EGU General Assembly 2024  

Over the Tertiary, the uplift of the Himalaya combined to the development of the monsoon generated the largest erosion basins of the planet. More than 80% of the erosion is exported to the Bay of Bengal by the Ganga-Brahmaputra river system and generates turbidity currents which convey detrital sediment building the Bengal Fan. In the modern Himalaya, the monsoon rainfall and tectonic processes shape the erosion pattern. The monsoon seasonal precipitation ensures efficient transport of sand-rich sediments in the basin despite long distances through a very flat floodplain and delta. Rapid transport also acts as a limiting factor for weathering as it reduces residence time in the floodplain but favors efficient carbon burial.

The IODP Expedition 354 drilled the Bengal Fan with seven sites over a 320 km E-W transect at 8°N. This construcs a composite sedimentary record of Himalayan erosion over the Neogene and Quaternary. Sediments are predominantly composed of turbidites generated from the Ganga-Brahmaputra delta. Turbiditic sediments show mineralogical, geochemical and isotopic characteristics which reveal a close analogy with those of the modern Ganga-Brahmaputra river. Sand deposition is dominant and is present in several meters thick sand lobe as well as in levee turbidite (Bergmann et al. 2020). Sand was used to determine average erosion rates of the Himalaya using quartz in situ concentrations of cosmogenic 10Be. Those show stable rate in spite of the onset of a more unstable climate from the Pliocene to the Pleistocene (Lenard et al. 2020).

Major element concentrations and Sr-Nd isotopic compositions of turbidite samples reflect combined effects of geological sources exposed to erosion, weathering and mineral sorting during transport. Deciphering these controls, based on the comparison between turbidite samples and modern river sediments of the Ganga and Brahmaputra basin reveals evolution from Miocene to present. Changes appear in the abundance of detrital carbonates likely reflecting decreasing exposition of the Tethys Himalaya to erosion since Miocene. Clear increase in the silicate Na and Ca concentrations from Miocene to Pleistocene indicates major change in the weathering conditions in the basin which can be related to longer residence time of the sediment in the floodplain and lower erosion ratesin the Miocene.

Bergmann et al. 2020, G. cube 10.1029/2019gc008702
Lenard et al. Nat Geosc. 2020, doi:10.1038/s41561-020-0585-2

How to cite: France-Lanord, C., Galy, A., Galy, V., Huyghe, P., Lavé, J., Lenard, S., Limonta, M., Rigaudier, T., Spiess, V., and Tachambalath, A.: The Neogene record of Himalayan erosion in the Bengal Fan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19206, https://doi.org/10.5194/egusphere-egu24-19206, 2024.

Quantifying landscape form can provide crucial insight into the interactions between tectonics and climate. River long profile morphology, quantified by metrics such as channel steepness, is the most commonly used tool to investigate topographic form, with many studies relating long profile morphology to uplift rate, precipitation, sediment properties, or lithology, for example. River long profiles record the signal of external forcing over large spatial scales (i.e. tens of kilometres). This has many advantages: for example, it is a convenient scale for analysing variations in large-scale processes, such gradients in tectonic uplift. It also means that high resolution digital elevation models (DEMs) are not required and therefore river long profiles can be extracted globally. However, analysis of river long profiles over tens of kilometres can also result in signal smoothing and subsequent loss of finer scale tectonic or climatic signatures encoded into the landscape.

Tectonic and climatic processes do not only leave their fingerprint in the long profiles of rivers. Hilltops, hillslopes, and valleys make up the majority of Earth’s landscapes by area, yet their morphology has received much less attention than that of rivers. This is in part due to the difficulty in accurately extracting hilltops and valley morphology from DEMs, especially on a global scale. Here, I show that we can now extract hilltop and valley metrics from high-resolution (< 15 m) DEMs over orogenic to continental scales using new topographic analysis techniques and high-performance computing facilities. I argue that by combining hilltop, hillslope, and valley metrics, we can obtain more information about tectonic and climatic processes than from river profiles alone.

How to cite: Clubb, F.: Going beyond the river long profile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6103, https://doi.org/10.5194/egusphere-egu24-6103, 2024.

Tidal channels are key players in ecogeomorphological dynamics of coastal wetlands, controlling the exchange of water, sediment and nutrient fluxes between low-lying coastal areas and the open sea. Traditionally seen as stable features, the importance of migrating and abandoned channels has been often overlooked. Yet, the constant evolution of tidal channels significantly influences sediment reworking in coastal wetlands and reduced flow velocities within abandoned channels promote particle settling thus rapidly storing large volumes of sediment. Moreover, reach abandonment may lead to the reorganization of the channel network, thus leading to sudden changes in flux dynamics at the basin scale. Hence, the characterization of channel-fill deposits is a critical step for a better understanding of the mechanisms that lead to channel abandonment and consequent network reorganization.

To this aim, we conducted a detailed analysis of the sedimentary features and the related depositional processes in abandoned tidal channels in the microtidal Venice Lagoon, Italy. We collected undisturbed sedimentary cores within abandoned channels identified from aerial images taken in the last 70 years. Cores were longitudinally cut and photographed for classical sedimentary facies analysis and identification of the main depositional environments. Cores were then subsampled at 5 cm intervals and prepared for different laboratory analyses, including organic matter estimation through Loss-On-Ignition and particle size distribution using laser diffractometry.

By combining facies and laboratory analyses, different depositional environments can be readily identified and characterized. The deposits accumulated during the channel abandonment phase are usually floored by a layer rich in shell and shell fragments related to the channel lag, which in most cases overlies sandy-laminated tidal flat deposits. Instead, channel-fill deposits consist of dark grey, organic-rich mud without any visible sedimentary structures. Massive mud can be locally mixed with very fine sand, and close to the lag they tend to become richer in coarser fractions. Moreover, channel-fill deposits are characterized by abundant submillimetric vegetation debris and by an almost constant organic matter content all along the deposit thickness. Our analysis provides a distinctive characterization of the features of channel-fill deposits and is foundational to the comprehension of the processes that lead to channel abandonment and infill.

How to cite: Tognin, D., Puppin, A., Ghinassi, M., D'Alpaos, A., and Finotello, A.: Characterization of channel-fill deposits in coastal wetlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-849, https://doi.org/10.5194/egusphere-egu24-849, 2024.

Quantifying landscape form can provide crucial insight into the interactions between tectonics and climate. River long profile morphology, quantified by metrics such as channel steepness, is the most commonly used tool to investigate topographic form, with many studies relating long profile morphology to uplift rate, precipitation, sediment properties, or lithology, for example. River long profiles record the signal of external forcing over large spatial scales (i.e. tens of kilometres). This has many advantages: for example, it is a convenient scale for analysing variations in large-scale processes, such gradients in tectonic uplift. It also means that high resolution digital elevation models (DEMs) are not required and therefore river long profiles can be extracted globally. However, analysis of river long profiles over tens of kilometres can also result in signal smoothing and subsequent loss of finer scale tectonic or climatic signatures encoded into the landscape.

Tectonic and climatic processes do not only leave their fingerprint in the long profiles of rivers. Hilltops, hillslopes, and valleys make up the majority of Earth’s landscapes by area, yet their morphology has received much less attention than that of rivers. This is in part due to the difficulty in accurately extracting hilltops and valley morphology from DEMs, especially on a global scale. Here, I show that we can now extract hilltop and valley metrics from high-resolution (< 15 m) DEMs over orogenic to continental scales using new topographic analysis techniques and high-performance computing facilities. I argue that by combining hilltop, hillslope, and valley metrics, we can obtain more information about tectonic and climatic processes than from river profiles alone.

How to cite: Clubb, F.: Going beyond the river long profile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6103, https://doi.org/10.5194/egusphere-egu24-6103, 2024.

How to cite: Townsend, D., Leyland, J., Kassem, H., Thompson, C., and Townend, I.: Observations from a constantly changing nearshore zone in a mixed sediment bay , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6586, https://doi.org/10.5194/egusphere-egu24-6586, 2024.

Luminescence is a powerful dating technique that is increasingly being used as a new tool to investigate surface processes. In the past decade, it has been used successfully for instance to estimate virtual sediment velocity in rivers, sediment storage time in floodplains, and to trace sediment sources (McGuire & Rhodes, 2015; Gray et al., 2018; Sawakuchi et al., 2018; Guyez et al., 2022; Guyez et al., 2023). As part of ongoing development, here we quantify sediment transport and catchment-wide erosion rates in natural systems using luminescence. For this purpose, single-grain post infrared-infrared (pIRIR) equivalent doses of felspars from modern floodplain deposits were measured in several catchments in the Southern Alps of New Zealand and compared to catchment-wide erosion rates derived from ¹⁰Be cosmogenic nuclide concentrations measured in fluvial quartz grains.

The fraction of grains that were well-bleached before their burial in the modern floodplain was calculated, as well as the fraction of grains with a saturated luminescence signal. Signal distribution was characterised using the central age model.

Our findings indicate that the luminescence signal is characterized by few well-bleached grains and lots of grains with a high luminescence signal where erosion rates are high. On the other hand, in catchments with lower erosion rates, bleaching appears to be more pervasive, resulting in an overall lower luminescence signal. Therefore, we hypothesize that bleaching efficiency is related to erosion rates.

To test the relationship between luminescence, bleaching, erosion, and transport processes, we include the luminescence signal of individual grains in a landscape evolution model that already takes into account the concentration of cosmogenic nuclides (Carretier et al., 2023). By tracking both signals in an evolving stream basin, the model helps better understanding the relationship between erosion and luminescence signal, on longer time scales. Single-grain pIRIR equivalent holds promise as a new method for measuring erosion and sediment transport.

How to cite: Guyez, A., Bonnet, S., Carretier, S., Wilkinson, C., Reimann, T., Norton, K., and Wallinga, J.: Using single-grain feldspar luminescence signal and modelling to study landscapes erosion rates and sediment transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15791, https://doi.org/10.5194/egusphere-egu24-15791, 2024.

Suspended sediment poses a risk to human and natural systems in terms of compromising water quality, flood hazard, hydropower production, and aquatic habitats. In many rivers the bulk of annual suspended sediment yield is mobilised and transported during (extreme) episodic runoff. Understanding such sediment-discharge events, including their drivers, may inform management strategies aimed at mitigating potential detrimental effects. Event-based analysis of local time series of suspended sediment transport has become a common approach to infer the dominant drivers and processes of sediment dynamics at the catchment scale. The increasing availability of detailed and continuous monitoring time series data enables us to use machine-learning techniques to identify groups of similar events, i.e. event types, and test whether and how these groups reflect similar catchment conditions and hydro-meteorological drivers. 

We present an approach which automatically detects, characterises and clusters sediment-discharge events. Hydrograph separation is used to automatically detect events, which are then filtered based on suspended sediment magnitude. The detected events are subsequently characterised with a selection of metrics, which are transformed into uncorrelated event characteristics with principal component analysis. Based on these characteristics events are clustered using a Gaussian mixture model. Finally, the identified event types are interpreted using catchment metrics describing antecedent conditions, hydrometeorological forcing, and catchment freezethaw state and snowcover.

Applying our approach to a high alpine, glaciated catchment we find that the event regime in the catchment is mainly defined by event magnitude, hysteresis and event shape complexity. However, for the clustering suspended sediment and streamflow magnitude, and event shape complexity are the most important factors, whereas sediment discharge hysteresis is less relevant. The four identified event types are attributed to (1) compound rainfall-melt extremes, (2) glacier and seasonal snow melt, (3) freezethaw-modulated snow-melt and precipitation events, and (4) late season glacier melt. 

Our approach enables event-based analysis of riverine sediment fluxes, by detecting and grouping similar events together, which can in turn be interpreted to understand under which conditions episodic sediment fluxes occur in the target catchment.

How to cite: Skålevåg, A., Korup, O., and Bronstert, A.: Identifying sediment-discharge event types with a data-based clustering approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15955, https://doi.org/10.5194/egusphere-egu24-15955, 2024.

How to cite: Aarnink, J., Rouge, F., Fornari, A., and Ruiz-Villanueva, V.: UAV-based tracking of floating wood during a flood , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20657, https://doi.org/10.5194/egusphere-egu24-20657, 2024.

Along the Chilean continental margin, where the active Nazca plate subducts under the South American plate, large deposits of gas hydrates trapped in marine sediments can be observed in seismic profiles (from Valparaíso to Patagonia), which may be affected by the increase in deep-water temperature due to climate change. This could trigger a massive release of methane gas into the marine environment and the atmosphere with negative effects on the environment, mainly through dissociation of the hydrates and/or direct migration to the seafloor through faults.

In this study, new multichannel seismic data located off Chiloé Island (∼42°S) are presented, and for the first time a BSR parallel to the continental margin (north-south) is analysed. Here, an efficient sediment subduction occurs where the young oceanic Nazca plate (5-25 Ma) subducts beneath the continental plate along Chiloé Island. In addition, an integrated analysis to better understand the hydrological and hydrothermal system in this area included previous geophysical and geological datasets, such as a) bathymetry, b) geothermal gradient calculated from gas hydrate distribution boundaries, and c) thermal conductivities. 

The results show a continuous and strong BSR along the entire seismic profile MGL1701-27 (approximately 27 km long), where large deformations, fractures and faults occur, favouring the flow of carbon-rich fluids from the depths, which subsequently form the gas hydrate layer. The large amount of gas hydrate present in the marine sediments off the coast of Chiloé Island is impressive. Velocity analysis of seismic profile MGL1701-27 indicates gas hydrate concentration values of up to 25% of the total rock volume, the highest estimates obtained at the Chilean margin. In addition, a peak in the geothermal gradient is related to deep faults that allow the passage of hot fluids from deeper strata to the seafloor.  Finally, a large amount of free gas is estimated beneath the BSR, which enhances its intensity and continuity in the seismic profile.

Our results provide valuable information for current and future studies related to climate change (methane storage), hydrothermal circulation, seismicity, gas hydrate stability and fluid venting in this natural laboratory, since Chiloé Island is located at the southern boundary of the rupture zone of the largest earthquake in recorded history (the Mw 9.5 Valdivia earthquake), the implications of which have yet to be fully elucidated.

How to cite: Villar-Munoz, L., Vargas-Cordero, I., Tinivella, U., Giustiniani, M., P. Bento, J., Bangs, N., and Contreras-Reyes, E.: The highest gas hydrate volume estimate found in the sediments of the Chilean margin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4165, https://doi.org/10.5194/egusphere-egu24-4165, 2024.

Wave action and seafloor scouring, likely from Hurricane Ivan, exposed an area of baldcypress (Taxoidum distichum) stumps, still in growth position and rooted in terrestrial soil, on the northern continental shelf of the Gulf of Mexico.  This site, known as the Underwater Forest, is located roughly 10 km off the coast of Gulf Shores, Alabama, USA, in approximately 18m of water.  Radiocarbon and optically stimulated luminescence dates from the mud/peat sections of the cores suggest a baldcypress swamp existed between approximately 70-40 ka BP (MIS 3-4) during the Würm glaciation.  Multiproxy analysis of sediments suggests significant geomorphological changes occurred to this backswamp environment overtime, which significantly impacted vegetation assemblage of the area.  Pollen evidence shows a clear transition from a baldcypress/tupelo gum (Nyssa aquatica) community to an alder (Alnus) dominated bar community.  This change suggests a transition to a braided river system, though it remains unclear whether these geomorphological changes resulted from terrestrial sources, marine transgression, or a combination of both.  The final vegetation change is to a more open, marsh environment resulting from sea-level rise.  Tree-ring analysis of the stumps suggest a synchronous death event, likely by burial, which may have also preserved the site.

How to cite: Reese, A., DeLong, K., Harley, G., Garretson, K., Garcia, A., Xu, K., Moran, K., Broome, K., and Bergan, E.: Paleoenvironmental and geomorphological changes in an ancient baldcypress swamp preserved on the Northern continental shelf in the Gulf of Mexico, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4166, https://doi.org/10.5194/egusphere-egu24-4166, 2024.

In this study, we investigate the relationship between subglacial conditions and the presence of ribbed moraines in Norway. Ribbed moraines are low-lying subglacially formed ridges, transverse to glacial flow and numerous processes have been proposed to explain their formation. So far there is no agreement about the formation process but most of them are linked to the presence of subglacial water. We therefore hypothesise that there is a relationship between hydrological conditions at the bed of the Fennoscandian Ice Sheet, and the presence of ribbed moraines. To test this, we extract subglacial conditions from a numerical model of the Fennoscandian Ice Sheet and derive further modelled hydrological conditions using a MATLAB-based hydrological toolbox. Our conditions include: (i) subglacial hydrological sinks, (ii) subglacial hydraulic head, (iii) flow accumulation, (iv) ice thickness, (v) ice-flow velocity, and (vi) basal temperature. We use these data in a presence-absence generalised linear modelling approach, to evaluate the coexistence of ribbed moraines and specific conditions. From this we can infer whether they have a consistent series of conditions which determine their presence. We focus on two areas, a training dataset in Vinstre, South-Central Norway, and a validation dataset in Femunden, Central-Eastern Norway. These sites cover known and well mapped areas of ribbed moraines, which are used as ground truth data. Comparison is possible through superimposing presence-absence predictions on the ground truth data in GIS as a pair of gridded, spatially referenced datasets. In comparing the model output to ground truth data, we aim to provide new assessments of the validity of the many ribbed moraine formation theories. For example, if hydrological conditions prove a poor predictor, then we can consider the presence of water as less likely a prerequisite for the formation of ribbed moraines. 

How to cite: Barnes, T. J., Lilleøren, K. S., Schuler, T. V., and Schmidt, L. S.: Ribbed Moraines and Generalised Linear Modelling: Can modelled ice conditions be used to predict the presence of specific landforms?  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6076, https://doi.org/10.5194/egusphere-egu24-6076, 2024.

Costa Rica is a small humid tropical country with an extension of 51,179 km², it has an extensive network of diverse streams and rivers controlled by diverse environmental and geological conditions. Rugged terrain, active volcanism, and tectonic activity, along with intense and frequent precipitation, result in a dynamic drainage system characterized by a wide array of erosive and depositional fluvial landforms. Over 33% of Costa Rica’s territory is composed of Quaternary-Pleistocene volcanic landforms. These dynamic and high sediment source environments play a crucial role in the economy and society of the country. From the energy supply point of view, over 70% of the country’s electricity generation comes from hydropower plants located within volcanic formations. Mountain and highland volcanic areas are also the main source of drinking water for most of the population that live in the central part of Costa Rica.

Using remote sensing techniques (UAV photogrammetry and satellite imagery), bidimensional hydraulic modelling and raster analysis we analyzed with high-resolution (<1m/pixel) five fluvial-volcanic environments with different environmental conditions: (i) the effects of explosive phreatic eruptions on the channel morphology of the Pénjamo River located on the Rincón de la Vieja Volcano; (ii) severe bank erosion caused by an extreme precipitation event that damaged multiple structures along the Turrialba River, Turrialba Volcano; (iii) alluvial fan geomorphology of the Reventado River and it’s hazard implications to Cartago City, Irazú Volcano; (iv) confined urban streams and vegetation connectivity analysis of San José City, Irazú Volcano; (v) river dynamics and channel morphology  in extinct Pleistocene volcanic formations, San Lorencito River.

The use of the high-resolution assets allowed us to get novel insights on how channel morphology is composed in these extremely dynamic environments. Also, analyze how channels adjust to high sediment yield due to climatic or eruptive events. Some main outcomes of our research show that: (i) rivers in these steep environments flow confined mostly with single-thread morphologies and coarse sediments (boulders); (ii) volcanic phreatic eruptions generated hyperconcentrated flows (lahars) that caused severe bank erosion; (iii) vegetation in confined urban rivers play a key role in ecosystem management and environmental development; (iv) rivers that flow from active volcanoes transport extreme amounts of sediments and represent a major hazard for populated areas of Costa Rica.

Our results contribute to a better understanding of how river dynamics function under diverse volcanic environments of the country. Since over 40% of the country’s population lives within volcanic formations the data we provide contributes for a better environmental and risk assessment.

How to cite: Cui, J., Granados, S., and Surian, N.: High-resolution fluvial geomorphology of dynamic volcanic environments of Costa Rica, Central America, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12134, https://doi.org/10.5194/egusphere-egu24-12134, 2024.

Mountainous regions are important headwater regions to sustain environmental and human water demands. The morphologies of these headwater catchments control their hydrological response and affect the water supply to downstream. In this study, more than 3.3×10⁷ headwater catchments are extracted. These cover most of the mountainous regions between 60°S and 60°N and their areas range from 0.5 km² to 2 km². Several morphological features closely related to hydrological response and sediment dynamics, such as width function and Melton number, are estimated for the catchments. Particularly, in order to ensure the accuracy of the estimated parameters, two new algorithms are developed, including an improved triangular form-based multiple flow direction algorithm as well as a width function algorithm based on a two-segmented-distance strategy and the multiple equidistant belt technique. Subsequently, a dataset of mountainous headwater catchment morphology is generated by adding the climatic and tectonic features corresponding to each catchment. This dataset can help to identify the hydrological similarities between different headwater catchments, which is important for determining the parameters of hydrological models in ungauged catchments. We analyze the relationship between the catchment morphology features and tectonics (e.g., shortening rate) as well as climate variables (e.g., precipitation and temperature). The results show that great differences exist in catchment morphology between tectonically active areas and inactive areas. Furthermore, the relationship between morphology and climatic variables varies depending on the lithology of the region, with the strongest correlation observed in sedimentary regions.

How to cite: Wu, P., Liu, J., and D'Agostino, V.: Global Distribution of Mountainous Headwater Catchments Morphology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12871, https://doi.org/10.5194/egusphere-egu24-12871, 2024.

Southern England has been undergoing subsidence since the end of the Last Glacial Maximum due to the Glacial Isostatic Adjustment of the British Isles. Rivers typically respond to subsidence by aggrading, however many rivers along the coast of Southern England incise at their outlet and exhibit river profile convexities typical of systems experiencing a drop in base level. Studies have suggested that coastal erosion could result in such river morphology. Specifically, numerical modelling studies (Leyland and Darby, 2009; Hackney et al., 2014) have shown that it was only in the Late Holocene when small basins experienced significant channel incision at their outlets.  They demonstrated that this was due to the reduction in the rates of sea level rise which enabled knickpoint recession rates to exceed cliff retreat rates.  

Observations and understanding of the geomorphic controls, including both climatic and topographic drivers, on coastal river outlets remain limited, however. For the first time, we examine the spatial distributions of river outlets in Southern England through digital topographic analysis. In regions with similar lithologies and coastal exposure, we find that channels with the smallest basins incise at their mouth while rivers with the largest basins experience aggradation. This signal aligns to model predictions, assuming that the slope of rivers at the coast decreases with increasing basin size. We further explore the role of lithology on knickpoint magnitude and retreat by testing whether more resistant lithologies slow knickpoint retreat rates. Moreover, we investigate the influence of spatial variations in coastal erosion rates on knickpoint morphology, with greater wave heights and subsidence rates documented in the South West. Finally, we examine whether realistic estimates of coastal erosion can be made by reconstructing river profiles before the initiation of subsidence.  This contribution will enhance our understanding of how rivers respond to rising base levels, which is particularly important given the projected sea level rise in Southern England.

How to cite: Towers, A., Attal, M., Mudd, S., and Clubb, F.: Quantifying the response of rivers to Holocene sea level rise in Southern England, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13101, https://doi.org/10.5194/egusphere-egu24-13101, 2024.

1. Objectives and data

To investigate trends of heavy snowfall attributable to climate change, we use maximum snow depth data calculated during 1951–2010 with a climate model (experimentation by present climate). The Japanese hydrological–meteorological community used a climate simulation model to construct a huge database of hydro-meteorological values (https://www.miroc-gcm.jp/d4PDF/index_en.html), designated as d4PDF. It has data calculated under the present climate and data calculated under a future climate, which are affected by global warming. The "T-year value" is a stochastically and statistically estimated hydrological value for which the return period is T years.

2. Extreme values of snowfall

We used hourly snow depth data of d4PDF around Japan. First, we calculated the annual maximum snow depth at each calculation grid. Because this database consists of ensemble calculations of 50 members, data for 3,000 years (60 years × 50 members) are included. We investigated trends of 50-year values for which the return period is 50 years. Specifically, 50-year snowfall and snow depth were estimated. The annual maximum of snow depth at each calculation grid was calculated. Our research theme evaluates the “T-year value” for which the return period is the T-year is itself, but we calculated it using a non-parametric method at this stage as described below.

• We assume that the population of this database is not stationary. Therefore, for example, for 1951, we use 500 data which consist of data of 10 years (1951–1960) of 50 members.
• A 50-year value is the tenth largest value among 500 descending data.
• For 1952–2010, 50-year values are estimated using the same procedure.

3. Result

Figure 1 presents the time variational 50-year-snow-depth at five grid points in central Japan. Figure 2 shows 50-year values of 24 h snowfall as the same grid points. These show no long clear increasing or decreasing trend. However, after 1985, it is apparent that the 50-year-annual maximum snowfall during 24 h decreases slightly.

4. Future work

Although we describe trends of 1951–2010 herein, we can describe some other results we are investigating now, as presented below.

• Optimal methods for estimating a T-year value require checking for optimal methods among non-parametric methods, methods using annual maxima, and methods using a partial duration series.
• Although we use only a database for present climate conditions, we will present trends of the near future which are affected by global changes.

Figure 1: Time variational 50-year snow depth at five grid points.

Figure 2: Time variational 50-year snowfall at five grid points.

How to cite: Kuzuha, Y., Tachibana, Y., and Mizuki, C.: Extreme values of central Japan snowfall attributable to global climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14468, https://doi.org/10.5194/egusphere-egu24-14468, 2024.

The streampower law is widely used to model the detachment-limited endmember of bedrock channel evolution, in which rivers set their slope mainly to abrade or pluck material from the channel bed. The model suggests a strong sensitivity of river long profiles to tectonic forcing, local bedrock strength, and climate. This has made it a tool of choice for interpreting these signatures in landscapes, regardless of the applicability of detachment limited erosion. For instance, sediment flux can be a major control on channel slope, as channels steepen to evacuate sediment and maintain their bed elevation, which is neglected by the streampower law.

While this is a well understood limitation, the implications become slightly murkier when the streampower law is used in 2D landscape evolution models that add a diffusion law to capture hillslope processes. We find that channel steepness increases with hillslope length, as channels have to steepen in order to erode the hillslope material added to the valley floor by diffusion processes. We show that this approximates some aspects of a transport-limited fluvial erosion model, but neglects others. Importantly, here channel steepening scales exactly with local hillslope properties, rather than those of the entire upstream watershed that would theoretically supply sediment. This has implications for interpretations of river profiles using chi-analysis and model inversion that rely on a version of the streampower law, especially when working between one-dimensional and two-dimensional approaches. We conclude with some extension of the physical significance of our findings, specifically related to constraints on the relationships between streampower erosivity, hillslope diffusivity, and grainsize.

How to cite: Litwin, D., Sklar, L., and Malatesta, L.: Right for the wrong reasons? On hillslope sediment and the streampower model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15831, https://doi.org/10.5194/egusphere-egu24-15831, 2024.

Deeply incised bedrock channels can be found in mountain landscapes across the whole globe. The processes controlling this incision and subsequently gorge formation in bedrock have been discussed in the scientific community but have not been directly observed in an actualistic way. Here, we show the results of an unprecedented LiDAR dataset deciphering the erosive power of a 60,000 m³ hyperconcentrated flow (transition of flood and debris flow). We were able to quantify the lateral bedrock erosion in a narrow limestone gorge with channel widths between 1 and 15 m and a total length of 900 m. The flow laterally eroded up to 1 m massive limestone and widened sections by up to 15 %. The influence of sinuosity, convergence and gradient were tested but found not to influence the local erosivity pattern of the rock walls. We show that single hyperconcentrated flows similar to this one could have a major influence on the effectiveness of bedrock incision in comparison to turbulent flows. Here, we provide a new explanation of the processes of rock gorge formation due to mechanically excited breakout of rock fragments in a massive limestone gorge.

How to cite: Stammberger, V., Jacobs, B., and Krautblatter, M.: Bedrock erosion by hyperconcentrated flows: A quantitative analysis and implications for effective gorge formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16976, https://doi.org/10.5194/egusphere-egu24-16976, 2024.

The complex interrelation between plants and geomorphic processes is described in the concept of biogeomorphic succession. While ecological research on succession and community assembly has transitioned towards functional approaches, studies on functional diversity in biogeomorphic settings, particularly in glacier forelands, remain limited.

In this study, we investigated abundance of vascular plant species and functional traits in an alpine glacier foreland using data from 199 plots. Our objective was to unravel the development of functional diversity during biogeomorphic succession. Specifically, the study determined whether structural shifts in functional diversity are associated with stability thresholds related to plant cover, geomorphic activity, and examined trait spectra for stages of biogeomorphic succession.

Our findings revealed a non-linear trajectory of functional diversity along the plant cover gradient, marked by two distinct structural shifts at 30% and 74% cover, corresponding to established stability thresholds. Along the gradient of geomorphic influence, we observed an increase in functional diversity until 54% of the plot area was affected, beyond which functional diversity declined below the initial level. The analysis of community-weighted means of traits across four stages of biogeomorphic succession determined by plant cover and absence and presence of geomorphic influence revealed significant differences in trait values.

In the transition to the biogeomorphic stage, associated with the identified initial structural shift, there is a shift from a prevalence of above-ground adaptation and reproductive traits, such as leaf longevity, structure, growth form, and mixed reproductive strategies, to an increased dominance of competitor species and traits related to below-ground structures, including root type and structures, as well as vegetative reproduction.

Our results contribute to understanding the relationship between vegetation succession and geomorphic influence by linking them to plant functional traits. This study advances beyond traditional taxonomic investigations by emphasizing functional approaches to biogeomorphic succession. Moreover, the functional trait data used in this study, easily downloadable from a public repository, can serve as a valuable template for future research in (bio)geomorphology, along with the employed methodologies.

How to cite: Haselberger, S., Junker, R. R., Ohler, L.-M., Otto, J.-C., and Kraushaar, S.: Structural shifts in plant functional diversity during biogeomorphic succession: Moving beyond taxonomic investigations in an alpine glacier foreland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1492, https://doi.org/10.5194/egusphere-egu24-1492, 2024.

Ecohydrology describes the effects of hydrological processes on ecosystem structure and functioning and the effects of biotic processes on hydrological processes. Recently, there is an increasing emphasis on the role of megafauna, large mammals and birds, on earth system processes, such as nutrient cycling, energy flows and vegetation patterns. Ecohydrology as a field, however, has not yet considered megafauna as central drivers of hydrological processes but focused strongly on the interactions between hydrological processes and plants and soils. Here, we introduce zoohydrology to emphasize the importance of considering the interactions between wild animals and hydrological processes. This includes both the effects of hydrological processes on the occurrence, behavior and life history of animals as well as the effects animals have on hydrology. In this introductory talk, we will outline different pathways through which hydrology affects megafauna and through which megafauna affect hydrological processes using a systems approach. We will illustrate these pathways with concrete examples from different parts of the world and on different species. For example, the importance of hydrological processes and hydromorpho-dynamics for shaping habitats of endangered species, such as the Ganges freshwater dolphin and Bengal tigers in northern India and Nepal, but also for structuring megafauna community dynamics, such as the example of Gorongosa National Park in Mozambique. We will also exemplify how wild animals can affect central hydrological processes in diverse ways; directly (e.g., species such as beaver and hippo as ecosystem engineers of aquatic systems) and indirectly (e.g., elephants that reduce woody cover at large scales, affecting evapotranspiration). Many effects of animals on hydrological processes remain understudied and are often lacking from hydrological models. By introducing the concept of zoohydrology, we stress the potentially pivotal interactions between central hydrological processes, wild animals and their habitats. To unravel the full complexity of these interactions and assess their true importance, zoohydrology must be advocated among scientists, policy makers and practitioners in order to better address biodiversity conservation and restoration, make the concept of environmental flow needs more concrete, and investigate the consequences of biodiversity restoration on hydrological systems.

How to cite: Cromsigt, J., Larsen, A., and Griffioen, J.: An introduction to the concept of Zoohydrology – the interactions between hydrological processes and wild animals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2096, https://doi.org/10.5194/egusphere-egu24-2096, 2024.

Sponge city is an engineering solution proposed by the Chinese government which aims to deal with urban water issues (e.g., flooding, poor water quality) brought on by climate change and urbanization. Various strategies for sponge city construction are required since environmental constraints differ regionally across the country. To identify regional variations, reveal the inner links between externalities and design elements in sponge city construction, and offer practical suggestions, efforts in two directions are made based on the data of 65 sponge city cases around China, 1) discussing design parameters of four Low Impact Development (LID) facilities, including bioretention cell, permeable pavement, grass swale, and sunken green space, under four regionalization maps of hydrologic, climatic, landform and soil texture factors, and 2) building a holistic Partial Least Squares-Structural Equation Modelling (PLS-SEM) model illustrating the relationship between local characteristics, LID system design, and LID system performance in sponge city construction. The results show that: 1) rainfall and landform factor have great impact on LID facilities design, as the depths tend to be higher in water rich areas and coastal areas. 2) LID types and areas are positively influenced (+0.764) by the total area and permeable portion of a project, and the LID system performance (water quantity and quality control) is negatively impacted (-0.417) by the rainfall amount and clay fraction. 3) In the holistic model, there are no significant links between the LID system design and natural characteristics or LID system performance. It is recommended that different design standards and assessment indexing systems be tailored to local environment when constructing sponge city projects.

How to cite: Guo, Z., Zhang, X., Winston, R., Smith, J., Yang, Y., Tao, S., and Liu, H.: A holistic analysis of Chinese sponge city cases by region: Using PLS-SEM models to understand key factors impacting LID performance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2302, https://doi.org/10.5194/egusphere-egu24-2302, 2024.

    With the growing interest in utilizing Blue-green solutions to mitigate the negative impact of urbanization and climate change, and further enhance human health, it becomes essential to comprehensively understand the extent to which BGS influence human well-being through integrating various indicators. Building upon concepts within the existing framework of the Nature-Based solutions to health theory, this study aims to investigate the changes in heart rate among park users and establish connections between these changes and the benefits brought about by urban green spaces, as well as the potential of integrating wearables to quantify the impact of BGS on human health. The research was conducted at the demo site of the HEART project, the Pedion of Areos Park in Athens. The heart rate data of two participants engaged in walking activities within the park were recorded through wearable devices. By analyzing the associations between factors like the Normalized Difference Vegetation Index (NDVI), air pollutants, temperature with heart rate, as well as the complex interplay of various environmental indicators, this study reveals the positive impact of BGS on human health. The outcomes of quantitative statistical analysis indicate that temperature significantly influences heart rate, while the impact of air pollutants on heart rate is not clearly revealed. The result from spatial analysis further confirms a significant correlation between the increase in NDVI and the reduction in Land Surface Temperature (LST), particularly during the spring season. These research findings demonstrate that heart rate can serve as an effective health indicator to quantify the benefits of BGS. While the generalizability of study results might have limitations, it offers insights into the influence of urban green spaces on human health. In the future, with larger sample sizes, diversified datasets such as GeoHealth data with health status, age, and gender, and long-term observations, we can gain a more comprehensive understanding of these positive impacts, thus providing stronger scientific foundations for urban planning and design. 

How to cite: Huo, W., Temenos, T., Boskovic, S., and Maksimovic, C.: Integration of health indicators and quantification of benefits from BGS urban interventions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3300, https://doi.org/10.5194/egusphere-egu24-3300, 2024.

The activities of an animal – beavers - are increasingly recognised as a nature-based solution to hydrological extremes; dams and wetlands that beavers create attenuate flows downstream whilst delivering multiple benefits for the environment and for people. There can however also be challenges for people living alongside beavers. Q-Methodology is a technique for eliciting an understanding of human perspectives that exist within a context, enabling a rich understanding of human subjectivity within a context. We used Q-Methodology to elicit an understanding of perspectives that exist about beavers and their role in natural flood management among communities living downstream of three beaver sites in England, where Eurasian beavers (Castor fiber) are currently being reintroduced. Diverse perspectives that exhibited a range of value judgements were identified, including favourable viewpoints which valued multiple benefits beaver activities can provide, as well as less favourable viewpoints with some perceiving a reliance on beaver-led natural flood management to be less predictable and of higher risk than relying upon human-led interventions. In response to our findings, we support a catchment-based approach to beaver management so as to incorporate contextual perspectives in decision-making, and to enable dissemination of knowledge about beaver behaviours within communities. Further, we encourage future research into whether Beaver-Dam Analogues (in-stream structures that mimic beaver dams or their function) could be used as ‘starter dams’ to encourage beaver activities in optimal locations, as this may inspire confidence in beaver-led flood defence by working with the animal to develop a 'right dam in the right place' strategy.

How to cite: Auster, R., Barr, S., and Brazier, R.: Beavers and flood alleviation: Human perspectives from downstream communities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3463, https://doi.org/10.5194/egusphere-egu24-3463, 2024.

Nature-based solutions (NBSs) have been promoted as a holistic way to solve a variety of societal issues while benefiting biodiversity at the same time. To date, applications of NBS approaches that help ensure food security have yet been systematically reviewed. In this paper, we critically review the specific NBSs for food security, highlighting their limitations, to provide recommendations that promote their applications for improving global food security. Our systematic review of nearly 700 peer-reviewed articles indicated that many NBS approaches can be applied to enhance food security dimensions individually or together. However, there is a strong bias towards food availability and not enough research has been done to link NBSs with
improvements in food access and utilization. Over 80% of the reviewed papers were of short-term studies or without specific timeframes, and 25% offered no information on economic effectiveness of NBSs. Environmental benefits of NBSs were explicitly described in about 60% of these papers, and biodiversity enhancement was measured in only about 10%. We, therefore, recommend future applications of NBSs to safeguard food security be shifted to food access and utilization with careful consultation with local communities to address their specific context, using indicators that are easily measured and managed. Systematic monitoring regime and robust and diversified financial support system are also equally important in efforts to successfully implement NBSs. Moreover, environmental and societal benefits, especially water productivity and biodiversity, must be incorporated into the planning and design of NBSs.

How to cite: Ho, L., Nguyen, M., Babel, M. S., and Park, E.: Nature-based solutions for improving food security: A systematic globalreview, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3786, https://doi.org/10.5194/egusphere-egu24-3786, 2024.

Our landscapes and watercourses face intense pressures from climate extremes, land use change, declining biodiversity and increased demand for water resources. It is increasingly proposed that by working with natural processes, Nature-based Solutions (NbS) can increase resilience to these pressures, providing multiple environmental and societal benefits.

Beavers are the archetypal ecosystem engineers and keystone species, which can profoundly alter ecosystem structure and function, creating complex wetland environments (Brazier et al., 2021). Research has shown the return of the Eurasian beaver (Castor fiber) to European landscapes can provide multiple benefits including for biodiversity and water resource management (Puttock et al., 2021). However, beaver activity such as damming and tree-felling within our intensively managed and populated landscapes can also conflict with existing land use (Auster et al., 2019). Therefore, management and policy frameworks are required which mitigate conflicts and maximise the NbS benefits beavers can bring.

The Making Space for Water Programme (Barclay et al., 2023) will be introduced, which aims to support land managers to build a network of nature rich wetlands across South West England. This project led by Devon Wildlife Trust, in partnership with the University of Exeter and local landowners is the first of its kind in the UK, aiming to work with wild beavers to deliver natural solutions to address societal challenges.  Case studies will be presented discussing how geospatial mapping and modelling, stakeholder engagement and green finance approaches are being implemented to make catchments ‘beaver ready’, target financial support and enable NbS to deliver significant and lasting benefits. It is hoped that the approach adopted in this project alongside discussion of challenges and benefits can contribute towards progress in the mainstreaming of nature-led NbS approaches.

References

Auster, R. E., Puttock, A., & Brazier, R. (2019). Unravelling perceptions of Eurasian beaver reintroduction in Great Britain. Area, area.12576. https://doi.org/10.1111/area.12576

Barclay, H., Holden, M., Puttock, A., & Burgess, P. (2023) Making Space for Water: Investing in nature-based solutions with beavers. https://www.flipsnack.com/devonwildlifetrust/dwt-beaver-green-finance-programme/full-view.html

Brazier, R. E., Puttock, A., Graham, H. A., Auster, R. E., Davies, K. H. & Brown, C. M. . (2021). Beaver: Nature’s ecosystem engineers. WIREs Water. DOI:10.1002/wat2.1494

Puttock, A., Graham, H. A., Ashe, J., Luscombe, D. J. & Brazier, R. E. (2021). Beaver dams attenuate flow: A multi‐site study. Hydrological Processes, 35(2), e14017. DOI:10.1002/hyp.14017

How to cite: Puttock, A., Barclay, H., Holden, M., Burgess, P., and Brazier, R.: Making Space for Water: Investing in Nature-based Solutions with Beavers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4650, https://doi.org/10.5194/egusphere-egu24-4650, 2024.

The concentration of atmospheric carbon has overpassed 420ppm calling for urgent action to mitigate climate change and remain below the 1.5-degree warming agreed in the Paris climate agreement. The construction industry, with energy consumption included, is with about 40% a significant contributor to the global carbon emissions. Within concrete production, cement accounts for 90% of the emissions. Notably, cement production alone accounts for 8% of global carbon emissions.

Fly ash is amongst the most used of all Supplementary Cementitious Material (SCM). However, its availability is becoming an issue since many coal power plants are shutting down in Europe. Moreover, its environmental profile is questionable. Fly ash is a side product of a carbon intensive industry. Nonetheless, no environmental load has been allocated to it until now.

This study investigates how Volcanic Pozzolan from Iceland (VPI) in concrete compares to traditional concrete and VPI to fly ash, as well as the potential of reducing carbon emissions in concrete production by using VPI as SCM and substitute for cement.

To assess the environmental impacts of VPI and fly ash in cement production, we conducted a Life Cycle Assessment (LCA). For this purpose, we used the GaBi software and relied on primary data from the developers, Heidelberg Materials, and secondary data from the Ecoinvent database.

Our preliminary results reveal that the utilization of VPI as SCM yields an important reduction in carbon emissions compared to Ordinary Portland Cement (OPC) concrete. This notable decrease in carbon footprint positions VPI as a compelling alternative for sustainable concrete production. Two primary factors support this assertion: i) preliminary tests affirm the comparable properties of VPI concrete to OPC, and ii) the diminishing availability of fly ash in Europe necessitates alternative sources, often located at considerable distances, thereby escalating transportation-related emissions.

In conclusion, the integration of VPI emerges as a viable strategy to combat climate change and curtail the carbon footprint of the concrete and construction industry. This initiative aligns with global environmental objectives outlined in the Paris Agreement, United Nations Climate Change Conference, and the Nordic commitment to carbon neutrality by 2040. Embracing VPI as a sustainable alternative in concrete production reflects a positive stride towards achieving these critical environmental milestones.

How to cite: Costa, D., Heinonen, J., Finger, D., Bjarnadóttir, S., Ögmundarson, Ó., Wigum, B., Þorsteinsson, B., and Adolfsdóttir, H.: The potential of Volcanic Pozzolan from Iceland (VPI) in concrete production to reduce the carbon footprint, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4763, https://doi.org/10.5194/egusphere-egu24-4763, 2024.

Wetland systems are known for their capacity to transform and/or remove various pollutants (organics, nutrients, trace elements, etc.) via various physical, biological, and chemical processes. As wetlands provide a wide range of economic and ecological benefits, they stimulated the development of constructed wetlands (CW) to exploit this water purification capacity for wastewater treatment purposes under controlled conditions. Constructed wetland ecosystems have been used for the treatment of domestic, municipal and industrial wastewater effluents for many years.

CWs are nature-based solutions designed in such a way to mimic and enhance the functions of natural wetlands, but further to provide an added value to the known values and functions of natural wetlands, and a wider range of ecosystem services that include flood and stormwater control, habitat creation, reduced carbon footprint and biodiversity restoration. This is why CWs represent a key development in the field of ecological engineering.

The modern view of ecological engineering, as outlined by the International Ecological Engineering Society in their Manifesto, dictates that a circular approach should be adopted across the various engineering solutions, in this case in the water and wastewater sector. Adopting green technologies such as CW is the first crucial step towards circularity and overall reduced carbon and material footprint, which should further be integrated with interventions such as treated effluent valorization for irrigation of crops and plant biomass conversion to valuable organic materials.

This study will present different case studies of CW from around the world where this modern approach has already been applied in the field. Focus is given on different wastewater effluents to demonstrate the treatment capacity of this green technology, as well as on different facility scales (small and large) to showcase the feasibility of building such systems even at the largest scale and the large potential to upscale CW technology. The following CW case studies will be presented:

Keywords: constructed wetlands; wastewater treatment; ecological engineering; nature-based solutions; circularity; water reuse; organic waste; systems thinking; resilience; ecosystem services

How to cite: Stefanakis, A.: Ecological engineering and circular solutions: constructed wetland case studies for wastewater treatment and reuse, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6029, https://doi.org/10.5194/egusphere-egu24-6029, 2024.

The rapid population growth rate is associated with an increased number of residential buildings worldwide; thereby, the massive consumption of building materials causes negative environmental consequences such as the depletion of natural resources and rising non-renewable energy use. To address the environmental, societal, and economic challenges, using Nature-based Solutions (NbS) in residential building materials became essential and considered a catalyst tool for realizing sustainable development goals (SDGs) of the UN 2030 agenda. Consequently, using green building materials (GBM) based on NbS as a long-term strategy should be considered during the whole building life cycle for applying sustainability. This research aims to investigate the potential role of using NbS in residential building materials to achieve SDG and develop a framework for assessing and identifying the direct and indirect inner relationships that affect resource efficiency, cost-effectiveness, and building occupants' comfort level. The research attempts to answer how using NbS in residential building materials can contribute to achieving SDG. The eco-friendly approach was used based on a comprehensive literature review to identify the sustainability indicators for using the GBM. The system dynamics (SD) is also used for estimating and quantifying the selected materials through the building life span, starting from the early design stage until demolition and disposal to landfill. The causal loop diagram (CLD) was created based on the data collected from the residential building case study in New Capital Administrative in Egypt after applying the sustainability indicators, followed by critical analysis to identify the realization of the SDGs. The results showed the framework promotes the potential benefits of using NbS in residential building materials. GBM has significantly contributed to achieving several SDG goals and their targets. The study recommended that the selection of alternative materials and the occupant's comfort level deserve more attention from the early design stage and need more consideration.

Keywords, Green Building Materials, Nature-based Solutions, System Dynamic, Sustainable Development Goals, Egypt

How to cite: Marey, H., Kozma, G., and Szabó, G.: The Role of Using Natural-Based Solutions in Residential Building Materials for Achieving Sustainable Development Goals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6592, https://doi.org/10.5194/egusphere-egu24-6592, 2024.

Biochar is a sustainable carbonaceous solid material derived from biomass pyrolysis, which abides to circular economy principles in several ways that concern both its production and its several application fields. Biochar is produced by valorizing different organic waste biomass, such as agricultural waste, municipal solid waste, sewage sludge and industrial biowaste, to create a beneficial and valuable product that can then be used in many fields. Thus, biochar production serves perfectly the circularity paradigm as it renders a previously considered waste material to a valuable input material for a new production process. The grounds for the increasing use of and interest in biochars is their favourable physicochemical characteristics, such as the high carbon, macro- and micro- nutrient content, the high porosity and specific surface area, and the abundance of surface functional groups.

Biochar can be effectively used as soil amendment providing fertilizing properties to the applied soil that leads to higher crop production and increased crop nutrient content and quality. At the same time, it provides a stable source of carbon to the soil for several years after its application, contributing this way to CO₂ mitigation. Biochar can also be used as an adsorbent due to its carbonaceous porous structure to remediate polluted soil, water and wastewater from either organic or/and inorganic pollutants, even in low pollutant concentrations.

Τhis abstract will present a comprehensive range of studies on biochar production from different sources and its use in different sectors. One of the latest applications is its use as a substrate in Constructed Wetlands for sustainable wastewater treatment, in order to enhance the various pollutant removal/transformation processes. Three different research studies will be presented where biochar was produced from green waste (e.g., olive tree branches) and used as substrate in various Constructed Wetland pilot units that treat domestic wastewater, landfill leachate and olive mill wastewater as an ecological treatment technology.

Furthermore, an agronomic application of biochar as soil amendment in a pot experiment for the cultivation of lettuce will be shown. Finally, the environmental application of biochar produced from sewage sludge as adsorbent will be presented towards the decontamination of water and wastewater from organic emerging micro-contaminants.

How to cite: Regkouzas, P., Asimakoulas, I., Athanasiadou, E., Koukouraki, E., and Stefanakis, A.: The role of biochar in a circular economy: from agriculture to water and wastewater treatment applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6788, https://doi.org/10.5194/egusphere-egu24-6788, 2024.

BirdWatch, funded by the Horizon Europe Program, focuses on improving the state of biodiversity of the EU's agricultural landscape, in line with major policy targets of the EU Green Deal, the EU Biodiversity Strategy for 2030, and the Farm to Fork Strategy. A healthy agricutural ecosystem forms the necessary basis for the provision of nature-based solutions and, eventually, for the resilience of our society.

Leveraging Copernicus satellite data, the project assesses agricultural areas to identify their suitability for farmland birds and strategises ways to enhance ecological conditions. As indicator species, birds offer insights into overall biodiversity health, contributing to a broader understanding of ecosystem well-being.

The project employs species distribution modeling to link bird occurrence data with habitat requirements, establishing models that gauge habitat suitability and the likelihood of an area being suitable for specific bird species. Utilising remote sensing data, BirdWatch quantifies essential environmental descriptors such as structural variability, land cover type, crop type, mowing intensity and soil moisture. These parameters are then fed into the habitat models to assess landscape suitability.

Knowing the state of habitat suitability and the habitat requirements, BirdWatch identifies which of the agroecological schemes under the EU’s Common Agricultural Policy (CAP), have to be applied to improve the farmland conditions. The agri-environmental schemes are selected in such a way to ensure that they are not in conflict with any spatial or ecological requirements.

Here, BirdWatch uses spatial optimisation, taking into account both the ecological requirements and the economic and operational constraints of the farmers who need to implement the agri-environmental measures as part of their obligations under the CAP.

Benefiting from Copernicus program's high temporal resolution, BirdWatch evaluates the success of agri-environmental measures and makes adjustments as needed.

Upon project completion, the service will be accessible through a web-based GIS application in the project regions of Flanders, Germany, Lithuania, and South Tyrol.

How to cite: Frick, A., Scholz, N., Gey, S., Zurell, D., Wiedenroth, L., Kadunc, N. O., Vesel, N., Rosier, I., Hendrix, R., de Meyer, A., Sonnenschein, R., Tufail, B., Ventura, B., Orlickas, T., and Rimgaila, M.: BirdWatch - a Copernicus-based service for the improvement of habitat suitability of farmland birds in the EU, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7509, https://doi.org/10.5194/egusphere-egu24-7509, 2024.

Wastewater treatment generates a by-product material known as sewage sludge. In many countries, most of the produced sludge is disposed in landfills, following a linear management strategy that is based on mechanical and chemical methods for limited dewatering and daily transportation to landfills. This strategy is rather expensive and unsustainable and possesses several environmental risks such as groundwater pollution, insufficient sludge drying and stabilization, high carbon footprint etc. Ecological engineering concepts and technologies can provide a circular sludge management strategy that focuses on the utilization of this valuable by-product with the smallest possible environmental impact.

This work will present an ongoing large research study that investigates different technologies and methods towards transforming this organic by-product to a beneficial material with the minimum environmental impact. Specific tasks of the project are:

• A setup of 16 pilot-scale units of the sustainable technology of Sludge Treatment Wetlands for sewage sludge treatment. The pilot units have different operation and construction properties, such as planted/unplanted, presence of earthworms, different substrate thickness, different loading rates, in order to eventually result in a highly efficient and optimized design configuration.
• Composting of sewage sludge along with the reed biomass from the constructed wetlands
• Production of biochar using sewage sludge and reed biomass as raw materials

The experimental results of the first operational year of this project will be presented.

The studied circular model for sludge management will be evaluated regarding the reduction of greenhouse gas emissions due to the non-use of mechanical dewatering methods, avoidance of high energy and chemicals consumption, and cessation of daily transport and disposal in landfills. The various organic materials that are produced will be assessed based on their quality properties and will further be tested by application to tomato crops for the estimation of yield improvement. Ultimately, an assessment of the economic, technical, environmental and social parameters of all methods and material cycles and studied management scenarios, will be carried out in order to determine the optimal circular management strategy.

How to cite: Asimakoulas, I., Regouzas, P., Koukouraki, E., and Stefanakis, A.: Circular management of sewage sludge for the sustainable dewatering and reuse of biosolids: an experimental study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7697, https://doi.org/10.5194/egusphere-egu24-7697, 2024.

Raceway open systems are a highly promising, eco-friendly methodology for wastewater treatment. To assess how effectively nutrients and organic matter were removed from primary and secondary treated wastewater, two laboratory-scale open-raceway algal-bacteria ponds were used. The reactors were operated at organic loading rates (OLR) ranging from 29 to 95 and 9 to 38 g sCOD m³/d, for primary and secondary effluent, respectively. The hydraulic retention time (HRT) of both reactors dropped progressively from 5.5 to 2.2 d, and they thereafter ran at a HRT of 1.1 d. After 130 days, a high biomass concentration of around 2.2 g/ L was maintained with both substrates. Reactors were shown to be functional even at lower HRT levels by the quick removal of organic matter and nutrients. In less than 12 hours, the highly active biomass that was produced with both substrates resulted in the almost complete removal of organic matter and nutrients.
With its exceptional settling capabilities, the algal-bacteria biomass may settle in less than ten minutes. The algal-bacteria content of biomass was 18.3 to 16.5% for lipids, 72.5 to 72.6% for proteins, and 2.6 to 3.2% for carbohydrates. The findings of the present work show that syntrophic algal-bacteria biomass is effective for the high-rate treatment of municipal wastewater. The low operational cost as well as the potential nutrient recovery and biomass valorization make the algal-bacteria process a circular-green model for wastewater management .

How to cite: Biliani, S. and Manariotis, I.: Algal-bacteria raceway ponds for circular wastewater treatment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7812, https://doi.org/10.5194/egusphere-egu24-7812, 2024.

Over the past century, the nitrogen pollution problem has grown concomitantly with population growth, intensified agricultural practices, and a warming climate. In Europe, the presence of excess nitrogen in the environment has already exceeded safe planetary boundaries, posing a threat to Earth’s water supply and biodiversity.

While considerable efforts are now focused toward mitigating this problem through increased regulatory measures on wastewater treatment plants and implementation of better agricultural management practices, there is a growing interest in the use of wetlands as nature-based solutions (NBS) to improve water quality and, in particular, to reduce nitrogen loading to downstream water.

Despite these benefits, wetlands are among the most degraded ecosystem in Europe, having experienced significant shrinkage over the past centuries, now constituting only one-third of their 1700 extent. This decline is largely attributed to agricultural expansion on drained productive wetland soils, while also contributing to increased nitrogen pollution from excess use of fertilizers.

To address these issues, starting from nitrogen surplus data and current wetland extent at European scale we estimate with a physically-based model that current removal potential of wetlands is about 1113 ± 101 kt of N per year (~6.5% of total N surplus in European soil). The significance of wetlands in water quality remediation is underscored by the fact that this nitrogen would otherwise enter the river network and, subsequently, the sea. Given that the current riverine loads in EU watersheds amount to about 2730 kt N per year, the loss of current wetlands would increase this figure by over 40%, with detrimental consequences for the status of surface waters and the eutrophication of coastal areas.

We propose a set of restoration scenarios, along with the associated costs, for the restoration of wetlands that have been drained for agricultural purposes. Our analysis aligns with the objective of the Nature Restoration Law, requiring EU member states to implement effective restoration measures to cover at least 20% of the EU’s land and sea areas by 2030. We show that by restoring 2.6% of EU land (equivalent to 20% of historical wetlands), we could nearly double the current nitrogen uptake (2108 ± 187 kt of N per year), and significantly improve riverine water quality by reducing more than 30% of their loads to the sea. In addition, wetland restoration will offer a wide array of ecosystem co-benefits from flood prevention and carbon sequestration to provision of critical habitat for specialized flora and fauna.

How to cite: Bertassello, L., Basu, N., and Feyen, L.: Enhancing Nitrogen Removal in European River Basins: The Crucial Role of Wetland Conservation and Restoration as Nature-Based Solutions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11118, https://doi.org/10.5194/egusphere-egu24-11118, 2024.

The UN Decade on Ecosystem Restoration (2021-2030) was declared by the UN General Assembly driven by the global need to support and scale up efforts to prevent, halt and reverse the degradation of ecosystems worldwide. The Food and Agriculture Organization of the UN (FAO) and the UN Environment Programme (UNEP), as leaders of the Decade, are working together with other relevant stakeholders to achieve the Decade’s mission. To do so, focus is given to the development of capacities to empower professionals and institutions involved in the field of restoration to design, implement, monitor and sustain effective restoration initiatives. In the framework of the Best Practices Task Force (TF) of the Decade, partners have jointly developed a Capacity, Knowledge and Learning Action Plan, based on the findings of a global capacity needs assessment, a stocktake of knowledge products and capacity-development activities, and multiple targeted consultations. The plan identifies the gaps where knowledge products or capacity-development initiatives are required across different stakeholder groups, and provides terms of reference for capacity and knowledge development initiatives tailored for those different stakeholder groups. The TF has published the Standards of Practice to guide ecosystem restoration, providing key recommendations in an effort to facilitate the application of the principles for ecosystem restoration. In addition, the TF has created the Framework for the Dissemination of Good Restoration Practices to help practitioners share and consult information about restoration. This framework is in turn part of the UN Decade’s Framework for Ecosystem Restoration Monitoring (FERM), and allows for the collection and documentation of good practices. It also features a common search engine to connect and facilitate retrieving best practices from different relevant platforms, besides the FERM. These resources provide any restoration actor with an essential base for an effective planning, implementation and monitoring of global and local restoration efforts.

How to cite: Besacier, C., Gallo Granizo, C., and Romero Montoya, A.: Fostering forest and landscape restoration under the UN Decade on Ecosystem Restoration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11619, https://doi.org/10.5194/egusphere-egu24-11619, 2024.

Forests and landscapes are fundamentally interconnected, with geomorphic process being modulated by vegetation dynamics, which in turn is influenced by landscape form. Trees play a critical role in shaping landscapes by redistributing sediment across the Earth's surface via gradual processes including tree throw and root growth, and catastrophic processes such as landsliding and debris flows, where spatially variable root cohesion contributes to slope failure likelihood. Conversely, landscape morphology controls the availability of light, water and nutrients for trees and has been observed to dive significant variability in the structure and composition of forests at both local and regional scales. Until recently, our ability to disentangle these processes at broad spatial scales has been limited due to a lack of high resolution data on tree morphology. Advances in Terrestrial Laser Scanning and UAV-LiDAR systems now allow forest plots to be scanned rapidly, capturing the morphology of hundreds of trees alongside the terrain they grow on.

Working across a range of European forest ecosystems, representing a range of climates, we have constructed an unprecedented 3D dataset of European forest-landscape dynamics. From plot-level scans, individual trees are segmented from the digital forest and classified by species. State of the art structural metrics are then computed at an individual, species, and regional level across each distinct climate zone. This pan-European dataset is then coupled with high resolution topographic data, to explore the fundamental linkages between landscapes and vegetation.

How to cite: Grieve, S., Owen, H., Ruiz-Benito, P., and Lines, E.: Forest-landscape dynamics across a climate gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11821, https://doi.org/10.5194/egusphere-egu24-11821, 2024.

The natural capital and ecosystem services that we rely on have been severely impacted by changes to our ecological, biogeochemical and climate systems. This has been driven by our lifestyle choices, impacting our water, air and soil quality. Left unchecked, environmental degradation threatens to reverse the benefits created, exacerbating the decline of our critical natural capital resources. Among the many benefits we obtain from the natural environment, human health and wellbeing are among the most important, yet least understood. In Ireland, mental health conditions, including depression and anxiety impact up to 42% of the population. The costs of poor mental health to the economy are estimated to be €11 billion each year. Furthermore, the second leading cause of death in Ireland is circulatory disease, such as heart attack, or stroke. This Science Foundation Ireland funded project VNiC-Health (Valuing Natural Capital in Communities for Health) will focus on providing evidence from both a human health and wellbeing, and a quality natural environment point of view, helping to address two of the most critical challenges affecting society - the climate and environmental emergency, and our health crisis.

How to cite: O'Keeffe, J., Burke, J., Kaleta, B., Campbell, S., and O'Connell, C.: Valuing Natural Capital in Communities for Health, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12659, https://doi.org/10.5194/egusphere-egu24-12659, 2024.

Live Pole Drains (LPDs) are a plant-based drainage system used to drain natural slopes and prevent shallow gully erosion. LPDs are a Nature-based Solution built by placing a live fascine in a shallow ditch or gully along the slope direction, allowing moderate fluxes of surface runoff or seepage to infiltrate and high water fluxes to be conveyed along the fascine without further eroding the slope. Despite their practical implementation, the transient and long-term eco-hydrological behaviour of LPDs is not well understood. We aim to better understand the LPD’s water balance, the seasonal and life-span changes in hydrological behaviour, as well as the impact of an LPD on surface runoff water quality. To this end, we built and instrumented an artificial slope with full-scale LPDs in an open-air lab (OAL) at TUD. The design of the setup and the monitoring plan of the LPDs were developed in collaboration with Glasgow Caledonia University with insights from the construction and monitoring of three LPDs at different growth stages in their OAL on the east coast of Scotland. Herein, we present the design and possible research experiments that can be performed over the next 5 years, generating a data set to further develop and validate conceptual hydrological modelling of LPDs. We expect this long-term demonstrative setup to generate interest and facilitate a more comprehensive understanding of LPD functions, ultimately leading to the incorporation of LPD design and maintenance standards in engineering toolboxes for slope and gully stabilization.

How to cite: Cahill, L., van der Werf, J. A., Gonzalez-Ollauri, A., and Bogaard, T. A.: Long-term monitoring of eco-hydrological effects of Live Pole Drains in large open-air test facility at TUDelft campus, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13080, https://doi.org/10.5194/egusphere-egu24-13080, 2024.

Zebra mussels (Dreissena bugensis) and quagga mussels (Dreissena polymorpha) are invasive throughout much of the northern hemisphere. Whilst much attention has been paid to their role in altering aquatic systems via their filter feeding, little attention has been given to their role as geomorphic agents, or the relationships between geomorphology and their ecosystem engineering. We aimed to understand the controls and feedbacks between fluvial geomorphology and Dreissenid mussel invasion, utilising field, laboratory, and numerical modelling approaches. We found important consequences for both geomorphology and ecosystems, with mussel invasion significantly impacting annual sediment transport rates, and positively facilitating the invasion of further priority invasive species.

Quagga mussels attach to benthic sediments using byssal threads, which affects sediment stability and thereby broader river geomorphology. At an invaded gravel bed river, quagga mussels attached >500 g m^-2 of mineral sediments together. In ex situ flume experiments, this process increased critical shear stress by 40%. Numerical modelling of flow at the study river was used to upscale these stresses to estimate changes to sediment transport over a recorded five-year flow period, which indicated that typical densities of quagga mussels may reduce the occurrence of a geomorphically active flood event from Q₃₀ to Q₂, and reduce sediment transport by 74%. Thus, substantial alterations to bedload sediment transport may occur following quagga mussel invasion.

Dreissenid mussels are also ecosystem engineers, where their shells provide a unique stable habitat in fine-grained rivers. Field surveys found that mussel shells positively facilitate macroinvertebrate communities, but preferentially facilitate co-evolved, high-priority invasive amphipods. The construction of a spatial model of riverbed grainsize across England and Wales, combined with an analysis of Environment Agency nationwide presence/absence records, identified that ecosystem engineering by zebra mussels was particularly powerful in fine-grained river systems to other invasive taxa. Supporting mechanistic aquarium experiments indicated that the ecosystem engineering of zebra mussels may support the invasions of high-profile amphipod species into otherwise unfavourable habitats, which could not be invaded without mussel engineering. Channelisation and dredging, which simplify river channels, may benefit Dreissenid mussel ecosystem engineering and the facilitation of other invasive species. Instead, Nature-based Solutions could be employed to restore the geomorphic functioning of systems, which may improve resilience against high-priority invasive species.

How to cite: Sanders, C.: Geomorphic invaders: Geomorphic potential and landscape controls on the biogeomorphology and ecosystem engineering of Dreissenid mussels, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15884, https://doi.org/10.5194/egusphere-egu24-15884, 2024.

Jan De Nul Group has a long-standing presence in Ecuador, particularly since 2018, when a 25-year concession contract began for performing maintenance dredging for the Access Channel to the port of Guayaquil. This area is part of the Guayas river delta and is covered by mangrove forests that provide important ecosystem services. However, in the last few decades there has been significant loss of mangroves in the area, which intensifies coastal safety problems, as the land around the Guayas river delta becomes more exposed to floods and coastal erosion.

In response to this, the AquaForest innovation project was introduced in 2023. Dredged material from the Access Channel of Guayaquil will be reused for the first time in a circular and sustainable way to create a new mangrove habitat on a new intertidal flat created in the Guayas river delta, located 15km NE of Posorja. AquaForest will become a ‘Nature-based-Solutions’ (NbS) Living lab where important mangrove ecosystem services will be demonstrated and monitored such as protection against floods, biodiversity gain, carbon sequestration and socio-economic benefits for the local communities.

The AquaForest project concept is based on the development of “green-grey infrastructure”. This approach combines conventional engineering techniques for land reclamation with the circular reuse of dredged material to create mangroves through assisted afforestation. At the same time, the initial conditions will be created (e.g. sediment characteristics, hydraulic and hydrodynamic conditions) that are ideal for the growth of mangrove propagules, the proliferation of new accompanying tree seeds and the colonization process of associated biodiversity (micro and macro fauna), though suitable eco-engineering of the project site. Part of the project also focuses on the study of upscaling of this type of Nature-based-Solutions. As such, knowledge obtained from this pilot project regarding the implementation and monitoring of mangrove NbS will be employed in the upscaling of the AquaForest concept in future projects across the region and around the world, particularly in areas where mangrove forests serve as vital components of local ecosystems.

AquaForest demonstrates co-creation between private companies, public institutions, international organisations, local communities and citizens, NGOs, universities and researchers. The project is a collaboration between Jan De Nul Group, Mantis Consulting, HAEDES, Escuela Superior Politécnica del Litoral, Free University of Brussels, University of Antwerp, South Pole, and the Calisur Foundation. The project furthermore has the full support of the Ecuadorian Ministry of Environment, Water and Ecological Transition (MAATE) and all other important local stakeholders.

Acknowledgements: AquaForest is supported by the Government of Flanders (NL: “Departement Omgeving”) through the G-STIC Climate Action Programme 2022, and The International Union for Conservation of Nature (IUCN) through the ‘Blue Natural Capital Financing Facility’.

How to cite: Stratigaki, V., Evenepoel, J., Wille, M., Lemey, E., Stols, I., De Prins, D., Reyes Chejin, A. S., Peláez Ávila, J., Kimpe, M., Nieto Wigby, J., Herremans, B., Ibanez, M., De Sutter, R., Bohorquez, B., Temmerman, S., and Dahdouh-Guebas, F.: Nature-based-Solutions for restoring and developing new mangrove habitats through eco-engineering, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16062, https://doi.org/10.5194/egusphere-egu24-16062, 2024.

Coastal ecosystems such as oyster reefs, salt marshes and mangroves are widely recognised as nature-based solutions reducing coastal erosion. Oyster reefs maintain their own habitat and have the ability to grow at the rate of sea level rise, making them self-sustainable, flexible and cost-effective coastal erosion measures in the face of climate change. By attenuating waves and stabilising sediment as well as facilitating and protecting neighbouring ecosystems, they stimulate coastal resilience. However, effective employment of oyster reefs as a nature-based erosion control measure is not trivial and requires the integration of ecological and engineering parameters. Given the satisfaction of these eco-engineering parameters, recent work demonstrates that oyster reefs lead to a four-fold reduction in erosion in the protected area compared to a non-protected area across a decadal period. Despite this apparent effectiveness across a longer time period, it is still poorly understood how effective oyster reefs are in reducing erosion during individual storm events and how large their morphological footprint during these events is.

We present the findings of a series of detailed morphological field surveys of the Viane oyster reef in the Eastern Scheldt, the Netherlands, during which three storm events (Ciaran, Gerrit and Henk) were captured. These storms led locally to significant wave heights of 1.3-1.5 m, corresponding to the highest percentile of wave events recorded locally. Results show that storm Ciaran resulted in an transect-average erosion of 0.02-0.05 m for the unprotected areas, corresponding to the typical annual erosion for the intertidal flats of this area. In contrast, the reef-protected areas showed a greatly reduced erosion of maximum 0.02 m but typically 0.01 m. It is important to note that the erosion pattern as a result of this storm event is far from homogeneous: erosion is greatest immediately behind the reef (~first 50 m), then reduces up to 150 m behind the reef, followed by a zone of deposition (150-250 m behind the reef) and then transitions into another zone of erosion (250-450 m behind the reef). Complementary numerical modelling with XBeach will be used to obtain additional insights into the role of wave angle, wave period and tidal timing on the flow, sediment transport and morphological changes caused by the Viane reef structure during storm events.

How to cite: van de Lageweg, W., van Steen, T., Walles, B., and de Smit, J.: The effectiveness of oyster reefs as a nature-based erosion control measure under storm events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16355, https://doi.org/10.5194/egusphere-egu24-16355, 2024.

Vertical greenery (VG) provides mutliple ecosystem services and diverse forms of implementation. Benefits are linked to maintenance, irrigation, and appropriate planning. The focus of the Fabikli project was to apply these aspects to educational purposes in three highschools in Berlin. This case study delineates the planning, implementation, maintenance, and educational operation of the project.

Complications arose due to planning errors and the still pending building permit of the systems, demonstrating the cumbersome administrative barriers regarding VG. Three energy-efficient rainwater irrigation systems and and a supporting structure that can be harvested from the ground were developed and implemented. Maintenance of these systems is designed to be infrequent and accessible, with low-tech solutions ensuring easy repairs.

At the center of the educational offer were the multidimensional issues addressed by the implemented VG systems. Examples include urban heat stress, land and water use, and CO₂ sequestration. The school personal was directly involved in the participation process. Consequently, teachers incorporated the VG-topic creatively into their classes. Here we present the harvest of the VG as an exemplary illustrative showcase.

In addition, the project aimed at a multiplication and propagation of similar systems, which did occur, but with serious design flaws. This demonstrates the importance of appropriate planning, implementation, and continuous attendance, even for low-tech solutions.

In conclusion, schools offer an influential societal overlap between generations and functions such as teachers, parents, or administration. VG can convey several key aspects of environmental education about the ecology with cities.

How to cite: Kluge, B. and Dahm, Y.: Climate adaptation through educational vertical greenery in high schools: key lessons from the city of Berlin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16707, https://doi.org/10.5194/egusphere-egu24-16707, 2024.

Conventional agricultural practices often lead to increased soil compaction, a decline in soil organic matter (SOM) and an associated decrease in structural porosity, compromising the water holding capacity and resilience of agricultural soils to hydrological extremes. Regenerative agriculture practices, with their focus on building healthy soil ecosystems, hold promises for enhancing agricultural resilience to extreme weather events like floods and droughts. These practices, such as reduced tillage, reduced trafficking and stocking density, cover cropping, and afforestation, can improve soil organic matter content, reduce compaction, enhance soil structure, and promote microbial activity, leading to increased soil porosity, water infiltration, and retention. However, due to the slow response of soils to changes in agricultural management, a critical research gap exists in the timely quantification of the potential effectiveness of these practices in mitigating flood and drought risks. Although undoubtedly robust and informative, long-term monitoring of soil properties before and after a management intervention may take decadal timescales to reveal any significant impacts.
We have therefore adopted an exploratory approach to investigate the merits of back-analysing existing long-term soil moisture datasets to reveal any changes in inferred soil porosity due to changes in land use and/or management. The following UKCEH long-term datasets, which include soil moisture information, have been considered: Neutron Probe Soil Moisture Database (~50 years range), UK Greenhouse Gases Flux Network (last 15+ years), and COSMOS-UK TDT probe data (last 10 years). In addition, we have land cover information from UKCEH Land Cover Maps from 1990 onwards. For UK conditions, it is anticipated that an annual maximum soil moisture content, representing saturated conditions, is likely to be attained during most winter seasons (excluding any ‘dry’ winters, excluded based on rainfall data). It is then possible to estimate soil porosity in any particular year by equating it to the maximum soil moisture content, in effect using this as a proxy measurement with due regard for potential air entrapment effects. Any identified long-term changes in soil porosity obtained through trend, wavelet, and before-after-control-impact analysis might then be linked to changes in land use and/or management. Land cover changes may be identified using Land Cover Map data and local site knowledge, the latter of which will also provide insights into changes in land management. COSMOS-UK TDT data is particularly interesting in terms of land management impacts as, when installed, the instrumentation at each site was enclosed by a newly erected fence. The resultant compound therefore excluded stock and vehicle trafficking and initiated a change in land use from generally arable or improved grassland to rough grassland. It will therefore be valuable to understand if the proposed exploratory analysis approach can reveal any significant changes in soil porosity over time due to this intervention. Likely challenges to be discussed include disentangling any long-term changes in maximum soil moisture due to changes in soil porosity from background changes in climate. We will also share lessons learned and provide recommendations for future work on the back-analysis of long-term soil moisture datasets.

How to cite: Sah, N., Blake, J., Bell, V., Evans, J., Morrison, R., and Dussaillant, A.: Exploratory analysis of the long(er) term dynamics of Nature-based Solutions: the case of agricultural soil properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17900, https://doi.org/10.5194/egusphere-egu24-17900, 2024.

Global warming has lead concerns about more frequent high intensity rainfall events and increasing river floods. Changes in the river hydrodynamics affect the biological communities which are controlled by the interplay between physical-chemical and hydraulic processes. Thus, there is increasing interest in identifying the impact of the hydrodynamic stresses, also determined by climate change, on the aquatic environment and, consequently, on the interactions between flow and organisms (Lopez and Vaughn, 2021). To this aim, it is fundamental to use remote sensors to constantly monitor the responses of animals to environmental changes. Among these sensors, bio-indicators have been increasingly used to monitor water quality conditions. Some species, called as “ecosystem engineers”, are especially important in studying the effects of climate changes in rivers (Butler and Sawyer, 2012). The present study considers freshwater mussels which meet the criteria to be considered as typical “ecosystem engineers” and can be considered as sensitive biosensors of environmental disturbance (among others Gerhardt et al. 2006). Monitoring freshwater mussels’ opening and closing valves activities (i.e., valvometric technique) over time has been used to evaluate the behavior of the bivalves in reaction to their environmental exposure. The application of the valvometric technique is not recent and has been mainly applied to analyze the impact of chemical stressors on freshwater mussels. Recent experimental results obtained by the research group of the present work (Modesto et al., 2023; Termini et al., 2023), in sand-bed laboratory flumes with different FMs’ populations, have suggested that the mussels’ behavioural response could be also used as a tool for an early warning system of flow variations in rivers, also in the presence of sediment transport. The present work reports the results both of an experimental investigation conducted in a laboratory flume to analyze the influence of the substrate composition on the freshwater mussels’ response and of an in-situ test conducted in a selected reach of the Paglia river (Italy) to verify the FMs’ response in non-controlled environment. In both cases the FMs’ valvometry data were collected in real-time by using Hall sensors technology. The FMs’ behavioural response was examined in terms of valves’ opening/closure frequency and amplitude. The obtained results have confirmed that FMs’ behavioural response can be used as BEWS for identifying the impacts of hydrodynamic changes in rivers.

References

Butler DR, Sawyer CF, 2012. Introduction to the special issue: zoogeomorphology and ecosystem engineering. Geomorphology 157–158.

Gerhardt A, Ingram MK, Kang IJ, Ulitzur S 2006. In situ on-line toxicity biomonitoring in water: recent developments. Environmental Toxicology and Chemistry 25: 2263–2271.

Lopez J. W., Vaughn C.C., 2021. A review and evaluation of the effects of hydrodynamic variables on freshwater mussel communities. Freshwater Biology 66 (9): 1665-1679.

Modesto, V. et al. 2023. Mussel behaviour as a tool to measure the impact of hydrodynamic stressors, Hydrobiologia, 850, 807–820.

Termini, D. et al. 2023. Identification of hydrodynamic changes in rivers by means of freshwater mussels’ behavioural response: an experimental investigation, Ecohydrology, e2544.

How to cite: Termini, D., Benistati, N., Ashkan Pilbala, A. P., Modesto, V., Riccardi, N., Fraccarollo, L., Piccolroaz, S., Manca, D., and Moramarco, T.: Freshwater mussels’ valve movement response as early-warning system of river’s ecosystem conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18207, https://doi.org/10.5194/egusphere-egu24-18207, 2024.

Connectivity is a crucial property of the riverine landscape. Reduction of connectivity, i.e. habitat fragmentation and isolation effects, impacting ecological functions and biotic communities, is one of the most critical threats to river-floodplain systems. Using a graph theoretical approach for analyzing possible transport pathways in the system (directed, undirected, overland, seepage), we could show that essential ecological functions related to sediment composition and quality, hydrochemical conditions, and macrophyte coverage can be predicted and importance of waterbodies in the network and their main connectivity deficits can be identified. In a second step we are now integrating biotic communities in the predictive framework. Dependent on dispersal model and habitat preferences the different taxonomic groups show clear pattern i.e. drifting invertebrate organisms are highly driven on directed transport whereas fish as active swimmers are more dependent on connectivity in the waterbody network or organism with terrestrial or flying dispersal (amphibia or flying insects) are dependent on overland connectivity. Further they interact with the ecological functions in the system. Using a temporal dataset based on eDNA (environmental DNA) we can further show that ecosystem conditions and distributions of biotic communities are dependent on different transport/movement pathways changing with hydrological conditions (flood to low flow conditions). The dynamic graph theoretic approach can, therefore, be used as an essential tool for prioritizing water bodies for nature-based solutions.

How to cite: Funk, A., Baldan, D., Meulenbroek, P., Pont, D., Recinos Brizuela, S., Bondar-Kunze, E., and Hein, T.: Connectivity as a driver of biodiversity and functioning in riverine landscapes: A dynamic, graph theoretic approach., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19044, https://doi.org/10.5194/egusphere-egu24-19044, 2024.

Most islands host an endemic biota, i.e., present nowhere else on Earth like it is the case, for instance, of Madagascar. It has been shown that different populations of lemurs, endemic to the island, are mostly distributed along the watersheds surrounding the central plateau of Madagascar, creating a so-called micro-endemism, while the populations living on the central high-elevated watersheds are not showing this micro-endemism. Here we wish to address the question whether there exists a correlation between the evolution of the landforms (i.e., the morphology of the island) of Madagascar and the hybrid distribution of lemur populations? More broadly, how does the tectono-geomorphic evolution of an island influence the flourishing of micro-biodiversity?

To answer these questions in a quantitative manner, we combined a Landscape Evolution Model based on the Stream Power Law and taking into account Flexural Isostasy, with a Speciation Model. We first developed a morphometric index to differentiate between Π-islands with a central plateau surrounded by smaller basins, like Madagascar, from conical Λ-islands, like Sri Lanka. We then predicted patterns of biodiversity as a function of the index value and its time evolution. We show that the tectono-geomorphic evolution influences patterns of biodiversity and evaluate the influence of varying the values for model parameters, in particular the ones characterising dispersal and mutation. We finally used phylogenetic observations to constrain some of these parameters.

How to cite: Lemaire, A., Braun, J., and Acevedo-Trejos, E.: Influence of Island Morphology on Micro-Endemic Biodiversity Distribution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19170, https://doi.org/10.5194/egusphere-egu24-19170, 2024.

The presence of burrowing animals is a recognizable characteristic in almost all types of landscapes and climates. Independent of their size, their activity of mounding and digging plays a significant role in landscape evolution, to the point of being addressed as ecosystem engineers. For example, while tunnels facilitate water infiltration, mounds slow down surface runoff and make soil available for erosion. Several models have included animal activity as a bioturbation process, and many studies have quantified the impact of animals’ presence on soil properties. However, how to best include burrowing animals’ role in other soil hydro-physical processes in hydrological, landscape evolution, or soil erosion models is still unclear. Indeed, the significant heterogeneity of animals’ distribution and their impact at different spatio-temporal scales complicates their inclusion into models. Therefore, this study aims to explore numerical methods (equations, coefficients, ratios) used to quantify the impact of burrowing animals on soil hydro-physical processes. Furthermore, it explores how these methods can be integrated with the most common equations implemented in hydrological, landscape evolution, or soil erosion models to calculate those processes. We focused on surface runoff, soil lateral transport, soil excavation, soil mixing, water infiltration and subsurface preferential flow. Peer-reviewed studies about burrowing animals’ impact on soil hydro-physical processes were collected. Of those articles, we reviewed studies where numerical methods were used to quantify or discriminate the role of the animals. The articles were classified according to the processes measured, the spatio-temporal scale, whether the animal was vertebrate or invertebrate and smaller or bigger than 2.5 cm.

As a first result, the main processes quantified are soil lateral transport, water infiltration and soil mixing. Most of the studies were conducted with field or laboratory experiments on a yearly scale. Because of this, most equations collected were empirical and used to quantify single processes for a specific environment. Rates were the primary means of quantification for runoff or soil lateral transport, and coefficients for soil mixing. Infiltration was quantified as change in soil moisture or as rate. Overall, hydraulic properties were mainly calculated in relation to the presence/absence of earthworms or insects, while mammals and vertebrates were primarily linked to soil physical properties and soil transport. We can argue that, to better incorporate animals’ influence on soil hydro-physical processes, a more comprehensive investigation of their role in soil hydraulic properties is fundamental. However, this might not be sufficient when considering large spatio-temporal scales (centuries, catchments). For this, the development of an ad hoc faunal-hydro-physical module can be used to explore the impact of animal bioturbation on processes at different scales.

How to cite: Loreggian, M., Baartman, J., and Larsen, A.: Quantification of burrowing animals’ impact on landscapes: a review of numerical methods., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19856, https://doi.org/10.5194/egusphere-egu24-19856, 2024.

Forest restoration faces persistent challenges for its financial viability due to high land opportunity costs and insufficient financial returns from restored areas, such as through payments for ecosystem services and timber production. A potential financial pathway is to develop non-timber forest products with bioeconomic potential. Here, we explore the bioeconomic potential of native tree species growing in different types of new wooded lands in Atlantic forests. First, we established 25 30 𝚡 30 m plots in natural regeneration, degraded forest remnants, and actively managed areas (eucalyptus monoculture and active restoration) in the Paraíba Valley, southeastern Brazil, where we sampled all woody individuals with dbh ≥ 5 cm, totaling 284 native tree species. Then, we conducted a literature review and patent survey on the biotechnological potential of the species sampled. Based on this review and survey, we calculated the proportion of sampled species with patents and assessed the species used and general characteristics of patents registered among prominent companies in the market. We found 168 (70%) species with a biotechnological potential based on the presence/absence of articles reporting uses for medicine, cosmetics, food, and other market segments, such as bioinsecticides, bio fertilization, construction, and manufacturing. In the sampled areas, species offer varied potential for use, with higher potential in spontaneous environments. Araucaria angustifolia was the most extensively studied species, with 246 research papers, followed by Euterpe edulis (205), Baccharis dracunculifolia (188), Dodonaea viscosa (170), Cedrela odorata (158), Copaifera langsdorffii (139) and Hymenaea courbaril (132). We found patents worldwide, distributed across more than 20 countries, for the sampled species. The medicinal use of leaf chemicals accounts for the largest use in our survey. Despite these numbers, we found that less than 5% of the investigated articles reported evaluations of final products, while most provided results from in vitro, in vivo, or chemical analytics descriptions. Most patents registered by companies are related to exotic and non-tree species, many associated with existing commodity chains, reinforcing the need to integrate bioeconomy and forest restoration agendas better.

How to cite: Krainovic, P., Paulo Romanelli, J., Helena Porcari Simões, L., Rodrigues Souza, L., Brower, R., Flávia Boeni, A., G. Massi, K., A. P. Toledo, C., R. Rodrigues, R., C. Souza, V., B. Chaves, R., de-Miguel8, S., and H. S. Brancalion, P.: Bioeconomy gaps and opportunities in restored Atlantic forests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20606, https://doi.org/10.5194/egusphere-egu24-20606, 2024.

This study presents the preliminary results of the ongoing research project “Re.Nature Cities”, in which  the ability of street trees to act as an effective measure against increased urban air temperatures is evaluated via experimental and simulation means. In the existing literature, numerous studies highlight that the addition of street trees inside the canyons of urban areas may result in a significant reduction of the peak ambient summer Tair, having also a prominent effect on outdoor thermal comfort regulation. Yet, street trees also impact urban ventilation as they act as barriers, disturbing the wind flow and affecting buildings’ energy needs and thermal comfort; the positive effect of wind sheltering during the cold winter period, can be thus significantly counterbalanced during the warmer periods of the year. The existing evidence reveals that the green elements’ implementation in the built environment without holistically accounting for all the vegetation-air-buildings interactions, can even exacerbate human discomfort and deteriorate indoor natural ventilation.

Based on the above, this study evaluates the mitigation potential of a tree type that is commonly encountered in Greek cities – the citrus- since it has low irrigation needs and high drought tolerance. An integrated experimental campaign, employing wind tunnel measurements, albedo and Leaf Area Index/Leaf Area Density (LAI/LAD) measurements is conducted so as to define of the aerodynamic, thermal and foliage characteristics of real trees.  Wind tunnel measurements of total drag are carried out in a wind tunnel section of 3.5m width and 2.5m height, while LAI measurements are conducted using a plant canopy analyzer, with the LAD of each layer (1 m/layer) then calculated from LAI by empirical equations. The obtained values are then used as input parameters in the vegetation model of the ENVI-met microclimate model, which is employed for the evaluation of the thermal environment of typical building blocks in Greece, considering different planting patterns and vegetation coverage scenarios.

The experimental database of foliage, thermal and aerodynamic characteristics of common urban tree species, along with the detailed microclimatic simulations of typical urban districts provide a valuable tool for decision-making regarding the optimal vegetation coverage and the planting pattern for urban areas.

How to cite: Tsoka, S., Pappa, V., Markos, N., and Bouris, D.: Assessing the effect of citrus plant on the improvement of the outdoor thermal environment using wind tunnel and ground-based Leaf Area Index measurements, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20879, https://doi.org/10.5194/egusphere-egu24-20879, 2024.

Cyanobacterial bloom induced by water eutrophication is one of the most serious ecological problems in freshwater lakes. Water diversion, transferring external freshwater into lakes, is proved to be the eco-hydraulic engineering measure rapidly relieving cyanobacterial blooms in eutrophic lakes. To explore the response of phytoplankton community to the changed aquatic habitat influenced by water diversion, we constructed the microcosm experiment modeling water diversion from Yangtze River to Lake Taihu in the laboratory, with one control group and three flow discharges groups of external freshwater from Wangyu River diversion channel during the summer water diversion period. Each modeling microcosm ecosystem had a volume of 5 L and was studied for a period of 20 days (10 days for the water diversion period and 10 days for the stop period). The results showed that the responses of physicochemical parameters in lake microcosms were sensitive, reflecting by the variations in contents of aquatic dissolved oxygen, total nitrogen, total phosphorus and dissolved silicate positively correlated with the flow discharges. During the period of water diversion, the cell abundances of Cyanophyta in all treat groups decreased significantly, while the abundances of Bacillariophyta increased, especially in the group with the highest flow discharge. The diversity and dominant species in phyla of Cyanophyta and Bacillariophyta were changed by water diversion and evidently in the highest flow discharge group. On the 20th day of the stop period, the relative proportion of Microcystis spp. recovered, and Pseudanabaena spp. became one of dominant cyanobacterial species in treat groups, which was related to the dominance of Pseudanabaena spp. in the external river water. The redundancy analysis between aquatic physicochemical parameters and phytoplankton communities revealed that variations in contents of aquatic dissolved oxygen, total nitrogen and dissolved silicate were the dominant environmental factors influencing lacustrine phytoplankton community in addition to the allochthonous inputs from external freshwater. However, the recovery of Microcystis spp. during the stop period of water diversion demonstrated that water diversion from Yangtze River to Lake Taihu has no sustainable effect on changing the dominance of Microcystis spp. in lakes in short time, although the diversity and phytoplankton community composition shifted during water diversion.

How to cite: Dai, J., Wu, X., and Wu, S.: Resilience of lacustrine phytoplankton community to the short-term river-to-lake water diversion, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21127, https://doi.org/10.5194/egusphere-egu24-21127, 2024.

During rockfall events, the seismic waves are generated in response to the time-varying normal and tangential forces between the Earth and colliding and sliding mass. These forces carry information about the nature of the generative seismic source; hence, the source dynamics can be estimated. Several studies have used forward modeling to determine the amplitude and duration of these forces and, implicitly, the source process that could generate the observed seismic waves. Through running multiple forward models, the force history inversion involves adjusting the force amplitude and duration to minimize the misfit between the proposed source model, convoluted with the force-impulse Green’s functions, and the observations. In the Bayesian framework, the normal likelihood function is traditionally used to measure the misfit between the observed and predicted waveforms with respect to amplitude. However, the normal likelihood function is insensitive to the potential misalignment of the waveforms in time. Moreover, the relevant parameter space often exhibits multiple local minima, which may lead to a convergence to a minimum that does not present the global optimum. Optimal transport distances-driven exponential likelihoods were recently proposed as alternatives thanks to their ability to capture the time structure of the signals. We employed a Metropolis-Hastings sampling strategy in the probabilistic framework to reconstruct the 2012 Palisades rockfall seismic source using two implementations of the Wasserstein distance-based exponential likelihood function. The first implementation transforms between density functions, which are always positive and integrate to one. Therefore, it requires the transformation of the signals into probability density functions, which is done here via a modified graph-space transform scheme. The second method is applied directly to the signals. We evaluated the robustness of the two implementations of the Wasserstein distance-based exponential likelihood function in simulating the source characteristics with respect to the normal likelihood. Preliminary results show that contrary to the expectations, using optimal transport distances-driven exponential likelihoods leads to negligible improvement in the fit to the observed waveform.

How to cite: Ursu, R., Naylor, M., Tang, H., and Turowski, J. M.: Probabilistic optimal transport-driven inversion of the 2012 Palisades rockfall seismic source, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-480, https://doi.org/10.5194/egusphere-egu24-480, 2024.

Shallow soft sedimentary layers overlaying harder bedrock are known to amplify ground motion generated by earthquakes. Such an amplification occurs when seismic waves travel from high impedance (density times wave speed) to low impedance layers. Large impedance contrasts can lead to substantially larger earthquake damages. As the impedance contrast determines the amplification factor, variations in shallow shear-wave speed contribute directly to changes in site amplification.

Seasonal temperature fluctuations have been shown to induce shear-wave speed variations and, hence, affect site amplification factors. This naturally leads to the question: is the strength of earthquake damage season dependent? In this study we model by how much seasonal temperature variations affect site amplification. The site-specific physical properties determine whether site amplification is more pronounced during summer or winter. For parameters from the Groningen region of the Netherlands, affected by the gas extraction induced seismicity, we expect in the summer a relative increase in amplification of 8% with respect to the amplification factor in the winter.

How to cite: Fokker, E., Ruigrok, E., and Trampert, J.: Do earthquakes cause more damage in the summer?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1972, https://doi.org/10.5194/egusphere-egu24-1972, 2024.

Machine learning can improve the accuracy of detecting mass movements in seismic signals and extend early warning times. However, we lack a profound understanding of the limitations of different machine learning methods and the most effective seismic features especially for the identifcation of debris flows. This contribution explores the importance of seismic features with Random Forest and XGBoost models. We find that a widely used approach based on more than seventy seismic features, including waveform, spectrum, spectrogram, and network metrics features, suffers from redundant input information. Our results show that six seismic features are sufficient to perform binary debris flow classification with equivalent or even better results., e.g., the Random Forest and XGBoost models achieve improvements over the benchmark of 0.09% and 1.10%, respectively, when validated on the ILL12 station. Considering models that aim to capture patterns in sequential data rather than information in the current time window, using the Long Short-Term Memory algorithm does not improve the binary classification performance over Random Forest and XGBoost models. However, in the early warning context, the Long Short-Term Memory model performs better and more consistently detects the initiation of debris flows. Our proposed framework simplifies seismic signal-driven early warning for debris flows and provides a proper workflow that can be used for detecting also other mass movements.

How to cite: Zhou, Q., turowski, J., Tang, H., Hibert, C., Chmiel, M., Walter, F., and Dietze, M.: Enhancing debris flow warning through seismic feature selection and machine learning model comparison, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3399, https://doi.org/10.5194/egusphere-egu24-3399, 2024.

Sermeq Kujalleq in Kangia, also known as Jakobshavn Isbræ, a major outlet glacier of the Greenland Ice Sheet, exhibits a flow speed higher than 30 m/day near the terminus. Basal sliding, iceberg calving, and subglacial hydraulics play pivotal roles in ice flow dynamics of this outlet glacier, and understanding these processes is crucial for predicting the impact of outlet glaciers on the Earth system in a changing climate.

 Seismic and geophysical field campaigns were conducted in 2021, 2022 and 2023 in the region of Sermeq Kujalleq in Kangia. The project has the aim to monitor the dynamic behavior of such a fast-flowing outlet glacier and its interaction with the surrounding shear margins. Shallow borehole seismic sensors and self-sufficient seismic boxes were deployed in multiple arrays on the fast-moving ice stream and its margin. The sensors capture seismic sources and monitor subglacial conditions and spatiotemporal variabilities throughout the ice mass. An on-rock broadband seismometer near the terminus records iceberg calving activity ideally complementing observations of a Terrestrial Radar Interferometer operating simultaneously.

 Here we report on first results of a seismic analysis that provides insights into details of ice dynamic variations of Sermeq Kujalleq. Power spectrograms of the 2023 upstream arrays feature a 4-day tremor-like signal between 2.5 and 6 Hz. This phenomenon was not observed for other calving events and was missing in the 2022 record. Beamforming techniques are employed to constrain the source location of this tremor as well as other seismic events. Potentially this multi-day tremor signal corresponds to the ice stream response to a major calving event. Additionally, beamforming and spectral analysis provide insights into hydraulic cycles of the glacier, such as widespread diurnal water drainage and the activity of moulins. By comparing these seismic observations with ice flow speed and satellite images we aim at understanding the details of short-term perturbations to ice flow, which may influence larger-scale ice stream dynamics.

How to cite: van Ginkel, J., Nap, A., Wehrlé, A., Walter, F., and Lüthi, M.: Capturing the short-term dynamics of outlet glaciers:  insights from seismic monitoring on Sermeq Kujalleq in Kangia, Greenland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3861, https://doi.org/10.5194/egusphere-egu24-3861, 2024.

Bedload export from Alpine glaciers by rivers is a geomorphological process of increasing interest given the high retreat rates of temperate ice masses in the context of global warming. Access and measurement difficulties make it very poorly known and contradictory hypotheses exist about how it might respond to receding glaciers. In subglacial channels, bedload transport is a key mechanism for evacuating one of the products of glacial erosion. It likely constrains glacial erosion rates as removal of the products of erosion is needed so as to yield fresh bedrock for further erosion. Environmental seismology may be a valuable tool in understanding rates of subglacial bedload export.
Previous studies have considered subglacial bedload export in glacial forefields using seismic sensors and tracked particles moving underneath the ice sheet. We are taking former studies forward and extend the monitoring of bedload export detecting coarse grain impacts using seismometers right at the glacial terminus. The project aims to determine diurnal as well as seasonal sediment export quantities and compare results among different field sites.
We studied subglacial bedload export for the Otemma and Arolla glacier in Valais, Switzerland in the summer of 2023 by installing two seismic stations (PE-6/B geophones) close to each glacier terminus throughout the melt season. These four-month records of seismic signals were processed using fluvial inversion algorithms of the eseis package implemented in R. The algorithm is refined with wave propagation- and ground properties determined through active seismic experiments as well as measured grain size distributions from field sampling. We are able to separate turbulent water noise and bedload noise in the seismic signal and estimate water stage as well as bedload transport rates. Results are validated by comparing the water stage estimates to measurements from a discharge gauging station. Over a full season, we compare the behaviour of the two different glaciers regarding sediment export taking into account their size, orientation, elevation and other factors. We relate the detected bedload export events to meteorological conditions and shifts in seasonal melt processes from snow melt to ice melt.
The results of this study help to get a clearer picture of diurnal as well as seasonal patterns of bedload export from glaciers, impacting downstream riverbed erosion and deposition in the light of increasingly rapid glacier melt. These geomorphological processes are of interest for different infrastructural facilities such as hydropower plants.

How to cite: Wolf, E., Dietze, M., and Lane, S.: Quantifying snout marginal bedload export from alpine glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5306, https://doi.org/10.5194/egusphere-egu24-5306, 2024.

We report the discovery of an unprecedented, monochromatic low-frequency seismic source arising from the fjords of North-East Greenland. Following a landslide and tsunami event in Dickson fjord on 16 September 2023, the seismic waves were detected by broad-band seismometers worldwide. Here we focus on a detailed analysis of the long-period seismic signal, while a reconstruction of the dynamics of the landslide is presented by Svennevig et al. in session NH3.5. 

Both frequency and phase velocity of the waves are consistent with fundamental mode Rayleigh- and Love-waves. However, the decay rate of these waves is much slower than predicted for freely propagating surface waves so that we infer a long-lasting and slowly decaying source process. Although the 16 September 2023 event was by far the largest, analysis of historical seismic data has revealed five other previously undetected events, all with a fundamental frequency between 10.85 and 11.02 mHz. The signal of the largest two events initially decayed with a quality factor, Q close to Q=500, which increased to Q=3000 within the first 10 hours and could thus be detected for up to nine days. The smaller four events had a slow decay-rate (Q>1000) for their entire duration. In comparison, the global average attenuation of Rayleigh waves at these frequencies is Q=117 for PREM, thus precluding a single, impulsive source for these signals.

Gleaning archives of optical and SAR satellite images reveals that at least four out of six events could be associated with landslides in Dickson fjord, the two others remain unresolved. However, such rapid transient events cannot explain the long duration of the radiated seismic waves. Our modelling of the largest event shows that a transversal seiche in Dickson fjord, excited by a landslide induced tsunami, can account for both the monochromatic low frequency signal as well as its seismic signal amplitude and radiation pattern. However, the seiche modelling results in Q values lower than 250 and hence the seiche needs to be continuously driven for the entire duration of the observed seismic signal. Thus, a full understanding of the source process that produces the monochromatic signal remains enigmatic.

How to cite: Koelemeijer, P., Widmer-Schnidrig, R., Svennevig, K., Hicks, S., Forbriger, T., Lecocq, T., Mangeney, A., Hibert, C., Korsgaard, N., Lucas, A., Satriano, C., Anthony, R., Mordret, A., Schippkus, S., Rysgaard, S., Boone, W., Gibbons, S., Cook, K., Glimsdal, S., and Løvholt, F. and the VLPGreenland team: Global observations of an up to 9 day long, recurring, monochromatic seismic source near 10.9 mHz associated with tsunamigenic landslides in a Northeast Greenland fjord, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5821, https://doi.org/10.5194/egusphere-egu24-5821, 2024.

Raindrop size distribution (DSD) is a key factor to derive reliable rainfall estimates. It is highly related to a number of integral rainfall variables, such as rain intensity (R), rain water content (W) and radar echo (Z) and thus can contribute to a range of hydrological and meteorological applications, such as rainfall-induced landslide warnings and radar rainfall calibration. Disdrometers are commonly used to measure DSDc. Well-known disdrometer sensors include JWD, Parsivel and 2DVD . These sensors may have their own strengths and weaknesses, but their costs are all much higher than that of widely-deployed catching gauges (e.g. tipping bucket and weighing gauges). This makes it infeasible to have a widespread, or dense, DSD monitoring network. To address this issue, our ultimate goal is to develop a lightweight and low-cost disdrometer with descent accuracy.

In this work, we have prototyped a disdrometer with a piezoelectric cantilever. It is not new to use piezoelectric materials as rain sensors because of its low cost and low maintenance. It is however not trivial to ‘calibrate’ this type of sensors, and various calibration methods have been proposed in the literature. However, whereas most of these sensors associate received signal with rainfall properties directly (via statistical or machine learning approaches), we propose to formulate the drop sensing process as a ‘mechanical’ problem. More specifically, we first form a physical model that can well simulate the signal response of continuous excitation force on a piezoelectric cantilever based on an existing theoretical model. We then analytically derive the inverse function of the model which can obtain the excitation force directly from the measured signals. The derived force-time signal is found to linearly associate with DSD and can also be used for other purposes including kinetic energy analysis.

In spite of the sound underlying theory, the real-world signal is far from perfect, containing a considerable amount of noise. Additionally, as our physical model requires conducting differentiation and second-order differentiation, to which the impact of noise is even destructive. Although we have made efforts to improve the quality of signal from the source, it does not fully solve the problem because the physical model is highly sensitive to signal gradients. To effectively deduce the impact of noise, we then introduced various signal ‘noise’ models, which were reported to well resemble the behavior of real-world signal noises, to train a machine learning (ML) model, such that the actual excitation force function can be derived from various weather conditions.

To verify the proposed sensor and signal processing model, we have set up lab experiments using an in-house device with micropumps and high-voltage raindrop detachment devices to control the required size, drop location, and timing of the drops. Preliminary results from a given range of drop sizes have shown the potential of the proposed sensor and ML-based signal processing model to well derive drop sizes from our experimental device. We plan on further testing our sensor outdoor and compare the measurements with those collected from a co-located Parseval2 disdrometer.

How to cite: Wei, C.-L. and Wang, L.-P.: Low-cost raindrop sizing with piezoelectric sensor: A mechanical approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5947, https://doi.org/10.5194/egusphere-egu24-5947, 2024.

Cryoseismology, which records ice-induced seismic activity, is emerging as a powerful tool for studying the grounding zone - a critical spatio-temporal area where outlet glaciers grounded on the continent starts floating and interacting with the ocean underneath. The SEIS-ADELICE project supported by the French Polar Institute (IPEV) aims to characterise the dynamics of the Astrolabe glacier in Terre Adélie (East Antarctica), from its grounded part to its terminus in the ocean. Over the past 3 years, we deployed broad-band seismometers both at the grounding zone and on stable ice around the glacier, along with ocean bottom seismometers (OBS) close to the glacier terminus. In January 2023, the recording system was complemented by a dense array of 50 seismic nodes over the grounding zone. This allowed us to cover spatial scales from metres to several kilometres, providing a high-resolution observation of tidal forcing on the floating tongue and its repercussions on the glacier behaviour. The seismic records contain a wide range of signals, including icequakes, accepted to result from the brittle deformation of the ice. Although the seismic patterns at the different stations show clear modulation of icequakes by tidal cycles, their phasing with the tide depends on the location of the sensors, whether they are grounded or floating and on their distance from the active part of the glacier. This highlights the importance of the network typology and its proximity to the grounding line when characterising icequake occurrence patterns. Local icequakes detected at the grounding line exhibit a consistent occurrence during both rising and falling tides, with the peak activity observed during high tide. Source location analysis reveals that events are distributed across both the grounding line and the lateral shear zones of the glacier which are under strong stress from the ice-ocean interactions during tides.

How to cite: Le Bris, T., Barruol, G., Gimbert, F., Le Meur, E., and Zigone, D.: High resolution observations of tide induced icequake activity at the Astrolabe glacier grounding zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6218, https://doi.org/10.5194/egusphere-egu24-6218, 2024.

The Lower St. Lawrence Seaway (LSLS) is part of a major marine shipping corridor in eastern Canada, and also an essential feeding ground for fin whales and blue whales. Understanding the whale migration and habitat usage in the LSLS is critical for informing conservation policies that minimize noise pollution and risk of collision to the whale populations. In this study we utilize continuous recordings of six broadband seismometers located on the north and south shores of the St. Lawrence River to characterize the frequency range, recurrence interval and duration of fin and blue whale calls. We further use the whale call detections to quantify their spatial and temporal variations along the LSLS between February 2020 and January 2022, with the caveat that the detection range at these land stations is probably limited to a few kilometers due to energy loss along the seismic wave travel paths through multiple interfaces. We identified higher whale call detection rates at stations near the northwest of St. Lawrence Gulf than the upstream Estuary, suggesting possible influences of ocean currents and ice conditions. Whale calls are detected year around, with majority in the fall/winter months (September to February), implying seasonal and annual variations that may be influenced by climate change. We are currently analyzing recordings from a temporary deployment of 48 nodal seismometers, at 10-km average spacing, along the shorelines of the LSLS between September-October 2023, to further quantify the spatial patterns of whale calls and identify possible linkages to coastal bathymetry, ocean currents and preferential diets for the baleen whales.

How to cite: Liu, Y., Goblot, E., and Plourde, A.: Tracking baleen whale calls in the Lower St. Lawrence Seaway, Canada, using land seismometers  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6613, https://doi.org/10.5194/egusphere-egu24-6613, 2024.

The EarthScope Transportable Array (TA) in Alaska has been a unique seismic network since about 2014 because most stations are equipped with environmental sensors to record pressure, temperature, and wind (speed and direction). We will summarize some physical insights of near-surface properties in Alaska that can be gained from the combined analysis of seismic and environmental sensors. We also point out a possible effect of the thick sea ice on the climate in the North Slope region that faces the polar ocean.

First, the combined analysis of seismic data and pressure data allows us to separate two distinct types of seismic noise; one is the ordinary seismic noise, consisting of propagating body and surface waves, and the other is the deformation caused by the local pressure loading. This loading effect is observed at many stations when surface pressure becomes high. It can be confirmed based on two pieces of evidence; one from high coherence between seismic and pressure data and the other from the phase difference between pressure and vertical seismic displacement. By selecting data from a high-pressure range, we can apply the compliance method, similar to the compliance method applied to ocean bottom observations (e.g., Webb and Crawford, 1998). We will show a map of shallow rigidity variations for the depth range of 50-100m.

Second, the combined analysis of temperature and seismic noise allows us to identify the major effects caused by near-surface melting, primarily in the permafrost area. Some stations show a thousand-fold increase of horizontal noise in summer at 0.01-0.03 Hz in comparison to the frozen state. This anomalous horizontal noise can be seen at low frequency (< 0.1 Hz) and is undoubtedly related to tilt effects as its amplitude increases towards lower frequency.

Third, seasonal variation in horizontal noise shows a rapid increase in summer due to melting but the way the noise level returns to the frozen (low-noise) state varies from station to station. For most stations, this return occurs well after the surface temperature becomes negative in September or October. But some stations require time until March of next year to return to the low noise level. These data suggest that the melt layer remains at depth for a long time even after temperature drops below freezing, perhaps developing a sandwiched molten layer between the developing ice from the surface and the underlying permafrost ice.

How to cite: Tanimoto, T.: New Perspectives on the Shallow Environment in Alaska from co-located seismic, pressure, temperature, and wind sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6637, https://doi.org/10.5194/egusphere-egu24-6637, 2024.

Excessive and sustained rainfall can trigger regional floods with a large propagation range. Their non-linear onset, rapid evolution and massive impact make prediction, mitigation and posteriour anatomy efforts difficult.

The atmospheric low “Petar” that struck Europe in early August 2023 was one drastic example of such flood triggering rain events. It was able to gain abundant moisture and heat over an exceptionally warm Mediterranean Sea, before it moved to continental Europe, crossing Slovenia, Austria, and Germany. It caused severe flooding as a result of locally more than 350 mm rain within less than two days. We focus on Slovenian examples, where the event was perceived the most devastating natural hazard in the last decades.

Here, we follow a seismic approach to study the spatially contrasting effects of the rain signal from available FDSN data (SL network). We study the time variant spectral signatures of reaches in steep mountain, graded upland and wide basin landscapes across northern Slovenia and exemplarily invert the seismic data for key flood parameters: water level and debris flux, and propagation velocity. We discuss the detection range of existing earthquake seismometer networks and the potential to improve those with respect to flood quantification. Our analysis highlights the compound effects of channel geometry, event magnitude and network density for flood detection and signature consistency.

How to cite: Dietze, M., Jemec Auflič, M., Petan, S., and Bezak, N.: August 2023 Slovenian flood anatomy from national seismometer network data analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7490, https://doi.org/10.5194/egusphere-egu24-7490, 2024.

The Greenland ice sheet, a critical component of the global climate system, has played a substantial role in rising sea level, marked by a fourfold increase in mass loss due to iceberg calving between 1992-2000 and 2000-2011. Through the quantification of the spatio-temporal changes in Greenland’s ice mass loss resulting from iceberg calving, we gain a deeper understanding of the impacts of climate change.

The mass loss related to calving icebergs can be estimated by combining mechanical simulation of iceberg calving and inversion of seismic data. Seismic signals are generated by the time-varying force produced during iceberg calving on marine-terminating glacier termini. These events, known as glacial earthquakes, are recorded by the Greenland Ice Sheet Monitoring Network at tens of kilometres from the source.

However, differentiating these signals from tectonic events, anthropogenic noise, and other natural noise is challenging due to their complex frequency content (1-100s), multi-phase waveforms and low amplitude. To overcome this difficulty, we use a detection algorithm based on the Short-Time Average over Long-Time Average (STA/LTA) method and combine it with machine learning (Random Forests). By training the machine learning algorithm on seismic event catalogues containing more than 400 earthquakes and glacial earthquakes each, our approach is apt for identifying glacial earthquakes. Applying this methodology to continuous data offers the possibility to uncover smaller and previously undetected events. As a result, we present a comprehensive catalogue spanning several years and discuss its relevance and reliability. The generated catalogue allows us to develop new methods to better understand the spatio-temporal evolution of the ice-calving activity in the region. Among these, we will initially focus on locating and inverting the force of the largest events, providing a basis for testing new machine learning approaches for the characterisation of the source. This includes extracting properties like the iceberg volume and shape from both large and smaller events, ultimately advancing our understanding of Greenland's ice mass loss dynamics.

How to cite: Wetter, S., Hibert, C., Mangeney, A., and Stutzmann, E.: Constructing a New Catalogue of Greenland's Iceberg Calving Events through Seismic Data Analysis and Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7576, https://doi.org/10.5194/egusphere-egu24-7576, 2024.

Icequakes are closely associated with glacier movement and rupture, and their temporal and spatial distribution patterns can portray the dynamics of glaciers. In this study, we used the seismic data recorded by 34 short-period Smartsolo seismometers deployed in Dålk Glacier, East Antarctica for about 60 days to detect and locate icequakes. The array was deployed at the edge of the Dålk Glacier and across the grounding line previously generated by satellite observations. The recorded data were strongly affected by Antarctica storms and we selected two days with little wind noise for preliminary analysis. Using time-frequency analysis and particle motion, we found that the seismic events are either dominated by body waves or surface waves, which likely correspond to deep icequakes or near-surface crevasse icequakes. Since the propagation of surface waves is easier to analyze and possible detections of crevasse icequakes are more likely to be verified from satellite images, we chose to focus on surface wave signals in this preliminary analysis. We first filtered records to 5-20 Hz and manually examined records with clear surface wave arrivals. We then produced templates using these events to scan through our records. We successfully identified 89 events within the two-day period. Lastly, these signals were located using a grid-search approach for their latitudes and longitudes, together with an average group velocity for each event. Nearly half of the incidents were concentrated on the edges of rock outcrops, which suggests they were generated by the relative movement between the glacier and outcrops. The other half of the events was found in the eastern region, where a large number of surface crevasses were observed on satellite imagery. In addition, the optimal velocity from the grid search is ~2.8 km/s for events from the North and West, while the optimal velocity for events from the East is ~1.8 km/s. The difference in wave velocity suggests the existence of a boundary between rock and ice at a depth of about 100-150m within or near our seismometer array. By analyzing the amplitude variations of incidents in different directions recorded at various stations, we observed that this boundary is within our array and its location and geometry can be estimated. Compared to the grounding line predicted from satellite observations, our result shows that the boundary is offset to the East by ~100 m. The reason for this discrepancy will be further discussed in the meeting.

How to cite: Zhao, S., Cao, Z., Gu, Y., Lv, C., Ma, Z., Hao, T., Qiao, G., Wang, B., and Li, R.: Icequake source location using seismic data in Dålk Glacier, East Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8208, https://doi.org/10.5194/egusphere-egu24-8208, 2024.

Monitoring underground water reservoirs is challenging due to limited spatial and temporal observations. This study presents an innovative approach utilizing supervised deep learning (DL), specifically a multilayer perceptron (MLP), and continuous passive-Multichannel Analysis of Surface Waves (passive-MASW) for constructing 2D water table height maps. The study site, geologically well-constrained, features two 20-meter-deep piezometers and a permanent 2D geophone array capturing train-induced surface waves. For each point of the 2D array, dispersion curves (DCs), displaying Rayleigh-wave phase velocities (V_R) across a frequency range of 5 to 50 Hz, have been computed each day between December 2022 and September 2023. In the present study, these DCs are sampled in wavelengths ranging from 4.5 to 10.5 m in order to focus the monitoring on the expected water table depths. All V_R data around one of the two piezometers is used to train the MLP model. Water table heights are then predicted across the entire geophone array, generating daily 2D piezometric maps. Model's performance is tested through cross-validation and comparisons with water table data at the second piezometer. Model’s efficiency is quantified with the root-mean-square error (RMSE) and the coefficient of determination (R²). A R² is estimated above 80 % for data surrounding the training piezometer and above 55 % for data surrounding the test piezometer. Additionally, the RMSE is impressively low at 0.03 m at both piezometers. Results showcase the effectiveness of DL in generating predictions of water table heights from passive-MASW data. This research contributes to advancing our understanding of subsurface hydrological dynamics, providing a valuable tool for water resource management and environmental monitoring. The ability to predict 2D piezometric maps from a single piezometer is particularly noteworthy, offering a practical and efficient solution for monitoring water table variations across broader spatial extents.

How to cite: Cunha Teixeira, J., Bodet, L., Rivière, A., Dangeard, M., Hallier, A., Gesret, A., Dhemaied, A., and Boisson Gaboriau, J.: Water table height maps prediction from passive surface-wave dispersion using deep learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8304, https://doi.org/10.5194/egusphere-egu24-8304, 2024.

Current climatic warming is causing accelerated melt of the Greenland Ice Sheet. Whilst the changing hydrological response is well known, the sediment export as well as the geomorphic changes in the proglacial area remain uncertain.  

Here we present records of sediment transport from melt seasons 2022 and 2023 in the proglacial area of Leverett glacier, a land terminating glacier outlet on the Western part of the Greenland Ice Sheet. The proglacial area here is very well denifed by a waterfall cutting through bedrock functioning as terminal gauge, which allows for the installation of hydrological stations. These hydrological gauging stations, containing turbidity and pressure sensors, allow for estimation of discharge and suspended sediment concentrations over the melt season. Variations in bedload transport can be analysed using the sesimic data obtained from the geophones placed on the river bank close to the hydrological gauging stations. To convert the recorded seismic data into bedload flux, a Fluvial Inversion Model is used, which is calibrated using active seismics surveys and the water stage data from the hydrological gauging stations.

The dataset allows us to investigate the relationships between bedload, suspended sediment, and water discharge from the Leverett glacier as well as sediment transport and deposition in the proglacial area. We observe several spring events in the first half of July, where suspended sediment concentration and water discharge increase simultaneously at the start of the melt season. During the first half of August, we observe a clear dilution signal, where increase in water discharge coincides with a decrease in suspended sediment concentration From insights about the relationship between water and sediment discharge from the ice sheet, we can speculate about the sediment export response to increased water discharge from the Ice Sheet.

How to cite: Gevers, M., Lane, S. N., Miesen, F., Mancini, D., Jenkin, M., Bouscary, C., Perchanok, F., and Delaney, I.: Seasonal variations in sediment transport from ice sheet terminus through a proglacial forefield. A case study from Leverett glacier, Western Kalaallit Nunaat (Greenland). , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9067, https://doi.org/10.5194/egusphere-egu24-9067, 2024.

Groundwater storage monitoring is now one of the most promising application of seismic interferometry techniques. In steep mountain environments, where drilling wells is particularly challenging, the use of seismic stations to retrieve relative seismic velocity changes could fundamentally advance our understanding of groundwater dynamics. However, very few studies have looked at seismic velocity variations at the scale of a single steep topography unit. Here, we estimate velocity variations from six stations covering a distance of 3.5 km on a single mountain ridge in the county of Hualien, Taiwan. One station was placed at the top of a ridge (900m elevation), two at the mid-slope of the topography and two others at the bottom (200m elevation), near the river banks. The aim is twofold: Determining how homogenous these velocity changes are and understanding the possible impact of topography on groundwater variations in a mountainous setting. Results from auto-correlations and cross-correlations are compared with meteorological data and other geophysical analysis. We identify the average hydrological dynamics of the ridge unit and connect the residual velocity changes to local site characteristics and upstream weather conditions.

How to cite: Illien, L., Kuehn, J., Andermann, C., and Hovius, N.: Monitoring groundwater dynamics in a mountain ridge using seismic interferometry: Influence of topography, local subsurface structure and meteorological conditions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9608, https://doi.org/10.5194/egusphere-egu24-9608, 2024.

In traditional glacier flow laws and consequently glacier models, a widely used assumption is that the ice behaves as a non-Newtonian viscous fluid that slides either across hard bedrock or via deforming subglacial till. Elastic effects and brittle deformation within the ice are often neglected for simplicity, as even ubiquitous surface crevasses are difficult to capture in numerical schemes. While there is ample seismological evidence that stick-slip motion plays a significant role in basal sliding of both alpine and polar glaciers, similar evidence is lacking for brittle deformation within the ice mass itself. Instead, it is commonly assumed that the ice moves and deforms in a purely viscous or ductile manner, which may not be an accurate representation of reality.

Here, we present observations of high-frequency (>50Hz) signals of intermediate-depth seismic sources occurring along the fast ice-stream of Sermeq Kujalleq in Kangia (Jakobshavn Isbræ), Greenland’s fastest flowing outlet glacier. The waveform characteristics of these events closely resemble the known characteristics of waveforms associated with basal stick-slip events, making them easily distinguishable from the more prevalent icequake signals generated by surface crevasse opening and propagation. However, differences in P and S wave arrival times as well as probabilistic source locations show that these events occur at ~170-400 m depth, whereas at those locations the glacier has a total depth of approximately 2000 m. Hence, these events cannot be caused by stick-slip motion at the base of the glacier, but must originate from englacial dislocations such as e.g., thrust faulting. Hundreds of these englacial icequakes are observed at several seismic arrays that were temporarily deployed in 2022 and 2023 along the fast ice-stream of Sermeq Kujalleq. Using waveform clustering and source mechanism analysis, we discuss the role of these events in ice dynamics and in particular englacial deformation.

How to cite: Nap, A., Walter, F., Lüthi, M. P., Wehrlé, A., van Ginkel, J., Kneib-Walter, A., and Rousseau, H.: Intermediate-depth icequakes at Greenland’s fastest outlet glacier: evidence for englacial thrust faulting?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9822, https://doi.org/10.5194/egusphere-egu24-9822, 2024.

One major challenge in cryoseismology is that signals of interest are often buried within the high noise level emitted by a multitude of environmental processes. Specifically, basal sources such as stick-slip events often stay unnoticed due to long travel paths to surface sensors and accompanied wave attenuation. Yet, stick-slip events play a crucial role in understanding glacier sliding and therefore, it is of great interest to investigate their spatio-temporal evolution, across the entire glacier from its ablation to its accumulation zone.
Distributed Acoustic Sensing (DAS) is a technology for measuring strain rate by using common fiber-optic cables in combination with an interrogation unit. This technology enables us to acquire seismic data over an entire glacier with great spatial and temporal resolution. To unmask stick-slip events, new techniques are required that effectively and efficiently denoise large cryoseismological DAS data sets. 
Here, we propose an autoencoder, a type of deep neural network, which is able to separate the incoherent environmental noise from the temporally and spatially coherent signals of interest (e.g., stick-slip events or crevasse formations). We trained the autoencoder in order to denoise a DAS data set acquired on Rhonegletscher, Switzerland, in July 2020. Due to the highly active and dynamic cryospheric environment as well as non-ideal cable-ground coupling the collected DAS data are characterized by a low signal to noise ratio compared to classical point sensors.
Several models were trained on a variety of data subsets, differing in recording positions (ablation or accumulation zone), event types (stick-slip event or surface event) and the quantity of training events. We compare and discuss the denoising capabilities of these models with several metrics, such as inter-channel coherence, similarity between seismometer and DAS recordings, and visual assessment. This evaluation is conducted while considering different data types in a qualitative and quantitative manner. All models show an increase in inter-channel coherence of the seismic records after denoising. Further, all models uncover previously undetected stick-slip events, whereby models trained on manually picked training data perform better than models trained on randomly picked training data. We believe that the application of our models can improve the understanding of basal stick-slip information in cryoseismological DAS datasets, potentially uncovering previously hidden information.

How to cite: Zitt, J., Paitz, P., Walter, F., and Umlauft, J.: Uncovering Stick-Slip Events: Denoising Cryoseismological Distributed Acoustic Sensing Data with an Autoencoder, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10147, https://doi.org/10.5194/egusphere-egu24-10147, 2024.

In March 2023 the annual winter school SKIENCE (www.skience.de) was held in the Bavaria alps, south-east of Munich. The topic was environmental seismology with a focus on seismic monitoring using ambient seismic noise. The winter school had strong practical training aspects. Prior to the meeting 12 5Hz nodes (SmartSolo) were deployed in the valley near Bayrischzell with the goal to explore local structure and site effects using interferometric methods. During the midweek free afternoon the 12 SmartSolo nodes were installed on both sides of a slalom run with several gates through which participants of the winterschool skied one after each other. First inspection of the data showed that clear signals of the skiers could be identified. Here, we report on attempts to use the seismic data records to recover the tracks of the skiers as moving seismic sources. Questions associated with this experiment are at which points in the tracks seismic energy is generated, where exactly the incoming signals propagate and with what velocities, and how well the source locations can be backprojected. A simple theoretical model is used to develop the inversion tools to recover the moving sources.   

How to cite: Igel, H., Brass, S., Lindner, F., Van Noten, K., de Plaen, R., Wassermann, J., Bernauer, F., and Lecocq, T.: The seismic signature of skiing, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10347, https://doi.org/10.5194/egusphere-egu24-10347, 2024.

How to cite: Seydoux, L., Nanni, U., Goulet, L., Pauze, T., and Köhler, A.: Observing ice-bed weakening on a fast flowing glacier with seismic noise interferometry and unsupevised clustering., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10380, https://doi.org/10.5194/egusphere-egu24-10380, 2024.

Cryoseismological records consist of numerous signals generated by various sources within or surrounding glacial ice, including icequakes, water flow, avalanches, rockfalls, wind, or precipitation. This results in a notably high noise level within the data, posing a significant challenge in detecting and distinguishing individual seismic events and sources.

Our research employs Deep Embedded Clustering (DEC) to address this challenge, focusing on the analysis of a Distributed Acoustic Sensing (DAS) dataset acquired on Rhonegletscher (Switzerland) in 2020.

To visualize and efficiently streamline the DEC processing of this substantial volume of data, we reorganize the numerous continuous DAS channels as a 3D data cube featuring the three dimensions: time, space, and frequency. The DEC approach involves first transforming high-dimensional seismic data into a more manageable lower-dimensional latent space using an autoencoder. This transformation is vital in emphasizing the essential characteristics of the data, thereby enabling more effective clustering. Subsequently, the DEC algorithm autonomously categorizes these seismic signals into distinct clusters based on their unique spatio-temporal characteristics, without the prerequisite of manual annotation.

The primary aim of this approach is to utilize DEC for the effective mapping of clearly defined spatio-temporal clusters within cryoseismological records. This approach is geared towards achieving a more nuanced understanding of the various sources contributing to these records and their complex dynamics. By successfully segregating these clusters, the aim is to reveal new insights into the complex processes and interactions in glacial environments.

Both the DAS data and the clustering results can be explored interactively using the data cube viewer Lexcube. Come find us at the poster stand!

How to cite: Peters, J., Roth, F., and Umaluft, J.: Deep Embedded Clustering of a Cryo-Data-Cube, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10525, https://doi.org/10.5194/egusphere-egu24-10525, 2024.

Can we use environmental data to predict changes in surface displacement fields? Do severe weather events alter the near-surface geomechanical properties? The seasonal variations in GPS time series and crustal seismic velocities have been frequently observed at different study areas. Such variation has been tied closely to the cyclic hydrological loads [e.g., Costain et al., 1987; Heki, 2003; Roth et al., 1992], which its association with tectonic deformation remains debated. Using the 15 years meteorological, geodetic, and seismic data recorded in southern Taiwan (near Chaozhou fault where the background seismicity level is low), we aim to explore the possibility of predicting surface displacement and vibration using climatic variables (time series of temperature, precipitation, and wind velocity) and groundwater levels. Here the Support Vector Regression (SVR) model is developed for the prediction of the GNSS and seismic signals, while 15-yr datasets are divided into groups of 75%  and 25% datasets for model calibration and testing. When the predicted surface displacement is compared with the real data, the R-square values reach 95%, indicating the applicability of SVR model on long-term surface deformation prediction. In the future, long-term prediction model will be conducted to target several extreme weather events in Taiwan.

How to cite: Hi, C. E., Chen, K. H., Peng, W., Huang, W.-R., Chen, H. H., Wang, K. C., and Ching, K. E.: Support vector regression-based model for the prediction of surface displacement and vibration using meteorological data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11086, https://doi.org/10.5194/egusphere-egu24-11086, 2024.

Changing climate, especially the increase in frequency and intensity of extreme events such as heat waves and droughts, poses a significant challenge to the biosphere, threatening biodiversity overall and specifically exacerbating tree mortality. Countermeasures and management actions often prove insufficient due to delayed visual indicators of tree stress. 

Real-time monitoring of physiological and structural changes in tree characteristics and related abiotic parameters, such as sap flow, leaf angle, or soil moisture, plays a crucial role in tracking the trees’ overall vitality. However, conventional monitoring approaches are often expensive, require high maintenance and are therefore not feasible on a larger spatio-temporal scale.     

In a groundbreaking approach, we propose to measure the seismic oscillation generated by tree sway under specific weather conditions, potentially reflecting tree vitality. Specifically, oscillations are related to material properties of leaves, branches, and trunks, which change when they become dry. Seismic measurements offer scalability and low maintenance, making them viable for extensive spatio-temporal coverage. Through integrated observations from dense seismic arrays, direct tree trait measurements, and meteorological parameters collected at the research arboretum (ARBOfun) during autumn 2023, we successfully isolated the seismic fingerprint of tree sway.

However, the unique nature of this novel data introduces challenges, for example noise from human and animal activities, allowing for only time series snapshots. To overcome these challenges, we explored various time series and frequency related analysis methods to separate the tree signal from other influences.

How to cite: Roth, J., Mora, K., Al-Halbouni, D., Richter, R., Kattenborn, T., Wieneke, S. J., Bastos, A., Weigelt, A., Wirth, C., and Umlauft, J.: How trees sway and what it tells us about their overall vitality, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11562, https://doi.org/10.5194/egusphere-egu24-11562, 2024.

GLOFs, glacier lake outburst floods – or by their local type name jökulhlaups – sometimes travel and propagate subglacially. Usually, these subglacial floods can be observed only indirectly using records of the related glacier’s surface deformation derived from GNSS and InSAR techniques. However, these floods can also be monitored by the seismic signals they generate: Flood noise by turbulent water or carried sediments, ice quakes, and others.

At Iceland’s Vatnajökull glacier, floods from the Skaftá cauldrons travel more than 40km below the ice before feeding into the Skaftá river. To study the propagation and the physics of the jökulhlaups, temporal seismic arrays were installed close to the glacier terminus, i.e., west and southwest of Vatnajökull between 2014 and 2016. To locate the generated tremor along the flood propagation path, we used two seismic methods: frequency-wavenumber-analysis (fk-analysis) and match field processing (MFP).

In previous works, we were able to track the subglacial propagation of the flood tremors seismically for four GLOF events occurring between 2014 and 2016. For the discharge-highest flood occuring in October 2015 we were also able to identify seismic signals related to the rising water level downstream at rapids outside of the glacier.

These findings can be directly related to hydrometric and GNSS observations, measured outside and on the glacier respectively. We find that the tremor can be related to the vertical deformation of the glacier after the flood front’s passing: an important insight allowing to reconstruct the glacier’s deformation seismically.

Our results highlight the potential of seismic methods for monitoring subglacial floods, especially in combination with GNSS and hydrometric observations. We emphasize that such multi-method approaches can improve the understanding and quantification of flood characteristics such as their volume, origin, propagation and timing which are critical to effectively provide early warning of subglacial floods.

How to cite: Dietrich, T., Eibl, E. P. S., Pálsson, F., Magnússon, E., Schwanghart, W., Ohrnberger, M., Heimann, S., Lindner, F., and Roessner, S.: Array seismologic insights into Skaftá jökulhlaups (GLOFs), Iceland, 2014-2016., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12879, https://doi.org/10.5194/egusphere-egu24-12879, 2024.

The field of fluvial seismology has undergone significant advances over the past decade. The development of dedicated physical theories and their applications in various contexts have allowed separating the respective contributions of turbulent flow and bedload transport, such that physical parameters like flow depth and sediment flux may be inferred from seismic observations. However, the quantitative link between signal characteristics (amplitude, frequency) and the underlying physics yet involves simplified considerations that do not necessarily apply to more complex situations, such as for example under rough flow conditions or during extreme floods.

In this talk I will present results from laboratory experiments that we designed specifically in order to quantify the seismic signature of flow turbulence and intense bedload transport under a range of conditions using force sensors coupled to the river bed. On one hand, I will show that existing theory regarding turbulent flow properly captures the main characteristics of the seismic source, but that additional dependencies on flow conditions and particle-wake development need to be included for more accurate predictions. On the other hand, I will show that existing theory regarding bedload transport fails at capturing the main characteristics of the seismic source under intense bedload transport conditions associated with complex changes in internal flow dynamics. In this case the seismic source appears to be a decreased function of solid concentration, as opposed to an increased function such as considered in current theories, which we suggest is due to grain impacts being agitation-controlled rather than bed-roughness controlled. Finally, I will discuss possible ways towards building more generic theories of ground motion induced by sediment transport.  

How to cite: Gimbert, F., Bakker, M., Piantini, M., Recking, A., and Lamb, M.: Assessing the seismic signature of turbulent flow and intense bedload transport from designed laboratory experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13007, https://doi.org/10.5194/egusphere-egu24-13007, 2024.

The early detection of slope instability and the monitoring of frequent hazard processes in mountainous regions is of paramount importance due to their sudden occurrence, and the risk of causing numerous fatalities and significant economic damage. The recent collapse of the Brienz/Brinzauls rockslide on June 15, 2023, in an active, deep-seated mountain slope deformation complex in Switzerland, provides a unique opportunity to investigate the evolution of precursors leading up to the collapse. Early identification of accelerating rockmass enabled us to set up a network of five broadband seismometers, strategically deployed to systematically record seismic signals in close proximity, reducing information loss due to attenuation of seismic waves. 

The internal rock damage dynamics in the displacing rock mass were interacting with external seasonal forcings, such as snow melt and rainfall, for years preceding the collapse at approximately 21:38:00 UTC on June 15, 2023. Seismic events of various types have been detected in the entire landslide complex, characterised by the recurrence of identical seismic events that aggregate prominently within the most rapid compartment, referred to as the "Insel," positioned directly above the village of Brienz. This study aims to investigate the influence of seasonal forcings on accelerating the rate of displacements and to understand how the nature of detected precursors changes over time. We systematically examine the feedback loop between seasonal triggers and gravity-driven internal rock damage under changing stress conditions during fluctuations in compartment velocity. Initially, events exhibit accelerations following periods of precipitation, but subsequently, a runaway acceleration in seismic events was noted even during dry periods. The locations detected reveal communication between the upper and lower parts of the “Insel” mass in the build-up to the main collapse. From June 1 onward, there is a consistent and gradual increase in the mean spectral power of the recurring seismic events, with a rapid escalation observed in the three days leading up to the collapse. Interestingly, on the final day preceding the main collapse, a significant decrease in the mean spectral power was identified. To complement seismic observations, the spatial and temporal changes in pre-failure slope instability for the period 05.2014-06.2023 were also analyzed using Sentinel-1 synthetic aperture radar (SAR) data using a multi-temporal interferometric (MTI) approach. MTI analysis indicates several patches of instability and surface deformation on the slope, along with signs of significant surface displacement of a few centimetres per year, also manifesting in the village of Brienz. To facilitate automatic detection and classification, we apply data science methods to various statistical seismic attributes of the identified precursors. This study contributes to advancing our understanding of the mechanisms leading to rockslide collapses, with the potential to significantly enhance warning system effectiveness.

How to cite: Dash, S., Dietze, M., Walter, F., Fulde, M., Wang, W., Motagh, M., and Hovius, N.: Analysis of Precursors and Collapse of June 15, 2023, Brienz/Brinzauls Rockslide in Switzerland: Integrating Seismic and Remote Sensing Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13208, https://doi.org/10.5194/egusphere-egu24-13208, 2024.

Reliable bedload flux estimations are necessary for a variety of applications such as sedimentation engineering, flood risk mitigation and river restoration. Several seismic physical models with considering different bedload transport mechanisms have been proposed, which provided an opportunity to have quantitative observation in practical. However, a lack of direct measurements of bedload fluxes in field application cause a challenge for the validation of seismic models. In the practical application, the bedload impact kinematics (elasticity and velocity) and particle dynamics assumed in models are crucial for achieving high accuracy in bedload inversion. In-situ seismic parameters such as shear-wave velocity and seismic quality factor are also required to reduce the uncertainty in model prediction. Thus, this study first conducts bedload transport experiments in a flume laboratory to understand the kinematics and mechanics of particle transport by using the smart rock embedded with accelerometer and gyroscope, geophone and hydrophone. For the field-scale experiments, we further studied distributed acoustic sensing (DAS) measurement during the experiments, which can record the dynamic strain in fiber optic cable under riverbed. Both case of laboratory flume and field-scale experiments, we will evaluate the performance of the different physical models by comparing in-situ measurements of bedload mass and impact forces recorded by the smart rock. In the case of field experiment, we adopted the active and passive seismic surface wave exploration to investigate the properties of wave propagation and attenuation. The effect of the process of rolling and/or sliding particles, as opposed to saltating particles, contributing in seismic signal generation, was also explored.   

How to cite: Chao, W.-A., Hung, C.-Y., and Chen, Y.-S.: Validation of seismic bedload saltation model: From laboratory flume to field-scale experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13569, https://doi.org/10.5194/egusphere-egu24-13569, 2024.

Bedload transport plays a key role in the morphodynamics of mountain rivers by regulating erosion and aggradation processes. However, it is still challenging to estimate and predict bedload transport rates with reliability because of a complex interplay between different types of sediment supply, hydrological forcing, and fluvial morphologies. In the last two decades, passive sensors recording the seismic signals generated by coarse particles impacting the riverbed have been proposed to provide a continuous indirect measure of bedload transport. Among them, geophone plates and seismometers have been demonstrated to be valid tools.

Here, we present the preliminary results from the new monitoring station of Stilfserbrücke/Ponte Stelvio designed and built to monitor both water and sediment fluxes in the Solda River (Italian Alps). The station, mainly financed through two ERDF 2014-2020 projects of the Autonomous Province of Bolzano South-Tyrol, is part of the operational gauging network of the Civil Protection Agency of Bolzano (Italy). Bedload transport is indirectly monitored by sixteen geophone plates covering the downstream side of a consolidation check dam. The signal associated with the vibrations generated by particle impacts on the steel plates is recorded continuously with a sampling frequency of 5 kHz. In order to calibrate the instruments, direct bedload measurements have been carried out through an innovative bridge-like structure (BLS) consisting of an electronically controlled mobile trap. The collected samples have been sieved by hand to characterize their grain size distribution. At the end of summer 2023 we have also explored the possibility to additionally monitor the river with seismometers installed on the left bank at the monitoring station. We have analyzed the signal from the geophone plates by counting the number of times its amplitude exceeds a preselected threshold expressed in volts (i.e. the impulses, Rickenmann et al., 2014), and by computing its power (Coviello et al., 2022). The best correlation is found between impulses (threshold of 0.04 V) and the bedload transport rates of particles larger than 22 mm, with a power law regression characterized by a coefficient of determination (R²) of 0.85 and a low root mean square error (RMSE) of 3.3 kg/min against peak bedload transport rates reaching 41 kg/min.

These findings pave the way towards ensuring the continuous quantification of coarse sediment transport in the Solda River, allowing for the evaluation of the impact of glacier retreat and slope instabilities associated with global warming on river dynamics. Finally, the simultaneous use of seismometers may provide a unique opportunity to test existing theoretical models on bedload-induced ground vibrations through the indirect measurements provided by the geophone plates.

References

Coviello, V., Vignoli, G., Simoni, S., Bertoldi, W., Engel, M., Buter, A., et al. (2022). Bedload fluxes in a glacier-fed river at multiple temporal scales. Water Resources Research, 58, e2021WR031873.

Rickenmann, D., Turowski, J.M., Fritschi, B., Wyss, C., Laronne, J., Barzilai, R., Reid, I., Kreisler, A., Aigner, J., Seitz, H. and Habersack, H. (2014), Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel-bed streams. Earth Surf. Process. Landforms, 39: 928-942.

How to cite: Piantini, M., Bonfrisco, M., Nadalet, R., Dinale, R., Vignoli, G., Antonacci, G., Simoni, S., Zanotti, F., Crema, S., Cavalli, M., Sarretta, A., Coviello, V., and Comiti, F.: Investigating bedload transport in mountain rivers through seismic methods: the new monitoring station in the Solda River (South Tyrol, Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13722, https://doi.org/10.5194/egusphere-egu24-13722, 2024.

Solid Earth Sciences：SE07 Faults and Earthquakes: Networks, Precursors, Monitoring Systems and Numerical Modelling Techniques

Research on new methods and equipment for seismological monitoring of glaciers on the Qinghai-Tibet Plateau

Lei Zou¹, Richard Games², ……

¹ SmartSolo Inc., China

² SmartSolo Inc., Huston, USA

Abstract: Glacier seismology combines the advantages of glaciology and seismology to form a young interdisciplinary subject. Icequakes are vibrations produced during the movement and breakup of glaciers, ranging from small squeaks to sudden ruptures or slides equivalent to earthquakes (MW7). According to the location and mechanism of icequake occurrence, icequakes can be divided into five types: surface fissures, stick-slip movement, iceberg calving, subglacial flow, and hydraulic fracturing. In addition to traditional seismological methods, icequake research can also be conducted using multidisciplinary methods such as GPS, numerical simulation, and glacier physical properties. Icequake research can further explore the occurrence process and risk assessment of ice avalanches. We review advances in glacier seismology.

Our users use SmartSolo scientific instruments to successfully analyze ice avalanche events through vibration signals by observing multi-parameter glacier environment and climate changes, combined with seismological observation instruments. Provide a new and effective monitoring method for glacier seismic monitoring. It enriches the process observation and risk assessment methods of ice avalanche occurrence, and the combination of multiple parameters further improves the accuracy and effectiveness of ice avalanche event monitoring.

How to cite: Gamez, R. and Zou, L.: Research on new methods and equipment for seismological monitoring of glaciers on the Qinghai-Tibet Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13798, https://doi.org/10.5194/egusphere-egu24-13798, 2024.

In 2022 a network of 23 seismometers and Distributed Acoustic Sensing (DAS) fibre optic cable were deployed on the North East Greenland Ice Stream (NEGIS). Using a combination of environmental seismology methods, we were able to gain a comprehensive understanding of the ice streams internal structure, giving insight into its past and present dynamics.  

From ambient noise recording, we utilise the 9-component correlation tensors associated with all station pairs.  We derived dispersion curves for Rayleigh and Love wave group velocities with usable data in the frequencies from 1 to 25 Hz. These data are then inverted to obtain shear wave velocity measurements for the top 150 m of the ice stream using an MCMC approach. We reveal variations in the radial anisotropy for both the along and across-flow components.

Alternative methods of passive seismology were explored, such as using the seismic signal from an airplane landing. The recorded signals by the surface DAS cable displayed exceptional clarity, revealing at least 15 visible wave propagation modes, including various Rayleigh and pseudo-acoustic waves within the frequency range of 8 to 55 Hz.

Seismic While Drilling (SWD) methods utilising the noise from ice core drilling and cutting at NEGIS were investigated as an unconventional signal at the borehole camp. While not successful in this instance, recommendations for future deployments were provided to optimize the utilisation of these techniques.

These methods collectively offer insight into the layering of snow, firn, and ice within the ice stream, indicating the presence of seismic anisotropy. Demonstrating the effectiveness of short-duration (2-3 weeks) seismic deployments in glaciology.  

How to cite: Pearce, E., Zigone, D., Fitchner, A., Hofstead, C., Rimpot, J., Brehmer-Moltmann, J., and Eisen, O.: An overview of environmental seismology used to study the internal structure of the North East Greenland Ice Stream , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13859, https://doi.org/10.5194/egusphere-egu24-13859, 2024.

Southern Taiwan often experienced abundant monsoon seasons during seasonal transitions, and monsoons and typhoons controlled the rainfall patterns to be complex and varied, resulting the high intensity, prolonged duration, and high concentration. The aforementioned rainfall characteristics can increase the risk of water-and-sediment-related disasters.  To explore the correlation between rainfall patterns and water-and-sediment events, this study employs micro-seismic monitoring network, and the selected Putanpunuas River in southern Taiwan as a case study site. Frequent landslides in the middle and upper watershed supply the river with stable source of sediment materials. Consequently, during the periods with strong precipitation, our study site the shows high susceptibility of water-and-sediment events.  The seismic network comprises one station (BNAR) on the right bank and two stations (BNAL, BNAS) on the left bank downstream of the Putanpunuas River, and an additional station (BNAF) at the confluence of the Putanpunuas River and the Laonong River.  By conducting a series of spectrogram analysis, the average power spectral density (PSD) time series of each station can be computed. Then, we further quantified the seismic signal characteristic parameters for each water-and-sediment events.  This study initially employs various machine learning algorithms (Decision Tree, KNN, K-means, Auto-sklearn) to develop an optimized model for identifying water-and-sediment events, classifying different types of events, such as flooding (FD), debris flooding (DFD) and debris flow (DF), then providing a 4-year-length (2019~2023) catalog of water-and-sediment events.  Rainfall data including hourly precipitation and LiDAR estimated rainfall are collected from the rain gauge stations nearby study area. Using a certain definition (e.g., 4 mm/hr threshold for picking start time) of rain episodes, we calculated total number of episodes and established a rain episodes catalog.  The aforementioned datasets allow us to probe the relationship between rainfall patterns and water-and-sediment events, aiding in inferring the main rain episodes characteristics associated with water-and-sediment events . The  results of this study can be applied to predict potential water-and-sediment event types in Putanpunuas River using rainfall information as input. This can facilitate relevant early warning operations, reducing the societal impact of water-and-sediment disasters.

Key words : Rainfall Patterns, Rain Episode, Micro-seismic monitoring network, Putanpunuas River, Water-and-Sediment Events, Machine Learning

How to cite: Huang, G.-S. and Chao, W.-A.: Probing relation between rainfall pattern and seismic detected water-and-sediment events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14117, https://doi.org/10.5194/egusphere-egu24-14117, 2024.

A dam is the natural damming of a river by the geohazards, such as landslides and debris flows. When the dam materials are eroded or washed away due to scour, erosion, and/or an increasing in water level of dam lake, leading dam breach and catastrophic outburst of flooding, which affect the downstream area. Therefore, real-time monitoring of dam failure would facilitate relevant early warning message for the impending floods. The conventional approach using image-based analysis and hydrological measurements is for providing timely warnings of breach; however, landslide dams often occur in mountainous areas, where the methods may face limitations of in-situ measurement. Additionally, the observations of landslide dam breach process are rare and cause the large uncertainties in scientific research. Hence, this study utilizes seismic signals to study the overtopping breach process of field-scale dams. Seismic signals serve as a monitoring tool while simultaneously monitoring the seismic characteristics of overtopping failure in the field-scale dams. In fact, there is a scarcity of observed seismic signal records related to dam breach process in field. Even if some observational data is available, there is a lack of corresponding image analysis or hydrological information for comprehensive discussions. Thus, this study aims to observe and understand overtopping failure through a series of field-scale dam breach experiments. In this study, we first investigate the time-frequency characteristics of seismic power spectral density (PSD) corresponding to the dam breaches primarily involves retrogression erosion, longitudinal and lateral erosion, and the stabilization period. Then, the results of photographic analysis (surface flow velocity, breach geometry), discharge measurements and the time-frequency characteristics of PSD are integrated to discuss the phenomena associated with dam breach. Finally, a series of comparison between compacted and non-compacted dams for PSD spectrogram patterns. The time-series of mean PSD and flow discharge data for the compacted dam exhibit a single-peak and short-term signal duration. Notably, the mean PSD time-series recorded by the seismic station located at the left bank showed a similar trend with flow discharge. Furthermore, during the retrogression erosion period, significant high-frequency PSD energy can be observed only in a case of the compacted dam. In contrast, the PSD energy for the non-compacted dam is concentrated in a relatively lower frequency range (between 10 to 30 Hz). The PSD and flow time series data for the non-compacted dam present a bimodal shape with longer time duration. Based on the flow velocity of breach notch, both in the compacted and non-compacted dams, the maximum velocity occurred during the transition from longitudinal to lateral erosion. In practical application, the results of seismic characteristics for the non-compacted dam case can be applied to the monitoring of dams formed by natural landslides in the field. Our results not only advance in understanding of the field-scale dam breach process but also can be directly applied to breach flooding warnings.
Key words : field-scale dam breach experiments, overtopping breach, power spectral density, time-frequency characteristic

How to cite: Hou, Y.-L., Chao, W.-A., Hung, C.-Y., Chen, S.-C., and Chang, T.-Y.: Studying field-scale dam breach due to overtopping by using seismic signals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14125, https://doi.org/10.5194/egusphere-egu24-14125, 2024.

Rainfall, temperature variations, and chemical processes are well-known drivers of rock erosion. The impact of rainfall on rocks is not well-understood yet but may impact the mechanical properties (including damage, rigidity, deformation) of the rock. In this study, we exhibit the effect of rainfall events on the resonance frequency of a rock column.

Resonance frequencies of structures have been utilized to monitor rock columns due to their sensitivity to changes in the rock apparent rigidity (1). For instance, daily temperature changes induce stress variations in the rock column, resulting in a daily cycle of resonance frequency changes (thermal-acousto-elasticity, 2).

This research involves long-term monitoring of the first resonance frequency of a 50 m high limestone cliff covering the Chauvet cave in the Ardèche plateau, SW France, exposed to climatic solicitations including daily solar radiation, air temperature fluctuations, and rain events. The rock column was equipped with seismic and meteorologic stations and monitored continuously during three years.

To demonstrate the effect of rainfall events on the mechanical properties of the rock, we calculated the resonance frequency depending only on air temperature and solar radiation, using a simple bivariate linear regression. The regression provides well-fitting results for dry periods but shows larger deviations during most rainy periods. This indicates that rain has an effect on the changes in rock resonance frequency. Identifying and quantifying these changes would be a key factor in understanding the evolution of damage.

1) Bottelin, P., Baillet, L., Larose, E., Jongmans, D., Hantz, D., Brenguier, O., ... & Helmstetter, A. (2017). Monitoring rock reinforcement works with ambient vibrations: La Bourne case study (Vercors, France). Engineering Geology, 226, 136-145.

2) Guillemot, A., Baillet, L., Larose, E., & Bottelin, P. (2022). Changes in resonance frequency of rock columns due to thermoelastic effects on a daily scale: observations, modelling and insights to improve monitoring systems. Geophysical Journal International, 231(2), 894-906.

How to cite: Starke, J., Baillet, L., Larose, E., Guillemot, A., and Audin, L.: Investigating Rainfall-Driven Resonance Frequency Changes in a Natural Rock Formation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15165, https://doi.org/10.5194/egusphere-egu24-15165, 2024.

Distributed Acoustic Sensing (DAS) represents a leap in seismic monitoring capabilities. Compared to traditional single-seismometer stations, DAS measures seismic strain at meter to sub-meter intervals along fiber-optic cables thus offering unprecedented temporal and spatial resolution. Leveraging the resolution of DAS enables us to monitor and detect seismogenic processes in the domain of hazardous mass-movements, including catastrophic rock avalanches.

Here, we present a semi-supervised neural network algorithm for screening DAS data related to mass movements at the Brienz landslide in Eastern Switzerland, which partially failed on 15 June 2023. A DAS interrogator connected to a 10 km-long dark fiber provided by Swisscom Broadcast AG near the landslide recorded seismic data from 16 May to 30 June 2023, with a sampling frequency of 200 Hz and a channel spacing of 4m. During a test period from June 1 to June 19, 2023, a total of 634 characteristic waveforms potentially related to slope failures, including the 15 June 2023 event, were detected, along with vehicle and other anthropogenic noise sources with characteristic diurnal and weekday/weekend variations.

For information extraction, we selected a subset of adjacent DAS channels, which include cable sections that were parallel to the failure event trajectory and thus particularly sensitive to mass movement activity. To facilitate efficient processing, we downsampled the data to 20 Hz, considering that slope failure events predominantly excite seismicity at below 10 Hz. We conceptualize the DAS data as a series of images representing consecutive strain rate data in the two dimensions of time and space. To bring out signal coherence between DAS channels, we transform the waveforms into cross-spectral density matrices (CSDM’s) which serve as the input image for unsupervised feature learning using an autoencoder (AE). Leveraging the features learned from the AE, we focus on activity classification using approximately 1500 samples. As ground truth for the slope failure class, we utilize concurrent Doppler radar data. The radar provides an event magnitude, which scales with failure volume and the number of individual rockfalls. Furthermore, the radar provides a measure of the moving mass’s trajectory length and front speed. The radar detected 516 slope failures during the test period.

Our algorithm captures 41.09 % of the slope failures recorded by the Doppler radar. The undetected events mainly have low radar magnitudes suggesting that they are associated with mass movements generating reduced seismic activity. Among the slope failure-type signals detected by DAS, 87.85% are also present in the radar catalogue. Interference from vehicle or human-triggered seismic waves, deteriorating the signal-to-noise ratio significantly, poses a challenge for our algorithm to differentiate between slope failures and those activities. Our study thus provides a benchmark for future natural hazard monitoring and suggests that using existing fiber optic infrastructure has a high potential for early warning purposes.

How to cite: Kang, J., Walter, F., Paitz, P., Aichele, J., Edme, P., Fichtner, A., and Meier, L.: Automatic Monitoring of Seismogenic Slope Failure Activity at Brienz (Switzerland) Using Distributed Acoustic Sensing and Semi-Supervised Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15365, https://doi.org/10.5194/egusphere-egu24-15365, 2024.

Some of the more densely populated areas in Norway are in potential quick clay zones. When disturbed, the structure of quick clay can suddenly collapse, and behave and flow as a liquid, potentially having disastrous impact over large areas.  One of the triggering factors for quick clay slides is heavy rainfall. Here, we focus on passive seismic data from two Raspberry shake sensors located in an urban area in Oslo, Norway with quick clay in the subsurface. Using coda wave interferometry, near-surface velocity variations are estimated during the extreme weather ”Hans” (August 2023).

We compute auto-correlations and single station cross-correlations of anthropogenic seismic noise (> 1 Hz) over a two-year period leading up to ”Hans”. We observe environmental velocity fluctuations well correlated with air temperature, precipitation and the water level in a nearby river. In particular, freezing and thawing produces strong changes in seismic velocity (up to 4 %). Disregarding freezing, we see the largest change in seismic velocity following the heavy rainfall associated with ”Hans”. This extreme event is associated with a sharp velocity drop anti-correlated with pore pressure. The surface wave-coda is sensitive to changes in shear wave velocity, which in turn can be used to detect changes of the subsurface properties. Therefore, observed velocity variations at the site could have potential for monitoring and early warning of quick clay instabilities.

How to cite: Bruland, C., Köhler, A., Dichiarante, A. M., Oye, V., and Van Bever, I.: Monitoring subsurface changes in a quick clay area during extreme weather, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15794, https://doi.org/10.5194/egusphere-egu24-15794, 2024.

Debris flow can cause severe damage due to its high velocity, large volume, and long transport distance. The monitoring and early warning system is one of the key approaches in debris-flow hazard mitigation. Monitoring and early warning equipment are easily damaged by debris flows, which directly affects the monitoring system. In recent years, environmental seismology has provided a new research method for debris flow monitoring and early warning due to the advantages of long-distance, non-contact monitoring and rich, dynamic information. However, we still lack essential understanding regarding the relationship between the basal force and physical properties of debris flow at the channel bed and the relationship between the impact mechanisms of the granular flow barrier and the generated seismic signal. We designed a series of flume experiments to analyze the distribution of base force and the link between the impact mechanism and seismic signals in geophysical flow. We examine the probability density function (PDF) of the basal impact force and establish a relationship between the PDFs distribution parameters and the geophysical flow's physical properties. We found that there are peak amplitude thresholds of the seismic signal that can distinguish between runup and pile-up mechanisms when considering engineering mitigation measures in the channel. Finally, by integrating laboratory experiments and field monitoring, we establish the relationship between seismic signals and debris-flow dynamics.

How to cite: Cui, Y., Zhou, X., Yan, Y., and Tang, H.: Analysis of debris-flow dynamics based on seismic signals: Insights from laboratory experiments and field monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16318, https://doi.org/10.5194/egusphere-egu24-16318, 2024.

In Oman, the frequency of flash floods has significantly increased in recent years. This phenomenon is correlated with climate change, resulting in an intensification of the atmospheric water cycle. Consequently, a further escalation of flash floods can be anticipated in the future. In Oman, the issue of flash floods is exacerbated by the frequent occurrence of tropical cyclones. Furthermore, the rapid expansion of urban areas, in some cases extending directly into wadis, coupled with the advancing sealing of the ground and insufficient drainage systems, leads to an increased risk of flooding. This is accompanied by substantial property damage and recurring loss of life.

Despite the growing danger posed by flash floods, there is currently no early warning system for precise prediction of these events in Oman. To establish such a system, densely distributed networks for rainfall and water level measurements would be required. However, due to the challenging topography and vastness of the country, implementing such networks is currently not feasible.

Recent studies have shown that seismic sensors could be used for measuring flow conditions. Further, seismic networks could be utilized to detect and track extreme flow events. The increasing availability of low-cost seismic sensors opens up the possibility of instrumenting previously ungauged wadi systems. However, the question remains if seismic networks can pick up smaller flow events and flow events happening in multiple smaller catchments at the same time.

In this study we used flow data from wadi gauge stations in the Al-Batinah Region (NW Oman) and data from broadband seismometers of the Earthquake Monitoring Center to research how flow events of various sizes can be detected by seismic networks. Initial results suggest that flow regimes in wadi systems offer favourable conditions for detection, as they mainly change between flow and no flow conditions. As the amplitude of seismic signals decreases with distance from the source, detection range is limited by background noise. To overcome this, low-cost seismic sensors have recently been installed in a wadi system together with camera based river gauges. Further work utilizing this data is currently ongoing.

How to cite: Krüger, R., Dietze, M., Blanch, X., Grundmann, J., El-Hussain, I., Al-Rawas, G., and Eltner, A.: Detection and localisation of wadi flow events utilizing seismic sensors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16742, https://doi.org/10.5194/egusphere-egu24-16742, 2024.

Our planet experiences ongoing unrest across various scales, from human footsteps to the powerful forces of volcanic eruptions and megathrust earthquakes. Seismic sensors, typically employed for geophysical studies, record diverse phenomena, including ground vibrations caused by the movement of terrestrial animals, known as footfall signals. The recently released SeisSavanna dataset comprises approximately 70,637 footfall signals from 11 different species in the African savanna. Consequently, ground-based vibrations might represent an underexplored sensory mode for continuously monitoring habitat usage and undisturbed animal behavior. To gain a deeper understanding of footfall signals, we conduct exploratory data analysis on the SeisSavanna dataset. Utilizing a scattering transform, we capture the distinctive features of footfall signals, creating a high-level and interpretable data representation for subsequent analyses. Seismogram atlases and clustering enable us to group similar types of footfall signals and investigate the signal-altering path and site effects, providing a comprehensive overview of the entire dataset. Moreover, this data-driven approach serves as a quality check for the species labels retrieved from co-located camera traps with a limited angle of view.

How to cite: Steinmann, R., Nissen-Meyer, T., Cotton, F., Tilmann, F., and Mortimer, B.: Towards seismic monitoring of terrestial ecosystems: an exploratory data analysis of the SeisSavanna dataset, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17219, https://doi.org/10.5194/egusphere-egu24-17219, 2024.

Since last decades, coda wave interferometry (CWI) from ambient seismic noise has become an efficient method to probe continuous temporal changes of mechanical properties of the subsurface and crust. This method has successfully been used for environmental seismology issues, in a view of investigating the response of subsurface to environmental changes, in particular hydrological and thermal forcings ⁽²⁾. More, it has contributed to monitoring instabilities such rock slopes or landslides ⁽³⁾. Applying these methods to permafrost is then relevant to assess and monitor its mechanical response to environmental forcings.

As lobate or tongue-shaped superficial landforms composed of frozen rock debris, active rock glaciers are widespread features of mountain permafrost ⁽⁴⁾, potentially causing emerging hazards linked to permafrost thawing and debris flows.

Passive seismic instrumentation has been deployed for several years at Gugla, Tsarmine (Valais, Switzerland) and Laurichard (Hautes-Alpes, France) rock glaciers.

CWI has been applied to compute daily averaged dV/V (or relative change in velocity of the surface waves). For the three sites studied, seasonal variations of shear stiffness have been measured, associated with freeze-thawing cycles ^{(5) (6)}. We located these daily fluctuations in depth by using a 1D coda wave inversion scheme. We also tracked water-induced power spectral density (PSD) and we detected microseismic events, highlighting the role of water inputs in changing the mechanical state, thus accelerating the whole rock glacier body. Also, we developed a viscoelastic model to explain the seasonal variability of the kinematics of rock glaciers. Combined with other geophysical methods, environmental seismology paves hence the way to deeply understand the mechanical response of mountain permafrost landforms to thermo-hydrological forcings.

 References

• Richter, T., Sens‐Schönfelder, C., Kind, R., & Asch, G. (2014). Comprehensive observation and modeling of earthquake and temperature‐related seismic velocity changes in northern Chile with passive image interferometry. Journal of Geophysical Research: Solid Earth, 119(6), 4747-4765
• Le Breton, M., Bontemps, N., Guillemot, A., Baillet, L., & Larose, É. (2021). Landslide monitoring using seismic ambient noise correlation: challenges and applications. Earth-Science Reviews, 216, 103518.
• Haeberli, W., Hallet, B., Arenson, L., Elconin, R., Humlum, O., Kääb, A., ... & Mühll, D. V. (2006). Permafrost creep and rock glacier dynamics.Permafrost and periglacial processes, 17(3), 189-214.
• Guillemot, A., Helmstetter, A., Larose, É., Baillet, L., Garambois, S., Mayoraz, R., & Delaloye, R. (2020). Seismic monitoring in the Gugla rock glacier (Switzerland): ambient noise correlation, microseismicity and modelling.Geophysical Journal International, 221(3), 1719-1735. https://doi.org/10.1093/gji/ggaa097
• Guillemot, A., Baillet, L., Garambois, S., Bodin, X., Helmstetter, A., Mayoraz, R., and Larose, E.: Modal sensitivity of rock glaciers to elastic changes from spectral seismic noise monitoring and modeling, The Cryosphere, 15, 501–529, https://doi.org/10.5194/tc-15-501-2021, 2021.

How to cite: Guillemot, A., Larose, E., Baillet, L., Helmstetter, A., Bodin, X., and Delaloye, R.: Monitoring the mechanics of mountain permafrost using ambient noise seismology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17786, https://doi.org/10.5194/egusphere-egu24-17786, 2024.

Microseism is one of the biggest parts of ambient seismic noise and has a huge effect on seismic measurements on almost every regular broad band seismometer, but especially in coastal areas. Generally, microseism describes the interaction of water waves and the seafloor. Its variation over time is from huge interest. It is often used on short-period scales to investigate local weather effects, like storm events or seasonal variations. In this work, we are investigating variations in the microseism of the Northern Atlantic on multiannual scales. For that reason, we utilize up to 50 years of seismic data from several onshore stations across Central and Northern Europe. The focus is on secondary microseism of the Northern Atlantic which is normally sensitive at periods of ≈10 to 5 s. It is estimated over two-hour segments of seismic data, separately. Secondary microseism is post processed to eliminate effects of data gaps or outliers before lowpass filtering for the periods of interest. Besides of a dominant peak at one year period, secondary microseism shows also distinct variations at several year of periods. These variations clearly correlate with the North-Atlantic-Oscillation Index (NAO), not only visually, but also quantitatively and might therefore be relatable to climate variations affecting the North Atlantic.

How to cite: Wiesenberg, L., Schmidtko, S., and Meier, T.: (Multi)annual variations in the microseism of the Northern Atlantic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17787, https://doi.org/10.5194/egusphere-egu24-17787, 2024.

Predicting bedload transport is a key element of water-related hazard assessment and hydraulic engineering applications. However, knowledge of bedload transport processes remains limited, particularly in steep mountain streams. Previous studies have revealed that bedload transport rates in mountain streams exhibits a large spatio-temporal variability for given flow conditions. This results from the direct influence of streambed structure on bedload transport, where sediment movement, in turn, interacts with streambed evolution. Furthermore, variations in sediment availability contribute to the spatio-temporal bedload variability. The complex interactions between water flow, bedload transport, and bed structure are not yet fully understood. In this work, systematic flume experiments were conducted to investigate the acoustic signal responses of impact plate geophone systems generated by bedload particles impacting on the flume bed during experimental flows in the transitional regime. The experiments varied in the grain size distribution of the transported particles and the bed material, and the compactness and the water content of the flume bed. Geophones were installed on the underside of steel plates flush with the flume bed both upstream and downstream to effectively capture the changes in vibration signals generated by the moving bedload mass impacting on the bed. Triaxial force sensors were utilized to measure the impact forces of the bedload particles on the bed material layer. Pore-water pressure sensors were embedded at different depths in the bed material to measure the change in pore-water pressure in the bed under the influence of the bedload mass. Flow velocities and depths of the moving bedload mass were recorded using a binocular high-speed camera and were analyzed with an image processing method. The observed vibration signals and fluctuating forces were used to calculate the characteristic parameters of bedload transport using calibrated relationships and seismic theory. In addition, a high-precision Digital Elevation Model (DEM) of the bed was constructed using the photography and 3D modeling techniques. The results of this work show that geotechnical material parameters of the bed such as compactness, compression modulus, and grain size distribution may affect the changes of bed structure caused by bedload transport This in turn influences the spatio-temporal variability of the transport rate. The findings of this work may help to explain the variability of the bedload transport process in mountain streams.

How to cite: Chen, Z., Badoux, A., and Rickenmann, D.: Quantitative measurement of bedload transport variability with acoustic monitoring systems: Insight from controlled laboratory flume experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18262, https://doi.org/10.5194/egusphere-egu24-18262, 2024.

Glaciated landscapes are showing an amplified reaction to global climate change. Glacial streams are the primary conveyor belts of the incipient sediment cascade, implementing the export of glacially scoured sediment to lower reaches, where the exported sediment controls fluvial geometry, valley floor evolution and ecosystem functioning, water reservoir lifetime and energy production in several alpine countries. Despite that importance, especially of the coarse bedload fraction, there is a striking lack of knowledge about the timing, magnitude and control factors of bedload flux in glacial streams. This is predominantly due to the difficulties to obtain such flux data by classic empirical approaches that require direct in-stream sampling. Here, we pursue a seismic approach to bedload transport quantification, where geophysical sensors are installed along the banks of glacial streams that continuously record ground motion caused by both the turbulent flow of the stream and coarse particle impact on the river bed. We installed small geophone networks along straight reaches of streams draining the glacierised catchments of Oberaargletscher and Steingletscher in Switzerland and recorded the target signals for several days in August 2022, when the melt driven, diurnal river stage fluctuated significantly. River level, turbidity and stream geometry were also observed. Ground parameters for the inverse seismic-model approach were determined using an active seismic survey. We present results of the instrumentation concepts, parameter estimation and data inversion. This allows a discussion of the temporal variability, non-linearity and site-specific nature of hydraulic and sediment transport patterns in catchments where sediment export is dominated by glacial processes.

How to cite: Cook, S., Swift, D., Cook, K., Andermann, C., Dietze, M., Wenban, W., and White, R.: Bedload sediment dynamics in two contrasting alpine glacier headwater catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18668, https://doi.org/10.5194/egusphere-egu24-18668, 2024.

Turbulent flows capable of mobilizing sediments, despite being studied over the past 100 years, continue to constitute an elusive process. In environmental seismology, seismic waves generated by the interplay of surface processes and the Earth offer a key to unraveling the dynamics of river processes. We studied the seismic signals emitted during floods in two tributaries with large boulders. Early findings indicated an unusually high dominant seismic frequency, reaching 2-4 times the frequency observed in nearby channels with smoother beds. Consistent anomalous high-frequency content during times without sediment transport prompts our hypothesis that turbulence is the key process driving the frequency shift. We hypothesized that the most energetic turbulent eddies, dominating the signal, decrease in size in response to the boulder-influenced constrained flow geometry, and we argue that this effect possesses a first-order control on the frequency shift. A frequency scaling law with boulder spacing, approximating boulder-induced eddy size, shows good agreement with our field data. The dynamics of the eddies under changing flow velocity are well predicted by a power law function of seismic frequency with water depth. The trend breaks at the onset of bedload transport, indicating that energy is dissipated through the partitioning between turbulence and sediment transport. Our study emphasizes that seismic frequency effectively records the dominant morphology and fluvial processes, revealing the intricate interaction between roughness and seismic energy.

How to cite: Nativ, R., Laronne, J., Turowski, J., Chang, J.-M., Yang, C.-J., Hovius, N., Chen, W.-S., and Chang, W.-Y.: Boulder-induced Turbulence Drives Shift in Seismic Frequency, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20192, https://doi.org/10.5194/egusphere-egu24-20192, 2024.

Landslides present a substantial hazard across coastal and mountainous regions in Europe and worldwide, and are becoming increasingly prevalent due to extreme rainfall linked to climate change. There is a need to develop new technologies for landslide monitoring and early warning systems, as traditional approaches alone are insufficient due to low temporal resolution and high costs. The SENSUM project (smart SENSing of landscapes Undergoing hazardous hydrogeologic Movement) has deployed manmade boulders, called SlideCubes, that monitor landslide movement in real-time across two coastal slow-moving landslide sites in southern England (Lyme Regis and Isle of Wight).

SlideCubes are embedded with low-power low-cost sensors that comprise an inertial measurement unit (IMU with accelerometers and gyroscopes) and magnetometers. The SlideCubes are part of a wireless sensor network (WSN) that communicates via Long Range Wide Area Network (LoRaWAN) and Internet of Things (IoT) technologies. Rain gauges and other third-party sensors can be easily integrated into the network to provide additional data sources. Our novel WSN allows for near real-time wireless monitoring of the landslides, only requiring field visits to replace sensor batteries every 9-12 months. The sensors are motion-triggered, significantly saving battery power, meaning the WSN requires little and less frequent maintenance than other sensor-based monitoring approaches. This allows long-term remote measurement of landslide kinematics (inferred from SlideCubes) and initiation of movement, which is key for early warning.

In the present work, initial findings from the SlideCubes installed at two UK-based sites are discussed. The movement events detected and recorded over 2 years are validated by periodic GNSS and drone imagery surveys. We present an overview of temporal and spatial motion across both landslide sites and evaluate sensor performance. Using gyroscope and accelerometer readings from field and laboratory data, we demonstrate how types of motion (e.g. rolling, sliding) can begin to be categorised, which is not possible with the accelerometer alone. This research will be developed in future with machine learning to detect hazardous movement including large magnitude catastrophic events. These findings will be integrated into a SENSUM early warning online portal, in development, for use by stakeholders.

How to cite: Newby, K., Bennett, G., Roskilly, K., Sgarabotto, A., Luo, C., and Manzella, I.: Smart boulders for real-time detection of hazardous movement on landslides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-394, https://doi.org/10.5194/egusphere-egu24-394, 2024.

This study investigates sediment mobility and transport dynamics in two Himalayan rivers, the Aglar and Paligad Rivers, during both monsoon and non-monsoon flows. Employing the virtual velocity approach, key parameters such as bed proportional mobility (Y), active layer depth (d_s), and displacement length were measured to estimate the virtual velocity of mobilized grains. Local parameters (0.5 m sub-sections) and wetted cross-sectional averages were utilized. Using local parameters, the total annual bed material transport was determined as 67,100 t (±20,400 t) and 18,400 t (±6,000 t) for the Aglar and Paligad Rivers, respectively, with nearly 60% occurring during the monsoon. The significant contribution of non-monsoonal flows (~ 40 %) could be ascertained to higher enough flows in specific sub-sections inducing partial or full mobility. Still, the contribution of partial transport (PT) remained lower (< 6%). In contrast, based on cross-section average parameters, total transport was estimated at 42,300 t (±15,800 t) and 12,200 t (±4,700 t) for the Aglar and Paligad Rivers, respectively, with approximately 79% and 68% occurring during the monsoon. The contribution of PT increased to nearly 18% and 29% for the Aglar and Paligad Rivers, respectively, attributed to the averaging effects of shallower sections. Furthermore, the interdependence of partial transport on Y and full transport on d_s leads to discontinuities in transport curves, prompting the proposal of a unified function to represent transport extent for both partial and full transport conditions. The unified function ensured the generation of continuous transport curves, yielding similar transport patterns concerning the contribution of PT, FT, monsoonal, and non-monsoonal flows. The findings are particularly relevant for efficient river management as the region houses several hydropower plants and is highly susceptible to climate change.

Keywords:

Painted tracers, partial transport, full transport, active layer, monsoonal flows

How to cite: Yadav, A., Sen, S., Mao, L., and A. Hassan, M.: Estimating bed material transport in Himalayan streams using the virtual velocity approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-558, https://doi.org/10.5194/egusphere-egu24-558, 2024.

Sediment transport can occur in a so-called “debris flow” form, where concentrations are high and movement is driven by gravity. Previous studies have predominantly used simple rheological fluids or uniform granular materials to study the characteristics of debris flows. However, a fundamental question remains regarding the characteristics of the complex granular debris flow, and the transition from granular debris flow to bedload remains poorly understood. In this contribution, we present an experiment in the laboratory where this phenomenon could be studied. Our experiment setup, a 6-meter-long wooden flume, involved a 1 m-long low-slope trapezoidal storage area and a 5 m-long and 0.1 m-wide wooden flume channel inclined at 33%, equipped with a force plate and hydrometer sensors. Our observations show that self-formed, highly concentrated sediment accumulation in the storage area, influenced by flow rate, generates pulses that exhibit three phases: the tail phase containing sand particles, the body phase containing a mixture of particles, and the front phase containing coarse particles. As discharge was dynamically increased, two distinct domains controlled by the forefront coarse particles were observed. Firstly, at low flow (0.14-0.16 l/sec), a static-dynamic domain is identified, characterized by a high sediment concentration and very low velocity. This generates a high resultant force magnitude that affects the forefront coarse particles, resulting in debris-flow-like pulses controlled by the sediment density. Secondly, at higher flows (0.17–0.24 l/sec), a full-dynamic domain is identified, characterized by a lower sediment concentration and very high velocities. This behavior generates hyperconcenrated flow-like pulses controlled by momentum transfer between the pulse phases. We demonstrated that the transition from debris and hyperconcentrated flow to bedload is controlled by the coarse particle’s mobility, whose threshold discharge in clear water was 0.22 l/sec. The important role played by the sand fraction is also demonstrated, which permits the static dynamics behavior by ensuring momentum transfer either directly, by mass transfer, or indirectly by reducing the medium porosity.

How to cite: Koa, I., Recking, A., and Gimbert, F.: The Transition from Granular Debris Flow to Bedload: a force balance perspective, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1825, https://doi.org/10.5194/egusphere-egu24-1825, 2024.

In mountainous regions, the dynamics of bedload transport can vary considerably, including significant changes over brief periods, thus also posing a substantial challenge for bedload transport measurement and prediction. Indirect monitoring systems like the Swiss Plate Geophone (SPG) have led to a significant advancement in our capacity to continuously monitor bedload processes (Rickenmann, 2017). Based on recording important parts of the raw measuring signal of the SPG system, we have developed a procedure to determine fractional bedload transport rates (Wyss et al., 2016; Nicollier et al., 2022). For this, each sediment collision (for particles larger than 9.5mm) is recorded with the SPG system as a discrete «packet», capturing raw signal information such as collision start and end times, raw and envelope amplitude, squared integral, and centroid frequency of the raw signal.

This research undertakes a detailed analysis of continuously recorded packet data from the SPG for several mountain streams in Switzerland. It aims to quantify fractional bedload transport rates and grain size distribution across various periods. To check the plausibility of the calculated fractional transport rates, we aggregated the data based on the packet analysis and compared it to the so-called «impulse-based» conversion of the SPG signal into total transport rates (independent of grain size classes). The objective of this study is to enhance the understanding of how grain size distribution of the bedload alters with changing discharge and bedload transport conditions, by considering different channel characteristics and evaluation periods.

References

Nicollier, T., Antoniazza, G., Ammann, L., Rickenmann, D., and Kirchner, J. W.: Toward a general calibration of the Swiss plate geophone system for fractional bedload transport, Earth Surf. Dynam., 10, 929–951, https://doi.org/10.5194/esurf-10-929-2022, 2022.

Rickenmann, D.: Bed-load transport measurements with geophones and other passive acoustic methods, J. Hydraul. Eng., 143, 03117004-1-14, https://doi.org/10.1061/(ASCE)HY.1943-7900.0001300, 2017.

Wyss, C. R., Rickenmann, D., Fritschi, B., Turowski, J.,Weitbrecht, V., and Boes, R.: Measuring bed load transport rates by grain-size fraction using the Swiss plate geophone signal at the Erlenbach, J. Hydraul. Eng., 142, https://doi.org/10.1061/(ASCE)HY.1943-7900.0001090,04016003, 2016.

How to cite: Baldig, D. and Rickenmann, D.: Evaluation of continuously recorded fractional bedload transport rates in Swiss mountain streams, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3823, https://doi.org/10.5194/egusphere-egu24-3823, 2024.

Sediment is an intrinsic component of the fluvial network, supplying material for floodplains and coastal landforms which provide resilience during flooding and storms. As a result, an understanding of the fluvial processes that control how much sediment moves through our river systems, and how this varies across the globe, is of fundamental importance.

For the purpose of estimating sediment delivery through the fluvial network, it is often assumed that rivers are well mixed through their vertical extent. However, empirical data reveals that there is frequently large variability in the concentration of sediment through the water column. Better understanding this variability is of interest to the geomorphological community to help explain variations in sediment transport and improve estimates of sediment flux.

In this research, we utilise a collection of Acoustic Doppler Current Profiler (ADCP) data from large rivers across the globe to investigate variations in the vertical distribution of suspended sediment. Calibrations of ADCP backscatter to Suspended Sediment Concentration (SSC) from the wider literature are used, alongside median grainsize and acoustic frequency, to create a Machine Learning (ML) model from which SSC from uncalibrated ADCPs can be estimated. This new ML model is subsequently implemented to explore the variations in the vertical mixing of suspended sediment both temporally and spatially. This variability is explored to identify the importance of catchment characteristics in determining variations in suspended sediment concentration within the water column. Comparison of multiple river systems and their catchment characteristics, both between sites and through time, enables the identification of key attributes which exert a greater control on this variation through the water column. Subsequently, this leads to an improved understanding of sediment flux through the river system, whereby knowing the variation in sediment concentration within the water column can help to better calibrate current methods of estimating flux.

How to cite: Tomsett, C., Leyland, J., Darby, S., Gernon, T., Parsons, D., Hincks, T., and Wolstenholme, J.: Vertical Mixing of Suspended Sediment in Big Rivers using ADCP data and Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9717, https://doi.org/10.5194/egusphere-egu24-9717, 2024.

Understanding when gravel moves in river beds is essential for a range of different applications, but is still surprisingly hard to predict. The critical shear stress at which a grain will move depends on its relative size and structure within the bed, and spatial and temporal changes in grain-scale structure are likely to be a major driver of changes in critical shear stress. Consequently grain-structure metrics such as protrusion, pivot angle and contact with any surrounding fine grained matrix are used as parameters in models to predict critical shear stress, and so there is an increasing demand for measurements of these parameters in order to improve our predictive ability. However, we do not have established methods for measuring these parameters, nor do we know whether different methods provide consistent results. Here we present and compare new datasets of sediment structure metrics collected from eight locations in a small gravel-bed stream using three different methods: direct field-based measurements, terrestrial laser scanning (TLS), and computed tomography (CT) scanning. Using each method, we measure metrics including grain size distribution, grain protrusion and fine matrix content. We find that distributions of grain size are consistent between field-based and TLS data, but smaller in CT data. All three methods produce similar distributions of protrusion relative to grain size. There is also some consistency between field and CT measures of fine-grained matrix. However, the identification of similarity also depends on the type of analysis, and an alternative analysis shows less similarity in protrusion and fine-grained matrix between the different methods. Of the three methods, TLS-based approaches have potential to be most easily applied, and our analysis suggests that for grain-size and protrusion they perform as well as the alternative methods. However, they cannot currently be used for measuring fine-grained matrix content.

How to cite: Hodge, R., Voepel, H., Yager, E., Leyland, J., Johnson, J., Sear, D., and Ahmed, S.: Comparing methods to quantify grain-scale sediment structure in gravel-bed rivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11132, https://doi.org/10.5194/egusphere-egu24-11132, 2024.

Abstract: Sediment transport is a natural process where sediment particles can be deposited downstream and exacerbate flooding. The movement of sediments can be observed in flows through rivers, canals, and coastal areas which include suspended load transport and bed-load transport. Bed-load transport occurs in the area close to the riverbed, which is of particular importance in shaping the riverbed. The present research aims to investigate the sediment transport process by applying the Entropy concept as a theoretical approach to the activities of the project ‘Probabilistic floods and sediment transport forecasting in the Himalayas during extreme events’, funded in the context of the Italy-India joint science and technology cooperation program.

Specifically, based on collected field data through the Alaknanda River at Srinagar in India by current meter, first, the Entropy theory was applied to obtain the cross-sectional distribution of the velocity (based on recent developments of Entropy theory in Bahmanpouri et al., 2022a, b). The calculated mean velocity and discharge were compared with the observed data collected by the Central Water Commission (CWC). Next, shear velocity was calculated for different cross-sections based on different flow conditions. Further, shear stress was calculated based on two terms induced by skin friction and bedforms, respectively. Finally, the shield parameter was obtained based on shear velocity distribution to find out if sediment particles have the potential to be transported or not. Overall, the findings of the current research highlighted the potential of the theoretical method of Entropy to calculate sediment transport in developing countries.

Bahmanpouri, F., Barbetta, S., Gualtieri, C., Ianniruberto, M., Filizola, N., Termini, D., & Moramarco, T. (2022a). Prediction of river discharges at confluences based on entropy theory and surface-velocity measurements. Journal of Hydrology, 606, 127404.

Bahmanpouri, F., Eltner, A., Barbetta, S., Bertalan, L., & Moramarco, T. (2022b). Estimating the Average River Cross‐Section Velocity by Observing Only One Surface Velocity Value and Calibrating the Entropic Parameter. Water Resources Research, 58(10), e2021WR031821.

How to cite: Bahmanpouri, F., Barbetta, S., Massari, C., De Santis, D., Sharma, A., Agarwal, A., and Sen, S.: Application of Entropy theory to estimate the sediment transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11623, https://doi.org/10.5194/egusphere-egu24-11623, 2024.

Morphological changes in alluvial rivers are very active and remain very complex to predict because of the high spatio-temporal variability of bedload. This strongly limits the ability of river managers to assess risk or conduct ecological restoration. With the recent development of non-intrusive methods to monitor bedload, such as seismic or acoustic tools, acquisition of data has been highly facilitated compared to direct measurement methods involving in-situ sampling. The challenging task remains in the interpretation of the signals during phases of intense bedload transport which are responsible for major morphological changes. The analysis of such signals requires a good understanding of the underlying physics as well as in-situ field observations to confort interpretation. In this work, we combine seismic with timelapse camera observations with the objective to have a better understanding of bedload behavior and its consequences on the morphology during floods on an alluvial reach of the Severaisse river in the French Alps. Data consists in 3 seismic sensors continuously recording at 200Hz from upstream to downstream along the reach, as well as data from 2 cameras taking timelapse photos of the reach at a 10 min interval during flood. We We find that high frequency seismic power, attributed to bedload, exhibits a characteristic scaling relationship against discharge, materialized by two different phases: a scaling of about 5 from above the threshold of motion (around 12m3/s water discharge) up to a critical discharge of 25 m3/s, and a scaling of about 1.4 above 25 m3/s. We interpret the first scaling to be due to bedload occurring in a diluted regime as described in previous models, and the second scaling to be due to bedload in an intense transport phase. This shift only occur during floods where we observe channel shifting or important re-working of the bed and we suppose that it represents a phase of intense transport responsible for morphological changes. Interestingly, for the most extreme flood with a return period of 50-years, the seismic power versus discharge relationship shows a distinct behavior form the other floods, materialized by a particularly larger and singular hysteresis. Next steps include understanding why this distinct signature occurs, quantify the morphological changes by calculating indexes from image analysis and investigate how bedload and hence the morphological changes depends on the season, characterized by a snow-melting spring and summer and rainy autumn and winter through a multi-year scale.

How to cite: Johannot, A., Gimbert, F., Recking, A., and Piantini, M.: Using seismic and timelapse camera observations to study flood-induced morphological changes on an alpine gravel-bed reach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11689, https://doi.org/10.5194/egusphere-egu24-11689, 2024.

Bedload transport plays a crucial role in shaping landscapes, yet monitoring it is challenging. Seismic sensors have emerged as valuable tools for continuous and non-invasive bedload transport monitoring. However, isolating the seismic signal of bedload transport from other environmental signals such as flow turbulence remains a challenge. While seismic waves propagate both vertically and horizontally, previous seismic bedload transport studies focused solely on the vertical component. This was based on the assumption that the bedload transport signal was mainly contained in Rayleigh waves which propagate with both vertical and horizontal motion, as opposed to Love waves which propagate with only horizontal motion. We hypothesise that there may be a significant signal from horizontally-propagating waves that characterises the interactions of coarse bedload impacts, and that this signal will be strongest in a flow-parallel orientation.  

This study employs the Horizontal-to-Vertical Spectral Ratio (HVSR) which is a passive method, commonly used in engineering seismology, that determines the ratio between horizontal and vertical seismic signal components. In this study, we explore the potential of the HVSR method to isolate the dominant component in seismic bedload transport signals and its applicability for monitoring fluvial processes within rivers. Using seismic, hydroacoustic, and hydrological measurements from the River Feshie in Scotland, our findings challenge prior belief that the seismic signal of bedload transport predominantly resides in the vertical component; instead, the horizontal component contains significant fluvial and bedload transport information. Due to differences in seismic wave characteristics, the HVSR method acts as a tool to isolate signals of bedload transport and water turbulence.

Additionally, the HVSR method demonstrates promise in effectively filtering out meteorological signals that may contaminate raw river-induced seismic signals, enabling more accurate monitoring of bedload transport occurrences. However, we acknowledge that the contributions of horizontal and vertical signals greatly depend on sensor location and site characteristics. This study emphasises the significance of utilising horizontal seismic signals for comprehensive bedload transport monitoring, presenting an opportunity for this method to enhance our understanding of complex fluvial processes within river systems.

How to cite: Matthews, B., Naylor, M., Sinclair, H., and Gervais, M.: Exploring vertical component dominance in seismic bedload transport signals: Horizontal-to-Vertical Spectral Ratio (HVSR) analysis in the River Feshie, Scotland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12924, https://doi.org/10.5194/egusphere-egu24-12924, 2024.

We present results from a particle-scale numerical model inspired by the idea that a majority of the time during transport capable floods, bedload transport in rivers is rarefied, and a stochastic process. Physical experiments conducted by others to explore this idea suggest that the time varying particle activity N measured within a control area A above the bed surface is described by a Poisson probability mass function (pmf), assuming an absence of collective entrainment. This implies that particles are sporadically entrained from the bed surface at rate λ with no “memory” of prior entrainment events, when and where local flow conditions favor particle lift or dislodgement. In this context we developed a new open source kinematic particle-scale model written in Python (Zwiep and Chartrand, 2022). Notably, the model includes no information related to the bed surface shear stress or Shields conditions, and no sediment transport functions are used to drive the model.

The model domain measures a use specified length nD of the particle diameter D, with a width of 1D. At present we have tested the model with 30 simulations using a uniform particle diameter. Each simulation was run for 1 million iterations to explore the governing model parameters: SRe is the number of subregions within the domain length nD; E_n is the particle entrainment rate per iteration, which we randomly sample from a Poisson pmf for a specified value of λ; l_t is the particle travel distance which we randomly sample from either a lognormal distribution or a truncated normal distribution for specified values of the distribution expected value and standard deviation; and S_h is the vertical particle stacking height ranging from 1-3D.

The model produces a time varying signal of particle flux counted at downstream points of internal subregion domains, and at the downstream end of the model domain. The simplified particle bed changes “relative” elevation distributions through particle stacking and downstream motions of travel distance. An implication of particle stacking within the context of a stochastic model framework is a time varying signal of the average “particle age” defined as the number of iterations since last entrainment, as well as the average “particle age range” defined as the difference of the maximum and minimum particle ages, both metrics calculated at each iteration and across all subregions. The age dynamics correlate with the magnitude of N following an initial period of particle bed organization. Our initial tests suggest that the relatively simple model logic captures the essence of rarefied particle transport. We believe the model can be used to ask basic science questions, and as a classroom tool to introduce students to bedload transport in a straightforward and illustrative manner.

References:

Zwiep, S., & Chartrand, S. M. (2022). pySBeLT: A Python software package for stochastic sediment transport under rarefied conditions. Journal of Open Source Software, 7(74), 4282. https://doi.org/10.21105/joss.04282.

How to cite: Chartrand, S.: A simplified Python-based kinematic model of particle transport in rivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13064, https://doi.org/10.5194/egusphere-egu24-13064, 2024.

Bedload transport plays a vital role in shaping Earth’s environment by promoting the formation and growth of geological features of various scales, including ripples and dunes, deltas and fans, and laminations and cross-bedding. A key problem hampering our understanding of bedload-induced landscape evolution is the notoriously large variability commonly associated with measurements of bedload flux, even under controlled and highly idealized conditions in the laboratory, such as fully-developed, unidirectional open-channel flows over flat beds composed of grains of nearly uniform sizes. For example, two recent experimental studies report a nearly sixfold different nondimensionalized bedload flux at a comparable Shields number for spherical grains [1, 2]. The likely culprit is the immense difficulty experimentalists face in estimating the transport-driving bed shear stress. There is currently no universally accepted method of even determining the bed surface elevation in the presence of bedload transport, which is particularly problematic for shallow flows where small changes have a large effect. Neither is there agreement on how to account for the effects of sidewall friction, which become the stronger the smaller the width-to-depth ratio b/h of the open-channel flow. Standardly employed empirical sidewall corrections have arguably a greater resemblance to cooking recipes than to formal physically-derived methods. In addition to such experimental difficulties, there is the physical question of how grain shape, which usually is not controlled for in laboratory experiments, affects bedload flux. A recent prominently published study argued that grain shape is the predominant reason for bedload flux variability and put forward a semi-empirical, analytical bedload transport model to account for it [1].

Here, we compile data from existing experiments and existing and new DNS-DEM, LES-DEM, and RANS-DEM numerical simulations of turbulent bedload transport of shape-controlled grains, in which b/h varies between 0.1 and infinity (periodic boundary conditions in simulations). After employing a non-empirical sidewall correction, which we derived from the phenomenological theory of turbulence, and a granular-physics-based method to determine the bed surface elevation, all data for spherical grains of sufficient size collapse onto a single curve, resolving the experimental problem of bed shear stress determination. Furthermore, the combined data for spherical and non-spherical grains are in strong disagreement with the model of Ref. [1] but support our alternative analytical bedload model across grain shapes, bed slopes, flow strengths, and channel widths.

[1] Deal et al., Nature 613, 298 (2023). https://doi.org/10.1038/s41586-022-05564-6

[2] Ni & Capart, Geophysical Research Letters 45, 7000 (2018). https://doi.org/10.1029/2018GL077571

How to cite: Pähtz, T., Chen, Y., Xie, J., Monthiller, R., Maurin, R., Tholen, K., Ho, H.-C., Hu, P., He, Z., and Durán, O.: Resolving bedload flux variability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16886, https://doi.org/10.5194/egusphere-egu24-16886, 2024.

Currently, the estimation of suspended sediment concentration (SSC) fluxes in rivers relies on river discharge and an average SSC, the latter is commonly determined through optical turbidity measurements at a single point in the river cross-section. This approach has limitations, such as the SSC data being extrapolated from a one-point measurement and indirectly determined depending on regular sampling and laboratory analysis, which is cost-intensive.

Hydro-acoustic echosounders are an alternative to derive SSC across an entire profile, for accurate conversion from backscatter intensity to SSC knowledge of particle size is a requirement. In this approach, we present a method utilizing multi-frequency hydro-acoustic echosounding in addition to velocity measurements via an ADCP. Operating on various acoustic frequencies allows for the direct estimation of mean particle size from backscatter data at different frequencies over a water profile. River in-situ measurements as well as laboratory experiments have been conducted in different concentration as well as particle size distribution regimes.

How to cite: Höllrigl, J., Blanckaert, K., Hurther, D., Fromant, G., and Storck, F. R.: Hydro-acoustic multi-frequency measurements of suspended sediment flux in rivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18899, https://doi.org/10.5194/egusphere-egu24-18899, 2024.

Moisture is a crucial environmental factor that shapes the dynamics of aeolian sediment transport along coastal beaches. Despite the existence of empirical formulations, little is known about the mechanism through which moisture influences this dynamic process. To address this knowledge gap, we present a numerical modelling framework implemented in the open-source software package MercuryDPM [1].
This framework combines a discrete particle model, a one-dimensional airflow model and a liquid migration model. The two-way coupling between the discrete particle model and the airflow model can accurately represent the momentum exchange between these phases, yeilding reasonable sediment transport rates [2]. The inter-particle moisture distribution is modelled by a liquid migration law, which governs the presence of liquid films covering the particle surfaces and liquid bridges spanning the particle contacts [3]. The liquid bridge model introduces a static capillary force as well as a dynamic lubrication force, which is necessary to model the dynamic effects of moisture. This comprehensive model effectively captures particle behaviour under moist conditions and demonstrates the dependence of bed erodibility on particle impact and wind entrainment for varying moisture levels.
Our approach provides valuable insights on the moisture effect in aeolian sediment transport. It advances our understanding of this complex phenomenon, and gives insights on the development of geomorphological patterns at coastal sandy areas. With its flexilibity and versatility, it can be extended to study many more specific processes related to sediment transport.

[1] Weinhart, T., Orefice, L., Post, M., et al (2020). Fast, flexible particle simulations—an introduction to MercuryDPM. Computer physics communications, 249, 107129.
[2] Campmans, G., & Wijnberg, K. (2022). Modelling the vertical grain size sorting process in aeolian sediment transport using the discrete element method. AeolianResearch, 57, 100817.
[3] Mani, R., Kadau, D., Or, D., & Herrmann, H. J. (2012). Fluid depletion in shear bands. Physical review letters, 109 (24), 248001.

How to cite: Wang, X., Campmans, G., Weinhart, T., Thornton, A., Luding, S., and Wijnberg, K.: Exploring moisture-constrained aeolian sediment transport through a discrete particle modelling framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18979, https://doi.org/10.5194/egusphere-egu24-18979, 2024.

Fluvial sediment transport is an important component of the global sediment budget, yet in-situ monitoring is limited. Researchers and practitioners employ various methods to fill in these gaps, each with their own advantages and drawbacks. In this study, we compare four different models for estimating the total annual suspended solids and daily suspended sediment flux for the Sagavanirktok River in Alaska. These four models include: 1) in-situ turbidity calibration; 2) WBMsed global sediment flux estimates 3) optical remote sensing random forest model; and 4) Long-short term memory (LSTM) model trained on remote sensing and modeled inputs. We focus particularly on the summers of 2022 and 2023, when we have continuous validation data via a USGS discharge gage and turbidity sensors that we installed. We evaluate the accuracy, practicality, and shortcomings of each approach to reconstructing the total suspended sediment flux of the Sagavanirktok River. We highlight the necessity of high temporal resolution (approximately daily) for estimating suspended sediment flux in the Sag. River due to the frequency of high discharge events and variable hysteresis between discharge and sediment load. We find that, for the Sag. River, optical imagery alone does not have sufficient temporal resolution to estimate suspended sediment flux (due to orbit repeat and clouds), despite the accuracy of individual estimates. The geomorphic model, WBMsed, is not accurate enough for the unusual hydrology, but does produce daily estimates. Finally, the LSTM model shows promise in being able to bridge the temporal mismatch between satellite, in-situ, and modeled dataset. The LSTM can take advantage of daily discharge models, while incorporating the accuracy of optical satellite sediment models

How to cite: Langhorst, T., Andreadis, K., and Pavelsky, T.: Multi-Model Comparison of Suspended Sediment Flux in the Sagavanirktok River, Alaska. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20740, https://doi.org/10.5194/egusphere-egu24-20740, 2024.

The Albanian Dinarides represent the central segment of the Dinarides–Hellenides orogenic belt. The Albanian sector is strategically located at the boundary between continental subduction to the north and oceanic subduction to the south, making it an ideal setting to explore the interplay between surface and deep geological processes. Furthermore, modern seismicity (e.g. 1979, Mw 7.1 Montenegro, and 2019, Mw 6.4 Durres earthquakes) and geomorphic features indicate ongoing tectonic activity at least since the late Quaternary. In this study, we explore the landscape response to tectonics and climate by 1) conducting an extensive geomorphic analysis including knickpoint extraction, ksn and chi analysis, longitudinal river profile projection, and mapping of geomorphic features such as windgaps, river terraces, pediment surfaces and uplifted relict landscapes, and 2) estimating basin-wide denudation rates using cosmogenic nuclides.

Specifically, we collected river sediment samples from more than 20 rivers draining all tectonic units and we determined denudation rates using the classic in situ 10Be technique for catchments draining quartz-bearing lithologies, and the new meteoric 10Be/9Be technique in carbonate and ophiolite settings where quartz-poor lithologies predominate. In a few cases, we used both techniques on the same catchments for inter-method comparison. 

The geomorphic analysis highlights the presence of river terraces, non-lithological knickpoints, uplifted relict landscapes and wind gaps suggesting recent tectonic activity at both regional and local scales. This led to a reshaping of the river network with changes in the hydraulic connectivity with the regional sea level that altered the sediment transport directions. Furthermore, Quaternary climatic variations appear to play a crucial role in the erosive power of rivers and in controlling cycles of aggradation and incision.

Denudation rates show spatial variability, ranging from less than 0.3 mm/yr to 0.9 mm/yr in the south, where carbonate and siliciclastic predominate, to over 1 mm/yr in the central part of Albania, where siliciclastic rocks and ophiolites are widely exposed. Although the rates present a good correlation with geomorphic metrics (e.g., ksn and hillslope), the observed variability appears to be influenced by local tectonic processes associated with active normal faults and salt diapirism. Overall, the denudation rates obtained with the two Be techniques are consistent and align with published incision rates derived from river terrace dating, suggesting coupling between fluvial incision and hillslope processes over the last few thousands of years. The consistency between the two cosmogenic Be methods validates the high future potential of the meteoric 10Be technique in quantifying denudation rates in settings dominated by non-quartz lithologies.

How to cite: Bazzucchi, C., Crosetto, S., Wittmann, H., Ballato, P., Faccenna, C., Muceku, B., and Rossetti, F.: The morphotectonic evolution of the Albanian Dinarides: new insights from the application of in situ and meteoric Be cosmogenic nuclides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-433, https://doi.org/10.5194/egusphere-egu24-433, 2024.

Boulders are ubiquitous in bedrock river channels, moving only when the discharge and slope are large enough to transport them; as a result, large boulders in river channels may retard stream incision by blocking the erodible surface of the channel bed. This cover effect of boulders in stream channels has been demonstrated in models, but we lack field data to test it and understand how it varies with rock type and climate. We collected amalgamated stream boulder samples for in situ ¹⁰Be and ¹⁴C cosmogenic radionuclide analysis from catchments in humid-temperate, mediterranean, and semi-arid zones in the Chilean Coastal Cordillera. We present preliminary results, including new cosmogenic nuclide data from small (1-5 km²) main catchments in each climate zone and three very small (~0.05 km²) catchments in the semi-arid zone along with grain size analysis (Wolman pebble counts; >100 measurements per locality) for the catchments and adjacent hillslopes, and compare with published ¹⁰Be concentrations of stream sediment from van Dongen et al. (2019) and hillslope boulders from Lodes et al. (2023). The humid-temperate catchment has the lowest mean stream boulder ¹⁰Be concentrations (normalized to sea level high latitude production rates) at 0.52×10⁵ a g^-1, followed by the mediterranean (1.82×10⁵ a g^-1) and the semi-arid catchment (4.56×10⁵ a g^-1). We obtained a ¹⁴C concentration for one boulder sample in the humid-temperate zone so far, at 2.31×10⁵ a g^-1. In the main catchments of all three climate zones, stream sediment samples show a negative trend where larger sample grain sizes have lower ¹⁰Be concentrations, possibly due to increased erosion of the boulder surfaces or shielding due to overturning. Deposition by landslides can be ruled out in the humid and semi-arid catchments, but not in the mediterranean. In contrast, the three very small catchments in the semi-arid zone show a positive relationship between grain size and ¹⁰Be concentrations, suggesting that in these catchments, discharge and slope are too low to frequently overturn or erode the largest grains. In addition, in the semi-arid catchments boulders on hillslopes are larger and have higher ¹⁰Be concentrations than boulders in streams, whereas in the mediterranean catchment we observe the opposite pattern, suggesting that in the semi-arid catchments, the largest boulders may stay on the hillslopes until they have weathered to a size small enough to be transported to the stream channels. Next steps include analyzing ¹⁴C data for the remaining catchments and further analysis of boulder nuclide concentrations using a modelling approach.

How to cite: Lodes, E. and Scherler, D.: Cosmogenic signal of the stream boulder cover effect , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-545, https://doi.org/10.5194/egusphere-egu24-545, 2024.

Theory suggests that the response time of alluvial-channel systems to perturbations in climate can be related to the magnitude and direction of the forcing, and the length of the system; shorter systems may record a higher frequency of forcing compared to longer systems. The Toro Basin in the Eastern Cordillera of NW Argentina has preserved a suite of eight alluvial-fan deposits along the western flanks of the Sierra de Pascha. Farther downstream, a flight of cut-and-fill terraces have been linked to eccentricity-driven (100-kyr) climate cycles since ca. 500 ka. We applied cosmogenic radionuclide (¹⁰Be) exposure dating to the fan surfaces to explore (1) how channel responses to external perturbations may or may not propagate downstream, and (2) the differences in landscape response to forcing frequency as a function of channel length when comparing the upper basin alluvial fan deposits with the lower basin terrace sequence. Our new Toro ¹⁰Be dataset consisted of 30 boulder samples from the fan surfaces and five pebble samples from a fan depth profile. We identified two generations of fan surface; the first (G1) and second (G2) generations record surface activity and abandonment between ca. 800 and 500 ka, and within the last 100 kyr, respectively. G1 fans record a prolonged phase of net incision, which has been recognised throughout the Central Andes, and was likely triggered by prolonged and enhanced global glacial cycles following the Mid-Pleistocene Transition. Relative fan surface stability followed, while 100-kyr cut-and-fill cycles recorded by the fluvial terraces persisted downstream, suggesting a disconnect in behaviour between the two reaches. G2 fans record higher frequency climate forcing, possibly the result of precessional forcing of climate (ca. 21/40-kyr timescales). The lack of a high-frequency signal farther downstream provides field support for theoretical predictions of a filtering of high-frequency climate forcing with increasing channel length. We show that multiple climate periodicities can be preserved within the sedimentary record of a single basin. Differences in the timing of alluvial fan and fluvial terrace development in the Toro Basin appear to be associated with how channel length affects fluvial response times to climate forcing as well as local controls on net incision, such as tectonic deformation.

How to cite: Orr, E., Schildgen, T., Tofelde, S., and Wittmann-Oelze, H.: Landscape response to tectonic deformation and cyclic climate change since ca. 800 ka in the southern Central Andes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1456, https://doi.org/10.5194/egusphere-egu24-1456, 2024.

Droughts are amongst the most significant natural hazards in the central and southern Great Plains (USA). Chronologies of droughts and related dune activity phases in the Great Plains are paramount for understanding the frequency and magnitude of these potential risks. Beyond historical records, the timing and magnitude of droughts can be revealed only from sediment archives. Our joint DFG/SNF project, CONSTRAIN, aims to provide a new, accurate, and precise temporal placement of prehistoric droughts in the Great Plains, specifically the Nebraska Sand Hills, over the last 1,500 years. We combine methodological research (zircon luminescence dating, luminescence screening) with high-resolution quartz OSL dating to better understand the regional landscape dynamics. Our collaboration is currently in a pilot phase, performing the first methodological tests and identifying suitable archives for dating.

In our first field season, we sampled sand blowouts in the Nebraska Sand Hills identified from LiDAR data. These widespread crater-like depressions (Stubbendieck et al., 1989) are similar to modern blowouts but are grass-covered, suggesting they are likely prehistoric. Still, they remain poorly studied. The blowouts are deflation hollows that seem unrelated to anthropogenic activity or disturbance through wild animals. Instead, they likely formed from drought events that resulted in aeolian deflation on dune crests, but they were either of lower magnitude or shorter-lived than droughts that reactivated the dunes that last moved between 1,000 to 600 years ago (Mason et al., 2004; Miao et al., 2007; McKean et al., 2015).

Our contribution presents field luminescence screening results from 141 samples and the first optically stimulated luminescence (OSL) quartz ages derived from standard measurements testing the hypothesis that the naturally occurring blowouts are related to partial dune reactivation phases between 800 to 200 years ago.

References

Mason, J. A., Swinehart, J. B., Goble, R. J., and Loope, D. B.: Late-Holocene dune activity linked to hydrological drought, Nebraska Sand Hills, USA, The Holocene, 14, 209–217, https://doi.org/10.1191/0959683604hl677rp, 2004.

McKean, R. L. S., Goble, R. J., Mason, J. B., Swinehart, J. B., and Loope, D. B.: Temporal and spatial variability in dune reactivation across the Nebraska Sand Hills, USA, The Holocene, 25, 523–535, https://doi.org/10.1177/0959683614561889, 2015.

Miao, X., Mason, J. A., Swinehart, J. B., Loope, D. B., Hanson, P. R., Goble, R. J., and Liu, X.: A 10,000-year record of dune activity, dust storms, and severe drought in the central Great Plains, Geology, 35, 119–4, https://doi.org/10.1130/g23133a.1, 2007.

Stubbendieck, J., Flessner, T. R., and Weedon, R.: Blowouts in the Nebraska Sandhills: The Habitat of Penstemon haydenii, Proceedings of the North American Prairie Conferences, 223–225, 1989.

How to cite: Kreutzer, S., Schmidt, C., Kadereit, A., and Hanson, P.: Tracking dune blowouts to constrain prehistoric droughts in the Nebraska Sand Hills (Great Plains, USA), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1804, https://doi.org/10.5194/egusphere-egu24-1804, 2024.

The measurement of cosmogenic nuclide (CN) concentrations in riverine sediment has provided breakthroughs in our understanding of landscape evolution. Yet, linking this detrital CN signal and relief evolution is based on hypotheses that are not easy to verify in the field. Models can be used to explore the statistics of CN concentrations in sediment grains. In this work, we present a coupling between the landscape evolution model Cidre and a model of the CN concentration in distinct grains. These grains are exhumed and detached from the bedrock and then transported in the sediment to the catchment outlet with temporary burials and travel according to the erosion-deposition rates calculated spatially in Cidre. The concentrations of various CNs can be tracked in these grains. Because the CN concentrations are calculated in a limited number of grains, they provide an approximation of the whole CN flux. Therefore, this approach is limited by the number of grains that can be handled in a reasonable computing time. Conversely, it becomes possible to record part of the variability in the erosion-deposition processes by tracking the CN concentrations in distinct grains using a Lagrangian approach.  We illustrate the robustness and limitations of this approach by deriving the catchment-average erosion rates from the mean 10Be concentration of grains leaving a synthetic catchment, and comparing them to the erosion rates calculated from sediment flux, for different uplift scenarios. We show that the catchment-average erosion  rates are approximated to within 5% uncertainty in most of the cases with a limited number of grains. This model opens up new possibilities for studying sediment residence times in landscapes, assessing the effect of recycling in calculating paleo-erosion rates, and proposing new methods based on the combination of several isotopes.

How to cite: Carretier, S., Regard, V., Abdelhafiz, Y., Plazolles, B., and Vainer, S.: Modelling detrital cosmogenic nuclide concentrations during landscape evolution in the LEM CIDRE, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1850, https://doi.org/10.5194/egusphere-egu24-1850, 2024.

Burial dating with two cosmogenic nuclides (e.g. ²⁶Al and ¹⁰Be) is unveiling the last 5 million years of the sedimentary record. There is no dating method of comparable reliability for the fragmentary records typical of terrestrial settings. For the first time, we can explore events on the same timescale as mountain-building, we can reconstruct landscapes that predate the initiation of the northern hemisphere glaciations, and we can explore milestones in the evolution of our species. Here we focus on illustrating the latter: two field sites in which ¹⁰Be-²⁶Al burial dating has reshaped our understanding of early human dispersal in Eurasia. Both are well known Palaeolithic sites hosting Mode-1-type stone tools that despite being intensively studied have not been dated conclusively by other methods.

At Korolevo on the Tysa River in western Ukraine, alluvium containing stone tools is dated to 1.42 ± 0.10 Ma using the burial dating model, P-PINI (Particle-Pathway Inversion of Nuclide Inventories). Korolevo stands as the earliest securely dated hominin presence in Europe and bridges the spatial and temporal gap between the Caucasus (~1.85–1.78 Ma)and southwestern Europe (~1.2–1.1 Ma). Our findings advance the hypothesis of colonisation of Europe from the east well before the Middle Pleistocene Transition.

At Diring Yuriakh on the Lena River in eastern Siberia, stone tools are buried by aeolian sand sheets. We combine optically stimulated luminescence dating with the P-PINI burial dating model to yield an age of 417 ± 82 ka, which is at least 300 kyr earlier than the previously documented earliest human presence north of 60 degrees. This timing overlaps with exceptional warmth across the High North during the ‘super-interglacial’ MIS 11c (426–396 ka), suggesting that warm climate intervals permitted human migration well beyond widely accepted territorial bounds.

Reflecting on these advances, we evaluate the pros and cons of burial dating relative to other widely used dating approaches in archaeology and palaeoanthropology.

How to cite: Jansen, J. D., Knudsen, M. F., Garba, R., Andersen, J. L., Buylaert, J.-P., Kameník, J., Kurbanov, R. N., Lachner, J., Lukyanycheva, M., Margold, M., Murray, A. S., Nørgaard, J., Olsen, J., Rugel, G., Stübner, K., Usik, V., and Ylä-Mella, L.: Redrawing early human dispersal patterns with cosmogenic nuclides , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4168, https://doi.org/10.5194/egusphere-egu24-4168, 2024.

Cosmogenic ¹⁰Be/²⁶Al isochron burial dating is an effective way to accurately determine the depositional time of fluvial sediments that were shallowly buried without requiring any information on post-burial nuclide production and time-dependent burial history. The apparent differences in measured ¹⁰Be and ²⁶Al concentrations among a sample assemblage, which derives from the differential erosion in provenance, plays a crucial role in building the isochron. While, when the burial depth is too shallow and/or the amounts of post-burial produced nuclides constitute a main part of total nuclide inventories in samples, the concentration differences among samples would be overwhelmed by the analytical uncertainties of measured ¹⁰Be and ²⁶Al concentrations in samples, especially for the old sediments, and it thus leads to a large uncertainty in obtained burial age or destroys totally the isochron. As a result, in the situation of shallow outcrops, a compromise needs to be done between time consumption to dig few meters for sampling and the attainable dating precision. Furthermore, in the cases of shallowly deposited river terraces, especially in the southeastern margin of Tibetan Plateau where the surface erosion is fast and sediments preserved are commonly thin, there is no alternative deeper-buried sediments, and the dilemma between dating but without acceptable uncertainty and not dating has to face. Therefore, the question of how deep is deep enough has to be weighed when sampling. Here, we proposed that the sampling depth of sediments in isochron burial dating should be a flexible standard depending on the isochronicity of the sample assemblage, the predicted burial duration, local geomorphic conditions, and the probably analyzed uncertainties. We try to plot the correlation of predicted age uncertainties with sampling depth, burial ages, as well as the geomorphic parameters, to disambiguate the acceptable depth in the isochron dating for the required dating precision. 

How to cite: Ma, Y., Pang, J., and Zheng, D.: How deep is deep enough: disambiguating the acceptable depth for cosmogenic isochron burial dating, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4994, https://doi.org/10.5194/egusphere-egu24-4994, 2024.

The McMurdo Dry Valleys are an ice-free region along the coast of the Transantarctic Mountains that display well-preserved polar desert morphologic features, particularly at high elevations. The extent of these well-preserved features suggests that cold-desert conditions have been present for millions of years. This is thought to be because average summer air temperatures in much of the McMurdo Dry Valleys remain below -3ºC, preventing significant amounts of liquid water from forming and in turn keeping erosion rates low. Recent climate simulations suggest that these freezing temperatures persist during summer months at high elevations in the McMurdo Dry Valleys, even during past warm periods characterized by significant ice sheet recession. Surfaces at lower elevations in the McMurdo Dry Valleys, subject to warmer temperatures during warm periods and interglacials, are thought to experience overall faster erosion rates compared to high elevation outcrops.

Here, we examine the relationships between elevation, temperature, and apparent surface exposure age for outcrops of the Beacon Sandstone in the McMurdo Dry Valleys. We use a compilation of cosmogenic nuclide measurements available in the ICE-D database to evaluate the correlation between apparent surface exposure age and elevation for outcrops of the Beacon Sandstone across the McMurdo Dry Valleys. At or near a number of the cosmogenic nuclide sites, local summertime ground and air surface temperature data are available from weather stations. We use these weather station data to document how ground temperatures, which ultimately control the availability of liquid water and therefore rates of surface processes, correspond with the apparent exposure ages and site elevations of Beacon Sandstone outcrops. In addition, we investigate whether field observations indicating a relationship between the coloration and surface appearance of Beacon Sandstone outcrops and the surface weathering/erosion rate can be quantified using satellite remote sensing data and the spectral properties of the outcrops. Tying all of these results together, we assess the role of temperature and other physical parameters on the rates of surface processes in the McMurdo Dry Valleys during the last few million ice-free years.

How to cite: Bourikas, T., Tremblay, M., Lamp, J., Balco, G., and Granger, D.: Relationships between temperature, elevation, and surface exposure age in the McMurdo Dry Valleys, Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6385, https://doi.org/10.5194/egusphere-egu24-6385, 2024.

Dating glaciofluvial deposits is fundamental to reconstruct paleoglacial and paleoclimatic dynamics. However, partial bleaching and lack of suitable sediments make the application of luminescence dating to such deposits challenging. Single grain and cobble luminescence dating have been successfully used to tackle these problematics ^{[e.g. 1, 2]} and are combined in this study on glaciofluvial deposits from the northern Alpine foreland (Finsterhennen, Switzerland).

Previous chronological investigations at the study site ^{[3, 4, 5]} suggest that the deposition of the glaciofluvial gravel lying directly underneath the till from the regional Last Glacial Maximum (LGM) occurred ca. 29 kyr ago, in response to the LGM glacial advance. By comparison with the existing age constraints, the present study aims (1) to test the combined application of single grain and cobble luminescence dating to Alpine glaciofluvial deposits and (2) to refine the two methodologies.

Samples were collected from well sorted sand lenses and moderately sorted gravel at approximately the same depth within the pre-LGM glaciofluvial gravel. Single grain (SG) feldspar luminescence measurements were conducted on sand lens and gravel sandy matrix samples, while luminescence depth profiles were measured in individual crystalline cobbles. Preliminary results show good agreement between SG ages from the sand lens and previous chronological constraints. SG results from the sandy matrix of the gravel horizon are instead underestimated, potentially because of challenges in dosimetry estimation, due to the heterogeneous lithology and grain size of the gravel layer. Heterogeneous dosimetry appears less problematic for burial age estimation of cobbles, since the variation of dose rate with depth into the cobble is dominated by the dosimetry of the cobble itself. Preliminary cobble luminescence depth profiles show shallow bleaching fronts, with large variability between cores and surfaces of the same cobble. The limited luminescence signal resetting can be explained by the proximity of the glaciofluvial deposits to the advancing LGM ice front and by sediment transportation in turbid water. The intra cobble variability is instead potentially related to the cobbles’ heterogeneous lithology, implying differences in dosimetry and light attenuation within the clasts.

References

^[1] Duller, 2006, Quaternary Geochronology 1.

^[2] Jenkins et al., 2018, Quaternary Science Review 192.

^[3] Schlüchter, 2004, Quaternary Sciences 2.

^[4] Preusser et al., 2007, Boreas 36.

^[5] Pfander et al., 2022, Swiss Journal of Geosciences 115.

How to cite: Serra, E., Mueller, D., Gegg, L., and Preusser, F.: Combined application of single grain and cobble luminescence dating to Alpine glaciofluvial deposits, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7506, https://doi.org/10.5194/egusphere-egu24-7506, 2024.

Any keen observer has noticed that valleys show a large variability in their shapes: mountain rivers flow in valleys ranging from dramatic narrow gorges to valley floors that are several times river width. This geometry implies that the river has not only carved vertically but has also laterally eroded the valley flanks, depending on the action of lateral and vertical erosion on the flanks and valley floor respectively. Valley widening occurs when a river channel comes into contact with the valley edges and erode them, therefore, it depends on processes acting at the scale of a river bank but also at the scale of the river.

However, valley widening processes and rate are still poorly documented while valley evolution has a key role in landscape evolution. Lateral erosion during catastrophic floods can drive valley flank erosion. Valleys are also wetlands with a voluminous aquifer and where ecosystems evolve as valleys widen or narrow over millennia. Moreover, the storage of carbon increases in wide valleys which, therefore, play a role in the carbon cycle and in the evolution of the global climate. Valley width strongly affects sediment residence times on continents, with large valleys potentially buffering sediment fluxes exported to the oceans. Finally, valleys widening is responsible for the formation of abrasion terraces and contribute to the development of pediments. The dynamics of valley widening is therefore a fundamental component of the evolution of relief and sediment flux.

Given these challenges, it is becoming necessary to better understand valley widening rate and its controls. We have used and further developed the approach presented and tested in northern Chile by Zavala et al. (2021 doi:e2020GL0899).  For that, we focused on 13 river valleys (in the Arequipa Province, Peru, in the Atacama Desert in Chile and in the plateau of Valensole, France) where geomorphic, geological and climatological parameters offer a wide range of conditions to compare with erosion rates. In total, we analysed 79 samples of sands from valley flanks to measure the millennial erosion rates, by using in-situ produced Beryllium-10 (10-Be) and Aluminium-26 (26-Al). We used the detrital mean 10-Be concentration to calculate a mean local valley flank erosion rate, in a similar way that cosmogenic nuclide concentrations have been used to quantify catchment wide denudation rates.

We also extracted factors that may control widening rate (valley width, slope of flanks and valley floors, incision and drainage area) for comparison with 10-Be and 26-Al concentrations. Our preliminary results in 31 samples show comparable 10-Be concentrations along a single stretch of valley, except for several outliers, for different valleys in the Andes and France, indicating some robustness in the sampling method. These results are promising and should provide new constraints on factors that control the widening rate of valleys. 

How to cite: Valenti, C., Carretier, S., Regard, V., Choy, S., Godard, V., Christophoul, F., Viveen, W., Zavala, V., and Team, A.: Controls on flank erosion rates during valley widening: an application of cosmogenic nuclides in Andean and French valleys, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7571, https://doi.org/10.5194/egusphere-egu24-7571, 2024.

Along an extreme climate gradient from arid to humid in the Chilean Coastal Cordillera, we investigated soil profiles using the meteoric cosmogenic radionuclide ¹⁰Be and its ratio to stable ⁹Be. The isotope ratio ¹⁰Be(meteoric)/⁹Be combines an atmospheric flux tracer to Earth’s surface with stable ⁹Be that is released by weathering. In contrast to the well-established in situ ¹⁰Be method, the meteoric variety of ¹⁰Be is not limited to quartz-bearing lithologies and requires less sample material. However, to calculate denudation rates from ¹⁰Be(meteoric)/⁹Be knowing the depositional flux to Earth’s surface, F¹⁰Be_met, is an essential prerequisite.

We applied the in situ ¹⁰Be technique for denudation rate estimations on soil profiles (D_insitu) and compared the results with ¹⁰Be(meteoric)/⁹Be-derived denudation rates (D_met). Our results show that D_met in conjunction with F¹⁰Be_met derived from a general circulation (GCM) model (ECHAM5-HAM; Heikkilä, 2007) are consistent with D_insitu at the mediterranean (¹⁰Be_insitu: 126 ± 32 t km^-2 yr^-1, ¹⁰Be(meteoric)/⁹Be: 170 ± 40 t km^-2 yr^-1) and humid (¹⁰Be_insitu: 38 ± 10 t km^-2 yr^-1, ¹⁰Be(meteoric)/⁹Be: 31 ± 8 t km^-2 yr^-1) study sites, both with mean annual precipitation (MAP) > 400 mm (mediterranean: 440 mm yr^-1, humid: 1080 mm yr^-1). However, at the arid (MAP: 10 mm yr^-1) and semi-arid (MAP: 90 mm yr^-1) study sites, when using a GCM-based F¹⁰Be_met, D_met exceed D_insitu by a factor of up to 170. The cause for this offset may lie in an overestimation of F¹⁰Be_met at low precipitation. Indeed, when using D_insitu as benchmark and solving for F¹⁰Be_met instead, a much lower flux results.

These results suggest a lower precipitation limit (~400 mm yr^-1) for the use of GCM-derived F¹⁰Be_met especially in dry regions. In such arid and semi-arid regions with high spatial climate variability the depositional flux derived from coarse-resolution GCM-models overestimates the input of meteoric ¹⁰Be to Earth’s surface either by wet or dry deposition. In settings with sufficient precipitation above this limit the GCM-derived flux is suited to determine denudation rates using ¹⁰Be(meteoric)/⁹Be.

Heikkilä, U., 2007, Modeling of the atmospheric transport of the cosmogenic radionuclides ¹⁰Be and ⁷Be using the ECHAM5-HAM general circulation model: ETH Zurich, doi:10.3929/ETHZ-A-005560259.

How to cite: Krone, L., Wittmann, H., and von Blanckenburg, F.: Combining meteoric and in situ 10Be for depositional flux estimations along a climate gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7686, https://doi.org/10.5194/egusphere-egu24-7686, 2024.

Changes in climate coupled with long-term uplift cause alluvial rivers to aggrade or incise, resulting in the formation of fluvial terrace sequences. Such terrace records provide an opportunity to investigate past interactions between climatic forcings, tectonics, and fluvial systems. Further, they allow us to infer potential channel responses to future climatic change. To accurately decipher such interactions, precise age constraints on fluvial terraces are vital. However, established dating methods such as cosmogenic exposure dating are costly, time intensive, and require direct access to terrace surfaces. Thus, their application is not always possible.

An alternative approach to dating fluvial terraces is based on the temporal evolution of the step (riser) between successive terraces. Downslope sediment transport and elevation change, commonly modelled by hillslope diffusion equations, cause a decrease in gradient with time. If the profile of a riser is obtained in high resolution via GPS or LiDAR elevation measurements, its shape can be related back to the terrace age using inverse modelling schemes.

Here, we apply this theory to a set of fluvial terraces situated along the Río Santa Cruz and Río Shehuen in Patagonia, Argentina. A set of existing ¹⁰Be terrace exposure ages of up to ca. 1 Ma from both rivers is used for age verification and model calibration. GPS elevation transects of terrace risers measured during a field campaign in 2023 are used to establish an age chronology with negligible elevation uncertainties. To explore the feasibility of this method without access to field-quality elevation data, we also test the viability of using riser profiles derived from ca. 12 m resolution TanDEM-X data for dating. Preliminary results from synthetic riser profiles with elevation uncertainties similar to those of TanDEM-X data indicate that such DEM-derived age estimates are theoretically accurate. However, application to the Patagonian river systems and comparison against independent ¹⁰Be ages shows a wide spread in absolute age estimates for single terrace generations. Therefore, in this case, the method appears to be viable only for relative age classification. Post-abandonment riser disturbances and spatially variable sediment transport rates may be key factors hindering our ability to integrate large numbers of DEM-derived profiles into a unified interpretation. Obtaining more robust absolute age estimates may require the use of landscape evolution models that incorporate more complex, non-diffusive processes. Further, the viability of this method may be reduced for very old (i.e., ca. 1 Ma) terraces. Application to younger terrace systems may yield more accurate results.

This technique provides a low-cost, spatially extendable way of dating fluvial terraces and analysing landscape dynamics in fluvial systems. We are currently preparing to release an open-source Python library containing the tools needed to perform these analyses.

How to cite: Grimm, L., McNab, F., Fernandes, V. M., and Schildgen, T.: What can DEMs tell us about the ages of fluvial terraces?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9499, https://doi.org/10.5194/egusphere-egu24-9499, 2024.

Up until now, the cosmogenic radioisotope ³⁹Ar has not been used for surface exposure or burial dating of minerals due to its low concentration in rocks and the large sample size requirements for its detection by low-level counting. The novel analytical method Atom Trap Trace Analysis (ATTA) – already well established for gas samples from groundwater, ocean water or ice cores – can measure the isotopic ratio of ³⁹Ar to stable Ar in the range of 10^-16 on just a few ml STP of argon and therefore opens up new possibilities for applying ³⁹Ar.

This talk will report on the initial steps taken towards using ³⁹Ar as a geochronometer. Calculations of production rates of ³⁹Ar in typical continental rocks, exposed to cosmic radiation at the Earth surface, show that sample sizes of the order of 100 g of rock should yield a sufficient number of ³⁹Ar atoms (order 10³ to 10⁴) for detection by ATTA. However, the amount of ⁴⁰Ar in such samples – and therefore the total extractable Ar amount - is much lower than what is typically extracted from ice and water samples, which contain atmosphere-derived Ar. The ⁴⁰Ar content in rock stems from ⁴⁰K-decay and depends on the rock formation age and the potassium content. Dilution with ³⁹Ar-free Ar results in sufficient total argon volumes for the standard ATTA analysis.

Gas extractions from heated rock samples indeed show ³⁹Ar isotope abundances 2-3 orders of magnitude above the atmospheric ratio, well within the measurement range of ATTA after dilution. In order to check the feasibility of exposure dating of rocks, several samples were taken for comparison from boulders of glacier moraines, previously dated with ¹⁰Be, in the Jamtal valley in Austria. Additionally, ¹⁰Be-dated samples from other moraine sites are to be analysed for ³⁹Ar for further validation of ³⁹Ar as a tool for exposure dating. As of now it remains to be seen whether reliable agreement between the dating methods can be achieved. Due to its relatively short half-life of 268 years, ³⁹Ar would be a useful addition in multi-tracer studies on geologic processes within the last two millennia.  

How to cite: Neumann, F., Arck, Y., Gardner, W. P., Schaefer, J., Singhateh, M. L., Oberthaler, M., and Aeschbach, W.: Early development of Argon-39 as a new geochronometer for geologic processes on short time scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9605, https://doi.org/10.5194/egusphere-egu24-9605, 2024.

The landscape of Central and Northern Madagascar is characterized by residual landforms, steep slopes, and low-relief areas, resulting mainly from the processes of dissection of the central high plateau and retreat of two main topographic scarps on the western and eastern margins of the island. On the western side, the topography is characterized by relict relief and a highly sinuous plateau edge. Conversely, the landscape on the eastern side is dominated by the great topographic escarpment with a linear plateau edge. Locally, this general morphology is perturbed by the formation of the active Alaotra-Ankay rift system, which displaces the plateau-escarpment system. Here, we explore the long-term relief evolution of these three morpho-structural domains (west and east sides and rift sector) by combining denudation rates derived from cosmogenic nuclides and geomorphic stream profile analysis. Our results show that, although the erosional dynamics are dominated by the same processes of plateau dissection and scarp retreat, the topographic features, drainage networks, and distributions of species richness differ within these three domains. We provide insight into the processes that lead to transient landscape and relief evolution of rifted margins.

How to cite: Clementucci, R., Willett, S., Wang, Y., Datian, W., Haghipour, N., Randriamananjara, H., and Ranaivoson, N. T.: Long-term denudation and topographic relief evolution of Central and Northern Madagascar, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10522, https://doi.org/10.5194/egusphere-egu24-10522, 2024.

The authigenic ¹⁰Be/⁹Be dating method has emerged as a novel chronometer in the last few decades. Initially introduced by Bourles et al. (1989: Geochim. Cosmochim. Acta) for dating of oceanic sediments the method has been successfully applied to date continental sediments in some recent studies. The method utilizes decay of cosmogenic radionuclide ¹⁰Be to date the deposition of sediment in the range of 0.2 to ~14 Ma. Different source of the two isotopes ⁹Be and ¹⁰Be results in changes in the authigenic ¹⁰Be/⁹Be ratio (R) as the sediment gets transported from deltaic to offshore settings through shelfal environment. Accurate determination of initial ¹⁰Be/⁹Be ratio (R₀) is of paramount importance in this dating method to calculate the correct age of the deposited sediment. It is therefore necessary to quantify the variability of authigenic initial ratio for the effective application of the method.

This study aims to describe the variability of authigenic ¹⁰Be/⁹Be ratio in temporal as well as spatial scale. We analyzed the samples for authigenic ¹⁰Be/⁹Be ratio from two different study sites, the Late Miocene to Quaternary Slanicul de Buzau section in Romania and the Holocene Po River delta plain in Italy. 109 samples were sampled from Slanicul de Buzau section with a sampling step resolution of ~20–30 ka aiming to interpret ratio variability in temporal scale. Po coastal plain yielded 50 samples from 4 different parasequnces (5,6,7 and 8) (Amorosi et al., 2017: Mar. Pet. Geol.) to cover the variability in spatial scale. The analysis of samples from these study sites allowed us to understand the variability of the ratio in terms of sediment source proximity and change in sediment provenance.

Back calculation of initial ratio R₀ in 109 samples from Slanicul de Buzau section with the help of measured authigenic R and interpolated magnetostratigraphic age of samples reveals low variability in R₀ in deltaic and shallow water sediments, while the offshore facies exhibit significantly higher variability.

Results from measured ratio R in 50 samples of Po Plain does not show a drastic variability, slightly higher R in the samples from parasequence 6 can be attributed to the different provenance of this parasequence in contrast to the sediment source of the latter parasequences (Amorosi et al., 2020: Basin res.).

This observed low variability of authigenic ¹⁰Be/⁹Be reveals the good suitability of the dating method for river dominated deltas. We have also attempted to propose a minimum number of sample count necessary to be analyzed when using this dating method. The approach aims to estimate the sample size dependency of the ratio by running 1000 simulations and bootstrapping to estimate the 95% CI for variability of ratio, taking into consideration the three statistics namely, range, IQR, and SD. Bootstrapping performed in our data, in a particular group of n samples (e.g., samples from a specific facies type), suggests that at least nearly half the sample size of n is necessary to represent the initial ratio variability and to avoid the potential bias caused by the initial ratio variability.

How to cite: Aherwar, K., Šujan, M., Braucher, R., Chyba, A., De Leeuw, A., Matoshko, A., Amorosi, A., Campo, B., Rózsová, B., Lalinská-Voleková, B., and Team, A.: Variation of authigenic 10Be/9Be in spatial and temporal scale and its implications for applicability of dating method for river dominated deltas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10959, https://doi.org/10.5194/egusphere-egu24-10959, 2024.

Multiple elevated temperature infra-red stimulated luminescence (MET-IRSL) has great potential to provide detailed information on the movement of sediment grains through time and space. MET-IRSL stimulates grains using infra-red light at a series of elevated temperatures to access multiple charge populations with different bleaching behaviours. Length of past light exposure and duration of storage events can be determined by the relative difference between multiple signals, or ages, for a single grain. With more signals, we can see deeper into the history of an individual grain.

Single-grain measurements paint a fine-resolution picture of how a system operates, often masked by multiple grain average measurements. The power of single-grain measurement is underpinned by three basic principles: 1) A single grain has a single transport-storage history (Rhodes and Leathard, 2022), 2) Populations of >200 grains per sample allows for quantitative estimation of the most likely, or ‘dominant’ history for a given sample, 3) It is possible to isolate different grain populations, with different histories or provenance within a single sample.

Using samples collected from the active channel of the Allt Dubhaig in Scotland, we present results from a bleach recovery experiment to illustrate an optimal method for quantifying most likely length of past light exposure using single grains, and a gaussian mixture model approach to isolating different grain populations within a single sample. Combined with a numerical model of single-grain bleaching and burial, we apply these approaches to elucidate past and present fluvial sediment transport information for the Allt Dubhaig, Scotland, and the Santa Clara River, southern California.

How to cite: Spano, T., Rhodes, E., and Hodge, R.: Using single-grain multiple elevated temperature luminescence to understand fluvial sediment transport at the system scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11032, https://doi.org/10.5194/egusphere-egu24-11032, 2024.

Meteoric ¹⁰Be is a cosmogenic nuclide produced in the atmosphere and delivered to Earth’s surface by precipitation, whereas stable ⁹Be is a trace metal released from bedrock during weathering. The ratio (¹⁰Be(meteoric)/⁹Be) is set in the critical zone, where beryllium is either adsorbed to fine-grained sediment or is dissolved in water if the pH-dependent retentivity of Be is low. A prerequisite for calculating denudation and weathering rates over millennial timescales is knowledge of the flux of ¹⁰Be deposition to Earth surface and the concentration of ⁹Be in the unweathered parent bedrock. We provide a review of applications of the ¹⁰Be/⁹Be system to Earth surface studies that covers a variety of quartz-bearing rocks, lithologies largely void of quartz like mafic rocks, mixed lithologies, and, most recently, carbonate and marble lithologies.

We show the versatility of this new approach in several case studies. These range from small creek-scale mafic basins in the European midlands, medium-sized (10²-10³ km²) catchments covered by slate and marble in the rapidly eroding Taiwan Island, pure carbonate rocks from the French Jura Mountains, to large catchments draining mixed lithologies in the Chilean Andean Cordillera and the Amazon and Ganga river basins. We find that i) across all spatial scales, the dissolved and sediment-bound ¹⁰Be/⁹Be ratios agree well, indicating equilibrium of phases. Approximately at medium-sized catchment scales, ii) the ⁹Be concentration from published databases from typical parent rocks (http://earthref.org/GERM) represents the local bedrock ⁹Be concentration, but for much smaller and carbonate catchments, a locally representative bedrock concentration has to be determined on a case-by-case basis; and iii) local measurements of the depositional ¹⁰Be flux from the ¹⁰Be inventory of independently-dated deposits like e.g. terrace profiles appear to yield the most reliable estimates. Under these constraints, derived denudation and weathering rates agree in all settings to within less than a factor of 2 with either decadal-scale denudation rates from combined suspended and dissolved river fluxes or with in situ-¹⁰Be-derived denudation rates where quartz is present. This close agreement shows that ¹⁰Be/⁹Be ratios from such rock types yield meaningful denudation rates obtained from sub gram-sized amounts of sediment, independent of the spatial scale of sampling ranging from a single soil profile to the scale of the Amazon river basin. Small sample amounts and the independence of the presence of quartz provide a benefit over the “sister” nuclide in situ ¹⁰Be that has been widely used in landscapes of felsic rocks. Now, with ¹⁰Be/⁹Be, the determination of rates of Earth surface change in quartz-poor lithologies opens up entirely new opportunities.

How to cite: Wittmann, H., Bouchez, J., Deng, K., Gaviria-Lugo, N., Bernhardt, A., and von Blanckenburg, F.: Denudation and weathering rates from meteoric 10Be/9Be: A versatile tool in mafic, carbonate or slate-dominated lithologies from the critical zone to very large catchments , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11084, https://doi.org/10.5194/egusphere-egu24-11084, 2024.

Cosmogenic nuclide burial dating exploits the differential decay rate of a nuclide pair, typically ²⁶Al and ¹⁰Be. There are three basic approaches; simple burial dating, the isochron method and P-PINI (Particle Pathway Inversion of Nuclide Inventories). The simple burial age is based on deviation from the surface production ratio assuming quick and deep burial. The isochron method incorporates multiple samples from a single stratigraphic layer and assumes steady erosion in the sediment source area. P-PINI accommodates more complicated situations, such as landscapes undergoing non-steady erosion and an eroding or accumulating sink zone. This source-to-sink model uses a Monte Carlo simulator to create a library of plausible erosional and depositional histories and then compares those histories against measured nuclide data to derive a burial age estimate. In cases involving multiple dated layers in a section or when an independent age estimate is available, a Bayesian tool further constrains the burial age.

With the aim of constraining the timing of the Eurasian Ice Sheet at its largest known extent, we applied P-PINI at Wapenveld in the Netherlands and at Szczerców in central Poland. From a drill-core at Wapenveld we collected three sand samples from the Early Pleistocene ‘Hattem’ beds, and derived the P-PINI burial age bracketed by simple burial ages calculated from the units above and below. Szczerców is an open-cast mine exposing multiple Middle Pleistocene till units rich in cobble-sized clasts. Here, P-PINI burial ages show sensitivity to the thickness of the dated layer, a problem we resolve by including feldspar infrared-simulated luminescence dates higher up the sequence.

We discuss the pros and cons of our approach at Wapenveld and Szczerców. Burial dating multiple units in section requires considerably more lab effort but also offers important advantages that can be boosted by carefully considering which grain-size to sample, and by incorporating independent age constraints.

How to cite: Ylä-Mella, L., Wagner, K., Margold, M., Knudsen, M. F., Busschers, F., Bakker, M., Wachecka-Kotkowska, L., Krzyszkowski, D., Wieczorek, D., Szuman-Kalita, I., Eriksen, B. L., Andersen, J. L., Olsen, J., Perić, Z., Alexanderson, H., and Jansen, J. D.: Unveiling the early Eurasian glaciations with new advances of 10Be-26Al burial dating, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11574, https://doi.org/10.5194/egusphere-egu24-11574, 2024.

Rates and patterns of erosion by glaciers and their contribution to the evolution of tectonically active mountain topographies remain poorly understood. Insights from apatite fission track and (U-Th)/He thermochronometry have been restricted by minimum detectable cooling ages measured in millions of years that are relevant to the exhumation of bedrock from depths of upwards of c. 2 km, whilst cosmogenic nuclide concentration methods reveal the timing of removal of only the uppermost 2 m of bedrock, which is relatively superficial in glacial erosion terms. We have therefore applied the relatively new technique of K-feldspar thermoluminescence thermochronometry (Brown & Rhodes, 2022) that is capable of resolving near-surface cooling histories of bedrock over timescales spanning the most recent glacial-interglacial cycle. This very low-temperature thermochronometer permits analysis of exhumation from depths of several hundred metres upwards and is therefore sensitive to the erosion processes of specific components of the glacier system as well as the dynamism and significance of major erosional landforms. Results are presented from two currently glaciated valleys in the central European Alps that possess contrasting features and longitudinal valley profiles, and these suggest the ability to better understand glacial process contributions to mountain geomorphic development and to improve glacial erosion laws commonly used in numerical landscape evolution models. 

How to cite: Wenban, W. J., Brown, N. D., Rhodes, E. J., and Swift, D. A.: Constraining erosion rates and patterns for glaciated basins in the European Alps using thermoluminescence thermochronology , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12081, https://doi.org/10.5194/egusphere-egu24-12081, 2024.

Luminescence and radiocarbon dating methods are mandatory to set up reliable chronological frameworks for sedimentary systems to reconstruct climate and environmental changes quantitatively through time. Our study area, the Basin of the Great Lakes in Western Mongolia is a key area to investigate sediment archives and sediment pathways under variable climates in this region including extreme continental climatic conditions.  Alluvial fans, beach bars and dune fields, partly interacting with each other, were sampled for luminescence dating in detail. In this study, a total of thirty-four samples were taken from a beach ridge sequence of Khyargas Nuur and tested using K-feldspar single aliquot (2.5 mm) pIRIR dating to overcome the problem of the dim signal of quartz. Furthermore, single grain dating was also conducted to address the problem of insufficient bleaching of the pIRIR signals. The preliminary established chronological framework indicates that the studied samples were mostly deposited during the Holocene and the results yielded a continuous decline of the lake level for most of the Holocene period.

How to cite: Frechen, M., Rahimzadeh, N., Wolf, D., and Lehmkuhl, F.: Sediment Dating of Fluvial, Lacustrine and Aeolian Systems in the Basin of the great Lakes, Western Mongolia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12491, https://doi.org/10.5194/egusphere-egu24-12491, 2024.

Measurement of multiple cosmogenic nuclides in single samples is valuable for various applications. For exposure dating, multiple-nuclide systematics are important for correcting exposure ages for surface weathering and erosion, as well as quantifying when and how often a surface has experienced burial. Currently, such constraints from paired ²⁶Al/¹⁰Be/²¹Ne measurements in quartz are common practice and well established. However, ³⁶Cl/¹⁰Be/³He nuclide measurements in pyroxene would provide more precise constraints because the range in decay constants is greater. In Antarctica, the pyroxene-bearing Ferrar Dolerite is one of the dominant lithologies of clast exposed at the surface of many surficial deposits throughout the Transantarctic Mountains. While cosmogenic ³He measurements in Ferrar pyroxene are routine, ¹⁰Be and ³⁶Cl measurements are less common and not well established. Here we present recent advances in multiple cosmogenic nuclides measured in the Ferrar pyroxene, which includes (i) improvements in the extraction of ¹⁰Be and ³He from pyroxene grains, (i) production rate estimates of ¹⁰Be in pyroxene and ³⁶Cl from Ca spallation, and (iii) understanding and quantifying the non-cosmogenic inventories of ³He and ³⁶Cl in pyroxene for accurate exposure dating.

How to cite: Bergelin, M. and Balco, G.: Advances in Cosmogenic Nuclides measured in Ferrar Pyroxene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13590, https://doi.org/10.5194/egusphere-egu24-13590, 2024.

Dating alluvial-fan or river-terrace surfaces that are more than several tens of kyr old is challenging in many environments. Depth profiles of samples can be difficult to extract in the field, time consuming to process in the lab, and expensive to analyze. Even under idealized sampling conditions, the difficulty of constraining possible surface erosion or inflation can lead to large uncertainties in the surface exposure age. Alternatively, sampling individual boulder surfaces or cobbles may be logistically simpler, but large scatter in ages can be difficult to explain, given the possibility that the boulders/cobbles have rotated from their original position, surfaces experienced erosion, or the clasts may have some inherited concentration of cosmogenic nuclides. All of these problems are exacerbated in surfaces that have been exposed for hundreds of kyr.

In the Toro Basin of NW Argentina, a set of alluvial-fan surfaces has recently been interpreted to comprise two generations, one likely spanning from ca. 500 to 800 ka, and another less than 100 ka, based on ¹⁰Be exposure ages of individual boulder surfaces and one depth profile. Here, we report ²¹Ne data from a subset of the boulder surfaces with the aim of better constraining the ages.

Despite the apparently simple geomorphic setting of the fans, dual-nuclide (“banana”) plots of ²¹Ne and ¹⁰Be data reveal that most of the boulders have a complex burial history, with inferred burial times up to ca. 750 kyr. This finding implies that the boulders were not simply transported from nearby bedrock hillslopes and exposed on the fan surfaces. Instead, the boulders must represent exhumed rocks from an earlier generation of basin filling, which is constrained to between 4.5 and 0.85 Ma in the vicinity of the fans from U-Pb zircon dating of intercalated ashes (Pingel et al., 2020). We use a Monte Carlo approach to explore what possible range of initial exposure times, burial times, and final exposure times are consistent with the ¹⁰Be and ²¹Ne data on any given surface. For several surfaces, parameters trade off such that a wide range of exposure ages is possible. However, if we also take into account the stratigraphic relationships among the surfaces (higher surfaces must be older), and we consider that boulders exposed in the highest surface must have burial times that are shorter than boulders exhumed from lower elevations, relatively tight constraints on exposure ages, inherited nuclide concentrations, and boulder-surface erosion rates are possible on some of the surfaces.

How to cite: Schildgen, T., Orr, E., and Niedermann, S.: Refining exposure-age estimates of 40- to 800-ka surfaces with 10Be, 21Ne, and additional geologic constraints, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14778, https://doi.org/10.5194/egusphere-egu24-14778, 2024.

Rapidly eroding mountain ranges act as major sources for the export of clastic sediments, solutes and organic matter from the continents to the oceans, and thereby affect the global climate via the sequestration of atmospheric CO₂ into geological reservoirs. At the same time, mountainous landscapes experienced Quaternary variations in climate and vegetation – including the waxing and waning of glacial ice masses – and were therefore exposed to temporally varying erosional regimes. In the specific case of soil-mantled hillslopes, changing environmental conditions (e.g., temperature, precipitation) along with spatially variable topographic parameters (e.g., slope, aspect) are expected to modify the geomorphic processes responsible for the mobilization and downslope movement of soil material, such that soil erosion might represent a function of both space and time. Furthermore, transient soil erosion is likely coupled to alterations of the soil thickness and hence to changes in the production of soil material from the underlying bedrock. In this study, we investigate the spatio-temporal variability of soil production and erosion on different soil-covered alpine landforms within the Goms area (Switzerland), based on paired measurements of the in situ ¹⁴C and ¹⁰Be concentrations within quartz separates of saprolite (n=12) and till-derived (n=2) samples. The short half-life of ¹⁴C compared to ¹⁰Be provides this approach with a unique sensitivity for short-term changes of soil production and/or soil thickness on Lateglacial to Holocene time scales. For multiple sites, the apparent soil production rates and exposure ages calculated from the cosmogenic nuclide concentrations reveal a constant exposure of the saprolite-soil interface, without any (detectable) signs of soil production or changes to the thickness of the overlying soil column since the Early to Mid-Holocene. The absence of soil production in combination with a constant vertical extent of the soils further implies that the erosional downslope transport of soil material is inactive at these locations, despite their generally steep slope angles (10 to 38°). Remarkably, the estimated exposure ages also differentiate between relatively young samples (¹⁰Be: 5.5 to 7.8 ka; ¹⁴C: 5.4 to 7.9 ka) from tributary hillslopes and older samples (¹⁰Be: 10.2 to 12.0 ka; ¹⁴C: 9.6 to 12.7 ka) from the hillslopes of the main valley and erosional ridges, which represent important landforms within the investigated landscape. Additional results from Markov chain Monte Carlo inversion modelling indicate the potential occurrence of instantaneous losses of the soil cover (9.3 to 14.7 m at 7.6 to 8.7 ka) or the step-like decline of soil production rates (11- to 12-fold at 12.4 to 13.1 ka) for most of the remaining samples. Overall, these observations demonstrate the co-occurrence of ‘static’ sites without active soil production and erosion and more ‘dynamic’ sites characterized by transient, non-zero soil production and erosion rates, attesting to the spatial variability of hillslope soil dynamics between an active and an inactive state.

How to cite: Wartenweiler, S. H., Lupker, M., Haghipour, N., Christl, M., and Eglinton, T. I.: Hillslopes in action? Combining in situ 14C- and 10Be-derived insights into the spatio-temporal variability of soil dynamics on Swiss alpine hillslopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15601, https://doi.org/10.5194/egusphere-egu24-15601, 2024.

Improving our understanding of the timing, rates and distribution of erosion across mountains and valleys plays a key part in resolving longstanding debates on how landscape dynamics are influenced by the interactions between climate, tectonics and erosion. In particular, the onset of glaciations and more variable climate in the Pliocene-Quaternary have been invoked to explain the observed global increase in erosion rates, arguing that glaciers are more efficient at eroding bedrock than rivers. But questions about the temporal and spatial impact of glacial erosion and potential feedback remain. To contribute to resolving this debate, we conducted a local-scale thermochronological study in the Tauern Window, Eastern European Alps, with the aim to compare our findings to patterns in the wider region and the Western Alps. The Tauern Window presents an ideal natural laboratory to isolate these interdependent effects due to its well constrained tectonic history of rapid uplift until ∼8 Ma. Comparatively, the western Alps have experienced similar glaciation but a different tectonic history, and show significantly higher geodetic uplift rates and millennial-timescale erosion rates. Thus, an East-West comparison could help shed light on the dominant controls on the laterally variable Alpine morphology.

Here, we present new apatite (U-Th)/He (AHe) data distributed along elevation profiles through several glacial valleys: the Italian Ahrntal and the Austrian Floitental, Krimmler Achental and Windbachtal. The low closure temperature of the AHe system is sufficiently sensitive to enable correlating recorded exhumation/denudation to surface processes and landscape-shaping dynamics, and allows us to examine the late-Cenozoic thermal history of the area. AHe dates range from ~3.4 to 12.5 Ma; the youngest dates are thus time congruent with the onset of glaciation.

Our data indicate variations in erosion rates with elevation down these valleys, which we suggest can be attributed to altitude-dependent glacial erosion intensity. These patterns are compared to a hypsometric analysis of the Eastern Alps, to determine possible links between observed denudation over the last few million years and present-day markers of glacially reshaped topography. This study also provides initial insight into the best suited locations for a future higher-resolution investigation using ⁴He/³He thermochronometry, which promises to be able to resolve the area’s denudation history into the Quaternary and allow for a more direct comparison to modern hypsometry. These findings will also inform a future focused investigation into landscape-shaping couplings discernible from thermochronological data used alongside landscape analysis via thermal-kinematic modelling in PecubeGUI.

How to cite: Wapenhans, I., van der Beek, P., Bernard, M., Colleps, C., and Amalberti, J.: Reconciling late Cenozoic spatio-temporal patterns of Alpine topographic changes from low-temperature thermochronology and glacial morphometric signatures , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16703, https://doi.org/10.5194/egusphere-egu24-16703, 2024.

The western European Alps are characterised by deeply incised valleys, however the timing of their formation and the impact of Quaternary glaciation on rates of erosion remains disputed. This is mainly due to a lack of geochronological methods that cover the timespan of 10³-10⁶ years. Electron spin resonance (ESR) thermochronometry has a high potential to fill this temporal gap because of its low closure temperature (<100 °C), potentially allowing changes in erosion rates to be related to glacial advance and retreat. The Rhône Valley (Switzerland) was intensively glaciated during the Quaternary [1] while it is unclear how tributary valleys incised throughout the glaciation period. In this study, we focus on two study sites along the main valley, close to Sion and Visp and the Matter and Vispa river tributary valleys, towards Zermatt and Saas-Fee to compare their Quaternary exhumation histories.  Whilst bedrock samples from Sion yielded cooling ages between 209 and 674 ka, samples from Visp showed saturation around 2500 ka. Thermal stability varied between samples and signals, and sample measurement is ongoing. Preliminary inversion of the data shows that the low closure temperatures of the ESR signals in quartz allow the Late Quaternary exhumation of the Alpine valleys to be resolved, providing new insights into the glacial incision history during the Quaternary and especially how erosion rates varied temporally under a changing climate.

Reference:

[1] Valla, P.G., D.L. Shuster, and P.A. van der Beek. 2011. Significant increase in relief of the European Alps during mid-Pleistocene glaciations, Nature Geoscience. 4(10): p. 688-692.

How to cite: Wen, X., Bartz, M., Schmidt, C., and King, G.: ­­­­­ESR-thermochronometry in the western European Alps (Switzerland) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17371, https://doi.org/10.5194/egusphere-egu24-17371, 2024.

The Rhenish/Ardenne Massif (RAM) spreads across parts of Belgium, France, Germany and Luxemburg; it is one of the largest (>40,000 km²) and most “emblematic” Variscan structures located north of the Alps (think of the “Romantic Rhine”). Intraplate uplift affected the RAM during the Plio-Quaternary along with other Palaeozoic massifs located in the alpine foreland. However, its cause(s), shape and rates are still poorly understood and therefore remain debated (e.g., Demoulin & Hallot, 2009). This was, until recently, mainly due to a lack of reliable ages for uplift markers, such as the Quaternary terrace staircases along deeply incised valleys of the Rhine, Moselle and Meuse as well as their main intra-massif tributaries. Several studies based on numerical dating methods (i.e., in situ cosmogenic nuclides, electron spin resonance, luminescence…) have shed new light on these questions by assigning numerical age estimates on key levels of fluvial terraces (e.g., the so-called main terraces; Rixhon et al., 2011; Cordier et al., 2012) or cave levels related to phases of regional base-level stability (Rixhon et al., 2020).

This contribution first compiles all chronological data produced over the last twenty years and critically assesses their reliability to infer massif-scale spatio-temporal patterns of river incision. Plio-Quaternary incision rates are accordingly reconstructed. A similar trend of increase is reported throughout the RAM with a peak of incision occurring during the Early or Middle Pleistocene and matching the massif-wide geomorphological marker materialised by the main terraces (and associated cave levels if any). However – and importantly – age control reveals a significant time lag (>250 ka) between the south-eastern and north-western RAM margins. The high incision rates onset is consistently older along the Rhine/Moselle and tributaries (e.g., the Sarre) than along the Meuse and tributaries (e.g., Ourthe). This key finding is well in line with Demoulin and Hallot’s (2009) hypothesis arguing for a wave of uplift migrating northward throughout the RAM. It also supports regional tectonic causes for uplift (i.e., late, upper-crustal stress transfer from the Alps to their foreland) rather than more local ones (i.e., mantle plume below the Eifel Massif). Age constraints along the river valleys draining the easternmost part of the RAM – so far absent – along with a global geodynamic modelling will represent further steps to better understand the evolution of the uplift history.

References:

Cordier S. et al., 2012. Geomorphology, 165-166, 91-106.

Demoulin, A., Hallot, E. 2009. Tectonophysics, 474, 696-708.

Rixhon, G., et al. 2011. Quaternary Geochronology, 6, 273-284.

Rixhon, G. et al. 2020. Geomorphology, 371, 107424.

How to cite: Rixhon, G.: From spatio-temporal patterns of river incision rates to Quaternary uplift history of the Variscan Rhenish/Ardenne Massif (N Europe), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17402, https://doi.org/10.5194/egusphere-egu24-17402, 2024.

Turbidites are underwater land sliding events that correspond to the most distal part of the source-to-sink system. They can be triggered by a number of processes including flood events, storms, earthquakes or simply destabilization of a continental slope and are a vector of terrestrial sediments to deep depocenters. Marine sedimentary cores recording turbidites represent key sedimentary archives and can be used to track back the occurrence of such land and sea processes giving information on terrestrial paleo conditions.

Unfortunately, it is often difficult to assess which process initiated turbidites in particular because these are usually poorly dated. In most studies, turbidites are considered as instantaneous events and dated using foraminifera of the over and underlying hemipelagic layers. In this study, we bring new light on the age of the material remobilized by turbidites. To do so, we use ¹⁴C to date 20 samples of foraminifera and 38 samples of vegetal debris contained in two turbidites from two different cores of the Ogooué turbiditic system in western Africa. We have also dated foraminifera in the hemipelagic layers above and under these turbidites. The radiocarbon ages measured in the turbidites, when compared to the depositional ages of under- and overlying hemipelagic layers constrain the total transportation time from the source to the turbidite deposition, including both the duration of transport on land, and the potential storage of the sediments onshore and offshore (on the continental margin).

Our results shed new light on the transport and residence time of sediments in the Ogooué drainage system which is under 15 ka, on the residence time of sediments on the continental slopes or margins which is of about 3 ka, and on the depositional sequences and mechanisms of turbidites in said system. In a broader sense, it allows a better understanding of the mechanisms controlling turbidite deposition and its intrinsic timings. 

How to cite: Large, E., Hage, S., Dennielou, B., Charreau, J., and Blard, P.-H.: Age of deposition versus age of remobilized sediments in turbidites and implication for the duration of transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20370, https://doi.org/10.5194/egusphere-egu24-20370, 2024.

Peat erosion and degradation contribute to 2-6% of total global emissions of carbon each year. Wind erosion of bare peat surfaces, is a significant component of erosion. However, how rapidly-changing bare peat surface aerodynamic properties affect erosion processes have not been fully quantified. This study investigates how the spatial and temporal characteristics of peatland wind erosion are controlled by the aerodynamic properties of the bare peat surface. Field measurements of local meteorology, peat surface properties and peat flux from a 3-ha bare area of upland blanket peat (North Pennines, UK), have been analysed during a sustained period of strong winds and rainfall (November to April 2023). Results demonstrate that the eroded peat flux is correlated with the southwest prevailing wind direction and as velocity increases, the flux becomes more focussed to the southwest (225°). Windward-facing peat fluxes are 4-9 times higher than those in the leeward direction. The vertical wind velocity profile over the bare peat shows a logarithmic pattern with height which is mirrored in the peat flux profile. Average friction velocity is only partially correlated to the peat flux during the strongest wind events suggesting that peat surface aerodynamic characteristics (roughness) also affect the pattern and magnitude of eroded peat flux. To investigate this hypothesis in greater detail wind tunnel experiments with a 3-D printed 1:1 rough peat surface model (0.5 x 0.7 m, average geometric roughness height 0.0345 m) in a large recirculating wind tunnel (2 x 0.6 x 0.6 m) are conducted to acquire the wind velocity profile over the peat boundary surface at 12 carefully selected characteristic locations. Experiments are conducted under free stream wind velocities at 2, 4, 6, 8, 10 m s^-1 which are representative to the wind velocities observed in the field. Velocity measurements are taken by traversing a 5-hole probe in a normal direction with a spatial resolution of 2 mm within the boundary layer. Velocity signals are sampled at 500 Hz over 12 seconds at each sampling location. Flow properties including time-mean velocity, turbulence kinetic energy and wall shear stresses over the rough peat surface are analysed. These provide details of the wind flow field over the peat microtopography and allow us to investigate spatially and temporally resolved airflow dynamics. Further work using numerical modelling is planned to test the field observations and wind tunnel experiments and define in detail how surface roughness influences erosion of bare peat.

How to cite: Zang, Y., Warburton, J., Gan, L., and Hardy, R.: Quantifying the Importance of Wind Erosion of Bare Peat: Initial Insights from Field Measurements and Wind Tunnel Modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1085, https://doi.org/10.5194/egusphere-egu24-1085, 2024.

Investigating the stability of river bedforms is essential for understanding their occurrence and evolution over time. Whereas the formation of ripples and dunes has been extensively studied [1, 2], little is known about antidune stability in the early stages. Our research aims to fill this gap by focusing on antidune incipience in gravel-bed streams under low submergence conditions. Based on Vesipa et al. (2014), who distinguished between convective and absolute instabilities of bedforms [3], we investigated the behavior of the antidunes in the early stages of their formation. We conducted experiments in a narrow flume and studied how key flow factors (e.g., the Froude number, relative submergence, and initial perturbation) affect antidune dynamics. By filming the bed evolution from the sidewall, we determined the antidune wavelength and amplitude as a function of space and time in order to provide empirical insights that complement the theoretical framework.

[1] Colombini, M., and Stocchino, A. (2011). Ripple and dune formation in rivers. Journal of Fluid Mechanics, 673, pp. 121-131.

[2] Fourrière, A., Claudin, P., and Andreotti, B. (2010). Bedforms in a turbulent stream: formation of ripples by primary linear instability and of dunes by nonlinear pattern coarsening. Journal of Fluid Mechanics, 649, pp. 287-328.

[3] Vesipa, R., Camporeale, C., Ridolfi, L., and Chomaz, J. M. (2014). On the convective-absolute nature of river bedform instabilities. Physics of Fluids, 26, 124104

How to cite: Farazande, S., Pascal, I., and Ancey, C.: Instability of Antidune Incipience under Low Submergence Conditions , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3160, https://doi.org/10.5194/egusphere-egu24-3160, 2024.

Debris flows are classical two-phase flows that can be enhanced by entraining multi-grain sizes of sediments from the bed as they rush down steep slopes, in which particle segregation is related to assessing the potential hazards. However, understanding the characteristics and fluid-particle interaction mechanisms remains challenging. Here an existing depth-averaged two-phase continuum flow model is further improved by incorporating the effects of pore-fluid pressure and bed sediment conditions on erosion. To demonstrate its reliability, we compare numerical solutions with measurements of thickness, front location, and bed deformation in two sets of USGS large-scale experimental debris flows over erodible beds. The following physical understandings are obtained. First, the positive effects of pore-fluid pressure and coarse bed materials on erosion rates are numerically reproduced. Moreover, an additional mechanism for this phenomenon has been revealed. Specifically, debris flows on steep slopes are likely to fall into a high shear stress regime, under which conditions the sediment transport capacity always takes a maximum value and is independent of the sediment size. Therefore, the sediment settling velocity that is proportional to the sediment size affects the erosion rate directly. Second, we probe into the non-dimension number and energetics of the debris flows to find it necessary to incorporate water-sediment and particle-particle interactions into reproducing the debris flow processes. Third, two kinds of mechanisms for particle size coarsening in the head region of the debris flow are resolved: on the one hand, they can be incorporated and retained there if the debris flow acquires sediment from the bed in transit due to considering the hiding/exposure mechanisms and on the other hand, they can migrate to the head by preferential transport. Furthermore, a series of idealized tests were conducted to explore the factors contributing to the segregation of particles within a debris flow. The longitudinal particle segregation was reproduced by incorporating the shear-induced non-uniform vertical distributions of velocity and sediment concentrations, the visco-inertial rheology, as well as the grain-size heterogeneity into the modelling. Sensitive analysis shows that the transport of fine particles is more inhibited by the interaction of the flow, contributing to the larger transportation velocity of the coarse particle. We further observed that the water content, the slope, and the particle size would have positive effects on the longitudinal size segregation in the head region, contrasting with the negative effects of the flow viscosity. These factors affecting the segregation ratio are attributed to the changes in the ratio of the Reynolds Number of the flow between fine and coarse particle.

How to cite: Hu, P., Lyu, B., Li, J., Li, W., and Cao, Z.: Numerical investigation about propagation characteristics and hydro-sediment-morphodynamic interactions of multi-sized debris flow with a two-phase continuum model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4798, https://doi.org/10.5194/egusphere-egu24-4798, 2024.

The laboratory experiments on the intense transport of bimodal sediment were conducted in a tilted, glass-sided flume with a variable longitudinal slope. Two fractions of lightweight solids were used, primarily differing in particle size, and each had a distinct color. The observed solid-liquid flow exhibited characteristics of being steady, uniform, turbulent, and supercritical. The bimodal sediment was transported as a combined load, with the finer fraction primarily supported by carrier turbulence, and the coarser fraction supported by interparticle contacts in the transport layer above a plane surface of the bimodal stationary bed. Distributions of solids velocity and concentration were measured for each of the two fractions across the transport layer above the bed using optical methods employing high-speed cameras. Additionally, the distribution of carrier velocity was measured across the flow depth. The measurements revealed a non-uniform distribution of solids for both fractions, with the maximum concentrations at the top of the bed for the coarser fraction and within the transport layer for the finer fraction at the highest bed shear. The results of the measurements allowed for the identification of the degree of stratification in the high-concentration sediment-laden flow and facilitated the evaluation of the interaction between particles of different fractions in the transport layer at various elevations above the bed. Furthermore, they enabled the quantification of the proportion of particles of the two fractions in the total discharge of solids through the channel.

How to cite: Matousek, V., Krupicka, J., Picek, T., and Svoboda, L.: Measured distributions of velocity and concentration for intense transport of bimodal lightweight sediment in tilting flume, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6100, https://doi.org/10.5194/egusphere-egu24-6100, 2024.

Consecutive floods combined with hyperconcentrated floods and moderate/low sediment-laden floods have always been observed in the Lower Yellow River (LYR) characterized by complex channel-floodplain systems of alternated meandering and straight segments. Interactions between those floods and sophisticated morphological segments are much more complicated than normal low-sediment laden rivers of relatively simple geometry. In this regard, we numerically investigate the 92.8 consecutive floods in the natural channel-floodplain reach of Xiaolangdi-Jiahetan in the LYR by deploying a 2-D depth-averaged fully coupled morphological model. The major focus includes (1) the unusual phenomenon of downstream peak discharge increase and (2) the different hydro-morphodynamic behaviors between meandering and straight channel-floodplain systems. For the former, the peak discharge increase of hyperconcentrated floods could be satisfactorily reproduced when the effects of bed roughness reduction and bed deformation are considered simultaneously. For the latter, the water-sediment exchange between channels and floodplains is relatively strong in hyperconcentrated floods and exhibits distinct features in meandering and straight segments. The straight one is featured by lateral channel-floodplain diffusion while the meandering one is characterized by the transition from lateral diffusion at the meander apex to streamwise advection. Consequently, the deposition at the meanders (especially on the floodplains) is much larger than that at the straight reach floodplains resulting in a remarkable uneven deposition pattern along the streamwise direction.

Key words: Lower Yellow River; Hyperconcentrated floods; Channel-floodplain interactions; Morphological modelling; Sediment transport

Acknowledgements: National Natural Science Foundation of China (No. 12272349, 52339005).

How to cite: Li, W., Zhu, L., and Hu, P.: Modelling interactions between consecutive floods and channel-floodplain systems in the Lower Yellow River, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7028, https://doi.org/10.5194/egusphere-egu24-7028, 2024.

Granular flow down a rough incline is a typical model case for geophysical mass flows. For insufficiently rough inclines, a strongly sheared basal layer can form below the less agitated bulk layer due to basal slip and particle collisions. However, the thickness and kinematic characteristics of the basal layer has not been well understood. Here, discrete element method (DEM) simulations are carried out to investigate the effects of base roughness on various kinematics profiles (i.e., velocity, shear rate and granular temperature) of the basal layer. The base roughness is varied systematically from geometrically smooth (i.e., a flat frictional plane) to moderately and sufficiently rough (formed by a layer of stationary particles). The base roughness is quantified by a dimensionless parameter, R_a, varying from 0 to 1, which has previously been found to control the transition from slip to non-slip regimes at around R_a=0.6. The present results show that, when basal slip occurs, the velocity profile deviates from the standard Bagnold’s profile, with an apparent basal slip and a basal layer where particles are highly agitated. The thickness of the basal layer, the slip velocity, and the level of velocity fluctuations (granular temperature) in the basal layer are all controlled by R_a. Intriguingly, the thickness of the basal layer, which is about several particle diameters, is insignificantly affected by other simulation conditions including the flow thickness and slope angle. Finally, the velocity profile is accurately described by a semi-empirical function based on the strong association between granular temperature and shear rate. Future work will focus on the rheology of the basal layer, which will potentially lead to more accurate predictions of geophysical granular flows.

How to cite: Wang, T., Jing, L., and Kwok, F.: Formation and Kinematics of Basal Layer in Granular Flows Down Smooth and Rough Inclines, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9106, https://doi.org/10.5194/egusphere-egu24-9106, 2024.

Large dams exploiting hydropower have been marvels of engineering practice, but over the decades their accrued environmental effects, such as sediment budget balances (due to upstream aggregation and downstream erosion) and water quality and fish biota degradation, were visible. Moreover, large centralised hydropower systems present the challenge of grid connectivity, as it can be challenging to connect large electricity grids to remote and inaccessible rural areas, not only due to costs but also due to the loss of energy due to high distances. Scotland having many small rural communities and thousands of small low-head streams, is a prime example for efficiently demonstrating tackling the above crucial challenges of small scale decentralised power generation, with alternative schemes such as micro-hydropower and hydro-kinetic systems. These flexible to install and operate systems, can help prevent grid connectivity problems and electricity loss. They can be installed in several locations due to their small assembly and easy construction process compared to large hydropower plants. They can also be installed at wastewater plants to exploit outlet flows. In this study several criteria were analysed to assess the new technologies based on data collected from various suppliers. The criteria covered several aspects of the technologies: health and safety, design, environmental constraints, employability, and financial viability. The selection process started to classify the viability of the technologies according to the score they achieved. The technologies are assessed, and optimal use sometimes based on the location and real world application, are offered.

How to cite: El Mir, M. A. and Valyrakis, M.: Assessment and evaluation of the utility of hydrokinetic technologies in low head streams, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9390, https://doi.org/10.5194/egusphere-egu24-9390, 2024.

We conducted a series of laboratory experiments to investigate the impact of vegetation on bedload transport rates depending on submergence. In the experiments, we used aluminum rods to simulate rigid vegetation, with vegetation submergence ratios (i.e., the ratio of water depth to vegetation height) ranging from 1 to 2. The bedload transport rates were measured by collecting sediment at the end of the vegetated area. The findings indicate that, with a constant bulk-averaged flow velocity, bedload transport rates decrease as the submergence ratio increases. This decrease is attributed to changes in the flow velocity distribution resulting from the flow resistance exerted by submerged vegetation. Indeed, water flows more easily through the top of the vegetation, and concurrently water velocity decreases significantly in the bottom region occupied by the vegetation. Building upon the phenomenological theory of turbulence, we propose a hydraulic radius-based method for estimating bed shear stress by incorporating the submergence ratio effect. This model enables the application of Cheng’s (2002) bedload formula, originally developed for bare beds, to predict bedload transport rates in both emergent and submerged vegetated flows. The present model, calibrated with a single parameter from experimental data, exhibited an average relative error of about 400% when validated with using experimental data (275 data in all) from our study and the relevant literature.

How to cite: Lu, Y., Cheng, N.-S., Wei, M., and Ancey, C.: Vegetation Submergence Effects on Bedload Transport Rate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9559, https://doi.org/10.5194/egusphere-egu24-9559, 2024.

Particle-size segregation is a widespread process that affects granular materials. Under the influence of gravity and shear, particles segregate into distinct regions according to their size. To date, most experimental investigations have studied granular flows induced by gravity and shear. Less studied is the special case where the granular material is segregated under convection. We are concerned with this particular case. We conducted experiments by shearing bi-dispersed granular mixtures in an annular shear cell. Refractive-index matching (RIM) was achieved between particles and the surrounding fluid, which made it possible to visualize the granular flow when illuminated by a laser sheet. We reconstructed the particle spatial arrangement by applying the Hough Transformation to a continuous series of scans. Both axial and radial segregation was observed in experiments, i.e., small particles tended to percolate downwards and accumulated radially to the center region, while large particles were squeezed upwards and gathered in the exterior region. We found that axial segregation was related to gravity and shear, while the radial convection was related to the shear and convection. Solids volume fractions were computed as a function of time from three-dimensional scans of granular mixtures, from which segregation velocity was then derived. The experimental data provides interesting insights into segregation produced simultaneously in two directions.

How to cite: Chen, Y., Ancey, C., and Gray, N.: Segregation of granular mixtures in an annular shear cell under shear, gravity, and convection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9650, https://doi.org/10.5194/egusphere-egu24-9650, 2024.

In Nepal, urbanization has significantly accelerated since 2017 due to the conversion of numerous rural administrative units into urban ones by the government. This trend is particularly pronounced in the Kathmandu Valley where development is taking place on a large scale, including the building of four smart satellite cities, an outer ring road and river corridor roads flanked by green belts. The result is increased urban sprawl, river channelization, and floodplain encroachment, accompanied by sand and gravel mining activities. Many embankments have been constructed for flood protection along the rivers in the Kathmandu valley, including the Nakkhu River. However, the increasing number of settlements in low-lying floodplain areas and associated infrastructure damage caused by overtopping, breaching, or seepage of embankments, raise questions about the long-term sustainability of embankments as a solution to prevent future floods.

Using numerical simulations in a coupled hydrodynamic and landscape evolution model, CAESAR-Lisflood, we investigate how such embankments affect sediment transport, channel geometry, conveyance capacity, and flood inundation along the Nakkhu River. Each simulation is based on a high-resolution digital elevation model (2 m pixels, acquired in 2019-2020). Input sediment grain sizes are derived from field measurements, and we drive the model for different flood scenarios using maximum daily discharge data provided from the Department of Hydrology and Meteorology, Nepal.

The results suggest that changes in channel geometry caused by sedimentation increase flood risk downstream, particularly where embankments have been built to replicate sinuous channel courses. Inundation area is significantly higher in a scenario that includes sediment transport compared to a flood event modelled without sediment. It is recommended that sediment transport analysis be undertaken in the routine design of embankments and planned developments for river floodplains to minimize flood risk. Our study indicates that the construction of embankments alone may not provide sustainable long-term protection against future floods in rivers carrying high sediment loads.

Keywords: River embankment; Sediment transport; River morphology; Flood modelling; Nepal

How to cite: Thapa, S., Sinclair, H. D., Creed, M. J., Mudd, S. M., Attal, M., Borthwick, A. G. L., and Ghimire, B. N.: Impact of sediment transport on newly constructed embankments and flooding in the Nakkhu River, Kathmandu, Nepal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9765, https://doi.org/10.5194/egusphere-egu24-9765, 2024.

Abstract: The subaqueous bedforms in mountainous macrotidal estuaries, distinguished by their large tidal range and strong tidal and river flow dynamics, exhibit complex interactions among hydrodynamics, sediment transport, and bedform morphology, setting them apart from river and marine bedforms. However, there is currently a lack of research on the development characteristics and mechanisms of bedforms in such estuaries. To address this gap, field observations were conducted in the Minjiang Estuary of the East China Sea in December 2021 and August 2023, utilizing multibeam echosounders, shallow seismic profilers, and Acoustic Doppler Current Profilers (ADCP). Field measurements, including bedform morphology, surface sediment grain size, and hydrodynamics, were collected during both flood and ebb seasons. The study aims to explore the development characteristics and evolutionary patterns of bedforms in mountainous macrotidal estuaries, using the Minjiang Estuary as a representative case. The results indicate that the surface sediments in the subaqueous delta plain to the delta front channel of the Minjiang Estuary are predominantly composed of gravelly sand, with a median grain size ranging from 12.77 to 724.51 µm. Large compound bedforms are prevalent, with wavelengths ranging from 7.23 to 233 m and heights from 0.1 to 11.42 m. Bedform size is positively correlated with sediment grain size in the respective regions, and bedform morphology is related to sediment composition and water depth. Bedforms in different regions of the Minjiang Estuary exhibit varying degrees of symmetry, with asymmetry being more common, occasionally interspersed with cosinusoidal bedforms exhibiting better symmetry, which correlates with the strength of regional tidal dynamics. This study is of significant importance for understanding and simulating estuarine hydrodynamics and sediment transport.

Keywords: Mountainous Macrotidal Estuary, Minjiang Estuary, Bedform Morphology, Subaqueous Bedforms, Tidal Currents

How to cite: Liu, R., Cheng, H., Teng, L., Ren, Z., Chen, J., Yang, Q., and Fan, H.: Subaqueous bedform morphology and migration in a mountainous macrotidal estuary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9774, https://doi.org/10.5194/egusphere-egu24-9774, 2024.

The mechanics of geophysical granular flow has been widely studied using spherical particles. However, natural granular materials are nearly always non-spherical, and a fundamental understanding of how particle shape affects the dynamics of granular flow remains elusive. Here, we use the discrete element method to simulate dense granular flows down a rough incline with systematically varied particle elongation (indicated by the length-to-diameter aspect ratio, AR). For each value of AR, we first determine the well-known h_stop curve delimiting no-flow and steady flow regimes and then carry out steady flow simulations above the h_stop curve to extract Pouliquen’s flow rule relations between the Froude number (Fr=u/(gh)^0.5) and the normalized flow thickness h/h_stop, where u is the mean flow velocity, h is the flow thickness and g is the gravitational acceleration. Our results show that the Fr-h/h_stop relations have a nonlinear dependence on AR (data collapse is not immediately achieved). Next, we analyze the statistics of particle orientation during the flow using a microscopic order parameter and find that more elongated particles tend to align better along a certain orientation, thus hindering the particle rotation. The dependence of the measured order parameter on AR seems to explain the trend in the Fr-h/h_stop relations, but further investigations are needed to quantitatively connect this micromechanical understanding with the macroscopic flow behaviors. Finally, the effects of other shape parameters, such as particle flatness and angularity, will be studied to draw a fuller picture of how the particle shape affects the mobility of geophysical granular flows.

How to cite: Jing, L. and Liu, J.: Effects of particle elongation on dense granular flows down a rough inclined plane, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9977, https://doi.org/10.5194/egusphere-egu24-9977, 2024.

In natural water bodies, sheared turbulent flows are the forcing agent responsible for particle mobilization near the river bed surface. Several analytical approaches have been used to describe this phenomenon, with ambiguities in the analytical methods employed, resulting in methodological biases. The application of a machine learning technique, namely, Adaptive Neuro-Fuzzy Inference System (ANFIS), is proposed here to model sediment transport dynamics. It is hypothesized that turbulent flow of different magnitudes and sufficient duration or near bed instantaneous flow power is responsible for particle displacement. The entrainment of sediment is modeled using the dynamic incipient motion criteria of impulse and energetic turbulent flow events. Several ANFIS architectures have been developed to relate the hydrodynamic vectorial quantities to particle displacement. ANFIS combines artificial neural networks' adaptation and learning power with the advantage of fuzzy inference (IF-THEN) rules for knowledge representation. To demonstrate ANFIS applicability for near bed threshold conditions, streamwise velocity [1], and particle dislodgement [2], flume-based experimental data sets are obtained as input and output signals to train the ANFIS model of various architecture complexities. The energy-based criterion and impulse criterion are obtained as cubic and quadratic expressions of streamwise velocity, respectively, and they are also used as inputs to train the ANFIS model [3]. Following a trial and error approach, the models developed with these criteria are analyzed and compared in terms of their efficiency and predictability using several performance indices. The optimum performing model is found capable of replicating the complex dynamics of sediment transport.

References
[1] Liu, D., AlObaidi, K., Valyrakis, M.* (2022). The assessment of an Acoustic Doppler Velocimetry profiler from a user’s perspective, Acta Geophysica, 70, pp. 2297-2310. DOI: 10.1007/s11600-022-00896-3.
[2] AlObaidi, K., Valyrakis, M. (2021). Linking the explicit probability of entrainment of instrumented particles to flow hydrodynamics, Earth Surface Processes and Landforms, 46(12), pp. 2448-2465 DOI: 10.1002/esp.5188.
[3] 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, DOI:10.1002/hyp.8228.

How to cite: Valyrakis, M. and Ojo, T.: Incipient particle entraiment prediction with the use of machine learning methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10063, https://doi.org/10.5194/egusphere-egu24-10063, 2024.

Riprap sloping structure is effective as bridge pier scour protection in the immediate vicinity of piers. In turn, riprap disrupts the flow conditions in a larger area than is the case with piers without scour protection in place. While these structures effectively dissipate the turbulent energy around piers, scouring occurs at the toe of the riprap and threatens the stability of the riprap and adjacent riverbed or hydraulic structures in proximity. This research presents the temporal evolution of the scour hole forming next to the riprap sloping structure. The research combines flume experiments with a physical model and numerical simulations using FLOW-3D software calibrated with experimental data measured with an optical surface scanner. Investigating the change in the scour hole dimensions over time provides valuable insights into the understanding of scour development and the associated undermining of the riprap toe during flood events that can jeopardize the bridge stability. The results show that, while scour generally increases with the duration of the flood, there are also evident backfilling events that need to be recognized and accounted for during the bridge design.

References:
[1] Harasti, A.; Gilja, G.; Potočki, K.; Lacko, M. Scour at Bridge Piers Protected by the Riprap Sloping Structure: A Review. Water 2021, 13, 3606. https://doi.org/10.3390/w13243606
[2] Harasti, A.; Gilja, G.; Adžaga, N.; Žic, M. Analysis of Variables Influencing Scour on Large Sand-Bed Rivers Conducted Using Field Data. Appl. Sci. 2023, 13, 5365. https://doi.org/10.3390/app13095365

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

How to cite: Harasti, A., Gilja, G., Vuco, J., Boban, J., and Valyrakis, M.: Temporal development of the scour hole next to the riprap sloping structure, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10349, https://doi.org/10.5194/egusphere-egu24-10349, 2024.

One approach to scour protection for bridge piers is constructing riprap sloping structure around the pier. To maintain its designated function, riprap must remain stable throughout the service life of the bridge, often exceeding 100 years and thus being vulnerable to more extreme hydrological events driven by climate change. The riprap sloping structure increases the size of the recirculation zone and turbulence downstream compared to a single pier. This paper presents the results of a detailed investigation of flow field dynamics over the scoured riverbed downstream of the riprap sloping structure. The research combines flume experiments with a physical model and numerical simulations using FLOW-3D software calibrated with experimental data measured with an acoustic Doppler velocimetry profiler, Vectrino ADVP. Investigating the complexities of the flow field resulting from the presence of riprap and interactions between the flow and scour development is essential for enhancing the design and performance of riprap structures in various hydraulic conditions. The results show that the change in scour geometry over time influences the flow direction in the zone downstream of the pier.

References

[1]    Gilja, G.; Fliszar, R.; Harasti, A.; Valyrakis, M. Calibration and Verification of Operation Parameters for an Array of Vectrino Profilers Configured for Turbulent Flow Field Measurement around Bridge Piers—Part I. Fluids 2022, 7, 315. https://doi.org/10.3390/fluids7100315

[2]    Gilja, G.; Fliszar, R.; Harasti, A.; Valyrakis, M. Calibration and Verification of Operation Parameters for an Array of Vectrino Profilers Configured for Turbulent Flow Field Measurement around Bridge Piers—Part II. Fluids 2023, 8, 199. https://doi.org/10.3390/fluids8070199

Acknowledgments

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

How to cite: Gilja, G., Harasti, A., Delija, D., Mejašić, I., and Valyrakis, M.: Change in flow field next to riprap sloping structure caused by variability of scoured bathymetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10417, https://doi.org/10.5194/egusphere-egu24-10417, 2024.

How to cite: Yamasaki, T., Houseago, R., Hodge, R., Hardy, R., Rice, S., Ferguson, R., Hackney, C., Yager, E., Johnson, J., and Hoey, T.: Measuring flow resistance in rough-bed rivers using flume and CFD approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11224, https://doi.org/10.5194/egusphere-egu24-11224, 2024.

The transition of supercritical turbidity-current bedforms has been studied in the flume experiments and outcrops, whereas similar bedform transitions in deep-sea cases are rare. To better understand the mechanism behind bedform transitions in natural environments, we investigated the tempo-spatial transition of supercritical turbidity-current bedforms in the lower continental slope to abyssal plain in the northeastern South China Sea, by high-quality single-channel seismic data analysis coupled with simple numerical modeling. Quaternary bedforms were delineated at >3400 m water depth, covering an area of ~20000 km². These bedforms are characterized by long wavelength (0.4-5 km), low wave height (1-15 m), and large aspect ratio (80-730), which are identified as supercritical-flow bedforms. Four types of bedforms were further identified based on the morphology and internal structure, which are (I) upslope-migrating cyclic steps characterized by asymmetrical morphology with thick backsets and long wavelength; (II) upslope-migrating antidunes (UMAs) featured by nearly symmetrical morphology and relatively short wavelength; (III) downslope-migrating antidunes (DMAs) typified by gentle and sigmoid foresets and large aspect ratios; (IV) upper-stage plane beds (UPBs) consisting of low-relief wavy to subhorizontal reflections. Slope variations are highlighted to induce flow energy changes and facilitate bedform transitions. A slight slope decrease from 0.5 to 0.1° and 0.3 to 0.1-0.2° would respectively lead to the transition from UMAs to UPBs and from cyclic steps to UMAs, due to the hydraulic jump and flow acceleration. In contrast, an increased slope from 0.1 to 0.2° can contribute to the transition from UMAs to cyclic steps or DMAs by re-accelerating flows. Over time, the bedforms evolve from DMAs to UMAs and cyclic steps with growing wavelengths and wave heights, possibly caused by the inherited development of bedforms and increasing aggradation rates linked with progressively rising Taiwan uplifting rates. These bedforms consist of three contiguous fields fed by inter-seamount pathways and Manila Trench, comprising a supercritical-flow submarine fan apron that is far from the shelf edge and lacks submarine channels. This research was supported by the National Key Research and Development Program of China (Grant Number 2022YFF0800503).

How to cite: Wang, B., Zhong, G., Wang, L., and Kuang, Z.: How do supercritical turbidity-current bedforms transition? Insights from seismic data interpretation in the South China Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11293, https://doi.org/10.5194/egusphere-egu24-11293, 2024.

Offshore tidal sand waves on the sandy bed of shallow continental shelf seas are more three-dimensional (3D) in some places than others, where 3D refers to a pattern that shows variations in three spatial directions. These sand waves often display meandering, splitting, or merging crestlines. The degree of three-dimensionality seems to vary especially when large-scale bedforms, such as tidal sand banks, are present underneath the sand waves. Understanding this behavior is important for offshore activities, such as offshore wind farm construction or the maintenance of navigation channels. In this study, the degree of three-dimensionality of sand waves at five sites in the North Sea is quantified with a new measure. Results show that tidal sand waves on top of tidal sand banks are more two-dimensional (2D) than those on bank slopes or in open areas. Numerical simulations performed with a new long-term sand wave model support these differences in sand wave patterns. The primary cause of these differences is attributed to the deflection of tidal flow over a sand bank, which causes sand wave crests to be more aligned with the bank at its top than at its slopes. It is subsequently made plausible that the different patterns result from the competition between two known mechanisms. These mechanisms are nonlinear interactions between sand waves themselves (SW-SW interactions) and nonlinear interactions between sand banks and sand waves (SB-SW interactions). On bank tops, SB-SW interactions favor a 2D pattern, while SW-SW interactions, which produce a 3D pattern elsewhere, are less effective.

How to cite: Nnafie, A., Krabbendam, J., Borsje, B., and de Swart, H.: Background Topography Affects the Degree of Three-Dimensionality of Tidal Sand Waves, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12742, https://doi.org/10.5194/egusphere-egu24-12742, 2024.

Detecting the stability of nearshore subaqueous geomorphology is a crucial challenge for ensuring early warning and controlling the stability of riverbank slopes. Acquiring nearshore subaqueous geomorphology data using unmanned ship-mounted acoustic multibeam systems is difficult, costly, and time-consuming. Moreover, it is often influenced by weather conditions. The limited availability of nearshore subaqueous geomorphology samples suitable for model training, combined with the high similarity between targets of nearshore unstable geomorphology and the background, poses significant challenges for traditional detection methods. In response to issues such as high similarity in subaqueous geomorphology images, large-scale variations in target size, and a scarcity of samples, this study proposes a nearshore subaqueous geomorphology instability detection framework based on Few-shot learning. Firstly, a feature extraction network is designed, replacing the backbone network with a Swin Transformer network. This network employs a feature pyramid network to extract multi-scale geomorphology features containing global information from the query set, facilitating the fusion of features across deep and shallow layers. Secondly, a weight adjustment module is devised to transform the support set into weight coefficients with class attributes. This adjustment helps in adapting the distribution of geomorphology features for detecting new class objects. Experimental results demonstrate that the proposed detection framework achieves desirable performance in terms of average precision and average recall indicators.
Keywords: Subaqueous Geomorphology; Stability Detection; Few-shot learning

How to cite: Ren, Z., Zhang, P., Cheng, H., Teng, L., Chen, J., Jin, Y., Liu, R., Jia, Z., and Zhang, H.: Research on nearshore subaqueous geomorphology stability detection based on few-shot learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13532, https://doi.org/10.5194/egusphere-egu24-13532, 2024.

Grain transport by saltation is involved in numerous geophysical phenomena such as wind-blown sand, snow drift, aeolian soil erosion, dust emission, etc. Particle impacts on a granular bed trigger rebound and ejections processes, which can lead in certain conditions to a steady state of solid transport. The present work is dedicated to the analysis of the impact processes at the grain scale, with the objectives of inferring robust statistical laws and better understanding granular transport, accounting for the possible role played by adhesion between the grains.

The study is based on numerical simulations with the DEM (Discrete Element Method). The numerical experiments consist in throwing a spherical particle on a granular packing with controlled velocity (Froude number between 0 and 200) and impact angle (between 10° and 90°). The contact model (friction, cohesion) between the grains is varied to represent different types of granular materials (e.g., dry sand, wet sand, snow).
We investigated the influence of incident parameters on the impact process, focusing on the incident particle rebound and on the number and velocities of ejected particles. For non-cohesive granular beds, the simulations were compared to laboratory experiments of impacts of spherical particles on granular packings in order to validate the model . In particular, the restitution coefficient of the incident particles and the number of ejected particles were found in good agreement with experimental results. The simulations also give access to quantities that cannot be easily measured in the experiments. Hence, we could observe an anisotropy of ejected particles velocities for grazing impact angles, which is more pronounced when the incident velocity decreases.
Preliminary results concerning cohesive granular beds will also be presented, considering contact laws representative of liquid (capillary) and solid cohesion processes. Effect of cohesion on the number of ejected particles, and energy dissipation processes within the cohesive granular beds, will be discussed.

How to cite: Mahjoub-Bonnaire, P., Bourrier, F., Oger, L., and Chambon, G.: Modeling particle impacts on granular media for the analysis of aeolian saltation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15069, https://doi.org/10.5194/egusphere-egu24-15069, 2024.

Despite the recommendations given in Ashley (1990), a plethora of terms continues to be used to describe flow-scale flow-transverse sedimentary bedforms, often without clear definition or distinction between the different nomenclatures. For example, (marine) dunes and sand waves are used interchangeably in many contexts. Smaller bedforms superimposed on larger ones may be referred to as megaripples or secondary dunes. It is currently unclear if different terms are used due to intrinsic morphological or genetic differences or due to the traditions of different scientific communities. Ashley (1990) already noted that the “poor communication among scientists and engineers has perpetuated the multiplicity of terms”. Researchers from fluvial, coastal or deep-marine environments, from industry or academia, from various disciplines, such as sedimentology, oceanography, coastal and offshore engineering or geomorphology may use a specific vocabulary. Furthermore, terminology may differ depending on the country or research group in which they work. All this makes communication difficult and may cause misinterpretations, hindering progress in understanding and cross-disciplinary collaborative pursuits.

The aim of the present contribution is to provide an updated classification of the different types of underwater flow-transverse sedimentary bedforms. The intent is to homogenise the nomenclature for researchers coming from different disciplines and working in varied environments, to enable the use of a common classification and terminology to improve knowledge exchange, comparison and dialogue.

We propose a description table, which can be used by scientists and practitioners to describe the sedimentary bedforms with which they are working. Importantly, each bedform characteristic is described and the way to calculate the quantitative descriptive parameters is detailed. The description table aims at providing a standard and consistent way to describe the bedforms and their environmental setting prior to classifying them. The description table can be used independently of bedform type and further classification, which should overcome communication issues.

Two classification schemes are then proposed. The first is based on an understanding of the genetic processes. This should be used whenever possible because it informs about the underlying processes which formed the bedform. In order to complement the process-based classification, or in situations where the genetic processes are unknown, a second, geomorphological classification is introduced. Thus, we urge the bedform community to consider deploying these descriptor and classification tools and hope our contribution leads to a much more transparent and cohesive future in bedform research.

How to cite: Lefebvre, A., Dalrymple, R. W., Cisneros, J., Scheiber, L., Hulscher, S., Slootman, A., Kleinhans, M. G., and Miramontes, E.: Classification of underwater flow-transverse sedimentary bedforms, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15693, https://doi.org/10.5194/egusphere-egu24-15693, 2024.

The study of the geomorphic dynamics of consecutive bends in Yangtze River under controlled conditions, i.e., the regulated water and sediment process, and the bank protection project, contributes to the further understanding of the meandering river theory. In this study, by combining the topographic data and remote sensing data, the morphological adjustment of typical consecutive bends in Yangtze River in response to upstream damming are analyzed. The results show that during 2006-2021, the riverbed is scoured generally. The consecutive bends are generally characterized by inner-bank scouring and outer-bank sedimentation. Besides, the evolution of the front and back bends shows good correlation, and the longer the length of the transition section, the weaker the correlation between the evolution of the front and back bends. The results of the study may serve as a rational reference for managing natural meandering rivers with multiple hydrological, geomorphological, and ecological goals.

How to cite: He, X. and Yu, M.: The morphological adjustment of typical consecutive bends in Yangtze River in response to upstream damming, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15932, https://doi.org/10.5194/egusphere-egu24-15932, 2024.

Based on laboratory experiments, Pouliquen (1999) uncovered a universal scaling law for the average velocity v of homogeneous flows of spherical grains down rough inclines [1]: , where g is the gravitational acceleration, h the flow thickness, and h_s(θ) the thickness below which the flow stops depending on the inclination angle θ. Today, this so-called “flow rule” is well established in the field and has served as a critical test for continuum granular flow models [2]. However, based on more accurate measurements for granular materials composed of either spherical or non-spherical grains, Börzsönyi and Ecke (2007) found and pointed out that this revised flow rule was predicted by a two-dimensional granular kinetic theory [3, 4]. In addition, for non-spherical grains, they noticed deviations from this rule at large h/h_s. Both Pouliquen and Börzsönyi and Ecke assumed that the granular flows in their experiments were steady.

Here, we report on new systematic experiments for granular materials composed of spherical glass beads, different kinds of non-spherical sands, and grain-size-equivalent mixtures of these. Their careful analysis reveals a new grain-shape-dependent flow rule that resolves the above contradictions in the current literature and provides quantitative evidence for the statement that the deviations observed by Börzsönyi and Ecke can be attributed to the flows not having reached the steady state.

[1] Pouliquen O. Scaling laws in granular flows down rough inclined planes[J]. Physics of fluids, 1999, 11(3): 542-548.

[2] Kamrin K, Henann D L. Nonlocal modeling of granular flows down inclines[J]. Soft matter, 2015, 11(1): 179-185.

[3] Börzsönyi T, Ecke R E. Flow rule of dense granular flows down a rough incline[J]. Physical Review E, 2007, 76(3): 031301.

[4] Jenkins J T. Dense shearing flows of inelastic disks[J]. Physics of Fluids, 2006, 18(10).

How to cite: Wu, Y., Guo, Z., Pähtz, T., and He, Z.: Flow rule for unsteady flows of spherical and non-spherical grains down rough inclined planes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16292, https://doi.org/10.5194/egusphere-egu24-16292, 2024.

A spur dike is an elongated artificial structure with one end on the bank of a stream and the other end projecting into the current, and it is the most cost-effective river training structure that can be built at the channel’s banks. A series of spur dikes are usually more efficient in stabilizing the alluvial shores, whereas single spur dikes alter the local field. Thus, analyzing the local scour phenomena surrounding hydraulic structures in rivers is crucial to minimize the hazard of foundation collapse.

Therefore, experiments have been conducted to study the phenomenon of local scouring around the series of repelling spur dikes under clear water conditions, analysis of flow behavior & alterations in the morphology of sediment bed, and turbulent fluctuation. The inclination angle of the non-submerged spur dike with the vertical wall was kept 60⁰ during the study in the straight rectangular flume of length, width, and depth are 15 m, 0.91 m, and 0.70 m. While the projected length of spur dikes was 1/5 of the width of the channel, and the spacing between spur dikes was 2.5 * the projected length of spur dike. In laboratory experiments, the flow velocities and bed deformation around the series of repelling spur dikes were measured using an Acoustic Doppler velocimeter, a high-resolution laser displacement meter, and a point gauge.

The test section consists of uniform sediment particles, the experiment was initiated with a leveled sediment bed, and a scouring phenomenon was observed throughout the experiment at the head, middle, and end of each spur dike in the u/s and d/s. The 3D velocity measurement is done at the head of the spur dike from u/s of the first spur dike till downstream of the third spur dike. Velocity measurements provide information on dominant agents responsible for the local scour.

It was concluded that the maximum depth of the scour hole 14.47 cm at 1^st spur dike head. Digging and siltation was a cyclic process till equilibrium was achieved during the experiment, and the flow was classified as subcritical and turbulent. The approaching flow has less strength between the 1^st and 2^nd spur dike as it moves upward mostly in the top section.  The negative values of  over some length was observed in the scoring zone near the bed. While comparing the value of non-dimensional Reynolds Shear Stress -u^’v^’/u_*²,  -u^’w^’/u_*²,  -v^’w^’/u_*², it was observed that -u^’w^’/u_*², had a much greater both positive and negative value compared to the other. The Turbulent Kinetic Energy distribution shows that there is relatively more turbulence surrounding the 1^st spur dike.

How to cite: Kumar, S. and Hanmaiahgari, P. R.: Experimental modelling of local scour phenomenon at a series of repelling emergent spur dikes , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17522, https://doi.org/10.5194/egusphere-egu24-17522, 2024.

Determination of flood magnitude and shape characteristics are necessary to provide a more complete assessment of flood severity and its impact in scour development analysis. Our recent research has focused on a joint distribution approach to account for the multivariate nature of flood characteristics, resulting in probability of occurrence of different pairs of flood variables: flood peak (Q), volume (V) and duration (D). To extend the results of this research, a method for deriving a design hydrograph is applied to the study area by using the typical hydrograph method. As it is recommended to test multiple scenarios in a scour analysis, different typical flood hydrographs were selected at several gauging stations on the Sava and Drava rivers in Croatia and multiplied by the design discharge values. The aim of this study is to complement the ongoing research of the relationship between climate change indicators, flood wave characteristics and scour development next to the bridges crossing large rivers in Croatia with installed scour countermeasures by preparing hydrological input data for a hydraulic scour analysis.

How to cite: Lacko, M., Potočki, K., Škreb, K. A., Bezak, N., and Gilja, G.: Typical design hydrograph method based on a joint distribution approach combining flood peak discharge, volume and duration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17681, https://doi.org/10.5194/egusphere-egu24-17681, 2024.

Granular media has near omnipresence in nature and is the second most processed substance in industry, after water. It is well accepted that it exhibits a wide spectrum of macro-scale behaviour which is ultimately determined by the grain-scale interactions of its constituent particles [1][2][3]; but there is still much to be discovered about those grain-scale interactions themselves. Away from the free surface of an agitated granular bed, the dominant grain-scale interactions are relative sliding and rolling between neighbouring particles [4], and it is this sliding and rolling which is the subject of this research.

In these experimental lab-based tests, ‘dry’ and ‘wet’ ideal granular beds are harmonically compressed via a moving side-wall and their responses captured via high-speed imaging. The granular media itself is a quasi-2D bed of polydisperse discs consisting of an even mixture of five different disc diameters ranging from 11mm to 36mm. The cyclic compressions are specifically designed to impose a jamming effect within the granular beds, before subsequent relaxation and deformation.

Use of the photo-elastic technique provides a window through which the grain-scale behaviour of the beds can be examined, as networks of inter-particle contact forces, known as force chains, become visible. Disc rotation is measured by tracking lines drawn onto each disc, providing useful insight into the sliding and rolling inter-particle interactions at the grain-scale. First, the behaviour of a ‘dry’ granular bed is examined, and then a thin layer of glycerol is spread onto the edges of each individual disc in order for the behaviour of an equivalent ‘wet’ granular bed – or at least, a bed with reduced inter-particle friction – to be examined. The behaviour of these beds are then compared to one another, and the results used to discuss how changes to friction at the grain scale affects the behaviour of granular bodies.

[1] Singh, S., Murthy, T.G.: Evolution of structure of cohesive granular ensembles in compression. International Journal of Solids and Structures 238(1), 111359 (2022)

[2] Jiang, M., Yu, H., Harris, D.: A novel discrete model for granular material incorporating rolling resistance. Computers and Geotechnics 32(5), 340–357 (2005)

[3] Oda, M., Konishi, J., Nemat-Nasser, S.: Experimental micromechanical evaluation of strength of granular materials: effects of particle rolling. Mechanics of Materials 1(4), 269–283 (1982)

[4] Moss, J., Glovnea, R.: Behavioural responses to horizontal vibrations of quasi-2D ideal granular beds: an experimental approach. Granular Matter 25(4), 63 (2023).

How to cite: Moss, J. and Glovnea, R.: Friction at the grain-scale: the role of inter-particle friction in granular media and its influence on grain-scale bed behaviour, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18798, https://doi.org/10.5194/egusphere-egu24-18798, 2024.

Most aeolian sand transport models incorporate a so-called splash function that describes the number and velocity of particles ejected by the splash of an impacting particle. It is usually obtained from experiments or simulations in which an incident grain is shot onto a static granular packing. However, it has recently been discovered that, during aeolian sand transport, the bed cannot be considered as static, since it cannot completely recover between successive impacts. This led to a correction of the splash function accounting for cooperative effects [1], which were shown to be responsible for an anomalous third-root scaling of the sand flux with the particle-fluid density ratio s, observed in discrete-element-method-based simulations of aeolian sand transport across six orders of magnitude of s [2]. The model by [1] represents the aeolian transport layer by two species: high-energy saltons that eject low-energy reptons upon impact. While it quantitatively captures measurements and the simulated sand flux scaling, it does not recover the scaling laws of the simulated transport threshold and vertical flux at the bed. Here, we improve the model by [1] by means of a three-species saltation model. The additional species, called leapers, represent the fastest reptons, ejected by saltons in rare extreme ejection events. Together, saltons and leapers quantitatively reproduce the threshold and sand flux scaling behaviors, whereas reptons are predominantly responsible for the vertical bed surface fluxes seen in the simulations.

[1] Tholen, Pähtz, Kamath, Parteli, Kroy, Anomalous scaling of aeolian sand transport reveals coupling to bed rheology, Physical Review Letters 130 (5), 058204 (2023). https://doi.org/10.1103/PhysRevLett.130.058204

[2] Pähtz, Durán, Scaling laws for planetary sediment transport from DEM-RANS numerical simulations, Journal of Fluid Mechanics 963, A20 (2023). https://doi.org/10.1017/jfm.2023.343

How to cite: Chen, Y., Pähtz, T., Tholen, K., and Kroy, K.: A three-species model of aeolian saltation incorporating cooperative splash, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19002, https://doi.org/10.5194/egusphere-egu24-19002, 2024.

We characterize experimentally the upstream-progressing jamming wave triggered by the clogging of a granular flow down a partially obstructed chute. We generated dry granular flows in a sloping chute whose outlet was obstructed by a wall with two vertical gaps, twice the diameter of the granular material. We conducted 31 repetitions of the same test to obtain stable statistics. We employed Particle Tracking Velocimetry (PTV) to determine particle velocities at the sidewall and estimated fields of mean velocity and granular temperature by ensemble-averaging. Each ensemble is a set of valid grain velocities collected in space-time bins, that map the entire domain, over all test repetitions. The system is highly dissipative due to collisions and enduring contacts among inelastic particles, resulting in generalised cooling. Clogging occurs as a consequence of the formation of stable arch-like structures at the outlet, while the flow cools down. We observe that the jamming wave propagates against the flow at different values of granular temperature and mean velocity. There is no triple point in the system in the sense that jamming is always preceded by gas-liquid transition. For the tested conditions, jamming can be described as an accretion problem, leading to a granular solid state from liquid state and never from the gaseous state. The jamming wavefront progresses faster as the values of the granular temperature decrease. Flow cooling, including gas-fluid transitions, seem independent of jamming, which is compatible with the range of observed granular Froude and Mach numbers. The jamming wavefront becomes faster than the adiabatic speed of sound of the granular material moving towards the jammed region.

Acknowledgements: This work was partially funded by the Portuguese Foundation for Science and Technology (FCT) through Project DikesFPro PTDC/ECI-EGC/7739/2020 and through CERIS funding UIDB/04625/2020

How to cite: L Ferreira, R. M., Mendes, S., Aleixo, R., Amaral, A., and Larcher, M.: Kinematics of the jamming front resulting from the clogging of the flow of monodisperse inelastic particles in a partially obstructed chute, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20911, https://doi.org/10.5194/egusphere-egu24-20911, 2024.

We employ a physically-based in-house 2D multi-layered depth and time averaged shallow water model with the capacity to simulate morphology and sediment transport (HiSTAV) to model the erosion of dikes subjected to overtopping. Its conceptual model is based on conservation laws for shallow flows and requires closures for flow resistance, and sources and sinks of transported substances. The conservation laws are discretized within a Godunov-type Finite Volume scheme. HiSTAV design is entirely cross-compatible between CPUs and GPUs, through an intuitive object-oriented approach. HiSTAV requires the parametrization of the processes expressing hydraulic erosion, slope failure and mass detachment. The latter are modelled as sudden collapses of cells of dam body, dry but adjacent to the flow, a process akin to river bank collapse. A secondary mesh is defined to group the cells that form the detached mass. We investigate the effects of the dimension of the group and the values of the parameters (velocity and shear stress) that trigger the collapse. As expected, the bulk erosion rate increases with the size of the detached group. The results of the model were compared with data from laboratory models. Three laboratory tests were carried out in a medium-scale facility located at the Fluvial Facilities of the Hydraulics and Environment Department (DHA) of LNEC. The facility operates in closed circuit and is composed by a 1.40 m wide and 19 m long channel where the river stream is simulated. It allows testing dikes up to 0.50 m height and 2.0 m long. The water level upstream the dike is controlled by a sluice gate placed at the downstream end of the channel. The dike site and the main channel where constructed in an elevated platform, after which there a settling basin (2.10W x 4.5L (m)) where the eroded soil from the failure tests is deposited. A Bazin spillway exists at the end of this structure to measure the dike outflow discharge. We performed 3-D reconstructions of the evolving dike geometry, monitored the water levels in the main channel, the flow discharges in the main channel and across the breach and calculated the surface velocity fields in the vicinity and breach (LSPIV). The rate of breach erosion and the velocities near the breach were compared with the results of the model. It was observed that the size of the detachment group should scale with the breach crest and is influenced by the type of soil.

Acknowledgements: This work was partially funded by the Portuguese Foundation for Science and Technology (FCT) through Project DikesFPro PTDC/ECI-EGC/7739/2020 and through CERIS funding UIDB/04625/2020

How to cite: Jonatas, R., L Ferreira, R. M., Ricardo, A. M., and Amaral, S.: Numerical simulation of dike breaching by overtopping. Influence of the bank erosion operator. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22239, https://doi.org/10.5194/egusphere-egu24-22239, 2024.

Gypsum is a common evaporate mineral in a wide variety of geological settings, especially in arid and semi-arid areas. It often precipitated from the natural brine systems with trace amounts of U and almost no Th, rendering it a potentially valuable U-Th geochronometer. However, U-Th dating of gypsum is often challenging, such as how to quickly and completely digest gypsum into solution, and avoid the re-crystallization of gypsum particles during the digestion and chromatography process. Here we present a rapid and practical method for high-precision U-Th dating of gypsum using the (NH₄)₂CO₃ exchange reaction and double-spike method by MC-ICPMS. Our developed protocol addresses these conventional challenges by using the chemical reaction between calcium sulfate and carbonate, resulting in the (NH₄)₂SO₄ solution and CaCO₃ precipitate. Then the CaCO₃ could be easily digested by diluted acid. With the solid-liquid separation, Ca²⁺ and SO₄^2- ions are also effectively separated, minimizing the recrystallization of gypsum. The (NH₄)₂CO₃ median, the gypsum/carbonate molar ratio of 1: 4, and the exchange reaction duration of 1.5 ~ 2 hours are suggested in this protocol. Since there is no gypsum U-Th dating reference materials to validate the accuracy of different approaches and ensure methods are repeatable across laboratories. We also prepared and characterized two natural gypsum U-Th dating reference materials (PXCG-1, PXCG-2) from PiXiao Cave, southwest China. Data from three different laboratories exhibit good agreement with both ²³⁸U content, δ²³⁴U, ²³⁰Th/²³⁸U activity ratio, and the ²³⁰Th ages. The ²³⁰Th ages of PXCG-1, PXCG-2 RMs proposed are 66.97 ± 0.31 ka, 260.82 ± 3.39 ka, respectively.

How to cite: Wang, X., Wang, L., Ma, Z., Duan, W., and Xiao, J.: U-Th dating of gypsum: methodology and reference materials, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6080, https://doi.org/10.5194/egusphere-egu24-6080, 2024.

The unprecedented environmental changes resulting from anthropogenic activities initiated during the Great Acceleration of the mid-20th century can be traced using radiocarbon analysis. The cosmogenic isotope ¹⁴C, which is produced in the atmosphere, is well-known as the geochronological tool applied to archives of the last 55 thousand years. However, during the last 200 years, the natural signal of ¹⁴C in the atmosphere and connected reservoirs (biosphere, ocean, soils, etc.,) has been perturbed by human activities. Two anthropogenic effects are observed: a decreasing trend observed in ¹⁴C concentration of the atmosphere (Suess effect) which has been temporarily reversed by aboveground thermonuclear tests of the 1950/60s.

The excess of the artificially produced ¹⁴C (bomb pulse) is a useful time marker for the mid-20th century and the detection of the bomb peak in natural archives has thus been proposed as a tool to locate and date the onset of a proposed new epoch, the Anthropocene [1].

Here we present the results of radiocarbon analysis conducted as a part of the research dedicated to establishing the Global boundary Stratotype Section and Point (GSSP) for the proposed Anthropocene series. The studied sites include corals (Flinders Reef, AU and Flower Garden Banks, USA)[2, 3], peat (Śnieżka peatland, PL)[4], lake sediment (Crawford Lake, CA and Searsville Lake, USA)[5, 6] and marine sediment (East Gotland Basin, Baltic Sea)[7]. The variety of records (different carbon reservoirs) required site and sample-specific treatment prior to analysis and site-specific interpretation of the measured ¹⁴C. Nevertheless, the mid-20th century bomb peak was detected at all but one of these sites (Searsville Lake)[6]. In all records, the observed onset of the ¹⁴C bomb peak always postdates 1954, the year of the first atmospheric ¹⁴C bomb increase. The specific reservoir effects and corrections will be discussed.

References

The Anthropocene Review, 2023. 10(1):

1.    Waters, C.N., et al. (Eds.), Candidate sites and other reference sections for the Global boundary Stratotype Section and Point of the Anthropocene series.  p. 3-24.

2.    Zinke, J., et al., North Flinders Reef (Coral Sea, Australia) Porites sp. corals as a candidate Global boundary Stratotype Section and Point  for the Anthropocene series.  p. 201-224.

3.    DeLong, K.L., et al., The Flower Garden Banks Siderastrea siderea coral as a candidate Global boundary Stratotype Section and Point  for the Anthropocene series. p. 225-250.

4.    Fiałkiewicz-Kozieł, B., et al., The Śnieżka peatland as a candidate for the Global boundary Stratotype Section and Point  for the Anthropocene series.  p. 288-315.

5.    McCarthy, F.M.G., et al., The varved succession of Crawford Lake, Milton, Ontario, Canada as a candidate Global boundary Stratotype Section and Point for the Anthropocene series.  p. 146-176.

6.    Stegner, M.A., et al., The Searsville Lake Site (California, USA) as a candidate Global boundary Stratotype Section and Point for the Anthropocene Series. p. 116-145.

7.    Kaiser, J., et al., The East Gotland Basin (Baltic Sea) as a candidate Global boundary Stratotype Section and Point for the Anthropocene series. p. 25-48.

How to cite: Hajdas, I., Crann, C., DeLong, K., Fiałkiewicz-Kozieł, B., Ivar Do Sul, J., Kaiser, J., McCarthy, F. M. G., Turner, S., Stenger, A., Waters, C., and Zinke, J.: 14C bomb peak and the onset of the Anthropocene, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10443, https://doi.org/10.5194/egusphere-egu24-10443, 2024.

Recent advancements in MC-ICPMS technology have significantly enhanced the application of U/Th geochronometry in both biogenic and chemically precipitated carbonate rocks of almost middle Pleistocene to upper Holocene. This burgeoning use, particularly in the study of late Pleistocene earth surface processes, underscores the need for standardized reference materials with a broad age spectrum with different uranium and thorium concentrations. Addressing this need, our study evaluates speleothem specimens, Gol-e-Zard Cave Standard (GZS) and Bergen Speleothem Standard (BSS), as potential reference materials.

BSS-2 was processed as a homogenized powder and dissolved aliquot for U-Th dating using MC-ICP-MS analysis. We employed various digestion and ion-resin chromatography separation methods, followed by U-Th dating using MC-ICP-MS at CENIEH, University of Miami, and University of Mainz. The ion chromatography protocols yielded recovery rates ranging from 85% to over 95%. U-series analyses of powdered BSS-2 indicated uncertainties between 0.2-1.5%, attributed to variations in the Beta-factor and the specific U and Th standard bracketing procedures used across laboratories. The dissolved BSS-2 aliquots yield between 1.5-2% of uncertainty. Obtained U-Th ages were 122.8 ± 3.3 ka (University of Miami), 124.5 ± 0.3 ka (University of Mainz), and 123.9 ± 3.2 ka (CENIEH) in the powdered samples. Furthermore, in dissolved samples, the Th-ages vary between 126.9 ± 2.9 to 127.9 ± 3.1 (CENIEH & University of Miami). GZS was prepared as a dissolved standard and the Th-date results obtained from this stalagmite are 3967 ± 0.1 to 3988 ± 0.1 (University of Miami), and 3967 ± 0.1 to 4060 ± 0.4 (CENIEH).

All Th-dates required no correction as activity ratios [230Th/232Th] exceeded 500 and 150 for BSS-2 and GZS, respectively. The consistency of these preliminary results across different laboratories suggest that GZS and BSS-2 are promising reference materials for U-Series analysis of calcium carbonate.

How to cite: Hasözbek, A., Jiménez-Barredo, F., Sharifi, A., Pourmand, A., Mertz-Kraus, R., Weber, M., Scholz, D., Lauritzen, S.-E., M. Parés, J., and Constantin, S.: Assessing Gol-e-Zard Cave (GZS) and Bergen Speleothem Standards (BSS) for U/Th Geochronometry Using MC-ICP-MS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13250, https://doi.org/10.5194/egusphere-egu24-13250, 2024.

In order to correctly determine leads and lags in the climate system and compare different proxy records over long time periods, it is important to build robust chronologies that can provide the temporal foundation for paleoclimate correlations between marine, terrestrial and ice-core records. One of the main challenges for building reliable radiocarbon-based chronologies in the marine realm is to estimate the regional marine radiocarbon reservoir age correction. Estimates of the local marine reservoir effect, ΔR, during the deglaciation can be obtained by ¹⁴C-independent dating methods such as synchronization to other well-dated archives. The cosmogenic radionuclide ¹⁰Be provides such a synchronization tool. Its atmospheric production rate is globally modulated by changes in the cosmic ray flux caused by changes in solar activity and geomagnetic field strength. The resulting variations in the meteoric fallout of¹⁰Be are recorded in sediments and ice cores and can thus be used for their synchronization.

In this study we use for the first time the authigenic ¹⁰Be/⁹Be record of a Laptev Sea sediment core and synchronize it to the ¹⁰Be records from absolutely dated ice cores. Based on the resulting absolute chronology, the ΔR  was then estimated for the Laptev Sea during the deglaciation. The deglacial estimate for the benthic ΔR value for the Laptev Sea is 345±60 ¹⁴C years, corresponding to a marine reservoir age of 864±90 ¹⁴C years. We discuss the obtained ΔR in comparison to modern ΔR estimates from the literature and its consequences for the age-depth model. Our refined age-depth model can be used as a reference for the Laptev Sea and the wider Siberian regions of the Arctic Ocean.    

How to cite: Nicolas, A., Mollenhauer, G., Malter, M., Wollenburg, J., and Adolphi, F.: Refining the age-depth model of a marine sediment record in the Laptev Sea using Beryllium-10, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17301, https://doi.org/10.5194/egusphere-egu24-17301, 2024.

Keywords: Geochronology, Sediment, Uranium, Thorium, Microwave Digestion, HR-ICP-MS

In Quaternary geochronology, accurately estimating natural radiation exposure is crucial for dating materials using Electron Spin Resonance (ESR) and Optically Stimulated Luminescence (OSL). Traditional methods like gamma and alpha spectrometry, despite their utility, are limited by sample size requirements and time inefficiency, especially in low-radiation contexts. This study explores the efficacy of Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Plasma Mass Spectrometry (ICP-MS), including both Quadrupole (ICP-QMS) and High-Resolution (HR-ICP-MS), for analyzing uranium, thorium, and potassium concentrations in sediments.

We compared various acid digestion methods using standard hot-blocks, microwave digestion, and single cell microwave technology on Sediment Reference Materials (NIST BRS 8704, OREAS 24d). Potassium detection was more accurate with ICP-OES (96% precision) than ICP-QMS (80%). In contrast, HR-ICP-MS significantly outperformed ICP-QMS in measuring uranium and thorium (U and Th recoveries of 99% and 94% vs. 83% and 81%, respectively). Moreover, microwave-assisted digestion methods showed slight advantages in uranium and thorium recovery.

Our findings suggest that a four-acid microwave-assisted digestion, combined with potassium measurement via ICP-OES in radial mode and uranium and thorium quantification using HR-ICP-MS, offers the most accurate and time-efficient approach for natural dose determination in sediment dating. This methodology is particularly relevant for cave, river, and stream sediments even with expected low uranium levels.

How to cite: Jimenez, F., Hasozbek, A., Duval, M., Pares, J. M., Sarró-Moreno, M. I., Barrado-Olmedo, A. I., Conde-Vila, E., Fernández-Díaz, M., Cobo, J. M., Perez-Estebanez, M., and Alonso-Garcia, J.: Advancing Quaternary Geochronology: Impact of Sample Preparation and Analytical Techniques on Natural Radioactive Dose Assessment in Stream Sediments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18258, https://doi.org/10.5194/egusphere-egu24-18258, 2024.

μGraphiline is an innovative, fully automated graphitization system designed for radiocarbon dating using accelerator mass spectrometry. This system streamlines the conversion of samples into CO₂ and subsequently into graphite. The standard configuration of μGraphiline is capable of preparing 24 targets daily, demonstrating its high throughput. It achieves a graphitization efficiency of over 95% for 1 mg graphite targets. μGraphiline also offers additional modules for stepped combustion, ramped pyrolysis, and oxidation, all of which can be operated at user-defined temperatures. Furthermore, its design ensures a low background and reproducibility, significantly enhancing the accuracy and reliability of radiocarbon measurements.

One of the notable advantages of the system is its low maintenance requirements. It operates efficiently without the need for working gasses such as helium (He), argon (Ar), oxygen (O₂), explosive hydrogen (H₂) or liquid nitrogen, which simplifies its operation and enhances safety. This feature, coupled with its modular design and high efficiency, virtually no cross-contamination between modules and samples makes μGraphiline an advanced solution for radiocarbon dating. Lastly, the system's repeatability and reliability are backed by reference materials measurements from the International Atomic Energy Agency, demonstrating good repeatability. 

This demonstrates μGraphiline's capability to deliver fast, consistent and accurate results, making it a valuable tool for various scientific and research applications.

How to cite: Tudyka, K., Kłosok, K., Jedrzejowski, M., Rakowski, A., Pawełczyk, S., Ustrzycka, A., Miłosz, S., and Kolarczyk, A.: μGraphiline: a high-throughput, low-maintenance, fully automated 14C graphitization system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18925, https://doi.org/10.5194/egusphere-egu24-18925, 2024.

U-series disequilibrium dating or more specifically ²³⁰Th/U - dating of cold-water corals is a major absolute chronological toolbox to study the evolution of coral reefs through time and to determine absolute time scales for climate proxies. Advances in multi-collector inductively coupled ion source mass spectrometry (MC-ICPMS) have continuously improved precision of Th and U isotopic measurements over the past decades thanks the development of new high ohmic resistors for Faraday cups. Consequently, isotopic measurements and absolute precision levels are in epsilon ranges for ²³⁴U/²³⁸U ratios and in the case of materials older than a few tens of thousands of years also for ²³⁰Th/²³⁸U ratios. To obtain accurate ages the corals isotope ratios need to evolve as a U series closed system and must be free of initial ²³⁰Th and non-carbonate materials. The latter being often traced using the natural most abundant ²³²Th isotope. Coral diagenesis, bio-erosion, residual ferromanganese coatings, recrystallization, and recoil displacement of U isotopes are known sources of age disturbances and U series open system behavior. Here, I want to advocate, however, that such cold-water corals can be ideal dating objects opening far reaching perspectives of marine climate science and for past ecosystem studies. Based on approx. 1200 coral ages and isotope ratios of reef-forming cold-water corals, which correspond to strict quality criteria, a perfect agreement with theoretical predictions of a closed U series system can be found. The resulting oceanic initial (²³⁴U/²³⁸U) activity ratio for the past 510 ka varies by at most 6.7 ‰ (2s) surrounding the mean of modern seawater and of all reconstructed values of 146.5 ‰ (HU1 reference material is assumed here to be in secular radioactive equilibrium). Consequently, the ²³⁴U/²³⁸U ratios may be used for dating of old cold-water corals to expand the dating range to more than 1.2 million years. Moreover, any significant deviation between closed system ²³⁴U/²³⁸U ages and ²³⁰Th/²³⁸U ages may be used to detect U series open - system behavior. Based on the combined age determination, more consistent chronologies can be derived for cold-water coral reefs beyond 350 ka and theoretically the quality of this archive has opened a path for absolutely dated marine climate proxy records since the Mid Pleistocene Transition.

How to cite: Frank, N. and the DCWC: 230Th/U and 234U/238U dating of cold-water corals: Approaching the disequilibrium theory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19089, https://doi.org/10.5194/egusphere-egu24-19089, 2024.

Lyoluminescence (LL) is light emission during the solvation of previously irradiated crystals in the liquid-solid interface (Atari, 1980). Our aim is the breakthrough development of lyoluminescence as a dating tool on halite (here: sodium chloride and potassium chloride) for application in Earth Sciences. The positive correlation between radiation dose and LL light emission makes crystal lattice defects viable natural ionizing radiation dosimeters. With a saturation dose of ~10 kGy (e.g. Atari et al., 1973) for sodium chloride dissolved in pure water and for realistic dose rates of ~4 Gy/ka (e.g., Han et al., 2014), the LL signal from salt minerals potentially may determine an age up to 2.5 Ma.
We hypothesize that LL, naturally observable in salt minerals, will allow dating the last recrystallization event significantly beyond the age limits of conventional luminescence-dating methods. In the past, the potential of halite as a material for optical luminescence dating had been suggested, e.g. Bailey et al., (2000); Zhang et al., (2005). However, LL may offer an additional luminescence-dating tool for routine use in geochronology but targeting the crystallization instead of heat or light exposure event. Moreover, it may enable tapping into different archives and subsurface processes where only the event of the last hydration is of interest.
In our contribution, we present the first basic design of a measurement prototype using 3D printing and preliminary experimental results of salts easily soluble in water.

References
Atari, N.A., 1980. Lyoluminescence mechanism of gamma and additively coloured alkali halides in pure water. Journal of Luminescence 21, 305–316. https://doi.org/10.1016/0022-2313(80)90009-5
Atari, N.A., Ettinger, K.V., Fremlin, J.H., 1973. Lyoluminescence as a possible basis of radiation dosimetry. Radiation Effects 17, 45–48. https://doi.org/10.1080/00337577308232596
Bailey, R.M., Adamiec, G., Rhodes, E.J., 2000. OSL properties of NaCl relative to dating and dosimetry. Radiation Measurements 32, 717–723. https://doi.org/10.1016/S1350-4487(00)00087-1
Han, W., Ma, Z., Lai, Z., Appel, E., Fang, X., Yu, L., 2014. Wind erosion on the north‐eastern Tibetan Plateau: constraints from OSL and U‐Th dating of playa salt crust in the Qaidam Basin. Earth Surf Processes Landf 39, 779–789. https://doi.org/10.1002/esp.3483
Zhang, J.F., Yan, C., Zhou, L.P., 2005. Feasibility of optical dating using halite. Journal of Luminescence 114, 234–240. https://doi.org/10.1016/j.jlumin.2005.01.009
 

How to cite: Biernacka, M. and Kreutzer, S.: Lyoluminescence: a potential tool for dating evaporites up to the Middle-Pleistocene?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21472, https://doi.org/10.5194/egusphere-egu24-21472, 2024.

AIM: We will present how virtual laser scanning (VLS), i.e., simulation of realistic LiDAR campaigns, can be key for applying machine/deep learning (ML/DL) approaches to geographic point clouds. Recent results will be shown for semantic classification and change analysis in multitemporal point clouds using exclusively open source scientific software.

MOTIVATION: Laser scanning is able to deliver precise 3D point clouds which have made huge progress in research in geosciences over the last decade. Capturing multitemporal (4D: 3D + time) point clouds enables to observe and quantify Earth surface process activities, their complex interactions and triggers. Due to the large size of 3D/4D datasets that can be captured by modern systems, automatic methods are required for point cloud analysis. Machine learning approaches applied to geographic point clouds, in particular DL, have shown very promising results for many different geoscientific applications [1,2].

METHODS & RESULTS: While new approaches for deep neural networks are rapidly developing [1], the bottleneck of sufficient and appropriate training data (typically annotated point clouds) remains the major obstacle for many applications in geosciences. Those data hungry learning methods depend on proper domain representation by training data, which is challenging for natural surfaces and dynamics, where there is high intra-class variability. Synthetic LiDAR point clouds generated by means of VLS, e.g., with the open-source simulator HELIOS++ [3], can be a possible solution to overcome the lack of training data for a given task. In a virtual 3D/4D scene representing the target surface classes, different LiDAR campaigns can be simulated, with all generated point clouds being automatically annotated. VLS software like HELIOS++ allows to simulate any LiDAR platform and settings for a given scene, which offers high potential for data augmentation and the creation of training samples tailored to specific applications. In recent experiments [1], purely synthetic training data could achieve similar performances to costly labeled training data from real-world acquisitions for semantic scene classification.

Furthermore, surface changes can be introduced to create dynamic VLS scenes (e.g., erosion, accumulation, movement/transport). Combining LiDAR simulation with automatic change analysis, such as offered by the open-source scientific software py4dgeo [5], enables to perform ML for change analysis in multitemporal point clouds [6]. Recent results show that rockfall activity mapping and classification for permanent laser scanning data can be successfully implemented by combining HELIOS++, py4dgeo and the open-source framework VL3D, which can be used for investigating various ML/DL approaches in parallel.

CONCLUSION: Expert domain knowledge (i.e., definition of proper 3D/4D scenes) and the power of AI can be closely coupled in VLS-driven ML/DL approaches to analyze 3D/4D point clouds in the geosciences. Open-source scientific software already offers all required components (HELIOS++, VL3D, py4dgeo). 

REFERENCES:

[1] Esmorís Pena, A. M., et al. (2024): Deep learning with simulated laser scanning data for 3D point cloud classification. ISPRS Journal of Photogrammetry and Remote Sensing. under revision.

[2] Winiwarter, L., et al. (2022): DOI: https://doi.org/10.1016/j.rse.2021.112772 

[3] HELIOS++: https://github.com/3dgeo-heidelberg/helios

[4] VL3D framework: https://github.com/3dgeo-heidelberg/virtualearn3d

[5] py4dgeo: https://github.com/3dgeo-heidelberg/py4dgeo

[6] Zahs, V. et al. (2023): DOI: https://doi.org/10.1016/j.jag.2023.103406

How to cite: Höfle, B., Tabernig, R., Zahs, V., Esmorís Pena, A. M., Winiwarter, L., and Weiser, H.: Machine-learning based 3D point cloud classification and multitemporal change analysis with simulated laser scanning data using open source scientific software, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1261, https://doi.org/10.5194/egusphere-egu24-1261, 2024.

We advance the characterization of landscape dynamics through analysis of point cloud time series by integrating virtual laser scanning, machine learning and innovative open source methods for 4D change analysis. We present a novel approach for automatic identification of different surface activity types in real-world 4D geospatial data using a machine learning model trained exclusively on simulated data.

Our method focuses on classifying surface activity types based on spatiotemporal features. We generate training data using virtual laser scanning of a dynamic coastal scene with artificially induced surface changes. Scenes with surface change are generated using geographic knowledge and the concept of 4D objects-by-change (4D-OBCs) [1, 2], which represent spatiotemporal subsets of the scene that exhibit change with similar properties. A realistic 3D scene modelling is essential for accurately replicating the dynamic nature of coastal landscapes, where morphological changes are driven by both natural processes and anthropogenic activities.

The Earth's landscapes exhibit complex dynamics, spanning large spatiotemporal scales, from high-mountain glaciers to sandy coastlines. The challenge lies in effectively detecting and classifying diverse surface activities with varying magnitudes, spatial extents, velocities, and return frequencies. Effective characterization of these dynamics is crucial for understanding the underlying environmental processes and their interplay with human activities. Supervised machine learning classification of surface activities from point cloud time series is challenging due to the limited availability of comprehensive and diverse real-world datasets for training and validation. Our approach combines virtual laser scanning with machine learning-based classification, enabling the generation of comprehensive training datasets covering the full spectrum of expected change patterns [3].

In our approach, the simulation of LiDAR point clouds is performed in the open-source framework HELIOS++ [4, 5]. HELIOS++ allows the flexible simulation of custom LiDAR campaigns with diverse acquisition modes and settings together with automatic annotations of artificially induced surface changes. We train a supervised machine learning model to classify synthetic 4D-OBCs into typical surface activity types of a sandy beach (e.g. dune erosion/accretion, sediment transport, etc.). Moreover, we investigate descriptors for 4D-OBCs, assessing their suitability for representing general types of surface activity (transferable between use cases) and types specific to particular surface processes.

We evaluate our model for 4D-OBC classification in terms of its capacity to discriminate surface activity types in a real-world dataset of a sandy beach in the Netherlands [6]. 4D-OBCs are extracted, classified into our target classes and validated with manually labelled reference data based on expert evaluation.

Our study showcases the efficacy of coupling virtual laser scanning, innovative open-source 4D change analysis methods, and machine learning for classifying natural surface changes [7]. Our findings not only contribute to advancing the understanding of landscape dynamics but also provide a promising approach to mitigating environmental challenges.

REFERENCES

[1] Anders et al. (2022): DOI: https://doi.org/10.5194/egusphere-egu22-4225

[2] py4dgeo: https://github.com/3dgeo-heidelberg/py4dgeo 

[3] Zahs et al. (2022): DOI: https://doi.org/10.1016/j.jag.2023.103406

[4] HELIOS++: https://github.com/3dgeo-heidelberg/helios

[5] Winiwarter et al. (2022): DOI: https://doi.org/10.1016/j.rse.2021.112772 

[6] Vos et al. (2022): DOI: https://doi.org/10.1038/s41597-022-01291-9

[7] CharAct4D: www.uni-heidelberg.de/charact4d

How to cite: Zahs, V., Höfle, B., Federer, M., Weiser, H., Tabernig, R., and Anders, K.: Automatic Classification of Surface Activity Types from Geographic 4D Monitoring Combining Virtual Laser Scanning, Change Analysis and Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1640, https://doi.org/10.5194/egusphere-egu24-1640, 2024.

The acquisition of aerial photographs for cartographic applications started in the 1930s, and more intensively after World War II. Such old, often panchromatic, imagery offers metre to sub-metre scale spatial resolution over landscapes that have significantly evolved over the decades. Before the appearance of the first digital aerial camera systems at the end of the 20^th Century, surveys were performed with analogue metric cameras, with images acquired on films or glass plates and, next, developed on photo papers. In Europe and North America, several institutions hold unique collections of historical aerial photographs having local, national and, in some cases, colonial coverages. They represent invaluable opportunities for environmental studies, allowing the comparison with today’s land use land cover, and the analysis of long-term surface displacements.

Initially, the photogrammetric processing of analogue aerial photographs would require expensive equipment, specialised operators, and significant processing time. Thanks to the digital revolution of the past two decades and the development of modern digital photogrammetric approaches, the processing of this type of image datasets has become less cumbersome, time consuming and expensive, at least in theory. In practice, this is more complex, with digitising and processing issues related to the ageing and quality of conservation of the aerial photographs, the potential distortions created during the digitising process, and the lack of ancillary data, such as, flight plans, and camera calibration reports. The limited overlap between photographs, typically 60 % and 10-20 %, along-track and across-track, respectively, make their processing with Structure-from-Motion Multi-View Stereo (SfM-MVS) photogrammetry poorly reliable to accurately reconstruct the topography and orthorectify the images. Given the fact that some collections reach up to millions of historical aerial photographs, the digitising, pre-processing, and photogrammetric processing of these images remain a challenge that must be properly tackle if we would like to ensure their preservation and large-scale valorisation.

In the present work, we describe the mass-digitising, digital image pre-processing and photogrammetric processing approaches implemented at the Royal Museum for Central Africa (RMCA, Belgium) to preserve and valorise the collection of >320,000 historical aerial photographs conserved in this federal institution. This imagery was acquired between the 1940’s and the 1980’s, over Central Africa, and mostly D.R. Congo, Rwanda and Burundi. For the digitising, a system of parallelized flatbed scanners controlled by a Linux computer and a self-developed software allows speeding-up the scanning of the entire collection in only few years. A series of Python scripts were developed and combined to allow a swift pre-processing that prepare and optimise the digitised images for photogrammetric processing. Finally, a SfM-MVS photogrammetric approach adapted to historical aerial photos is used. Examples of application for geo-hydrological hazards studies in the western branch of the East African Rift are shown.

How to cite: Smets, B., Dille, A., Dewitte, O., and Kervyn, F.: Digitising, pre-processing and photogrammetric processing of historical aerial photographs for the production of high resolution orthomosaics and the study of geohazards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2356, https://doi.org/10.5194/egusphere-egu24-2356, 2024.

Wind erosion constitutes a prominent land degradation process in regions of Hungary characterized by low annual precipitation. In these areas, it poses significant challenges to agricultural productivity and adversely impacts soil and environmental quality. Presently, human activities exert a more pronounced influence on the endangered areas of Hungary in comparison to climate-related factors. It is noteworthy that the wind erodibility of Hungarian soils not only poses a soil conservation challenge but also gives rise to economic ramifications, such as nutrient loss, as well as environmental and human health concerns. Within agricultural landscapes, wind erosion contributes to the removal and transportation of the finest and biologically active soil fractions, rich in organic matter and nutrients.

High-resolution topographic surveys have become integral for assessing volumetric changes in sand dune mobility and mapping wind erosion. While Unmanned Aerial Systems (UAS) surveys have been extensively employed for erosion rates exceeding the decimeter scale, Terrestrial Laser Scanning (TLS) surveys have demonstrated efficiency in capturing more extensive negative erosional forms, even in a vertical orientation. To enhance the field of view, a mounting framework can be implemented to elevate the TLS. However, determining centimeter-scale material displacement in flat terrain conditions remains challenging and requires an increased number of scanning positions.

To identify optimal settings for surveying centimeter-scale wind erosion magnitudes, we conducted combined multi-temporal TLS and UAS surveys at the Westsik experimental site near Nyíregyháza during the spring of 2023. This site features dune topography with a height of 6 meters. Our investigations encompassed various UAS image acquisition modes, involving different flight altitudes and camera settings, utilizing a DJI Matrice M210 RTK v2 drone and a Zenmuse X7 24 mm lens. Additionally, we generated diverse point clouds through various scanning scenarios using a Trimble X7 TLS device. In the data processing phase, we explored multiple co-registration algorithms to address the challenge of larger Root Mean Square Error (RMSE) in Digital Terrain Models (DTMs) from UAS Structure from Motion (SfM) compared to the actual wind erosion rates.

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The research is supported by the NKFI K138079 project.

How to cite: Bertalan, L., Négyesi, G., Szabó, G., Túri, Z., and Szabó, S.: Evaluating the efficacy of multitemporal TLS and UAS surveys for quantifying wind erosion magnitudes of sand dune topography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4399, https://doi.org/10.5194/egusphere-egu24-4399, 2024.

Historical aerial images, captured by film cameras in the previous century, have emerged as valuable resources for quantifying Earth's surface and landscape changes over time. In the post-war period, historical aerial images were often acquired to create topographic maps, resulting in the acquisition of large-scale aerial photographs with stereo coverage. Using photogrammetric techniques on stereo-images enables extracting 3D information to reconstruct Digital Surface Models (DSMs), and orthoimages.

This study presents a highly automated photogrammetric approach for generating nationwide DSMs for Switzerland at 1 m resolution using aerial stereo-images acquired between 1979 and 2006. The 8-bit scanned images, with known exterior and interior orientation, were processed using BAE Systems' SocetSet (v5.6.0) with the "Next-Generation Automatic Terrain Extraction" (NGATE) package for DSM generation. The primary objective of the study is to derive four nationwide DSMs for the epochs 1979-1985, 1985-1991, 1991-1998, and 1998-2006. The study assesses DSM quality in terms of vertical accuracy and completeness of image matching across different land cover types, with a focus on forest dynamics and management research.

The elevation accuracy of the generated DSMs was assessed using two reference datasets. Firstly, the elevation differences between a nationwide reference Digital Terrain Model (DTM - swissAlti3d 2017 by Swisstopo) and the generated DSMs were calculated on points classified as "sealed surface". Secondly, elevation values of the DSMs were compared to approximately 500 independent geodetic points distributed across the country. Six study areas were chosen to assess completeness, and it was calculated as the percentage of successfully matched points to the potential total number of matched points within a predefined area. This assessment was conducted for six land cover classes based on the land cover/land-use statistics dataset from the Federal Office of Statistics.

Across the entire country, the median elevation accuracy of the DSMs on sealed points ranges between 0.28 to 0.53 m, with a Normalized Median Absolute Deviation (NMAD) of around 1 m (maximum 1.41 m) and an RMSE of a maximum of 3.90 m. The elevation differences between geodetic points and DSMs show higher accuracy, with a median value of a maximum of 0.05 m and an NMAD smaller than 1 m. Completeness results reveal mean completeness between 64 % to 98 % for the classes "glacial and perpetual snow" and "sealed surfaces," respectively and 93 % specifically for the “closed forest” class.

This work demonstrates the feasibility of generating accurate DSM time series (spanning four epochs) from historical scanned images for the entire Switzerland in a highly automated manner. The resulting DSMs will be available upon publication, providing an excellent opportunity to detect major surface changes, such as forest dynamics.

How to cite: Ginzler, C., Piermattei, L., Marty, M., and Waser, L. T.: Four nationwide Digital Surface Models from airborne historical stereo-images, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5142, https://doi.org/10.5194/egusphere-egu24-5142, 2024.

Landslides are a pervasive natural hazard with significant societal and environmental impacts. In addressing the critical need for accurate landslide detection and monitoring, our previous research introduced a feature-based monitoring method enhanced by histogram analyses, straddling a middle ground between point-based and point cloud-based methods. This paper expands upon that foundation, introducing an innovative contour line extraction technique from various epochs to precisely identify areas prone to deformation. This refined focus diverges from conventional methodologies that analyze entire point clouds. By applying on regions where contour lines do not match, indicating potential ground movement, we significantly elevate the efficiency and precision of our feature-based monitoring system.

One of the principal challenges of feature-based monitoring is managing a substantial number of outliers. Our prior research tackled this issue effectively by integrating feature tracking with histogram analysis, thereby filtering these outliers from the final results. However, the process of extracting features from each patch and matching them with corresponding patches from different epochs was time-intensive.

The incorporation of contour line extraction into our workflow, using high-resolution laser scanner data, allows for a more focused and efficient analysis. We can now identify and analyze areas of landscape alteration with greater accuracy. This approach limits the application of feature tracking and histogram analysis to these critical areas, thus streamlining the process and significantly reducing computational demands. This focused methodology not only accelerates data processing but also enhances the accuracy of landslide predictions.

Our findings indicate a substantial improvement in the efficiency of landslide monitoring methods. This methodology represents a promising advancement in geospatial analysis, particularly for environmental monitoring and risk management in regions susceptible to landslides. This research contributes to the ongoing efforts to develop more effective, efficient, and accurate approaches to landslide monitoring, ultimately aiding in better informed and timely decision-making processes for hazard mitigation and risk management.

How to cite: Hosseini, K., Hummelsberger, J., Czerwonka-Schröder, D., and Holst, C.: Enhancing 3D Feature-based Landslide Monitoring Efficiency by Integrating Contour Lines in Laser Scanner Point Clouds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5670, https://doi.org/10.5194/egusphere-egu24-5670, 2024.

The permanent terrestrial laser scanning (PLS) system has opened the possibilities for efficient data acquisition with high-temporal and spatial resolution, thus allowing for improved capture and analyses of complex geomorphological changes on the Earth's surface. Accurate georeferencing of generated four-dimensional point clouds (4DPC) from PLS is the prerequisite of the following change analysis. Due to the massive data volume and potential changes between scans, however, efficient, robust, and automatic georeferencing of 4DPC remains challenging, especially in scenarios lacking signalized and reliable targets. This georeferencing procedure can be typically realized by designating a reference epoch and registering all other scans to this epoch. Addressing the challenges in targetless registration of topographic 4DPC, we propose a simple and efficient registration method called Piecewise-ICP, which first segments point clouds into piecewise patches and aligns them in a piecewise manner.

Assuming the stable areas on monitored surfaces are locally planar, supervoxel-based segmentation is employed to generate small planes from adjacent point clouds. These planes are then refined and classified by comparing defined correspondence distances to a monotonically decreasing distance threshold, thus progressively eliminating unstable planes in an efficient iterative process as well as preventing local minimization in the ICP process. Finally, point-to-plane ICP is performed on the centroids of the remaining stable planes. We introduce the level of detection in change analysis to determine the minimum distance threshold, which mitigates the influence of outliers and deformed areas on registration accuracy. Besides, the spatial distribution of empirical registration uncertainties on registered point clouds is derived based on the variance-covariance propagation law.

Our registration method is demonstrated on two datasets: (1) Synthetic point cloud time series with defined changes and transformation parameters, and (2) a 4DPC dataset from a PLS system installed in the Vals Valley (Tyrol, Austria) for monitoring a rockfall. The experimental results show that the proposed algorithm exhibits higher registration accuracy compared to the existing robust ICP variants. The real-time capability of Piecewise-ICP is significantly improved owing to the centroid-based point-to-plane ICP and the efficient iteration process.

How to cite: Yang, Y., Czerwonka-Schröder, D., and Holst, C.: Piecewise-ICP: Efficient Registration of 4D Point Clouds for Geodetic Monitoring, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5674, https://doi.org/10.5194/egusphere-egu24-5674, 2024.

Our study focuses on the geologically, topographically, and oceanographically complex region of Disko Bay in West Greenland. Disko Bay is also considered a marine biodiversity hotspot in Greenland. Given the impact of commercial fishing on seafloor integrity in the area, seafloor habitats studies are crucial for sustainable use of marine resources. One of the key fishery resources in Greenland, as well as in the North Atlantic Ocean, is northern shrimp.

In this study we analyzed multiple (1) monitoring datasets from 2010 to 2019, including data from shrimp and fish surveys, commercial shrimp fishery catches, satellite chlorophyll data, and (2) seafloor models, encompassing high-resolution (25 x 25 m) multibeam data with a low-resolution (200 x 200 m) IBCAO grid. Using multivariate regression analysis and spatial linear mixed-effect model we assessed the impact of physical (water depth, bottom water temperature, sediment type), biological (chlorophyll a, Greenland halibut predation), and anthropogenic factors (shrimp fishery catch and effort) on shrimp density in the area. The resulting high-resolution predictive model of northern shrimp distribution in Disko Bay is the first model of this kind developed for an Arctic area.

Our findings reveal that shrimp density is significantly associated with static habitat factors, namely sediment type and water depth, explaining 34% of the variation. The optimal shrimp habitat is characterized by medium-deep water (approximately 150-350 m) and mixed sediments, primarily in the north-eastern, south-eastern, and north-western Disko Bay. This pioneering study highlights the importance of seafloor habitat mapping and modeling, providing fundamental geophysical knowledge necessary for long-term sustainable use of marine resources in Greenland.

The developed high-resolution model contributes to a better understanding of detailed patterns in northern shrimp distribution in the Arctic, offering valuable insights for stock assessments and sustainable fishery management. This novel approach to seafloor habitat mapping supports the broader goal of ensuring the responsible utilization of marine resources, aligning with principles of environmental conservation and fisheries management. Our work serves as a foundation for ongoing efforts to balance economic interests with the preservation of marine ecosystems, fostering a harmonious coexistence between human activities and the fragile Arctic environment.

How to cite: Krawczyk, D., Vonnahme, T., Burmeister, A.-D., Maier, S., Blicher, M., Meire, L., and Nygaard, R.: Arctic puzzle: pioneering a shrimp habitat model in topographically complex Disko Bay (West Greenland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5757, https://doi.org/10.5194/egusphere-egu24-5757, 2024.

The evolution of technology, particularly the integration of Unmanned Aerial Systems (UAS), earth observation datasets, and historical data such as aerial photographs, stand as fundamental tools for comprehending and reconstructing surface evolution and potential environmental changes. In addition, the active geodynamic phenomena in conjunction with climate crisis and the increasing frequency of extreme weather phenomena can cause abrupt events such as rockfalls and landslides, altering completely the morphology on both small and large scales.

This study deals generally with the temporal evolution of landscapes and specifically focuses on the detection and quantification of a significant rockfall event that occurred at Kalamaki Beach on Zakynthos Island, Greece – a very popular summer destination. Utilizing UAS surveys conducted in July 2020 and July 2023, this research revealed a rockfall that has significantly altered the coastal morphology. During this period, two severe natural phenomena occurred, one of which could potentially be the cause of this rockfall event. Initially, the Mediterranean hurricane (‘medicane’) ‘Ianos’ made landfall in September 2020, affecting a large part of the country including the Ionian Islands. The result was severe damage to property and infrastructures, along with human casualties, induced by intense precipitation, flash flooding, strong winds, and wave action. Second, in September of 2022, an M_L=5.4 earthquake struck between Cephalonia and Zakynthos Islands in the Ionian Sea, triggering considerable impact in both islands. The study employs satellite images postdating these natural disasters, to detect the source of the rockfall in Kalamaki Beach. Additionally, historical analog aerial images from 1996 and 2010 were used as assets for understanding the surface’s evolution. For the quantitative analysis, we applied 3D semi-automated change detection techniques such as the M3C2 algorithm, to estimate the volume of the rockfall.

The results provide insights into the complex interplay between natural disasters and geological processes, shedding light on the dynamic nature of landscapes and the potential implications for visitor-preferred areas.

This research not only contributes to our understanding of landscape evolution but also underscores the importance of integrating modern and historical datasets to decipher the dynamic processes shaping the Earth's surface. The methodology proposed, serves as a valuable approach for assessing and managing geological hazards in coastal regions affected by both climatic events and geodynamic activities.

How to cite: Konsolaki, A., Vassilakis, E., Kotsi, E., Diakakis, M., Mavroulis, S., Petrakis, S., Filis, C., and Lekkas, E.: A Time-Series Analysis of Rockfall Evolution in a Coastal Region Using Remote Sensing Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10361, https://doi.org/10.5194/egusphere-egu24-10361, 2024.

Understanding the complex processes occurring at the soil surface is challenging due to the intricate spatial variability and dynamic nature of these processes. An effective tool for elucidating these phenomena is three-dimensional (3D) reconstruction, which employs advanced imaging technologies to create a comprehensive representation of the soil surface at high spatial resolution, often at the mm-scale. Three-dimensional reconstruction techniques are increasingly available to scientists in the fields of soil science, geomorphology, hydrology, and ecology and many studies have employed these novel tools to advance understanding of surface processes. Much of the data being collected in these studies are however not interoperable, i.e., 3D data from one study may not be directly combined with 3D data from other studies thus limiting the ability of researchers to advance process understanding at a broader scope. The limited interoperability of existing data is due in part to the fact that 3D surface reconstruction data are influenced by many factors including experimental conditions, intrinsic soil properties and accuracy and precision limits of the 3D reconstruction technique used. These ancillary data are crucial to any broad-scope efforts that leverage the increasing number of 3D datasets collected by scientists across disciplines, geographic regions, and experimental conditions. We have developed a relational database that archives and serves ancillary data associated with published high-resolution 3D data representing soil surface processes. This presentation introduces the structure of the database with its required and optional variables. We also provide analytics on the currently available records in the database and discuss potential applications of the database and future developments.

How to cite: Nouwakpo, K., Eltner, A., Candido, B., Li, Y., Wacha, K., Nichols, M., and Washington-Allen, R.: A database for ancillary information of three-dimensional soil surface microtopography measurements., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10373, https://doi.org/10.5194/egusphere-egu24-10373, 2024.

Rural landscapes inherited from the past are marked by a strong interaction between man and nature, a relationship rooted in a long history that testifies to the importance of the landscape as one of the most historically representative expressions of a country's cultural identity.

In this broad context, olive groves markedly characterize the agricultural landscape of many European rural areas, particularly in the Mediterranean region. Along with other rural landscapes, they form a semi-natural environment that can contribute to biodiversity conservation, soil protection and ecosystem resilience.

In addition to the global increase in temperatures, the main threats affecting these agrarian landscapes include the abandonment of traditional practices and the intensification of cultivation through the installation of irregular, intensive and overly dense planting beds.

The Land Cover classification and change-detection can provide useful indications for the restoration, conservation, and enhancement of olive groves

The objective of this work was to identify , rural landscapes in the Lazio region with characteristics of historical interest and determine their level of conservation. In particular, it was investigated the olive landscape of Cures (historic province of Sabina) trough a multi-temporal analysis of literature and cartographic information (e.g. orthophotos from the Italian Aeronautical Group flight of 1954)

The technique concerns the VASA (Historical Environmental Assessment) methodology, which allows the temporal evaluation of a given landscape and can inform on how agricultural practices and land use have changed over time.

Softwares  Collect Earth and Google Earth were employed to manipulate the historical series of high-resolution satellite images and implement photointerpretation. The coverage of identitied land units  was then estimated to address the configuration of the target landscape.

Landscape evolution over time was achieved by overlaying the 1954 and 2022 land use polygons, resulting in a merging database, in which an evolutionary dynamic was associated with each land use change.

The approach generated in-depth insights on the significant elements of the CURES olive landscape and informed on the dynamics of the area in relation to the risk of their disappearance, making it possible to identify what are the "landscape emergencies," i.e., the land uses that have seen the most̀ reduction in their area.

The methodologies employed have proven reliability in improving the knowledge ng target landscapes.  It might be useful to promote  sustainable agricultural practices for better preservation and management of rural environments so that cultural traditions can be preserved as well, and the environmental balance of the agrarian land can be maintained.

How to cite: Cuccaro, V. C., Di Giovannantonio, C., Pica, G., Malatesta, L., and Attorre, F.: Employng satellite immagery interpretation tools to detect land-use land-change dynamics in Italian historical rural landscapes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11949, https://doi.org/10.5194/egusphere-egu24-11949, 2024.

How to cite: Belart, J. M. C., Gunnarson, S., Berthier, E., Dehecq, A., Jóhannesson, T., Hannesdóttir, H., and Baxter, K.: Unleashing the archive of aerial photographs of Iceland, 1945-2000. Applications in geosciences , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12105, https://doi.org/10.5194/egusphere-egu24-12105, 2024.

The water level and discharge of river are crucial parameters to understand the variance in riverbed scour. The detail behavior of scouring can be studied by the hydraulic simulation. The grain-size distribution of riverbed is also one of crucial parameter for modeling. Thus, how to investigate the grain-size of riverbed efficiently and swiftly is the urgent issue. However, the conventional measurement methods including Wolman counts (particles sampled at a fixed interval) which are a long and laborious task cannot survey the grain-size efficiently in the large area. In recent years, with an advantage of image segmentation and recognition has been applied to the investigation of grain-size, for example, capturing images through UAV and generating orthoimage is one of commonly used image technique. Although above the method can investigate the grain-size in the large area, it does not provide the information in the field immediately. Hence, a recent study developed the low-cost portable scanner to obtain the information of grain-size distribution in the field. However, the calibrating parameters of camera (e.g., height camera capture) are necessary before survey, and the uncertainties in calculation of image resolution will significantly affect the accuracy of grain-size analysis. Therefore, this study provides the additional algorithm to analyze the grain-size by using RGB-D image as inputs. The application of RGB-D can be categorized into two-dimensional (2D) and three-dimensional (3D) spaces. In a case of 2D, it integrates depth information with traditional RGB image processing to separate the grain-size of riverbed from the background (e.g., bottomland). Furthermore, depth information is also applied for grain-size edge detection. In a case of 3D, the collected RGB-D image information is transformed into point cloud data, then extract 3D features of grain particle by Deep learning, specifically PointNet. Our study demonstrates that clustering of 3D features can achieve the automatic identification of particle. The grain-size of particle can also be estimated by fitting 3D ellipsoid geometry. In the end, results show the grain-size distribution curves with the RGB、RGB-D、PointNet recognition, and compare with the true observations. 3D image information provides the cloud points of grain object, leading the possibility of estimating the 3D geometric morphology of the object. Our study successfully overcomes the limitations of conventional RGB-based process, which could only capture size and shape information in 2D planar. RGB-D-based image recognition, is an innovative technique for the hydraulic problem, not only advances survey efficiency but also addresses the intricate steps required for field investigations.

Key words: Riverbed grain size, RGB-D image, Point cloud, Deep Learning

How to cite: Chen, B. R. and Chao, W. A.: A point-cloud deep learning model based on RGB-D images: Application of riverbed grain size survey, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14087, https://doi.org/10.5194/egusphere-egu24-14087, 2024.

Examining deposition and erosion dynamics during the late Pleistocene and Holocene is crucial for gaining insights into soil development, erosion, and climate fluctuations. This urgency intensifies as arable lands face escalating degradation rates, particularly in arid and semi-arid environments. Nevertheless, as the destructive nature of erosional processes allows only for short-term studies, long-term processes in these regions are insufficiently investigated. In that respect, the ancient agricultural installations in the arid Southern Levant offer distinctive and undisturbed evidence of long-term land dynamics. Constructed on a late Pleistocene fluvial-loess section during the 3rd-4th CE and abandoned after 600-700 years, these installations record sediment deposition, soil formation, and erosion processes. The challenge is to trace and quantify these processes based on their current state. In this presentation, we demonstrate how the use of 3D point cloud data enables us to follow past geomorphological processes and reconstruct trends and rates. Utilizing data gathered in the immediate vicinity of the UNESCO World Heritage Site of Avdat (Israel), we illustrate how these point clouds comprehensively document the history of soil dynamics in the region. This encompasses the initial erosion phase, subsequent soil aggradation processes resulting from anthropogenic interruption, and the ongoing reinstated erosion. The unique setting, which uncovers the different fluvial sections, together with the detailed 3D documentation of the site, allows us to develop means for the reconstruction of the natural environment in each of the erosion/siltation stages. Therefore, by utilizing the obtained data, we can recreate the site during its developmental stages till the present day. Furthermore, we utilize terrestrial laser scan data sequence acquired in the past decade (2012-2022) to compute current erosion rates. These are then used to determine past rates, enabling inferences about the climatic conditions prevalent in the region over the last millennium. The in-depth examination of these installations provides valuable insights into approaches for soil conservation, sustainable desert living, and strategies to safeguard world-heritage sites subjected to soil erosion. As the global imperative to address soil erosion intensifies, this case study gains heightened relevance.

How to cite: Arav, R., Filin, S., and Avni, Y.: Using current 3D point clouds as a tool to infer on past geomorphological processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14680, https://doi.org/10.5194/egusphere-egu24-14680, 2024.

Our research explores the potential of historical images of Antarctica for change detection in 2D and 3D. We
make use of the TMA Archive, a vast collection of over 330,000 black and white photographs of Antarctica taken
between 1940 to 1990. These photographs, available in both nadir and oblique, are systematically captured
from airplanes along flight paths and offer an unprecedented historical snapshot of the Antarctic landscape.
Detecting changes between past and present observations provides a unique insight into the long-term impact
of changing climate conditions on Antarctica’s glaciers, and their dynamical response to ice shelf weakening and
disintegration. Furthermore, it provides essential validation data for ice modelling efforts, thereby contributing
to reducing the uncertainties in future sea level rise scenarios.

In previous work, we applied semantic segmentation to these images [1]. By employing classes derived from this
segmentation, we can focus on features of interest and exclude images with extensive cloud coverage, enhancing
the accuracy of change analyses. In the next step, we geo-referenced the images: We assigned the images to
their actual position, scaled them to their true size, and aligned them with their genuine orientation. This
presents novel opportunities for detecting environmental changes in Antarctica, particularly in the retreat of
glaciers and sea ice.

Furthermore, the combination of these two steps allows for the first time a large scale reconstruction of these
images in 3D through Structure from Motion (SfM) techniques, which enables further multidimensional change
detection by comparing historical 3D models with contemporary ones. Due to the high number of images,
manual processing is impractical. Therefore, we are investigating the possibility of automatizing this process.
We utilize MicMac, an open-source software developed by the French National Geographic Institute for the
creation of the 3D models. Its high modularity allows for necessary customizations to automate the SfM
process effectively. Further adaptions are required due to the poor image quality and monotonous scenery. By
comparing historical 3D models with contemporary ones, we can assess alterations in elevation due to factors
such as glacial isostatic adjustments and glacier retreat.

We have already employed geo-referenced images for detecting changes on the Antarctic peninsula and are in the
process of creating initial 3D models. Our presentation will outline the workflow we developed for this process
and showcase the initial results of the change detection, both in 2D and 3D formats. This approach marks a
significant step in understanding and visualizing the impacts of climate change on the Antarctic landscape.

Acknowledgements
This work was funded by NWO-grant ALWGO.2019.044.

References
[1] F. Dahle, R. Lindenbergh, and B. Wouters. Revisiting the past: A comparative study for semantic segmen-
tation of historical images of Adelaide Island using U-nets. ISPRS Open Journal of Photogrammetry and
Remote Sensing, 11:100056, 2024.

How to cite: Dahle, F., Lindenbergh, R., and Wouters, B.: Utilizing historical aerial imagery for change detection in Antarctica, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15439, https://doi.org/10.5194/egusphere-egu24-15439, 2024.

How to cite: Guerit, L., Steer, P., Leroy, P., Lague, D., Filipov, D., Jakubinsky, J., Petrovic, A., and Nikolova, V.: Classification and segmentation of 3D point clouds to survey river dynamics and evolution , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15896, https://doi.org/10.5194/egusphere-egu24-15896, 2024.

The Maltese coasts extend for approximately 273km, representing a notable resource for the country and of one of its pillar economies, the tourism sector. Natural processes and anthropic interventions continue to threaten Malta's coastal morphology, shaping its landscape and triggering soil erosion phenomena. Therefore, many research projects (Colica et al., 2021, 2022 and 2023) have concentrated their work on the investigation and monitoring of the instability of cliffs and the erosion of pocket beaches. The results of such activities can be widely disseminated and shared with expert and non-expert users through web mapping, which has only been used in a very limited way in collaborative coastal management and monitoring by different entities in Malta. This study describes the performance of a WebGIS designed to disseminate the results of innovative geomatic investigations for monitoring and analyzing erosion risk, performed by the Research and Planning Unit within the Public Works Department of Malta. While aiming to include the entire national coastline, three study areas along the NE and NW regional coasts of the island of Malta have already been implemented as pilot cases. This WebGIS was generated using ArcGIS pro software by ESRI and a user-friendly interactive interface has been programmed to help users view in 2D and 3D, satisfying both multi-temporal and multi-scale perspectives. It is envisaged that through further development and wider dissemination there will be a stronger uptake across different agencies involved in coastal risk assessment, monitoring and management.

References

Colica, E., D’Amico, S., Iannucci, R., Martino, S., Gauci, A., Galone, L., ... & Paciello, A. (2021). Using unmanned aerial vehicle photogrammetry for digital geological surveys: Case study of Selmun promontory, northern of Malta. Environmental Earth Sciences, 80, 1-14.

Colica, E. (2022). Geophysics and geomatics methods for coastal monitoring and hazard evaluation.

Colica, E., Galone, L., D’Amico, S., Gauci, A., Iannucci, R., Martino, S., ... & Valentino, G. (2023). Evaluating Characteristics of an Active Coastal Spreading Area Combining Geophysical Data with Satellite, Aerial, and Unmanned Aerial Vehicles Images. Remote Sensing, 15(5), 1465.

How to cite: Colica, E., Fenech, D., Gauci, C., and Buhagiar, G.: Integrating structure-from-motion photogrammetry with 3D webGIS for risk assessment, mapping and monitoring of coastal area changes in the Maltese archipelago, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16939, https://doi.org/10.5194/egusphere-egu24-16939, 2024.

Jeremie' Tranchant¹, Daniel Fenech¹, Christopher Gauci¹, Daniela Ghirxi¹, Ines Felix Martins¹, Emanuele Colica¹, George Buhagiar¹

¹  Research and Planning Unit, Ministry for Transport, Infrastructure and Public Works, Project House, Triq Francesco    Buonamici, Floriana, FRN1700, Malta

The assessment of coastal erosion through shoreline change analysis, is an exercise of national utility undertaken in many countries. The Maltese Islands are particularly vulnerable to coastal erosion given the economic value of coastal activities and their high ratio of coast-to-land surface. The integration of historical cartographic material is often used to hindcast shoreline change across long periods of time, as well as to model future erosion rates. The Public Works Department have produced detailed 1:2500 maps of Malta in collaboration with the British Ordnance Survey from the end of the 19th century to 1957, however these maps have never been scientifically assessed. The initial research carried out evaluated the usefulness of the two oldest 25-inches Maltese maps series (early 20th century and 1957) for shoreline change analysis.  The two series were digitised, georeferenced, and compared in a GIS environment to assess their differences. The inaccuracies of the original drawings, absent shoreline indicators, and the absence of a geographic coordinate system (datum and projection) were identified as limitations for their use in evaluating small gradual changes, but were ideal for the identification of stochastic, large-scale historic erosion events using difference maps. This assessment showed that the two series are highly congruous and any changes between the two series are largely attributed to changes in infrastructure. There were, however, minor exceptions and these need to be explored on a case-by-case basis. These methods and the insights garnered from their production will function as scientific steppingstones towards developing a holistic coastal erosion national monitoring program.  

How to cite: Fenech, D., Tranchant, J., Gauci, C., Ghirxi, D., Felix-Martins, I., Colica, E., and Buhagiar, G.: Evaluating Ordnance Survey sheets (1890s – 1957) for shoreline change analysis in the Maltese Islands , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17822, https://doi.org/10.5194/egusphere-egu24-17822, 2024.

The European Water Framework Directive (WFD), adopted in 2000, set out requirements for a
better understanding of aquatic environments and ecosystems. In 2006, following the transposition of
the WFD into French law (LEMA), France began work on a field protocol for the geomorphological
characterization of watercourses, as part of a partnership between the Centre National de la Recherche
Scientifique (CNRS) and the Office Français de la Biodiversité (OFB). This protocol, known as "Carhyce"
(For « River Hydromorphological Caracterisation »), has been tested, strengthened and approved over
the last 15 years at more than 2500 reaches. It consists of collecting standardised qualitative and
quantitative data in the field, essential for the caracterisation of a watercourse: channel geometry,
substrate, riparian vegetation... However, certain rivers that are difficult to survey (too deep or too
wide) pose problems for data collection.
To address these issues, and to extend the analysis to a wider scale (full river section), using
remote sensing, and in particular LiDAR data, was considered. The major advantages of LiDAR over
passive optical sensors are better geometric accuracy and especially under vegetation. For a long time,
LiDAR data rarely exists at national scale with data density similar to passive imagery. Today, the French
LiDAR HD dataset (10 pulses per meter square) program run by the French mapping agency offers an
unprecedented amount of data at this scale. Thanks to them, a national 3D coverage of the ground can
be used, and numerous geomorphological measurements can be carried out on a more or less large
scale. This is the case for hydromorphological parameters such as water level and width.
The aim of this study is therefore to use this high-density lidar to automatically determine the
hydromorphological parameters sought in the Carhyce protocol. In particular, we have developed a
lidar-based algorithm to reconstruct the topography from point cloud and automatically identify the
bankfull level at reach scale. Designed to be applicable to every French river, the method must be
robust to all river features such as longitudinal slope, width, sinuosity, multi-channel etc... For
validation purposes, the bankfull geometry calculated by the algorithm has been compared with field
measurements at some twenty Carhyce stations across France. To determine the test stations, we
looked for the diversity of situations in terms of river characteristics describe above to observed the
influence of this features on the results.

How to cite: Rétat, A., Thommeret, N., Gob, F., Depret, T., Bailly, J.-S., Lespez, L., and Kreutzenberger, K.: Automatic detection of river bankfull parameters from high density lidar data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21396, https://doi.org/10.5194/egusphere-egu24-21396, 2024.

Uncrewed Aerial Vehicles (UAVs) are increasingly employed for glacier monitoring, particularly for small to medium-sized glaciers. The UAVs are mainly used to generate high-resolution Digital Elevation Models (DEMs), delineate glacier areas, determine surface velocities, and map supraglacial features. In this study, we utilise UAVs across various sites in the Alps and the Tien Shan (Central Asia) to monitor the mass balance of glaciers. We present a workflow for calculating the annual geodetic mass balance and obtaining the surface mass balance using the continuity-equation method. Our results demonstrate generally a close alignment between the determined mass balances and those obtained through traditional glaciological methods involving intensive fieldwork. We show that utilising UAV data reveals significantly more spatial details, such as the influence of debris and collapsing ice caves, which are challenging to capture using conventional methods that strongly rely on interpolation and extrapolation. This underscores the UAV's significance as a valuable add-on tool for quantifying annual glacier mass balance and validating glaciological assessments. Drawing on our experience in on-site UAV glacier surveys, we discuss the methodology's advantages, disadvantages, and potential pitfalls. 

How to cite: Van Tricht, L., Zekollari, H., Huss, M., Huybrechts, P., and Farinotti, D.: UAV’s to monitor the mass balance of glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22358, https://doi.org/10.5194/egusphere-egu24-22358, 2024.

Riverscapes in arid and semi-arid environments serve as crucial archives, enabling us to understand the landscape evolution and the active and fossil geomorphological processes that shape the Earth's surface. Such environmental contexts are generally wide, and these settings are routinely investigated with remote sensing tools. We selected two distinct study areas from the south-eastern margin of the Arabian Peninsula (Sultanate of Oman) to detect climate and tectonic imprints over landform development: 1) Jebel Akhdar (JAK), and its surrounding areas, located in the Al-Hajar Mountains (to the North), is a wide anticline formed by the Late Cretaceous obduction of the Semail Ophiolite and the associated time-equivalent tectonics, followed by the Cenozoic tectonic events; and 2) Jebel Qara (JQA), situated in the Dhofar Mountains (to the South), is placed along the Gulf of Aden transform margin, featuring transtensional faults giving rise to stepped escarpments and grabens. The extant landscapes of both regions are characterized by a network of narrow and deep canyons that incised limestone massifs, while the surrounding plain areas show the development of important alluvial fan systems.

The application of remote sensing is essential for investigating the development of fluvial systems at a regional scale, combined with field survey to validate specific sites of interest, thereby understanding the geomorphological evolution at various scales. Specifically, remote sensing techniques include the processing of satellite imagery and the comparison with the available historical imagery and maps to detect changes in geomorphic processes. Remote sensing and field survey allow the recognizing of different geomorphological features; the dominant ones are represented by elements and landforms related to structural setting, fluvial activity, and karst processes. The associations of the abovementioned landforms make it possible to assess the structural influence on drainage and karstic network development. Data collected from remote sensing implements the geomorphometric quantification of geomorphological processes, mostly considering changes in topography and river network analyses. The most meaningful morphometric indices applied (such as drainage divide stability, normalized steepness index, knickpoint detection, and swath profiles…) suggest their values strongly vary along faults in JAK, highlighted even with the alignment of knickpoints; while, in JQA, values show little changes in correspondence of faults and knickpoints are controlled both by karst and structural settings. In this way, the combination of remote sensing and morphometrical analyses permits to quantify the central role of litho-structural influence on the development of riverscapes in the south-eastern Arabian Peninsula. This approach facilitates the identification of the primary geomorphological processes that have shaped the landscape in arid and semi-arid contexts of the Sultanate of Oman, making it a versatile method that can be applied to understand the riverscapes evolution processes in analogous regions.

How to cite: Pezzotta, A., Marinoni, A., Al Kindi, M., Zucali, M., and Zerboni, A.: Remote sensing and geomorphometry application in riverscapes evolution in the south-eastern Arabian Peninsula (Sultanate of Oman), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-196, https://doi.org/10.5194/egusphere-egu24-196, 2024.

Terrestrial Laser Scanning (TLS) systems have been refined to automatically and continuously scan defined areas with high temporal resolution (sub-hourly), leading to the development of Permanent Laser Scanning (PLS). This temporal resolution requires the development of new methods for efficient extraction of change information. The creation of labeled 4D point clouds (3D+time), classified by surface change type, remains time-consuming. This hinders the evaluation of change detection methods and the training of machine learning (ML) and deep learning (DL) models.

This study explores how synthetic 4D point clouds can be effectively utilized for detecting and classifying spatiotemporal changes. We combine simplified process path simulations, simulated PLS, and change detection methods (e.g. M3C2) [1]. This combination is used to automatically evaluate calculated distances compared to a pre-defined reference. It also generates labeled 4D training datasets for ML/DL approaches.

We adapted the Gravitational Process Path model (GPP) [2] to create gravity-influenced process paths for our PLS simulations. Utilizing these paths, we simulate two different scenarios, 1) including a forest situated on top of a large landslide and 2) an outcrop with rockfall activity. For the forest scenario, a constant velocity is applied to each tree to simulate slope movement. The velocity of the objects in the rockfall scene is determined by the GPP model. Dynamic 3D scenes are generated from these scenarios and used as input for Virtual Laser Scanning (VLS). Realistic simulation of LiDAR surveys (of these virtual scenes) is achieved by using the open-source simulator HELIOS++ [3]. This workflow allows for the determination of the accurate position of each object at any given time. It provides reference data that is usually unavailable in real data acquisitions. In the rockfall scenario, M3C2 distances are calculated, and areas of similar change are clustered. For the forest located on the landslide, 2D and 3D displacement vectors are derived from the displacement of the tree trunks. These changes are then compared to the actual change occurring between epochs. Furthermore, the time steps between each epoch can be chosen arbitrarily, enabling the exploration of various scenarios and processes using labeled point clouds at any temporal resolution.

Preliminary results suggest that this workflow can assist in determining the scan resolution required to detect changes of a specific size and magnitude. We establish a simulation-based error margin for each method used by comparing the results to the reference data. This enables direct evaluation of method performance during implementation.

We demonstrate the potential of combining process simulation and laser scanning simulation for resource efficient planning of TLS and PLS campaigns, geographically sound generation of dynamic point clouds, the evaluation of change detection and quantification methods, and generating labeled point clouds as training data for 4D ML/DL methods. 

References:
[1] py4dgeo: https://github.com/3dgeo-heidelberg/py4dgeo
[2] Wichmann, V. (2017): https://doi.org/10.5194/gmd-10-3309-2017.
[3] Winiwarter, L. et al. (2022): https://doi.org/10.1016/j.rse.2021.112772. 

How to cite: Tabernig, R., Zahs, V., Weiser, H., and Höfle, B.: Simulating 4D scenes of rockfall and landslide activity for improved 3D point cloud-based change detection using machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1613, https://doi.org/10.5194/egusphere-egu24-1613, 2024.

Landform classification and mapping provide fundamental data for Earth science research, natural resource management, environmental monitoring, urban planning, and various other domains. Despite the availability of DEMs with 1-arc second resolution, global-scale studies on landform classification and mapping are inconsistent in terms of general classification systems and methods.

Landforms represent not only assemblages of morphological characteristics but also encompass the human understanding of the Earth, which is constrained by the nature and scale of quantitative analysis. Here, we propose a novel framework for global landform mapping to significantly improve the quantitative evaluation of geomorphological features.

The proposed framework incorporates geomorphological ontology that takes account of their conceptualization to construct classified objects. We propose the accumulated slope (AS) and mountain uplift index (MUI) to emphasize the integrity and continuity of geomorphological units, providing more precise results compared to traditional methods. Aggregating local terrain features into global metrics, AS effectively overcomes the potential negative influence of increased resolution on landform integrity. MUI aligns better with human perception of mountainous morphology and surpasses the limitations of window-based computing.

In presenting the new framework, we have developed and made available a public dataset, Global Basic Landform Unit (GBLU), which incorporates a comprehensive set of objects that constitute the range of landforms on Earth. In emphasizing the integration of classification with quantitative analysis, GBLU highlights the connection between natural objects and human understanding in geomorphology and the Earth sciences. The GBLU outperforms previous datasets (the basic landform classification and global mountain assessment) in expressing landform details. GBLU can be downloaded at https://geomorph.deep-time.org. It serves as a valuable resource in facilitating a deeper understanding of landform spatial distribution and evolution, and supporting research in a diverse range of fields.

How to cite: Yang, X., Zhou, C., Li, S., Ma, J., Chen, Y., Zhou, X., Li, F., Xiong, L., Tang, G., and Meadows, M.: Incorporating ontological characteristics for global landform classification based on 30 meters DEM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4207, https://doi.org/10.5194/egusphere-egu24-4207, 2024.

The influence of temperature as a key factor in slope stability, particularly in temperate regions, remains insufficiently explored. This study investigates the thermo-hydro-mechanical (THM) response of expansive soils, focusing on the thermally-induced activity in clay landslides.

Establishing a representative thermal variable for broad-scale assessments poses challenges due to material heterogeneities and the intricate nature of THM processes. Our research employs landslide spatial modelling in Italy, concentrating on clay-rich areas with shallow landslides on gentle slopes. Utilizing geo-lithological and geological maps and the Italian National Inventory (IFFI), we apply a Generalized Additive Model (GAM) based on slope units to capture nonlinearities in the temperature-shear strength relationship. A decade-long dataset of Land Surface Temperature (LST) from MODIS, accessible in Google Earth Engine, serves as a key input.

The study produces spatial probability maps for clay deposits across Italy, revealing a positive correlation between landslide occurrence and LST on warmer, gentle slopes, especially in Southern Italy. This aligns with the observation that higher temperatures reduce soil and water viscosity, amplifying shear creep rates in clay-rich materials. By elucidating the temperature-slope stability relationship, this study contributes to understanding landslide dynamics in temperate climates, facilitating the development of effective risk recognition strategies.

How to cite: Loche, M. and Scaringi, G.: Exploring Temperature-Shear Strength Dynamics: A Spatial Modelling Approach for Clay Landslide Susceptibility in Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5190, https://doi.org/10.5194/egusphere-egu24-5190, 2024.

The negative feedback between relief formation due to valley incision, increasing topographic stress towards a critical stress state dependent on rock strength, and consequently relief-destroying (and stress-reducing) landslides determines the geometry of alpine landscapes. Hence, the computation of topographic stresses for entire mountain massifs is crucial to identify potential landslide hotspots at steep landforms close to rock failure, determining the maximum strength of rocks and rock sequences at the mountain scale, and explaining contrasting geometries of alpine landscapes in dependence on the prevailing rock types. Traditional 2D stress and displacement calculations on valley cross-sections tend to oversimplify the complicated stress pattern, particularly where valleys converge or around ridges and peaks. 3D stress calculations based on standard finite element methods are computationally expensive and not feasible for entire mountain massifs at a reasonable expense.

Our study addresses this limitation by employing a novel three-dimensional approach, utilizing the Marching Volume Polytopes Algorithm for mesh generation and the Finite Cell Method as an alternative to the widely used finite element method. Incorporating an octree-like structure and advancing-front meshing techniques, the Marching Volume Polytopes Algorithm accurately represents given surface data through a tetrahedral mesh. In the Finite Cell Method representing a fictitious domain approach, the difficulty of generating adequate grids for physical domains with complicated geometry is transformed into the problem of specifying an adequate integration scheme for the finite cells and thus saving degrees of freedom. The computational efficiency of our approach is particularly advantageous when dealing with equidistant grids such as digital elevation models for mesh generation.

In a first study, we use our model to compute the 3D topographic stress distribution for the three Austrian UNESCO Global Geoparks known for over-steepened valley flanks and high landslide activity. Initial results show high shear stress maxima occurring predominantly at over-deepened glacial valleys bordered by rock faces, with stress maxima at valley flanks but also at or slightly below the valley floors. Unexpected stress patterns occur in areas with a complicated landscape geometry, where valleys converge, or intersecting ridge lines form pyramid peaks. Lithological contrasts of the investigated mountain massifs are reflected in very different stress patterns, with shear stress maxima showing the highest values in carbonate-dominated units.

In addition to local topographic metrics, the spatial distribution of observed landslides and the rock types that occur, modelled topographic stresses provide a new data set for assessing landslide potential. Beyond that, modeling topographic stresses of entire mountain massifs offers new insights into the evolution of alpine landscapes in the competition between relief-forming and relief-destroying processes.

How to cite: Haunsperger, V., Robl, J., Schröder, A., and Hergarten, S.: Three-Dimensional Stress Analysis of Mountain Ranges: A Novel Approach Using Marching Volume Polytopes Algorithm and Finite Cell Method , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6250, https://doi.org/10.5194/egusphere-egu24-6250, 2024.

Mapping benthic reefs at high resolution and accuracy is vital for the management and conservation of coral habitats. Optical remote sensing data has emerged as a valuable tool for large-scale reef mapping in the past decades, with numerous data sets and methods being utilised and developed. In this study, we present a comprehensive comparison of optical remote sensing based bathymetry and benthic mapping methods. We use different optical data including WorldView-2 stereo and Sentinel-2 imagery to map the water depths of coral reef areas in the Xisha region of the South China Sea. Bathymetry data derived from photogrammetric and linear regression methods are compared to the reprocessed Ice, Cloud and land Elevation Satellite-2 (ICESat-2) data. We find that the linear regression method (root-mean-square-error, RMSE=0.60 m) outperforms photogrammetry (RMSE=1.02 m), and the higher resolution WorldView-2 data yields less systematic biases than Sentinel-2 data. Considering that water depths reflect changes in temperature and light, which are critical factors influencing coral reef distribution, we propose to use satellite-derived bathymetry as a feature for coral reef classification. We demonstrate that combining topography and spectral information can improve the overall mapping accuracy, particularly for compositions characterised by sharp boundaries.

How to cite: Liu, Y., Zhou, Y., and Yang, X.: Bathymetry derivation and slope-assisted benthic mapping using optical satellite imagery in combination with ICESat-2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7114, https://doi.org/10.5194/egusphere-egu24-7114, 2024.

Airborne Light Detecting and Ranging (LiDAR) surveys became essential in tracking the evolving coastal landscapes of Mecklenburg-Vorpommern on the Baltic Sea for more than one decade, producing a data series of Digital Terrain Models (DTMs) crucial for estimating coastal erosion along the exposed cliffs. Although change detection based on differences between these DTMs is supposed to represent erosion and deposition accurately, a detailed analysis indicates that the initial and final DTMs in the data series sometimes fail to capture the full extent of changes due to various factors. So, natural phenomena, such as the movement of cliff materials (rolling, sliding, creeping), human activities aimed at coastal protection, and errors in DTM processing may disturb clear trends, introducing uncertainties and, in particular, making the data series appear alternating.

To address these issues, we proposed to apply the robust Mann-Kendall test, a non-parametric statistical method used to identify trends in a data series without assuming any particular data distribution. It focuses on determining the direction and consistency of trends (ascending or descending), rather than the change’s magnitude. By implementing this approach, we can pinpoint areas that exhibit clear trends, thereby significantly improving the accuracy of coastal retreat estimations. In regions where trends are not readily apparent, it becomes crucial to investigate potential contributing factors thoroughly by exploring natural environmental dynamics, assessing the impact of human activities, and scrutinizing any errors in data processing. Such a comprehensive analysis ensures a more holistic understanding of the factors influencing these zones.

We employed the proposed approach across four distinguished shore areas characterized by the distinct geological composition of the cliffs, delving into the trends of coastal retreat over the past ten years. As expected for areas with clear trends, the estimation of the dimensions of the recent coastal retreat was in good agreement with historically recorded data. Additionally, in areas exhibiting no discernible trends, we were able to identify the underlying reasons, shedding light on the intricacies of coastal dynamics.

How to cite: Fuchs, M., Tiepolt, L., Schütze, K., and Torizin, J.: The Performance of the Man-Kendall Test in the Analysis of Coastal Changes along Cliff Sections on the Baltic Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7859, https://doi.org/10.5194/egusphere-egu24-7859, 2024.

The size and shape of sediment particles record crucial information on erosion, transport, and deposition mechanisms during sedimentary processes. Therefore, data on grain morphometry is a critical component in understanding sediment production and transport dynamics in various environments, such as fluvial or hillslope settings. However, traditional field methods are labor-intensive, and results may suffer from a limited number of observations. At the same time, remote measurements in images or point clouds still need improvements to counter low accuracy or the need for time-consuming manual corrections (e.g., Steer et al., 2022). These persisting challenges impede the capability of routinely obtaining size and shape information.

Here, we present a new and automated approach (Mair et al., 2023) for obtaining morphometric information on coarse sediment particles from segmented images. To do so, we tap into the capability for transfer learning of deep neural networks. In particular, we use state-of-the-art deep learning, developed to find cells in biomedical images, to segment individual grains in pictures of various sediments and image types. Our method validation includes assessing segmentation performance against ground truth from annotated images and evaluating the measurement quality by comparing results to independent measurements in the field and in images. This approach facilitates precise and rapid grain segmentation and outperforms existing methods. In addition, we observe that higher segmentation quality directly leads to improved precision and accuracy for grain size and shape data. Furthermore, any model of the used architecture can easily be re-trained for new image conditions, which we successfully did for several different settings. This highlights the potential for easy adapting to different environments and scales with comparatively small datasets.

References

Mair, D., Witz, G., Do Prado, A. H., Garefalakis, P., and Schlunegger, F.: Automated detecting, segmenting and measuring of grains in images of fluvial sediments: The potential for large and precise data from specialist deep learning models and transfer learning, Earth Surf. Process. Landforms, 1–18, https://doi.org/10.1002/esp.5755, 2023.

Steer, P., Guerit, L., Lague, D., Crave, A., and Gourdon, A.: Size, shape and orientation matter: fast and semi-automatic measurement of grain geometries from 3D point clouds, Earth Surf. Dyn., 10, 1211–1232, https://doi.org/10.5194/esurf-10-1211-2022, 2022.

How to cite: Mair, D., Witz, G., Do Prado, A. H., Garefalakis, P., and Schlunegger, F.: Automated and flexible measuring of grain size and shape in images of sediment with deep learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8222, https://doi.org/10.5194/egusphere-egu24-8222, 2024.

High-resolution Digital Elevation Model (DEM) data provides essential information for pluvial flood simulation. Although the increased accessibility and quality of publicly available DEM datasets can facilitate geospatial analysis at various scales, existing DEM datasets with global coverage mostly lack sufficient spatial resolution for pluvial flood simulations, which require detailed topographic information to be included in the simulation. Simulating flood scenarios with low-resolution DEMs (>30m) can result in substantial deviations from real cases. This issue becomes even more severe for flood-prone areas in data-scarce developing countries.

Image super-resolution is a technique for reconstructing low-resolution information into high-resolution data. Various deep-learning models have been employed for this task, primarily focusing on generating high-resolution natural-colour images. However, the effects of these deep learning models on enhancing the resolution of DEM data have not been extensively investigated. One of the state-of-the-art super-resolution models, the Residual Channel Attention Network (RCAN), has gained popularity due to its accuracy and efficiency. Leveraging publicly available low-resolution global DEM data and high-resolution regional DEM data, this study assesses the performance of RCAN models in a DEM super-resolution task. The experimental results suggest that, compared to conventional interpolation methods, the tested RCAN model exhibits superior performance in constructing high-resolution DEM data. The generated super-resolution DEM data were then tested in pluvial flood simulations and achieved substantially higher realism in modelling floodwater distribution. The proposed method for constructing super-resolution DEMs opens up the possibility of simulating flooding at hyper-resolution globally.

How to cite: Zhu, Y., Burlando, P., Tan, P. Y., Geiß, C., and Fatichi, S.: A deep learning-based super-resolution DEM model for pluvial flood simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10314, https://doi.org/10.5194/egusphere-egu24-10314, 2024.

River channel bankfull geometry and discharge are important features providing valuable insights into fluvial monitoring and flood recurrency. The bankfull stage represents the riverbank position that approximates the level at which water overflows onto the floodplain. Bankfull discharge is considered the channel-forming discharge, with a recurrence interval of approximately 1.5 years. Bankfull floods are significant, as they are highly effective in changing channel shape and characteristics. Their recurrence intervals can be used for stream assessment and have implications for infrastructure design and flood mapping. Additionally, gaining insights into the factors influencing floodplain inundation across various time periods is crucial, as the frequency of flood events is predicted to rise with the increase in global temperatures.

In this contribution, we present a novel approach to identify the bankfull geometry through a set of dedicated MATLAB functions. A Digital Elevation Model (DEM) with ground resolution of 1 m/pixel is used as input elevation dataset, obtained with airborne LiDAR (Light Detection and Ranging) survey. The selected river channels are divided in regularly spaced sampling sections, where the bankfull geometry is extracted. Then, the hydraulic depth function that plots the elevation above the river thalweg vs. the ratio between the area and the width is computed for every section. Then, the elevation above river associated to the lowest and the most prominent peaks of the function, corresponding respectively to the bankfull stage or bankfull/floodplain inflection point and to the floodplain, are automatically extracted for each section. Manning’s equation is then applied to the hydraulic geometry corresponding to the lowest peaks elevation to compute the bankfull discharge at every river channel section. The validation process includes the comparison between the results obtained through the automatic bankfull geometry and discharge estimation and discharge data available from river hydrological gauges. Results demonstrate that the developed approach is effective to delineate the bankfull geometry from high-resolution DEMs and complements traditional qualitative field observations. Thus, our approach represents a cost-effective alternative for mapping detailed spatial variations over large spatial extents that are difficult to cover with traditional fieldwork.

How to cite: Ruscitto, V., Delchiaro, M., Schwanghart, W., Brignone, E., Piacentini, D., and Troiani, F.: Identification of river channel bankfull geometry from topographic indicators extracted from high-resolution digital elevation datasets , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11527, https://doi.org/10.5194/egusphere-egu24-11527, 2024.

The Earth’s surface results from the interplay of tectonic and erosive forces, and the action of organisms and humans. To gain a deeper understanding of these interactions, accurate monitoring and analysis of topography is essential. Digital elevation models (DEMs) are powerful tools for achieving this goal and are available at ever increasing spatial resolution. TopoToolbox is a research software that provides a “laboratory” for the analysis of DEMs, enabling customized, automated analysis, prototyping and creative method development. Its high computational efficiency, ease-of-use and extensive documentation have attracted a worldwide user base across multiple research disciplines.

Over the last ten years, TopoToolbox, now in version 2, has undergone numerous changes and additions. The development of version 3 of TopoToolbox seeks to build on those past successes and take the software to the next level. Specifically, our goals are (1) to improve usability and accessibility, (2) to enhance quality assurance in the software’s development process, and (3) to increase community involvement in the ongoing development of TopoToolbox. We strive to achieve these goals in a recently funded 2-year project, in which community involvement is a key aspect. In this presentation, we aim to interact with other researchers interested in terrain analysis to discuss avenues for future developments and activities that improve TopoToolbox's usability, expand its usage, and increase its impact in a new version 3.

How to cite: Schwanghart, W., Kearney, W., Lamprecht, A.-L., and Scherler, D.: TopoToolbox 3 – avenues for the future development of a software for terrain analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12288, https://doi.org/10.5194/egusphere-egu24-12288, 2024.

After successfully applying segmentation and machine learning for landform identification and delineation for concave, convex, and generic landforms (landslides, floodplains), the used approach is generalized as a framework. The approach can be implemented in any GIS software that allows scripting and is based on four steps: (i) object-based segmentation based on a specific geomorphometric variable, (ii) contextual merging if the landform is composed of multiple shapes, (iii) selection of the training data segments, (iv) statistical classification by machine learning. The framework refers to creating a set of rules for various scenarios of landform types to allow the implementation of the approach for various landforms and areas around the globe. One of the main requirements regarding the DEM is that its feature resolution be high enough to allow at least a segment to cover the target landform spatially. This requires either LiDAR or RADAR DEMs, with medium or high resolution. We tested COPDEM in areas where there is no vegetation cover and the results show that landslides, floodplains, gullies, sinkholes, and closed depressions can be depicted by the approach.

How to cite: Niculita, M.: A generic framework for the identification and delineation of landforms from high-for DEMs using segmentation, contextual merging, and machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13034, https://doi.org/10.5194/egusphere-egu24-13034, 2024.

Spectral analysis (SA) is a technique commonly used in signal and image processing that makes use of the Fast Fourier Transform to compute the 2D power spectrum, which is a representation of the magnitude of each frequency component of the signal or image. SA can be similarly performed on a topographic map, and the orientation, frequency and magnitude (or power) of general topographic trends can be automatically retrieved and displayed in the 2D power spectrum. Recent studies have shown that spectral analysis can be successfully used to characterize repetitive and spatially homogeneous features or landforms, such as ridge and valley or glacial lineations. However, although these repetitive features dominate the 2D power spectrum, all the topographic information of the map is still present. Therefore, SA can be used on heterogenous and complex topographic map as a proxy for lineament analysis.

Lineament analysis is broadly used in a wide number of applications which include tectonic studies, exploration for groundwater, hazard evaluation for tunnel excavation, rockfalls or waste repository etc. Here, we propose a new methodology for lineament analysis based on spectral analysis and we demonstrate that this is a fast and effective way to derive lineament spatial distribution from images that can be visualized as rose diagrams. To validate our methodology, we stochastically generated 1000 synthetic lineament networks and numerically compared the rose diagrams derived from the power spectra to known lineament distribution. The comparison held a similarity of 94%.

The methodology was also applied to the Oslo region and compared to automatically extracted lineaments from OttoDetect software (developed by the Geological Survey of Norway). Results on three pre-selected areas characterized by different topographic patterns showed similarity of 97%, 95%, and 90%, respectively.

One of the pitfalls of spectral analysis is the lack of positioning on the original map of the signatures in the power spectrum. To locate the main signature on the map, we used the orientation of the main signatures from the power spectrum and used cross-correlation and clustering methods on topographic profiles.

How to cite: Dichiarante, A. M., Redfield, T., Torgersen, E., Svendby, A. K., and Oye, V.: Spectral analysis as proxy for lineament spatial distribution: validation and case study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13135, https://doi.org/10.5194/egusphere-egu24-13135, 2024.

Hiking up a steep mountain, in comparison to walking on a flat beach, is unarguably different. But the horizontal distance made, estimated using a Digital Terrain Model (DTM), might be the same. The projection of 3D landscapes onto 2D grids in DTMs leads to a slope-dependent, inhomogeneous sampling of the surfaces, and a first-order error in topographic metrics. Using the slope dependency of this error, we can quantify and revert it. Foremost, correcting the projection error allows for more accurate estimates of area and volume, e.g., to quantify natural hazards; and enables the use of the full slope distribution to define the physical space of surface processes at any scale.

We quantify the projection error using synthetic landscapes for which analytical solutions of slope angles and surface area are known. In applying the correction to DTM data of a real landscapes, we can address geomorphological processes in physically more meaningful ways. The corrected extracted topographic proxies, here exemplary, the erosional response to uplift in the Mendocino Triple Junction (MTJ) area, California, USA, provide two aspects for interpretation of geomorphic processes. First, as all slope angles are now represented equally, the variations in slope distribution by region of uplift rate is more pronounced. Second, the erosional response causes not only a steepening but narrow slope distribution in the regions of high uplift. The transient response is visible in a broadening of the distribution towards the lower slope angles, as deposition becomes more prevalent. In this example, we also find that the surface area ratio, enables determining the effectiveness of Earth surface processes, by increasing or decreasing the differential between the standard-planform and the surface area. Earth surface processes, that involve transport and volume along the surfaces, if not referenced in time, the ratio between the planform and surface area can provide a spatial reference and could be explored further. Correcting topographic metrics also allows addressing additional questions, like, which slope angles characterize which process domains, which processes create steepening, which lowering of slopes, where, and to what extent? Or, which parts of landscapes, maybe not the steepest, correlate to the highest potential to erode?

How to cite: Voigtländer, A., Rheinwalt, A., and Tofelde, S.: The effect of correcting the projection error in Digital Terrain Models on Earth surface processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13867, https://doi.org/10.5194/egusphere-egu24-13867, 2024.

The integration of point-cloud data in geo- and environmental sciences has become increasingly pivotal, with applications ranging from UAVs, spaceborne and airborne lidars to ground-based lidars and stereo-photogrammetric techniques. This session seeks contributions that delve into challenges related to classification, segmentation, and noise removal in the context of point-cloud data, crucial for facilitating change detection studies. Our study focuses on the Navigational Branch of the ERDC Coastal Hydraulics Laboratory tasked with developing a Digital Twin model for a Dam, exemplifying the complexities involved in creating CAD models of terrain and structures.

To address the intricacies of point-cloud data processing, we employed both open-source and proprietary software solutions—Cloud Compare and Autodesk ReCAP— for noise reduction, ensuring the prepared data is seamlessly integrated into CAD modeling software, specifically Inventor. Surface modeling involved the strategic application of planes on cloud points to generate a foundation for sketching and subsequent solid surface extrusion.

Classification of data points was initiated through the implementation of regions in the noise removal software, facilitating the depiction of various areas on the model. Further, color and material assignment in the CAD software enhanced the identification of distinct part areas. Microstation TopoDOT played a pivotal role in creating a detailed terrain model, complete with physical landmarks and water bodies specific to the Dalles dam site.

The resulting models were exported in the desired file format, ensuring compatibility with sponsor requirements. This case study not only showcases the practical challenges encountered in working with point-cloud data but also highlights effective strategies for noise reduction, classification, and model exportation. The presented methodologies contribute to the broader spectrum of geo- and environmental sciences, emphasizing the significance of accurate point-cloud processing for comprehensive modeling endeavors.

How to cite: Krapac, M.: Advancements in Point-Cloud Processing for Geo-Environmental Modeling: A Case Study of The Dalles Dam Digital Twin Creation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14080, https://doi.org/10.5194/egusphere-egu24-14080, 2024.

The interaction between slope instability processes and river dynamics often triggers a cascade effect. Sediment influx from slopes can obstruct rivers, leading to upstream flooding and potential catastrophic flash floods downstream upon dam breakage. In addition, the incision of the drainage network steepens the valley hillslopes, further exacerbating slope instability processes, modifying the geomorphology and the sedimentary fluxes and increasing the occurrence of landslide-derived hazards.

In this regard, a comprehensive and updated landslide inventory, especially focusing on the interconnection between landslides and drainage networks, is crucial for effective hazard assessment considering these cascading effects induced by slope and fluvial processes.

This study presents advancements in landslide mapping by integrating data from Multi-Temporal Synthetic Aperture Radar (MT-InSAR) and landscape evolution analysis through geomorphological indices such as Chi, Normalized Channel Steepness Index (Ksn) and Stream Length-Gradient Index (SL). Identification of anomalies along rivers using Ksn and SL (knickpoints or knickzones) aided in pinpointing abnormal slopes due to sediment influx from landslides. Additionally, active areas were delineated using the ADAfinder tool, extracting data from MT-InSAR provided by the European Ground Motion Service (EGMS). This multi-technique analysis highlighted the slopes of interest. Landslides identified with these techniques were delimited and characterized in terms of type assignment, using 2x2 m DTM hillshades derived from airborne LiDAR data and field observations.

The upper catchments of the Garona and Noguera Pallaresa rivers (central Pyrenees-NE Spain) were selected as study cases. The study highlights the disequilibrium in the watershed divide between Noguera Pallaresa and Garona basins, suggesting a transition toward equilibrium favouring a main divide migration towards the Noguera Pallaresa due to hillslope processes. The assessment of the equilibrium profile geometry of the Noguera Pallaresa river at a regional scale suggests at least two main knickpoints. The river sections downstream of the knickpoints are associated with landslides triggered by post-glacial dynamics and incision wave effects. Combining SL and Ksn curves with Active Deformation Areas (ADA) underscores areas with potentially reactivating deep-seated landslides, signifying potential high damages in case of low-probability but catastrophic reactivations.

In conclusion, the integration of diverse methodologies shed light on the spatial relationship between transient features in the landscape (knickpoints) and landslide occurrence, emphasizing the need for a comprehensive approach to mitigate landslide and fluvial risks in the Noguera Pallaresa and Garona river basins.

How to cite: Guinau, M., Fernández-Jiménez, C., Barra, A., Viaplana-Muzas, M., Flores, A., Ortuño, M., González, M., Pinyol, J., and Abancó, C.: Multi-Technique Analysis and Landscape Evolution: Implications for Landslide-Fluvial Cascading Hazards Assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14955, https://doi.org/10.5194/egusphere-egu24-14955, 2024.

Cameras that capture images in time-lapse mode of the earth surface enable great opportunities for change detection and thus potential process identification and understanding. The camera systems can range from simple and robust game cameras to complex and synchronised full frame cameras. The main workflow of calculating digital elevation models from overlapping images is similar for the different types of systems; automatically matching the images, performing bundle adjustment considering either calibrated or non-calibrated cameras, geo-referencing the data by automatic ground control point (GCP) measurement, densifying the point cloud and eventually calculating point cloud differences. However, adapted pre-and post-processing steps are needed due to the varying observation conditions considering the camera qualities and the objects of interest. The time-series of point cloud-based change information can be further processed, for example, with time-series clustering approaches to disentangle overlapping processes.

We will introduce three different case studies in the field of fluvial geomorphology, soil erosion research and rockfall assessment. Thereby, different camera systems are utilized. Four low-cost time-lapse cameras are applied in arctic environments to study changes of a river bank at a distance of about 60 m. The high robustness of the cameras encompasses the trade-off of low quality images. In addition, challenging lighting conditions and enduring snow cover complicate the photogrammetric processing. The images are captured with a frequency of two hours, and six permanent GCPs are used to geo-reference the measurements.

Digital SLR cameras are used in moderate climate to measure soil surface changes either due to rainfall simulations or due to natural rainfall events. During the rainfall simulation we use images that are captured by up to ten cameras with a frequency of 10 to 20 seconds and at an object distance between 3 to 4 m. And at the field plot we installed three special camera rigs that encompass five cameras each that are event-controlled by a micro-controller and single board computer solution, which trigger the cameras each time a rain collector bucket is tipping in addition to daily captured images. Challenges for change detection arise from vegetation present at the plots and from runoff water covering the soil surface. Eventually, the derived models of change are used to validate physical based soil erosion models.

The last case study utilizes five full-frame system cameras in the Mediterranean to detect single rockfall events. Images are captured three times a day by an ad-hoc system at a distance of about 100 m. The data is transferred via a locally installed network module. Many areas within the field of view remain stable throughout the measurement period allowing for a time-SIFT approach that matches the images from different points in time. Machine learning algorithms are applied to automatically identify rockfalls in the final 4D dataset. Thereby, we showcase the great potential of time-lapse photogrammetry for different applications of geomorphological change detection.

How to cite: Eltner, A., Blanch, X., Grothum, O., Epple, L., Lotsari, E., Anders, K., and Elias, M.: Applying photogrammetry to time-lapse imagery for geomorphological change detection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15001, https://doi.org/10.5194/egusphere-egu24-15001, 2024.

Geodiversity is “the variety of abiotic features and processes of the land surface and subsurface” [1,2]. Consensus is growing that geodiversity is the geosphere counterpart of what biodiversity represents within the biosphere, atmosphere, and hydrosphere [2]. Thus, it is potentially relevant to ecosystem functions and services [2]. Since the introduction of geodiversity, several scholars studied it from the theoretical and practical points of view, with different approaches, assumptions and purposes. Methods to define diversity of the geosphere are quantitative, qualitative, or a combination of the twos, with the occasional addition of heuristics [3].

Here, we describe a quantitative derivation of a subset of geodiversity, namely, geomorphodiversity. The effort stems from the need of an objective method, apt to providing easy to understand results, readily available for subsequent applications. To that end, requirements are in order about the data included in the analysis: they should be widely available, to allow reproduction of the analysis in most geographical locations, and they should contain enough information to approximate real-world geodiversity.

Geomorphodiversity is one implementation fulfilling the requirements, obtained in the literature by different groups, for different locations [4,5], using simple geomorphometry. Data for the method implemented in Italy [6] are a digital elevation model (EUDEM, 25 m resolution), and a lithological map at 1:100,000 scale [7]. DEM provides derived quantities such as slope, drainage network, landforms [8] and slope units [9], all of which contribute in different ways to produce partial diversity maps. We eventually combine partials into an overall geomorphodiversity raster index, GmI, distinguishing five classes of land surface diversity.

The inherent parameter dependence in the existing implementations of GmI, partially resolved in [6], is one issue to overcome. Free parameters are embedded in the size of neighborhoods (moving windows, or focal statistics) used to calculate the variety, the arbitrary output resolution, and procedures to polish the final raster diversity map from artifacts. We suggest a multiple assessment of the variety of partial abiotic parameters with a full range of different neighborhood sizes, and a-posteriori statistical selection of local values of diversity. This results in a parameter-free approach to GmI, also allowing a custom resolution of the output, with the lower bound of DEM resolution.

We consider a parameter-free geomorphodiversity as a measure of the potential of morphological evolution of the landscape, useful to investigate natural and human-induced diversity in urban areas [10], in combination with accurate, local mapping of geomorphological landforms [11].

References

[1] Gray, (2004) Geodiversity: valuing and conserving abiotic nature. ISBN 978–0–470-74215-0

[2] Schrodt et al., PNAS (2019) https://doi.org/10.1073/pnas.1911799116

[3] Zwoliński et al., Geoheritage (2018) https://doi.org/10.1016/B978-0-12-809531-7.00002-2

[4] Benito-Calvo et al, Earth Surf Proc Land (2009) https://doi.org/10.1002/esp.1840

[5] Melelli et al., Sci Tot Env (2017) https://doi.org/10.1016/j.scitotenv.2017.01.101

[6] Burnelli et al., Earth Surf Proc Land (2023) https://doi.org/10.1002/esp.5679

[7] Bucci et al., Earth System Science Data (2022) https://doi.org/10.5194/essd-14-4129-2022

[8] Jasiewicz et al., Geomorphology (2013) https://doi.org/10.1016/j.geomorph.2012.11.005

[9] Alvioli et al., Geomorphology (2020) https://doi.org/10.1016/j.geomorph.2020.107124

[10] Alvioli, Landscape and Urban Planning (2020) https://doi.org/10.1016/j.landurbplan.2020.103906

[11] Del Monte et al., Journal of Maps (2016) https://doi.org/10.1080/17445647.2016.1187977

How to cite: Burnelli, M., Melelli, L., Bucci, F., Santangelo, M., Fiorucci, F., and Alvioli, M.: A definition of land surface geomorphodiversity across different scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15418, https://doi.org/10.5194/egusphere-egu24-15418, 2024.

Gold is abundant in the greenstone belts of the Guiana shield, in South America, leading to alluvial mining in river sediments and in in-situ rocks. In French Guiana, legal mining takes place under strict environmental regulations and controls, but illegal operations also occur uncontrolled in the vast expanses of the rainforest. Here we describe a successful range of mobile lidar systems, acquisition schemes and processes to map the ground and underground mining operations in a rainforest context. We seek to detect illegal operations, supply and transportation pathways and base camps, using crewed planes and helicopters, uncrewed fixed-wing and multi-copter vehicles (UAV) and handheld lidar systems.

To sense ground elevation below the canopy, airborne lidar systems face three challenges: tree heights (some trees exceed 70 m in height), incised topography (requires performant terrain following capabilities), dark and wet ground surface largely absorbs lidar pulses requiring powerful sources. Tested uncrewed airborne vehicles (UAV) did not yet meet all of the flying autonomy, terrain-following capability, lidar range and on-board decision systems. At present, crewed systems adapt better to conditions and achieve mission objectives.

Over forested areas, observed canopy penetration rates is of the order of 1 ground point for 250 lidar pulses (0.4%). To generate a 1-m/pixel Digital Terrain Model (DTM) with a minimum of occluded pixels, acquisition density should exceed 250 pts/m² at canopy level everywhere. In Dorlin (central French Guiana), a helicopter flew 85-m-above ground-level, 70 % side-lap and 90° cross-lines, using a Riegl VUX-1LR lidar. Targeting 400 pts/m² at canopy-top for 95 % of the 220 ha territory, it reached a canopy-top density of 1400 +/- 750 pts/m² and 43 pts/m² ground density overall. On fully forested areas, ground density dropped to 22.4+/-22.6 pts/m² with 5% of the surface never receiving points at 1 m² level. This enabled interpolation of a 25cm/pixel DTM, which revealed narrow paths, quad tracks, and shaft platforms and head frames under the forest. 2-m kernel high-pass filtering enhanced features better than a standard hill shading. Base camp hut structures, invisible in DTM, are retrievable from native point clouds in a 4 to 5 m-above-ground elevation range. Huts covered in black tarpaulins stand out as rectangular hollow patches due to lidar photon absorption. But even without tarpaulin, hut wooden frames stand out particularly well when point cloud subsets are lit up with the PCV filter of Cloud Compare. Ore-bearing quartz stockpiles however are too small and occluded for a reliable detection and volume computation.

Instead, SLAM-based handheld lidar systems (GeoSLAM Zeb-Revo and Zeb-Horizon) complement the detailed mapping of quartz stockpiles volume, shaft conduit geometry and gallery entrances. Then real-time, SLAM-based quadcopter UAV lidar (Flyability Elios 3) safely penetrates shafts from the surface to explore the undergound gallery network. These new millimetre-scale density point clouds critically reveal spacing, orientation and dimensions of ore-bearing veins, which improves the metallogical understanding of the site and uniquely documents the way artisanal illegal miners operate.

Lidar acquisitions and processing are now being streamlined for systematic use in law enforcement operations and environmental protection actions.

How to cite: Dewez, T., Linares, S., Yart, S., Masson, F., Collignon, M., Rivera, L., Bedeau, C., and Chevillard, M.: Mapping gold mines under the French Guiana rainforest: return of experience with different mobile lidar systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15904, https://doi.org/10.5194/egusphere-egu24-15904, 2024.

Fans are cone-shaped depositional landforms composed of a mixture of sediments, mainly derived from debris flow processes at the catchment scale. In mountainous terrains located in humid climates, debris flows are fundamental agents of landscape evolution and a highly destructive natural hazard. In the northern Colombian Andes, fans have been traditionally occupied by human settlements, which has also produced a long history of disasters in many settlements located on fans. For example, a debris flow on November 13, 1985, devastated the city of Armero, killing approximately 22,000 people and causing economic losses totaling over $US 339 million. In 2017, the city of Mocoa was affected by a debris flow where 333 people died, 130 houses were destroyed, and 1461 were partially affected.

Debris-flow risk is likely to increase as a consequence of the increasing magnitude and frequency of extreme weather and rapid population growth over the past few decades. Hence, identifying fan spatial distribution and debris flow occurrences is important for land use planning. In this study, we implemented geomorphometric analyses in the northern Colombian Andes to understand debris flow occurrence in terms of landscape evolution. Using digital elevation models, fan inventory, morphometric parameters, and geomorphic indices associated with the drainage network at the catchment scale, the close interconnection between debris-flow hazards and landscape evolution is explained.

The results show a clear spatial pattern of fans location and debris-flow-prone basins with knickpoint upstream migration and transient-state catchments, those characterized by high values of Ksn, hypsometric index and constraint values of 𝛘. Those findings suggest that landscape evolution indexes could improve debris flow susceptibility assessment at regional scale.

How to cite: Aristizábal Giraldo, E. V. and Korup, O.: Debris flow catchments and landscape evolution in the northern Colombian Andes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16317, https://doi.org/10.5194/egusphere-egu24-16317, 2024.

Geomorphometry and geomorphological mapping are essential tools for understanding landscape changes. The recent availability of 3D imaging sensors and processing techniques, including Artificial Intelligence, is offering interesting solutions for gemorphometric analyses and processes understanding. Photogrammetry stands as a pivotal image-based tool in geomorphology, enabling accurate 3D reconstruction of complex natural environments and effective tackling of multi-temporal monitoring challenges. A key step in photogrammetry is the identification of corresponding points between different images, traditionally achieved through the extraction and matching of local features such as SIFT and ORB. However, these methods face difficulties when using images of complex environments scenarios. Deep Learning (DL) methods have recently emerged as powerful tools to address challenges such as strong radiometric variations and viewpoint changes (Morelli et al., 2022; Ioli et al., 2023). However, their practical application in photogrammetry is hindered by the lack of libraries integrating DL matching into standard SfM pipelines.

The presentation will introduce the recently developed Deep-Image-Matching, an open-source toolbox designed for multi-view image matching using DL approaches, specifically tailored for 3D reconstruction in complex scenarios (https://github.com/3DOM-FBK/deep-image-matching). This tool can be used to achieve a 3D reconstruction with wide camera baselines and strongly varying viewpoints (e.g., with ground-based monitoring cameras), with datasets involving varying illumination or weather conditions typical of multi-temporal monitoring, with historical images, or in low-texture situations (e.g., snow or bare ice).

Deep-Image-Matching provides the flexibility to choose from a variety of local feature extractors and matchers. Supported methods include traditional local feature extractors, such as ORB or SIFT, as well as learning-based methods, such as SuperPoint, ALIKE, ALIKED, DISK, KeyNet + OriNet + HardNet, and DeDoDe. Matcher choices range from traditional nearest neighbor algorithms to state-of-the-art options like SuperGlue and LightGlue. Available semi-dense matching solutions include the detector-free matchers LoFTR and RoMa.

To handle high-resolution images, the tool offers a tiling process. In case of strong image rotations, such as aerial stripes, images are automatically rotated before matching. Image pairs for matching can be selected by exhaustive brute-force matching, sequential matching, low-resolution guided pairs selection, or global descriptor-based image retrieval. Geometric verification is used to discard outliers among matched features. The extracted image correspondences are stored in a COLMAP database for further processing (i.e. bundle adjustment and dense reconstruction) or can be exported in other formats useful for other open-source and commercial software.

The presentation will highlight how image-based geomorphometry and geomorphological mapping could benefit of the realized tool and how complex environmental scenarios (landslides, glaciers, etc.) could be analysed and monitored with the support of deep learning.

References:

Ioli, F., Bruno, E., Calzolari, D., Galbiati, M., Mannocchi, A., Manzoni, P., Martini, M., Bianchi, A., Cina, A., De Michele, C. & Pinto, L. (2023). A Replicable Open-Source Multi-Camera System for Low-Cost 4D Glacier Monitoring. Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., 48, 137-144

Morelli, L., Bellavia, F., Menna, F., & Remondino, F. (2022). Photogrammetry Now and Then - From Hand-Crafted to Deep Learning Tie Points. Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLVIII-2/W1-2022, 163–170

How to cite: Ioli, F., Morelli, L., Pinto, L., and Remondino, F.: Deep-Image-Matching: an open-source toolbox for multi-view image matching of complex geomorphological scenarios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16412, https://doi.org/10.5194/egusphere-egu24-16412, 2024.