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.

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.

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., Hofstede, 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.

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.

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.