As a result, tracking the interactions between denudation, climatic forcing, tectonic activity, vegetation and land use is complex. Yet, these feedbacks affect both long- and short-term natural surface processes, landscape evolution, and human-environment interactions. Many of these processes are further intensified by climate change, posing increasing threats to the biosphere, mountain settlements and infrastructure. Understanding and quantifying rates of erosion, weathering, transport and deposition within mountain landscapes is a challenging, but crucial research topic in Earth surface processes.
We welcome contributions that (1) investigate the processes of production, mobilisation, transport, and deposition of sediment in mountain landscapes, (2) explore feedbacks between erosion and weathering due to natural and anthropogenic forcings, including climate change, and (3) examine how these processes contribute to natural hazards specific to mountain regions. We invite presentations that employ observational, analytical or modeling approaches in mountain environments across a variety of temporal and spatial scales. We particularly encourage early career scientists to apply for this session.
Orals: Wed, 6 May, 08:30–12:27 | Room G1
Disentangling tectonic, climatic, and lithologic controls on bedrock river profiles is a central challenge in geomorphology. Landscapes with layered rocks represent an end-member case of lithologic complexity where lithology varies through both time and space, as vertical incision causes contacts between layers to migrate. Recent studies using the Stream Power Model (SPM) have highlighted the complex variations in erosion rates that arise in these landscapes, which cannot reach a typical topography steady state where erosion rates are equal everywhere as long as lithology continues to vary. Instead, these landscapes reach a dynamic steady state where erosion rates in individual layers adjust to achieve a landscape-averaged erosion rate that is balanced with uplift. However, the SPM assumes detachment-limited behavior, omitting the role of sediment. Lithology controls bedrock rivers not only by setting bedrock erodibility, but also by producing sediment that is transported and deposited downstream. Sediment deposited on the channel bed can form a protective layer that inhibits bedrock erosion, known as the cover effect.
In this study, we use the Stream Power with Alluvium Conservation and Entrainment (SPACE) model to quantify how sediment cover effects influence patterns of channel steepness and erosion in horizontally layered rocks. We run a series of simulations modeling landscape evolution through alternating layers of hard and soft rock over million-year timescales, varying the amount of sediment that accumulates on the channel bed across model runs. As sediment cover increases, lithologic knickpoints formed by the contacts between layers become less prominent in the topography, and the effective erodibility contrast between the two rock types is substantially reduced. Additionally, sediment cover effects increase topographic relief and landscape adjustment time compared to the SPM model. Our results demonstrate that identical underlying lithologic configurations produce remarkably distinct channel profiles depending on the degree of sediment cover. This work highlights the importance of considering sediment cover effects when analyzing river profiles, particularly in settings with variable lithology.
How to cite: Guryan, G., Johnson, J. P. L., and Gasparini, N. M.: Sediment Cover Modulates Lithologic Signals in Mountain Rivers: Implications for Channel Profile Interpretation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18890, https://doi.org/10.5194/egusphere-egu26-18890, 2026.
In mountain rivers, sediment from landslides or debris flows can alluviate portions or even full reaches of bedrock channel beds, influencing bedrock river incision rates through the “tools and cover” effect. Various landscape evolution models have been developed to account for the coevolution of alluvial cover and sediment-flux-dependent bedrock incision. Despite the commonality of their aims, one major difference between these models is the way they account for sediment transport length scales. Sediment can be transported over long distances before it settles, and sediment flux depends not only on local topographic and hydraulic conditions, but also on non-local upstream sediment supply and flow conditions. Here, we compare numerical simulations of sediment transport and sediment-driven bedrock abrasion across a range of sediment transport length scales. Our results show that longer transport length scales delay the adjustment of sediment cover relative to changes in sediment flux, thereby modifying sediment-flux-dependent bedrock incision. We further simulate the evacuation of a landslide deposit and examine the resulting bedrock abrasion by the evacuated sediment. For longer sediment transport length scales, sediment accumulates more slowly downstream of the landslide deposit (the cover effect), whereas sediment flux increases rapidly (the tools effect). This mismatch prolongs periods of bedrock exposure under high sediment flux, leading to enhanced bedrock incision. Consequently, variations in sediment transport length scale produce distinct spatial and temporal patterns of bedrock incision during landslide deposit evacuation. Our findings highlight sediment transport length scale as a key control on fluvial responses to episodic sediment inputs in mixed bedrock–alluvial rivers, particularly in tectonically active mountain landscapes where landslides frequently deliver large sediment pulses to river channels.
How to cite: Lai, J., Huppert, K., and Braun, J.: Sediment transport length scales shape the tools-and-cover effect on bedrock incision, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14706, https://doi.org/10.5194/egusphere-egu26-14706, 2026.
River incision into bedrock and thus topographic relief depend on, and also influence, the size distribution of sediment produced on hillslopes and supplied to channels. Sediment size is therefore central to the feedbacks between weathering, sediment production, and channel incision that drive landscape evolution. However, quantifying these feedbacks is challenging due to difficulty in measuring how hillslope sediment size varies at catchment scales and how size distributions evolve as particles are transported through the channel network. Recent work has shown that detrital apatite (U-Th)/He ages measured in all size classes present at a catchment outlet can reveal elevation gradients in sediment size produced on hillslopes. We compared this approach with in-situ grain size measurements on hillslopes at Inyo Creek, which spans 2 km of relief in the Sierra Nevada, California, USA. We find that the two independent data sets do not agree. For example age data suggest that boulders originate at lower elevations whereas sand is produced uniformly across the catchment. The hillslope data show the reverse: spatially uniform boulder production with sand only from lower elevations. This divergence may reflect particle wear during transport from hillslope sources to the catchment outlet; only boulders produced near the outlet arrive at the sampling site intact, whereas sampled sand is a mix of sand produced by particle wear and by weathering on hillslopes.
To explore this hypothesis, we developed a numerical model to predict particle wear and the evolution of grain size distributions by fragmentation and attrition, mechanisms that occur in steep catchments. The model is calibrated with data from two laboratory experiments: individual rock drops to quantify the probability of fragmentation on impact and number of fragments produced as functions of impact energy; and bulk sediment tumbling in 4 rotating drums ranging from 0.2 to 4.0 m in diameter. The wear model can reproduce the variation in wear rates and evolution of grain size distributions in the rotating drum experiments. Wear rates also correlate with energy expenditure in drums of different sizes, permitting extrapolation to the field. We incorporate the wear model into a population balance model to track the evolution of particle size distributions due to wear, mixing of sediments from sources across the catchment, and the transfer of (U-Th)/He ages among sediment sizes. A plausible range of modeled wear rates yields a match between predicted and measured age distributions by size class at the catchment outlet. This holistic picture of the life cycle of sediment grain size links the upstream geomorphic conditions that control hillslope weathering and erosion with the downstream size and abundance of coarse grained tools that control channel incision into bedrock.
How to cite: Sklar, L. and Riebe, C.: Transformation of sediment grain size distributions by abrasion and fragmentation in an alpine catchment: linking hillslope weathering and erosion to bedload transport and channel incision, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14060, https://doi.org/10.5194/egusphere-egu26-14060, 2026.
Recent work has shown both that drainage divides shift location over geologic timescales in response to contrasts in erosion rates and that fluvial and hillslope grain size is correlated with erosion rate, with faster eroding basins tending to have coarser grain size distributions. However, it remains unclear whether (and how) divide migration might impact grain size distributions in eroding watersheds. Here, we investigate hillslope grain size and soil production in two adjacent watersheds with a twofold difference in erosion rates in the Oregon Coast Range, a humid upland landscape in the western United States. This erosion rate contrast is set by the exposure of a resistant dike at the outlet of one watershed, and is likely to have persisted on the order of 0.5 Myr, based on regional erosion rates and the height of the knickpoint. We collected grain size data from soil pits along transects of the migrating divide itself and from sites further downstream in sub-watersheds that drain the migrating divide. We also measured soil depth and soil production rate across the divide to gain insight into the nature of the subsurface divide. Grain size measurements from the migrating divide show that for sediment < 2 mm, the grain size distribution is nearly indistinguishable on each side, while the faster side of the divide has a larger coarse fraction. This difference becomes more pronounced further from the divide. Grain size data further downstream show that the faster eroding basin has systematically coarser grain size distributions, as expected, but the size-dependent patterns seen at the divide are not evident. Soil depth across the divide reveals that the subsurface divide is offset by a few meters towards the slower-eroding side, such that there are deeper than expected soils near the divide. While our data indicate that divide migration does impact hillslope grain size and soil production, the lack of a clear signal of divide migration further downstream suggests that these effects are localized to the scale of the divide itself
How to cite: Sweeney, K., Struble, W., Seeley, M., Patton, J., and Talmadge, J.: Grain size signature of divide migration is restricted to local hillslope scale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13042, https://doi.org/10.5194/egusphere-egu26-13042, 2026.
Bedload is considered a fundamental aspect of river “health” on a global scale. A comprehensive understanding of bedload transport is crucial for ensuring resilient river function and the implementation of sustainable, long-term basin management strategies. In Austria, integrative monitoring of bedload transport has been conducted for a period exceeding two decades, encompassing numerous monitoring stations and projects. Utilising these extensive datasets, we conducted a comprehensive analysis of bedload-discharge relationships in three alpine gravel-bed rivers (Drau, Isel, and Rofenache) to elucidate hysteretic bedload process behaviour and its underlying drivers. Event-scale and seasonal analyses reveal pronounced hysteresis between bedload flux and discharge, with river-specific dominance of clockwise (CW) versus counterclockwise (CCW) loop patterns. CW hysteresis is associated with unrestricted bedload availability, whereas CCW hysteresis indicates limited bedload supply. The direction of hysteresis and the hystereses loop patterns are related to e.g., seasonality (winter, summer, fall, autumn), anthropogenic influences, like channel modifications, flow regulation, barriers or hydropower, and hydro-climatic factors (temperature and precipitation). In the high-alpine Rofenache catchment, CCW hysteresis is predominant, consistent with temperature-driven melt dynamics, delayed sediment mobilisation relative to peak discharge, and the ongoing influence of glacier retreat on bedload supply timing. Across various melt periods, emerging trends indicate a lengthening and shifting of bedload transport windows, thereby offering insights into future dynamics under the influence of climate change. The Upper Drau exhibits clear counterclockwise hysteresis that points to a bedload deficit, primarily driven by anthropogenic influences such as the residual flow reach downstream of a hydropower plant and insufficient upstream sediment input, both of which cause delayed bedload transport relative to peak discharge. In contrast, the Isel shows CW hysteresis, indicating that no bedload deficits were present at the monitoring station during the study period; here, hysteresis loop patterns are a key component of process understanding. The results obtained can inform the development of evidence-based sediment management strategies, as well as habitat restoration and risk mitigation strategies, which can be tailored to the evolving alpine river systems.
How to cite: Schwarz, S., Shire-Peterlechner, D., Lammer, A., Habersack, H., and Rindler, R.: Hysteretic Bedload-Discharge Dynamics in Austrian Alpine Gravel-Bed Rivers: Evidence from Long-Term Monitoring, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19588, https://doi.org/10.5194/egusphere-egu26-19588, 2026.
This study presents eight years of continuous monitoring data on bedload transport dynamics in alpine gravel-bed river systems in Austria, specifically the Urslau and Strobler-Weißenbach rivers, utilizing radio frequency identification (RFID) technology. Stationary antennas were employed to detect embedded RFID tracers, enabling the acquisition of high-resolution data on particle transport velocities, transport distances, and sediment dynamics. A total of 1,612 RFID-tagged stones were deployed, enabling the generation of large and comprehensive datasets on bedload transport dynamics. Seasonal variability and long-term trends were observed at the Urslau stream, while targeted short-term measurements at the Strobler-Weißenbach stream provided crucial insights into flood event dynamics. The study underscores the influence of environmental factors, such as grain size, river gradient, and hydraulic parameters, on bedload transport processes in alpine streams. Additionally, the efficiency of stationary antennas was optimized to ensure uninterrupted monitoring. These findings emphasize the value of advanced monitoring technologies in understanding river processes and addressing emerging challenges, including those posed by climate change and anthropogenic pressures on river systems.
How to cite: Shire-Peterlechner, D., Lammer, A., Schwarz, S., Habersack, H., and Rindler, R.: Dynamics of Bedload Transport in Alpine Gravel-Bed Streams: Long-Term Monitoring Using RFID Technology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18369, https://doi.org/10.5194/egusphere-egu26-18369, 2026.
Climate-driven glacier retreat is fundamentally restructuring sediment transfer systems in Alpine catchments, yet quantifying these changes over timescales relevant to global warming remains challenging. Established approaches to sediment connectivity assessment, such as DEM-based connectivity indices or sediment flux measurements, face limitations when applied across centennial timescales due to inconsistent data quality and sparse temporal or spatial coverage.
We present a graph-theoretic framework for analyzing structural sediment connectivity evolution across three glaciated catchments in the Central European Alps (Grastal, Kaunertal, Martelltal) over approximately 150 years since the Little Ice Age maximum. Our approach derives sediment cascade graphs from multitemporal geomorphological maps, using landforms as fundamental spatial units. The key methodological challenge lies in enabling meaningful comparisons across study sites of different sizes and configurations, and across time periods characterized by heterogeneous source data.
To achieve temporal depth, we integrate diverse data sources: historical topographic maps (1870s–1930s), georeferenced terrestrial photographs, aerial imagery processed with Structure-from-Motion photogrammetry (1940s–1990s), and recent ALS-derived products. Graph creation follows a semi-automatic workflow combining GIS-based flow routing with manual sediment source identification from DEMs of Difference and orthoimagery. We specifically address hydrological sediment connectivity, focusing on fluvial transport processes that dominate sediment export from glaciated systems.
We develop and apply graph metrics designed to be robust against variations in network size and data quality, enabling direct comparison of structural properties across catchments and time periods. These metrics characterize pathway architecture, the topological positioning of barrier landforms (lakes, braidplains, alluvial fans), and potential functional sediment connectivity under event-scale forcing through a simplified routing model.
Results indicate that the three catchments exhibit distinct evolutionary trajectories, with network structural changes and barrier formation capable of substantially modulating the response to deglaciation. The approach demonstrates that graph-based representations can be consistently derived from heterogeneous historical sources, offering a transferable methodology for investigating how sediment cascade structure mediates landscape response to climate forcing across decadal to centennial timescales.
How to cite: Himmelstoss, T., Kara-Timmermann, D., Betz, S., Altmann, M., Rom, J., Stark, M., Haas, F., Becht, M., and Heckmann, T.: Tracking sediment cascade evolution in Alpine catchments since the Little Ice Age: A graph-based approach integrating historical and modern data sources, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18246, https://doi.org/10.5194/egusphere-egu26-18246, 2026.
Sediment redistribution dynamics interest geoscientists greatly as their assessment can help address issues such as soil loss in agricultural areas or the movement of pollutants and sediments toward streams. In mountain landscapes, the variety of gravitational and water-based erosion processes makes redistribution assessments particularly challenging.
The concept of sediment connectivity was defined generally as the degree of linkage between sediment sources and downstream sink areas, and was further distinguished into structural (SC) and functional (FC) connectivity.
SC is the potential connectivity due to the existing topography, most widely assessed using the Index of Connectivity, developed by Borselli et al. (2008) and later improved by Cavalli et al. (2013).
It is an empirical calculation, which is not intended to quantify sediment rates, to capture sub-surface dynamics and changes in time or even whether sediment transfer actually occurs.
The FC has been introduced to represent the actual transfer of water and sediments within the landscape, on the basis of the geomorphic processes and their magnitude.
FC is not as widely adopted and few authors have adopted existing Landscape Evolution Models or LEMs to quantify sediment dynamic across the landscape. So far, FC has only been simulated at the surface.
The aim of this work is to a) assess how time, depth in the soil, grain size, and landscape development affect surface and sub-surface sediment dynamics; b) determine the impact of bioturbation on sediment connectivity; and c) compare sediment redistribution to the Index of Connectivity (Borselli et al. 2008, Cavalli et al. 2013) dynamically after each timestep.
This work was carried out using an adapted version of the mechanistic soil-landscape evolution model LORICA and applied to a mountainous catchment in Tirol, Austria.
The results confirmed that simulating bioturbation affects the vertical redistribution of sediments, transporting surface sediments deeper in the soil profile and bringing deeper sediments to the surface. It also showed that different grain sizes are transported at different rates across the landscape, with finer grainsizes reaching both deeper layers and the outlet of the catchment more rapidly compared to larger ones.
Lastly, transport of material in deeper layers was delayed compared to those on the surface.
The mean Index of connectivity across the catchment was mostly unaffected by bioturbation.
How to cite: Giarola, A. and Temme, A.: Modelling surface and sub-surface connectivity with a mechanistic soil-landscape evolution model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17688, https://doi.org/10.5194/egusphere-egu26-17688, 2026.
Mountain headwaters play a critical role in both water and sediment production, transport, and storage. In Mediterranean regions, their geomorphological and ecological significance is amplified by pronounced climatic seasonality, hydrological variability, and anthropogenic pressures. Central Spanish Pyrenees exemplify these dynamics with steep gradients, land use and land cover (LULC) changes, and climatic oscillations in a natural-regime framework. Understanding short-term geomorphic adjustments in these systems requires high-resolution, event-based monitoring that provides a link between hydrological variability and morphological response.
This study examines hydro-morphological dynamics across four headwater reaches in Upper Aragón Basin (NE Spain), characterized by contrasting altitudinal, sedimentological, and topographical characteristics. Daily discharge records (2012 – 2024) were analysed to assess recent hydrological trends and stablish one- and five-year return period magnitudes. In order to stablish a sediment-mobilizing threshold for each reach, a critical discharge (Qc) was calculated based on D50 sediment fraction. To quantify hydraulic forcing in-between periods, the cumulative excess energy (ΔE) was calculated, integrating discharge exceeding Qc over given survey intervals.
High-resolution topographic surveys were conducted using UAV-SfM photogrammetry following competent flood events. Seven seasonal topographic surveys (2023 – 2025) were carried out with a DJI Mavic 3M drone equipped with multispectral sensors and RTK positioning. To ensure topographic correction and evaluate precision and accuracy, ground control points (GCP) and checkpoints (ChP) were surveyed with an EMLID GNSS-RTK rover, achieving centimetric values (average RMSE: 0.08 m; σ: 0.07 m).. Dense point clouds (130 000 points/m2 average) were processed within a 0.05 m grid to generate Digital Elevation Models (DEM). DEMs were filtered through the application of multispectral indices (GLI, NDVI, NDWI, and WI) to mask vegetation and debris. Successive DEMs were differenced to quantify aggradation – degradation patterns through models of difference (DoD). A variable minimum level of detection (minLoD) was applied across wet and dry areas along with a custom neighbour-based algorithm to identify and remove isolated outliers.
By integrating hydrological thresholds with fine-scale morphological monitoring, this study provides a detailed quantification of sediment mobility and channel adjustment in Mediterranean mountain rivers. The results highlight the influence of discharge variability on short-term morphological response, offering a process-based framework to support sediment management and channel evolution under changing hydro‑climatic conditions.
ACKNOWLEDGMENTS: This work is funded by the European Research Council (ERC) through the Horizon Europe 2021 Starting Grant program under REA grant agreement number 101039181 - SEDAHEAD.
How to cite: Martín-Rodríguez, F. J., Juez, C., and Llena, M.: High-resolution UAV-SfM approach to quantify short-term hydro-dynamics in Mediterranean river systems., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1877, https://doi.org/10.5194/egusphere-egu26-1877, 2026.
Snow avalanches are a natural hazard that is – depending on its size and location – destructive and potentially harmful to humans, livestock and infrastructure. Because of that there is a lot of research on avalanche formation and how to protect residents and mountaineers from them.
However, some avalanches also function as geomorphic agents. This is the case for full-depth glide or wet snow avalanches that release after melting periods with high air temperatures or rain-on-snow events. These avalanches erode sediment and vegetation as they glide over the ground and transport the material to their deposition areas. Since they appear as brownish-grey in the landscape, they are referred to as “dirty snow avalanches”.
So far, no efforts have been made to investigate the influence these dirty snow avalanches have on soil and landscape. Thus, this research aims to bridge the gap by investigating two avalanche slopes of different lithologies in the Tyrolean Alps (Austria): one at the Hahntennjoch (limestone) in the Lechtal Alps and one in the Kraspes Valley (gneiss) in the Sellrain. We analysed in total 24 soil profiles and their soil properties in the avalanche deposition areas and nearby control areas where avalanche activity was presumed absent. Furthermore, an erosional spot in the release area at Hahntennjoch was accessed and investigated.
We will present the results of these analyses and compare avalanche and control sites as well as the two study areas with each other.
How to cite: Koschmieder, M., Mascher, J., and Temme, A.: The Influence of Dirty Snow Avalanches on Soil Development, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1777, https://doi.org/10.5194/egusphere-egu26-1777, 2026.
The deep critical zone both influences and is influenced by soil production and surface erosion in soil-mantled landscapes. However, few studies have examined the links among soil production rates (SPR), bedrock weathering in the deep critical zone, and landscape evolution. Here, we show that the evolution of the deep critical zone is modulated by near-surface residence times, reflecting the interplay between physical fracturing and chemical weathering. We integrate geophysical, geochemical, and cosmogenic nuclide data from the San Dimas Experimental Forest, California, USA. Our results demonstrate that deep bedrock weathering relates to soil production rates in different ways depending on its magnitude. In slowly eroding areas, soil production rates increase with increasing depth of bedrock weathering, reflecting the potential influences of topographic stress. In contrast, in rapidly eroding areas, soil production rates increase as the extent of bedrock weathering becomes shallower, reflecting limited chemical weathering under short residence times. These findings highlight the underappreciated co-evolution of deep bedrock weathering and soil production across the transition from soil-mantled to bedrock landscapes in actively eroding landscapes.
How to cite: Moon, S., Lee, J., Callahan, R., Riebe, C., Sklar, L., Carr, B., Holbrook, S., Flinchum, B., Weinheimer, N., Uecker, R., and Hidy, A.: Co-evolution of the critical zone: soil production and bedrock weathering, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8745, https://doi.org/10.5194/egusphere-egu26-8745, 2026.
Microorganisms contribute to surface processes through the physical and chemical weathering of minerals, yet their influence on landscape evolution remains difficult to quantify. Recently deglaciated landforms provide a natural laboratory to examine early-stage interactions, as freshly exposed surfaces become available to microbial community establishment and rock-to-soil weathering. Here, we compare microbial community composition and potential weathering capacity across a weathering gradient from bare bedrock to saprolite and soil, using DNA-based sequencing (16S rRNA). Sampling in a recently deglaciated basin (~13 ka) in the eastern Sierra Nevada, California, we find that microbial communities in soil and saprolite exhibit higher diversity and an order-of-magnitude enrichment of weathering-related metabolic pathways. In contrast, bedrock communities remain low-diversity and compositionally similar to those reported from newly deglaciated surfaces worldwide, even after ~13 kyr of exposure. These results indicate that microbial communities diverge along two distinct ecological trajectories: in soil-mantled surfaces, microbially mediated feedbacks enhance soil production and surface transformation, while rock surfaces remain effectively locked in low-weathering conditions and ecological stasis over millennial timescales. Together, these findings demonstrate that microbial lifeforms can influence early stages of landscape evolution in recently deglaciated terrains.
How to cite: Ben-Israel, M., Lukens, C. E., and Beman, J. M.: Microbial Weathering Effects on Early Landscape Evolution in a Deglaciated Alpine Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7928, https://doi.org/10.5194/egusphere-egu26-7928, 2026.
Consumption of CO2 through weathering of volcanic arc and ophiolite rocks in arc-collision zones in the humid tropics has been proposed to regulate Earth’s climate over geological timescales. Evaluating this hypothesis requires quantifying the factors that control CO2 consumption from weathering of mafic and ultramafic rocks. Temperature, runoff, and physical erosion may each influence weathering rates. To determine their relative importance for arc and ophiolite rocks, we examine co-variation of stream solutes, sediment geochemistry, and erosion rates inferred from cosmogenic 36Cl in magnetite in an ancient, uplifted arc-collision zone in Puerto Rico. The data reveal contrasting weathering behavior between mafic and ultramafic rocks. Consumption of CO2 from mafic rock weathering is primarily limited by the ability of erosion to strip regolith from the landscape. Conversely, ultramafic rock weathering is more strongly controlled by runoff than by erosion. This difference likely results from the low Al concentrations in ultramafic rocks, which inhibit the formation of aluminosilicate clays and thick regolith. Additionally, we find that CO2 consumption is not limited by temperature for either mafic or ultramafic rocks in the tropics. These results have implications for the role of tropical arc-collision zones in the Earth’s negative silicate weathering feedback.
How to cite: Moore, A., Méndez Méndez, K., Hughes, S., and Granger, D.: Contrasting weathering behavior of mafic and ultramafic rocks in arc-collision zones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18059, https://doi.org/10.5194/egusphere-egu26-18059, 2026.
Earth's last half-billion years exhibit alternating greenhouse and icehouse climate states, but we do not know why. Global climate state reflects atmospheric CO2 partial pressure, a product of volcanic emission and silicate weathering drawdown, modulated by the biosphere. Global climate simulations on geological timescales show temporal correlation with tectonic collisions. However, collision simultaneously terminates arc volcanism and exposes fresh rock for weathering: these processes are hard to deconvolve.
Recent studies have provocatively hypothesised that Earth’s climate state is set by ophiolite obduction in tropical collisions. Here, rapid weathering of reactive rocks efficiently consumes CO2. This hypothesis yields a testable prediction: that the sedimentary archive of ancient tropical orogens will contain ophiolitic detrital minerals at the onset of icehouse periods. Here, we use automated heavy mineral analysis of key sedimentary sections from the New Guinea and Taconic-Grampian orogens to identify and quantify ophiolite detritus. We integrate these data with detrital geochronology and bulk geochemistry to assess ophiolitic weathering contribution to CO2 drawdown.
How to cite: Mark, C., Sharma, N., Lünsdorf, K., and Zack, T.: Did ophiolite obduction in the tropics drive global climate? A detrital sediment perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17582, https://doi.org/10.5194/egusphere-egu26-17582, 2026.
Reconstructing the timing of glaciations and post-glacial erosion rates is essential for understanding past climate variability, the interaction between climatic systems and landforms, and for predicting future glacier behaviour under global warming. Such reconstructions also provide quantitative chronological constraints on landscape evolution. The terrestrial cosmogenic nuclide (TCN) dating technique using 10Be is among the most widely applied methods for reconstructing glacial histories by constraining the exposure ages of moraine boulders that record past glacial activity. However, the measured nuclide concentration is sensitive to post-depositional rock surface erosion, which can lead to an underestimation of exposure ages if not properly corrected. While very low erosion rates (<10-3 mm/a) exert a negligible influence on exposure-age calculations, higher rates (>10-2 mm/a) can significantly underestimate the apparent ages of sampled surfaces. Therefore, exposure and erosion rates are often evaluated using paired-nuclide approach or complementary dating techniques. Furthermore, the selection of different scaling models for cosmogenic nuclide production introduces additional variability and can significantly affect the derived exposure ages. This necessitated the development of a reliable complementary rock surface chronometer. Recently, rock surface luminescence dating (RSLD) has emerged as a promising technique for constraining exposure and erosion rates of rock surfaces. A few recent studies have used a combined approach integrating RSLD with 10Be dating to constrain post-exposure erosion rates and erosion corrected exposure ages. The accuracy of RSLD has been further improved through the application of General order kinetic (GOK) model, which incorporate the non-exponential decay of feldspar IRSL (Infrared Stimulated luminescence) signal within into RSLD modelling. This advanced approach has been applied in Lahaul Himalaya to determine the timing of past glacial activity and quantify post-glacial erosion rates. A total of eleven granitic gneiss boulders were sampled from five morphologically distinct moraine ridges distributed across two catchments within the Jankar Valley. Preliminary analysis revealed that the order of kinetics varied from 2.03 to 2.45, indicating the nonlinear behaviour of feldspar. Furthermore, the exposure ages derived from RSLD were significantly underestimated, suggesting the presence of relatively high surface erosion rates. The erosion rates were estimated by assuming step function erosion history and the values ranged from 64 ± 20 mm/kyr to 236 ± 30 mm/kyr, which are considerably higher than the previously reported rates of 0.8 mm/kyr. These elevated erosion rates are expected to exert a substantial influence on the apparent exposure ages obtained from TCN dating.
How to cite: Pathan, A., Biswas, R., Kumar, D., Murari, M., Kumar, P., and Ali, N.: The first application of rock surface luminescence dating as erosion-meter in Jankar Valley, Lahaul Himalaya, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1598, https://doi.org/10.5194/egusphere-egu26-1598, 2026.
Straddling the Himalayan Arc, Bhutan exhibits an impressive topographic gradient from 170 to 7’600 m a.s.l. Despite these high elevations a defining characteristic of this landscape is the absence of glacial overprint in large portions of the country’s surface. This setting provides a unique opportunity to observe landscape-forming processes such as fluvial erosion and deposition over temporal spans of several glacial cycles.
In this study, we examine two major drainage basins in north-west Bhutan, characterised by three primary geomorphic domains: 1) detachment-limited regimes, characterised by broad alluvial plains followed upstream by 2) transport-limited fluvial systems flanked by high-relief, steep hillslopes which finally transition into 3) low-relief landscapes at high altitudes, which exhibit clear glacial overprinting below the summits of the High Himalayas. Based on the systematic mapping of morphological markers and the collection of soil and rock outcrop records in a series of field campaigns, we have compiled a three-dimensional inventory of sedimentary deposits. To constrain the observed relative age relationships quantitatively, we collected samples for 14C and cosmogenic radionuclide (CRN) dating in key geomorphic locations. These physical observations were then integrated with longitudinal river profile analyses, providing a conceptual model for the geomorphic evolution of the region.
Our findings highlight significant morphological divergence between the two drainage basins. The Wang Chhu Valley in the west is characterised by broad alluvial plains with negligible fluvial bedrock incision and terrace risers only a few metres high. In contrast, the Punatsangchhu Basin in the east shows narrower valleys with prominent terrace sequences between 10 and 50 metres high. Interestingly, despite being in a similar position in relation to the mountain front, the interior valleys of the eastern basin are approximately 1'000 metres lower than those in the west.
In addition to the valley morphology, also the sedimentological characteristics vary by basin. The western deposits consist of fluvial sequences interbedded with chaotic, sub-angular, blocky facies, which are typical of mass-wasting events such as debris flows. The eastern basin contains similar gravity-flow deposits, as well as lacustrine sediments and massive, fine-grained units containing suspended clasts. These are interpreted as signatures of a previously identified glacial lake outburst flood (GLOF).
By integrating spatial sedimentary data with radiocarbon and CRN ages, we propose a model of landscape evolution defined by prolonged erosional quiescence and sediment aggradation. These stable periods are punctuated with episodic pulses of high sediment supply from hillslopes or high-magnitude catastrophic floods, creating the characteristic present-day morphology of the Bhutanese Himalaya.
How to cite: de Palézieux, L., Zeller, M., Haghipour, N., and Loew, S.: Deciphering contrasts in geomorphic evolution across neighbouring mountain catchments in the High Himalaya of Bhutan using radiocarbon and cosmogenic radionuclide dating, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19849, https://doi.org/10.5194/egusphere-egu26-19849, 2026.
Although the topographic evolution and erosion dynamics of the Himalayan range have been extensively documented, it is not known how the very high Himalayan peaks erode. Some conceptual models assume that intense periglacial processes involve regressive erosion of high peak headwalls at rates dictated by valley-floor downcutting of glaciers. However, recent data indicate that frost-cracking intensity decreases with elevation, suggesting instead that highest Himalayan peaks denudation requires a distinct erosional process. Based on the example of the giant collapse of the paleo-Annapurna IV, Lavé et al. (2023) proposed that this erosion occurs episodically and catastrophically during such giant rockslides.
To test this conceptual model and evaluate the modes of sediment export associated with these extreme events, we explored the entire Annapurna massif more systematically. In addition to dating (36Cl exposure age and 14C burial age) several rockslide deposits already described in the literature, we identified for the first time a giant rockslide in the upper Marsyandi Valley (central Nepal). This rockslide, which corresponds to the collapse of the Khangsar Khang paleo-peak during the early-Holocene, formed a huge breccia deposit of ~20 km3 damming the valley and creating the Tilicho Lake (~5000 m a.s.l.).
The cumulative contribution of giant Holocene rockslides in the Annapurna massif represents an average erosion rate of approximately 3 mm/a, equivalent to long-term denudation rate. This equivalence confirms that the main mode of high-altitude erosion could be mega-rockslides that lead to the catastrophic reduction of the high peaks elevation by several hundred meters. This erosion mode of the High Himalaya, associated to steep slopes and high relief, might arise from a higher mechanical strength of the substratum, probably due to the presence of permafrost at high altitude and the absence of bedrock weathering (Lavé et al., 2023).
This major contribution from giant rockslides primarily concerns the denudation of peaks and hillslopes in the High Himalaya. At the scale of the mountain range, the question then arises of the export of breccia deposits produced by these rockslides. Using VolcFlow, a numerical code for granular avalanche flow (Kelfoun & Druitt 2005), we first explore the dynamics of avalanche deposit formation and their final geometry in the upper valleys. Secondly, by comparing with their present residual volumes, we estimate the erosion and export rates of the brecciated deposits. We thus highlight a significant contrast (> one order of magnitude in rates) between the southern flank of the massif, which is directly exposed to the monsoon precipitations and has steeper valleys, and the northern flank, which receives little rainfall. Depending on their location within the range, the giant rockslides can therefore have very different impacts on Himalayan landscape and downstream river evolution.
How to cite: Lave, J., Huber, M., Khatiwada, S., and Scholtes, L.: Giant collapses of high Himalayan peaks and their impact on the erosion of Himalayan landscapes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18286, https://doi.org/10.5194/egusphere-egu26-18286, 2026.
The Ciprnik complex landslide in the Planica valley (NW Slovenia) triggered on 19. 11. 2000 and measured approximately 80,000 m3. Its movement was characterised by three distinct stages of transport mechanism: a translational landslide-debris flow-hyperconcentrated flow. It occurred due to local geological structure (highly fractured beds dipping parallel to the surface), lithology (alternation of Upper Triassic thin bedded carbonates and fine-grained clastics), and record-breaking monthly rainfall. On the night from 24. to 25. 10. 2023 a large part of the landslide was reactivated during an intense short-duration rainfall event. In this study we analysed surface changes of the area affected by the Ciprnik complex landslide following the 2000 event, performed a sedimentary analysis of the 2023 event and analysed the meteorological data to assess the triggering precipitation conditions. We created a surface-changes time-series spanning between 2006-2023 based on photogrammetrically derived Digital Elevation Models generated from publicly available aerial photographs and our own Unmanned Aerial Vehicle surveys. Granulometric analysis was performed on fourteen samples collected along the transport-depositional area of the 2023 event. Additionally, publicly available meteorological records were analysed. The results show that the area of the Ciprnik complex landslide remained unstable with an average annual erosion rate of 1,000 to 3,500 m3. The 2023 event measured 26,000 m3 and had identical transport mechanism stages as the initial one with very pronounced finning-down of the transported sediment. The proximal material of the debris-flow stage was composed of muddy sandy gravel with approximately 75% of gravel, 15% of sand and 10% of mud. Further down the slopes the granulometry of debris-flow stage fined down containing only 40% of gravel, 45% of sand and 15% of mud fraction. Only fine-grained material travelled in the hyperconcentrated flow stage composed of approximately 40% sand, 50% silt and 10% clay. Both events however differ in the duration and magnitude of the triggering precipitation. The 2000 event was triggered by long-duration low-intensity rainfall, which had record breaking quantities (613.6 mm in the month of the event). The 2023 event was triggered by intense short duration rainfall event (104.2 mm in 24 hours), which relatively commonly occurs in the study area. This case study of the Ciprnik complex landslide demonstrates the complexity of triggering thresholds in the aftermath of the main mass movement event. Even in the later events, which have identical transport mechanisms as the original event, the triggering precipitation can differ considerably in duration and magnitude.
How to cite: Novak, A., Vrabec, M., and Šmuc, A.: History often rhymes: evolution and reactivation of the Ciprnik complex landslide (Julian Alps, NW Slovenia), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11196, https://doi.org/10.5194/egusphere-egu26-11196, 2026.
Erosion often poses a great challenge in simulating hazardous multi-phase mass flows as it drastically changes the flow behaviour, impact force, run-out and deposition morphology by dramatically increasing their masses. Here, the comprehensive, unified mechanical erosion model for multi-phase mass flows (Pudasaini, 2025) is implemented for the first time in to the GIS-based open source computational tool r.avaflow. The model includes the frictional, collisional and viscous stresses. The consistent basal erosion rates for solid and fluid phases are based on the mechanically derived, dynamically flexible interacting stresses across the erosion-interface between the landslide and the bed. The model physically correctly includes the essentially composite erosion velocities of the mobilized particles and fluid from the bed and utilizes them to architect erosion-induced net momentum productions that consider all the interactions between solids and fluids in the landslide and the bed. This overcomes severe limitations inherited by existing erosion models. This mechanically-explained, comprehensive multi-phase model for erosive mass flows realistically embeds the erosion velocities, unified mechanical erosion rates and the net momentum productions into the mass and momentum balance equations. As the model makes a complete description of multi-phase erosive landslide dynamics by considering all essential aspects including the correct handling of inertia, the simulation results clearly demonstrate the physical essence of the new mechanical model substantiating the erosion-induced enhanced mass flow mobility with the net momentum production. This offers unique opportunities for practitioners in appropriately solving technical, engineering and geomorphological problems related to complex erosive multi-phase mass flows with r.avaflow.
Pudasaini, S. P. (2025). A comprehensive, unified mechanical erosion model for multi-phase mass flows. International Journal of Multiphase Flow, 191, 105328. https://doi.org/10.1016/j.ijmultiphaseflow.2025.105328
How to cite: Pudasaini, S. P.: Simulating multi-phase erosive landslides with r.avaflow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8743, https://doi.org/10.5194/egusphere-egu26-8743, 2026.
Posters on site: Tue, 5 May, 14:00–15:45 | Hall X3
The role of mountain building in regulating Earth’s climate remains unclear, as uplift and erosion can drive both CO2 drawdown via silicate weathering and CO2 release via carbonate dissolution by strong acids and oxidation of petrogenic organic carbon. Understanding how erosion rate, climate, and lithology influence these reactions is key for understanding the impact of the growth and subsequent erosion of the Himalayan Orogeny on atmosphere pCO2.
We present comprehensive long-term inorganic carbon budgets linked with millennial-scale cosmogenic denudation rates across 65 river tributaries of the Alaknanda, Bhagirathi, Tons, Yamuna, and Pabbar rivers, which together form the headwaters of the Ganges. These catchments span wide gradients in erosion rates, climate zones, and underlying geology. For each catchment, we combine basic geochemical measurements with δ34SSO4, δ18OSO4, and δ18OH2O analyses to quantify the proportion of sulfate derived from pyrite oxidation to the net inorganic carbon budget. We calculate long-term CO2 fluxes from inorganic sources and combine these estimates with new and existing in situ cosmogenic 10Be measurements to independently constrain denudation rates. Denudation rates for unsampled catchments are extrapolated using a stream-power-law regression between discharge-weighted channel steepness and measured denudation.
Preliminary results reveal strong contrasts in both the magnitude and direction of net CO2 fluxes across the High Himalayan Crystalline Sequence (HHCS), Lesser Himalayan Sequence (LHS), and Tethyan Sedimentary Sequence (TSS). The LHS catchments exhibit dominant silicate weathering and sustained long-term CO2 drawdown, whereas for the TSS and HHCS catchments sulfide oxidation coupled to carbonate dissolution reactions are prominent and outpace CO2 drawdown by silicate weathering reactions. Long-term denudation rates correlate with CO2 fluxes, but subtleties exist between the differing morpho-tectonic units. These findings provide new constraints on the spatial controls of weathering processes in the Himalaya and their net impact on Earth’s long-term carbon cycle.
How to cite: Stevenson, E., Frings, P., Wittman, H., Scherler, D., Clementucci, R., Sen, I., and Strauss, H.: Long-term CO2 fluxes across erosional and lithological gradients in the Himalayas, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18220, https://doi.org/10.5194/egusphere-egu26-18220, 2026.
Understanding the relative control of tectonics and climate over denudation rates has been a driver of scientific research over the past decades, especially in mountainous regions. In the Alps, although millennial-scale denudation rates range over two orders of magnitude, it is generally accepted that these are largely driven by the topographic overprint left by the Quaternary glaciations. However, tectonic uplift rates also vary substantially across the range, complicating this interpretation. Apatite (U-Th)/He ages from the Niedere Tauern indicate Late Miocene to Early Pliocene exhumation, attributed to tectonic activity given the very regional scale of this exhumation. This region, which is also ideally located at the eastern margin of the Last Glacial Maximum (LGM) ice extent, is therefore an ideal natural laboratory for investigating the controls on Quaternary glaciations in the Alps.
We present new 10Be-derived denudation rates of 17 catchments of the Eastern Alps, 10 of which are located within the Mio-Pliocene uplifted Niedere Tauern, and 7 outside of it. The 3 easternmost catchments of the Niedere Tauern are located at the edge of the LGM ice extent. Combined with previously published cosmogenic nuclide data from the region, this dataset allows us to investigate whether present-day denudation patterns primarily reflect the imprint of Quaternary glaciations, or the longer-term tectonic control associated with Mio–Pliocene uplift.
How to cite: Large, E., Gong, L., Mariotti, A., and Sobel, E.: Disentangling the Tectonic vs. Glacial control over millennial-scale denudation rates of the Niedere Tauern, Eastern Alps, Austria, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9996, https://doi.org/10.5194/egusphere-egu26-9996, 2026.
Enhanced sediment export from high-alpine mountain catchments strongly affects fluvial systems and reinforces the risk of damage to valleys downstream. Changes in precipitation regimes induced by climate change are expected to modify geomorphological activity, erosion processes, and sediment transfer, potentially leading to increased sediment fluxes in alpine rivers. Despite increasing attention to climate-driven geomorphic change, a detailed understanding of sediment transport processes and their response to variations in meteorological forcing remains limited.
This study aims to improve the understanding of recent and historic sediment dynamics in a high-alpine catchment, the Habach Valley, located in the Hohe Tauern National Park (Austria), by integrating topographic change analyses with information on historic meteorological conditions.
We calculate multi-temporal DEM of Difference (DoD) for the time span 1953 – 2023 to detect hotspots of frequent sediment redistribution and quantify erosion volumes. Complemented by information from historical hazard archives, we further evaluate the SPARTACUS precipitation dataset to reconstruct meteorological conditions and link formative extreme events to sediment mobilization and redistribution within the catchment.
First results reveal persistent hotspots of sediment mobilization and redistribution in the observed period, predominantly located within the riverbed and depositional landforms on the slopes and within the cirques. The detected surface changes are mainly related to gravitational and fluvial processes and redistribution along the sediment cascade.
How to cite: Dietel, S., Dremel, F., Healy, S., Robl, J., and Otto, J.-C.: Linking Past Erosion Processes with Weather Dynamics in the Habach Valley, Hohe Tauern, Austria, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3901, https://doi.org/10.5194/egusphere-egu26-3901, 2026.
Soil erosion is a critical factor causing structural changes in the natural environment by inducing vegetation reduction and topographic alterations, making it a vital subject of analysis from a geomorphological perspective. Jirisan National Park, the first national park in South Korea, holds immense symbolic value and rich ecological resources that necessitate high conservation priority. However, its vulnerability to erosion has been increasing recently due to intensified tourist activities and natural disasters driven by rapid climate change.
This study quantitatively estimated soil erosion rates in Jirisan National Park by adopting fallout radionuclide analysis (Cs-137 and exPb-210), a method that has not yet been widely applied in South Korea. The analysis revealed that the overall average soil erosion rates were 1.51±0.21 t/ha/yr based on the Cs-137 method and 2.65±0.2 t/ha/yr based on the exPb-210 method.
Regarding the spatial distribution characteristics of each radionuclide, the erosion rates derived from Cs-137 showed a distinct pattern, being relatively higher in the eastern part of Jirisan compared to the western part. In contrast, no significant difference in erosion rates based on location was observed for exPb-210. These results suggest that the distribution of heavy rainfall and intensive precipitation, influenced by the recent migration paths of typhoons which have been more pronounced in the eastern region, has directly impacted the erosion rates.
By scientifically clarifying soil erosion rates-a key indicator of topographic change-through radionuclide analysis, this study provides essential baseline data for establishing precise environmental conservation and soil resource management strategies for Jirisan National Park. It holds significant academic and policy implications for future conservation efforts.
Keywords: Soil erosion rate; Fallout radionuclides; Spatiotemporal distribution; Jirisan National Park
How to cite: Shin, Y., Kim, Y., Ki, S., and Kim, J. K.: Estimation of Soil Erosion Rates and Spatiotemporal Distribution Characteristics in Jirisan National Park Using Fallout Radionuclides, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9098, https://doi.org/10.5194/egusphere-egu26-9098, 2026.
Understanding the interactions between Earth's surface processes, climate, and tectonic forcing remains challenging due to the inherently stochastic nature of erosion and sedimentation. Landslides exemplify this stochasticity while dominating sediment production in steep mountain landscapes. Here, we investigate landsliding and sediment-storage dynamics in the Southern Alps of New Zealand, where differences in tectonic advection and a strong orographic precipitation gradient create a pronounced west-to-east contrast in erosion rates that differ by approximately an order of magnitude across the Alpine drainage divide. These contrasts, largely driven by landslide activity, provide an exceptional opportunity for evaluating how distinct process domains regulate sediment production, storage, and evacuation.
We combined terrestrial cosmogenic radionuclide measurements (14C and 10Be) with single-grain K-feldspar post-infrared infrared stimulated luminescence (post-IR IRSL) signal analysis of modern fluvial sediments to constrain sediment sources and residence times. Our preliminary results indicate that while the western catchments exhibit 14C/10Be ratios of ~11 to 69, well above the nuclide production rate ratio of ~3, indicating landslide-dominated sediment supply, eastern catchments show lower ratios of 2 to 8, reflecting mixed sediment dynamics: landslide contributions in some catchments (with ratios >3) whereas significant sediment buffering in others (with ratios <3). Two-isotope plots (14C-10Be) further reveal minimal storage (negligible to a couple of hundred years of burial) for landslide-dominated western catchments, indicating rapid evacuation of eroded materials and complex exposure histories in eastern catchments record burial durations of ~2000 to 5000 years, demonstrating substantial sediment storage, reworking, and a correspondingly buffered erosional signal.
Unexpectedly, our post‑IR IRSL results do not reflect these contrasting process domains very clearly. Mean equivalent doses show substantial overlap between western (~45 to 177 Gy) and eastern (~40 to 128 Gy) catchments, with no systematic distinction between landslide-dominated and storage-dominated systems. We propose that high doses in western catchments reflect incomplete bleaching of landslide-evacuated sediment coupled with rapid transport, while elevated doses from eastern catchments result from competing processes such as partial or incomplete bleaching of episodic landslide-derived materials from steep slopes and progressive signal accumulation during prolonged storage. These observations thus warrant further systematic investigation of topographic controls, including landslide frequency-magnitude analysis to fully resolve luminescence behavior across erosional process domains.
How to cite: Biswas, A., Karman-Besson, L., Guyez, A., Riedesel, S., Fülöp, R.-H., Binnie, S. A., Bonnet, S., and Reimann, T.: Quantifying sediment production and storage dynamics in the tectonically active Southern Alps of New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10996, https://doi.org/10.5194/egusphere-egu26-10996, 2026.
Mountain landscapes show strong spatial variability in sediment production, with long-term erosion often being concentrated in specific areas. This local variability complicates disentangling the relative contribution of different sediment sources and understanding how their signals evolve downstream through dilution, temporary storage, and deposition. Here, we address these questions by characterizing sediment sources and tracing their sedimentary signals along the river network of the 4,300 km² Alpine Rhine basin (Switzerland).
We use concentrations of in-situ cosmogenic ¹⁰Be from riverine quartz collected at 75 sites - and paired ¹⁰Be-²⁶Al data from 45 of them - to quantify erosion rates and identify the relative importance of landsliding versus overland flow erosion on the generation of sediment. We complement these data with information on the bulk geochemical compositions from the same sand samples. We synthesize the geochemical and cosmogenic dataset into mixing models with the goal to identify sediment sources and quantify their relative contributions to the mixed downstream signal.
The concentrations of 10Be show that erosion rates range widely from ~0.3 to 2 mm yr⁻¹. In addition, paired cosmogenic nuclides indicate negligible burial and highly efficient sediment evacuation across all spatial scales. Although they additionally show evidence for localized input of material from landslides, the majority of paired cosmogenic nuclide samples reveal that sediment generation through overland flow erosion has been the most important mechanism. Finally, the cosmogenic nuclide concentrations in combination with the geochemistry information reveals that sedimentary signals are generated in basins at small scales (<200 km²). Modelling of sedimentary pathways reveals that the signals are generally well mixed for basins >200 km2, where the riverine material reflects mixtures of multiple source signals generated at smaller scales. Yet we also find that locally generated signals can disproportionately influence downstream records. This is particularly the case where stochastic mass-wasting events episodically overprint basin-scale signals through high-magnitude sediment inputs. In contrast, signals generated through overland flow erosion become well mixed for basins >200 km2, and a further differentiation between potential source signals is no longer possible.
How to cite: Garipova, S., Mair, D., Akçar, N., Christl, M., and Schlunegger, F.: Tracing source-to-sink sedimentary signals across scales in the Alpine Rhine Basin (Switzerland), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10009, https://doi.org/10.5194/egusphere-egu26-10009, 2026.
High mountain and polar regions are among the most impacted by present-day climate change, with cryosphere degradation altering geomorphic processes and sediment dynamics. These changes affect ecosystem functioning, hydrogeomorphological hazards, and sediment fluxes from glaciated catchments to the ocean. Understanding sediment transport mechanisms in proglacial rivers is thus crucial for predicting how sediment dynamics in these regions will evolve under continued climate warming.
Here, we advance understanding of sediment dynamics in ice sheet-fed proglacial rivers by applying a coupled luminescence–modelling approach to the Qunnguata Kuussua river (Watson river) in south-western Kalaallit Nunaat (south-western Greenland). We build on the work of recent studies which have shown that luminescence signals in modern alluvial sediments can serve as sediment tracers and, when combined with numerical models, provide constraints on transport distances, velocities and storage times (Gray et al., 2018; Guyez et al., 2023).
We collected a large dataset (~600 samples) of portable-reader luminescence measurements on bulk sandy sediment samples along the ~30 km-long Watson River during three summer melt seasons (2021–2023). The luminescence signal intensities of different samples are highly variable near the river source (Russell and Leverett glacier termini) and at junctions with tributaries, while the inter-sample signal variability reduces following progressive signal bleaching (i.e. resetting) with increasing downstream transport distance. To interpret and quantify this pattern, we develop a probabilistic luminescence-based sediment transport model that simulates suspended particle transport and luminescence bleaching in a proglacial river. The model successfully reproduces the observed downstream evolution of luminescence signal distributions observed along the Watson River, enabling estimation of sediment transport parameters from combined luminescence and hydrological data.
References
Gray et al., 2018, Geophysical Research Letters 45.
Guyez et al., 2023, Journal of Geophysical Research: Earth Surface 128.
How to cite: Serra, E., Gray, H., Perchanok, F., Bouscary, C., Gevers, M., Delaney, I., Anderson, L., Agostini, L., Kjeldsen, K. K., Schmidt, C., and King, G.: Constraining sediment dynamics in proglacial rivers: novel insights from a combined luminescence-modelling approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17555, https://doi.org/10.5194/egusphere-egu26-17555, 2026.
Flood frequency and magnitude in the Himalaya are projected to increase over the next century due to accelerating glacier melt and more intense monsoons. Most research has focused on the upstream triggers of floods, such as glacial lake outbursts, avalanches, or intense rainfall. Entrainment of sediment stored within mountain valleys as they travel downstream can transform these floods into debris or hyperconcentrated flows, increasing both their travel distances and downstream impacts. This hazard cascade means the risk to downstream communities is conditioned not just by the trigger events but also the distribution of sediment fill along the flow path. However, controls on the spatial and temporal dynamics of sediment accumulation in mountain valleys are poorly constrained due to a lack of systematic, large-scale datasets that capture both channel sediment and landsliding in steep mountain catchments. Inventories of slow moving landslides, which can also supply sediment to channels, are even more scarce. Therefore, our understanding of how shallow and slow landslides contribute to stores of channel sediment in these catchments is limited.
Here, we apply (semi-) automated approaches to generate inventories of channel and hillslope sediment stores for the Alaknanda Basin systematically through time, using a combination of deep learning and remote sensing data. Using these inventories, we develop a framework that explores connectivity between hillslope and channel sediment. We assess whether certain topographic and/or channel characteristics control the spatial and temporal dynamics of sediment supply and fill. We will use these findings to gain a better understanding of the role sediment stores in mountain landscapes that are highly susceptible to sediment-rich flood events.
How to cite: Harvey, E., Clubb, F., Milledge, D., Sinclair, H., Sinha, R., Kumar, V., Chen, Q., Devrani, R., Mudd, S., Nava, L., Naylor, M., Van Wyk de Vries, M., and Yadav, A.: Connectivity between hillslope and channel sediment stores and links to cascading hazards in the Indian Himalaya , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19884, https://doi.org/10.5194/egusphere-egu26-19884, 2026.
Sediment-discharge events recorded at the outlet of high-mountain catchments provide an integrated signal of upstream geomorphic activity. At the same time, a key limitation of DEMs of Difference (DoDs) is that sediment source areas and geomorphic responses cannot be directly linked to individual events, especially when DoDs span extended time periods. To address this, we apply the method proposed by Skålevåg et al. (2024) to detect, cluster and characterise sediment-discharge events, which can subsequently be related to observed sediment mobilization signals in the DoD.
15-min time series of water discharge and suspended sediment concentration from Gepatschalm, Kaunertal (Austria), covering the period 2008-2025, were used to detect the sediment-discharge events and derive 16 metrics, which were used to cluster the events with a Gaussian mixture model. Gridded meteorological data were used to characterise the clusters with respect to antecedent and intra-event forcing conditions. The resulting event catalogue was evaluated using DEMs of difference (DoDs) covering the entire catchment and investigation period.
Over the 16-year period we identified a total of 850 sediment-discharge events. Clustering results reveal three patterns: (i) melt-dominated events (average contribution ~30% to annual suspended sediment yield), (ii) early- and late-season freeze–thaw-modulated events (~15%), and (iii) compound rainfall–melt events (~33%). A marked increase in event frequency was observed in 2022, which also recorded the highest annual suspended sediment yield in the dataset. The majority of 2022 events were assigned to clusters 2 and 3. Combining multiple DoDs from summer 2022 with gridded precipitation data allowed the identification of a distinct sediment-discharge event on 28 June 2022, which triggered fluvial erosion in a specific sub-catchment of Kaunertal. For this event and other events, the main sediment source areas can clearly be delineated with the DoD analysis.
Skålevåg, A.; Korup, O.; Bronstert, A. (2024): Inferring sediment-discharge event types in an alpine catchment from sub-daily time series. In: Hydrology and Earth System Sciences Discussions.
How to cite: Kara-Timmermann, D., Himmelstoss, T., Betz-Nutz, S., Rom, J., Altmann, M., Stark, M., Haas, F., Becht, M., and Heckmann, T.: Clustering of suspended sediment-discharge events and linking them to upstream geomorphic signals in a high-alpine catchment using DEMs of difference (2008–2025), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13308, https://doi.org/10.5194/egusphere-egu26-13308, 2026.
The understanding of fluvial erosion processes during extreme rainfall events is often limited by the lack of detailed pre-event topographic, sedimentological, and hydrological data. This study explores the 2024 extreme rainfall event in the Guarda Mor River experimental basin, Southern Brazil, based on a comparison of hydrological and topographic information obtained before, during, and after the event. The event, driven by a rainfall volume of 435 mm in 31 hours and an estimated peak discharge of 700 m3s−1, generated a unit stream power capable of greatly exceeding channel stability thresholds. To evaluate the impact of flow on fluvial erosion, pre- and post-event topographic and grain size data were compared, focusing specifically on a 130 m reach upstream of the monitoring section. Additionally, the hydrological study compared the hydraulic behavior of the channel using velocity and water level data from the basin’s existing monitoring program. The approach combined: (i) geomorphological change detection via DEM of Difference (DoD); (ii) characterization of the bed sedimentary restructuring via surface and subsurface grain size analysis; and (iii) changes in hydraulic geometry and flow resistance. The results reveal a complete “geomorphic reset” of the channel. The DoD quantified a substantial morphological reconfiguration, including an average channel widening of 24% and a transition from upstream erosion (max. −0.73 m) to massive downstream deposition (max. +1.19 m). Sedimentologically, the event energy was sufficient to break the pre-existing armoring layer, reducing the armoring ratio from 7.9 to 4.9 and causing intense winnowing of subsurface fines. This revealed a striking hydro-geomorphic duality: despite significant coarsening of the surface layer (D50 increased from 192.5 mm to 249.6 mm), the structural reorganization led to a “hydraulic smoothing” phenomenon. Flow resistance decreased drastically (Manning’s n dropped from ≈ 0.040 to ≈ 0.020), resulting in higher flow velocities and a transition from a subcritical to a critical/supercritical regime (Fr ≥ 1). The event redefined the channel into a new, hydraulically more efficient state, in which the erosive process altered fluvial morphology, bed configuration, and roughness to accommodate the occurring discharges, magnitudes that, apparently, tend to become more frequent. However, due to the breaking of the armoring, the bed is now in a state of latent instability and greater sensitivity to future events.
How to cite: Feyh, G. A., Minella, J. P. G., Saatkamp, E. D., Buligon, L., Merten, G. H., Bernardi, F., da Silva, C. C., Costa, A. G., and Dambroz, A. P. B.: Geomorphic change in the Guarda Mor River resulting from the extreme event of 2024, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4115, https://doi.org/10.5194/egusphere-egu26-4115, 2026.
Rock weathering is crucial for regulating carbon transformation across the Earth's spheres. While silicate weathering is considered kinetically limited, pyrite-driven carbonate weathering and rock-bound organic carbon oxidation are supply limited. As the control of supply limitation depends on reactant mobility, availability, and reactivity, weathering intensity can vary dynamically from the reactant generation to exhaustion at outcrop to catchment scales. How these contrasting weathering regimes operate in terrains with steep topography and deeply incised rivers remains largely unconstrained. The failure of a landslide-induced dam in the Matai’an river in the Central Range of eastern Taiwan delivered approximately 50 million cubic meters of sediments along the river bank (~17 km between landslide dam and lower reach) on September 23, 2025. By combining the dam residue, the total amount of landslide deposits was estimated to be 320 million cubic meters. Such an enormous quantity of materials (primarily composed of schists and marbles) freshly produced by mass wasting and fluvial processes on a monthly scale could be reactive for CO2 production, thereby providing an unparalleled opportunity to constrain the fluxes and governing processes of carbon cycling at the incipient stage of major landscape change in orogenic belts.
To investigate how extreme and what mechanism CO2 evasion is manifested by material supply, direct measurements of CO2 gas flux were conducted using a modified closed chamber method. Our measurements for more than 100 sites yielded gas accumulation at a rate spanning from 0.4 to 60 g-C/m2/d with a median value of 16 g-C/m2/d. The fluxes were not correlated with sediment temperature, sediment depth, or distance to the active channel, a pattern in contrast to the temperature-dependent flux for sedimentary rock setting. This range ranks among the highest ever reported for weathering processes in mountainous catchments. Analyses of carbon isotopic compositions further revealed that the collected CO2 was predominantly sourced by pyrite-driven carbonate dissolution, with minor contributions from rock-bound and soil organic carbon. By integrating the surface area of sediment coverage along the river, the enormous generating capacity of reactive materials from the landslide renders the CO2 emissions exceeding the baseline level inferred from prior riverine chemistry by at least an order of magnitude. Our results demonstrate that the transient and extremely hazardous landscape change in active orogenic belts jumpstarts carbon evasion through rapid weathering of bank sediments at a pace that can substantially alter the catchment-scale carbon budget.
How to cite: Lin, L.-H., Wang, P.-L., Lien, W.-Y., Tsai, J.-F., Wang, L.-Y., Chuang, C.-K., Fu, C.-C., Yen, J.-Y., Roering, J., and Lai, L. S.-H.: Extreme CO2 evasion from channel deposits produced by devastating failure of landslide induced dam in eastern Taiwan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8641, https://doi.org/10.5194/egusphere-egu26-8641, 2026.
In terrestrial landscapes, neighboring catchments that experience contrasting erosion rates can be in disequilibrium such that drainage divides migrate. Cross-divide differences in measured erosion rate can indicate whether a drainage divide is stationary or mobile, and fluvial and hillslope morphologic proxies for erosion rate are often used to infer divide motion. However, these morphometrics do not measure the morphology of the divide itself. Furthermore, these metrics often neglect processes that spatially disconnect the divide from nearby fluvial channels, particularly debris-flow dominated valleys. Here, we test the efficacy of alternate morphometrics that correspond to nonfluvial processes proximal to the divide and compare our results to traditional divide-stability morphometrics (“Gilbert Metrics,” channel steepness, χ). Specifically, our alternate morphometrics are: Adf, a measure of the extent of debris-flow dominated channels, and hilltop curvature, CHT, within each drainage basin. Finally, we quantify the asymmetry of hilltop curvature of the main drainage divide – termed Casym – which represents the only morphometric that measures the drainage divide itself. We investigate these descriptors of landscape form in three landscapes that exhibit a range of uplift and erosion rates, as measured with cosmogenic nuclides in river sands: the Oregon Coast Range (OCR) and Ozark Plateau, Arkansas, both humid landscapes with moderate and low erosion rates, respectively, and the San Gabriel Mountains (SGM), California, a semi-arid region with high erosion rates.
We find that across all landscapes, classic morphometrics like channel steepness, χ, and the Gilbert Metrics can generally estimate divide mobility. However, the accuracy of these metrics differs and depends on measurement scale, and they are subject to assumptions regarding spatial variability in lithology, tectonics, and climate, as has been previously noted. Similarly, we find that the ability of Adf and CHT to predict divide mobility is dependent on the dominant processes within each landscape as well as the magnitude of erosion rate. For example, in landscapes like the SGM where debris flows are common at high erosion rates, Adf accurately predicts divide migration, whereas it struggles to record migration at low erosion rates in the OCR and Ozarks. In contrast, we find that catchment-averaged CHT is an effective proxy for divide migration in the OCR and Ozarks, but becomes ineffective at the most rapid erosion rates in the SGM, where hillslopes become devoid of soil as erosion rates exceed soil production rates. Notably, in all landscapes, we observe that Casym accurately predicts divide migration, indicating that asymmetry near the hillcrest can be captured by curvature morphometrics that isolate each side of the mobile divide. Overall, our results encourage an ensemble approach to predict divide migration, with attention paid to whether morphometrics faithfully record dominant surface processes in a landscape.
How to cite: Struble, W., Sweeney, K., Talmadge, J., Patton, J., and Seeley, M.: Local hilltop and debris-flow morphometrics predict drainage divide migration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5877, https://doi.org/10.5194/egusphere-egu26-5877, 2026.
Mountainous landscapes often contain sediment-filled valleys that control ecosystem diversity, flood hazards, and the distribution of human populations. Valley-floor geometry has been shown to correlate with climate proxies such as discharge or drainage area and is also influenced by lithology and tectonic uplift. However, the relative importance of these controls remains poorly constrained, and no global dataset of valley geometry currently exists.Here, we focus on the automatic mapping of valley floors at the scale of entire mountain ranges. We compare two methods for extracting valley floors from digital elevation models, based on different conceptual definitions. The first is a geometric approach following Clubb et al. (2017, 2022), which defines valleys as low slope areas with a low relative elevation to the nearest river. The second is a new method that identifies valleys as floodplains using a simplified hydraulic model that locally distributes water across flat surfaces adjacent to channels. We evaluate and calibrate both methods by comparison with maps of alluvial cover in four catchments spanning a wide range of tectonic and climatic settings: the European Alps, Scottish Highlands, Pyrenees, and Taiwan. Both methods achieve comparable agreement with alluvial data, although the geometric method is more sensitive to calibration parameters. We compute valley width along the stream network by identifying valley centers and measuring the distance to valley margins, allowing us to quantify the scaling between valley width and drainage area. The scaling relationships of width with drainage area shows exponents ranging from 0.3 to 0.5, consistent with values reported in the literature, with an inter-catchment variability. We show that large-scale valley extraction also allows a more precise characterization of valley networks by identifying local deviations from width–area scaling by using a wideness index similar to the steepness index for channel gradient, and by extracting additional valley attributes such as slope and elevation. This study paves the way for a global analysis of valley morphology to better constraints its dependency to climate, tectonic and geological conditions the controls acting on it.
How to cite: Lurin, A., Steer, P., Clubb, F., and Gailleton, B.: From Local to Global: Systematic Valley Floor Extraction for Characterizing Valley Width-Area Scaling in Mountainous Landscapes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18272, https://doi.org/10.5194/egusphere-egu26-18272, 2026.
All widely used fluvial landscape evolution models rely on a power-law scaling between discharge and drainage area. In settings with relatively high relief and low permeability, this assumption is often sufficient to capture landscape-scale fluvial dynamics and migration of drainage divides. What happens to geomorphic dynamics when those assumptions break down? For example, carbonate karst systems can move massive amounts of water through the subsurface, sometimes against local topographic gradients. To address this question, we introduce a framework for landscape evolution based on the dissipation of the potential energy of precipitation as it takes both surface and subsurface flow paths. We demonstrate the utility of this framework by comparing the widely used “streampower plus diffusion” landscape evolution model with one in which water can take flow paths both over the surface and through the subsurface, responding to groundwater hydraulic head gradients. The framework explains how large carbonate plateaus like the Swabian Alb in southern Germany can persist and stall drainage capture despite a massive river profile asymmetry between Rhine and Danube catchments. Finally, we suggest that in such layered rock systems, the combination of contrasts in lithologic strength and permeability are primary controls on landscape evolution.
How to cite: Litwin, D. and Malatesta, L.: Draining the fluvial battery through groundwater and surface flow: energy partitioning and fluvial landscape evolution, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2895, https://doi.org/10.5194/egusphere-egu26-2895, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 3
EGU26-6006 | ECS | Posters virtual | VPS26
High-energy sediment dynamics in ephemeral Andean mountain streams: The case of Río Seco, PeruTue, 05 May, 14:06–14:09 (CEST) vPoster spot 3
Ephemeral mountain streams on the western Andean slopes remain dry most of the year, yet during intense rainfall events they generate short-lived flash floods with exceptionally high sediment transport capacity. This study investigates the hydraulic response of the upper Río Seco micro-basin (Huaycoloro catchment, Peru) under extreme rainfall scenarios, using a hydraulic–geomorphological framework that links surface hydrology with sediment mobility thresholds. Design discharges were estimated through IDF-based rainfall analysis and classical hydrological methods, while sectional hydraulic modelling using the Manning equation provided flow velocities and bed shear stresses along representative channel reaches. Results indicate mean velocities ranging from 2.4 to 3.4 m/s and shear stresses up to 215 Pa. These values exceed the critical shear stress of the coarse gravel bed by more than five times, indicating generalized sediment mobility and strong incision potential in confined steep reaches. Such conditions promote significant sediment supply from the upper basin, increasing the likelihood of downstream channel aggradation and flood hazard in peri-urban sectors of eastern Lima. To our knowledge, this is the first hydraulic–geomorphological quantification of sediment mobility thresholds in an arid Andean micro-basin under design-storm conditions. The findings provide quantitative evidence supporting the need to transition from purely water-based flood models toward sediment-inclusive risk assessments in steep ephemeral mountain catchments.
How to cite: Rosales Torres, L. and Cárdenas-Gaudry, M.: High-energy sediment dynamics in ephemeral Andean mountain streams: The case of Río Seco, Peru, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6006, https://doi.org/10.5194/egusphere-egu26-6006, 2026.
