PAR)) required to run a process-based model for reach-scale metabolism to the scale of an entire stream network. Secondly, the same procedure could be applied to reach-scale estimates of ecosystem metabolism to check whether available data contain enough information to explain the network scale variability. In this study, we used Random Forest to predict patterns of environmental forcings (T and PAR) and stream metabolism (GPP and ER) at the scale of an entire stream network. We used available high-frequency measurements of T and PAR, estimates of ecosystem metabolism and major proximal controls (e.g., incident light, discharge, stream-bed slope, drainage area, water level,  air temperature) from twelve reaches within the Ybbs River network (Austria) and explicitly trained our Random Forests by integrating distal factors, namely:  vegetation type, canopy cover, hydro-geomorphic properties, light,  precipitation, and other climatic variables. We designed two different training setups to assess spatial and temporal predicting model capabilities, respectively. This approach allowed us to reliably infer the target variables (T, PAR, GPP, and ER) on annual basis across a stream network, to filter the most important predictors, to assess the relative contribution of the metabolic fluxes from small to large streams, to estimate annual metabolic budgets at different spatial scales and to provide empirical evidence for long-standing theory predicting shifts of ecosystem metabolism along the stream continuum. Finally, we estimated autochthonous and allochthonous respiration for the entire stream network, which is crucial to integrate the role of ecosystem processes for the carbon cycle.

How to cite: Segatto, P. L., Battin, T. J., and Bertuzzo, E.: Data-based machine learning unveils ecosystem metabolic regimes at the scale of entire stream networks, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5504, https://doi.org/10.5194/egusphere-egu2020-5504, 2020.

Peat stored in large wetlands plays an important role in the carbon cycle and strongly influences water quality of terrestrial surface water bodies. At the same time, peat is also stored in the direct vicinity of many boreal forest streams. From this strategic position, peat can receive and chemically reset hillslope water before it reaches the stream network. Yet, in contrast to large wetlands, only little spatial information is available on the lateral extent of near-stream peat and even less about its vertical variation. Here, we present field data on peat depth and lateral extent collected from approximately 200 transects (with 12 soil profiles taken per transect) distributed across the entire stream network of the Krycklan boreal catchment in Northern Sweden. This soil profile data revealed a considerable heterogeneity of peat and organic horizon thicknesses. By combining the field data with morphological and geological maps, we show how parent material, stream order and local topography influence near stream peat structures. Furthermore, we discuss potential consequences on surface water quality by linking the detailed peat data set to estimates of lateral, shallow groundwater inflows derived from hydrometric measurements and digital terrain analysis.

How to cite: Grabs, T., Ledesma, J. L. J., Laudon, H., Seibert, J., Köhler, S., Teutschbein, C., and Bishop, K.: Revealing hidden peat structures along the stream network of a boreal forest catchment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17834, https://doi.org/10.5194/egusphere-egu2020-17834, 2020.

Point discharges of pollution such as effluents, enriched in bioavailable nutrients, organic matter and multiple contaminants, are often considered as having both strong local and cumulative downstream effects on aquatic ecosystem quality. Since potential impacts of effluents involve many multiple stressor interactions it requires an integrated suite of in-situ and ex-situ techniques to evaluate the biotic and abiotic interplay of the ecosystem effects. This study aimed to evaluate impacts using sampling transects around discharges from wastewater treatment works (WWTW) to a range of watercourses. The hypothesis was that major effluent discharges would lead to local downstream enrichment in nutrient and microbial contaminants, altered microbial communities and impairment in P processing rates with downstream recovery distances related to cumulative upstream pollution.

Five river transects were evaluated on two dates comprising points 100m above then 100, 200, 500 m below stream-side WWTW. Stream water samples were collected (effluents where possible) and analysed for C, N, P forms, coliforms, pesticides and pharmaceuticals. Biofilms (grown on tiles between sampling dates) and recovered for analysis alongside bed sediments for stoichiometry, P enzyme activity, substrate induced respiration assays and chlorophyll (biofilms). Catchments were characterised using spatial data on landcover, stream network and cumulative pollution sources.

Patterns of pollution presence in the waters and cycling indicators in the bed and periphyton did not show clear patterns of high local and declining downstream impacts. Instead a surprising complexity of weak transect effects amongst a high background heterogeneity was seen. This likely results from a heterogeneous biophysical environment of the channel as well as the complexity of the catchment ‘diffuse’ pollution inputs. Hence, WWTW impacts on aquatic pollution presence and processing factors were unclear and masked by catchment system heterogeneity and complexity.   

How to cite: Stutter, M. and Richards, S.: Point effluent discharges have unclear direct impacts on local biogeochemical P cycling against high background complexity in catchment pollution processes and ecosystem responses , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5736, https://doi.org/10.5194/egusphere-egu2020-5736, 2020.

Sediment mobilization in small-medium size mountain catchments occurs by different flow types, categorized as debris-flows, hyperconcentrated-flows and water-flows, depending on the physical mechanisms governing flow rheology and particles interaction. During high-magnitude flow events, such transport mechanisms may take place concurrently in the same catchment at different sites of the channel network. One of the most important tasks in investigating dynamics of floods in these mountain catchments is to identify the transport mechanisms, since different flow types induce peculiar geomorphological hazards and dynamics. This work aims to improve criteria to recognize different flow types, with particular regard to hyperconcentrated-flows, and to analyze the transport mechanisms in mountain catchments in response to high-magnitude hydrological events.

Since direct monitoring of sediment mobilization during a flood is extremely difficult, a sound alternative is to consider the characteristics of the deposited material, which depend on the rheological proprieties of related flow. Through an extensive literature review, we identified the diagnostic criteria of the different flow types, grouping them in morphological and sedimentological evidences. A field-survey worksheet has been developed to ease the field-data collection and interpretation. The case-study selected for applying the survey procedure is the Tegnas catchment (Dolomites, Italy), a mountain basin draining an area of 51 km² affected by the Vaia Storm in October 2018, which induced large floods in several catchments of the Eastern Italian Alps. The deposits field-survey has been conducted in 35 sub-reaches of the Tegnas river and its major tributaries. In addition, we carried out detailed grain-size analyses, measured the angle of clasts-imbrication and collected samples for estimating the vegetal organic matter content through Loss-of-ignition procedure.

Field criteria allowed us to classify each sub-reach according to the deposits left after the event. Most of the steep tributaries have been interested by debris-flows, but also hyperconcentrated-flows have been recognized. Along the main stem, water-flow was the dominant process, although debris-flows and hyperconcentrated-flows deposits are documented where channel slope was very high (i.e. from 9 to 21%).   Hyperconcentrated-flow deposits occur also in the lower sub-reaches (i.e. channel slope from 0.3 to 6%), either at the confluence with debris-flow fed tributaries of where severe bank erosion occurred. We statistically analyzed data about clast imbrication angle (δ) and content of vegetal organic matter (OM_LOI) obtaining significant results for both parameters. δ measured in debris-flow (50°-65°) and hyperconcentrated-flow deposits (45°-60°) is considerably higher than in water-flow sediments (30°-40°). Debris-flow and hyperconcentrated-flow deposits have higher OM_LOI (2.5-5.5%) than water-flow deposits (1.5-3%). 

The combination of field diagnostic-criteria and quantitative measure of additional parameters allows a reliable recognition of the flow types based on post-flood survey. Besides, this study allowed to point out that during high-magnitude floods the sediment mobilization in small-medium size catchments occurs through mechanisms that can be different from those expected for ordinary hydrological events using morphometric approaches. Solid material concentration or dilution (e.g. due to lacking of sediment sources or sediment disconnectivity) can explain the “unexpected” flow types during high magnitude events.

How to cite: Brenna, A., Surian, N., Borga, M., Ghinassi, M., and Marchi, L.: Recognition and Occurrence of Different Sediment-Water Flows Triggered by High-Magnitude Hydrological Events in Mountain Catchments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7333, https://doi.org/10.5194/egusphere-egu2020-7333, 2020.

Empirical sediment transport models have common characteristics suggestive of the underlying physics, but mechanistic explanations for these characteristics are lacking due to an incomplete understanding of the fundamental physical mechanisms involved. Hydrodynamic interactions at the grain-scale are thought to be key, however, it is a major challenge to either observe or model these processes. In order to improve our understanding of grain-scale dynamics in sediment entrainment and transport we are studying the detailed mechanics of fluid-grain interactions using a combination of laboratory flume experiments, advanced numerical simulations, and granular mechanics theory. 

The flume experiments are conducted with an emphasis on exploring differences and similarities in the behaviour of glass spheres, a common theoretical tool, to naturally sourced river gravel. Using high-speed cameras coupled with computer-vision based particle tracking, we tracked the majority of grains in the grain bed and water column, with 130,000 glass sphere track paths longer than 10 particle diameters. In particular, we introduce a newly developed a machine learning based particle tracking of the natural grains, with 30,000 gravel track paths longer than 10 mean particle diameters. Fluid flow fields are also observed using particle image velocimetry (PIV). We present the comparison of our detailed observations of granular dynamics between spheres and natural gravel, with a focus on how grain shape impacts fluid-grain and grain-grain interactions.

Using a discrete-element plus Lattice-Boltzmann fluid method (LBM-DEM) we simulate a small portion of the laboratory flume with high temporal and spatial resolution. This method tracks discrete particles interacting with each other through contact laws while mechanically coupled to a dynamic interstitial fluid. We discuss the ability of our simulations to emulate our experiments, the benefits of which are twofold. First, where the simulations work well, we use them to observe grain-scale dynamics that would be difficult or impossible to measure in a laboratory setting or in the field. Second, we learn from situations in which the experiments and simulations diverge, leading to improvements in both the simulations and our understanding of how fluid-grain interactions influence sediment transport.

How to cite: Deal, E., Perron, T., Venditti, J., Zhang, Q., Benavides, S., and Kamrin, K.: Observing and modeling bedload sediment transport at the grain-scale, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21982, https://doi.org/10.5194/egusphere-egu2020-21982, 2020.

Natural granular flows have a widely dispersed grain size distribution. The majority of the numerical models and laboratory investigations of granular flows are developed assuming a single grain size. However, the geophysical massive flows involve several classes of particles and the bulk solid evolves spatially in a non-uniform state [1]. Segregation causes a different spatial distribution of the particles and influences the kinematic of the bulk solid, like the concentration, the run-out, the velocity and the granular temperature. During the flow motion, the largest particles are found at the surface due to the imbalances in the contact forces, and the smallest at the bottom as they percolate due to gravity [2].

To investigate the physical processes responsible of the particles transfer, we conducted a series of laboratory experiments, using two different grain size classes to reproduce the binary mixture. The measured data are required to calibrate the mathematical model and to set the coefficients that describe the percolation and the kinetic sieving mechanism. The experiments to study the free surface flow started considering the dry condition. Two different type of classes of particles flow over a loose deposit in homogenous and steady conditions. We used spherical particles of non-expanded polystyrene with a density of 1035 kg/m³. The small beads are black with a mean diameter of 0.00075 m and the large beads are white with a mean diameter of 0.0014 m. At the end of the flume there is a weir with two openings. The material is manually inserted and flow in the flume, it is then recirculated by an auger and finally conveyed in a hopper, from where it falls down in the chute again. The system works for at least 30 minutes, after reaching the steady condition.

The measurements were taken through a high speed camera in a section lateral to the flume. The flow field was measured with an optical method, that gives the velocity, the concentration and the granular temperature for both the small and the large particles, from the sidewalls.

Analyzing the experimental data, as regards the longitudinal velocity, it is possible to observe that the velocities of the two classes are similar and the large particles flow a bit faster. In contrast, there is a strong segregation in the concentration rates. After the running time, segregation causes the separation of the two classes: the largest classes are in the upper part and the smallest fraction at the bottom.

References

1 Drahun J.A., Bridgwater J. The mechanisms of free surface segregation, Powder Technology, 36, 39-53, 1988.

2 Savage S., Lun K.K. Particle size segregation in inclined chute of dry cohesionless granular solids, Journal of Fluid Mechanics, 189, 311-335, 1988.

How to cite: D'Agostino, S.: Experimental analysis of segregation in granular flows, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10063, https://doi.org/10.5194/egusphere-egu2020-10063, 2020.

We studied granular flows of glass beads on an inclined conveyor channel. An upward-moving belt conveyed particles that flowed down the channel under the action of gravity, thus creating a stationary flow. To visualize the internal dynamics of the bulk, we relied on the refractive index matching technique. Under fixed slope and belt velocity, we ran mono- and bi-disperse experiments to characterize spatially and temporally the dynamics and concentration fields of these granular flows. Mono-disperse experiments were done using 6 and 8 mm beads on slopes of 10, 12, 15 and 18° and 3 different belt velocities. Beads of 14 mm were added in concentrations of 10, 20, 30 and 40% for the bi-disperse experiments. The rear part of the flow exhibited well-arranged particle layers that moved relatively between them. This particle arrangement ended with a sharp transition to the front of the flow and a dilated convective front. Bi-disperse experiments with low concentrations of large particles conserved the same layered-convective regime with the few added large beads confined to the convective front, a result of size segregation. When the concentration of large beads was increased to 30%, the described regime disappeared. Large grains were frequently dragged back by the belt, thus disrupting the arrangement of particle layers. A quasi-stationary behavior was observed in these experiments, small particles migrated to the front of the flow in pulses that after a while were dragged back, repeating the cycle. We observed that particle concentration fields, on average, were consistent with the structures observed for the  breaking size-segregation wave phenomenon. The effective basal friction, local concentrations and dilation, among other variables, are responsible for these phenomena.

How to cite: Trewhela, T., Gray, N., and Ancey, C.: Flow regimes, grain mobility and size segregation in stationary bi-disperse granular flows, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18412, https://doi.org/10.5194/egusphere-egu2020-18412, 2020.

Soil liquefaction is one of the most impactful secondary hazards of earthquakes. For example, it played a crucial role in driving the devastating landslides following the 2018 Palu earthquake, Indonesia. While traditionally, the initiation of liquefaction is treated as an undrained phenomenon, evidence shows that a well-drained end-member exists.

We develop a theory for the coupled grains - pore fluid system, and conduct numerical discrete element – fluid dynamics simulations and lab experiments under well-drained conditions. Here, a well-drained layer means that the interstitial fluid can flow out of the layer faster than a single earthquake shaking period. Theory, simulations, and experiments, all suggest that a saturated granular layer, although well-drained, can liquefy when subjected to horizontal cyclic shear. The liquefaction event, evident by high pore pressure, loss of shear strength, and dissipation of shear waves is spatially and temporally controlled by a compaction front that swipes upward through the layer. The compaction front separates the grain-fluid system into two sub-layers: The bottom sub-layer, below the front, is fully-compacted, and the pore pressure gradient across it is hydrostatic. The top sub-layer, above the front, is actively subsiding, and its pore pressure gradient reaches the total solid stress gradient. I.e., the fluid fully supports the granular skeleton. The velocity of the compaction front depends on the permeability of the soil layer and the viscosity of the interstitial fluid. Analytic considerations of the propagation rate of the compaction front allows us to evaluate the duration of a liquefaction event, the magnitude of soil subsidence, and the timing of water seepage at the surface level, which are all independent of the time scales related to the earthquake shaking. Our approach, when combined with field stratigraphy and groundwater level data, could explain and predict the occurrence and duration of soil liquefaction when the soil layer is effectively drained.

How to cite: Ben-Zeev, S., Aharonov, E., Goren, L., Toussaint, R., and Parez, S.: Compaction front controls soil liquefaction dynamics of drained saturated grain layers, as evident by theory, numerical simulations and lab experiments , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10688, https://doi.org/10.5194/egusphere-egu2020-10688, 2020.

The flow resistance in granular mass flows can be due to frictional contacts or collisional interactions between particles. For a constant number of particles, the transition from a frictional to a collisional regime is expected to depend on flow velocity and is associated with an increase of volume and a decrease of bulk density, an effect termed dilation. The relation between velocity, dilation and flow resistance is not well understood. Here we present results of steady, non-uniform flows of ceramic beads (d = 4 mm) in a rotating drum, a setup allowing observations and averaging of parameters measured over an extended period of time. We systematically varied flow mass between 12.3 and 49 kg and flow velocity between 0.2 and 1.2 m/s, while continuously measuring basal normal stress and flow depth. Flow resistance was assessed by calculating average bulk shear stress from torque measurements at the axis of the drum as well as from the deviation of the center of mass from the vertical. Additionally, the flows were captured by high-speed video recordings through the transparent side wall. We find bulk densities at the deepest section of the flow decreasing from 1430 kg/m³ at low velocities to 1370 kg/m³ at the highest velocity for the largest flow mass. At the same time flow resistance increased linearly. When the flow mass was reduced, also bulk density decreased, indicating the importance of overburden pressure for dilation. Video recordings revealed that shear is concentrated in depth zones of lower volume fraction. Our results shall contribute to a better understanding of the transition from a frictional to a collisional flow regime and may help to assess the importance of dilation for gravitational mass flows.

How to cite: Kaitna, R., Shuai, L., Taylor-Noonan, A., Take, W. A., McArdell, B., McElwaine, J., and Bowmann, E.: Dilation and flow resistance of granular flows in a rotating drum, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18418, https://doi.org/10.5194/egusphere-egu2020-18418, 2020.

This contribution presents results of field measurements of wind-blown sand streamers and turbulent flow structures in the boundary layer airflow during gale-force winds on a beach. Sand transport and streamers were measured using Large-Scale Particle Image Velocimetry (LSPIV) combined with laser particle sensors (Wenglors), and airflow turbulence was monitored with a co-located sonic anemometer. The data analysis yields insight into the precise spatio-temporal relationships between sand streamers and near-surface airflow turbulence, at a high resolution of 25 Hz and a centimetre scale, including how high-energy sweeps correlate with the passage of fast-moving saltation clusters, and how Turbulent Kinetic Energy (TKE) may be linked to sediment mass flux.

How to cite: Baas, A.: Wind-Blown Sand Streamers and Turbulent Flow Structures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7777, https://doi.org/10.5194/egusphere-egu2020-7777, 2020.

In the state-of-the-art for suspended-load modeling it is commonly assumed that the concentration profile results from a balance between a settling flux, in which the settling velocity is considered as equal to its value for a single settling particle in quiescent water, and an upward turbulent flux modeled using a Fickian gradient diffusion approximation. While this model provides a general framework, comparison with experiments reveals that the concentration diffusivity is not equal to the eddy viscosity and a turbulent Schmidt number needs to be introduced. Based on Coleman (1970,1981) data, van Rijn (1984) proposed an empirical model which suggests that the Schmidt number is a decreasing function of W_s/u_*. This result is intriguing as it suggests that the turbulent dispersion of sediment concentration is enhanced when the particle’s settling velocity increases relative to the bed friction velocity. Van Rijn suggested that this is due to centrifugal forces that tends to throw inertial particles out of the turbulent vortices leading to an enhanced particle dispersion compared to momentum. In the present contribution, we use high-resolution experimental data and turbulence resolving two-phase flow simulations that directly resolve the turbulent momentum and particle fluxes and the flow turbulence to investigate the different terms appearing on the mass balance mentioned above.  Both the experimental and the numerical results show that the actual turbulent Schmidt number based on the resolved sediment flux is higher than unity meaning that turbulent dispersion efficiency of « heavy particles » is reduced. This contradicts van Rijn’s prediction model of the Schmidt number. One plausible explanation is that the settling velocity of particles is reduced in highly turbulent flows. Using the experimental and numerical results, the actual settling velocity in the turbulent flow is retrieved from the mass balance at steady state. It is found that it is significantly retarded compared with the value in quiescent water (10 to 40%). This result is in good agreement with the one obtained in recent experiments performed in a turbulent grid at KIT (Germany) using the same particles (Akutina et al., 2020). The authors found a settling retardation of 16% for the same turbulent intensities as in the present experiments. The results presented herein completely change the paradigm for turbulent suspension load modeling and open new perspectives on the development of new, physical process-based, parametrizations required for large-scale models. This, of course, will require to extend the proposed methodology to a wider range of flow and sediment conditions.

How to cite: chauchat, J., Revil-Baudard, T., Cheng, Z., Hurther, D., and Hsu, T.-J.: On the physical origin of enhanced turbulent-dispersion of 'heavy particles' in suspended-load, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14748, https://doi.org/10.5194/egusphere-egu2020-14748, 2020.

Turbidity currents are a major way to transport sediment along reservoir, lake and sea beds. They are not fully understood yet due to the difficulty of accessibility. Theoretical criteria have been established for the conditions that generate accelerating turbidity currents, which can produce strong erosion of channel beds, transmit over long distances and thus have important significance for reservoir and sea bed morphology. However, the current theoretical criterion only utilizes local factors of hydraulic, morphology and grain size, which do not necessarily depend on the up- and down- stream boundary conditions. Here, we conducted field surveys on turbidity currents and bed morphology of the Xiaolangdi reservoir on the Yellow River, China. The survey results show clear evidence of accelerating turbidity currents. We identify two types of accelerating turbidity currents: one locates closely to the upstream plunging point where fluvial sediment-laden flow collapses to a stratified turbidity current, concentrating momentum and producing acceleration locally, and the other is located downstream and shows dependence on the enhancement of local slope and potentially on downstream boundary (flushing condition at flow outlets of the dam). So both ends of the boundaries may work together to produce long run-out turbidity currents that transmit through the entire reservoir.  Although preliminary, our dataset indicates that the conditions for accelerating turbidity currents are not only controlled by local morphology and grain size, but also by both upstream and downstream conditions. A comprehensive understanding of the boundary conditions so as to determine conditions for the generation of accelerating turbidity currents will help enhance the sustainability of the dam and reservoir system.

How to cite: Ma, H., Parker, G., Nittrouer, J., McElory, B., Wang, Y., Chen, X., and Fu, X.: Controls of boundary conditions on accelerating turbidity currents in a reservoir: Case study of Xiaolangdi Reservoir on the Yellow River, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20944, https://doi.org/10.5194/egusphere-egu2020-20944, 2020.

Abstract

Recent experiments have established that the sediment particle motion, especially for particles near the bed, may not follow the normal (Fickian) diffusion behavior. To modify the diffusion equation where the fluctuation velocity is based on the normal distribution, this investigation hypothesizes that the fluctuation velocity based on bivariate probability distributions and particle-bed collision in open channel can provide some physical insight into the particle diffusion behavior. The distribution of fluctuation velocity is obtained using the Gram-Charlier expansion which considers the first four statistical moments of turbulent fluctuation velocity. The correlation between two-dimensional fluctuation velocities is modeled by performing Monte Carlo simulations. Besides, the uniform momentum zones (UMZ) are further identified and consequently the spatial locations of the edges that demarcate UMZs can be estimated. Once UMZs in the turbulent boundary layers can be characterized, the streamwise momentum deficit, and occurrences of ejection events and sweep events in the vicinity of UMZ edges under different Reynolds numbers can be simulated. The spatial influence of turbulent coherent structures on sediment particle trajectory can be demonstrated.

How to cite: Tsai, C. and Wu, K.-T.: Beyond Normality: Estimation of Near-Bed Sediment Concentrations Accounting for Asymmetric Distribution and Spatial Influence of Turbulence Coherent Structures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21416, https://doi.org/10.5194/egusphere-egu2020-21416, 2020.

Overtopping of fluvial dikes occurs frequently during major floods and may lead to dike failure, with severe consequences in the protected areas. Mechanisms of fluvial dike breaching remain incompletely understood, while predicting the breach hydrograph is of paramount importance for the flood risk management.

Here, we present a new series of laboratory experiments, in which the evolving 3D fluvial dike geometry was monitored in detail using the laser profilometry technique. The experimental setup extends over about 20 m by 7 m and accommodates a 15 m long main channel and a 7 m-long dike section. The facility is located at LNHE of EDF-R&D (France). The present study extends former experiments by Rifai et al. (2017, 2018), which were conducted with uniform coarse sand (d₅₀ = 1.03 mm). In the new tests, various mixtures of coarse (d₅₀ = 1.03 mm) and fine (d₅₀ = 0.24 mm) sands were used as dike material (Rifai et al., 2020). The fraction of fine sand was varied systematically to assess its influence on the breaching process, specifically as regards the apparent cohesion.

The experimental observations reveal that the frequency of breach slope collapse tends to decrease as the fraction of fine sand is increased; but the collapsing volumes become larger. Consequently, in the tested configurations, the addition of fine sand to the dike material has virtually no effect on the overall breaching dynamics, due to compensation between less frequent but larger collapsing material volumes. In the presentation, the relative importance of the effects will be discussed in comparison with other influencing parameters such as the main channel discharge, floodplain backwater effects and the dike geometry.

All experimental data, including high resolution 3D dynamic models of the breach geometry, are publicly available online (Rifai et al., 2019).

References

Rifai, I., Erpicum, S., Archambeau, P., Violeau, D., Pirotton, M., El kadi Abderrezzak, K., & Dewals, B. (2017). Overtopping induced failure of noncohesive, homogeneous fluvial dikes. Water Resources Research, 53(4), 3373-3386.

Rifai, I., El kadi Abderrezzak, K., Erpicum, S., Archambeau, P., Violeau, D., Pirotton, M., & Dewals, B. (2018). Floodplain backwater effect on overtopping induced fluvial dike failure. Water Resources Research, 54(11), 9060-9073.

Rifai, I., El kadi Abderrezzak, K., Erpicum, S., Archambeau, P., Violeau, D., Pirotton, M., & Dewals, B. (2019). Flow and detailed 3D morphodynamic data from laboratory experiments of fluvial dike breaching. Scientific data, 6(1), 53.

Rifai, I., El kadi Abderrezzak, K., Hager, W.H., Erpicum, S., Archambeau, P., Violeau, D., Pirotton, M., & Dewals, B. (2020). Apparent cohesion effects on overtopping-induced fluvial dike breaching. Journal of Hydraulic Research. In press. https://doi.org/10.1080/00221686.2020.1714760.

How to cite: Dewals, B., Rifai, I., El kadi Abderrezzak, K., Schmitz, V., Hager, W., Violeau, D., Archambeau, P., Pirotton, M., and Erpicum, S.: Addition of fine material is expected to strengthen fluvial dikes ... does it really?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11785, https://doi.org/10.5194/egusphere-egu2020-11785, 2020.

Due to their stochastic and fluctuating nature, the entrainment and transport of sediment particles present great challenges to scientists and engineers who endeavor to formulate a universal framework for quantifying sediment dynamics and transport behaviors. The application of impulse theory represents one of such efforts and has received increased attention over the past decade. Practically, the impulse concept helps to remove the inactive periods of transporting process from the entire transport history, such that the underlying driving mechanism of particle movements can be better identified. This approach not only proves to be useful in characterizing the threshold of motion conditions, as tested against experimental data from an increased body of literature, but also provides a new perspective in formulating the constitutive relation of bedload transport. In this study, we employ a similar criterion, yet based on the pertinent amounts of energy imparted upon sediment particles, to reproduce the stress-transport relations. These post-conditioned stress-transport relations are almost devoid of the inactive periods and, thus, better represent the physics of transport of sediment particles. It is noted that a consistent 1.5th power law has been recovered from a wide range of transport flow conditions, which can be deemed as a constitutive relation for bedload transport. Further examination of these data sets indicates that, in essence, the obtained 1.5th power relation accounts for a constant energy transfer efficiency of fluid flow applied upon the sediment particles. These efforts, based on the impulse concept, lead to a unified approach to sediment transport problems.

How to cite: Diplas, P. and Shih, W.: Impulse concept in formulating a unified approach to bedload transport, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9217, https://doi.org/10.5194/egusphere-egu2020-9217, 2020.

Scour has been recognized as one of the primary reasons for bridge pier destabilization. As extreme weather intensifies and hydraulic infrastructure such as bridge piers and abutments (many constructed since the Victorian era, for the case of the UK) continues to age, the challenge of scour-induced hazards will keep growing impacting the resilience of our society. Thus, there is an increasing value in studying the highly dynamical process of scour around hydraulic infrastructure. Maximum scour depth estimation has been broadly studied by researchers over the past decades, using phenomenological or empirical approaches, linking mean flow properties, bridge pier and riverbed materials characteristics [1, 2].

This study aims to get a better understanding of how the turbulent flow field modified by the bridge pier, interacts with the bed surface towards the generation of the scour hole. This is pursued by following a dynamical approach via assessing the flow structures that are sufficiently energetic [3] to remove bed material from the vicinity of the bridge pier.

A series of scour experiments with different lengthscale of model bridge piers is conducted in a water recirculating research flume. For each of these cases flow velocity profiles are collected downstream the bridge pier using high resolution acoustic Doppler velocimetry (ADV). Using the raw data collected near the bed surface and information for the bed surface material, the criterion of impulse [4] is used as a metric for assessing the extend and maximum scour depth. The results are compared for the different measurement locations are compared to better understand the process of scour downstream different model piers.

[1]. M Valyrakis, P Michalis, H Zhang, (2015). A new system for bridge scour monitoring and prediction, Proceedings of the 36th IAHR World Congress, 1-4.

[2]. Yagci, O., Celik, M. F., Kitsikoudis, V., Ozgur Kirca, V.S., Hodoglu, C., Valyrakis, M. , Duran, Z. and Kaya, S. (2016) Scour patterns around isolated vegetation elements. Advances in Water Resources, 97, pp. 251-265.(doi:10.1016/j.advwatres.2016.10.002)

[3]. Valyrakis, M. , Diplas, P. and Dancey, C.L. (2013) Entrainment of coarse particles in turbulent flows: an energy approach. Journal of Geophysical Research: Earth Surface, 118(1), pp. 42-53. (doi:10.1029/2012JF002354)

[4]. Valyrakis, M. , Diplas, P., Dancey, C.L., Greer, K. and Celik, A.O. (2010) Role of instantaneous force magnitude and duration on particle entrainment. Journal of Geophysical Research: Earth Surface, 115(F02006), 18p. (doi:10.1029/2008JF001247)

How to cite: Xu, Y., Valyrakis, M., and Michalis, P.: Assessing energetic flow structures responsible for bridge pier scour, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1502, https://doi.org/10.5194/egusphere-egu2020-1502, 2020.

In recent years, the impact of landslides on society has increased due to increasing urbanisation and climate change (as much as up to 30%). In about a decade, around 5000 fatal non-seismic landslides have occurred world-wide resulting in almost 56000 deaths, most of which took place in developing countries, such as China and Philippines. The purpose of studying the characteristics of landslides is to develop a better understanding of their features and to reduce any threat posed by them. Out of these characteristics the runout distance directly determines the impact of the landslide and extend of the affected area which are useful in evaluating risk to infrastructure (such as road pavement or railroad or built structures). Therefore, the study of landslide runout distance prediction has great significance for urban planning and risk assessment, specifically in mountainous areas.

This study focuses on conducting a review of previous literature on landslides reported at the region of Wenchuan in Sichuan (China), aiming to identify any trends connecting the cause and effect relationship between landslides in a phenomenological and empirical manner. Specifically, a dataset of landslides (20 due to rainfall and 50 due to earthquake) is used to statistically link, using multiple regression analysis, the travel distance to five main influencing factors, including landslide volume, height of landslide, landslide plane form, landslide average thickness and relative coefficient of friction. Good results are obtained through error minimisation rendering the developed framework as a useful tool for predictive analysis of the potential extend and impact of landslides using historical regional data.

How to cite: Gu, P. and Valyrakis, M.: A regression analysis framework for the prediction of runout distance of landslides: a case study for Sichuan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1505, https://doi.org/10.5194/egusphere-egu2020-1505, 2020.

Large number of bridges in Europe is at the end of their life span, while the frequency of occurrence for extreme climatic events, driven by climate change, is increasing. Floods influence morphodynamic changes in the riverbed, such as scouring of the riverbed next to the bridge substructure, that can undermine the overall stability of the bridge. Placement of riprap protection around bridge piers is an approach that doesn’t solve scouring problem, it rather displaces the scour hole elsewhere in the river channel, where its location is unknown because it is formed in the interaction between the flow and the structure, in site-specific conditions. Traditional approach to scour monitoring is effective only if surveys are conducted during the flood conditions, while the data acquired post-flood can underestimate the full potential of flood hazard. Detailed field surveys of hydraulic parameters during floods are essential in the understanding of morphodynamic evolution of the river channel, but are often scarce because they are time-consuming and require extensive resources (e.g. the survey equipment). Therefore, the majority of research was conducted using hydraulic flumes where both flow and the riverbed conditions are idealized 

The goal of the R3PEAT project (Remote Real-time Riprap Protection Erosion AssessmenT on large rivers) is to bridge the gap between the real-time scour hole development and flow environment through development of real-time scour monitoring system. The research focus of the project is investigation of scouring processes next to the riprap protection around bridge piers - existing structures whose stability and safety are unknown in the hydraulic environment under the influence of climate change. Research methodology combines experimental investigations on scaled physical model (Phase I) with 3D numerical model (Phase II) into hybrid modelling approach, calibrated and validated with field surveys. The research objectives of the project are: (1) develop ScourBuoy prototype (2); calibrate the physical model with field surveys; (3) improve existing empirical equations for equilibrium scour hole development using hybrid modelling approach; (4) investigate the dependence between turbulent flow characteristics and temporal scour hole development and (5) investigate dependence between turbulent conditions and incipient motion of sediment particles. The impact of the proposed project on the bridge management systems is expected through the development of a practical remote real-time system for erosion estimation around the riprap protection on large rivers that can be basis for the real-time decision support system.

Acknowledgment:
This work has been supported in part by Croatian Science Foundation under the project R3PEAT (UIP-2019-04-4046)

How to cite: Gilja, G., Cikojević, A., Potočki, K., Varga, M., and Adžaga, N.: Remote Real-time Riprap Protection Erosion AssessmenT on large rivers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1933, https://doi.org/10.5194/egusphere-egu2020-1933, 2020.

Embankments, found in virtually all transportation and river networks, can be subjected to severe scouring and erosion issues due to more intensified climatic change, which may increase their failure risk [1]. Monitoring of embankment conditions with modern means is essential for ensuring the structural stability of nearby infrastructure (eg. roads and rail networks) against any geotechnical and hydraulic hazards [2, 3]. Additive manufacturing (AM), commonly referred to as 3D printing (3DP), is increasingly finding applications in the construction industry and is defined by the American Society for Testing and Materials (ASTM) International Committee as “the process of joining materials to make objects from 3D model data, usually layer upon layer”. This research is demonstrating the application of additive manufacturing technology in producing an electrical resistance strain gauge mechanism [2] to monitor the probability of embankment scouring failure, thus, warning could be given prior any devastating catastrophes, and preventive measures could be implemented accordingly. Electrical resistance strain gauges could be manufactured utilizing a dual-extrusion 3D printer which allows simultaneous depositions of a conductive material and a structural material in one print. Specifically, a range of control parameters are assessed here including different arrangements of the conductive material within the structural material matrix as well as infill percentages. The parameters aforementioned have effects on the gauge factor of the strain gauges produced. Overall, the 3DP sensors could be deployed to monitor embankment slope failure attributed to erosion, flooding and external loading (eg. due to heavy vehicle passage over it, for road embankments), which are important challenges [2, 3].

Acknowledgements

This research project has been funded by Transport Scotland, under the 2019/20 Innovation Fund (Scheme ID18/SE/0401/014) and the Scottish Road Research Board (Student research competition award 2019).

References

[1] Koursari, E., Wallace, S., Valyrakis, M. and Michalis, P. (2019). The need for real time and robust sensing of infrastructure risk due to extreme hydrologic events, 2019 UK/ China Emerging Technologies (UCET), Glasgow, United Kingdom, 2019, pp. 1-3. doi: 10.1109/UCET.2019.8881865

[2] Michalis, P., Saafi, M. and Judd, M. (2012) Wireless sensor networks for surveillance and monitoring of bridge scour. Proceedings of the 11th International Conference of Protection and Restoration of the Environment (KatsifarakisKL, Theodossiou N, Christodoulatos C, Koutsospyros Aand Mallios Z (eds)). Thessaloniki, Greece, pp. 1345–1354

[3] Michalis, P.; Konstantinidis, F.; 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), Chania, Greece, 23–26 June 2019.

How to cite: Chen, H., Michalis, P., and Valyrakis, M.: Additive Manufacturing of electrical strain gauges for the monitoring of embankment failures, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5866, https://doi.org/10.5194/egusphere-egu2020-5866, 2020.

Under climate change, shifting  weather conditions, (both in terms of increasing frequency and intensifying magnitude) result in increasing occurrence of catastrophic failures of the constantly exposed and ageing infrastructure, across the world. Energetic flow events, advected past hydraulic infrastructure (such as bridge piers and abutments), may lead to scour [1, 2, 3], which is the primary cause of bridge collapses, resulting in high socio-economical costs, including loss of life.

This research aims to demonstrate the use of a novel monitoring device for the assessment of scour initiated by turbulent flows. This is pursued via the use of a miniaturized instrumented particle, namely “smart-sphere”, to record directly the frequency of entrainment from its downstream placement a model bridge pier at the Water Engineering lab of the University of Glasgow [4, 5, 6]. The change in entrainment frequencies is used as a metric to assess the increasing risk to scour, with increasing flow conditions, recorded acoustic Doppler velocimetry (ADV). The utility of the method as well as the potential use of the acquired data for prediction of bridge pier scour is presented and the tool as well is discussed with the potential for use to an appropriate field site [7, 8, 9].

Acknowledgments

This research project has been supported by Transport Scotland, under the 2019/20 Innovation Fund and the Student research award.

References

[1] Pähtz, Th., Clark, A., Duran, O., Valyrakis, M. 2019. The physics of sediment transport initiation, cessation and entrainment across aeolian and fluvial environments, Reviews of Gephysics, https://doi.org/10.1029/2019RG000679.

[2] Yagci, O., Celik, F., Kitsikoudis, V., Kirca, O., Hodoglu, C., Valyrakis, M., Duran, Z., Kaya S. 2016. Scour patterns around individual vegetation elements, Advances in Water Resources, 97, pp 251-265, doi: 10.1016/j.advwatres.2016.10.002.

[3] Michalis, P., Saafi, M. and M.D. Judd. (2012) Integrated Wireless Sensing Technology for Surveillance and Monitoring of Bridge Scour. Proceedings of the 6th International Conference on Scour and Erosion, France, Paris, pp. 395-402.

[4] Valyrakis, M. & Pavlovskis, E. 2014. "Smart pebble” design for environmental monitoring applications, In Proceedings of the 11th International Conference on Hydroinformatics, Hamburg, Germany.

[5] Valyrakis M., A. Alexakis. 2016. Development of a “smart-pebble” for tracking sediment transport. International Conference on Fluvial Hydraulics River Flow 2016, St. Liouis, MO, 8p.

[6] Valyrakis, M., Farhadi, H. 2017. Investigating coarse sediment particles transport using PTV and “smart-pebbles” instrumented with inertial sensors, EGU General Assembly 2017, Vienna, Austria, 23-28 April 2017, id. 9980.

[7] Valyrakis, M., Diplas, P., Dancey, C.L. 2011. Prediction of coarse particle movement with adaptive neuro-fuzzy inference systems, Hydrological Processes, 25 (22). pp. 3513-3524. ISSN 0885-6087, doi:10.1002/hyp.8228.

[8] Valyrakis, M., Michalis, P., Zhang, H. 2015a. A new system for bridge scour monitoring and prediction. Proceedings of the 36th IAHR World Congress, The Hague, the Netherlands, pp. 1-4.

How to cite: Corrigan, A., Elmubarak, H., Xu, Y., Michalis, P., and Valyrakis, M.: Bridge pier scour hazards assessment using smart-spheres, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8341, https://doi.org/10.5194/egusphere-egu2020-8341, 2020.

Road infrastructure is expected to face extreme pressure due to ageing and climatic extremes [1] as evident by recent cases of flash floods followed by drought periods. Among the most vulnerable elements of civil infrastructure are considered to be the road embankments that are not expected to withstand the prospective flood extremes. Seepage and internal erosion patterns inside the body of embankments are difficult to be assessed with conventional methods (e.g. visual inspections) and therefore go undetected leading to irreversible effects with major disruption and costs to road asset owners and maintainers. Flood-induced hazards can cause sudden collapse of bridge infrastructure without prior warning, and with significant socio-economic impacts [2]. Various sensor applications have focused on the development of monitoring systems to assess in real-time hydro and geo-hazards [2, 3, 4, 5]

This study focuses on the development and application of a real-time geo-monitoring system at a pilot road embankment in Scotland (UK) to remotely assess the evolving characteristics of hydro-hazards. The system will also provide early warning of such hazards and timely information to asset owner for proactive actions and early maintenance to avoid irreversible and costly major rehabilitation activities.

[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 (ICONHIC2019), Chania, Greece, 23–26 June 2019, pp.1-9.

[2] Koursari, E., Wallace, S., Valyrakis, M. and Michalis, P. (2019) The need for real time and robust sensing of infrastructure risk due to extreme hydrologic events, 2019 UK/ China Emerging Technologies (UCET), Glasgow, United Kingdom, 2019, pp. 1-3. doi: 10.1109/UCET.2019.8881865

[3] 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

[4] Valyrakis M. and Alexakis, A. (2016) Development of a “smart-pebble” for tracking sediment transport. International Conference on Fluvial Hydraulics River Flow 2016, St. Liouis, MO, 8p.

[5] Michalis, P., Saafi, M. and M.D. Judd. (2012) Integrated Wireless Sensing Technology for Surveillance and Monitoring of Bridge Scour. Proceedings of the 6th International Conference on Scour and Erosion, France, Paris, pp. 395-402.

Acknowledgements: This research project has been funded by Transport Scotland, under the 2019/20 Innovation Fund (Scheme ID19/SE/0401/032).

How to cite: Michalis, P., Xu, Y., Koursari, E., Wallace, S., and Valyrakis, M.: Innovative geo-monitoring system to assess hydro-hazards at road embankments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10218, https://doi.org/10.5194/egusphere-egu2020-10218, 2020.

Ageing infrastructure alongside with extreme climatic conditions pose a major threat for the sustainability of civil infrastructure systems with significant societal and economic impacts [1]. A main issue also arises from the fact that past and existing methods that incorporate the risk of climatic hazards into infrastructure design and assessment methods are based on historical records [2].

Major flood incidents are the factor of evolving geomorphological processes, which cause a drastic reduction in the safe capacity of structures (e.g. bridges, dams). Many efforts focused on the development and application of monitoring techniques to provide real-time assessment of geomorphological conditions around structural elements [1, 3, 4]. However, the current qualitative visual inspection practice cannot provide reliable assessment of geomorphological effects at bridges and other water infrastructure.

This work presents an analysis of the useful experience and lessons learnt from past monitoring efforts applied to assess geomorphological conditions at bridges and other types of water infrastructure. The main advantages and limitations of each monitoring method is summarized and compared, alongside with the key issues behind the failure of existing instrumentation to provide a solution. Finally, future directions on scour monitoring is presented focusing on latest advances in soil and remote sensing methods to provide modern and reliable alternatives for real-time monitoring and prediction [5, 6] of climatic hazards of infrastructure at risk.

References

[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 (ICONHIC2019), Chania, Greece, 23–26 June 2019.

[2] Pytharouli, S., Michalis, P. and Raftopoulos, S. (2019) From Theory to Field Evidence: Observations on the Evolution of the Settlements of an Earthfill Dam, over Long Time Scales. Infrastructures 2019, 4, 65.

[3] Koursari, E., Wallace, S., Valyrakis, M. and Michalis, P. (2019). The need for real time and robust sensing of infrastructure risk due to extreme hydrologic events, 2019 UK/ China Emerging Technologies (UCET), Glasgow, United Kingdom, 2019, pp. 1-3. doi: 10.1109/UCET.2019.8881865

[4] Michalis, P., Saafi, M. and M.D. Judd. (2012) Integrated Wireless Sensing Technology for Surveillance and Monitoring of Bridge Scour. Proceedings of the 6th International Conference on Scour and Erosion, France, Paris, pp. 395-402.

[5] Valyrakis, M., Diplas, P., and Dancey, C.L. (2011) Prediction of coarse particle movement with adaptive neuro-fuzzy inference systems, Hydrological Processes, 25 (22). pp. 3513-3524. ISSN 0885-6087, doi:10.1002/hyp.8228.

[6] Valyrakis, M., Michalis, P. and Zhang, H. (2015) A new system for bridge scour monitoring and prediction. Proceedings of the 36th IAHR World Congress, The Hague, the Netherlands, pp. 1-4.

How to cite: Valyrakis, M., Michalis, P., Xu, Y., and Latessa, P. G.: Monitoring systems for the assessment of water infrastructure hazards due to extreme climatic conditions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10526, https://doi.org/10.5194/egusphere-egu2020-10526, 2020.

Turbulent flows may destabilise riverbeds and banks, transporting sediment or underscouring hydraulic infrastructure built near water bodies. For example, scour is a significant challenge that can affect the stability of bridge foundations as the transport of sediment around a bridge pier may cause structural instabilities and catastrophic failures. The aim of this study is to use machine learning techniques & data driven algorithms to predict how energetic turbulent flow events can result in the removal of individual sediment grains, resting on the bed surface or on the protective armour layer around built infrastructure. 

The flume experiments involve flow and particle motion data gathering campaigns [1]. Turbulent flow data are collected upstream the exposed target particle using acoustic Doppler velocimetry. Particle's motion data are gathered using novel micro-electro-mechanical sensors embedded within its waterproof casing, for a range of flow conditions. The obtained data are fed into neural networks having distinct algorithmic complexity (inputs, levels and neutrons). A comparison of the performance of the various model architectures, as well as with past ones [2], is conducted to identify the optimal predictive algorithm for the configuration tested. Sensor data fusion combined with artificial intelligence techniques are shown to provide a unique tool for live and robust data-driven predictions to help tackle significant engineering problems, such as geomorphological activity and scouring of infrastructure (eg bridge piers and embankments) due to turbulent flows, which become increasingly more challenging, under the scope of climate change and intensifying extreme weather hazards.

References

[1] Valyrakis, M., Farhadi, H. 2017. Investigating coarse sediment particles transport using PTV and “smart-pebbles” instrumented with inertial sensors, EGU General Assembly 2017, Vienna, Austria, 23-28 April 2017, id. 9980.

[2] Valyrakis, M., Diplas, P., Dancey, C.L. 2011b. Prediction of coarse particle movement with adaptive neuro-fuzzy inference systems, Hydrological Processes, 25 (22). pp. 3513-3524. ISSN 0885-6087, doi:10.1002/hyp.8228.

How to cite: Ahmed, M., Farhadi, H., Michalis, P., and Valyrakis, M.: Geomorphological hazards assessment using machine learning and data fusion , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20770, https://doi.org/10.5194/egusphere-egu2020-20770, 2020.

In 1995, divers noticed a strange circular pattern on the seabed off Japan. The geometric formations mysteriously appeared and dissolved, and no-one knew what made them. Finally, the creator of these remarkable formations was found: a new species of pufferfish from the genus Torquigener. The male puffer fish executes a design of mathematical perfection in the form of ornate circles. As he swims along the seabed, he laboriously flaps his fins and rearranges the sand, creating the geomorphic feature dubbed crop circle by the pioneers who first noticed them. The significance to understand the puffer fish design is magnified when we consider that the nest is able to maintain its morphological features for long periods even though it is built entirely of mobile particles in an area where the flow does not stop.

As a relatively new discovery, the exact reasons behind why the pufferfish spends such a long time constructing and cultivating the nest it still a question that is shrouded in a substantial amount of mystery. Male puffer fish spend many days caring for the eggs, the only puffer fish genus to be overserved doing so; suggesting that Torquigener place an unusually large emphasis on ensuring the survival of their eggs. It is hypothesised that the nest is created as a mating display, as female puffer fish will visit the site, presumably assessing various characteristics of the nest. It is not known exactly what parameters the females judge the nest on; whether it be size, symmetric properties or decorative choice. However, due to some basic hydrodynamic experiments performed by Hiroshi Kawase, there is some evidence to suggest that there may be more to building the nest than solely attracting a mate.

Several questions therefore arise regarding the nest. Is there an evolutionary reason that male puffer fish build these nests? Which characteristics of a nest make it attractive to female puffer fish? Are the eggs safer in a nest, perhaps from incoming currents? How exactly does fluid flow through nest, and can it be replicated and simulated? This project begins to tackle these questions through a numerical investigation (CFD) of the fluid flow through the nest in order to identify key fluid dynamic features, which may play a significant role in egg incubation and spawning using Star CCM+.

How to cite: Clement, L., Campbell, C., Hasibi, A., Zare-Behtash, H., and Valyrakis, M.: Scour-resilient bio-inspired geomorphic designs: The Male Japanese Puffer Fish Nest, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21592, https://doi.org/10.5194/egusphere-egu2020-21592, 2020.

Fine particles represent an important fraction of the mass of sediment transported by rivers (Syvitski et Saito, 2007). Suspended load is therefore a significant contributor to the erosion of landscapes. Fine particles are often considered to travel through streams and rivers with minimal interaction. Yet, recent field campaigns demonstrate that fine particles interact with the bed through erosion and deposition (Misset et al., 2019). Based on this observation, we develop a simplified model of suspended transport that accounts explicitly for the exchange of small particles between the river bed and the water column. This model involves three parameters: (1) a threshold water level above which the flow starts eroding fine particles from the bed, (2) an erosion rate that characterizes the intensity of sediment entrainment, and (3) a characteristic settling time accounting for sediment deposition.

We then test the validity of the model against data collected in the Capesterre catchment, a small catchment (16.6 km2) monitored by the Observatory of Water and Erosion in the Antilles (ObsErA). Located in Basse-Terre Island (Guadeloupe archipelago, lesser Antilles arc), this catchment is regularly exposed to floods induced by hurricanes and tropical storms (Allemand et al., 2014; Gaillardet et al., 2011). The discharge and the turbidity of the river are measured with a time step of 5 minutes. Using in-situ calibrations, we convert the turbidity signal into a suspended load concentration. The resulting data reveal that the transport of fine sediment is highly intermittent: the concentration of suspended particles rises abruptly when the river height exceeds a threshold of the order of 25cm, corresponding to a discharge of 5 m³/s. The concentration decrease following the flood peak is more gentle. The resulting concentration-discharge curve takes the form of a counter-clockwise hysteretic loop, as commonly observed in many streams (Williams, 1989).

How to cite: Roque-Bernard, A., Lucas, A., Gayer, E., Allemand, P., and Lajeunesse, E.: Suspended load transport in a small tropical catchment: data analysis and modeling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5289, https://doi.org/10.5194/egusphere-egu2020-5289, 2020.

Despite the fact sediment transport has been studied for decades, there is still a need to gain a further insight on the nature and driving mechanisms of bed particle motions induced by turbulent flows, for the low transport stages where the particle transport is relatively intermittent. A custom designed and prototyped instrumented particle, embedded with inertial sensors is used herein to study its transport over hydraulically rough bed surfaces. The calibration and error estimation for its sensors is also undertaken before starting the experiments, to ensure optimal operation and estimate any uncertainties.

The observations and results of this research are obtained from experiments carried out at the University of Glasgow 12 meters long and 0.9 meters wide, tilting and water recirculating flume. The flume walls comprise of smooth transparent glass that enables observing particle transport from the side (also with underwater video cameras) and the bed surface generally is layered with coarse gravel.

The particle is initially located at the upstream end of the test configuration, fully exposed to the uniform and fully developed turbulent channel flow. The top and side cameras are set in their suitable positions to monitor and study the behaviour of particle motion by capturing the dynamical features of sediment motion and to not interfere with flow field that pushes particle downstream. 

Using the sensor data to calculate the kinetic energy for a range of sets of sediment transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of particle transport features, such as particle’s total energy, are generated which give information about particle interaction with the surface bed during its motion. In addition, the effects of different flow rates, particle densities on particle energy are assessed.

How to cite: Al-Husban, Z. and Valyrakis, M.: Assessing sediment transport energetics with instrumented particles for above threshold of motion turbulent flows, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21727, https://doi.org/10.5194/egusphere-egu2020-21727, 2020.

Classically, for free surface flows of binary granular mixture, large particles migrate at the top of the flow while small ones percolate to the bottom. The key mechanisms at the origin of this segregation behavior have been identified as a combination of squeeze expulsion and kinetic sieving (Savage & Lun J. Fluid Mech. 1988). In this case, the segregation process is governed by the gravity. We discovered here by means of numerical simulations a new segregation pattern in high speed granular flows where size segregation is driven mostly by granular temperature gradients rather than gravity, which highlight the complexity of providing a complete description of segregation processes.

High speed granular flows are obtained by means of discrete numerical simulations (DEM) in a confined geometry with lateral frictional side-walls. Recently, Brodu et al. (Phys. Rev. E 2013, J. Fluid Mech. 2015) highlighted that this confined geometry allows to produce steady and fully-developed flows at relatively high angles of inclination, including a rich and broad variety of new regimes. In particular, they showed the existence of supported regimes, characterized by a dense and cold (in terms of granular temperature) core floating over a dilute and highly agitated layer of grains, accompanied with longitudinal convection rolls.

We performed extensive numerical simulations within this geometry with binary mixture of spheres with a given size ratio of 2. We analyzed segregation patterns of steady and fully-developed flows for inclination angles ranging from 18° to 50° and various mixture proportions of large particles ranging from 0 to 100%. We evidenced a new segregation pattern that emerge in the supported flow regimes: large particles no longer accumulate in the upper layers of the flow but are trapped in the dense core and localized at the center of the convection rolls. The strong temperature gradients that develop between the dense core and the surrounding dilute layer seem to govern the segregation mechanism. The accumulation of large particles in the dense core, which is the fastest region of the flow, also tends to enhance the total mass flux in comparison with similar mono-disperse flows.

How to cite: Valance, A., Delannay, R., and Neveu, A.: Unexpected segregation patterns in high speed granular flows, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21839, https://doi.org/10.5194/egusphere-egu2020-21839, 2020.

Scour is the leading cause of bridge collapse worldwide, being responsible for compromising the stability of structures’ foundations. Scour and erosion can take place without prior warning and cause sudden failure. This study describes engineering measures and complications encountered during construction for a case study in the Scottish Borders (A68 Galadean Bridge). The bridge studied carries the A68 road across the Leader Water.

Transport Scotland’s structures crossing or near a watercourse are subject to a two-stage scour assessment following the Design Manual for Roads and Bridges (DMRB) BD97/12 Standard, ‘The Assessment of Scour and Other Hydraulic Actions at Highway Structures’. Structures identified at risk are monitored through Reactive Structures Safety Inspections following events likely to increase water levels. The most common form of monitoring includes visual inspections, however, monitoring sensors are being currently implemented and trialled at locations at high risk of scour.

Scour in the area was identified during a Reactive Structures Safety Inspection, following which a weekly scour monitoring regime was established, alongside further Reactive Structures Safety Inspections, until remediation measures were put in place.

Despite the bridge being constructed perpendicular to the Leader Water, meandering of the watercourse was detected upstream. Sediment transport was the cause of an island formation immediately upstream of the structure. Non-uniform flow and secondary, spiral currents, resulting from the formation of the bend were exacerbating scour and erosion in the area. The design of the remediation measures included the implementation of rock rolls alongside the affected riverbank. However, during construction, increased water levels resulting from thawing snow resulted in the collapse of a significant portion of the embankment supporting the structure’s abutment and the A68 road, prior to the realisation of the remediation measures. An emergency design revision was required and emergency measures had to be enforced.

The urgency of the works led to a two-phase approach being followed for the design and construction of the scour measures in the affected area. The first phase included the construction of a platform in front of the affected road embankment and the implementation of rock rolls to provide scour protection. The two-phase approach ensured the infrastructure at risk was protected from further deterioration while the reconstruction of the embankment was being designed.

The second phase of works included the reconstruction of the affected road embankment, for which the anticipated total scour depth was taken into account.

References:

Koursari E and Wallace S. 2019. Infrastructure scour management: a case study for A68 Galadean Bridge, UK. Proceedings of the Institution of Civil Engineers – Bridge Engineering, https://doi.org/10.1680/jbren.18.00062

Acknowledgements:

The authors would like to acknowledge Transport Scotland for funding this project.

How to cite: Koursari, E., Wallace, S., Michalis, P., Xu, Y., and Valyrakis, M.: A Case Study for Infrastructure Scour Management, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22209, https://doi.org/10.5194/egusphere-egu2020-22209, 2020.

Blowout is a common landform on sandy grassland in semi-arid area and part of semi-humid area, and it is the symbol of the activation of fixed dune and the primary manifestation of desertification. This paper selected the south edge of Otingdag Sandy Land as the research area, and used WindSonic and high-precision RTK GPS to measure the airflow and topography of three blowouts with different morphology on the fixed dune. Meanwhile, combining with the image data and meteorological data,we analyzed the morphology evolution process of the three different blowouts and discussed the relationship between airflow and morphology of blowouts. The results showed that the northwest, west and southwest winds were dominant in the study area, and the west wind among them was the most frequent; The average annual wind speed tends to decrease, and the wind direction gradually tends to be stable and unidirectional, which is consistent with the direction of movement of the blowout in this area; From the air inlet to the top of the sand accumulation area, each blowout experienced the process of diffusion deceleration, convergence acceleration, separation deceleration and gradual acceleration along the long axis of the blowout, but the location that highest or lowest wind speed occurred were not the same in different blowout; The relationship between the wind direction and the long axis of blowout determines the airflow pattern inside blowouts. When the airflow diagonally enters the blowout, the airflow pattern tends to be complicated, and the deceleration and acceleration zone in blowout are obviously deviated. After the airflow enters the blowout, the wind speed and direction change obviously, which affects the spatial pattern of erosion or accumulation and further alters the morphology of the blowout. The morphology also in turn reacts on the near-surface airflow, which results in the response and feedback of the morphology and dynamics of the blowout.

How to cite: Zhou, Y. and Hasi, E.: Morphodynamic processes of blowout on the fixed dune, China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13595, https://doi.org/10.5194/egusphere-egu2020-13595, 2020.

Climate change has resulted in increased storminess and sea-level change that affects the morphodynamics of bays worldwide, impacting both the ecosystem and local infrastructure. This study explores the impact of differing storm winds on the sediment budget of the Bay of Cadiz. The Bay of Cadiz is a highly altered coastal lagoon located in Southwest Spain surrounded by ports, navigation channels, and urban developments and is of high socioeconomic and environmental importance. The human interactions with the bay have already caused morphological impacts, which could be exacerbated by increased storminess. Potential impacts on the sediment budget of the Bay of Cadiz will be modeled using a Delft3D model previously calibrated and tested using field data from December 2011 to January 2012. The model will consider a variety of storm wind scenarios and observe their impacts on sediment transport within the bay, identifying sources and sinks. This will help to estimate the potential impacts of climate change and increased storminess on the bay and the surrounding areas.

How to cite: LeBlanc, M., Plomaritis, T., and Lopez-Ruiz, A.: Response of a coastal lagoon sediment budget to extreme events and climate change implications: The case of the Bay of Cadiz, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21783, https://doi.org/10.5194/egusphere-egu2020-21783, 2020.

One of the primary challenges of understanding hydro-geomorphic connectivity is to move from static to dynamic representations of connection. This is particularly important when linkages are made between hydro-geomorphic connectivity and habitat. In response to external drivers, notably extreme events, the spatial locations of suitable habitat within an ecosystem may migrate spatially, potentially rapidly. A resilient ecosystem, in one sense, is one where organisms can either “weather-it-out” or migrate to newly suitable habitat to find temporary refuge from those extreme events. In this paper, I show that is it the spatio-temporal evolution of connectivity that determines the resilience of braided stream ecosystems to geomorphic perturbation. Using a validated model of the spatial distribution of instream macroinvertebrate habitat, that combines both known organism preferences with the risks of geomorphic perturbation, I show that during high flow events, suitable habitat shifts rapidly from the primary braid plain channels to secondary ones. The connectivity between primary and secondary channels determines the extent to which secondary channels can be used as refugia; but this connectivity varies continually during the flow event. This can be captured in connectivity metrics based upon notions of percolation. The work has important implications for stream management. First, it shows that the availability of habitat within an ecosystem at high flows is not a sufficient descriptor of the system resilience. The ability of organisms to access suitable habitat as flow rises, and to return to the low flow channel as it falls, is critical; connectivity is primordial. Second, it emphasises that a focus on connectivity as a static state or metric is not sufficient to describe the extent to which a system is resilient. The accessibility of habitat suitable zones at high flows depends upon the how connectivity evolves during the event, which controls accessibility. Thirdly, analyses of connectivity, and wider assessment of stream resilience, need to couple geomorphology and hydrology, and not just focus on environmental flows. The latter provide only a very partial representation of connectivity.

How to cite: Lane, S.: Dynamic connectivity as a determinant of the resilience of stream habitat to geomorphic perturbation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18770, https://doi.org/10.5194/egusphere-egu2020-18770, 2020.