Changes of discharge (Q) and sediment yield (SSY) during flood events provide critical insights for flood disaster prevention and control. However, our understanding of the long-term variations and driving factors of Q-SSY relationships during flood events remains limited. This study examined the variations in Q, SSY and sediment rating curves (SSY = aQ^b) during maximum flood events (one, three, and five) across fifteen catchments in the China’s Loess Plateau during 1956-2019. The partial least squares-structural equation modeling (PLS-SEM) was used to quantitatively decouple the effects of driving factors (precipitation, soil, vegetation, topography, and soil and water conservation measures (SWCMs)). There was a significant declining trend in both Q and SSY during flood events across catchments, but the contribution of these events to annual SSY significantly increased by 41.48% during 1956-2019, underscoring the critical role of floods in sediment transport. The Q-SSY relationship during flood events weakened over time, with coefficient a decreased and index b increased. In addition, 44 - 49% and 36 - 51% of the changes in a and b can be attributed to the comprehensive effects of the five factors, respectively. The direct effects of vegetation (-0.921) and precipitation (0.616) on coefficient a were significant. Index b was principally dominated by SWCMs and vegetation, and the effects diminished from one to five flood events. These findings highlight the importance of increased vegetation cover and effective SWCMs in mitigating sediment transportation processes, and informs the development of tailored sediment management strategies for the Loess Plateau and similar regions.

How to cite: Gao, G.: Quantitatively decoupling the relationships between discharge and sediment yield during flood events in China's Loess Plateau, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19415, https://doi.org/10.5194/egusphere-egu25-19415, 2025.

Fine sediment transported in suspension is an important part of the total sediment yield in most rivers with erodible upland sediment sources. Fine sediment has positive effects on the stabilization of riverbanks, the accretion of floodplains, nutrient transport, and carbon sequestration. However, when fine sediment load is excessive, it can also clog the streambed, reduce invertebrate and fish habitat, prevent river-aquifer exchange and hyporheic flows, and damage hydropower infrastructure.

 To effectively design sediment management policies in rivers, it is fundamental to understand the fine sediment dynamics at the catchment scale. This study focuses on the washload, the fine sediment fraction that, once entrained, remains in suspension until its deposition.

Washload dynamics are typically quantified by concurrently measuring stage or discharge (Q) and turbidity, from which suspended sediment concentration (SSC) is derived. Q-SSC pairs often create a hysteretic relationship, allowing us to infer the distance of fine sediment sources upstream of the station.

This contribution adopts a reach-scale perspective on Q-SSC analysis, moving beyond single-station hysteresis loops and leveraging Q-SSC data from two stations, one upstream and one downstream. The core idea is that we can study washload as a passive tracer to gain further information about the hydraulic variables of roughness and water velocity, for each event separately. We can then integrate this information to further describe the fine sediment sources dynamics and the washload regime of the studied reach. Combining the subsequent reach-scale information we can completely reconstruct the washload production timing and yields across the whole catchment.

For this purpose, we developed new tools which ought to become the new standard for Q-SSC analysis. First, we identify in the discharge timeseries the flood and sediment pulse events through a new algorithm based on Empirical Mode Decomposition. Second, we study the virtual velocity of the flood and sediment signal by a new definition of cross correlation, analysing the Hilber transforms of the signal. Third, we study the presence and the nature (e.g. intensity and seasonality) of suspended sediment sources and tributaries through a time dependant boundary condition analytical solution of the advection-diffusion equation, both for discharge and washload concentration.

 The development of these three new tools and their application to the Arc-Isere (France) with six stations and four reaches, allowed us to identify the fine sediment sources and sinks in the river network. We also gained insights into seasonal fine sediment yields, the deposition and re-suspension dynamics of riverbed sediment stocks, and their progressive depletion during the spring-summer season. These methods are generalizable and applicable wherever discharge (Q) or stage and SSC data are available at two or more locations.

How to cite: Agostini, L. and Molnar, P.: New methods for the identification of fine sediment sources: from the discharge-turbidity relation to a reach scale understanding, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8969, https://doi.org/10.5194/egusphere-egu25-8969, 2025.

Understanding soil erosion history in ecologically fragile karst regions is essential for sustainable land management. The potential use of border polje (BP) soil profiles as reliable records of erosion deposition remains uncertain. This study investigated the geochemical characteristics of limestone and siltstone weathering profiles on both sides of the BP, using geochemical fingerprints to quantify BP soil source proportions and erosion changes. Key findings include (1) The karst and non-karst soil profiles on the slopes on each side of BP exhibit distinct geochemical signatures, with weathering indices indicating chemical weathering processes originating from limestone and siltstone, respectively. (2) Discriminant analysis and conservative element testing achieved accurate differentiation between the limestone and siltstone weathered soil sources, with a model goodness-of-fit above 80%, confirming the effectiveness of geochemical fingerprinting for determining soil provenance. (3) Siltstone-weathered soils dominate the bulk of BP soils, with small amounts of weathering products from limestone near the karst hills. (4) A marked increase in weathered material from both karst and non-karst sources at depths of 1.2–1.4 m, along with charcoal presence, suggests intensified erosion following historical fire events in the area. These results affirm the feasibility of the use of BP soil profiles as records of historical erosion, with geochemical fingerprints capturing shifts between karst and non-karst hill contributions. This study highlights the potential of BP soil profiles as archives of environmental changes, providing a framework for reconstructing historical landscape dynamics in complex terrains.

How to cite: Zhang, C., Jiang, Z., Zhang, C., Chen, Z., Sun, P., and Zhu, T.: Historical soil erosion events in border polje revealed by geochemical fingerprint analysis of soil profiles, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5010, https://doi.org/10.5194/egusphere-egu25-5010, 2025.

To mitigate erosion, soil and water conservation measures have been widely implemented to reduce on-site erosion rates and catchment sediment yield. However, the effectiveness of these measures has often been questioned, particularly in Ethiopia, where gullying has intensified due to conservation programs that primarily target sheet and rill erosion on cropland. This study aimed to identify erosion hotspots and sediment source areas using an integrated approach. The study was conducted in the 211 km² Fota-Gumara catchment, a highly erosion-prone area in Northwest Ethiopia. First, erosion hotspot areas were identified through field observation, farmer’s interview and modelling. Then, sediment sources areas were identified using sediment fingerprinting by employing fallout radionuclide tracers (210-Pbex and 37-Cs). Local communities identified communal grazing lands and croplands as particularly vulnerable to erosion. Field observations corroborated these findings, highlighting steep slope cropland and grazing land as erosion hotspots. The Analytical Hierarchical Process (AHP) model indicated that 23.5% of the area experiences severe erosion, predominantly on steep slopes under cropland, shrubland, and valley bottoms where saturation excess runoff drives gullying. Sediment fingerprinting further revealed that subsoil is the dominant source of sediment. Bayesian models (MixSIAR and BMM) consistently showed that subsoil contributes approximately three-quarters of the sediment, with median contributions of 73% and 81%, respectively. We conclude that prioritizing gully rehabilitation and managing steep slope croplands should be central to land management strategies in Ethiopia.

Keywords: Sediment fingerprinting, Lake Tana Basin, Land Degradation Surveillance Framework, Analytical Hierarchical Process Model, Gully erosion

How to cite: Abere, T., Evrard, O., Chalaux-Clergue, T., Adgo, E., Lemma, H., Verleyen, E., and Frankl, A.: Identifying hotspots of erosion from local knowledge and sediment fingerprinting (Lake Tana Basin, Ethiopia), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7219, https://doi.org/10.5194/egusphere-egu25-7219, 2025.

Human activities like deforestation intensify runoff and soil erosion, leading not only to local land degradation but also to off-site impacts such as excessive lake sediment deposition. Climate change may further exacerbate the erosion rate, particularly where human activity is highest. Hence, the sustainability of natural lakes is threatened by soil erosion and climate change. This is certainly the case for the tropical lakes of Abaya and Chamo in the southern Ethiopian Rift Valley. High rainfall intensities, steep slopes, and increasing population levels make these lakes susceptible to high rates of sedimentation, and rising water levels due to changing sediment and water budgets lead to coastal flooding of agricultural land and infrastructure. However, in order to properly assess the impact of human-induced land use change and climate on the lakes, quantitative assessments of the water and sediment delivery to the lakes are required. High-quality data are often missing for tropical lake environments, especially in developing countries. 

Here, we established seven streamflow and suspended sediment concentration (SSC) monitoring stations across four selected rivers draining to Lake Abaya and Lake Chamo: Bilate (5480 km²), Elgo (298 km²), Kulfo (467.2 km²) and Shafe (191 km²). Together, these stations monitor 35% of the total area contributing to both lakes. Streamflow was measured at 10-minute intervals using a transducer, with atmospheric pressure corrections from a Baro diver. In total, 3501 samples were collected to measure SSC. Observed SSC ranges from 0.08 g/l to 107.75 g/l, whereas discharge varies between 0.01 and 410.65 m³/s. Sediment rating curves were developed using SSC and streamflow data to enable the estimation of total suspended sediment yield (SY) using continuous streamflow records. SY from the four gauged catchments was calculated at 11.3 Mt/year, with area-specific SY varying between 1083.43 and 10117.5 t/km²/year. Overall, Bilate River contributes 67% of the total sediment load, making it the most significant river in terms of the total SY. However, when normalized by catchment area, the Gamo highland catchments have higher net erosion rates. Strong temporal variability in SSC and SY is observed, which can be explained by seasonal changes in vegetation cover and rainfall intensity. Time series of SSC for each river can be correlated with NDVI-data in the corresponding catchments and rainfall erosivity calculated from high-resolution meteorological data. Catchments draining the Gamo highlands have their highest sediment transport rates at the start of the rainy season (May to June) when vegetation cover is low, contributing 60% of SY. In contrast, Bilate, which drains the rift valley itself, experiences a peak sediment yield in August-September, representing 61% of its annual SY.

The integration of satellite-derived NDVI, high-resolution rainfall erosivity data, and timeseries of SSC and discharge enables to identify periods and areas of enhanced erosion and sediment delivery to the lakes. Such spatio-temporal information will be used to calibrate and validate erosion models, which in turn can simulate the impact of management scenarios on lake water and sediment budgets.

How to cite: Ayana, M. T., Tilahun, A. K., Minda, T. T., and Verstraeten, G.: Monitoring water and sediment delivery to Lake Abaya and Lake Chamo in the Southern Rift Valley Basin, Ethiopia  , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16326, https://doi.org/10.5194/egusphere-egu25-16326, 2025.

Sediment production is often intensified in peri-urban areas as landscapes transition from predominantly rural to urbanized conditions. This transformation alters hydrological and sediment dynamics, which are complex and remain poorly understood, particularly during the process of urbanization. There is a need to begin systematically monitoring the impacts of urbanization on sediment production and transport. This study focused on monitoring suspended solids concentrations and loads in stormwater drainage systems over six months in Officer, Melbourne – a peri-urban area experiencing rapid urban development. Using low-cost automatic monitoring stations developed by our research team, we collected data across sites with different stages of urbanization, ranging from early construction to fully developed areas.

We found that during storm events, mean concentrations of suspended sediments in early urbanization stages can reach up to 100 times those observed in mature urbanized areas. Most importantly, suspended sediment yields in early-stage urbanization areas were up to 10 times higher than in fully developed areas, despite lower runoff volumes. Sediments from early stages of development were also finer than sediments from later stages. These high loads of fine sediments present increased risks to receiving water bodies, such as streams, bays, and wetlands, due to their ability to transport pollutants over long distances and contribute to environmental degradation.

The findings highlight the value of combining innovative monitoring technologies with geospatial and time series analysis to better understand sediment dynamics in a complex and rapidly urbanizing landscape. Additionally, the findings underscore that erosion and sediment control measures are vital, particularly during the early stages of urbanization, requiring proactive management throughout this process to mitigate fine sediment impacts and protect downstream waterbodies, ensuring sustainable growth in peri-urban areas.

How to cite: R. M. da Silva, P. V., L. Russell, K., D. Fletcher, T., Cherqui, F., Navratil, O., and Cossart, E.: Early-stage urbanization drives critical sediment production, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3910, https://doi.org/10.5194/egusphere-egu25-3910, 2025.

Artificial fallout radionuclides (FRNs), such as ¹³⁷Cs and ^239+240Pu, released during nuclear weapon testing from the 1950s to 1980, have been widely used over the past three decades to quantify land degradation processes. The spatial distribution of global fallout generally aligns with latitudinal bands in areas with similar precipitation regimes. Despite nearly 80 years since these tests, no comprehensive reference map exists for FRN inventories across the Southern Hemisphere.

Therefore, this study aims to create the first complete reference maps for ¹³⁷Cs and ^239+240Pu along with their spatial uncertainties over the entire Southern Hemisphere and Equatorial band. To accomplish this objective, we employ the random forest algorithm to predict the concentrations of FRNs in soils of this part of the world. This is achieved by utilizing a compiled data set of soil ¹³⁷Cs (n=429) and ^239+240Pu (n=102) inventories (Bq/m²) (Dicen et al., 2024; under review) under the AVATAR Project (“A reVised dATing framework for quantifying geomorphological processes during the Anthropocene”). The training phase of modeling relied on environmental covariates, including monthly mean precipitation (following test months), elevation (m.), euclidean distance to test sites (km.), terrain wetness index, flow accumulation, and soil texture.

Preliminary results indicate that precipitation distribution strongly influences FRN inventories, with the highest values observed between 20°S to 30°S due to atmospheric circulation patterns driving fallout dispersion. Consistent with previous studies, southern America emerges as a major depositional region, while Australia exhibits the lowest inventories. These differences primarily reflect the proximity to nuclear test sites, such as French Polynesia, a significant source of fallout radionuclides. The euclidean distance and westerly wind patterns are key factors shaping FRN inventories.

In equatorial regions, recent land disturbances highlight the need for additional sampling, particularly for ^239+240Pu, to enhance prediction accuracy and reduce spatial uncertainties. This study addresses critical gaps in the spatial distribution of FRN inventories, providing a robust foundation for geomorphological reconstructions in the Southern Hemisphere and Equatorial regions.

How to cite: Avcioglu, A., Gupta, S., Dicen, G., Vandromme, R., Alewell, C., Cerdan, O., Evrard, O., Bernard--Coquard, R., Angot, H., Sabatier, P., and Meusburger, K.: Reconstruction of 137Cs and 239+240Pu baseline inventories in the Southern Hemisphere and Equatorial Soils, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9055, https://doi.org/10.5194/egusphere-egu25-9055, 2025.

Karst aquifers, supplying nearly 25% of the global population with drinking water, are critical yet vulnerable resources. While sediment transport modeling in karst systems has progressed, fluviokarst systems remain underexplored, particularly regarding multilayer sediment dynamics during diverse hydrologic events. This study introduces a novel framework integrating stable isotope analyses (δ¹³C, δ¹⁵N) with high-resolution sensor data to investigate sediment transport mechanisms in Kentucky’s mature fluviokarst systems, focusing on the Cane Run Watershed and Royal Spring Basin in central Kentucky, USA.

The multilayer framework hypothesizes that sediment stored at different depths within fluviokarst caves originates from distinct sources and undergoes unique transport processes. During large hydrologic events, a single active sediment layer forms, mobilizing material from sources in the fluvial system to the cave outlet via suspension. Smaller hydrologic events activate only the top sediment layer within the cave, with transport characterized by intermittent deposition and resuspension of surface sediments, fluctuating between suspension and saltation. Surface processes across the fluvial system exhibit a similar pattern: smaller hydrologic events mobilize loose surface material, while larger hydrologic events erode deeper soil layers through gully formation, transporting material into the karst cave systems.

Tracer-aided modeling, combining sediment fingerprinting and sediment continuity equations, revealed two primary transport types: (1) larger hydrologic events characterized by high sediment trap weights, lower soil organic carbon (SOC) and total nitrogen (TN) values, less negative δ¹³C, and more positive δ¹⁵N values; and (2) smaller hydrologic events dominated by surface-derived material with higher SOC and TN values, more negative δ¹³C, and less positive δ¹⁵N values. Isotopic trends highlighted interactions between cave-stored sediment and external sources, with high-discharge hydrologic events mixing bottom layers and low-discharge hydrologic events remobilizing deposited sediment.

Three temporal periods were identified, reflecting the stream’s response to in-stream reconstruction: (1) a pre-reconstruction period with low sediment loads, (2) a reconstruction period with elevated sediment loads from disturbances, and (3) a post-reconstruction recovery period with reduced sediment loads as the stream stabilized.

This research provides critical insights into sediment transport dynamics in fluviokarst systems, emphasizing the interplay between hydrologic variability, sediment sources, and anthropogenic impacts. It advances predictive capabilities for sediment behavior under future hydrologic and climatic conditions.

How to cite: Bettel, L., Fox, J., Riddle, B., Beckman, M., Zhu, J., and Al Aamery, N.: Multilayer Sediment Dynamics in Fluviokarst Systems: Insights from Stable Isotopes and Sensor Measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13413, https://doi.org/10.5194/egusphere-egu25-13413, 2025.

Global population growth and economic growth lead to increasing energy demand. This propels the construction of river dams and artificial reservoirs to produce hydropower. Ecological effects of water impoundments, such as the fragmentation of free-flowing rivers, habitat changes, loss of habitats and biodiversity, and changes in biogeochemical cycles have been addressed by researchers for several decades. Also, the influence of flooding on the soils within reservoirs and shore erosion have been studied in a variety of environments and soil types. The development of soil carbon stocks in the submerged soils and soil carbon mineralization upon flooding are of particular interest. Some studies observe a significant decrease of carbon stocks in submerged soil, whereas others report the opposite. Here, we present a study on the influence of 24 years of water impoundment on properties of organic and mineral constituents in submerged Andosols of the Blöndulón hydro-electric reservoir in the Icelandic highlands. Drowned soils are relatively enriched in carbon content, carbon densities and carbon stocks compared to the reference soils, while they are depleted in pedogenic minerals ferrihydrite and allophane. Depth patterns of carbon are rather uniform in the drowned soils in contrast to declining trends in the reference soils. Likely, movement of organic material from upper to lower horizons, and carbon additions from decaying vegetation in the years after the reservoir impoundment explain the carbon enrichment and altered depth distribution. While the drowned soils are enriched in carbon after a comparatively short inundation time of less than three decades, the stability of the soils carbon is uncertain. The apparent loss of mineral soil colloids will likely render the carbon more sensitive to oxidation in the coming decades, particularly during times of exposure of the inundated soils. Assessments of the consequences of water level fluctuations or potential future dam removal need to take the vulnerability of the exposed soils into account.

How to cite: Möckel, S. C., Bonatotzky, T., Mankasingh, U., Alvarez, I., Erlendsson, E., and Gísladóttir, G.: Carbon stocks in submerged soils of a hydro-electric reservoir after 24 years of flooding, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12254, https://doi.org/10.5194/egusphere-egu25-12254, 2025.

Small, shallow lakes are under severe stress from the combined impact of anthropogenic eutrophication and modern climate change. Therefore, such lacustrine sediments provide key information for understanding the lake’s eutrophication and the ongoing unprecedented climate change. The present work focuses on the saline Kallar Kahar Lake located in the Salt Range of Pakistan, to unravel the extend of anthropogenic impacts and climate change on sedimentation in lakes using a core section of 180 cm. Dark gray marly mud dominates with interlayered greenish-gray sandy/silty layers in the lower part. Geochemical results indicate that the SiO₂ and Al₂O₃ contents drop to around one-third (from 54.6% to 16.4% and from 9.8% to 3.5% respectively) vertically upward in the cored interval, whereas the CaO content displays a three-fold upward increase (from 11% to around 30%). Similarly, the Total Organic Carbon (TOC) and Total Organic Sulphur (TOS) contents show a three-fold vertical upward increase (from 3% to > 15% and < 0.3%  to 0.9%). The paleoredox proxies V/(V + Ni), V/Cr, and especially Th/U indicate an upward decrease in the oxygenation level and establishment of an anoxic setting in the lake. Paleoclimate proxies including Mg/Ca, Rb/Sr, and Sr/V indicate a progressive upward increase in the aridity. Paleosalinity proxies Sr/Ba and Rb/K  suggest an upward increase in the salinity of the lake. The anthropogenic impact proxy elements Mo and Hg indicate enrichment and display strong negative correlations with detrital supply. Similarly, As, Pb, Zn, and P neither correlate with the detrital influx proxies nor with in situ sedimentation proxies thereby pointing to their anthropogenic source. These results indicate that urbanization and anthropogenic activities have blocked the natural drainage of the Kallar Kahar Lake, reducing the detrital influx to around one-third. The increasing aridity of the area due to modern climate change has transformed the lake into a closed-water body where evaporation has increased the salinity forcing a nearly three-fold increase in the in-situ organic carbonate production in the sampled interval. Thus the Kallar Kahar Lake provides an ideal case study site to understand the eutrophication of shallow lakes due to anthropogenic drainage blockage, pollutants inputs and impacts of modern climate change that is observed in many small shallow lakes globally.

How to cite: Iqbal, S., Bibi, M., and Wagreich, M.: Geochemical signals for anthropogenic eutrophication and climate change from the Kallar Kahar Lake, Salt Range, Pakistan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19498, https://doi.org/10.5194/egusphere-egu25-19498, 2025.

The growth of a territory is usually linked to the increase of contamination with Potentially Toxic Elements (PTE), which show stable, persistent, and non-biodegradable characteristics. PTEs became of great interest because they threaten humans and ecosystems through their bioaccumulation capacity and mobility in water systems. The main source of high levels of PTE is human activities such as mining, industries, and factory emissions. The erosion of soils contaminated by emissions and deposits of these activities can lead to great contamination levels in sediments, which greatly concerns environmental quality.

This study aims to identify the impact of intensive past mining and smelting industries on the metal and metalloid contents in actual alluvial surface sediments. To assess the associated environmental risks, index calculations, and statistical treatments have been carried out on 78 sediment samples in both natural and urban streams. The two main studied areas are the Furan River watershed and the Ondaine River watershed (close to the city of Saint-Etienne, France), with about 10 samples on each river in addition to the tributaries samples (around 20 by river).

The study outcomes mainly show values above TEC values for As, Cu, Ni, Pb, and Zn, indicating that the contamination poses a potential threat to natural ecosystems. Moreover, the enrichment factor of PTEs, calculated along the length of rivers, indicates moderate pollution (> 2), after the biggest cities, which decreases with the distance downstream for Cr, Ni, Pb, and Cu for both rivers. The Furan River has even higher enrichment for Cu and Mo, as significant pollution (> 5) can be observed before decreasing to no pollution levels. On the other hand, Zn values stay at a limited pollution level over the entire rivers length. The overall moderate contamination of PTEs shown by the enrichment factor indicates high risks for the environment linked to human activities. To quantify the danger, a hazard index was determined, for all the PTEs of interest, on each sample. The results show that the PTEs levels are not of any harm for the environment, except for four samples that indicate high risks compared to the local geochemical background (SIGMINES database). This index puts the real risk for the environment into perspective since only 4 samples out of 48 show actual hazards.

In light of these observations, statistics (Principal Component Analysis and Correlation Matrix), and previous studies on similar areas, some links could be built with metalworking (Furan River) and dyes and paints industries (Ondaine River). However, in the absence of further evidence, it is not certain how this conclusion can be associated with past activities.

How to cite: Seillier, R., Riquier, J., Paran, F., Peuble, S., Faure, O., and Bouillot, B.: Alluvial surface sediments as a tool for Heavy Metal Pollutants determination of areas with strong industrial heritage , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5607, https://doi.org/10.5194/egusphere-egu25-5607, 2025.

Urban deposits pose many challenges compared to natural archives. Due do anthropogenic influence they often have only limited lateral continuity, highly variable deposition rates, are prone to (anthropogenic) erosion, reworking and resedimentation, and show omission surfaces. In Vienna (Austria) we investigated sediments from an archaeological excavation site near the city centre as part of a transdisciplinary project involving geosciences, isotope physics and urban archaeology. The study area at Karlsplatz is situated near the Wien River and records the change in land use of the expanding city. The site covers a section from natural flood sediments (17th century) and anthropogenic fill (before 1900) of the Wien River to the latest levelling period of the park area in the 1950s. Archaeological stratigraphy and historic data sets provide age constraints for the multiple deposition phases, with the oldest road structures dating from the 18th century and the youngest deposits dating around 1922, post-1945 and the park opening in 1959 (Mosser et al., 2022). Atmospheric bomb-testing fallout plutonium was used for further Anthropocene age constraints (Wagreich et al., 2023) dating the upper layer as deposited between 1952 and 1959.
The fine-grained matrix (< 2 mm grain size) of the deposits was used for X-Ray fluorescence (XRF) analysis of trace elements such as lead, copper and zinc. The highest levels of trace metals (Cu 330 ppm, Pb 633 ppm, Zn 852 ppm) are present in sediments of a 19th century deposit rich in charcoal and metal slags associated with nearby metal-working industry. The second highest peak occurs in a layer of WW2 rubble rich in technofossils of that era (Cu 71 ppm, Pb 208 ppm, 296 ppm). Overlying deposits of the 1950s show again much lower values (Cu 24 ppm, Pb 28 ppm, Zn 61 ppm) similar to the range of low contamination background and infill materials, although the uppermost topsoil layer shows a slight recent enrichment (Cu 35 ppm, Pb 56 ppm, Zn 99 ppm) compared to the 1950s. Spheroidal carbonaceous fly-ash particles (SCPs), the product of industrial coal and oil combustion, were found in elevated concentrations in the post-1945 levels. These results indicate both a local (iron industry of the 19th century, WW2 pollution) and a regional-global (e.g. lead from leaded gasoline, fly ash particles) control on trace metal and fly ash contamination and a correlation with technofossil findings. In conclusion, additional stratigraphic markers for the Anthropocene were identified and quantified in the urban anthropogenic sediments of the Karlsplatz site. Therefore, the site may be used as a correlative stratigraphic reference section for the Anthropocene.

References:

Mosser et al. 2022. Fundort Wien, 25, 2022, 4-53.

Wagreich et al., 2023. The Anthropocene Review, 2023, 10/1, 316-329. doi 10.1177/20530196221136427

How to cite: Meszar, M., Wagreich, M., Mosser, M., Rose, N., Nagl, P., and Hain, K.: Additional stratigraphic marker for an Anthropocene at the Karlsplatz reference site (Vienna, Austria), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19703, https://doi.org/10.5194/egusphere-egu25-19703, 2025.

Mountain catchments are highly sensitive to the impacts of global warming, which affects seasonal weather patterns, glacier retreat, permafrost thawing, and snow cover duration. These changes drive rapid transformations in their ecosystems and alter their hydrological and sedimentological regime, exacerbating their susceptibility to various hazards, including floods, shallow landslides, and debris flows, all closely tied to sediment dynamics. Consequently, sediment management plays a key role in developing watershed management strategies that lead to programme interventions for mitigating potential losses for the mountain communities.

In this context, an integrated approach combining field surveys and aerial imagery analysis is essential for evaluating the effectiveness of existing countermeasures (mainly torrent control structures) and for finding innovative solutions, especially in absence of sediment transport monitoring systems. This approach enables the collection of observations on lithology, geology, channel cross-section shape, longitudinal profiles, land use, active soil movements, and grain size distribution within sediment source areas and along the channel network. The field inspections of torrent control structures further provide a detailed assessment of their condition and functionality.

All these observations are essential for geomorphological approaches, statistical formulae, and hybrid methods to estimate potential debris flow volumes at both reach and catchment scales. Additionally, simplified rainfall-runoff modelling, such as the SCS-CN method, is employed to assess critical runoff thresholds that could trigger water-sediment flows. The outputs include the spatially distributed assessments of in-channel and hillslope sediment storage volumes, and the delineation of sediment source areas. Aerial imagery complements this process by verifying the spatial distribution and extent of sediment source areas and tracking land cover changes over time.

The proposed methodology was developed and applied to the Rovina Torrent basin, located in the Central Alps (Lombardy, North Italy). The basin is characterized by coniferous forest cover (37.2%) and extensive debris accumulations and lithoid outcrops (36.7%). In the study case, the results provide the typologies in terms of driving the triggering event mode within the catchment, the minimum critical rainfall for designing an early warning system, and the potential debris flow volume for adjusting the sediment trapping basin.

The outcome significantly enhances the accuracy of hazard mitigation strategies and supports the adaptation or redesign of the torrent control structures to better address evolving sediment dynamics. The combination of the scientific experience in similar mountain context and the additional field observations can quantitatively provide a robust diagnosis of the current scenario for planning maintenance operations, for proposing and designing alternative solutions to reduce the natural hazard and for effectively supporting the decision-making process including the strategic allocation of human and financial resources.

How to cite: Cislaghi, A., Morlotti, E., and Bischetti, G. B.: Combining field and aerial imagery monitoring for planning maintenance operations and strategies in an ungauged mountain catchment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4443, https://doi.org/10.5194/egusphere-egu25-4443, 2025.

In recent decades, watershed management has assumed a pivotal role in the face of the progressive anthropization of land use and the increasing frequency of extreme hydro-geomorphic events caused by climate change. Indeed, the reduction of hydro-geological risk in mountain basins is contingent on the effective and sustainable design of torrent control structures, including check dams and bed sills.

The up-to-date knowledge of basin morphology and the comprehension of the interaction between torrent control works and hydro-geomorphological phenomena represent fundamental elements for designing, managing and maintaining mountain watersheds. Nowadays, the interpretation of basin processes is significantly enhanced using accurate, high-resolution remote sensing (RS) data, in conjunction with analyses employing GIS software. However, the use of such techniques is not yet widespread and there is a need for user-friendly tools to facilitate the effective processing of RS data to support planning and management activities.

To address these demands, this work proposes the development of a QGIS plugin (i-GIS4HydroPlan) to fully support the hydrological design of torrent control structures, implementing functions such as the automatic extraction of watershed boundaries from the Digital Terrain Model (DTM), the calculation of the flow directions, upslope contributing areas, routing, and, finally, the design hydrograph. This output is estimated through the Kinematic Local Excess Model (KLEM), an event-based model applicable to small mountain basins that combines the equations of the Soil Conservation Service for the calculation of the effective rainfall, the kinematic method for the flow propagation to the outlet and a linear reservoir for the simulation of base flow. Moreover, the plugin incorporates functionalities that facilitate the management of multi-temporal DTMs, thereby enabling a comprehensive analysis of sediment dynamics within the entire basin or single torrent reaches equipped with torrent control structures. The module encompasses algorithms for the co-registration of DTMs and the error analysis that affects the DTM of Difference (DoD).

The plugin will be distributed under an open-source license with the objective of enhancing its dissemination and facilitating the standardization of workflows. This will in turn allow a more efficient design of new torrent control works and the assessment of existing structures to determine their criticality and establish maintenance priorities.

Acknowledgement: This study was funded by the European Union - NextGenerationEU, in the framework of the consortium iNEST - Interconnected Nord-Est Innovation Ecosystem (PNRR, Missione 4, Componente 2, Investimento 1.5, D.D. 1058 23/06/2022, ECS00000043 – Spoke1, RT1B, CUP G23C22001130006). The views and opinions expressed are solely those of the authors and do not necessarily reflect those of the European Union, nor can the European Union be held responsible for them.

How to cite: Maset, E., Cucchiaro, S., De Luca, A., and Cazorzi, F.: An open-source QGIS plugin to support hydrological and watershed management planning in mountain basins, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9960, https://doi.org/10.5194/egusphere-egu25-9960, 2025.

Monitoring and maintenance are crucial for effective mountain catchments management, particularly in mitigating geo-hydrological risks. Torrent control structures, such as check dams and bed sills, play an important role in stabilising streambeds and reducing the impact of hydrological events such as floods and debris flows. However, their effectiveness depends on proper watershed management supported by systematic monitoring, which must consider sediment dynamic characterizing the catchment.

Nowadays, the use of High-Resolution Topography (HRT) data could support torrent control structures monitoring. Light Detection and Ranging (LiDAR) technology has become a standard approach for generating reliable Digital Terrain Models (DTMs) and conducting multi-temporal analyses. When morphometric data derived from DTM are combined with up-to-date inventories of torrent control structures, they offer valuable insights into the condition and functionality of these structures.

This study aims to develop and implement an index to identify torrent control structures in the most critical condition at a regional scale, with validation conducted at basin scale. The primary study areas are But (324 km²) and Fella (703 km²) catchments in the Friuli Venezia Giulia region (Italy) on the border with Slovenia and Austria. The methodology integrates HRT-derived data with information from the regional inventory of torrent control structures. The developed index considers characteristics of the structures, such as height and year of construction, alongside site-specific factors like geology and morphometric parameters derived from DTMs. The results show how this type of analysis can prioritize maintenance interventions and enhance the management of torrent control structures.

How to cite: Chiarel, G., Cucchiaro, S., Cavalli, M., and Cazorzi, F.: Torrent Control Structures Monitoring: a Regional Scale Index based on Inventory Analysis and Remote Sensing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6376, https://doi.org/10.5194/egusphere-egu25-6376, 2025.

Hydrological forcings and erosion dynamics are influenced by natural factors and anthropogenic activities. Flooding events associated with climate change are attributed to heightened rainfall intensity and frequency, alterations in landscape patterns across various scales, and an elevated risk of flooding and water scarcity. This study combined landscape pattern indices with sediment connectivity to analyze changes in sediment connectivity during extreme rainfall events in various check dam-controlled hillslope-gully systems. Aerial and field surveys of four systems within the Caijiachuan watershed, conducted before and after the rainstorm event in October 2021, utilized unmanned aerial vehicles (UAVs) and remote sensing imagery. Landscape indices were applied to analyze the spatial pattern characteristics preceding and following the rainstorm event. The sediment connectivity index (IC) assessed sediment transport connections in the chosen systems. It was found that extreme precipitation led to increased landscape fragmentation, decreased biodiversity, and higher sediment connectivity, especially on steep slopes compared to gully channels. Soil erosion hotspots were found on slopes between 0-50°, with landslides occurring in areas of high sediment connectivity. This altered the landscape pattern and further boosted sediment connectivity. Various hillslope-gully systems reacted differently to rainstorms. This study highlights the value of using sediment connectivity to assess check dams' responses to extreme precipitation, improve watershed and land management strategies, and evaluate soil erosion control measures in fragile ecosystems.

How to cite: Yu, Y., Feng, J., Zhang, Z., Crema, S., and Cavalli, M.: Divergent responses of hillslope-gully systems controlled by check dams to rainstorm events in the Loess Plateau, China., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16498, https://doi.org/10.5194/egusphere-egu25-16498, 2025.

The Hindol block in Dhenkanal, Odisha, with an average annual rainfall exceeding 1200 mm, faces persistent challenges in managing runoff and sedimentation. This study evaluates the effectiveness of soil and water conservation (SWC) techniques in mitigating runoff across clusters of untreated micro-watersheds within this region.

A water balance analysis, focusing primarily on surface runoff, was conducted using the Soil and Water Assessment Tool (SWAT). The model incorporated high-resolution datasets, including digital elevation models, land use, recent Land Resource Inventory (LRI) data, and local weather records. Based on the hydrological assessment, a series of SWC interventions were designed, including contour bunding, trench cum bunds, staggered trenches, and Drainage Line Treatment (DLT) measures such as loose boulder check dams, brushwood check dams, and gabions.

These interventions were simulated in the SWAT model by adjusting critical hydrological parameters, such as Curve Number (CN2), Universal Soil Loss Equation Factor (USLE_K), Manning’s roughness coefficient (CH_N), and tributary slope (CH_S). Comparative analyses of pre and post implementation scenarios demonstrated significant reductions in runoff volumes. The extent of these reductions varied with the type and combination of conservation measures implemented.

The results underscore the potential of integrated conservation strategies to mitigate runoff and restore hydrological balance in sub-watersheds with similar agro-climatic and topographical conditions. This study provides practical insights for watershed management practitioners and policymakers, facilitating informed decisions on selecting and implementing conservation measures to address runoff and sedimentation challenges.

How to cite: Biswal, S. S., Dash, P., and Ramadas, M.: Evaluation of Conservation Treatment Measures for Runoff Reduction using A SWAT Model-Based Approach: A Case study in Hindol Sub-watershed, Dhenkanal, Odisha, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6778, https://doi.org/10.5194/egusphere-egu25-6778, 2025.