There is general agreement that environmental changes and global warming are leading to increased frequencies and intensities of extreme weather and climate events. Such extreme events include, e.g., temperature extremes and droughts, heavy precipitation, storms, pluvial floods and river floods. Scientific studies on possible effects of the increasing frequency and/or intensity of such extreme weather and climate events on geomorphic processes and related earth surface systems are of particular importance as they are addressing key challenges related to the environment in which we live.
This session presents contributions from earth scientists that include a wide spectrum of processes, approaches, methods and techniques, like, e.g., dating, sedimentary records, GIS, remote sensing, observational records, monitoring, experimental studies, and modelling. Several studies have wider systematic relevance and implications, and some presentations highlight contributions of geomorphological research to the ongoing debates on the effects of global environmental changes on geomorphic processes and natural and anthropogenically modified earth surface systems, and for the development of suitable and sustainable mitigation, management and adaption strategies and actions.
This session is co-organized by the IAG Working Group on Denudation and Environmental Changes in Different Morphoclimatic Zones (DENUCHANGE).
Orals: Tue, 5 May, 16:15–18:00 | Room -2.93
Climate change is rapidly reshaping hydro-geomorphological processes in cold regions. Melting glaciers and thawing permafrost are altering how and when sediment is mobilized, creating sediment supplies that are highly sensitive to warming and shifting precipitation patterns. During heavy rainfall and/or intense melting, this abundant and readily mobilized sediment can lead to substantial increases in sediment fluxes, triggering episodic sediment transport events widely observed in permafrost watersheds. These events are typically characterized by the complex co-occurrence of multiple factors such as transient and complex flow conditions, temporarily enhanced erosivity, and dynamic sediment availability. However, widely applied empirical, process-based, and data-driven sediment-transport models (e.g., rating curves, SAT, HydroTrend, SWAT, WBMsed) commonly assume stationary parameters or simplified process dynamics and tend to underestimate both the magnitude of episodic sediment transport. Artificial intelligence (AI)–based data-driven models, including machine learning and deep learning algorithms, have emerged as powerful tools for suspended sediment concentration modeling due to their ability to represent nonlinear and nonstationary processes. Using twenty years of hydrological observations, we found that the drivers of sediment transport now show distinct seasonal variations. To better capture these complex and seasonal shifting processes, we developed a modified deep learning model to learn seasonal differences in sediment transport and dynamically adjusts its predictive weights. It performs substantially better than current widely applied models including rating-curves, processes-based and random forest models, particularly during extreme sediment transport. Our results demonstrate the promise of integrating AI with process understanding to simulate highly variable sediment dynamics under changing climate and cryosphere conditions.
How to cite: Zhang, T., Li, S., Kettner, A., Jiang, S., Farquharson, L., Li, Y., and Li, D.: AI-enhanced simulation of sediment transport in cold regions , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-401, https://doi.org/10.5194/egusphere-egu26-401, 2026.
Extreme weather events, i.e., heavy rainfall, trigger widespread mass movements, producing large volumes of unconsolidated sediments that continue to shape geomorphic processes long after the event. However, the post-event evolution of precipitation-triggered landslides remains much less known, especially in paraglacial mountain systems. This study examines the decadal evolution of landslides in the Mandakini catchment, Uttarakhand, India, a landscape characterised by three distinct geomorphological zones: the lower fluvial, middle paraglacial, and upper glaciated regions. Using multi-temporal LISS-IV and PlanetScope imagery (2014–2023), the characteristics and activity of landslides were assessed across these zones. Results show that landslide activity peaked immediately after the 2013 Kedarnath disaster and declined gradually, although there was an increase in activity in 2018, 2020, and 2023, with clear geomorphic controls. The fluvial zone exhibited the highest landslide densities and continued reactivation, whereas the paraglacial zones were largely characterised by debris flow-type landslides that remained largely dormant, except for renewed movement in 2023. High-intensity short-duration rainfall emerged as a major trigger regardless of antecedent moisture, driving a marked surge in new landslides and debris flows during the 2023 monsoon. Additionally, anomalously high winter precipitation coincided with elevated debris-flow activity in the paraglacial zone, suggesting a significant role for snowmelt, which is likely to intensify under rising temperatures. Roughly 40% of the landslide-impacted area was fully revegetated by 2023. These findings highlight how a paraglacial terrain, rainfall extremes, and evolving snowmelt patterns collectively shape long-term slope sensitivity, with implications for hazard assessment and targeted mitigation in the Himalayas and similar environments worldwide.
How to cite: Sekar, A. and Siva Subramanian, S.: Extreme weather event-driven evolution of mass movements over upper, middle, and paraglacial zones of a Central Himalayan catchment , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1152, https://doi.org/10.5194/egusphere-egu26-1152, 2026.
Climate change is strongly affecting sediment dynamics in the highly sensitive proglacial areas of high-mountain environments, as accelerated glacier melt and permafrost degradation expose new surfaces to erosion, while changing precipitation patterns influence erosion rates and sediment transport. Quantifying these changes is crucial for assessing geomorphological evolution, anticipating natural hazards, and evaluating the responses of both proglacial and downstream ecosystems. However, this task remains challenging as sediment yields from these landscapes are governed by complex interactions among moraine activity, glacial erosion, paraglacial adjustment, and channel morphology, with ongoing climate change further modulating the timing and magnitude of these processes.
This study aims to quantify temporal changes in sediment fluxes in the Sulden proglacial area in South Tyrol, Eastern Italian Alps, from 2005 to 2025, and to assess the role of climate variability in driving these changes. We used high-resolution digital elevation models (DEMs) from 2005, 2017, 2021, 2023, and 2025 to compute multi-temporal DEMs of Difference (DoDs) and derive mean annual sediment fluxes for each interval. Unequal interval lengths can bias flux estimates because short-lived peaks associated with extreme precipitation events may be averaged out over long periods. To address this, we calculated mean annual sediment flux over cumulative intervals starting in 2005 (2005-2017, 2005-2021, 2005-2023, and 2005-2025), providing a framework to evaluate whether, and to what extent, recent changes in precipitation patterns influence longer-term mean flux estimates.
Our results show that mean sediment fluxes, referenced to 2005, have increased sharply and nonlinearly over time, spanning more than one order of magnitude by 2025 and revealing a clear acceleration relative to the 2005-2017 baseline. Comparison of the non-overlapping intervals 2005-2017 and 2017-2025 further emphasizes this shift, with mean fluxes during 2017-2025 approximately 40 times higher than during 2005-2017, indicating a fundamental increase in sediment export efficiency rather than short-term variability around a stable long-term mean. Interestingly, periods with similar amounts of erosion reveal contrasting amounts of deposition along low-slope fluvial pathways within the proglacial system, illustrating how functional connectivity controls sediment storage and ultimately sediment export. Precipitation records indicate an increase in the frequency of high-magnitude rainfall events after 2017, including more frequent exceedances of daily extremes and events approaching or exceeding a 10-year return period.
Together, these findings suggest that the increasing frequency of extreme precipitation events is a key driver of enhanced sediment yields in proglacial environments, with important implications for sediment-related hazards and associated management costs.
How to cite: Pandey, A., Heckmann, T., Cavalli, M., Crozi, M., Mura, F., Andreoli, A., Zucca, F., and Savi, S.: Decadal-scale changes in sediment export from an Alpine proglacial area linked to an increasing frequency of rainfall extremes: evidence for an emerging sediment-export regime shift?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6221, https://doi.org/10.5194/egusphere-egu26-6221, 2026.
The routing of sediment from source to sink is commonly described as a “jerky” conveyor belt, in which sediment flux is strongly controlled by connectivity between source areas and transfer zones. However, the extent to which extreme flood events increase source connectivity and modify sediment transfer through river reaches via combined hillslope and fluvial processes remains poorly understood. The increasing availability of multitemporal, high-resolution lidar now enables the development of event-scale topographic sediment budgets, providing new insights into sediment flux during extreme events.
In February 2023, the landfall of Cyclone Gabrielle caused catastrophic flooding along the eastern coast of the North Island of Aotearoa New Zealand. Repeat lidar surveys were acquired for three catchments—Esk (264 km²), Aropauanui (158 km²), and Tangoio (71 km²)—to quantify landscape change and develop catchment-scale sediment budgets. Sediment delivery ratios were estimated to be approximately 0.4 across all three rivers, with sediment volumes delivered to the marine environment of 9.6 × 10⁶ m³ for the Esk, 5.1 × 10⁶ m³ for the Aropauanui, and 2.4 × 10⁶ m³ for the Tangoio.
Sediment budgets were further refined through geomorphic mapping and two-dimensional flood modelling to partition sediment sources and sinks into geomorphic process zones. The sediment routing model D-Cascade was used to route upstream sediment supply, combined with hillslope-derived inputs along the reach, through individual river sections. Results identify river reaches where observed sediment fluxes exceed modelled fluvial transport capacity, indicating locations where debris-flow-dominated transport processes likely governed sediment routing during the cyclone. These findings demonstrate the potential importance of non-fluvial processes in shaping sediment transfer during extreme floods and highlight the value of lidar-based sediment budgets for resolving sediment dynamics at the event scale.
How to cite: Stout, J., Rogers, J., and Brasington, J.: Jerky conveyor belts under stress: sediment connectivity and routing during an extreme flood event in New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15722, https://doi.org/10.5194/egusphere-egu26-15722, 2026.
Alpine alluvial fans and debris flow cones are central components of the sediment cascade. The projected increase in heavy precipitation due to ongoing climate warming is thought to intensify sediment redistribution dynamics under transport-limited conditions. However, alluvial fan response to increasing heavy precipitation has been shown to strongly differ between individual catchments. In this study, we compare decadal-scale planimetric dynamics of a mature alpine alluvial fan (“Friedergries”, 5 km2 catchment area) to juvenile debris flow cones (Lake Plansee, catchment areas mostly < 0.5 km2) in the Main Dolomite region of the Northern Calcareous Alps. We show that the juvenile cones corresponding to small and steep catchments are susceptible to moderate precipitation while floodplain dynamics on the mature fan are only susceptible to extreme precipitation events with supra-regional extent. Our observation indicates that sediment redistribution on juvenile cones with small and steep catchments will shift towards spring and autumn, corresponding to the seasonal shift of moderate precipitation extremes (1-year return level). In contrast, sediment redistribution on mature fans with larger, gentler catchments will continue to occur mainly in summer, as supra-regional extreme events with return levels > 1 year will occur during the hottest months also in a changing climate (Brönnimann et al., 2018). Here we show that catchment morphology and fan maturity control future susceptibility to rainstorms and thus sediment fan evolution over the coming decades.
Brönnimann, S., Rajczak, J., Fischer, E.M., Raible, C.C., Rohrer, M. & Schär, C. (2018): Changing seasonality of moderate and extreme precipitation events in the Alps. – Natural Hazards and Earth System Sciences, 18: 2047 – 2056. DOI: 10.5194/nhess-18-2047-2018.
How to cite: Gewalt, P., Wagner, T., Barbosa, N., Kiefer, C., and Krautblatter, M.: Juvenile and mature alpine sediment fans respond differently to rainfall intensification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6585, https://doi.org/10.5194/egusphere-egu26-6585, 2026.
As extreme hydrological events become increasingly frequent and intense, there is a growing need for innovative approaches to systematically monitor their impacts on riverine landscapes. This need is especially crucial in human-modified river systems, where such events can have significant consequences on the surrounding anthropized areas. The Po River in Italy exemplifies this challenge, having experienced an unprecedented drought in 2022—its lowest streamflow in two centuries—followed in 2024 by one of the most hydrologically intense years on record. This sequence of contrasting extremes makes the Po River an ideal case study for investigating morphological adjustments and assessing river sensitivity to hydrological variability.
We leveraged Sentinel-2 satellite imagery collection, spanning 2017 to 2025, on a 130-km-long segment of the Po River. A free, globally applicable Fully Convolutional Neural Network was employed to automatically classify monthly median composite images and delineate the active channel—defined as the area encompassing both flowing water and adjacent exposed, unvegetated sediment bars. We generated a continuous, updatable time series, identifying the emergence of progressively activated areas or regions undergoing gradual vegetation colonization (“deactivated” areas). By analysing changes over multiple years rather than on a year-by-year basis, this method more effectively distinguishes areas that consistently remain active or inactive from those that fluctuate between these two states. That helps separate changes driven by varying water stage from those resulting from morphological modifications, e.g. bank erosion.
Our analysis reveals that the 2022 drought was part of an extended period of hydrological scarcity lasting nearly three years. During this time, all reaches of the Po River experienced a net loss of active channel area due to vegetation encroachment. By comparing these trends with a 2022 LiDAR-derived Relative Elevation Model, we demonstrate that vegetation encroachment expanded into topographically lower zones closer to the low-flow channel that had not previously supported vegetation. This indicates a significant shift in morphological setting and ecological dynamics. The hydrologically intense conditions of 2024 triggered unprecedented bank erosion and the widespread reactivation of previously abandoned areas, particularly those deactivated during the preceding dry years. Interestingly, not all areas reactivated in 2024 persisted into 2025. We show that patterns of reactivation and the new activation of floodplain areas depend on river configuration and the degree of artificial confinement. While some reaches restored the active channel width to pre-drought levels, others have not yet fully recovered, suggesting that changes in vegetation establishment may have induced long-lasting morphological adjustments.
This approach provides a practical and scalable tool for global river monitoring, enhancing our understanding of river sensitivity to a rapidly changing climate.
How to cite: Cecchetto, M., Matteligh, E., Vanzani, F., Bozzolan, E., Brenna, A., Taffetani, E., Surian, N., and Bizzi, S.: Biogeomorphic River Response to an Unprecedented Hydrological Drought: Evidence from the Po River (Italy) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5330, https://doi.org/10.5194/egusphere-egu26-5330, 2026.
Given the accelerated pace of climate change (increased droughts and the frequency of intense rainstorms) and human-induced land-use changes, this work assesses the magnitude of their effects on slope evolution in the Serra do Mar mountainous domain of Rio de Janeiro, SE Brazil. Morphological, historical, and functional approaches were integrated to evaluate the conditions controlling landslides in response to Holocene bioclimatic changes and present-day environmental dynamics, with emphasis on the role of fire in intensifying these phenomena. Past processes dynamics were inferred through geomorphological, chronostratigraphic, and palynological evidence. Current studies include geological-geotechnical, hydro-geomorphological, and vegetation analysis; classification of landslide susceptibility and comparison with the January 2011 landslide inventory; monitoring rainfall and soil suction in fire-affected vegetation (degraded forest and herbaceous-shrubby vegetation); in situ tests of Ksat and fire-controlled field experiments. Regionally, colluvial deposits mark distinct landslide episodes throughout the Holocene, with local recurrence intervals of about 300 years. Variations in δ13C and palynological analyses suggest significant transformations in vegetation cover during the Mid-Holocene, with a predominance of herbaceous-shrubby post-fire vegetation and pioneer species; spores and pollen grains with mechanical damage, indicative of a high-energy transport environment, attest to landslide transport. Charcoal fragments in colluvial deposits suggest frequent paleofires during the Holocene. Nowadays, recurrent short-term fires (<10 years) replace forests with herbaceous-shrubby vegetation, where most of the landslides (70%, N=382) from the 2011 catastrophic event are concentrated. At some slopes, fires create a hydrophobic layer in herbaceous vegetation, and short roots (≤30 cm deep) reduce evapotranspiration, keeping soil conditions near saturation at 1,5 m depth, even during prolonged droughts. Post-fire, soil suction increases in the upper soil meter in both vegetation types, within a five to six-month delay. During the following rainy season or extreme rainfall, soils tend to saturate completely, leading to rapid suction loss and excess pore pressure that could trigger landslides. In degraded secondary rainforest, dominated by pioneer and early-succession species that sustain rapid hydrological responses to rainfall, the absence of functional anchoring roots would increase the likelihood of landslides.
How to cite: Coelho-Netto, A. L., Facadio, A. C., Bolsas, L., Ishimine, K., and Silva, R.: HOLOCENE AND PRESENT-DAY EVIDENCES OF RECURRENT POST-FIRE LANDSLIDES: geomorphological responses to climatic and environmental changes., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22181, https://doi.org/10.5194/egusphere-egu26-22181, 2026.
I will present work demonstrating how stochastic theory can be used to establish a scale-bridging understanding of landscape evolution. The scales of interest here include individual erosional events to continental-scale landscape evolution. The theory is used to embrace the unknowability of erosional processes operating at small scales over the lifetime of a landscape. It is used to establish analytical expectations of landscape form and its variance when the probabilities of forces driving and resisting denudation have defined distributions. The results provide a basis for the widely used stream power erosional model that is rooted in first principles. It also quantifies the (often considerable) uncertainty in predictions generated using deterministic models such as stream power, e.g. when probability distributions of driving and resisting forces significantly overlap. Landscape form and its variance can be estimated for arbitrary stochastic driving forces and erosional thresholds extremely precisely and efficiently with a simple algorithmic approach that has links to cellular automata. I demonstrate how such approaches can be used to generate predictions that match those of partial differential equations (PDEs, e.g. the stream power model) at large scales, whilst avoiding many of the limitations, pitfalls and challenges with modelling landscape evolution with PDEs (e.g. assumptions of continuity, numerical stability, management of shockwaves). Stochastic theory is shown to provide means to relate physics-, laboratory- and field-based insights and measurement to landscape form at larger scales. I speculate on how this work might be useful for developing a better, probabilistic, understanding of landscape evolution across scales.
How to cite: Roberts, G.: Bridging scales from single denudational events to continental-scale landscape evolution with stochastic theory, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3119, https://doi.org/10.5194/egusphere-egu26-3119, 2026.
It is widely stated that atmospheric warming, together with an increasing frequency of rainfall events, enhance the activation of sediment sources, erosion and sediment-transport processes in cold-climate environments, with these increases being mainly driven by cryosphere degradation. In this study we compare the effects of ongoing environmental changes on measured sediment yields in three different cold-climate environments in Norway: (i) partially-glacierized drainage basins (Bødalen and Erdalen, connected to the Jostedalsbreen ice cap, western Norway), (ii) one drainage-basin system with discontinuous permafrost (upper Driva, central Norway), and (iii) one boreal drainage-basin system free of permafrost (Selbusjøen, central Norway). Our study includes the multi-year (>10 yr) monitoring of fluvial solute and sediment transport using a range of different advanced techniques. In the partially-glacierized drainage basins mechanical denudation dominates over chemical denudation. Most sediment transport occurs during pluvial events in fall, followed by thermally-determined glacier melt in summer, and thermally-determined snowmelt in spring. An increasing frequency of extreme rainfall events leads to increased sediment yields whereas smaller amounts of wintry snow and the ongoing retreat of outlet glaciers are not causing a detectable increase of sediment yields. For the drainage-basin system with discontinuous permafrost it is found that global warming and the connected shifts in the ratio of snow and rain, the increased frequency of heavy rainfall events, and the continued thawing of permafrost have complex effects on denudation, with an increasing importance of pluvially-induced denudational events, a decreasing importance of snowmelt-induced denudation processes, and an increasing dominance of chemical denudation over mechanical denudation. Also in the boreal environment an increasing importance of pluvially-induced denudational events, a decreasing importance of snowmelt-induced denudation processes, and an increasing dominance of chemical over mechanical denudation can be observed. As a result, the different cold-climate environments respond differently to ongoing environmental changes. A significant increase of mechanical denudation due to cryosphere degradation cannot be detected in our study areas while an increased frequency of pluvial events causes an enhanced activation of sediment sources and rising mechanical denudation.
How to cite: Beylich, A. A. and Laute, K.: Effects of environmental change on the activation of sediment sources in different cold-climate drainage basins in Norway , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19301, https://doi.org/10.5194/egusphere-egu26-19301, 2026.
Abstract: Mountainous regions are now subject to more recurring flash floods than they were in the past decades. These recurring flash floods are attributed to short-duration extreme precipitation events, which are driven by climate change. Mountainous flash floods are far more hazardous as they trigger landslides, activate debris flows, and carry a large amount of dead wood, which can destroy entire valley infrastructure such as roads, bridges, and dams. Moreover, in response to these floods, valley rivers (confined or partially confined) also undergo geomorphological transformation, owing to debris flows. The sediment transportation activates processes like bank erosion, channel incision, bed alteration, and overbank aggradation both at the spatial and temporal scales. In June 2024, a mountainous flash flood led to dreadful destruction of the Valnontey catchment located in Cogne, Valle d’Aosta (northwestern Italian Alps). Not only was the valley infrastructure destroyed within a few hours, but the valley river network also experienced significant geomorphological changes due to the activity of debris flows and landslides. Intensive Post-Event Campaigns (IPECs) were carried out to quantify the flash flood and its geomorphological impacts in the Valnontey catchment. The 24-hour cumulative rainfall was estimated to be approximately 120 mm, and the reconstructed peak discharge ranged between 200 and 250 m³ s⁻¹. This is why in alpine catchments, where the real-time data on flood events is almost absent, post-event studies of hydro-geomorphological response to extreme rainfall events can be extensively found in the literature. However, the impact of resulting geomorphological changes to a flood event, mainly the channel widening, is generally not considered in flood hazard assessment and mountain river basin management, and so the study of all associated factors to geomorphological changes during high-magnitude floods remains a significant research gap. In this study, the analysis of geomorphological dynamics and channel response to such a flood event has been performed, with a principal focus on channel widening. The widening, a geomorphic response to flood events, of the main channel in the Valnontey basin was investigated quantitatively through manual digitization of channel margins using GIS tools. The methodological framework was based on multitemporal high-resolution pre-flood orthophotos and a LiDAR survey acquired immediately after the flood event (August 2024). It was observed that the main channel was predominantly widened because of floodplain island erosion and bank erosion processes that supplied sediments to the main channel. Statistically, the channel response, usually expressed as the width ratio (post-event width/pre-event width), was analysed in relation to channel bed slope and stream power. The results indicate that channel widening was controlled not only by extreme rainfall intensity and stream power (hydraulic factor), but also by morphological characteristics, including lateral confinement, channel bed slope, sediment availability, transport mechanisms, and hillslope–channel coupling.
Keywords: Alpine catchments; Extreme rainfall; Flash floods; Channel widening; Flood hazard
How to cite: Nawaz, A., Dallan, E., Crema, S., Cavalli, M., Ferraris, S., Comiti, F., and D’Agostino, V.: Geomorphological Response of the Valnontey River Basin (NW Italy) to the Extreme Rainfall Event of June 2024, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5951, https://doi.org/10.5194/egusphere-egu26-5951, 2026.
Rivers are dynamic, with channel size and shape adapting to fluctuations in water and sediment supplied from their upstream catchments. These changes directly affect flood conveyance capacity, yet sediment transport processes are often overlooked in flood hazard prediction and management, where channels are treated essentially as static pipes through landscapes. Recent global floods show this assumption can be flawed, as extreme rainfall events can liberate and transport vast volumes of sediment, and in doing so potentially amplify flood hazard.
Here we show, using a prototype catchment in the UK and rainfall data, including that derived from an extreme event associated with Storm Desmond in 2015, the critical role of intra-event sediment transport on flood inundation levels. Our analysis reveals a substantial increase in flood inundation volumes compared to projections that exclude sediment transport processes. Extending these simulations to a range of storm scenarios, we find that both event duration and intensity can significantly influence sediment-driven flood amplification processes, with longer-duration floods of the same magnitude increasing inundation.
These findings underscore the need to consider incorporating intra-event sediment fluxes into flood hazard assessments and that failing to address and integrate these processes could underestimate future risks under climate change.
How to cite: Wolstenholme, J., Skinner, C., Hackney, C., Perks, M., and Parsons, D.: The role of sediment transport in amplifying flooding, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13856, https://doi.org/10.5194/egusphere-egu26-13856, 2026.
Disentangling human signals from geomorphic, tectonic, and climatic drivers of contemporary sediment fluxes is key to understanding the magnitude of human impacts on river basins and the landscape. Denudation rates derived from cosmogenic radionuclides (CRN) can provide a useful baseline of ‘natural’ sediment fluxes, especially in regions where little to no undisturbed catchments remain or where contemporary monitoring networks are lacking. However, their integration time can span very long timescales (up to 100kyr), which may limit their suitability for establishing contemporary natural rates of sediment export. Here, we investigate whether (and where) CRN-derived denudation rates are representative of current climatic, geomorphic, and tectonic conditions and can provide relevant contemporary baseline fluxes. We do so by first compiling hundreds of contemporary sediment yield (SY) observations from ‘quasi-natural’ catchments worldwide. We define quasi-natural catchments as ones with little to no expected disturbance to their sediment transport regime due to anthropogenic changes to the landscape or river system (e.g., land cover/land use, dams and reservoirs, mining). In addition to clear indicators of human disturbance such as the degree of regulation of the river network or the human footprint in the catchment, we base our selection of quasi-natural catchments on a combination of biome-specific thresholds and patterns of acceptable semi-natural vegetation, land cover classification, and potential natural vegetation maps. We then compare a global denudation rate model (trained on >4,000 CRN samples) against the contemporary SY observations and examine possible global and regional patterns of correlation. We further explore the potential of integrating both types of data into a combined global natural SY model, with the goal of further improving our understanding of nature- vs human-driven sediment dynamics worldwide.
How to cite: Tan, F., Campforts, B., Vanacker, V., Borrelli, P., and Vanmaercke, M.: Are CRN-derived denudation rates representative of contemporary natural sediment fluxes?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16773, https://doi.org/10.5194/egusphere-egu26-16773, 2026.
The badlands of southwestern Taiwan lie within an active fold-and-thrust belt, where surface geology mainly consists of a thick Plio-Pleistocene mudstone formation. In the absence of fluvial markers of river incision, we investigate relief and hypsometry within the badlands as potential proxies for long-term (0.1-1 ka) tectonic uplift. In parallel, hypsometric curves allow us to assess the balance between tectonics and erosion.
We selected three badland sites located at different structural positions, with decadal uplift rates from 12 to 55 mm/yr (continuous GNSS, levelling or traverse measurements), yet with similar lithology and climate. The badlands are of calanchi type, with unvegetated slopes and sharp ridges, low relief (<50 m) and short basin length (<200 m). Topographic datasets include high-resolution (2.5 to 10 cm) UAV-derived Digital Surface Models (DSM) at all sites and a 1-m LiDAR Digital Earth Model (DEM) at one site. Drainage network, divides and geomorphic metrics (basin relief BR, hypsometric integral HI and hypsometric curve) were extracted using ArcGIS and Matlab TopoToolbox, for 12 to 27 basins over areas of 5000 to 34000 m2 from site to site.
At the fastest-uplift site, the 10-cm-resolution DSM and 1-m DEM lead to similar average BR (35 ± 7 m and 37 ± 7 m, respectively) and HI (0.49 ± 0.05 and 0.46 ± 0.05), although results for individual basins differ significantly for 20% of the 24 basins. Hence, even though crestlines and gullies are commonly narrower than 1 m, the 1-m LiDAR DEM mainly provides representative values for the investigated metrics. Results obtained from UAV DSMs at the three sites show no clear influence from decadal uplift or structural position. With increasing uplift of 12, 23, and 55 mm/yr, we respectively obtained average BR and HI of 27 ± 8 m and 0.50 ± 0.03, 23 ± 6 m and 0.48 ± 0.07, and 35 ± 7 m and 0.49 ± 0.05. Hypsometric curves fluctuate around a S shape at all sites, indicating a transitional stage with sustained uplift and erosion. A notable difference in the field is the thinner crestines and larger amount of clasts transiting along the hillslopes at the fastest-uplift site, indicating a larger production of clasts than run-off can transport. We interpret these results as erosion rates exceeding the already rapid uplift rates. This would be facilitated by the low erodibility of the mudstone formation. Indeed, a regional analysis based on a 20 m DEM shows that mean and maximum values of local slope and relief are lower in the mudstone domain than in siltstone and sandstone domains, in spite of active anticlines and larger decadal uplift being located in the mudstone domain. Ongoing complementary works on basin-wide denudation rates in several-km-long river basins draining the mudstone domains led to contrastingly low denudation rates of 0.8 mm/yr, indicating that badlands denudation either represents a different timescale or that other processes dominate denudation at the larger spatial scale.
How to cite: Le Béon, M., Ali, K., Siame, L., Chen, K.-F., Nguyen, N.-T., Leung, P.-H., Ching, K.-E., and Pathier, E.: Basin Relief and Hypsometry Indicate Rapid Erosion in the Badlands of the Active Fold-Thrust Belt of Southwestern Taiwan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15213, https://doi.org/10.5194/egusphere-egu26-15213, 2026.
The uplift of the Andes mountain range is widely recognized as a primary factor in shaping South America's climate patterns and transforming adjacent river landscapes. These changes have played a fundamental role in the dynamics of the rivers that drain the Amazon lowlands and shaping the physical landscapes and ecosystems over time. Here, we reconstruct the geomorphological and sedimentary evolution of the Huallaga River in central Peru. As part of the Amazon drainage system, the Huallaga River preserves a sedimentary record that allows us to disentangle the relative roles of tectonics and climate.
This study uses geomorphological mapping, sedimentological characterization, and feldspar post-infrared infrared-stimulated luminescence (pIRIR) dating to investigate the geomorphological and sedimentary evolution of the upper Huallaga River . Feldspar pIRIR at 225oC and at 290oC was applied to determine sediment deposition ages from river terraces and the Juanjui Fm. in the Juanjuí region, which is located on the eastern edge of the Peruvian Andes. The Huallaga River deposits are generally characterized by thick sedimentary layers (0 - 75 m) composed of conglomerates supported by a fine sand matrix and framework. The Pliocene-Pleistocene Juanjui Fm. consists of polymictic conglomerates with a sandy matrix. The conglomerate framework consists of gneiss, volcanic rock, schist, and sandstone pebbles that were reworked and deposited in a fluvial-alluvial fan environment. Geomorphological mapping indicates eight distinct terrace levels, named T1 to T8 from lower to higher elevation ranging from 3 to 142 meters above the riverbed. Feldspar pIRIR ages range from 100 to 300 thousand years ago (ka), but some sediment layers have similar ages, indicating a fill-cut deposit. The evolution of this region can be divided into four phases. The first phase is represented by the deposition of the Pliocene Juanjuí Fm. over the Miocene Ipururu Fm., indicating a period of high-energy aggradation. The second phase is characterized by the beginning of uplift of a syncline, promoted by the Biabo fault. This uplift caused erosion of part of the Juanjuí Fm. due to incision by the ancient Huallaga River. This was followed by the deposition of alluvial fans in the axial portion of the river system. The third phase is characterized by continued uplift, which promoted the erosion of the Pleistocene alluvial deposits (now, exposed in terrace levels) and the onset of a new phase of river incision. The last phase records the current configuration of the fill-cut terraces. These minimum ages are older than previously reported ages for the top of the Juanjuí Fm. in a nearby anticline. An integrated analysis of mapping, sedimentology, and chronology allowed the interpretation of river terrace deposition and incision phases, supporting future links with regional tectonic deformation. These results improve our understanding of recent dynamics along the eastern Andean margin and its role in shaping the Amazon basin. Funding provided by FAPESP (23/16031-4 and 22/03007-5).
Keywords: fluvial evolution, pIRIR dating, geomorphological mapping, Sub-Andean deposits
How to cite: Cruz, C., Souza, P., Viveen, W., Simoes, A., Campos, G., Breda, C., Brito, R., Souza, D., Sawakuchi, A., Bookhagen, B., and Pupim, F.: Fluvial response to Andean-Amazonian Transition Dynamics: evidence from Huallaga River terraces in central Peru, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17476, https://doi.org/10.5194/egusphere-egu26-17476, 2026.
Snow avalanches constitute a widespread and dynamic geomorphic process in the Carpathian Mountains, playing a key role in sediment and debris transfer on steep slopes within alpine and subalpine belts. The occurrence, magnitude, and frequency of snow-avalanche events are strongly controlled by climatic factors, particularly snowfall amount, snowpack structure, temperature fluctuations, and extreme weather conditions. In the context of ongoing climate variability, understanding the long-term relationship between climate drivers and avalanche activity is essential for improving hazard assessments in high-mountain regions.
In remote areas of the Carpathians, snow-avalanche hazard assessment is severely limited by the scarcity of systematic observations and the absence of long-term archival records of past avalanche events. This data gap is especially pronounced in the Eastern Carpathians, where documentary evidence of extreme snow avalanches is largely missing. At the same time, increasing human presence and recreational activities in high-mountain environments over recent decades have amplified exposure to avalanche hazards, highlighting the urgent need for reliable, long-term reconstructions of avalanche activity and climate-induced extremes.
This study aims to enhance the understanding of climate-driven snow-avalanche dynamics in the Eastern Carpathians through dendrochronological methods. Multiple avalanche paths located in different mountain ranges were investigated, targeting both coniferous and broadleaved tree species affected by past snow-avalanche activity. Trees disturbed by avalanches were sampled along selected paths, and growth anomalies caused by the mechanical impact and mass movement of snow were identified and precisely dated within annual growth rings. These disturbances include impact scars, tangential rows of traumatic resin ducts, compression wood, and growth-suppression sequences, which serve as reliable proxies for past snow-avalanche events.
By synchronizing avalanche signals recorded in tree-ring series and relating them to regional climatic patterns, this study reconstructs the spatial extent, frequency, and return periods of snow-avalanche events, with particular emphasis on extreme events likely associated with anomalous climatic conditions (e.g., winters with exceptional snowfall, or rapid temperature increases). The results provide insight into temporal variations in avalanche activity and allow the identification of climatically controlled periods of enhanced snow-avalanche occurrence. The dendrochronological reconstruction of climate-induced snow-avalanche activity offers a valuable long-term perspective on avalanche regimes in the Eastern Carpathians. These findings contribute to improved snow-avalanche hazard assessment and zonation and provide a robust framework for evaluating the potential impacts of future climate variability and change on avalanche dynamics at both local and regional scales.
How to cite: Pop, O.: Tree-ring reconstruction of climate-induced extreme snow-avalanche events in the Eastern Carpathians (Romania), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6368, https://doi.org/10.5194/egusphere-egu26-6368, 2026.
Fans formed by the accumulation of debris flows, rockfalls, and fluvial action are often found at the base of steep escarpments, which commonly border infrastructure corridors. Escarpments evolve at discordant rates, due to climate and tectonic gradients, and geologic heterogeneity. The variations influence watershed morphology, which in turn determines the dominant erosional processes and potential hazard along fans, such as rockfall, landsliding, avalanches, or flooding. Classically, erosional process regimes have been determined from simple morphometric indices, such as watershed length and the Melton Ratio (watershed relief divided by the square root of area; Wilford et al., 2004). Here, we propose a new framework that leverages high-resolution topography and its topographic derivatives along the steep Columbia River Gorge (CRG) escarpment (Oregon, USA) to classify erosional process regimes across 78 fans. Using fan slope, surface roughness, and drainage density, we map transitions from colluvial to debris-flow dominated fans. We show these topographic derivatives along fans can stand alone, providing the ability to distinguish upslope catchment processes without catchment morphology. This work serves as a framework for preliminary assessment of regional-scale process variability on fans, with applications ranging from hazard mitigation efforts to planetary geomorphology.
How to cite: Sanders, M. and Roering, J.: Linking fan surface morphology to erosional process regimes: A morphometric framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22128, https://doi.org/10.5194/egusphere-egu26-22128, 2026.
Escarpment landscapes represent prominent geomorphic boundaries that result from the long-term interaction of tectonic uplift, climate induced surface processes and lithological diversity over the one million timescales. However, quantifying the relative contribution of each factor remains challenging over such long periods. Process-based landscape evolution models provide these controls to be isolated and systematically tested under regulated conditions.
In this study, we use forward numerical landscape evolution simulations to investigate the sensitivity of escarpment evolution in the Swabian Alb
(southwestern Germany). We employ the Landlab modeling tools to simulate landscape transformations over approximately 1 Myr. Fluvial incision is
represented using a detachment-limited stream-power model, while hillslope sediment transport is depicted as diffusive smoothing. Spatially variable uplift is utilized to model long-term tectonic forces. Lithological heterogeneity is characterized by stratified layers exhibiting regionally diverse erodibility
coefficients, guided by channel steepness metrics that are commonly used to evaluate geographical discrepancies in river incision potential. Sensitivity studies examine different precipitation/runoff forcing scenarios to evaluate how climatic forcing changes erosion patterns compared with lithological controls.
Model results indicate that erosion and escarpment retreat are markedly concentrated along the Albtrauf escarpment facing tributaries of neckar and the primary river, but the core of the Swabian Alb plateau remains reasonably intact throughout the 1 million-year simulations. In the basic arrangement, high-erosion zones (≥P80) encompass a significant area of the escarpment domain but only a small section of the plateau. Sensitivity experiments indicate that variations in lithology significantly influence the magnitude and duration of erosion hotspots. They may improve hotspot coverage by up to as 10–12 percentage points relative to the basic model in some catchments however changes in uplift rate create very minor changes. Increasing precipitation significantly raises erosion level, however hardly influences the dimensions of hotspots. This indicates that climate mostly exacerbates erosion rather than altering its spatial distribution.
Reorganizing drainage by relocating divisions and trapping water locally
enhances incision concentration within existing channel networks. This results in
the gradual erosion of escarpments over an million timescale.
How to cite: Kumar, S., Glotzbach, C., Beer, A., and Peifer, D.: Sensitivity of Escarpment Evolution to Lithology and Climate Forcing: Forward Landscape Evolution Study from the Swabian Alb, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20653, https://doi.org/10.5194/egusphere-egu26-20653, 2026.
