Orals: Wed, 30 Apr | Room G1
Understanding the processes of non-steady state denudation and sediment recycling is crucial for interpreting landscape evolution and sedimentary records, yet its quantification remains challenging. This study integrates field observations, cosmogenic nuclide analyses, topographic data, and modeling to unravel these processes from regolith to catchment scales. Depth profile models were used to estimate denudation rates in regolith within non-steady landscapes, revealing that abrupt surface denudation events—such as those driven by climate change, landslides, or human activities—can be recorded by cosmogenic nuclides in regolith. Our findings also show that denudation rates derived from non-steady state region with strong tectonic activity are often overestimated by assuming steady state. Through measurements of both 10Be and 26Al in riverine sediments, we identified evidence of sediment recycling in the central Tibetan Plateau, with a consistent burial age of 0.54 ± 0.16 Ma. By combining these results and paleoclimate records, we interpret this "Great Burial" as most likely resulting from climate-controlled deglaciation and denudation at the termination of Naynayxungla glaciation during the MIS 13–15 period. This event likely marks the first widespread deglaciation on the Tibetan Plateau.
How to cite: Xu, S. and Yang, Y.: Deciphering non-steady state denudation and sediment recycling using cosmogenic nuclides across regolith to catchment scales, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3802, https://doi.org/10.5194/egusphere-egu25-3802, 2025.
Taiwan is a young arc-continent collisional orogen characterised by rapid exhumation, high relief, and a fluvial and landslide-dominated landscape. The obliquity between the convergence direction and the plate boundary trend creates gradients of uplift and variations in orogenic activity, with an immature orogen in the south, a mature orogen in the central and northern regions, and possible cessation of orogeny in the far north. Channel steepness strongly correlates with erosion rates, suggesting fluvial erosion as the dominant exhumation process, primarily driven by tectonic forcing. These processes maintain a quasi-equilibrium where erosion and uplift rates are nearly equal, shaping Taiwan’s dynamic and rapidly evolving landscape. Over the past two decades, in-situ produced cosmogenic nuclides, particularly 10Be in quartz-bearing rocks, have emerged as essential tools for studying bedrock erosion rates and landscape evolution. Early studies in Taiwan utilised atmospheric 10Be to measure sedimentation rates along continental margins, while later works employed in-situ 10Be to date glacial features, stream terraces, and soils, providing critical insights into surface deformation and climate. Applications of 10Be in modern river sediments revealed its capacity to address orogen-scale surface processes, with studies linking denudation rates to tectonic control in mature orogens. Recent research has refined these approaches, highlighting the effects of landslide sediment on 10Be concentrations and providing detailed spatial erosion patterns at the catchment scale. Building on this foundation, our presentation introduces a comprehensive dataset of unpublished spatial and temporal analyses, offering new perspectives on Taiwan’s topographic evolution. These data enhance our understanding of the interplay between surface processes and the construction of the central mountain range, enriching the broader narrative of Taiwan’s geomorphic evolution and the complexities of erosional processes driven by tectonics.
How to cite: Siame, L., Clementucci, R., Kang, C.-C., Chu, H.-T., Chang, C.-P., Lee, J.-C., Leanni, L., Braucher, R., and Team, A.: Taiwan's mountain building and landscape evolution: A cosmogenic perspective, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4981, https://doi.org/10.5194/egusphere-egu25-4981, 2025.
Sediment grain size in bedrock rivers is critical in determining incision thresholds and energy expenditure on bedrock channels during floods, affecting fluvial relief over geological time. However, little work has explored controls on grain size distribution on mountainous bedrock river systems, particularly in the tropics and sub-tropics, where intense chemical weathering alters near-surface properties, producing thick critical zones. Here, we quantify grain size distributions using Wolman pebble counts in three rock types, serpentine (SP), volcaniclastic (VC), and granodiorite (GD), across topographic gradients on the tropical island of Puerto Rico. Our experimental design focuses on >150 low-order channels (draining ~2.5-100 km²) that are morphologically in a steady state, drain largely a single rock type, and span as large of topographic gradients as possible. This approach enables us to explore how differences in Critical Zone architecture – as dictated by rock type and topography – affect grain sizes. In aggregate, our results suggest minimal differences in median (D50) and D84 grain sizes among the three rock types, ~35 cm and ~180 cm, respectively. However, GD-draining rivers are ~36% sand, while VC and SP catchments have about 2.5 times less sand. The high sand content in GD-draining rivers is due to in-situ sand production within the Critical Zone, which emphasizes the role of rock type in determining grain sizes in Puerto Rican rivers. Across all rock types, grain size coarsens with increasing catchment average steepness (e.g., slope, normalized channel steepness indices), with significant and stronger correlations for coarser grain size fractions. We interpret that grain size coarsening with increased topographic steepness is due to faster erosion rates and shorter residence times in the critical zone, resulting in less weathering and larger grains delivered to river channels. These findings emphasize the role of rock type and erosion rate in determining grain size, which, in part, determines the magnitude of incision thresholds in river channels. We use a detachment-limited stream power model that includes incision thresholds to explore the implications of these findings on mountain relief. Considering models of sediment mobilization that consider the role of sand in reducing the critical shear stress of coarser grain size fractions, elevated sand content in GD-draining rivers could result in a ~20-40% reduction in fluvial relief relative to VC and SP draining rivers at comparable rock uplift rates. These models also suggest the progressively coarser sediment load in steeper topography might increase fluvial relief from ~20 to ~200% relative to standard models without an incision threshold. These findings demonstrate the fundamental role of the Critical Zone in modulating grain size distributions in topical bedrock rivers and imply a key role in determining mountain relief.
How to cite: Gallen, S., Axness, A., Perez Hincapie, A., Drobnich, K., Vicens Clavell, E., and Hughes, K. S.: Critical Zone controls on bedrock river grain sizes in the tropics and implications for mountain relief, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3883, https://doi.org/10.5194/egusphere-egu25-3883, 2025.
Mountainous landscapes have been progressively shaped during the Quaternary under oscillating glacial-interglacial conditions. However, in the context of current climate change, quantifying alpine erosion dynamics has remained problematic because geomorphic processes operate at interrelated timescales. Thus, deciphering the interactions between climate change, glacier retreat, and sediment production in alpine catchments has proven challenging. In this context, we aim to further constrain the transient geomorphic response and catchment sediment transfer during glacial/interglacial oscillations, and especially during the transition period since the Last Glacial Maximum (LGM, ca. 20 ka), using terrestrial cosmogenic nuclides as proxy for erosion processes.
Here, we focus on the Ariège catchment (Eastern Pyrenees), a high-relief area crossing various lithologies that has been extensively glaciated and shaped by glacial processes during the Quaternary. We collected modern river sediments samples along the main Ariège river and its tributary basins, covering contrasted lithologies, topo-climatic settings and LGM glacial coverage. We complemented this dataset with Lateglacial sediment archives within the Ariège catchment together with fluvio-glacial terrace sediments in the downstream foreland area. Terrestrial cosmogenic nuclide (TCN) 10Be and 26Al concentrations were measured on these samples with the overall objectives to (1) identify TCN concentration differences between modern and Lateglacial/fluvio-glacial deposits, (2) assess sediment transfer times and potential recycling (using 26Al/10Be ratios), and finally (3) derive catchment-averaged denudation rates from TCN concentrations to investigate spatial erosion patterns and discuss the main controlling factors.
The 26Al/10Be ratios calculated for modern river sediments are in majority between 6 and 6.75, consistent with surface production ratios. This suggests that most modern river sediments samples have a simple sediment transfer dynamics with limited effects of burial and recycling from glacial overdeepenings and low input from high elevation slowly eroding weathered surfaces. Measured 10Be concentrations in modern river sediments are 2 to 5 times higher than for Lateglacial and fluvio-glacial terrace sediments, showing a clear difference in the 10Be sediment signature during glacial and interglacial periods. This reveals that (1) glacial erosion has been effective enough to partially reset the TCN signals, and (2) the post-glacial period is marked by a re-adjustment of TCN concentrations towards an “interglacial” signal. Finally, TCN-derived catchment-averaged denudation rates reveal a high spatial variability within the Ariège catchment, both between tributary basins (from 33 to 294 mm/ka) and along the main Ariège stream (from 130 and 278 mm/ka). Our preliminary results point towards a topographic control on the modern erosion pattern, with a statistically-significant correlation between denudation rates and mean catchment slopes while other topo-climatic parameters appear less efficient in tuning the spatial distribution in denudation rates. We will discuss the potential influence of long-term orogeny, litho-tectonic configuration, and glacial inheritance on the modern slope distributions and overall topographic patterns in the Ariège catchment. Our work contributes to a better understanding of the sensitivity of alpine landscapes to climate forcing and associated changes in geomorphic processes over glacial-interglacial oscillations, using TCN approach for quantifying erosional processes, sediment production and transfer in mountainous environments.
How to cite: Féaud, B., Valla, P. G., Delunel, R., Delmas, M., Carcaillet, J., Lehmann, B., Torcheboeuf, M.-E., and Paradis, N.: Post- glacial geomorphic response, erosion dynamics and sediment transfer in the Ariège catchment (Eastern Pyrenees, France), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6709, https://doi.org/10.5194/egusphere-egu25-6709, 2025.
In hillslopes where landslides are the main mechanism of erosion, land use and land cover significantly influence sediment transfer downslope. This relation allows for assessing the spatial and temporal distribution of sediment flux within the basin.
An evaluation of the (dis)connectivity factors in the pre-Pyrenees region of Catalonia shows that the Saldes Basin has experienced a significant transformation in land cover over the past 30 years. There has been a notable 30% increase in shrublands and forests. This change is primarily attributed to the abandonment of agricultural practices in mountainous areas, allowing for a natural succession of vegetation.
This increase in forest cover usually results in reduced connectivity and lower erosion rates. However, soil erosion rates can rise significantly given the high risk of wildfires linked to these vegetation types. The destruction of vegetation and changes in soil properties can lead to increased runoff and sediment transport. Therefore, conducting a more detailed analysis of the relationship between sediment production and land cover is essential.
This project examines the relationship between soil erosion and land use and cover changes in mountainous areas. The methods and tools used in this study quantitatively analyze the current sediment production, the effects of vegetation, and the factors driving changes in land cover. This involves assessing geomorphometric parameters and hillslope processes and implementing an index of connectivity.
Integrating this analysis with an overland transport Monte Carlo model allows the assessment of the volume of sediment vulnerable to propagation. Based on climate change projections until 2100, the increase in overland transport to the targeted river is projected to rise by 2.8%, 9.6%, and 8.9% for the near, mid, and far future, respectively. This translates to a Landslide mobilization rate (LMR) of 75 to 500 tons per square kilometer per year reaching the target river, depending on different (dis)connectivity patterns.
The results aim to identify the source areas and understand sediment transport to the target river, facilitating a detailed investigation of sediment production within the basin. This evaluation helps to determine the potential of specific source areas to supply sediment to the main drainage system. The findings highlight critical areas that require intervention and enhance our understanding of how erosion processes vary spatially.
How to cite: Rodriguez, S., Hürlimann, M., Medina, V., Torra, O., Oorthuis, R., and Puig Polo, C.: Evaluating the impacts of land use and land cover changes on the spatial and temporal patterns of sediment connectivity: A case study of shallow landslides in the pre-Pyrenees of Catalonia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18441, https://doi.org/10.5194/egusphere-egu25-18441, 2025.
This study examines sedimentary deposits from Storm Alex (2 October 2020) in the Roya Valley, focusing on three different sub-valley (Dente, Consciente and Caïros) to understand flow processes and associated lithofacies. Key factors controlling sediment transport include lithology, slope, and sediment supply, which influence the occurrence of bedload, suspension, or debris flows. A notable ~5 wt% difference in fines (clay + silt) was observed between debris flows in the Dente sub-valley and bedload/hyperconcentrated flows in other areas.
In the Dente, extensive reworking of glacial and colluvial deposits triggered debris flows that transitioned into hyperconcentrated and bedload flows, culminating in sheetflood deposits on the Viévola fan. The Consciente sub-valley exhibited bedload and hyperconcentrated flows, with debris flows linked to lateral inputs from landslides. The Caïros sub-valley, characterised by gentler slopes and a wider valley floor, was dominated by bedload processes with localized debris flows originating from right-bank tributaries or natural dams.
Hydraulic reconstructions using empirical discharge, unit stream power, shear stress, and clast size estimates provided insights into event intensity, offering valuable reference points for understanding extreme hydro-sedimentary events. Spatial and temporal variability was significant, highlighting the challenges in interpreting fossil deposits without precise temporal context, since a single extreme rainfall event (>1000-year return period) produced a wide range of facies.
This case study underscores the complexity of flow transitions (debris flows to bedload) and the importance of lithological and topographic constraints. The findings emphasize the value of interdisciplinary, multi-scale approaches in documenting and understanding extreme hydro-sedimentary events in mountainous regions
How to cite: Kerverdo, R., Lafuerza, S., Gorini, C., Fouache, E., Rubino, J.-L., Granjeon, D., Deschamps, R., Jafari, M., Lagrée, P.-Y., and Bianchi, N.: Extreme flood event and their depositonal signatures: the case of the Storm Alex in the Roya Valley, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17785, https://doi.org/10.5194/egusphere-egu25-17785, 2025.
Hydrological and erosion processes in mountainous catchments are often influenced by climatic, geologic, and anthropogenic factors. Recent studies show that significant erosion in the European Alps is caused by extreme events, such as floods, windthrows, and avalanches. However, studies integrating the monitoring of hillslope erosion with environmental tracers to investigate the origin of overland flow (OVF) are rare. Thus, this study aims to: i) examine the temporal geomorphologic changes of an eroded experimental hillslope (including sediment estimation) in the Bridge Creek Catchment (BCC, eastern Italian Alps); and ii) compare the OVF generating in erosion risk and non-prone to erosion areas using environmental tracers (i.e., δ2H and δ18O, electrical conductivity, and major ions).
The BCC catchment covers an area of 0.14 m2, with an elevation range from 1931 to 2515 m a.s.l. Geomorphic changes in two eroded hillslopes (Area 1: 910 m2; Area 2: 484 m2) near the lower part of BCC were analyzed using the Difference of Digital Surface Models (DoD) reconstructed from four high-resolution DSMs obtained by Unmanned Aerial Vehicle between August 2023 and October 2024. Additionally, three sediment collectors (SCs) were installed at the hillslope toe to quantify the amount of sediment deposited between late June and November 2024. Water samples for environmental tracer analysis were collected from stream water, spring water, shallow groundwater, OVF from the hillslope, rainfall, and saturated riparian zone between June 2023 and November 2024. Further, soil leaching tests with different durations (24 and 48 hours) were conducted to assess ion enrichment in water mixed with eroded soil.
The DoD analysis showed that topsoil removal particularly along the rill networks. Furthermore, shallow erosion caused by nival abrasion from snow movement was observed during the April 2024 survey. Soil losses from the experimental hillslope in BCC (Area 1 with three SCs) were estimated to be approximately 3.9 tons for the monitoring period, originating from an effective contributing area of 610 m2 (out of 910 m2). The OVF from erosion-prone hillslope had a less negative isotopic composition, reflecting the isotopic signatures of recent precipitation events. In contrast, water sources from non-erosion risk areas depicted a depletion in heavy isotopes compared to summer rainwater. Stream water, spring water, groundwater, and saturated OVF in riparian zones exhibited less variability in isotopes compared to OVF from the eroded hillslope and rainfall. These findings highlighted the influence of snowmelt and summer rainfall on hillslope erosion.
Acknowledgements: This study was carried out within the Agritech National Research Center and received funding from the European Union Next-Generation EU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022). This abstract reflects only the authors’ views and opinions; neither the European Union nor the European Commission can be considered responsible for them.
Keywords
Alpine hillslopes, soil erosion, digital surface model, overland flow, environmental tracers
How to cite: Adane, G. B., Marin, E., Marchina, C., Bettella, F., Martini, M., Tarolli, P., and Zuecco, G.: Integrating hillslope erosion monitoring with tracer-based characterization of water sources in a small Alpine catchment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12586, https://doi.org/10.5194/egusphere-egu25-12586, 2025.
Evaluating hillslope sediment supply to stream channels and hillslope-channel feedback mechanisms is a key step for a proper sediment management. In this study, a distributed modelling approach will be applied to explore sediment dynamics (erosion, transport, deposition) along hillslopes and to estimate the sediment export to the drainage network due to landsliding. For the purpose, the open-source software LANDPLANER will be used. Such tool is built upon a distributed hydrological modelling procedure and uses a simplified set of input data, namely (i) a slope and an accumulation map derived from a DEM, (ii) meteorological data, and (iii) a Curve Number map derived from land use/cover and soil maps based on SCS method (https://www.nrcs.usda.gov/). LANDPLANER estimates primarily the repartition of rainfall into infiltration and runoff and secondarily the related sediment erosion, transport and deposition. The tool will be applied in small basins located in the central/northern sector of the Apennine chain. The model will be set up and calibrated in the different specific study area conditions, using benchmark data. Effectiveness of calibrations depends on the type, quality and accuracy of the benchmark data. Multiple calibration approaches will be tested, accounting for the presence of landslides on hillslopes and their possible sediment supply. The calibrated model will be used to estimate the dynamic water and sediment connectivity in relation to specific rainfall and landslides spatio/temporal patterns and to site-specific land use, vegetation and soil conditions. Scenario-based simulations will evaluate sediment dynamics for real/plausible basin managements in response to varying natural and/or anthropogenic forcings.
How to cite: Rossi, M., Fiorucci, F., Santangelo, M., Masini, A., and Brardinoni, F.: Distributed modelling of erosion and sediment delivery to drainage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17998, https://doi.org/10.5194/egusphere-egu25-17998, 2025.
Badlands have been extensively studied for their erosion dynamics and sediment transport due to their remarkable sensitivity to climate forcing [1]. These erosion processes, primarily driven by mass wasting, are typically investigated at the plot scale using rainfall experiments [2] or at the catchment scale by integrating export measurements at gauging stations [1]. However, detailed spatial analysis of sediment dynamics within a catchment remains scarce [3]. This lack of spatially explicit data limits our ability to identify the contributions of various mass-wasting processes to the overall sediment budget and landscape dynamics.
This work is based on the Draix-Bléone observatory [4], which provides time series of suspended and deposited sediment loads for the Laval catchment (French Alps). This small (86ha), steep, denuded (up to 57%) and unmanaged catchment is instrumented at its outlet since 1983. These chronicles emphasize very high denudation rates (>100 T/ha/year) associated to strong seasonal storms [1]. In addition, we analysed a 6-year diachronic LiDAR scans that cover the whole catchment and conducted shallow-water modeling of its hydraulic network with the GraphFloods algorithm [5]. This allow us to assess the contributions of the different erosion processes to the geomorphological dynamics as well as sediment residence.
Our results highlight several compartments of the critical zone that contribute significantly to the total sediment budget. In particular, landslides account for 15% of the export measured at the outlet and crests erosion for almost 5%, although these areas together cover only about 1ha. This corresponds to the extreme erodibility we measure in marls on submetric (>60 kg/m²/year) and metric (>20 kg/m²/year) specific drainage areas. We also identify important sediment sinks that regulate export, such as the narrowing of the main channel upstream of a slow-moving landslide. In addition, uncleared debris on slopes and in elementary gullies represent in average 30% of the mass balance of associated slides, underscoring their central role in sediment dynamics.
Our results highlight the complex interplay between sediment sources and sinks in shaping steep badland catchments. By combining high-resolution spatial analysis with long-term monitoring data and hydraulic modeling, this study provides new insights into how small-scale processes drive large-scale sediment budgets. It contributes to wider efforts to model sediment flows in sensitive and rapidly changing landscapes.
[1] N. Mathys et al., (2003). Erosion quantification in the small marly experimental catchments of Draix (Alpes de Haute Provence, France). Calibration of the ETC rainfall-runoff-erosion model. CATENA. DOI:10.1016/S0341-8162(02)00122-4.
[2] D.J. Oostwoud Wijdenes and P. Ergenzinger (1998). Erosion and sediment transport on steep marly hillslopes, Draix, Haute-Provence, France: an experimental field study. CATENA. DOI:10.1016/S0341-8162(98)00076-9.
[3] J. Bechet et al., (2016). Detection of seasonal cycles of erosion processes in a black marl gully from a time series of high-resolution digital elevation models (DEMs), Earth Surface Dynamics. DOI:10.5194/esurf-4-781-2016.
[4] S. Klotz et al., (2023). A high-frequency, long-term data set of hydrology and sediment yield: the alpine badland catchments of Draix-Bléone Observatory. DOI:10.5194/essd-15-4371-2023
[5] B. Gailleton et al., (2024). GraphFlood 1.0: an efficient algorithm to approximate 2D hydrodynamics for Landscape Evolution Models, EGUsphere, DOI:10.5194/egusphere-2024-1239.
How to cite: Boukhari, Y., Lucas, A., Le Bouteiller, C., Jacquemoud, S., and Klotz, S.: Dynamics of a badland watershed subject to erosion by diachronic LiDAR analysis and hydraulic modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18421, https://doi.org/10.5194/egusphere-egu25-18421, 2025.
Denudation is arguably one of the most important processes in determining the functioning of the Earth’s surface, from landscape morphology to CO2 consuming silicate weathering and soil/sediment production. While slope is the primary control on denudation rates, slope-based models explain only half of the observed variance, systematically underestimating the highest rates and overestimating the lowest rates. This discrepancy arises from the lack of other environmental factors and the decoupling of denudation rates from slope beyond certain thresholds. To address this, we propose a novel threshold-control decision tree model, incorporating 14 environmental predictors to analyze denudation rates of ~4000 river basins worldwide. Our results identify key slope thresholds at 3°, 12° and 15°. For slopes below 3°, denudation rates rarely exceed 10 mm/kyr, though high mean annual temperatures can enhance denudation by accelerating chemical weathering. As slope increases, it becomes less determinant, and denudation transitions from transport-limited to detachment-limited regimes. Climate seasonality (3°≤slope<12°), precipitation and seismicity (12°≤slope<15°), and runoff and vegetation coverage (slope≥15°) emerge as critical secondary controls. Our ensemble model of decision trees explains an additional 30% of the variation in denudation rates (R2= 0.82), enabling us to give a more accurate prediction of global denudation rates at 1-km resolution. Our results provide quantitative constraints for understanding Earth surface dynamics over the last millennia and throughout geologic history.
How to cite: Liu, Y. and Zhao, J.: Global denudation rates based on machine learning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16733, https://doi.org/10.5194/egusphere-egu25-16733, 2025.
Posters on site: Thu, 1 May, 16:15–18:00 | Hall X3
This study investigates suspended sediment transport in two glaciated catchment areas of the Eastern Central Alps within the DFG Research Group SEHAG (Sensitivity of High Alpine Geosystems to climate change since 1850). The main objective of this work is to characterize the conditions that trigger suspended sediment transport and the resulting sediment dynamics, emphasizing the sediment supply activated under specific hydrometeorological conditions.
The methodology combines continuous meteorological data with monthly suspended sediment measurements conducted during the ablation period of 2024 using manual samplers at strategically positioned sampling stations across the Upper Kaunertal and Martelltal catchments. Two primary research questions are addressed: (1) How do suspended sediment concentrations and loads vary spatially and temporally when comparing glacier terminus locations with downstream stations? (2) What characteristic patterns emerge in the suspended sediment samples under different hydrometeorological conditions?
During days dominated by glacial melt, the suspended sediment samples show a typical diurnal peak around 15:00-16:00, with concentrations up to 2.5 g/l in Kaunertal and 11.8 g/l in Martelltal, following the glacial hydrograph. However, notable increases of up to 1169 % occur during precipitation events, suggesting the activation of different sediment sources. These findings provide insights into how different hydrometeorological conditions activate distinct sediment sources and contribute to the understanding of sediment dynamics in glaciated catchments. The results lay the foundation for future suspended sediment monitoring.
How to cite: Kara-Timmermann, D., Himmelstoss, T., Betz-Nutz, S., Altmann, M., Rom, J., Haas, F., Heckmann, T., and Becht, M.: From Source to Sink: Spatial and Temporal Variability of Suspended Sediment Load in two Glaciated Alpine Catchments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4444, https://doi.org/10.5194/egusphere-egu25-4444, 2025.
The rapid retreat of Alpine glaciers in recent decades has a direct impact on glacier runoff and sediment transport. As deglaciation begins, runoff increases to a maximum (“peak water”), after which runoff gradually decreases. Sediment transport is expected to vary as well over the time, but despite the significant environmental relevance of sediment transport for the ecological functioning of Alpine streams and its potential hazard to Alpine communities, little is known about how sediment transport (and most the notably bedload fraction) changes with deglaciation. The difficulty of measuring bedload transport in the field determines the paucity of measured time-series extending back in time for more than a couple of decades, and none in deglaciating river basins.
One method of overcoming this problem is to use data collected from water intakes of hydropower plants, widespread in Alpine streams and rivers. Many intakes were built in the 1960s, and mostly at high elevations, in glaciated basins. Most of them have sediment traps where water and sediment are separated before water can be transferred to storage or to the turbines. Such traps need to be flushed when bedload deposits reach a certain level. By knowing the volume of the sediment traps and the packing density of the sediment, it is possible to reconstruct the bedload transport history of a given catchment, by analysis the flushing operation. For regulatory reasons, such records are commonly also complemented by very high-quality water discharge records that can be used to reconstruct the associated bedload transport capacity and thus determine the extent to which bedload has been supply or transport limited through different hydrological periods.
In this work, we present the reconstruction of the volume of bedload exported over the last 60 years for more than 20 Alpine catchments located in the southwest of Switzerland. These basins are heterogeneous with different extents of contemporary glaciation and different climatic and geographical characteristics. Data suggest an upward trend in sediment transport since the late 1980s for most of the catchments analysed, coinciding with the onset of rapid Alpine warming in the 1980s. Bedload transport slowed in the 1990s, seemingly associated with a series of years with reduced up-glacier snowline recession, before accelerating again in the early 2000s, with some evidence of a peak sediment export in the 2010s. The snowline recession effect is interesting because it is supported by recent process-based studies which suggest that the ability of glaciers to evacuate bedload-sized sediment is constrained by up-glacier extension of the subglacial drainage network during a melt-season, itself controlled by snowline recession. However, some glaciers show anomalous behaviour which are possibly caused by the direct effects and legacy of glacial overdeepenings. This can lead to site-specific, geomorphologically-influenced responses of bedload transport on top of the underlying regional-scale trend of climate warming.
How to cite: Gianini, M., Repnik, L., Argentin, A.-L., Pitscheider, F., Comiti, F., and Lane, S. N.: Bedload transport histories in heterogeneous Alpine glaciated catchments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8728, https://doi.org/10.5194/egusphere-egu25-8728, 2025.
The rate at which Alpine glaciers erode their bedrock and evacuate eroded sediment to downstream environments is a fundamental control on landscape evolution, ecosystem dynamics and water quality. However, directly measuring subglacial erosion and sediment evacuation processes is extremely difficult since they occur under tens to hundreds of meters of ice. In general, Alpine glaciers are thought to be efficient at evacuating subglacially eroded sediment via meltwater flow in subglacial channels with very high transport capacities. However, recent field observations and hydrological modelling work suggests that coarse sediment transport may be inhibited near glacier termini in the presence of unpressurised subglacial channels. Accumulation of coarse sediment may substantially affect subglacial erosion and hydrology. Extended lags between coarse sediment production and eventual evacuation may also limit the timescales over which sediment export measurements in proglacial rivers can be used to estimate glacial erosion rates. Here, we apply a recently developed method for tracking radio-tagged particles as they are transported through subglacial channels to assess coarse sediment mobility. We deployed 324 pebbles and cobbles tagged with active RFID tags directly into an unpressurised, ice-marginal subglacial channel at the Otemma Glacier, southwestern Switzerland and tracked their motion from the glacier surface using a system of roving and stationary antennas (350 m channel reach). We report very low movement and prolonged storage of coarse subglacial sediment. Particle motion remained low despite exceptionally high meltwater discharge during the mid to late melt season. Only 16% of particles were transported out of the glacier, indicating significant inter-annual storage of coarse sediment. These results reveal that some glaciers do not efficiently evacuate coarse sediment, suggesting that sediment export records from proglacial rivers may be better suited for inferring erosion rates over extended timescales (decadal or longer) rather than shorter, typical observation periods.
How to cite: Jenkin, M., Mancini, D., Miesen, F., and Lane, S.: Low bedload mobility in an Alpine subglacial channel, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18670, https://doi.org/10.5194/egusphere-egu25-18670, 2025.
Initially, landscape evolution models (LEMs) were derived by observing the landscape and its change through cartography metrics. Since then, the techniques have shifted to more process-based numerical methods and have been used to reconstruct a wide range of physical landforms through computer simulations. One such application is reconstructing the Alps. However, as we seek to model the landscape evolution within a topographically driven region of the Alps, we require high-order ice dynamics to accurately capture the underlying physics. As such, existing landscape evolution models, ones that incorporate both glacial and fluvial erosion, are incapable of modelling millions of years of erosion at a high spatial resolution due to the computational cost. However, by extending the efficient physics-driven AI iceflow model, the Instructed Glacier Model (IGM), to also act as a LEM, we are able to reduce the computational load by 1-2 orders of magnitude. As IGM only replaces the iceflow solver, this then means we can incorporate existing state-of-the-art process-based erosion models within the geomorphology literature, including but not limited to abrasion, quarrying, fluvial, and hillslope processes. We then seek to show how powerful this new model is by validating it on existing benchmark papers across the aforementioned processes while also simultaneously reducing the computational load. As such, this allows one to do landscape evolution modelling over millions of years at a high spatial resolution, presenting itself as a potential option to model the entire Quaternary period, and possibly beyond. Finally, this exposes new research applications that rely on ensemble approaches as well as inverse techniques as the computational demand for doing such simulations is now feasible.
How to cite: Finley, B., Jouvet, G., Cordonnier, G., Herman, F., and Leger, T.: Achieving Computationally Trackable Modelling of Erosion in the Alps using the Instructed Glacier Model (IGM), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16480, https://doi.org/10.5194/egusphere-egu25-16480, 2025.
The unprecedented atmospheric warming, coupled with extensive cryosphere degradation, has triggered profound changes in terrestrial landscapes and hydrogeomorphic processes. Rapidly increasing temperature-dependent erosion in cryospheric regions is releasing vast quantities of unconsolidated sediment. Together with altered hydrological processes, shifts in the timing and magnitude of fluvial fluxes have been widely identified in cryosphere-featured rivers. Notably, the substantial increase in summer sediment transport can be attributed to rich sediment sources activated by thaw-related processes and greater glacier meltwater pulses and pluvial pulses. Such amplified seasonality in sediment transport has crucial implications as they fundamentally alter the seasonal allocation of organic matter, nutrients and pollutants, thus affecting the year-round provision of water, food, and energy to populated and vulnerable mountain communities. Continuous glacier retreat and permafrost degradation are expected to further elevate sediment fluxes in the coming decades until reaching the maximum (“peak sediment”). The timing of this peak may lag behind the meltwater peak by decades or even centuries, driven by the legacy effects of fluvial transport and the remobilization of sediment deposited in proglacial and periglacial regions. As thermally-controlled sediment sources are depleted, we predict that sediment-transport regimes will shift from the ongoing temperature-dominated regime toward a rainfall-dominated regime after the completion of deglaciation. Understanding regime shifts and associated tipping points in sediment transport is essential for safeguarding downstream riverine ecosystems and enabling adaptive, forward-looking basin management strategies.
How to cite: Zhang, T.: Climate-driven regime shifts and amplified seasonality in sediment transport of cryosphere-fed rivers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1855, https://doi.org/10.5194/egusphere-egu25-1855, 2025.
Studies on the simulation of erosion in high alpine geosystems are still rare. Using the physically based soil erosion model Erosion3D (E3D), we show the simulation of fluvial erosion on a steep and unvegetated slope in a Little Ice Age (LIA) glacier foreland over several years. The study area is located in the proglacial area of the Zufallferner glacier in the Martell Valley (South Tyrol, Italy). The slope erosion is mainly due to fluvial erosion and process dynamics. A digital elevation model (DEM), various soil physical properties and precipitation data were used as input parameters for the E3D model. The DEMs were generated either from airborne LiDAR surveys (2013 and 2019) or from UAV-based structure-from-motion (SfM) photogrammetry (2023). Additional soil parameters required for E3D, such as bulk density, soil moisture, cover information, grain size distribution, erosion resistance, hydraulic roughness and the skin factor were determined. For this purpose, three rain simulations were carried out during a field campaign in August 2023 and corresponding soil samples were collected and analysed in the laboratory. The precipitation data as input for E3D comes from a data set that was created with a regional climate model (RCM). The Advanced Research WRF (ARW) module of the Weather Research and Forecasting (WRF) model (version 4.3) was used for the dynamic downscaling of the ERA5 climate data. This approach provided precipitation data for the Martell Valley with a temporal resolution of 15 minutes and a spatial resolution of 2x2 kilometres.
The E3D simulations were calibrated by comparing the modelled erosion volume of a specific slope section with the erosion volume derived from the DEMs of Difference (DoD) for 2023 and 2021. Spatial and temporal validation was then performed by comparing the E3D simulated erosion volumes with the volumes calculated from the corresponding DoDs (2013 to 2019 and 2019 to 2021). The E3D simulation results show that the net erosion volume of the entire slope section for each epoch agrees well with the calculated erosion volumes from the DoDs and is within their respective error ranges. These results confirm the suitability of the E3D model for simulating geomorphological activity on this slope within an LIA glacier foreland. Finally, we aim to improve the temporal resolution of geomorphological activity on the selected slope section using E3D simulations. By allowing an annual quantification of erosion between 2013 and 2023, the model enables a deeper understanding of the relationship between erosion dynamics and precipitation events.
How to cite: Altmann, M., Fischer, P., Haas, F., Pfeiffer, M., Ramskogler, K., Rom, J., Kara-Timmermann, D., Himmelstoß, T., Heckmann, T., and Becht, M.: Simulation of soil erosion in the Little Ice Age glacier foreland of the Zufallferner (South Tyrol, Italy) using Erosion-3D, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5734, https://doi.org/10.5194/egusphere-egu25-5734, 2025.
The erosion and weathering exert a key control on the long-term carbon cycling between the earth's surface and crust, thus impacting Earth's climate. The net carbon budget of a tectonically active catchment is based on the superposition of several carbon sources and sinks, but certain processes, such as petrogenic organic carbon (OCpetro) weathering, still lack comprehensive quantitative research, hindering a full understanding of the net carbon budget of mountain building. In this study, we explored OCpetro weathering process within the Eastern Tibetan Plateau utilizing rhenium (Re) as a tracer to quantify OCpetro weathering rates and elucidate carbon fluxes. Detailly, we measured rhenium concentration, TOC, and the concentration of major ions of the river water as well as bedload sediments of the large river basins within and on the eastern margin of the Tibetan Plateau, including Yangtze, Mekong, Salween, Yellow and Brahmaputra Rivers. We then portioned the sources of major ions as well as dissolved rhenium by a Monte Carlo simulation. Lastly, we quantified the carbon transfer through several geological processes. The overall OCpetro weathering rate and net carbon budget of the Tibetan Plateau on time scales of 104-107 years are 1.95(±0.60)tC·km-2·yr-1 and 1.81 +0.34/-0.49 tC·km-2·yr-1, respectively, indicating the Tibetan Plateau currently serve as a carbon source. This study not only refines our understanding of the OCpetro weathering but also reveals a dynamic transforming impact on the geological carbon cycle from mountain building at different stages.
How to cite: Wang, Y., Chen, Y., Li, S., William Hedding, D., and Chen, J.: Oxidation of petrogenic organic carbon and the net geological carbon budget of the Eastern Tibetan Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5191, https://doi.org/10.5194/egusphere-egu25-5191, 2025.
Understanding chemical weathering process and its controlling factors is important for interpreting hydrochemical dynamics in a catchment system. This study analyses solute chemistry, river discharge, and precipitation data from the Kali-Gandaki, a trans-Himalayan River, over four annual cycles. River samples were collected weekly at two sampling locations, upstream (Lete) and downstream (Purtighat), complemented by grab samples from tributaries, springs and main river covering the entire catchment. Concentration-discharge relationships for most elements, including Na+, Ca2+, Mg2+, Li+, Sr2+, SO42-, Cl-, and HCO3-, show dilution behaviour during monsoon with highest elemental concentrations during baseflow season. However, K+ and Si concentrations exhibit chemostatic behaviour downstream. The Ca/Na and Sr/Na ratios increase with increasing discharge in Lete, indicating carbonate mineral dominance during high flow, while Sr/Na ratio decreases downstream, signifying an increased contribution of solutes from silicate rocks. Weathered solute budget from inverse modelling reveals seasonal and temporal variation, with the highest proportions of cations derived from carbonate and silicate occurring during the monsoonal period. Additionally, the relative contributions from these sources increase from upstream to downstream. Carbonate weathering rates at Lete and Purtighat are significantly higher than silicate rates, calculated at (40±8) x104 tons km-2 yr-1 and (73±8) x104 tons km-2 yr-1 respectively, compared to silicate weathering rates of (2±0.1) x104 tons km-2 yr-1 at Lete and (7±1) x104 tons km-2 yr-1 at Purtighat. Weathering rates strongly correlate with discharge, explaining their peaks during the monsoon as well as in downstream. Moreover, the chemical weathering rates also show weak but positive trends with rainfall amounts. On the other hand, the consistent counter-clockwise hysteresis patterns of all elements (except SO42- and Sr2+ in Purtighat), reveal the role of groundwater contribution. Groundwater has long transit times, with extended water-rock interaction periods, resulting in more dissolved elemental concentration compared to the rising limb of fast responding peak discharge. The effect of groundwater can also be supported by the relationship of elemental ratios, such as Na/Si and Li/Si which consistently show decreasing trend with increasing discharge across both sites. During high runoff, the river receives a greater proportion of water with shorter transit times, such as direct surface runoff or shallow subsurface flow. These waters have had limited time to interact with minerals, resulting in lower Na and Li concentrations relative to Si. However, after peak discharge, increased groundwater contribution allows prolonged interaction, enables the groundwater to reach chemical equilibrium with secondary silicate minerals and results in removal of silica from solution and high Na/Si and Li/Si. The findings emphasize the dual role of monsoonal rainfall in enhancing weathering processes, and groundwater contributions in maintaining elevated solute fluxes after the monsoon peak. This interplay underscores groundwater’s role as a buffer system, modulating river chemistry and ensuring consistent solute contributions across varying hydrological conditions.
How to cite: Roy, N., Hovius, N., and Andermann, C.: High Resolution River Chemistry Timeseries Reveal Hydro-Climatological Controls on Weathering Fluxes Across the Himalayan Mountain Range, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13524, https://doi.org/10.5194/egusphere-egu25-13524, 2025.
Bhutan is a landlocked country straddling the Himalayan Arc, with elevations ranging from approximately 170 to 7,600 m a.s.l. Despite these high elevations, large portions of the do not show glacial overprint and are thought to have remained relatively stable in terms of erosion during recent geological history. This unique geomorphological setting is characterized by a quasi-stationary fluvial system and low hillslope erosion, as evidenced by well-preserved sedimentary records and deeply weathered rock horizons along adjacent hillslopes.
This study focuses on two large drainage basins in northwestern Bhutan, which encompass three distinct geomorphic domains: (1) broad alluvial plains with detachment-limited regimes, (2) transport-limited fluvial valleys with steep hillslopes and high relief, and (3) glacially overprinted low-relief landscapes at the base of the High Himalayan peaks. During multiple field campaigns, we extensively mapped the extent and type of sedimentary deposits across numerous outcrops, enabling the creation of a 3D inventory of sedimentary distributions throughout the valleys. These field data are integrated with geomorphological analyses of river profiles and a comprehensive inventory of rock mass weathering degrees to reconstruct the sequence of geomorphic events shaping the contemporary landscape.
Our observations reveal notable contrasts between the two basins. In the Wang Chhu Valley (western basin), broad alluvial plains exhibit minimal terracing, with terrace steps measuring only a few meters in height. In contrast, the Punatsangchhu Basin (eastern basin) features much narrower valleys distinguished by well-defined terraces with elevation differences of several tens of meters. Furthermore, although both basins lie at comparable distances from the range front, the central valleys in the eastern basin are approximately 1,000 m lower in elevation than corresponding locations in the western basin.
The sedimentary deposits also display distinctive characteristics. In the western basin, fluvial sediments are often interbedded with chaotic, sub-angular blocky deposits indicative of gravitational mass movements, such as debris flows. While similar deposits are present in the eastern basin, they are accompanied by lake sediments and thick accumulations of fine-grained, unstructured material containing suspended angular clasts. These deposits are likely associated with a glacial lake outburst flood (GLOF) previously documented in the region.
Combining the spatial sedimentary distribution of the two basins with topographic analyses, we propose a sequence of geomorphic events marked by extensive periods of erosional quiescence forming large fluvial deposits, which are regularly interrupted by phases of heightened hillslope sediment production or even catastrophic events like glacial lake outburst floods.
How to cite: de Palézieux, L., Zeller, M., and Loew, S.: Positive feedback between rates of rock mass weathering and landscape lowering through fluvial and hillslope erosion in the High Himalaya of Bhutan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21650, https://doi.org/10.5194/egusphere-egu25-21650, 2025.
Bedload transport is vital for river dynamics but difficult to measure directly. To address this, we conducted a large-scale field experiment at Landaoxi in the HueiShui Forest Station, featuring a 25-meter-long, 2-meter-wide channel with significant inflow (~1.5 cms) to replicate realistic river conditions. This large-scale setup enabled us to capture complex sediment transport behaviors that are often unobservable in smaller laboratory environments. Six UAVs were used to record the entire experiment, applying Particle Tracking Velocimetry (PTV) to capture surface flow velocity. Additionally, we reconstructed the flow surface using Structure-from-Motion (SfM) techniques.
This study emphasizes the deployment of smart rock technology for direct tracking of bedload motion. Each smart rock, built on Arduino-based controllers, incorporates a 9-axis accelerometer, timer, and SD card reader. The shells were fabricated through 3D printing and molded with epoxy-sand mixtures to match the density of natural particles. Signal processing of accelerometer data facilitated reconstruction of particle paths, velocities, and dynamic responses. Path reconstruction involves integrating the accelerometer data twice to estimate velocity and position. To mitigate drift errors inherent in integration, we applied noise filtering, coordinate alignment using gyroscopic data, and final position correction based on known retrieval locations. Advanced techniques, such as Kalman filtering and cross-validation with UAV-based flow data, were employed to enhance accuracy and ensure reliable path visualization.
The smart rock measurements were compared with (1) seismic signal monitoring and (2) optical fiber sensing. This multi-method approach within a large-scale experimental framework provides new insights into sediment transport processes in river systems.
How to cite: Chan, T.-H., Cheng, Y.-C., Chen, C.-H., Hung, C.-Y., and Chao, W.: Integrating Smart Rocks, UAV-Based Sensing, and Large-Scale Field Experiments for Bedload Transport Analysis in River Systems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14716, https://doi.org/10.5194/egusphere-egu25-14716, 2025.
The big challenge addressed in this study involves understanding Earth surface processes, such as landslides, sediment transport, and bedrock incision, which shape landscapes and link climate, tectonics, and erosion. These processes require long-term monitoring of experimental catchments to capture the full range of timescales involved in their evolution. Hydrophones deployed in stream can record fluvial soundscapes over frequencies from Hz to tens of kHz, which are possibly corresponding to sediment transport. Large-N array geophone deployed along riverbank can also provide additional constraints on bedload flux and turbulent flow using seismic physical models. However, high-frequency of fluvial-related seismic signals are rapidly attenuated before arrival riverine geophones. Discrepancies in frequency contents and sensing space resulted that is difficult to fully connect passive seismo-acoustic signals to fluvial processes. In this study, distributed Acoustic Sensing (DAS) is proposed as possible solution to advance in understanding of sediment transport. DAS not only records strain-rate at meter scales, similar to large-N geophone array, but also monitors frequencies from mHz to kHz, similar to hydrophone. This study aims to establish a river sediment observatory in a mountainous catchment in Taiwan. This observatory will serve as a research and educational hub for long-term monitoring, providing valuable data for sediment transport studies and environmental conservation. We have conducted a preliminary experiment in 2024. The artificial channel segment reach approximately 30 m long, 1 m depth, and up to 3.8 m width, with an average slope of 4°. Based on a series analysis of photogrammetric survey, we measure the flow configurations during experiment with flow discharge ranging from 1.1 m3/s to 1.5 m3/s and flow surface velocity of 1.9 – 3.0 m/s. The riverbed is covered with sediment particles that have D50 before the experiment ranged between 10 mm and 12 mm, all of which were smaller than the D50 values measured after the experiment (15 mm to 22 mm) as derived from pebble scanner using a deep learning model. Regarding the movement of sediment particles, data from smart rocks showed that 8 impacts occurred along the channel; with an average saltation velocity of ~1.5 m/s. The time-series monitoring data from the field channel experiment showed notable time-frequency differences in the microseismic signals at stations located in the concave bank scour and sediment deposition areas. The PSD at the concave bank scour station exhibited stronger PSD energy and a broader frequency range, with a dominant frequency range of approximately 20 – 80 Hz. This was consistent with the time-frequency results from the impact tests. The study hypothesizes that this dominant frequency characteristic is caused by the sediment material saltation effects. Fiber optic records showed that when the upstream flow reached the test area, it caused a strain rate of approximately 10-5/s. We further conduct PSD estimation of in-stream and along-riverbank DAS data to explore spectral characteristics corresponding to riverbed scour, lateral erosion, sediment transport and flow dynamics. The goals in this study include developing new monitoring instruments, validating seismic models, and exploring the impact of extreme events on sediment dynamics.
How to cite: Chao, W.-A., Hung, C.-Y., Chen, Y.-S., Huang, H.-H., Ku, C.-S., Yang, C.-L., and Lin, J.-J.: River sediment observatory in the mountainous catchment: Long-term and high spatiotemporal monitoring with distributed acoustic sensing (DAS), large-N geophone array, hydrophone, smart rock, AI-based grain-size scanner, and photogrammetric survey, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10790, https://doi.org/10.5194/egusphere-egu25-10790, 2025.
Soil erosion is a significant environmental concern that threatens agricultural activities, reduces soil fertility, and eventually impacts productivity. Assessing soil erosion is essential for effective planning and conservation initiatives in a basin or watershed. This study aims to assess water-induced soil erosion using machine learning techniques and identify key factors contributing to erosion vulnerability in a watershed. This study employed three advanced machine learning techniques: Random Forest (RF), k-Nearest Neighbors (kNN), and Extreme Gradient Boosting (XGBoost) - to analyze and forecast water-induced soil erosion patterns. The investigation identifies key factors contributing to soil erosion vulnerability by utilizing a comprehensive dataset derived from Digital Elevation Models, climatic records, and land use patterns. The models were trained on 80% of the data, while the other 20% were used for evaluation, resulting in an accuracy demonstrating their robustness in environmental modeling across various topographic features. The models were extensively assessed using various accuracy measures, including sensitivity, specificity, precision, and the Kappa coefficient. The Area under the Curve (AUC) values for the models were 87% for RF, 89% for kNN, and 91% for XGBoost, indicating high predictive performance. RF, kNN, and XGBoost models demonstrated high sensitivity values (0.9, 0.87, and 0.91, respectively) and specificity (0.9, 0.86, and 0.89). The Kappa index for the ML models was 0.80 for RF, 0.73 for kNN, and 0.80 for XGBoost. These metrics indicated that RF, kNN, and XGBoost are highly effective in identifying water-induced soil erosion in the research region. This study not only identifies critical sites susceptible to erosion but also provides a decision-support tool for evaluating soil erosion within the investigated area and similar riverine ecosystems.
How to cite: Khan, I., Bęcek, K., and Ahmad, S. M.: Machine Learning Approaches for Evaluating Water-Induced Soil Erosion and Its Vulnerability Factors in a Watershed, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2795, https://doi.org/10.5194/egusphere-egu25-2795, 2025.
Landslides, in general, can release large volumes of sediment into rivers, sometimes causing river blockages, outburst floods, or mudflows. Quantifying sediment contributions from landslides is important not only for the resilient development of population in mountainous settings but also to understand river responses to catastrophic sediment inputs.
This study focuses on the watershed of Rivière des Pluies, in La Réunion, a high-standing volcanic island characterised by a particularly dissected topography. In the upper part of this mountainous watershed, a slow-moving landslide (Grand Eboulis) has been recently shown to be remobilised by shallow landsliding, supplying sediment to the river (Hopquin et al., in prep). Such contributions raise societal concerns for downstream populations exposed to flooding, as well as economic challenges due to the proximity of the island’s main airport to the river’s fan.
In this study, using photogrammetry on historical aerial images, we investigated the volume of sediment transferred by shallow landslides between 1978 and 2011. Landslide scars and deposits were mapped from the computed orthoimages, and associated sediment volumes were estimated using difference of Digital Surface Models (DSMs).
Preliminary results show that over the 33 years, 4.21 ± 0.36 Mm³ of sediment were eroded from Grand Eboulis through shallow landslides. In the river, only 0.64 ± 0.14 Mm³ remained, suggesting that the river exported 3.57 ± 0.5 Mm³ of sediment at an export rate of 108 kM³/yr. As the discharge responsible for such transfer depends on precipitation regimes, we will investigate the relationship between precipitation and sediment contributions, as well as between hydrology and the river transport capacity, at a decadal timescale, for intermediate years: 1984, 1989, 1997, and 2003.
How to cite: Hopquin, C., Gayer, E., Michon, L., and Lucas, A.: Quantifying sediment supply to the river from a tropical slow-moving landslide using photogrammetry: the case study of Grand Eboulis, Réunion Island, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16462, https://doi.org/10.5194/egusphere-egu25-16462, 2025.
In mountain drainage basins, channel morphology and river dynamics are heavily controlled by sediment budgets resulting from landslide activity (Schumm 1977, Church 1992, Montgomery and Buffington 1997). Depending on the type and volume of landslide sediments, river velocity, fluvial channel geometry, and the magnitude-frequency of hydro-meteorological events, downstream effects can be dangerous, particularly when the safety of lives and urban areas is threatened. A quantitative estimate of landslide sediment supplies and their influence on the morphology of fluvial systems are crucial information for predicting subsequent sediment transport dynamics, and, therefore, ensuring effective sediment management strategies.
The objective of this study is to provide quantitative estimates of landslide sediment supply to the fluvial drainage network using the Material Point Method (MPM). MPM is a mesh-free physically-based numerical approach where the domain is discretized into material points that can move across a stationary Finite Element (FE) mesh (Sulsky et al. 1994, 1995, Abe et al. 2014, Yerro et al. 2019). The governing equations are solved at the nodes of the fixed computational grid for each new configuration of the material points. This feature makes the MPM more suitable than FE methods for studying large deformation phenomena, such as the propagation of landslide masses.
The numerical method has been applied to study an earthflow event in the Northern Apennines (Italy) validated using multi-temporal DTM reconstructed from drone-based LiDAR surveys. Preliminary results are presented in terms of sediment budget quantification and variations in river cross-section. The comparison between predictions and observations provides valuable insights into the hillslope-channel coupling phenomenon and demonstrates the forecasting potential of the MPM. This preliminary study is a crucial step toward advancing sediment supply forecasting under changing climate scenarios.
AKNOWLEDGEMENTS
This study has been carried out within the Project LASST “evaluating LAndslide Sediment Supply to sTreams and connectivity for sustainable, basin-wide sediment management” 20225S3Y7N_PE10_PRIN2022 - PNR M4.C2.1.1 – Funded by European Union – Next Generation EU - CUP: B53D23006810006
REFERENCES
Abe, K., Soga, K., & Bandara, S. (2014). Material point method for coupled hydromechanical problems. Journal of Geotechnical and Geoenvironmental Engineering, 140(3), 04013033.
Church, M. (1992). Channel morphology and typology. The river handbook, 1, 126-143.
Montgomery, D.R., & Buffington, J.M. (1997). Channel-reach morphology in mountain drainage basins. Geological Society of America Bulletin, 109(5), 596-611.
Schumm, S.A. (1977). The fluvial system. New York u.a: Wiley
Sulsky, D., Chen, Z., & Schreyer, H. L. (1994). A particle method for history-dependent materials. Computer methods in applied mechanics and engineering, 118(1-2), 179-196.
Sulsky, D., Zhou, S. J., & Schreyer, H. L. (1995). Application of a particle-in-cell method to solid mechanics. Computer physics communications, 87(1-2), 236-252.
Yerro, A., Soga, K., & Bray, J. (2019). Runout evaluation of Oso landslide with the material point method. Canadian Geotechnical Journal, 56(9), 1304-1317.
How to cite: Mevoli, F. A., Santangelo, M., Talbot, L. E. D., Soga, K., and Rossi, M.: Forecasting landslide sediment supply to streams using material point method, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8450, https://doi.org/10.5194/egusphere-egu25-8450, 2025.
The Stołowe Mountains in the Sudetes are an area of complex structure, located at the junction of three tectonic units, the boundaries of which show contemporary activity within the study area. While the escape of surface waters into the Stołowe Mountains massif along deep fractures of bedrock associated with the presence of fault zones was already recognised in the 1980s, only in recent years more attention has been paid to the geomorphological effects of this phenomenon.
This study aimed to quantitatively characterize the drainage network of the study area by: (1) Objective delimitation of individual valleys, including valleys in various stages of development and located in areas with different lithology, carried out using hydrological modeling tools, based on a high-resolution DTM. The result, in the form of a vector model of the valley network, became the input data for the subsequent stages of the research plan implementation; (2) Quantitative characterization of the catchment area of the Stołowe Mountains as the basic reference areas in the studies on the heterogeneity, conditions, and development of the drainage network, using indicators related to the shape, asymmetry, and slope of the catchment area and the density of the valley network; (3) Identification of areas most dissected due to increased erosion, using the cluster analysis method, based on multifactorial, geomorphometric characteristics of the entire study area; (4) Indication of the main drainage directions in relation to a) the entire study area, b) main lithological units, c) catchments, d) main drainage areas, e) morphogenetic domains, and f) zones of increased erosion.
The driving force of the geomorphic processes of the valley-slope systems in the studied area is the destabilization of the balance between erosion forces and uplift. That imbalance is expressed by drainage divide migration. The progress of local disequilibrium reduction is recorded in the geometric features of individual valleys.
The study reveals that the valley network of the Stołowe Mountains was created by the interaction of surface and subsurface processes of varying intensity. The genetic diversity of valley forms is manifested in their specific geomorphometric features.
How to cite: Porębna, W.: Behind the scenes of the struggle between rock control and tectonic forces - reading the geologic past through morphometric analysis of valley network, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10049, https://doi.org/10.5194/egusphere-egu25-10049, 2025.
The incision of bedrock by rivers is a key process that controls river morphology, drives valley downcutting, determines the evolution of hillslopes base level, and shapes landscapes. Understanding the mechanisms of fluvial erosion of bedrock is therefore crucial in geomorphology. In this study, we investigate the factors controlling bedrock erosion rates, both experimentally to document the pebble abrasion process and in the field to highlight the respective roles of abrasion and block detachment. Experimentally, we use an annular flume to simulate different hydrodynamic conditions and sediment transport regimes, in order to conduct a parametric study and to explore the influence of sediment size (from fine to coarse gravel size), sediment quantity and flow velocity. Our experiments partly reproduce the semi-theoretical abrasion model of Sklar and Dietrich (WRR, 2004) in particular the dual role of the sediment load: a “tool” effect for gravel quantity lower than the amount required to cover the flume bottom, and an increasing “cover” or protective effect beyond. To complement these controlled laboratory observations, we are carrying out in situ erosion measurements in three different small gorges carved into silt- to sand-stones units across the Himalayan front in Nepal. We use terrestrial Lidar to follow the rocky banks evolution both at a scale of several tens of meters to quantify block detachment rates, and at the scale of locally protruding sandstone bars sediment in order to document the surface abrasion and its spatial variations. This micro-topographic study is complemented by hydrologic measurements and by an in-situ erosion sensor that records the timing of the erosion. These field data provide insight into the mechanisms of bedrock erosion in a monsoon-driven climate. Together, laboratory and field approaches provide a comprehensive framework for understanding bedrock abrasion, with implications for predicting landscape evolution in mountainous river systems.
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Sklar, L. S., & Dietrich, W. E. (2004). A mechanistic model for river incision into bedrock by saltating bed load. Water Resources Research, 40(6).
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How to cite: Delorme, P. and Lavé, J.: Abrasion of river bedrock: from the laboratory to the field, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12017, https://doi.org/10.5194/egusphere-egu25-12017, 2025.
Waterfalls play a critical role in landscape evolution. Waterfalls can control the rate and style that new relief is introduced into a landscape, and, when waterfalls self-form, they can alter channel erosion rates and longitudinal profiles. Here we investigate how waterfalls alter channel form and whether waterfalls might alter erosional processes in adjacent (waterfall-free) reaches and hillslopes. We examine channels located upstream, at, and downstream of waterfalls using channel width, channel slope and waterfall locations extracted from 93 basins in the Front Range of the San Gabriel Mountains in California, USA. While these mountains are thought to be in a large-scale erosional steady state, we find that many channels are in a transient state of adjustment due to the presence of waterfalls. Our results show that waterfalls increase channel slope (up to a factor of 20) and narrow channel width (up to a factor of 3), not only at the waterfall itself, but also up to 100 m upstream and downstream of the waterfall. We explore the influence of waterfall retreat rate on changes in channel form by examining waterfalls that occur across a range of drainage areas (which has been shown to scale with retreat rate). We demonstrate that waterfalls occurring at larger drainage areas have approximately twice the effect on changes in channel width, and may cause channel narrowing four times as far downstream as those at smaller drainage areas. These findings highlight the potential to estimate waterfall retreat rate from spatial changes in channel form. Through examining the different ways that waterfalls alter channel processes, this research illustrates that rivers may be out of equilibrium on a small scale even when they are at a large-scale steady state.
How to cite: Rothman, S. D., Scheingross, J. S., and McCoy, S. S.: Waterfall alteration of bedrock channel form in the San Gabriel Mountains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16311, https://doi.org/10.5194/egusphere-egu25-16311, 2025.
