Sediment transport water demand provides the critical theoretical foundation for effective watershed management, optimized reservoir operation, and sustaining river ecosystem health. This demand refers to the clear or sediment-laden water volume needed for transporting a specified amount of sediment to a downstream location within a given period, under defined flow-sediment and channel boundary conditions, while preserving a target erosion-deposition balance. This demand is governed by the sediment‑carrying capacity and channel‑forming processes of the river and is modulated by channel geometry, sediment supply dynamics, grain‑size distribution, target erosion‑deposition levels, and temporal scale. It manifests through multi‑factor coupling, spatiotemporal variability, scale dependency, and functional orientation. A range of methods have been developed to calculate this demand, including the definition method, the equilibrium sediment transport method, data‑based analysis, erosion‑deposition correction, energy balance, and non‑equilibrium sediment transport approaches. Drawing on case studies from the Ningxia-Inner Mongolia reach and the lower Yellow River, this paper examines the key characteristics of sediment transport water demand and compares the applicability of prevailing calculation methods.

How to cite: Le, M., Guo, C., and zhou, Z.: Water Demand for Sediment Transport in Rivers: Conceptualization and Computational Approaches, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21094, https://doi.org/10.5194/egusphere-egu26-21094, 2026.

Sediment-laden runoff in Ethiopia’s Upper Blue Nile Basin (UBNB) threatens the ecological health of Lake Tana and the operational efficiency of the Grand Ethiopian Renaissance Dam (GERD). Limited event-based sediment sampling hinders the accurate estimation of fluxes and process-based modeling in this data-scarce region. This study reconstructs continuous daily sedigraphs (1990–2020) for the Gilgel Abay (1,664 km²) and Gumara (1,394 km²) watersheds using machine-Learning (ML) methods, including Gradient Boosting (GB), Random Forest (RF), and Quantile Regression Forests (QRF), along with traditional techniques, using discharge, rainfall, temperature, and evapotranspiration as predictors.

QRF achieved the highest validation accuracy at the daily scale (R² = 0.62–0.72), capturing non‑linear sediment dynamics and providing uncertainty‑quantified yields (90% CI: 17.15–54.37 t/ha/yr for Gilgel Abay; 21.15–40.61 t/ha/yr for Gumara). Mean annual sediment yields were 27.5 ± 7.2 t/ha/yr (Gilgel Abay) and 23.8 ± 10.7 t/ha/yr (Gumara), with 93–95% of transport occurring during the monsoon season (June–October), emphasizing strong rainfall control.

The reconstructed records enabled the first successful calibration and validation of the WASA-SED model for coupled daily streamflow and suspended-sediment dynamics in the Ethiopian Highlands. Monthly simulations showed strong performance (NSE 0.66–0.86; R² 0.72–0.87). Flow- and sediment-duration curves indicated excellent skill during high-flow events, which dominate sediment export, with underestimation in mid- and low-sediment ranges.

Decadal analyses revealed contrasting watershed trajectories. In Gilgel Abay, rainfall intensified (from 136.9 mm/month in the 1990s to 208 mm/month in the 2020s), streamflow increased by 78% (55 to 98 m³/s), and sediment loads peaked mid‑period before declining. In Gumara, rainfall remained stable, but streamflow rose 54% (35 to 54 m³/s), and sediment loads increased 61% (8.2 to 13.2 × 10³ t/day), influenced by wetland loss (−63%) and rapid urban expansion.

This integrated ML–process modelling framework bridges sediment data gaps, advances hydro-sediment process understanding, and supports targeted erosion mitigation for the sustainable management of the UBNB. The approach is transferable to other humid tropical basins facing similar data limitations.

Keywords: sediment reconstruction, QRF, WASA‑SED, decadal trends, Upper Blue Nile, humid tropics, data‑scarce modelling

How to cite: B.Worku, K., A. Zimale, F., Francke, T., Zargar, M., and Bronstert, A.: Suspended Sediment Fluxes and Decadal Trends in the Humid Tropics: Machine Learning Reconstruction and Coupled Modelling in Upper Blue Nile Tributaries, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4157, https://doi.org/10.5194/egusphere-egu26-4157, 2026.

The occurrence and magnitude of debris flows largely depend on the amount of sediment stored within a catchment and the effectiveness of its connection to the channel network. Quantifying both sediment availability and its connectivity is therefore a critical requirement for constraining numerical simulations used to delineate debris-flow inundation areas. To support more reliable hazard assessments in alpine regions, an integrated geomorphological framework was developed and implemented in the Camonica Valley (Italian Alps) to characterise potential debris flow behaviour. The approach places particular emphasis on sediment connectivity as a key link between sediment sources and downstream propagation, reinforcing the role of geomorphological and geomorphometric analyses as a foundation for numerical modelling. Field observations, historical records of past events, and morphometric indicators are jointly used to discriminate between dominant flow processes and to estimate the volumes of sediment that may be mobilised during extreme events. The workflow combines GIS-based regional screening of debris-flow susceptibility along the drainage network with the identification of sediment source areas derived from orthophotos and terrain analysis, followed by an explicit evaluation of sediment connectivity and field-based verification of sediment thickness. Overall, the methodology provides a coherent and transferable basis for debris-flow hazard zonation and land-use planning in mountain environments, with sediment connectivity explicitly embedded in the assessment process.

How to cite: Cavalli, M., Crema, S., Rocca, J., Ballaera, A., Barizza, A., Gaigher, G., Ioriatti, E., Marchi, L., Piantini, M., Sarretta, A., Agostini, M., Bianchi, F., Martinengo, M., and Simonelli, T.: Sediment availability and connectivity: a geomorphological framework for debris-flow hazard assessment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20802, https://doi.org/10.5194/egusphere-egu26-20802, 2026.

In engineering practice, the export of sediment loads during so-called “torrent events”, i.e. fluvial events or debris-flow events in steep headwater catchment, is of interest for short-term hazard assessment and longer-term sediment management in alpine regions. Several empirical models already exist for this purpose, each with varying degrees of complexity and uncertainty. In this study, a total of 3,642 torrent events in Austria, where information on the associated sediment load is available, were analyzed and related to geomorphological, geological, and hydro-meteorological boundary conditions. Despite of substantial scatter, we find that the type of event – fluvial flows or debris flows – as well as geology and geomorphology have the strongest control on sediment loads, while, interestingly, triggering precipitation show only limited correlations. Based on these results, we derive simple empirical equations to provide a data-driven assessment tool to estimate value ranges for future event sediment loads in torrent catchments in the Austrian Alps.

How to cite: Kaitna, R., Ender, M., Nagl, G., Moser, M., and Kammerlander, J.: Event-based sediment loads from Austrian torrent catchments related to process and catchment characteristics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17224, https://doi.org/10.5194/egusphere-egu26-17224, 2026.

Soil erosion and sediment redistribution in Mediterranean agroforestry landscapes are strongly influenced by land use and substrate variability, affecting sediment delivery to downstream sinks. Identifying the relative contributions of hillslope sediment sources to depositional environments is essential for understanding sediment transfer processes and source–sink connectivity. In this study, sediment fingerprinting techniques were applied to quantify hillslope sediment contributions recorded in a lake shore sediment core within the endorheic Estaña catchment (NE Spain). The closed hydrological setting and the presence of a lake acting as a natural sediment trap provide favourable conditions for tracing sediment provenance from adjacent slopes. A sediment core collected at the lower part of the hillslope in a lake shore, was analysed and compared with potential sediment sources representing different land uses and lithological units. Potential source materials and sediment core samples, analysed as a sequence of 5 cm depth intervals from the surface to depth, were characterised using a suite of geochemical elements (Mg, K, Na, Pb, Ba, Zn, Sr, Li, Mn, Co, Ni, Cu, Cr, Fe, Al and Ca) and fallout radionuclides (¹³⁷Cs and excess ²¹⁰Pb). The unmixing model FingerPro 2.0 was used to identify and estimate the relative contributions of the potential sources to the lake shore sediment core, allowing uncertainty to be explicitly assessed. Preliminary results reveal marked spatial variability in sediment source contributions linked to land use and lithology on the contributing hillslope, demonstrating the potential of combining geochemical and fallout radionuclide tracers to improve the robustness of sediment fingerprinting in small Mediterranean catchments. This approach provides valuable insights into hillslope to lake shore sediment connectivity and contributes to a better understanding of sediment source dynamics and temporal shifts in dominant sediment sources under changing environmental conditions.

How to cite: Gaspar, L., Latorre, B., and Navas, A.: Tracing hillslope sediment contributions to a lake shore using geochemical and fallout radionuclide fingerprints, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21024, https://doi.org/10.5194/egusphere-egu26-21024, 2026.

Understanding sediment provenance is crucial for reconstructing past environmental conditions and deciphering erosion patterns in rapidly evolving mountain belts such as the Himalaya. The Yarlung–Tsangpo–Brahmaputra system, one of the world’s most dynamic sediment-routing networks, provides a key setting to examine how extreme hydrological events mobilize material from distinct source terranes. In this study, we analyse five well-dated paleoflood deposits from the Siang River using an integrated suite of provenance tools—sand petrography, U–Pb zircon geochronology, and Sr–Nd isotope geochemistry—to evaluate their relative strengths and interpretive limitations.

Petrographic data show quartz–feldspar-rich compositions and heavy-mineral assemblages pointing to contributions from the Higher Himalayan Crystallines (HHC) and Tethyan Sedimentary Sequence (TSS), although long-distance transport, weathering, and hydraulic sorting obscure lithologic specificity. Zircon age spectra reveal diverse age populations sourced from the Namche Barwa syntaxis, Tibetan Plateau, and Lhasa Terrane; however, zircon recycling and overlapping age groups introduce ambiguity in resolving discrete source areas. Sr–Nd isotopic signatures provide a more integrated and transport-insensitive signal, indicating dominant TSS influence with enhanced erosion of the Namche Barwa region during high-magnitude flood events. Together, these proxies demonstrate that each method captures a different scale of sediment input—petrography reflecting local lithologic contributions, zircon ages tracing distal and recycled sources, and Sr–Nd isotopes integrating basin-scale signatures. The multi-proxy approach underscores the need to combine complementary datasets to accurately reconstruct sediment routing, identify erosional hotspots, and comprehend megaflood-driven landscape evolution in the eastern Himalayas.

How to cite: Panda, S., Kumar, A., Singhal, S., and Srivastava, P.: Tracing Sediment Pathways in the Siang Basin: A Multi-Proxy Provenance Approach Using Petrography, Zircon Geochronology, and Sr–Nd Isotopes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-797, https://doi.org/10.5194/egusphere-egu26-797, 2026.

The 2025 "State of Food and Agriculture" (SOFA) report published by the Food and Agriculture Organization of the United Nations (FAO) reiterates the significant threat posed by soil erosion and land degradation to agricultural productivity, food security, and the resilience of ecosystems. The FAO estimates that around 1.7 billion individuals globally reside in regions facing yield gaps associated with human-induced land degradation (FAO, 2025).

Numerous scientists across the globe, including our research team in Basel, have utilized and assessed d13C compound-specific stable isotopes (CSSI) derived from long-chain fatty acids across various land uses as tracers. This methodology has been employed to monitor and identify erosion stemming from different land uses to river or lake sediments (Alewell et al., 2016; Upadhayay et al., 2022), as well as to depositional sites (Mabit et al., 2018), and to investigate land use changes within soil chronosequences (Swales and Gibbs, 2020). This analytical tool can act as a significant asset for global decision-makers, aiding in the protection of soil and water resources both in a general context and in relation to specific United Nations Sustainable Development Goals (SDGs): 2 – Zero Hunger, 6 – Clean Water and Sanitation, 12 – Responsible Consumption and Production, 13 – Climate Action, 14 – Life Below Water, and 15 – Life On Land.

We present data of isotopes collected over several years from different land use in various regions including Europe (Switzerland, France, England, Scotland), South Korea, and Brazil. The isotopic values transition from being more depleted in temperate Europe to more enriched in the semi-humid Brazilian savannah, with South Korea exhibiting intermediate values. Furthermore, additional data from over 40 internationally published studies have been compiled to enhance our findings.

This is the first presentation of such a data collection, which can be continuously updated with the latest research findings, functioning as both an archive and a foundational data resource for sediment source attribution to ascertain the origins and potential causes of soil erosion. Additionally, a CSSI land use database encompassing numerous regions globally could significantly lessen the burden of costly and labor-intensive source soil sampling, particularly when time and resources are constrained.

References:

Alewell, C., Birkholz, A., Meusburger, K., Schindler Wildhaber, Y., and Mabit, L.: Quantitative sediment source attribution with compound-specific isotope analysis in a C3 plant-dominated catchment (central Switzerland), Biogeosciences, 13, 1587–1596, https://doi.org/10.5194/bg-13-1587-2016, 2016.

FAO. 2025. The State of Food and Agriculture 2025 – Addressing land degradation across landholding scales. Rome.

Mabit, L., Gibbs, M., Mbaye, M., Meusburger, K., Toloza, A., Resch, C., Klik, A., Swales, A., Alewell, C.,: Novel application of Compound Specific Stable Isotope (CSSI) techniques to investigate on-site sediment origins across arable fields, Geoderma, Volume 316, 2018.

Swales, A. & Gibbs, M.: Transition in the isotopic signatures of fatty-acid soil biomarkers under changing land use: Insights from a multi-decadal chronosequence, Science of The Total Environment, Volume 722, 2020.

Upadhayay, H.R., Granger, S.J. & Collins, A.L. Comparison of sediment biomarker signatures generated using time-integrated and discrete suspended sediment samples.Environ Sci Pollut Res 31, 22431–22440 (2024). 

How to cite: Birkholz, A., Evrard, O., Foucher, A., Glendell, M., Park, J.-H., Ramon, R., Salvador-Blanes, S., Tiecher, T., and Alewell, C.: Global assessment of CSSI land use fingerprints of long-chain fatty acids in soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10161, https://doi.org/10.5194/egusphere-egu26-10161, 2026.

Following the Fukushima nuclear accident in March 2011, significant deposition of radiocesium, including ¹³⁴Cs and ¹³⁷Cs, occurred across vast regions of Northeastern Japan, in the Tohoku Region. However, as most studies have focused on fallout in the Fukushima Prefecture, there is much less information available on the situation in other parts of the Tohoku region of Japan further north. Against this backdrop, the present study examined the presence of fallout radionuclides (including the natural radionuclide ²¹⁰Pb and the artificial radionuclides ¹³⁴Cs and ¹³⁷Cs) in both burned and unburned soil profiles, as well as in various surface soil and sediment samples collected in the Kamaishi region (Iwate Prefecture, Tohoku Region, Japan), which was affected by extensive wildfires in 2017.  The results show that ²¹⁰Pb and ¹³⁷Cs can be used to trace sediment sources in landscapes affected by wildfires in this region. Furthermore, analysis of the soil profiles demonstrated that all analysed fallout radionuclides were enriched in the burned versus unburned profiles due to radionuclides being trapped by vegetation and incorporated into the ash after the fire. Detecting ¹³⁴Cs in the uppermost 0–5 cm layer of all soil profiles investigated also demonstrated significant Fukushima fallout of ¹³⁴Cs and ¹³⁷Cs in this region, roughly equivalent to the fallout associated with nuclear atmospheric tests in the 1960s. In future, both sources of fallout should be considered when interpreting radionuclide data found in environmental samples collected in vast regions of north-eastern Japan. Analysis of ¹³⁴Cs should also be encouraged in order to document fallout sources in these regions for as long as this short-lived radionuclide remains detectable (i.e. until around 2031).

How to cite: Evrard, O., Takahashi, N., Chalaux-Clergue, T., Foucher, A., and Chaboche, P.-A.: Potential use of fallout radionuclides as tracers of environmental processes after wildfires in Tohoku Region, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1774, https://doi.org/10.5194/egusphere-egu26-1774, 2026.

A considerable number of geochemical and granulometric datasets from various sediment sequences was gathered during the recent decades in the context of palaeoenvironmental and palaeoclimate reconstructions, assessment of human impacts on earth surface processes, and provenance tracing in fluvial environments. Although the large importance of grain-size control on sediment geochemistry has been known for many years and was explicitly declared in some review papers on geochemical provenance tracing, it still forms a challenge for current research. The problem is that provenance, grain-size, and weathering (post-depositional alterations) jointly control the resulting chemical composition of paleosol-loess sequences or floodplain deposits, and need hence to be distinguished from each other. However, in several recent studies data processing was simplified and the results were presented in an unequivocal manner, although interpretation of sediment composition is always rather equivocal. This was especially the case when geochemical datasets were subjected to automated data processing by software routines, instead of an expert-based examination of the individual datasets and a correct qualitative distinguishing of the individual controlling factors.

Data assessment should always start from understanding the major geochemical and sedimentological factors and processes behind data variability. This phase cannot be automated, and should mandatorily precede the selection of appropriate data processing routines. On the one hand geochemical compositions may be mainly controlled by varying percentages of ‘diluting’ components such as quartz (usually sand) or (detritic or autochthonous) carbonate, that can be corrected for by rationally chosen element ratios. Numerous complex mathematical approaches have been designed to address that issue, however, they do not always produce interpretable results and therefore need empirical (expert-based) verification. One the other hand, ‘dilution’ effects can interfere with grain-size control, that can be revealed by scatterplots of element ratios or the visualisation of element ratios and grain size classes. Furthermore, the recently established Bayes space methodology for modelling and analysing continuous distributive data can visualise the grain size control of element ratios for entire granulometric curves. Combined with regression modelling this allows statistically sound conclusions about grain size effects on the element ratios desired for interpretation. For example, varying grain-size preferences of feldspars or zircons can point to distinct source rocks and thus qualitatively reveal provenance changes. Provenance changes can only be quantified after deciphering and considering ‘dilution’ and grain-size effects, and only if the sediment sources have really distinct geochemistry. The provenance tracing cannot be automated or based only on the formal performance of statistical tools such as low values of RMSE.

Concluding, provenance tracing should be based on geochemically interpretable element concentration ratios after cross-checking for ‘dilution’ and grain-size control, best done ‘manually’ by assessing a series of (old-fashioned) scatterplots, preferably with the granulometry information implemented using the Bayes space methodology. To obtain sound conclusions it is also essential to phrase clear and testable research questions before any research, acquire suitable data really representing variability in studied sediment sequences and potential provenance areas, and use statistical methods respecting real data complexity.

How to cite: Matys Grygar, T., von Suchodoletz, H., Pavlů, I., and Zeeden, C.: Deciphering dilution, grain size, and provenance in sediment geochemistry, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3575, https://doi.org/10.5194/egusphere-egu26-3575, 2026.

Since the mid-20th century, agricultural intensification and expansion have profoundly altered sediment fluxes from cultivated landscapes to freshwater systems. However, the long-term (>70 years) regional and global imprint of these changes remains poorly quantified. Here, we present a global synthesis of sediment accumulation records from 812 lakes and reservoirs draining agricultural catchments affected by land use worldwide.

By compiling sediment accumulation rates (SAR), mass accumulation rates (MAR) and associated geochemical proxies constrained by robust age–depth models, we reconstruct multi-decadal sediment flux trajectories from 1900 to 2010 at global and regional scales, and compared them with global land use statistics. These trajectories provide an integrated proxy for long-term land degradation. Our results reveal a pronounced and sustained post-1950 increase in sediment fluxes, with global MAR and SAR rising by approximately 500% and 350%, respectively. This acceleration is observed across all regions of the world, although its timing and relationship with land-use change differ markedly. In Europe and North America, sediment fluxes increased earlier (1950s–1960s; ≈140%) despite declining agricultural land area, suggesting an anticorrelation with land extent but a strong link to the intensification of agricultural practices. In contrast, Africa, Asia and Latin America exhibited later accelerations (1980s–2000s) that are positively correlated with the agricultural expansion.

Together, these findings demonstrate that lakes and reservoirs in agricultural regions worldwide record a coherent sedimentary response to post-1950 agricultural changes, while highlighting regional contrasts in the mechanisms linking land use, land management and sediment delivery. This synthesis provides a long-term reference for evaluating the impact of agricultural intensification on soil degradation and freshwater systems during the Anthropocene.

How to cite: Foucher, A., Evrard, O., Cerdan, O., and Salvador-Blanes, S.: Global acceleration of sediment fluxes under post-1950 agricultural intensification, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12086, https://doi.org/10.5194/egusphere-egu26-12086, 2026.

In the context of river ecological restoration in Europe and in order to achieve a “good” ecological and chemical status in watercourses, it is essential to quantify the volumes of contaminated sediment accumulated in fluvial annexes, which may be remobilized during floods or human interventions. These assessments not only allow the evaluation of ecotoxicological risks, but also help to assess the ecological functions associated with reconnection to the main channel. The Saône River (France), the main tributary of the Rhône River in terms of hydro-sedimentary contributions, has been little studied from this perspective, despite numerous developments (dykes) that have profoundly altered the lateral connectivity of its main channel. A more in-depth knowledge of the Saône River is therefore clearly needed  to guide effective and safe ecological restoration actions.

The volumes of sediments accumulated in three fluvial annexes distributed along the Saône River were estimated by combining ground-penetrating radar (GPR) transects with sediment cores sampling. These sediment archives were characterized (grain-size, organic matter content, trace metal content) to reconstruct the temporal trends of metal accumulation, based on ¹³⁷Cs and ²¹⁰Pb dating. Depending on the site, these sediment sequences provide six to eight decades of records, extending back to the 1940s for the longest. These data allow quantification of contaminants stocks (trace metals) and estimation of the annual load of contaminated suspended matters by the river in each site.

The study sites exhibit contrasting morphologies and varying levels of lateral connectivity with the main channel. These differences influence the sediment storage volumes within the fluvial annexes, ranging from 8,000 m³ to 100,000 m³. These results reveal metal enrichment since the 1940s, with a clear and well-documented increase in Cd, Cu, Pb and Zn during the post‑World War II economic expansion (1950s), reaching maximum concentrations during the 1970s. Their concentrations subsequently declined in the 1990-2000s before stabilizing at lower plateau values.

A specific feature concerns the contamination history of Ag, most likely driven by the photographic industry, which presented a three-phase pattern: (i) regular increase in the 1970s and 1980s, (ii) successive peaks between 1986 and 1994, and (iii) a marked decline in the late 1990s-2000s, with the decline of silver. This typical signal was observed at all studied sites along the river, despite hydrological connectivity differences. These sedimentary record complement monitoring data, especially for trace metals that were difficult to quantify in the past. This study highlights the major influence of historical contamination sources that released polluted sediments at the basin scale over several decades. This reconstruction also has national-scale implications and complements records obtained by other research works (such as on the Seine or Garonne rivers), highlighting the extent and persistence of pollution linked with photographic product manufacturing in Western Europe before 2000. Together, these results provide an integrated understanding of sediment dynamics and contamination, offering key insights for future river management and restoration strategies.

How to cite: Écorse, A., Dendievel, A.-M., Mourier, B., Coynel, A., Dhivert, É., Paran, F., Peuble, S., Winiarski, T., and Bedell, J.-P.: Which benefits of fluvial annex sediment analysis for quantifying and tracing industrial pollution along the Saône River? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2798, https://doi.org/10.5194/egusphere-egu26-2798, 2026.

In alpine torrents, the transport of large wood plays a significant role in the development of multi-hazard chains, while also contributing to channel complexity, sediment regulation, and the ecological functioning of mountain stream ecosystems, its mobilization during extreme events increases the risk of damage for infrastructures. The interaction between large wood, sediment and infrastructure such as engineering structures can lead to hazards, due to the formation of wood jams, related backwater effects, overtopping and unexpected morphological changes. Therefore, understanding the transport dynamics of large wood is fundamental for the design of resilient torrent control measures.

The Rindbach catchment in Ebensee close to the Traunsee (Austria) serves as a representative case study area for these processes. This torrent has a history of high wood recruitment driven by deforestation and avalanches such as the Häuseleckgraben avalanche in 2009 which delivered about 1,000 m³ of wood into the channel. A wood retention rack was built as part of a project by the Austrian Service for Torrent and Avalanche Control (WLV), after the flood event in 2013 that demonstrated the vulnerability of local settlements to wood-laden floods.

To analyze the potential formation of wood jams at the retention structure, the 2D numerical model IberWood is used. The methodology focuses on the interaction between channel morphology, hydraulic flow conditions and the variable transport pattern of large wood. To analyze the systematic response of the torrent to varying wood loads, historical high-flow conditions like the event in 2013 are used as a reference framework. The focus lies on identifying the amount of wood needed to clog the retention structure and affect its discharge capacity. The aims of this study are to provide valuable insights into the optimization of technical wood retention in torrential catchments and to contribute to the development of more resilient hazard mitigation measures in the Alps.

How to cite: Kienesberger, S., Schalko, I., Ruiz-Villaneva, V., and Scheidl, C.: Evaluation of Large Wood Accumulation Processes at a Retention Structure in the Rindbach Alpine Torrent (Austria): A Numerical Study, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10772, https://doi.org/10.5194/egusphere-egu26-10772, 2026.

Geo-hydrological risk mitigation exceeds administrative borders and needs shared and coordinated actions to address climate change effects across borders. In vulnerable areas, such as North-Eastern Italy and Slovenia where torrents and rivers cross national boundaries, joint strategies are essential to improve watershed management, infrastructure safety, and human protection. This requires integrating diverse expertise through cooperation among cross-border authorities, stakeholders, and researchers to develop a shared management solution and a response to common challenges. Torrent control works have been strategically used for several decades to regulate sediment dynamics in mountain catchments, but few research studied how structures interact with erosion and deposition processes. Nowadays, multi-temporal High-Resolution Topography (HRT) and GIS technologies enable efficient analysis of sediment dynamics in fluvial systems and their evolving interactions with watershed control structures. To improve watershed management and prioritise maintenance, the Interreg ITA-SLO “TORRENT” project aims to define shared international standards for monitoring torrent control systems and evaluating their long-term performance. The results highlight how a shared database complemented by common tools such as the Maintenance Priority Index, advanced technology and standardised data collection protocols, strengthens watershed management challenges in Slovenia and Italy and provides a transferable strategic approach for other basins in neighbouring countries.

Acknowledgments

The TORRENT project is co-funded by the European Union under the Interreg VI-A Italy-Slovenia Programme.

How to cite: Cazorzi, F., Žvokelj, L., Zupanc, V., Bezak, N., Fabbro, M., Clerbois, A., Ziraldo, A., di Bernardo, F., Maset, E., Beinat, A., Arnone, E., Poli, M. E., Orlando, C., and Cucchiaro, S.: Joint practices to support the torrent control structures management in geo-hydrological risk mitigation across borders, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5762, https://doi.org/10.5194/egusphere-egu26-5762, 2026.

Check dams are widely implemented in Alpine torrents to mitigate natural hazards and regulate sediment fluxes, yet their influence on sediment transfer and connectivity remains poorly constrained. In particular, it is still unclear how a series of check dams can modify sediment connectivity, specifically the erosion, and deposition patterns along the sediment cascade. We address this gap in the 12 km² Gürbe catchment at the northern margin of the Swiss Alps, where a steep, geomorphologically active channel reach has been engineered by approximately 100 check dams. The Gürbe torrent originates in low-erodibility Mesozoic limestones and transitions downstream into highly erodible Flysch, Molasse, and glacial till. A glacially conditioned knickzone at ~1200 m a.s.l. marks the onset of strong channel incision and enhanced hillslope–channel coupling (Schmidt et al. 2026). Downstream of this knickzone, the channel steepens by about 3°, traverses a landslide-prone corridor, and finally reaches the alluvial fan, forming a reach that is almost entirely controlled by check-dam structures.

We investigated the impact of check dams on bedload transport using repeated uncrewed aerial vehicle (UAV) - based photogrammetric surveys, which allowed us to quantify volumetric changes of the channel bed and to track erosion and deposition patterns through time (seasonal to annual and decadal). Our results show that bedload transport within the engineered reach is highly discontinuous, particularly during frequent low- to moderate-magnitude flow events. Check dams interrupt sediment continuity and create a succession of closely spaced erosion and deposition zones, leading to pronounced spatial variability in sediment dynamics over short distances. Even during moderate floods, gravel-bar re-working differs markedly between adjacent dam sections. Sediment inputs strongly control these dynamics. Material delivered from upstream is repeatedly reworked as it passes through successive check-dam compartments, alternating between reaches dominated by deposition and by erosion. In contrast, lateral sediment inputs, especially from landslides, promote net deposition and progressive accumulation of stored bedload material that is only mobilized during larger, less frequent flood events. Further downstream segments with lateral input of sediment derived from tributaries as well as non-regulated channel reaches are characterized by enhanced sedimentary dynamics, leading to abundant channel reorganization.

Overall, the check-dam system exhibits a tendency toward net deposition and sediment storage on decadal timescales, with dams acting as temporary buffers that trap bedload. These accumulated sediments form a latent sediment stock that is episodically released during major events, when channel erosion intensifies and stored material is excavated and transferred downstream. Our findings demonstrate that check dams fundamentally shift bedload transport from a relatively continuous process toward a pulsed, event-driven regime characterized by persistent reworking, long-term accumulation, and episodic phases of intensified erosion and transport.

Schmidt, C., Mair, D., Akçar, N., Christl, M., Haghipour, N., Vockenhuber, C., Gautschi, P., McArdell, B., and Schlunegger, F.: Quantifying erosion in a pre-Alpine catchment at high resolution with concentrations of cosmogenic ¹⁰Be, ²⁶Al, and ¹⁴C, Earth Surf. Dynam., 14, 33–53, https://doi.org/10.5194/esurf-14-33-2026, 2026.

How to cite: Schmidt, C., Mair, D., McArdell, B., and Schlunegger, F.: Disrupted Connectivity: The Impact of Check Dams on Bedload Transport and Sediment Storage in the Gürbe Catchment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13048, https://doi.org/10.5194/egusphere-egu26-13048, 2026.

Slit dams, a common type of check dam, are engineered to retain coarse sediment while allowing finer particles to pass through. During the interception of granular flows, a separation of water and sediment typically occurs, beginning with the initial impact and continuing through subsequent deposition stages. To fundamentally understand the mechanisms by which slit dams separate solid-liquid mixtures, it is essential to first isolate and examine the hydrodynamic impact of water on the dam structure in detail.

In the design of slit dams, the width of the slits between piers and the dam height are critical parameters. To investigate the effect of different slit widths, experiments were conducted in a rectangular transparent flume with a length of 1.58 m set at a fixed slope of 15°. Three slit configurations, labeled A4, A5, and A6 (representing arrangements with 4, 5, and 6 piers respectively), were tested in the flume. During the experiments, miniature pressure sensors were used to sample pressure fluctuations, and a high-speed camera operating at 400 fps was employed to capture the flow behavior. This setup allowed the detailed process of flow impacting the slit dams to be fully recorded for statistical analysis. The results indicate that the impact process can be divided into three stages: turbulent, stable, and decay. The maximum average impact force and overflow depth showed no significant difference across the different slit widths. The hydrograph for the A5 configuration, which exhibited high turbulence, demonstrated a longer duration and slower pressure decay, followed by A6 and then A4.

How to cite: Fan, J., Chen, J.-C., and Li, F.: Experimental Investigation of Water-Flow Impact on Slit Dams with Varying Slit Widths, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18921, https://doi.org/10.5194/egusphere-egu26-18921, 2026.

Mediterranean agricultural landscapes face significant challenges from soil degradation and erosion processes that compromise both productive capacity and downstream water resources, creating an urgent need for implementing sustainable conservation strategies through Nature-Based Solutions (NBSs). This research employed the InVEST Sediment Delivery Ratio (SDR) modeling framework to examine erosional dynamics and quantify the potential benefits of various NBS interventions within the 506 km² Carapelle catchment. Model calibration and validation procedures utilized empirical sediment yield observations from the 2007-2008 monitoring period, achieving optimal parameter adjustment with only 4.3% variance from field measurements. A 20-year measured weather data were used to run the InVEST SDR model. The investigation examined four distinct NBS implementation strategies: contour-based cultivation techniques (CF), conservation tillage practices (NT), vegetative cover establishment (CCs), and integrated management approaches (Comb). Annual soil displacement rates under baseline conditions ranged between 2.43 and 3.88 t ha⁻¹ yr⁻¹ across the study years, with corresponding downstream sediment delivery of 0.86-1.30 t ha⁻¹ yr⁻¹. Conservation tillage emerged as the most effective single intervention, achieving an average 72.2% reduction in sediment transport. The integrated strategy combining conservation tillage with cover crop establishment delivered optimal results, yielding 75.9% and 70.5% reductions in sediment export and soil displacement, respectively. Geospatial evaluation demonstrated that forested and shrubland areas exhibited the highest natural retention capacity, while cultivated landscapes presented the greatest opportunities for NBSs deployment. The findings confirm that NBSs substantially improve sediment retention ecosystem services within Mediterranean agricultural watersheds. The InVEST SDR modeling approach demonstrates robust capabilities for catchment-scale erosion assessment. These outcomes offer practical insights for developing evidence-based land stewardship policies and conservation strategies in erosion-vulnerable Mediterranean regions.

How to cite: Abdelwahab, O. M. M., Ricci, G. F., Netti, A. M., Fiore, A., Mohammedi, S., De Girolamo, A. M., and Gentile, F.: Assessing Erosion Mitigation Effectiveness of Nature-Based Solutions Using InVEST® SDR Modeling: Application to the Carapelle Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20411, https://doi.org/10.5194/egusphere-egu26-20411, 2026.