In mountain areas, debris floods and debris flows threaten the lives of people and endanger buildings and infrastructures worldwide. The hazard assessment of such phenomena is a crucial process for hazard mapping and, eventually, design mitigation structures. The classical approach consists in the evaluation of the return period of a certain rainfall intensity that can mobilize a given amount of sediment and generate a debris floods/flows phenomenon consequently. Researchers have made progress in understanding these phenomena over the past decades, enhancing the ability to predict their impacts. Through an extensive literature review, we have fine-tuned an innovative procedural framework that takes into consideration most of the predisposing factors and processes that lead to the increase of destructive potential of debris flow and debris flood phenomena. The investigated aspects are: (i) exogenous forces (climatic, natural and anthropic disturbance related aspects); (ii) alterations of the catchment and channel conditions (countermeasures malfunctions/failures, bed/banks/slopes disposal to erosion, Large Wood presence); (iii) flow type variations (changes in transport behaviour and typology). The outcome of the study is a perspective hazard map that accounts for all of these factors and processes together with an estimation of the probable long-term evolution of the catchment response, accounting for climate change too. The study was supported by the analysis of four different catastrophic debris flow and debris flood events for which factors and processes increasing the destructive potential have been analysed.
The study highlights that joined processes and basin conditions, which are not necessarily related to rain events of high return period, should also be considered in the hazard evaluation of mountain catchments. The related hazard assessment should move toward a global and tailored assessment of the potential catchment responses, and possibly accounting for the residual hazard component. The proposed framework aims to outline guidelines to assist practitioners and civil authorities in better defining the hazard classes and consequently reducing the uncertainty associated with probable future debris flow and debris flood events.
How to cite: Bettella, F., Baggio, T., Martini, M., and D'Agostino, V.: A tailored framework for debris flow and debris flood hazard assessment in mountain catchments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11847, https://doi.org/10.5194/egusphere-egu25-11847, 2025.
On July 20, 2024, a catastrophic group-occurring debris flow event occurred in the Malie Valley, southwestern China, involving nine debris flows primarily initiated by widespread shallow landslides. The event was triggered by a short-duration nighttime rainfall. The triggering rainfall intensity was 25.44 mm/h, and the Malie Valley was nearly at the center of the rainstorm. Since 2000, four historical rainfall events in the region have exceeded this intensity, yet none resulted in debris flows. The total daily rainfall during the event was 100.5 mm, corresponding to only 20-year return period. While differences in long-term antecedent effective rainfall (AER) between this event and previous heavy rainfall events were small, the 3-day AER reached 108.75 mm, which was 4 to 20 times greater than that of earlier events. These findings underscore the critical influence of short-term AER preceding intense rainfall in triggering group-occurring debris flows.
How to cite: Li, H., Hu, K., and Liu, S.: Analysis of antecedent and real-time rainfall characteristics of a large-scale debris flow event in Southwest China in 2024, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17685, https://doi.org/10.5194/egusphere-egu25-17685, 2025.
Volcanic debris flows are large-scale, gravity-induced mass movements involving mixtures of water, mud, and volcanic sediments. These phenomena are among the most hazardous in volcanic regions, characterized by high impact forces, extended runout distances, rapid velocities, and unpredictable timing. The stability of a slope depends on the balance between driving forces (shear stress) acting parallel to the surface and resisting forces (shear strength), strictly connected to the particle size distribution, bulk density, degree of aggregation, and organic matter. Soil water content plays a critical role in this balance, influencing cohesion and internal friction, often leading to failure under lower shear stress thresholds for the same material and boundary conditions.
This study investigates the Campanian Volcanism region, an area of approximately 2,000 km² that includes over 100 towns identified as at risk. Particular attention is given to Sarno, a municipality in the western Campanian Apennines that experienced devastating rainfall-triggered debris flows on May 5–6, 1998, resulting in 160 fatalities and widespread damages. The region's deposits are composed of alternating pyroclastic layers (ashes and pumices) and colluvium overlying steep calcareous bedrock, a combination of factors that create conditions highly favourable to slope instability.
The primary aim of this research is to assess how variations in soil moisture content influence the shear strength of volcanic ash deposits, with a focus on defining the failure envelope as described by Mohr’s criterion. Laboratory analyses are conducted using an Anton Paar MCR 703e rheometer at the Chemistry Department of the University of Bari.
Ash samples collected from Sarno are subjected to controlled hydration tests, starting from a completely dry state and gradually increasing moisture content under carefully monitored conditions. Due to the specific design of the rheometer’s shear cell, the study is limited to particles passing through a 710 µm sieve. Additionally, X-ray diffractometry is employed to identify and characterize possible clay minerals in the samples, as different clay types can significantly affect soil rheological behaviour.
The findings of this study provide critical insights into the relationship between moisture content and shear strength, advancing our understanding of slope stability and the triggering mechanisms of debris flows. The obtained results will contribute to improving predictive models and informing mitigation strategies in volcanic regions.
How to cite: Pace, L., Capolongo, D., Capparelli, G., Dellino, P., Dioguardi, F., Gentile, L., and Sulpizio, R.: Moisture Effects on Shear Strength and Slope Stability: Volcanic Ash Deposits from Sarno, Campanian Volcanism Region, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-910, https://doi.org/10.5194/egusphere-egu25-910, 2025.
In semi-arid regions of the United States rainfall intensity thresholds are used to estimate when postfire debris flows may occur. Prior research has shown that postfire debris flows are highly correlated with short-duration rainfall intensity, and that short duration rainfall thresholds (e.g., 15-minute rainfall intensity) can be estimated based on wildfire and terrain attributes. Consequently, it is possible to determine possible debris flow activity in recent burn areas in the western United States by tracking rainfall rates using publicly available rainfall data. We have developed a software (FlowAlert) and an accompanying map dashboard that monitors when and where rain gages near burn areas cross rainfall intensity thresholds. The software runs continuously on a linux server, processing more than 2500 rain gages every two hours. When rainfall rates near a burn area are higher than a rainfall threshold, symbols are updated on a map indicating possible debris flow activity. Rainfall plots are also provided on the dashboard, and via email alerts for the gages that have crossed the rainfall intensity threshold. FlowAlert can be used for situational awareness to alert authorities of potential debris flow activity in remote areas. Additionally, the data stream produced by FlowAlert can be used by managers to adjust the rainfall intensity threshold in areas following storms based on observed activity. For example, if rainfall thresholds were crossed, but no debris flows were observed, managers may choose to increase the rainfall threshold to avoid warning fatigue. This presentation will focus on the utility of the new FlowAlert software, and how it might be used for decision support in burn areas.
How to cite: Rengers, F., King, R., and Schmitt, R.: Situational Awareness of Postfire Debris Flow Activity using Big Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1663, https://doi.org/10.5194/egusphere-egu25-1663, 2025.
Innovative Approaches to Debris Flow Protection: Insights into Baffle Positioning and Design Optimization
Baffles effectively reduce debris flow velocity and kinetic energy, altering movement distance and accumulation patterns, and are widely used for mitigating natural disasters like landslides and mudslides. This study utilized the three-dimensional Discrete Element Method (DEM) to investigate the effects of baffle positions on debris flow protection. Through single-factor experiments, velocity and energy variations were analyzed, and the influence of the first-row baffle position on impact force and accumulation mass was evaluated to determine suitable positions.
Subsequently, an orthogonal design explored the effects of four key factors—baffle position (P), height (h), row spacing (Sr), and transit area angle (α)—on the performance of baffle arrangements. Results indicated that baffles placed in the transit area outperformed those in the deposition area, showing greater energy dissipation and flow mass obstruction. Range analysis ranked the influencing factors for impact force as α > P > Sr > h, while for mass reduction, the ranking was P > α > Sr > h. The optimal arrangement was identified as P5, Sr=16, α=35°, and h=9, providing a framework for improving debris flow mitigation strategies through optimized baffle design.
How to cite: Jiang, Z.-Y. and Bi, Y.-Z.: Innovative Approaches to Debris Flow Protection: Insights into Baffle Positioning and Design Optimization, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1554, https://doi.org/10.5194/egusphere-egu25-1554, 2025.
The lower reaches of the Yarlung Tsangpo-Brahmaputra River are important hydropower development bases in the future. However, frequent glacier landslide hazard occurred in this region, posing serious threats to the safety of local communities and infrastructures. A glacier landslide hazard chain can form a long-run mass flow and generate a large flood, travelling more than hundreds of kilometers away from the initiating hazard site. This study takes remote sensing, field investigations and numerical simulations to make risk assessment on the river system. A comprehensive framework is developed, considering the impacts of near-field and far-field hazards. The findings suggest that the presence of extensive, nearly saturated sediments on the glacier valley floor significantly increases the mobility and intensifies the scale of the mass flow when these sediments are incorporated. Topography plays a key role in influencing the behavior of mass flow. When the valley outlet intersects the river course at a perpendicular angle, topographic barriers lead to an abrupt stop, resulting in the formation of high barrier dams. In contrast, if the glacier valley runs nearly parallel to the river channel, the mass flow is able to travel further upon entering the river, thereby impacting a larger area within the river channel. The formed mass flow can traverse river channels in mountainous regions, during which geo-material gradually accumulates, leading to the formation of barrier dams. Barrier dams can break suddenly, leading to breaching floods that significantly extend the downstream impact, ranging from several kilometers to potentially hundreds of kilometers. Among the regions at risk, the Sedongpu-Ganglang reach faces the greatest vulnerability to river damming and subsequent breaching floods. Downstream areas along the Yarlung Tsangpo-Brahmaputra River are comparatively less likely to experience greater threats from these events than those posed by local monsoon floods. These findings serve as a valuable basis for developing strategies to manage glacier hazard chains, contributing to better disaster preparedness and risk mitigation in affected regions.
How to cite: Jiang, R., Zhang, L., Lu, W., Xiao, S., and He, X.: Risk Assessment of the Lower Reaches of the Yarlung Tsangpo-Brahmaputra River Exposed to Glacier Landslide Risk Chains, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11276, https://doi.org/10.5194/egusphere-egu25-11276, 2025.
The initiation and growth of debris flows is an important activity in many settings, including steep mountains, volcano flanks, and recently burned landscapes. Flow volume from growth exerts a fundamental control on behavior – larger volumes typically lead to faster flows, longer runout, more inundation, and greater hazard. Many processes can promote growth, including hillslope-based processes, such as landsliding or soil rilling, and/or stream channel-based processes such as bed entrainment or stream-bank collapse. Explicitly incorporating and parameterizing these diverse processes in physics-based models is an ongoing challenge to assess hazard and minimize risk.
As an alternative to computationally intensive physics-based models, we developed a USGS software package, called Grfin Tools (an acronym for growth + flow + inundation), that includes tools to define a drainage network, compute volumetric growth from various sources, and then delineate debris-flow inundation throughout a DEM. Grfin Tools uses empirical volume-area relations, derived from observed debris-flow events worldwide, with simple geometric rules to delimit debris-flow inundation. Integrated growth factors, applied over upslope source area and/or upstream channel-length, are used to calculate flow volumes along defined growth zones in the drainage network. Additionally, realistic inundation is created where flows traverse unconfined topography. Grfin Tools requires minimal parameters and places an emphasis on regional geomorphic and topographic controls rather than specific material properties.
Grfin Tools can define-flow inundation with varied modes of growth; we apply these tools to three settings with different growth processes: (1) mountain drainages with distributed landsliding, (2) lahars from volcano flanks that travel from the edifice, and (3) surface-runoff generated debris flows in post-fire landscapes. With upslope distributed landslides as debris-flow sources, nonlinear growth with increasing basin size can reduce potential inundation effects. For lahars from volcanoes, growth from channel sediment entrainment can lead to both wider and longer downstream inundation zones. Finally, with post-fire debris flows, growth from surface-runoff mobilization of available sediment in steep upper watersheds can enlarge flows and inundate fans downstream of mountain fronts. These examples demonstrate the ability of Grfin Tools to delineate debris-flow growth and inundation in diverse geomorphic settings.
How to cite: Reid, M., Cronkite-Ratcliff, C., Brien, D., and Perkins, J.: Analyzing debris-flow growth in diverse geomorphic settings with Grfin Tools, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7501, https://doi.org/10.5194/egusphere-egu25-7501, 2025.
The accuracy of numerical simulations for debris flows is critically dependent on the precision of terrain morphology data, regardless of the mechanical model employed. However, digital elevation models (DEMs) derived from satellite imagery and unmanned aerial vehicle (UAV) photogrammetry often exhibit limitations in mountainous regions, particularly in areas characterized by narrow channels and significant elevation differences. Additionally, air- and space-based DEMs are often insufficient for capturing channel bed information in locations where the view is obstructed by vegetation or sidewalls. This challenge is especially pronounced for channelized debris flows, where channel morphology significantly influences the flow dynamics. To address this bottleneck, we developed a ground-based channel morphology detection system utilizing simultaneous localization and mapping (SLAM) technology. The advanced SLAM-based channel detection and mapping system (AscDAMs) enables the acquisition of accurate, high-resolution channel morphology data, including channel DEMs and typical cross-sections (TCS). In this study, we applied the AscDAMs system to the debris flow event that occurred on June 26, 2023, in Banzi Gully, Wenchuan County, Sichuan Province, China. By comparing DEMs derived from satellite imagery, UAV photogrammetry, and AscDAMs, we found that the AscDAMs-based DEM exhibited superior resolution, capturing finer-scale morphological details and achieving higher accuracy. Furthermore, numerical simulations using different DEMs were conducted and compared with event video data. Results demonstrated that the simulated flow field generated from the AscDAMs-based DEM showed the highest consistency with the flow field observed in the video. These improved simulation outcomes provide deeper insights into the dynamic processes of debris flow events and contribute to more effective risk management of such hazards.
How to cite: Wang, T., Lu, F., and Shen, P.: Lidar-aided Channelized Debris Flow Numerical Modelling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7892, https://doi.org/10.5194/egusphere-egu25-7892, 2025.
Landslides, debris flows, hyperconcentrated flows, and floods are among the most dangerous natural hazards worldwide. One of the fundamental tasks for geomorphologists is to classify and identify the kinds of processes they observe in the field. The task is more challenging than it sounds, especially considering high-damage processes like debris flows and landslides. Meanwhile, multiple dimensionless numbers (e.g., Reynolds number and Einstein number) based on first-principle physics have been widely used to describe these natural flows. When we use these dimensionless numbers and datasets to classify the flow, we face a long-standing challenge in machine learning: the curse of dimensionality. One of the expertise for quantum machine learning methods (e.g., Quantum Support Vector Machine, QSVM) is to deal with such a high-dimensional dataset. Therefore, based on Quantum machine learning methods, we develop a framework to objectively define the type of natural flows using the dimensionless number. Our preliminary results show that the QSVM method has very similar outputs compared to classical SVM, but it is relatively slower than classical ones. Meanwhile, for the high-dimensional k-mean cluster, the Quantum K-mean model has shown different clusters compared to the classical version. In the future, we will develop a hybrid version combining classical K-mean with Quantum acceleration to understand different flow types.
How to cite: Tang, H.: When Geomorphology Meets Quantum Computing: a Quantum Machine Learning Model for Extreme Flows Classification , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11521, https://doi.org/10.5194/egusphere-egu25-11521, 2025.
Debris flows are a common natural trigger of mountain disasters, and gravity-type check dams are one of the most representative soil and water conservation measures in the Bailong River basin. Despite the prevalence of gravity-type check dams, scholarly research on calculating deposition thickness for each debris flow event intercepted under future precipitation scenarios is lacking, hindering accurate predictions of dredging or expansion timing. This study developed a prediction formula for deposition thickness behind the check dam. The formula is applicable to debris flow events that the dams can intercept. By analyzing the mathematical relationships among slope ratio before and after deposition, channel width, distance to the check dam, and peak discharge, the thicknesses of debris flow depositions at certain positions can be calculated, offering a new approach for predicting check dam siltation times. The newly proposed prediction formula was used to calculate the deposition thicknesses behind the dam for five debris flow events, and was applied to channels with similar Melton Indices where check dams are constructed. The deposition processes of the five debris flow events were simulated using Massflow software. Additionally, machine learning methods were employed to predict precipitation scenarios and debris flow I-D threshold curves, thereby determining the rainfall likely to trigger debris flows in catchments. Results showed that, with a duration of 900 seconds, the peak flood discharges of the five debris flow events were 40.83%–43.23%, 18.56%–22.99%, 17.89%–18.69%, 9.00%–12.10%, and 15.85%–21.06% of a 100-year return period, respectively. The study also demonstrated that the new method can be widely applied to calculate deposition thicknesses behind dams accommodating different debris flow events, aiding in optimizing check dam management and maintenance strategies and enhancing their efficiency and sustainability in water and soil conservation.
How to cite: Wei, Z., Zeng, R., and Wang, X.: Predicting Debris Flow Check Dams Siltation Times Considering Climate Change: A Case Study of the Bailong River Basin (Gansu Section), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14695, https://doi.org/10.5194/egusphere-egu25-14695, 2025.
Debris flows are massively erosive mass movements that pose an increasing threat to infrastructure and settlements in mountainous areas due to more intense heavy rainfall events in the future. A major contributor to the magnitude for runoff generated debris flow is the parameter of effective erosion. It directly translates to the hazard potential of debris flows, but it is yet to be sufficiently implemented in models to achieve a predictive performance.
We developed a simple predictive erosive debris-flow model calibrated on active channels in the northern Bavarian Alps. The debris-flows at the study sites recently occurred in 2015 and in 2021, and all entrained more than 80% of their final volume from the sediment channel bed. Geomorphic change was calculated from pre- and post-event LiDAR data and the total volume of the flow was then compared to catchment characteristics. For a detailed analysis we divided the channel into equal segments and compared the respective eroded volume to flow parameters of the adjacent cross section which were simulated in a numerical model. The initiation volume was estimated by a runoff calculation from the respective heavy precipitation events recorded with radar data. We were able to obtain a correlation that can be used in a predictive debris-flow model to iteratively calculate the erosion for runoff-generated debris flows that are triggered by intense rainstorms. This model allows improved predictions of the magnitude of debris-flow prone channels through a forward-modelling approach.
How to cite: Stammberger, V., Boie, K., and Krautblatter, M.: Erosive power of debris flows: predictive modelling by a simple empirical approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16175, https://doi.org/10.5194/egusphere-egu25-16175, 2025.
Gravitational mass movements, such as debris and mud flows, are among the most destructive natural hazards, leading to substantial fatalities and extensive economic damage worldwide. Improving our understanding and modeling of these processes is essential for developing effective risk management and early warning strategies. When debris and mud flows pass through a curved channel, centrifugal forces may cause a difference in flow height between the inner and outer banks of the channel. This height difference, known as superelevation, can be described using analytical models that establish a relationship between the superelevation height and the flow velocity.
Analytical models often employ a forced vortex approach, incorporating parameters such as the cross-sectional slope of the flow surface, flow width, and bend radius. These models, however, rely on assumptions such as a linear flow surface between mud deposits on the banks, a rectangular cross-section, and neglect both complex rheological behaviors and solid-fluid interactions. As a result, an empirically determined correction factor is required within the formula. The absence of a clear mechanical rationale for this correction factor presents challenges, as it is currently derived only through field investigations and laboratory experiments.
This study presents an enhancement to the existing forced vortex approach by incorporating insights from numerical modeling. A coupled SPH-DEM numerical model is employed, where DEM particles represent coarse solid particles, and SPH accounts for the fluid phase, comprising fines and water. The SPH-DEM coupling is based on the no-slip interaction model, with simulations performed using a GPU-based solver to ensure enhanced computational efficiency. To validate the approach, a parametric test is conducted, initially back-calculating laboratory-scale experiments. The study further involves varying the water content in debris and mud flows to examine its impact on flow behavior and superelevation. Larger water contents lead to an increased superelevation angle. Results from the parametric test reveal a clear correlation between water content and the flow surface shape in curved channels. Specifically, mud flows are characterized by convex upward surface shapes, whereas more granular debris flows typically exhibit concave downward shapes.
The distribution of material within the cross-section of the flow is governed by the equilibrium between boundary forces and centrifugal forces acting on the flow, which directly influences the superelevation. Numerical investigations are conducted to determine a correction factor and assess the extent to which inertial effects contribute to this correction factor for different material mixtures. Furthermore, we demonstrate that the effect of the flow surface shape is significant and is currently only accounted for by the empirical correction factor. This study offers new physical insights for the back-calculation of debris flow velocities in curved sections marked by mud deposits. Large-scale SPH-DEM simulations of a real debris flow event at Illgraben (Switzerland) are performed, showing good agreement with field data and its potential for further real-scale modeling.
How to cite: Friess, P., Vicari, H., McArdell, B., Åberg, A., and Gaume, J.: SPH-DEM Modeling of Debris and Mud Flows, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16696, https://doi.org/10.5194/egusphere-egu25-16696, 2025.
We propose a novel physically-based multi-phase thermo-mechanical model for rock-ice avalanches. It (i) considers rock, ice and fluid; and (ii) includes the mechanism of ice-melting and a dynamically changing general temperature equation for the avalanching mass, the first of its kind. It explains advection-diffusion of heat including heat exchange across the rock-ice avalanche body, basal heat conduction, production and loss of heat due to frictional shearing and changing temperature, a general formulation of the ice-melting rate and enhancement of temperature due to basal entrainment. The temperature equation includes a coupled dynamics, considering the rates of change of thermal conductivity and temperature. Ice melt intensity determines these rates as mixture conductivity evolves, characterizing distinctive thermo-mechanical processes. Fast ice melting results in substantial change in temperature. We formally derive the melting efficiency-dependent general fluid production rate. The model includes internal mass and momentum exchanges between the phases and mass and momentum productions due to entrainment. The latter significantly changes the state of temperature; yet, the former exclusively characterizes the rock-ice avalanche. Temperature changes are rapid when heat entrainment across the avalanche boundary is substantial. The new model offers the first-ever complete dynamical solution for simulating rock-ice avalanche with changing temperature. We construct simple and exact analytical solutions for the temperature evolution of propagating rock-ice masses with ice-melting. This offers a fundamentally novel understanding of the complex process of rock-ice avalanche, flashing the deep insights into the underlying dynamics. Finally, we present the first multi-phase thermo-mechanical simulation of the 2021 Chamoli rock-ice avalanche event with the comprehensive simulation tool r.avaflow, https://www.avaflow.org.
How to cite: Pudasaini, S. P. and Mergili, M.: A multi-phase thermo-mechanical model for rock-ice avalanche and its application to the 2021 Chamoli event, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7301, https://doi.org/10.5194/egusphere-egu25-7301, 2025.
Erosion and entrainment are dominant mechanical processes in debris flows that can amplify the flow volume by several orders of magnitude, enhance mobility, significantly increase impact forces and expand the inundation area. Reliable simulations that include erosion processes are thus critical for hazard assessment. However, existing computational debris flow models do not correctly account for the erosion-induced net momentum production. Instead, they utilize empirical approaches to erosion that rely on data from past events for calibration, often resulting in parameters that vary widely and sometimes assume unrealistic values. We have implemented the mechanical model presented in Pudasaini and Krautblatter (2021), which explains erosion-induced mass flow mobility based on erosion velocity, mechanically described erosion rate, and flow inertia, into the open source, multi-phase computational tool r.avaflow, that we extended for use in both field and laboratory conditions. To verify the correct implementation of the mechanical erosion model into r.avaflow, we are using data from large-scale laboratory flume experiments with an erodible bed and varying material composition, bed morphology and flow conditions. Here, we present simulation results from an erosive laboratory setting and the highly erosive field event “Bauhof-torrent”, Königssee (Bavaria, Germany), using the newly expanded r.avaflow, which now includes erosion-induced net momentum production. The results show that the model correctly captures the characteristic effects of erosive mass transport, such as enhanced flow mobility and energetically nonlinear volume bulking, leading to amplified surges, increased flow height, longer flow durations, and much wider inundation areas. Additionally, important phenomena such as phase separation with a solid-rich front and fluid-dominated tail, as well as different deposition speeds of the frictional solid phase and the viscous fluid phase, are observed.
How to cite: Boie, K., Krautblatter, M., Baselt, I., Wetterauer, K., and Pudasaini, S. P.: Simulating debris flow mobility with erosion in r.avaflow using a mechanical model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17110, https://doi.org/10.5194/egusphere-egu25-17110, 2025.
The generation of post-fire debris flows has been shown to significantly differ from that of non-fire related debris flows, particularly in terms of erosion patterns and response to rainfall, necessitating further research on the complete hazard generation process. To explore this phenomenon, a post-fire debris flow event at Ren’e Yong gully in China was analyzed using simulations conducted with OpenLisem. This approach enabled the consideration of multiple factors within the simulation, including rainfall interception, soil infiltration, surface runoff, erosion, channel incision, bank slope erosion, and subsequent landslides. The results showed as follows: i)Overland flow initiated more rapidly and intensely in burned areas compared to unburned ones, and it also diminishes more quickly as rainfall decreases; ii)Surface erosion increases with the severity of the burn, leading to greater channel erosion in areas with larger burned extents; iii)The erosion phase of post-fire debris flow can be categorized into four stages: initial rainfall splattering, surface erosion and channel initiation, enhanced channel erosion during the debris flow process, and channel bank slides. This simulation successfully replicates the entire process of post-fire debris flow generation, demonstrating how increased surface runoff and erosion in burned areas contribute to the formation of debris flows.
How to cite: Wang, Y., Hu, X., Tie, Y., and He, K.: Simulation of the entire generation process of post-fire debris flows at Ren’e Yong gully in China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14158, https://doi.org/10.5194/egusphere-egu25-14158, 2025.
The study of the rheological behavior of sediment suspensions is one of the most important tools for understanding the fundamental physical processes that occur between the interaction of particles and the homogeneous fluid. As lahars are natural flows that occur along the slopes of volcanoes and consist of large blocks of sediment supported by a matrix of fine sediment suspended in water, their behavior can be studied from their rheological characterization. Most of the stresses are distributed mainly within the fine matrix, due to its abundance in the flow and its capacity to support the large blocks.
This work proposes an appropriate measurement protocol for the rheological characterization of fine sediment suspensions of volcanic origin (also known as lahar matrix) from a small-scale concentric cylinder geometry, which achieves the necessary physical conditions to establish a laminar and steady flow within a homogeneous suspension and without a slippage phenomenon. This protocol was carried out using an M702e Anton Paar rheometer. The proposed protocol consisted of a staircase function testing a measurement range between and with a homogenization step between each measurement step.
Different measurement times were tested according to the maximum sediment settling time in a virtual sample column of homogeneous particle suspension. The settling time was calculated from the shape-dependent drag formula of Dioguardi et al. (2018), which includes a wide range of fluid dynamics regimes and not only perfectly spherical sediments.
The apparent viscosity curves obtained from this protocol show its dependence on shear rate, exhibiting an inverse exponential relationship with increasing shear rate. A Herschel-Bulkley type behavior is proposed as a preliminary rheological model.
How to cite: Tranquilino Espinoza, C. G., Dioguardi, F., Dellino, P., Gentile, L., Caballero, L., Sarocchi, D., and Lacalamita, M.: Measurement protocol proposal for the rheological characterization of volcanic sediment suspensions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-564, https://doi.org/10.5194/egusphere-egu25-564, 2025.
Martian gullies are alcove-channel-fan systems that are undistinguishable from debris-flow systems on Earth. Therefore, they have long been hypothesized to be formed by the action of liquid water and brines. However, over the past decade, growing evidence of widespread, extensive, and particularly, seasonal activity in these gully systems, has shifted the formation hypothesis of these landforms away from water-driven processes. The correlation between the spatial and temporal distribution of CO2 frost on the Martian surface and the formation of new lobes, the movement of meter-scale boulders, and the cutting of new channels has led to a new hypothesis: debris flows on Mars are driven by the seasonal sublimation of dry ice (CO2 ice). However, the lack of direct observations of these flows hinders our understanding of the exact conditions that lead to these granular flows, their dynamics, and erosional capacity, which hinders our understanding of the formation of these gullies over the last five million years.
Over the last three years, we have conducted three experimental campaigns in two environmental chambers (at the Open University, UK, and Aarhus University, Denmark) with different flume set-ups at varying scales to explore the feasibility of the CO2-driven granular flow hypothesis. We have quantified the CO2-driven granular flow dynamics under Martian atmospheric conditions, the physical limits under which these flows can occur, and have determined their erosional capacity. From these results, we conclude that CO2-driven granular flows can occur on Mars under specific environmental conditions and that the sublimation of very small amounts of CO2 ice (<0.5% of the flow volume) fluidizes sediment by creating high pore pressures. These high gas pore pressures decrease intergranular friction and make the granular mixture extremely mobile. Although seemingly similar, this process can not directly be compared to increased pore pressure in water-driven debris flows due to the other dynamical effects of the sublimating ice, for example, the grain movement in the flow. The high gas pore pressures under Martian conditions stem from the large CO2 gas flux created under the thin Martian atmosphere (~8e-3 bar), which is ~100 times larger than it is under Earth's atmosphere (~1 bar).
Furthermore, based on dimensionless analysis (Bagnold, Savage and friction numbers) we show that the dynamics of these CO2-driven granular flows are similar to terrestrial water-driven debris flows and pyroclastic density currents. In addition, we prove that CO2-driven granular flows are effective erosive agents, likely more efficient than terrestrial water-driven debris flows.
Combined, these results show that we do not have to evoke a water-driven origin for the Martian gullies as we can explain their formation by CO2-driven granular processes alone. This has implications for our understanding of the Martian climate, surface conditions and surface processes during the last five million years. Furthermore, these “alien” debris flows allow us to test ideas on terrestrial granular flows outside the confines of our own planet.
How to cite: Roelofs, L., Conway, S., Sylvest, M., Patel, M., Merrison, J., Iversen, J. J., McElwaine, J., Kleinhans, M., and de Haas, T.: Present-day debris flows on Mars are driven by the sublimation of dry ice (CO2), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1643, https://doi.org/10.5194/egusphere-egu25-1643, 2025.
Debris flow—plant interactions are ubiquitous, yet we have limited understanding of how plants affect debris-flow erosion. Ignoring the effects of plants in debris-flow studies potentially leads to mistakes in hazard assessments. While debris-flow erosion has been the focus of recent studies, the influence of plant roots on this process has not yet been explored. Therefore, we unravel plant rooting effects on debris-flow bed erosion, using scaled experiments. We show how fast-growing Sorghum bicolor (Sudan grass) seedlings enable scale experiments with plant-debris flow interactions. Our experiments reveal a strong, non-linear correlation between root length density and debris-flow bed erosion. Increasing root length density amplifies root-soil contact, enhancing soil stability and reducing erosion. In turn, the reduced erosion could prevent potentially hazardous debris-flow volume growth. Our results yield insights into the potential effects of changes in vegetation characteristics on debris-flow erosion and open up possibilities for biogeomorphic scale experiments for slope processes.
How to cite: van den Broek, A., Mennes, D., Kleinhans, M., Roelofs, L., Eichel, J., Draebing, D., and de Haas, T.: Impacts of Plant Roots on Debris-Flow Bed Erosion in Laboratory Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2707, https://doi.org/10.5194/egusphere-egu25-2707, 2025.
Flow-type landslides are rapid, fluid-like movements of soil or debris down a slope, posing significant risks to infrastructure and safety. It consists of grains with various grain size distribution, ranging from millimeters to meters. Recent advancements in seismic sensing have proven to be valuable for characterizing flow-type landslides. Existing physical seismic impact models link flow-type landslides to seismic signatures, thereby enhancing the measurement and inversion of the landslides. However, most models rely on prior knowledge of grain size distribution, and also the application of effective diameter can overlook some information of the grain size distribution. This oversight leads to inaccuracies both within the models themselves and the inversions of grain size distribution derived from these models.
Integrating experimental methods with analytical theory, our study aims to elucidate the relationship between grain size distribution and the seismic signatures generated by grain-bed impacts, refining the seismic impact model considering grain size distribution. A newly developed free-fall experimental apparatus has been employed to conduct both single-grain and dual-grain falling tests as unit tests. Building upon the findings from unit tests, we carried out multi-grain experiments with varying grain size distributions. The frequency components and power spectral density of the seismic data can effectively differentiate between different grain size distributions. A new grain size distribution parameter has been proposed. Combing the experimental results, we utilized the elastic impact model to analyze the seismic signatures of individual grains. Additionally, the superposition method was investigated to account for the spatial and temporal variations of grain impacts, thereby revealing the seismic response associated with different grain size distributions. Ultimately, we propose a modified seismic impact model that incorporates grain size distribution for flow-type landslides. This study provides significant insights for practitioners by leveraging seismic signals to elucidate the characteristics of flow-type landslides.
How to cite: Wang, Y. and Choi, C. E.: Investigation of seismic signature induced by grain-bed impact considering the grain size distribution of flow-type landslides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7630, https://doi.org/10.5194/egusphere-egu25-7630, 2025.
Erosion can tremendously amplify the volume and destructive potential of mass flows with spectacularly increased mobility. However, the mechanism and consequences of erosion and entrainment of such flows are still not well understood as these processes are inherently complex due to the composition of the flow as well as the erodible bed material and their physical properties. Erosion rate, erosion velocity, and momentum production are the key factors essentially controlling all the processes associated with erosive mass transport. Here, we present experimental results on the dynamics of impact-induced mobility of erosive mass flows. Experiments are conducted at the Laboratory Nepnova – Innovation Flows in Kathmandu using some native Nepalese food grains as well as geological granular materials. As we focus on erosion in the inclined channel, transition and the run-out zone, we determine how the flow and the bed conditions control the erosion rate, erosion velocity, and the momentum production. This includes the change in volume, composition, and physical properties of the released mass and the erodible bed and its slope. We establish some quantitative functional relationships among the erosion rate, the erosion velocity, and the mobility of the mass transport aiming at providing a foundation for developing predictive models and innovative strategies for erosion control and mitigation from landslide hazard.
How to cite: Dangol, B. R., Tiwari, C. N., Kattel, P., Kafle, J., and Pudasaini, S. P.: The dynamics of impact-induced erosive mass flow mobility, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11569, https://doi.org/10.5194/egusphere-egu25-11569, 2025.
As the consequences of global climate change become increasingly apparent, the ability to create accurate landslide runout analyses has become critical. These analyses can provide estimates of the potential volume and reach of future landslides and may be used to inform hazard awareness, risk management, and the design of mitigation and emergency response measures. A key uncertainty within landslide hazard assessment relates to the behaviour and possible entrainment of the sediment it travels over, which may affect the distal reach and volume of the slide. In this study we explore the extreme case of a highspeed landslide overriding loose saturated valley floor sediments vulnerable to static liquefaction; in particular, how static liquefaction progresses through the bed when the sediments are overridden and how the depth of liquefiable sediment available affects whether and how liquefaction occurs.
A static liquefaction hazard may be posed when a loose saturated layer of sand is located at the base of a landslide-prone slope so that a contractive soil is both fully saturated and in reach of a shear trigger (i.e., the landslide). This scenario was reproduced in the Queen’s landslide flume using horizontal liquefiable beds of saturated fine sand 2 m in width, 4 m in length, and at various thicknesses, located at the bottom of the inclined portion of the flume. Landslides of 700 kg of saturated granular material were then released from the top of a 6.5 m long slope inclined at 30 degrees to impact the beds at speeds of up to 6 m/s. Behaviour of the sand beds upon impact was captured using ultrahigh speed imaging of the landslide and bed profiles, a Blickfeld LiDAR sensor positioned opposite to the landslide to capture point cloud scans of the slide, and a linear array of porewater pressure sensors within the sand bed. Experiments comparing different liquefiable bed thicknesses to height of slide ratios will be presented as we explore the effect of bed depth on liquefaction susceptibility, extent of liquefaction, and the rate of excess porewater pressure generation, dissipation, and deformation within the sand bed during impact.
How to cite: Waring, A. and Take, A.: Exploring the effect of bed thickness on liquefaction of sediments overridden by landslides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13324, https://doi.org/10.5194/egusphere-egu25-13324, 2025.
Flume experiments have been widely used in many studies to investigate various characteristics of debris flows. However, some researchers have raised concerns about the adequacy of these experiments in simulating natural debris flows, as the majority do not account for entrainment and similarity. This study aimed to replicate debris flows that are dynamically similar to natural debris flows through flume experiments incorporating entrainment, and to analyze their flow characteristics. A 3.2-meter-long erodible bed composed of gravel was installed in the flume, and debris flows were generated by continuously supplying water at a constant discharge. The flow characteristics, including flow depth, flow velocity, and volumetric sediment concentration, were measured under varying flume slopes and water discharge conditions. The results showed that flow depth and volumetric sediment concentration exhibited an upward trend with increasing flume slope gradient under constant discharge conditions. Conversely, flow velocity exhibited a tendency to increase with higher discharge under the same slope conditions. The dynamic similarity of the flume experiments was evaluated using various dimensionless parameters, including the Froude number and the Bagnold number. These evaluations indicated that the flume experiments closely replicated the stony-type debris flows observed in nature.
How to cite: Jeong, J., Eu, S., Kim, T., and Im, S.: Hydraulic Characteristics and Similarity of Debris Flows under the Erodible Bed Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16052, https://doi.org/10.5194/egusphere-egu25-16052, 2025.
Geophysical flows, such as debris flows, debris avalanches, pyroclastic density currents, etc., represent one of the main sources of natural hazards. Some of these can be classified as dry granular flows, i.e., gravity-driven mixtures of discrete grains that are prevalent in a wide range of volcanological scenarios (e.g. pyroclastic density currents, block and ash flows, debris avalanches, etc.). These flows are characterized by a high degree of polydispersity in terms of grain size and density, which in turn affects the flow properties. Specifically, the presence of fine particles modifies the flow structure by segregating downwards forming a fine-rich basal layer, which controls basal dissipation. Here, the role of fine grains within granular flows is investigated on the mobility of granular flows through large-scale laboratory experiments, in which dry, initially-homogeneous granular mixtures are released vertically onto a sloped channel. In this presentation, we show the preliminary results of this experimental campaign with an emphasis on the effect of fine particles in polydisperse mixtures and its interaction with the basal roughness on the flow runout. We reveal how important it is to consider fine particles in granular flows, and look ahead to the future prospects of this study.
How to cite: Dioguardi, F., Neglia, F., Sarocchi, D., Rodríguez Sedano, L. A., Segura Cisneros, O., Montenegro Rios, A., Bougouin, A., Sulpizio, R., and Dellino, P.: Insights on the role of fine particles on the mobility of geophysical flows from large-scale experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16616, https://doi.org/10.5194/egusphere-egu25-16616, 2025.
Due to the unpredictable nature of debris flows, it is difficult to systematically establish a long-term debris-flow observation dataset. Since the 1960s, the Dongchuan Debris Flow Observation and Research Station (DDFORS) at Jiangjia Ravine was established. Field observation and research on the initiation, transportation, and accumulation of debris flow have been carried out, and a debris-flow database has been established. These sixty years of observations provide a solid foundation for exploring the dynamics and mechanisms of debris flows. Based on the observation data of debris flows, the sources of flow resistance during the natural debris-flow process were investigated. A visco-collisional resistance model was developed. The model indicates that, for surge flows, fluid viscous effects play a more significant role than solid particle interactions. However, for continuous flows, inertial collisions between particles dominate over fluid viscous effects. In addition, based on simple hydraulic jump equations, the eroded deposition depth of surge flows is quantified. For surge flows with erosion-deposition propagation, significant downward erosion potential is confirmed. The total momentum of surge flow not only originates from the apparent surge front, but also includes the momentum within the eroded deposition layer. The revealed erosion pattern and hidden momentum in debris-flow surges may improve the reliability of debris-flow risk assessment. This long-term field observation dataset will be open to the public by early 2025.
How to cite: Song, D., Wei, L., Zhong, W., and Li, X.: Long-term field observation dataset and key findings of the dynamic characteristics of debris flows in Jiangjia Ravine, China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-128, https://doi.org/10.5194/egusphere-egu25-128, 2025.
Chile faces high vulnerability to mountain hazards along the Andean Cordillera. As climate change and urban development intensify, the frequency and impact of destructive debris flows are anticipated to rise. To inform mitigation and adaptation strategies, it is imperative to understand the characteristics of historical events in this region. A notable example is the Parraguirre rock avalanche that occurred on November 29, 1987, which transformed into a catastrophic debris flow, travelling 50 kilometers down-valley and causing severe damage and loss of human lives. The high destructive power is attributed to the considerable amount of water involved. Yet, the source of this water remains largely unidentified - so is the initial trigger volume and the total mass transfer down the valley.
In this study, we revisit the past event by integrating new insights from remote sensing, climate and hydrological records as well as process-based modelling. Our results suggest important corrections. We find a trigger volume of 17.0±1.4·106 m³ and a total fluid flood volume of 16.0·106 m³. The solid mass transfer from the Parraguirre catchment amounts to 38.1±15.2·106 m³. Moreover, we find that the elevated water content cannot be solely attributed to the entrainment of soil moisture and snow cover. It requires a considerable contribution from another source - likely in form of glacier ice. Furthermore, our simulations corroborate the damming hypothesis of Río Colorado, thereby reconciling the observations of multiple waves as well as on arrival times and run-out distance.
Apart from the geological and tectonic preconditions, we propose to classify the Parraguirre rock avalanche as a meteorological compound event. This classification is motivated by the exceptionally high snowpack observed in the spring of 1987, which preconditioned elevated snowmelt rates during a series of unusually warm days at the end of November. Such preconditioning factors are readily accountable in monitoring efforts and early-warning systems for such mountain hazards.
How to cite: Fürst, J. J., Farías-Barahona, D., Bruckner, T., Scaff, L., Mergili, M., Montserrat, S., and Peña, H.: Reassessing the 1987 Parraguirre Ice-Rock Avalanche in the Semi-Arid Andes of Chile, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9159, https://doi.org/10.5194/egusphere-egu25-9159, 2025.
Debris flows are extremely rapid, flow-like landslides composed of fine and coarser-grained components, boulders, woody debris as well as water. They are characterized by large impact forces as well as long runout distances and are one of the most dangerous types of mass movements in mountainous regions. In the past, researchers have mainly measured the velocity of the front or of distinct surges. However, the spatio-temporal distribution throughout a cross-section remains largely unknown. Quantifying the horizontal and vertical velocity profiles is required for hazard assessment, the design of mitigation structures, process understanding and numerical model development.
In the present work, we analyze two debris-flow events that occurred at the Gadria creek (South Tyrol, Italy) in 2023 and 2024. We measure the horizontal as well as vertical velocity profiles for selected phases of the flows and explore how they vary in time. For the horizontal measurements, we use timelapse point clouds from a high-resolution, high-frequency 3D LiDAR scanner (Ouster OS1). We process these 3D point clouds to obtain 2D hillshade images of the moving flow, which we then analyze using Particle Image Velocimetry (PIV). This approach provides a timeseries of dense velocity vector fields of the moving surface, which we then evaluate at a defined channel cross-section to obtain horizontal velocity profiles. In order to derive the vertical velocity profiles, we use a fin-shaped barrier located in the middle of the channel, which is equipped with paired conductivity sensors at different depths along the side-wall. By applying cross-correlation to the paired conductivity signals, we can extract the vertical velocity distribution at the wall. We validated our methods by comparing the velocities to measurements of feature velocities, including boulders or pieces of woody debris, which we tracked manually and/or using a fine-tuned off-the-shelf neural-network-based object detection algorithm (YOLO v8).
For the surface velocity along the barrier, we find good agreement between the different measurement approaches. Over the duration of both events, we observe substantial variations in the shape of the profiles with different degrees of internal deformation: the horizontal profiles vary between parabolic and more plug-flow-like shapes whereas the vertical profiles feature convex to concave shapes.
Our findings highlight the non-uniform and highly variable distribution of debris-flow velocities in a cross-section with important implications for practical applications and process understanding, as for example for discharge and volume estimates. Eventually, the developed methods will be applied to additional events at the Gadria creek, which should allow for further inference into the constitutive flow behavior of debris flows to improve our understanding of these destructive events in the future.
How to cite: Spielmann, R., Ender, M., Nagl, G., Kaitna, R., Hübl, J., Schmid, P., Hirschberg, J., and Aaron, J.: Insights into debris-flow dynamics through vertical and horizontal velocity profile measurements at the Gadria creek, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9187, https://doi.org/10.5194/egusphere-egu25-9187, 2025.
On August 28, 2023, an exceptionally large debris flow occurred in the Rauris Valley, Salzburg, Austria, inundating most of the valley floor, transferring large quantities of sediment to the river system, and causing damage to local infrastructure. As the source area is located in the glacial and paraglacial environment and comparable events of such magnitude seem to have become more frequent in recent years due to changing climate conditions, this contribution investigates the meteorological and geomorphological initiation conditions and documents the flow and deposition behavior of the debris-flow event at Pilatuskar. We analyzed high-resolution radar-based precipitation records together with local rainfall and temperature data to assess the magnitude and the return period of the rainfall event. The sediment budget was quantified from differential digital elevation models derived from UAV photogrammetry drone flights immediately before (25.08.2023) and after (04.09.2023) the event. The sediment source area was investigated using electrical resistivity tomography and ground penetrating radar to evaluate ground ice occurrence and derive sediment thickness. Geomorphologic features such as levées, lobes and plateaus were manually mapped and samples taken for sedimentological and rheological analysis. Video recordings, seismic records and reports of eye witnesses were used to constrain the dynamics, sequence and time-line of deposition. The event mobilized around 680,000 m³ of sediment in the proglacial area of the Pilatuskees glacier eroding up to 15 m deep into the main discharge channel and about 570,000 m³ were deposited in the valley floor. The triggering precipitation of 145 mm had a duration of 32 hours, a maximum hourly intensity of 21 mm/h, a return period of about 10 years, and was associated with a snow line above 3200 m. The source area is composed of proglacial sediments with a mean thickness of 10 m. Resistivity measurements one year after the event revealed unfrozen conditions in the immediate surroundings of the head scarp, but thick ground ice occurrence covered by coarse supraglacial debris within a distance of 100 m. The sediment-transfer processes lasted about 3 hours and comprised periods of fluvial sediment transport, debris flood, and debris flow. The debris-flow event consisted of a sequence of 4-5 granular surges that deposited material at different locations on the fan due to avulsion. Pebble counts yielded a median grain size ranging between 0.1 and 0.45 m, and a maximum grain size between 0.34 and 1.5 m. The fine fraction consisted of sandy gravel, with only limited clay content. The results of this study shall contribute to the documentation of the geomorphological activity within high-alpine catchments that rapidly respond to changing climate conditions. Future work will focus on monitoring debris flow activity from the newly formed erosion scar at Pilatuskar as a basis for debris-flow simulation model development and testing.
How to cite: Kaitna, R., Hörmann, L., Hartmeyer, I., Keuschnig, M., Binder, D., Moser, M., Nagl, G., and Otto, J.-C.: High magnitude debris-flow event from a proglacial environment, Lachegggraben/Pilatuskar, Austria, 2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10941, https://doi.org/10.5194/egusphere-egu25-10941, 2025.
Debris flows represent one of the most prevalent and impactful natural hazards in mountainous areas, posing significant risks to both human life and infrastructure. Alpe di Succiso (2017 m a.s.l.) located in Northern Apennines, Italy, is an area where numerous occurrences of debris flows have been identified in this area encompassed by a National Park, thus densely traversed by touristic routes and infrastructures. Understanding the spatial and temporal patterns of these debris flows is critical for assessing the hazard and managing the associated safety risks for mountaineers, hikers, tourists, and, more generally, for the communities and infrastructure in the area.
This research integrates field observations of debris flows, dendrochronological analysis, geomorphological mapping (Rashid et al., 2024), and satellite imagery to reconstruct the history of debris flow events and is partially comprised in the DECC project (2023). A key focus is the 1987 debris flow, triggered by an intense rainfall event on August 25, which recorded 179 mm of rainfall in a single day, including 133 mm within a 6-hour period.
This study investigates the dynamics of debris flows, through channel-specific analysis, GIS-based zonation, and statistical evaluation. Slope angle and elevation data were analyzed to delineate source, transport, and deposition zones across four channels of debris flows. Channel 1 was identified as a debris flood channel, while Channels 2, 3, and 4 exhibited typical debris flow characteristics.
To account for the wide variation in grain sizes in the study area (0.0005 mm to 5 meters), four techniques were employed. Sieve analysis was used for grains between 2 mm and 32 mm, while laser granulometry measured finer particles below 2 mm. Direct field measurement was applied to intermediate grains (32 mm to 1000 mm), and particle counting was used for large particles above 1 meter. This multi-method approach ensured accurate representation of sedimentary material across the broad grain size spectrum.
Geomorphological analysis indicates that rockfalls and rock weathering significantly contribute to the material on the slopes. During debris flow events, these deposits are triggered at the first stage like debris/rock slide and then as flow creating channels and deposits. A geological survey of rock outcrops feeding these debris flow channels revealed that the Rock Quality Designation (RQD) ranges from 44 to 65 (poor to fair quality), while the Rock Mass Rating (RMR) falls between 45 and 56 (fair quality).
Using the RAMMS Debris Flow software (RAMMS, 2017), a scenario-based modeling approach was employed to better understand the interactions between debris flow and material constituting the slope deposits. Simulation results are currently being compared with the geometry of levees and lobes to refine the model and ensure accuracy. This comprehensive approach aims to improve the understanding of debris flow dynamics and the influence of rockfalls, thereby aiding hazard assessment and management.
How to cite: Rashid, M. A., Leonelli, G., Valentino, R., Francese, R., Chelli, A., Melada, J., Manara, V., Maugeri, M., Pescio, S., Petrella, E., Trombino, L., Masseroli, A., Arcuri, B., and Brunetti, M.: Analyzing debris flow and rockfall interactions: A case study in surrounding of Alpe di Succiso, Northern Apennines (Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10946, https://doi.org/10.5194/egusphere-egu25-10946, 2025.
Recently the methods for building rainfall threshold were proposed based on the physical process aims to predict the debris flood occurrences. However, due to uncertainties in rainfall and water & soil supply processes in mountainous regions, significant uncertainty remains in the forecasting. This study evaluates the error propagation mechanisms of rainfall patterns, hydrological process, and soil mobilization under specific rainfall constraints using a typical small watershed in the Wenchuan earthquake area as a case study. By setting parameters for rainfall, models, and initial soil conditions based on critical conditions derived from actual monitoring, we observe an amplifying trend in errors throughout the threshold establishment process. From rainfall to water flow, after transforming rainfall patterns and selecting runoff model parameters, the maximum positive error is 0.10, while the maximum negative error is -0.18. Incorporating the uncertainty of D50 into soil mobilization increases the maximum positive error to 1.16 and expands the maximum negative error to -0.43. Considering the uncertainty in the proportion of soil mobilization within the catchment during the threshold building process, the maximum positive error further increases to 1.72, while the maximum negative error rises to -0.48. It is evident that errors introduced by rainfall patterns and runoff model parameters are relatively minor compared to those caused by the uncertainty of D50. Based on these findings, a probabilistic forecasting model is proposed, providing a scientific basis for debris flow forecasts.
Key words: Debris flood, runoff yield, soil mobilization, critical thresholds, probabilistic forecasting.
How to cite: Guo, X. and Zhang, S.: Uncertainty and error propagation in the channelized debris flood forecasting, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18775, https://doi.org/10.5194/egusphere-egu25-18775, 2025.
Convective precipitation in mountainous zones often induces downstream effects, such as increased river turbidity, debris flows, and flooding, which can result in infrastructure damage, casualties, and even fatalities. Observing these events in the Andes is particularly challenging because of the lack of surface observations in the highlands, and sometimes, they are not even captured by meteorological stations. Nevertheless, debris flows are observed by the small communities of mountain inhabitants. In this research, we analyze a convective precipitation event induced by a cut-off low that triggered several debris flows in the upper Huasco River basin at the subtropical Andes (~28°S) during April 2024 (austral fall). We follow the typical hydrologic approach, extrapolating low elevation measurements from the Chilean water and meteorological agencies, comparing the estimation of freezing level with in-situ low-cost temperature sensors, and MODIS images sensing for snow detection. In addition, we perform a convection-permitting simulation through the Weather Research and Forecasting model (WRF), to reproduce rainfall in locations where debris flows occur. Our results show that the available pluviometers did not observe significant precipitation, except in some areas with intensities of up to 7 mm/hr and total precipitation of 64 mm at 1370 m a.s.l., as well as intensities of up to 2 mm/hour and total precipitation of 10 mm at 467 m a.s.l. during two to three days of the event. The temperature sensors indicate a high freezing level decreasing from 4000 m a.s.l, to 3000 m a.s.l. within the first day. The WRF simulations revealed, in the 4 km resolution domain, that total precipitation exceeds 100 mm, surpassing the highest observed records. Our findings demonstrate the importance of having observational data in mountain zones and the key role that may play in convection-permitting simulations in complex and ungauged terrain.
How to cite: Lagos-Zuñiga, M., Paredes, M., Matus, F., Pinto, D., Garcés, A., and Montserrat, S.: Meteorological assessment of a mountainous convective precipitation event triggering debris flows in the subtropical Andes. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19392, https://doi.org/10.5194/egusphere-egu25-19392, 2025.
Landslide is the most dangerous geohazards in the world and have the greatest impact on the bio-environment. In the process of landslide evolution, the evolution of the slip zone plays a controlling role in the formation of landslide, and the formation of the slip zone often has the characteristics of progressive failure. In order to elucidate the evolution of minerals and elements in the water-affected slip zone and their influence on the physical and mechanical properties of the slip zone, the sliding characteristics and formation process of the Shanyang landslide under the action of the slip zone were obtained through field investigation, laboratory experiments and numerical simulation. Firstly, the long-term evolution and mineral migration evolution characteristics of the slip zone under the action of water were studied by obtaining soil samples at different positions of the landslide slip zone, and secondly, the strength characteristics of the soil in the slip zone under saturated and natural water content were analyzed by ring shear experiments, and the influence of shear rate on the shear strength of the slip zone was studied, and the formation of the slip zone and the instability process of the landslide were analyzed by creep experiments. The study of its evolution in the water-affected landslide is of good guiding significance for understanding the formation process of the landslide.
How to cite: Zhuang, J.: The failure characters of fine-grained sliding zone due to water , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2636, https://doi.org/10.5194/egusphere-egu25-2636, 2025.
Machine learning techniques have been extensively applied to identify debris flow events in seismic signals and develop debris-flow early warning systems. However, several challenges persist. Traditional models find it difficult to directly process the raw waveform signals and instead rely heavily on manual feature extraction, which may result in redundant or insufficient features, potentially resulting in unreasonable generalization bias. Meanwhile, deep learning approaches, particularly those based on convolutional neural networks (CNNs), require multilayer stacking for dimensionality reduction. This may cause overfitting. To address these challenges, this research introduces an enhanced model based on the Transformer architecture: the Patch Fourier Transformer (PFT).
The Patch attention mechanism allows the model to focus on key regions of the seismic waveform, highlighting areas of significant energy fluctuations that correspond to debris flow events. Utilizing the Patch attention mechanism, our model effectively captures energy fluctuations in the time-frequency domain and exhibits a high level of consistency with the spatio-temporal distribution of attention weights. By mapping the attention distribution to specific time-frequency regions, the model provides insight into the seismic signal components that most influence its decision-making process.
The model was evaluated using seismic data from 12 debris flow events in the Illgraben, a Swiss catchment. The PFT model achieved over 96% accuracy in waveform identification. Furthermore, the early warning system provided warning times ranging from 24 minutes to 2 hours without generating any false alarms. These results highlight the considerable potential and advantages of the PFT model for debris flow identification and early warning applications.
How to cite: Liu, Y., Li, S., Tang, H., Zhou, Q., Ouyang, C., Xu, Q., and Zhang, B.: Debris Flow Early Warning Using the Patch Fourier Transformer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11523, https://doi.org/10.5194/egusphere-egu25-11523, 2025.
Debris flow is one of the most common geological disasters in Vietnam, occurring in mountainous areas and causing catastrophic impacts on both the economy and human lives. This article shows the results of a debris flow simulation that took place on August 5, 2023, in Trong La village, Ho Bon commune, Mu Cang Chai district, Yen Bai province, through an empirical model called LAHARZ and digital elevation model (DEM). The debris flow also was assessed for damage to the built-up area. The LAHARZ model is based on empirical equations which were derived from historical debris flood statistics. The equations include A = 0.05 V^(2⁄3) and B = 200 V^(2⁄3), in which A is the cross-sectional area, B is the planimetric area, and V is the volume. This study uses drone images and digital elevation model with 0.5m spatial resolution, which were created on August 12, 2023 by using Phantom 3 Professional drone. The debris flow's source area is roughly 78104 m2, corresponding to a volume of 8000–10000 m3. For this reason, the LAHARZ model is simulated with volumes of 5000; 8000; 10000; 15000 and 20000 m3. LAHARZ simulation results were validated by comparing them to field survey evidence. The result shows that the model results are quite similar to the actual inundated area with TPR and TS values being 0.717 and 65.9%, respectively. This study also demonstrates that the false irregular edges in the delineated inundation zones supposedly originated because of a lack of DEM accuracy. The LAHARZ model simulation has many advantages in terms of time and the few parameters used, which enable rapid evaluation of debris flow scenarios.
Keywords: Debris flow, LAHARZ, Ho Bon, Mu Cang Chai
How to cite: Tran, T.: Identification of inundated area by debris flow using LAHARZ model - A case study in Ho Bon, Mu Cang Chai, Yen Bai, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2336, https://doi.org/10.5194/egusphere-egu25-2336, 2025.
Landslides and debris flows occurring in reservoir watersheds can generate tsunami-like waves by inflowing into the reservoir. When such disasters occur during periods of high-water levels, such as the flood season, overtopping due to waves is inevitable. Analyzing such events is essential since they could lead to a dam break, which is particularly significant for Earth-fill dams, where overtopping alone greatly increases the risk of failure. Although several studies have attempted to address these phenomena through numerical modeling, there remains a lack of research that adequately considers the erosion and entrainment processes, which critically influence debris flow dynamics and the amplitude of debris flow-induced waves. In response, this study developed Deb2L, a two-dimensional two-layer numerical model based on shallow-water equations discretized using the finite volume method, capable of considering erosion, entrainment, and deposition processes. The performance of Deb2L was validated using theoretical and laboratory experiment results, demonstrating a quantitative accuracy with an R2 value greater than 0.85 and an RMSE of less than 0.10 m. Its applicability to field-scale events was confirmed by simulating the 2020 Sanyang Reservoir event in Icheon, South Korea. Additionally, to verify the applicability of scenario analysis, the simulation results from the landslide analysis model TiVaSS were used as input data for Deb2L, confirming the potential for coupling these models. According to the results, simulations without erosion and entrainment processes led to an underestimation of the debris flow-induced wave complex disaster.
How to cite: Lee, S., An, H., Kang, T., and Kim, M.: Development and application of a two-dimensional numerical model for debris flow-induced impulsive wave considering debris flow erosion-entrainment process, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3915, https://doi.org/10.5194/egusphere-egu25-3915, 2025.
This study presents a comprehensive risk assessment associated
with debris flows in the Quebrada Rosayoc, located in the district of
San Rafael, province of Ambo, Huánuco region, Peru. Debris flows,
characterized by their high velocity and mobility, pose a significant
threat to the population and infrastructure in the area. Therefore,
this study seeks to conduct a quantitative risk assessments (QRA)
to accurately estimate potential damage to structures and associated
economic losses. To achieve this objective, historical records of
events were collected based on the selected observation years. Additionally,
topographic, climatic, geological, and socioeconomic data
were integrated with fieldwork, laboratory testing, and numerical
modeling to simulate debris flows and assess building vulnerability.
One of the most significant contributions of this work is the
introduction of the debris-flow intensity index (DFI) as a metric to
evaluate the physical impact on buildings. This index not only provides
a measure of the physical impact that debris flows can have
on buildings, but also allows for the classification of damage into
four categories, ranging from minor damage to total destruction of
structures. Finally, the generated risk map, which integrates hazard
levels, impact intensities and vulnerability, constitutes a fundamental
tool for urban planning and emergency preparedness, facilitating
informed decision-making and the implementation of effective mitigation
measures.
How to cite: Santiago, E. M., Hürlimann, M., and Medina, V.: Debris-flow risk and impact on buildings: A case study of Rosayoc-Batán, Peru, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4973, https://doi.org/10.5194/egusphere-egu25-4973, 2025.
Debris flows represent a profound natural hazard, exerting devastating impacts on infrastructure, ecosystems, and human lives. During their downstream progression, debris flows transport a diverse range of materials, including soil, rocks, and vegetation, a phenomenon termed sediment entrainment. This entrainment process is governed by a complex interplay of geomorphological features, hydrological conditions, triggering factors, physical properties, and geological characteristics. Traditional predictive methods, which predominantly rely on empirical data and physically-based models, have shown limitations in capturing the variability and intricacy of environmental conditions. This study seeks to develop a sophisticated predictive model for debris flow sediment transport rates by leveraging advanced artificial intelligence (AI) techniques. The AI-driven approach enables efficient processing of extensive datasets and the recognition of nonlinear and intricate patterns, providing more rapid and precise predictions compared to conventional methodologies. The research framework comprises five distinct stages. First, critical factors influencing sediment transport rates were systematically identified and collected. Second, a comprehensive database was constructed, incorporating detailed data from 54 debris flow sites across South Korea. Third, data preprocessing was conducted, including correlation analysis and multicollinearity diagnostics to refine variable selection, followed by feature scaling and data augmentation utilizing generative AI techniques to enhance dataset robustness. Fourth, the dataset was partitioned into training and validation subsets, and various machine learning regression algorithms were employed to identify the optimal predictive model. Finally, the proposed model was empirically validated using a case study of the 2023 large-scale debris flow disaster in Yecheon County, Gyeongsangbuk-do, South Korea. The findings underscore the remarkable predictive precision and adaptability of the AI-based model, surpassing the performance of traditional physically-based approaches. This advancement holds significant potential for enhancing debris flow risk management and proactive mitigation strategies. Moreover, the study underscores the transformative role of AI technologies in addressing the challenges of predicting and managing complex natural hazards, offering a robust foundation for diverse applications in hazard mitigation and disaster resilience
How to cite: Song, C.-H., Kim, Y.-T., Nguyen, H.-H.-D., Kim, M.-J., and Lee, J.-S.: Development and Empirical Application of a Debris Flow Entrainment Rate Prediction Model Utilizing Generative AI, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5281, https://doi.org/10.5194/egusphere-egu25-5281, 2025.
Critical rainfall conditions initiating torrential processes like sediment-laden floods and debris flows in steep headwater catchments represent a multifaceted problem in Alpine communities, necessitating comprehensive adaptation and mitigation strategies to safeguard both society and the environment. Understanding the relationship between rainfall drivers and event occurrence is needed for a mechanistic understanding of the initiation process and therefore represents an important basis for developing adequate risk management strategies in a changing climate.
In this study, we investigate rainfall patterns triggering debris flows, debris floods, fluvial sediment transport and floods based on hourly rainfall time series derived from combined radar-rain gauge data for more than 3,600 torrent events in the Austrian Alps between 2003 and 2022. We consider time periods spanning seven days prior to event occurrence as well as the event day itself. These time series are clustered using longitudinal k-means on the cumulative rainfall sums over the whole time period leading up to the event.
Results reveal different archetypical precipitation patterns. While all of the patterns exhibit some rainfall on the event day, differences emerge with respect to antecedent precipitation. Major patterns include an archetype featuring stepwise increases, several patterns with breakpoints followed by an increase, and patterns characterized mainly by differences in their slope, i.e., overall rainfall magnitude. These patterns are largely consistent across all considered process types. A first analysis of the spatial distribution of patterns indicates that some patterns occur mainly south of the main Alpine ridge while others occur all over the Eastern Alps. The results of this study will help improving early warning systems and guiding model development for the initiation of mass flow processes.
How to cite: Schlögl, M., Hrachowitz, M., and Kaitna, R.: Unveiling critical rainfall patterns triggering torrential processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5772, https://doi.org/10.5194/egusphere-egu25-5772, 2025.
The purpose of this study is to investigate the occurrence of debris flows, including their locations, volumes, and flow in regions. The field surveys were conducted in regions using a drone and a numerical analysis was performed with the RAMMS model to simulate debris flow behavior. The results of this study were compared with the actual debris flows. As a result of comparing the detailed map (Case A) and the actual debris flow occurrence status after the debris flow in the Docheon-ri basin in the model verification, it was confirmed that the spread area and movement distance were simulated to be the same, confirming the applicability of the model. As a result of simulating the digital map (Case B) before the occurrence of debris flow under the same conditions and comparing it with the actual debris flow occurrence status, the flow direction and spread shape of the debris flow were simulated to be similar except for the area that occurred beyond the basin. It was confirmed that simulation was possible. It is believed that it can be used as basic data for damage prevention, such as estimating the extent of damage from debris flow disasters, selecting on-site investigation points for expected debris flow damage, and evacuating residents within the debris flow damage area when heavy rain is expected.
Keywords: debris flow, heavy rain, RAMMS, survey, damage.
How to cite: Lee, H., Kim, S., and Chang, H.: Analysis of debris flow mitigation at ungauged watershed, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5897, https://doi.org/10.5194/egusphere-egu25-5897, 2025.
Debris flows, like most gravitational flows, exhibit an extremely diverse flow behavior depending on the relative composition of the mixture. For debris flows, the interaction between the fluid and the solid components as well as the interaction of the solids with each other is of decisive importance for the bulk flow behavior. Combined information of bulk flow properties, material composition and internal deformation is needed to constrain constitutive relations for debris flows.
This study focuses on the measurement velocity profiles in natural debris flows observed at a monitoring station at the Gadria creek in South Tyrol, Italy and to relate these with measurements of grain size distribution, flow depth, basal stress measurements and horizontal velocity distributions. Velocity profiles are measured along the sidewall of a concrete structure in the middle of the channel at 11 levels above the channel bed using pairs of conductivity sensors with a certain horizontal spacing s. Cross-correlating the signals yields a time delay t that allows calculating the velocity v.
The main focus of the first stage of the project BEHAVE is to identify the optimal way to process the conductivity signals for the subsequent continuous velocity determination, as the processing parameters have a major influence on the resulting velocity profiles. In an initial assessment, we find that the step size of the floating window plays tendentiously a more important role for the quantitative velocity value generation than the value size of the floating window (= maximum lag). In contrast, the quality of the velocity values is decisively influenced by the setting of an optimal auto-correlation factor (ACF) value threshold, which indicates the significance of the individual correlations. We finally compare the velocity distributions from selected time periods of two debris flow events with each other.
These results will form the basis for further analysis, such as rheological characterizations of the collected debris flow materials, combinations with horizontal velocity profiles and the comparison with laboratory test data.
How to cite: Ender, M., Nagl, G., Huebl, J., and Kaitna, R.: Deriving vertical velocity profiles of natural debris flows at the Gadria creek, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8011, https://doi.org/10.5194/egusphere-egu25-8011, 2025.
Due to the high uncertainty surrounding extreme rainfall events and debris flow occurrence, combining probability and risk is a commonly used approach for predicting debris flows. The Chenyoulan River Watershed (CRW) in central Taiwan has experienced a major earthquake and multiple extreme rainfall events, making it a suitable area for this study. A rainfall warning model based on records of multiple debris flows and long-term rainfall data was used in this study. The model reflects the probabilistic characteristics of debris flow occurrences following earthquakes and extreme rainfall, and it has been successfully applied to predict recent debris flow events. Although the CRW experienced several severe debris flows in the past, it has not faced any major debris flow disasters for over a decade. However, in 2024, multiple debris flows were observed, many originating from the same location, with high recurrence. Fortunately, these events did not result in any injuries or fatalities. This study evaluates the model's adaptability to the rainfall events of 2024 and proposes an improved method for predicting rainfall thresholds, warning times, and risk levels for this type of debris flow. The findings offer valuable insights for future debris flow monitoring and prediction efforts.
How to cite: Chen, J.-C., Huang, W.-S., Li, F.-B., Fan, J.-Q., Lai, X.-Z., and Li, G.-L.: Rainfall Warning Model for Debris Flow Occurrence after Extreme Rainfalls: Recent Events in Chenyoulan River, Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8672, https://doi.org/10.5194/egusphere-egu25-8672, 2025.
Granular flows, such as landslides and rock avalanches, are a prevalent geological hazard in mountainous regions, necessitating accurate dynamic modeling for disaster prevention. We investigate the influence of particle composition and flow regimes on granular flow dynamics and seismic response through a series of flume experiments. By varying particle size distributions and flume inclinations, we analyzed kinematic properties, seismic signals, and the interplay between flow regimes and seismic characteristics. The results demonstrate that particle composition significantly impacts flow mobility, with an optimal proportion of large particles maximizing flow mobility. Seismic signals, including peak amplitude and power spectral density, showed a strong coupling with collisional stresses and exhibited a biphasic positive correlation with flow dynamics. We employ a unified framework based on the dimensionless amplitude parameter and the Savage number to interpret seismic responses across flow regimes. We found that frictional flows generate seismic signals through bulk impacts, while collisional flows do so via inter-particle collisions. Our study advances the understanding of granular flow dynamics and their seismic signatures, highlighting the importance of refined models to disentangle the mechanisms of frictional and collisional interactions. These findings enhance our understanding of seismic-based debris flow monitoring and hazard assessment, highlighting the need for refined models to better interpret granular flow behaviors in natural environments.
How to cite: Zhou, X., Cui, Y., Tang, H., Zhang, Z., Ye, L., and Turowski, J.: Dynamic and Seismic Characteristics of Granular Flows under Different Flow Regimes: Insights from Laboratory Flume Experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10610, https://doi.org/10.5194/egusphere-egu25-10610, 2025.
Debris flows are high speed saturated mass movements, which are controlled by gravity and shear processes. The flow matrix consists of water and granular material, ranging in size from clays to boulders. Particle diameters below 63 µm, the “fines”, are able to remain in suspension for the flow duration owing to their small settling velocities. Therefore, water and fines are often considered as a single, fluid, phase in the literature. This assumption means the fluid phase properties are governed by fines concentration and microstructure, and the fluid shear state. During propagation downslope, the debris flow matrix shears as a sequence of contractions and dilations. This process causes a reduction, or enlargement, of the voids between large grains, and allows flow of the fluid phase out of, or into, this space. The influence of increased fluid viscosity caused by fines on these processes and its impact on the macro-scale outcomes is largely under-researched. This study undertakes tests in a small-scale flume to physically model idealised debris flows with increasing viscosity. To achieve this, a uniform coarse granular material is replaced with increasing percentages of fines, a kaolinite clay. To identify the contribution of viscous properties of the fluid phase on the model, each fluid phase composition is independently tested for its rheological properties. The majority are observed to be non-Newtonian and shear-thinning in behaviour.
How to cite: Nichols, H., Leonardi, A., and Bowman, E.: Effects of fine grains in suspension on fluid viscosity and debris flow mobility , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10820, https://doi.org/10.5194/egusphere-egu25-10820, 2025.
In nature, the propagation and deposition dynamics of geophysical flows - such as debris flows, rock avalanches, and pyroclastic flows - are governed by the rheology of the flowing material itself, but also by the interaction with its environment. In particular, the interaction between the flow and the substrate plays a key role in the frictional dissipation process at the base, whereas it can vary considerably in natural situations. In fact, favorable conditions could even partly explain the high mobility of geophysical flows usually reported in relation to laboratory experiments. To tackle this question, we investigate the role of substrate roughness on the dynamics and deposition of concentrated, dry granular flows by combining small-to-large scale experiments and numerical simulations. We reveal that substrate condition can significantly affect the propagation and deposition of geophysical granular flows. Specifically, we show that the substrate type can be characterized as smooth, rough and macro-rough, based on the grain-to-roughness size ratio for a wide range of materials (i.e., glass beads, sand, volcanic materials). We then characterize the macroscopic properties of the flow in each of these configurations. Finally, this study offers guidelines for improving the modelling of geophysical granular flows.
How to cite: Bougouin, A., Dioguardi, F., Capparelli, G., Nicotra, E., and Sulpizio, R.: How does substrate roughness affect geophysical granular flows ?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11996, https://doi.org/10.5194/egusphere-egu25-11996, 2025.
In mountainous regions, debris flows represent a significant hazard, causing extensive damage and casualties each year. Among the various triggering factors, rainfall is the primary driver of debris flows in catchments with high sediment availability. Determining critical rainfall thresholds for debris-flow initiation is therefore essential for improving early warning systems and mitigating associated risks. This study focuses on:
a) Defining rainfall thresholds for debris-flow initiation using monitoring data collected over a relatively short period (three years), even in the absence of a large number of observed debris-flow events;
b) Gaining deeper insights into catchment dynamics by not only differentiating between debris-flow and no debris-flow conditions but also identifying rainfall thresholds that correspond to increased water levels and sediment transport within the stream;
c) Achieving these goals through the implementation of a monitoring station that is simple, cost-effective, and easy to install and operate.
The study area is the Blè catchment, a drainage basin covering 2.9 km², located in Val Camonica in the Central Italian Alps. Monitoring activities began in 2021, supported by funding from Regione Lombardia. The catchment is monitored through a network of seven stations distributed along the debris-flow channel. One station was installed by the University of Bologna, while the remaining six form the monitoring and early warning system developed by Hortus Srl. These stations are equipped with a variety of sensors, including rain gauges, radar-level sensors, geophones, and cameras, enabling comprehensive observation of debris-flow dynamics.
A crucial aspect in determining rainfall thresholds is the identification of individual rainfall events. In this study, we applied time windows of varying durations to separate consecutive events and analysed how rainfall thresholds change as the duration of these time windows varies. Using images from the cameras, we associated each rainfall event with the corresponding catchment response. Alongside the recorded debris-flow events (one in August 2021 and one in October 2022), we also considered events characterized by increased runoff in the stream, both without evident sediment transport and with evident sediment transport. The classical approach to defining rainfall thresholds was adopted, utilizing the duration and average intensity of rainfall in their logarithmic form. Rainfall threshold determination was performed using Linear Discriminant Analysis (LDA), a method that identifies threshold values by maximizing differences between categories of catchment responses while minimizing variability within each category. Two distinct thresholds were defined: an upper threshold for debris-flow initiation and a lower threshold to distinguish events characterized by increased runoff with sediment transport. These thresholds were determined for each of the five monitoring stations equipped with rain gauges. Additionally, we analysed how the average rainfall intensity and duration varied between rain gauges installed in close proximity within the same small catchment. Our approach revealed particularly valuable for areas with short monitoring periods and infrequent debris-flow occurrences.
How to cite: Ioriatti, E., Reguzzoni, M., Reguzzoni, E., Schimmel, A., Venturelli, M., Albertelli, L., Beretta, L., Brardinoni, F., Ceriani, M., Redaelli, M., Pilotti, M., Ranzi, R., Scotti, R., Simoni, A., Turconi, L., Luino, F., and Berti, M.: Defining rainfall thresholds for debris flows in catchments with short monitoring periods and rare debris-flow events., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12179, https://doi.org/10.5194/egusphere-egu25-12179, 2025.
We demonstrate that a numerical model based on mixture theory can capture the break-up of a flow into multiple waves formed of relatively dry granular fronts followed by more watery tails. In doing so it, it is shown that no variations in topography are necessary for the combined flow of solid and fluid phases down an inclined channel of constant gradient to break up into surge waves. The observed wave structure is consistent with field observations. The formation of small levees is also evident in our simulations. The production of levees is enhanced by the geometry of the channel. At the flow front, material is pushed towards the edges of the flow, onto the banks of the channel. The fluid phase drains down the banks back into the centre of the channel faster than the solid phase. As a result, a small amount of statically stable solid material is deposited at the edge of the flow, in the form of small levees.
How to cite: Webb, J., Meng, X., Johnson, C., and Gray, N.: Debris flow waves, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12450, https://doi.org/10.5194/egusphere-egu25-12450, 2025.
This article focuses on a gully where seven debris flow events occurred successively over a period of 24 years. The gully is located in the mountainous area of central Taiwan, with a catchment area of 55.85 hectares, an elevation ranging from 720 to 1470 m, an average slope of 80%, and forest covered 80% catchment area. From 2000 to 2023, seven debris flow events have occurred in this gully, and in response to these events, the authorities have constructed various mitigation structures in the area. In addition, 217 earthquakes of intensity 2 or greater occurred from 1995 to 2024, including three earthquakes of intensity 5 and one of intensity 7. This study aims to understand the characteristics of induced debris flow events in this gully by analyzing the rainfall data, seismic sequences, and mitigation structures.
The results of the study show that: (1) The hydrological parameters, including rainfall depth, duration and intensity, exhibited significant variation among the seven debris-flow events. For instance, the 3-hour rainfall depth varies by more than 10 times. (2) Earthquakes with intensity below 5 do not show a significant correlation with the occurrence of debris flow events in this gully, but earthquakes with intensity 7 caused a significant decrease in the occurrence threshold of debris flow; (3) In about 5 years, the decreasing of debris flow occurrence thresholds by the intensity 7 earthquake gradually returned to pre-earthquake conditions; (4) Mitigation structures have a certain degree of disaster suppression against normal rainfall. However, the suppression of debris flow disasters induced by extreme rainfall is limited.
How to cite: Wang, J.-S., Zeng, Y.-C., and Jan, C.-D.: Case study of a gully with 7 repeated debris-flow events in 24 years, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14216, https://doi.org/10.5194/egusphere-egu25-14216, 2025.
Landslide barrier structures are a useful mitigation tool for managing debris flow risks, working to slow their momentum or alter their course to avoid damage to downslope inhabitants or infrastructure. Their design is typically governed by the expected impact force, which is predicted using analytical models or numerical simulations. These methods only provide estimates of the peak force and require detailed information about the flow at impact that can be difficult to accurately predict. In this experimental study, we use the large Queen’s University Landslide Flume to explore the relative contributions of the fluid and solid phases of a multi-phase flow on the structural demand on a barrier. Impact forces following dam break experiments of up to 0.4 m3 of material, released from the top of a 6.5 m long slope inclined at 30 degrees are explored for material releases of pure water, dry granular particles (3 mm diameter), and fully saturated water-grain mixtures. Temporal impact behaviour captured using ultrahigh speed imaging (7500 fps) is correlated with the time series of impact load measured at the barrier. The addition of the fluid phase was found to significantly increase the impact force and the maximum run-up height along the barrier. Further tests are performed using single-graded particles ranging in diameter from 3-25 mm. Over this range, the dilatancy of the flow increased with increasing particle size, leading to reduced influence of the fluid phase on the flow dynamics and decreased impact force, despite similar flow velocities (4-5 m/s).
To explore the performance of an alternate barrier type, impact tests were conducted using a single-slit barrier with varying slit size (30-240 mm) and grain diameter (3-25 mm), providing a wide range of relative slit sizes. A benefit of the slit barrier design is its ability to ‘self-clean,’ letting material slowly release through the slit following an impact event. This allows the barrier to remain effective in halting a secondary debris flow without maintenance clearing between impacts. To explore the dynamics of this subsequent event, secondary releases were performed for both solid and slit barrier designs. Barrier performance is investigated using load measurement, LiDAR imaging, and PIV analysis. The solid barrier experienced overtopping under the second release. The addition of the slit alters the deposit geometry, generating two slopes on either slide of the slit which act as redirection berms, altering the flow behaviour and reducing the runup height and force of the second impact. The results of this large-scale experimental study provide detailed data on the flow behaviour, impact mechanics, and barrier efficiency for a range of debris flow compositions, particle sizes, and slit sizes under single and sequential impacts, suitable for numerical model benchmark tests that may lead to improved barrier design.
How to cite: Hirsch, E., Take, A., Mulligan, R., and Woods, J.: Exploring single and sequential debris flow impacts against solid and slit barriers, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14420, https://doi.org/10.5194/egusphere-egu25-14420, 2025.
The assessment of the degree to which a society is vulnerable to the tragedies that are caused by landslides continues to be a serious concern, particularly in areas that are prone to experiencing frequent landslides. Although there have been several studies that have addressed this topic, there has been relatively little research done on the relationship between landslides and the impact they have on buildings and infrastructure. This study focuses on assessing building vulnerability within the landslide susceptibility zones of the Champawat district in Uttarakhand. Building footprints were identified using an image segmentation algorithm powered by artificial intelligence. Landslide events were delineated based on historical and recent data from authenticated sources and field investigations on recent landslides. For this analysis, 10 Landslide Conditioning Factors were considered, including land surface temperature, rainfall, and land use/land cover, among others. The Weight of Evidence (WoE) method was applied to generate a landslide susceptibility map for the study area. The results indicate that almost 63.7% of the total buildings are located in moderate to highly susceptibility zones. The Receiver Operating Characteristic (ROC) curve was utilized in order to validate the Landslide Susceptibility Map (LSM) that was developed, and the results showed that it achieved an accuracy of ~72%. This study highlights the need for targeted risk mitigation strategies to enhance the resilience of communities in landslide-prone regions.
How to cite: Tyagi, A., Sharma, M. L., Gaur, C., and Gupta, R. K.: Landslide Susceptibility Mapping and Risk Assessment: Zoning and Building Exposure Analysis for Champawat District, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15243, https://doi.org/10.5194/egusphere-egu25-15243, 2025.
Debris flows are fast-moving, destructive mass transport processes that frequently occur in mountainous regions, posing severe threats to infrastructure and communities. Despite extensive research on debris flows, high-resolution velocity and flow depth data from full-scale natural events to test and parameterize empirical equations remain scarce. This study utilizes pulse-Doppler (PD) radar to continuously track debris-flow velocities at Illgraben, Switzerland, during the 2022 season. We analysed three debris flows and one debris flood, initially assessing four empirical mean velocity estimation equations: Newtonian Laminar Flow, Dilatant Grain Shearing, Manning-Strickler, and Chézy.
Flow resistance coefficients were back-calculated for each equation to evaluate their applicability and define their plausible value ranges. Based on these findings, we identified optimal Manning-Strickler (n = 0.16; n = 0.09) and Dilatant Grain Shearing (ξ = 25.5; ξ = 51.2) coefficients for the three debris flows and the debris flood, respectively, to estimate discharge and volume, highlighting both the strengths and limitations of these approaches. However, substantial variability in M-S and DGS coefficients—both within individual events and across different flows—challenges the conventional assumption of constant friction coefficients in debris-flow modeling.
Additionally, analysis of the relationship between flow height and velocity revealed a progressive decrease in yield stress across successive surges in two events, indicating a transition toward more fluidized flow behaviour. These findings contribute critical data for refining debris-flow models and improving predictive capabilities.
How to cite: Schöffl, T., McArdell, B., Hübl, J., Schreiber, H., Graf, C., Koschuch, R., and Kaitna, R.: Dynamic Flow Resistance in Debris Flows: High-Resolution Insights from Remote Sensing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15395, https://doi.org/10.5194/egusphere-egu25-15395, 2025.
Debris flows are destructive mixtures of water and sediments. In mountain regions, debris flows are a relevant hazard as they threaten people and infrastructure. A critical yet understudied debris-flow characteristic are surge waves, which can occur throughout a debris-flow event. These waves travel faster than the bulk flow and often determine the maximum discharge and impact pressure, with important implications for hazard assessment and mitigation. Although surge wave kinematics have been studied experimentally and theoretically, the high-quality field data needed to validate these findings are missing. Here, we leverage recently developed LiDAR sensors and cameras to monitor surge waves high spatial (<2 cm) and temporal (10 Hz) resolution in the Illgraben channel, Switzerland. We use a neural-network-based object detection algorithm (YOLOv5) to identify and track surge waves, boulders and woody debris on 2D camera images. Object tracking was performed with the SORT algorithm. By projecting the tracks onto the LiDAR point clouds, we obtain precise data such as size and velocity of individual objects including the wave crest, the fluid downstream of the wave and small features such as woody debris interacting with the surge waves. This data builds the basis to validate the latest theories of surge wave dynamics. Preliminary results show that a representation of surge kinematics which treats the wave as uniform and progressive (Davies, 1997), as a wave traveling through still water, captures the velocity trend although only based on wave height and the depth of the fluid it travels through. In future, we aim to test more complex surge wave kinematic theories, which can solve space-time evolution of the wave and particles floating on the surface (Viroulet et al., 2018), such as the woody debris we detect and track. Therefore, the unique field data and methods we present will be helpful for better understanding surge wave kinematics and develop and test numerical models.
References
Davies, T.R., 1997. Large and small debris flows—Occurrence and behaviour, in: Armanini, A., Michiue, M. (Eds.), Recent Developments on Debris Flows, Lecture Notes in Earth Sciences. Springer Berlin Heidelberg, Berlin, Heidelberg, pp. 27–45. https://doi.org/10.1007/BFb0117760
Viroulet, S., Baker, J.L., Rocha, F.M., Johnson, C.G., Kokelaar, B.P., Gray, J.M.N.T., 2018. The kinematics of bidisperse granular roll waves. J. Fluid Mech. 848, 836–875. https://doi.org/10.1017/jfm.2018.348
How to cite: Hirschberg, J. and Aaron, J.: Field validation of debris-flow surge-wave equations at Illgraben, Switzerland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15837, https://doi.org/10.5194/egusphere-egu25-15837, 2025.
To improve the timeliness and precision of debris flow early warnings in disaster-prone areas, a fully automated monitoring and warning system has been deployed in the midstream section of Yusui Stream, Taiwan. Designed to operate without manual intervention, the system serves as a localized enhancement to traditional precipitation threshold warnings. While precipitation-based alerts are effective on a regional scale, they may fail to account for localized variations in debris flow activity. This advanced system addresses these limitations, reducing unnecessary evacuations and disruptions while enhancing safety in high-risk communities.
The system achieves real-time debris flow detection by integrating two video cameras with 10X optical zoom, two geophone sensors, and a rain gauge. This setup captures both visual evidence and ground vibration signals, enabling accurate and direct confirmation of debris flow events. Upon detection, automated warnings are disseminated through multiple communication channels, including voice messages, Line Notify, public broadcasts, and web-based alerts. This multi-channel approach ensures effective notification even in critical situations.
Beyond its warning capabilities, the system offers advanced monitoring functions. The video cameras record key parameters such as debris flow front velocity and flow height, providing valuable data for emergency response and post-event analysis. Simultaneously, the geophone sensors measure phase speed and flow rate, offering deeper insights into debris flow dynamics and supporting the development of informed disaster management strategies.
The system’s reliability was demonstrated during Typhoon Gaemi on July 24, 2014, when it successfully detected multiple debris flows triggered by intense rainfall. Despite challenging weather conditions, it operated seamlessly, issuing timely warnings and capturing detailed video footage along with real-time depth variation data. These comprehensive records supported immediate relief efforts and contributed to ongoing research and preparedness for future disasters.
In conclusion, this fully automated debris flow monitoring and warning system represents a significant advancement in disaster mitigation. By providing precise, localized alerts and comprehensive monitoring data, it complements existing methods and sets a benchmark for wider adoption in regions facing similar geological or climatic hazards.
How to cite: Wei, S.-C. and Liu, K.-F.: Automated Debris Flow Monitoring and Warning System for Yusui Stream, Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16122, https://doi.org/10.5194/egusphere-egu25-16122, 2025.
To estimate the debris flow runout distance and its velocity, the geotechnical and rheological parameters of marine sediments are requested. To obtain the yield stress and viscosity as rheological properties, steady state and oscillatory shear rheology were conducted for marine sediments taken from the Ulleung Basin, East Sea. In general, marine sediments act as a yield stress fluid, such as a non-swelling materials. For the materials examined, yield stress and viscosity are sensitive to the change in volumetric concentration of sediment and salinity. In particular, at the same liquid limit, especially for the liquid limit state, the value is unique; however, when the liquidity index increases, the difference of rheological properties are large. According to the test results, the Bingham and bilinear yield stresses in controlled shear modes ranges approximately from 100 Pa to 4000 Pa. The large gap is due to the imposed shear loads: e.g. steady state and oscillatory shear loads. One of large difference is reached to the twice. Since the yield stress and viscosity affect the runout distance and peak velocity of debris flow materials, the difference create different geomorphological characteristics. For the debris flow simulation, Massmov2d is used. In this presentation, the debris flow characteristics depending on geotechnical and rheological parameters will be discussed.
How to cite: Jeong, S.-W., Lee, G.-S., Yoo, D.-G., Hong, S.-H., and Urgeles, R.: Rheology of marine sediments at the eastern margin of the Korea Peninsula and its implications for submarine debris flow mobility, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16317, https://doi.org/10.5194/egusphere-egu25-16317, 2025.
The transition area between the Tibet plateau and the Sichuan basin has a big elevation difference and sensitive environment, the new build expressway from Wenchuan to Marcon suffering debris flow before it formally running. After investigation and data analysis, the reason caused debris flow is heavy rainfall cause some landslide in the both banks of gully, investigation also found different structure of the expressway cause different result. In order to make effective mitigation for expressway, a susceptibility analysis of struck area was made, the geology environment, rainfall intensity map from TRMM and GPM data and NDVI and the loose material evaluation from remote sensing data were used in gully scale, the susceptibility model is AHP method and compared with the synthetic model proposed by Liu xilin(2002). The expressway suffering debris flow because the exposure and the facility structures, with this idea and the concept of risk given by the UNESCO, the disaster resistance were classed by 5 kind of structures, the final result show the right bank is much higher risk and some corresponding mitigation works were proposed.
How to cite: Tian, H.: Assessment of low-frequency plateau debris flow risk along expressway considering the threatened highway facility constructures, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17761, https://doi.org/10.5194/egusphere-egu25-17761, 2025.
Northern Chile is characterized by hyperarid conditions, with annual precipitation averaging < 100 mm/year, however, during the austral summer, few short-duration, high-intensity local convective rainfall, typically originated by cut-off lows, accounts for > 90% of annual precipitation. Large scale events, dominated by synoptic activity, such as those occurring in March 2015 and May 2017 in the southernmost Atacama desert, triggered debris flows in more than 100 creeks, causing significant damage to infrastructure, the local economy, and loss of human lives. However, numerous debris flow events associated with mesoscale convective systems in the Andes have also been documented despite not being recorded by low-elevation meteorological stations. Based on a debris flow inventory compiled by the National Geology and Mining Service, the characteristics of storms within a 10 km radius of each event were analyzed. Rainfall intensity-duration (ID) thresholds were identified, revealing that storms with an intensity exceeding ~7 mm/h have a high probability of triggering debris flows. The identified ID curve generally represents lower thresholds compared to global studies, attributed to the convective nature of the storms and the low density of meteorological stations. Although low, the proposed threshold is conservative and suitable given the low meteorological monitoring density in the area. The use of a convection-permitting storm simulation through the Weather Research and Forecasting model (WRF) is being explore to reproduce local scale precipitation triggering debris flows in the area.
How to cite: Pinto, D., Lagos-Zúñiga, M., Garcés, A., Paredes, M., and Montserrat, S.: Rainfall intensity-duration thresholds for debris flows in hyperarid zones with sparse meteorological monitoring., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17838, https://doi.org/10.5194/egusphere-egu25-17838, 2025.
Mountainous catchments often experience snowmelt-induced landslides and debris flows triggered by soil saturation due to intense and rapid snowmelt during spring and early summer. These events are influenced by snowpack dynamics, terrain morphology, and the hydrological processes associated with the melting process. While snowmelt-induced debris flows typically exhibit gradual initiation due to steady water input, they can mobilize large volumes of sediment (and possibly woody material), posing significant hazards to downstream areas. In spite of their impacts, these events are poorly covered in the literature. The objectives of this study are to examine the mechanisms of snowmelt-induced debris flow formation, analyze sediment transport dynamics, and evaluate downstream impacts. The landslide has affected sedimentary rocks of poor mechanical characteristics that produce abundant silty-clayey debris. The event under study occurred on June 17-18, 2024 in the Dolomites, just upstream of the Longiarù village (South Tyrol, Italy). Field observations, coupled with DoD analysis, revealed that the landslide originated in a hollow near the watershed divide and the muddy debris flow traveled a significant distance into the valley, receiving further water input from a few minor streams and entraining additional sediments along its course. Video footage recorded near the village showed a progressive decrease in flow concentration as the flowing mass moved downstream.
Based on the mobilized volume derived from the DoD, we simulated the debris flow using the single-phase flow model implemented in the r.avaflow computational tool. Field data and historical records were used to calibrate and validate the model, ensuring that the simulated results closely matched observed travel distances, deposited volumes, and impacted areas. The findings of this study contribute to a broader understanding of snowmelt-induced debris flows in mountain regions and provide insights for developing effective hazard mitigation strategies.
How to cite: Dey, L., Borga, M., Comiti, F., Mergili, M., Pierpaolo, M., Marchi, L., Cavalli, M., Crema, S., Dallan, E., and Mair, V.: Simulating snowmelt-induced muddy debris flows in alpine regions: A case study in the Seres Creek, Dolomites, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19265, https://doi.org/10.5194/egusphere-egu25-19265, 2025.
This study presents a simplified approach using the control volume finite element method (CVFEM) to model debris flow fan morphology at tributary confluences, with a specific focus on the effects of main channel flow rates and slopes. Conventional models often require extensive parameterization and computational resources to simulate such complex sediment transport processes. In contrast, our simplified model introduces an effective slope parameter to represent the influence of the main stream on the evolving fan morphology. This adjustment allows for a more efficient yet reliable simulation framework, particularly in scenarios where real-time analysis or rapid assessments are needed. To validate the model, we conducted field-based comparisons using morphological data from the confluence of the Yu-Shui River and Laonong River, a region prone to frequent debris flow events and significant sediment deposition. The model successfully reproduced essential features observed in the field, including fan elongation and narrowing in response to increased main stream flow rates. Despite its simplified structure, the model showed consistent agreement with field observations across varying hydraulic and topographic conditions, highlighting its capability to capture key morphological trends without the need for excessive computational effort. By incorporating the effective slope parameter to simulate main stream influence, this approach offers a practical and computationally efficient tool for simulating debris flow fan dynamics. The simplified model holds promise for applications in geomorphological research, sediment transport analysis, and disaster risk management, particularly in data-scarce or rapidly evolving environments.
How to cite: Shan, S.-Y., Zhong, Y.-J., and Hung, C.-Y.: A Simplified CVFEM-Based Model for Debris Flow Fan Morphology at Tributary Confluences, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18137, https://doi.org/10.5194/egusphere-egu25-18137, 2025.
Debris flow activity is expected to show a nonlinear response under different climate change scenarios. The Plansee (Tyrol, Austria) in the Northern Calcareous Alps is one of the few catchments where the strong increase in debris flow activity could be evidenced over the last 70 years (terrestrially) and 4000 years (lake sediments). The latter study (Kiefer et al. 2021) shows a 9-fold recent (since 1920) increase in debris flow volumes. The 54 alluvial fans bordering the lake are connected to heavily jointed Dolostone catchments with constant debris production and form an archive for the evolution of debris flow activity over the Holocene. By photogrammetric analysis of historical and digital aerial images starting in 1952, we capture a 7-decade period of terrestrial hillslope erosion. The volumes of debris flow-induced sediment deposition in the lake since 1952 derived from turbidite deposits match the yearly cumulative net change in the catchments calculated from Digital Surface Models derived from historical aerial images. An increase in rainfall days since the 1980s corresponds to an increase in mean erosion over all catchments. We compare the sediment yields of these catchments over the last 7 decades to find out whether varying catchment characteristics control the activity on each fan or the variation in rockfall activity and local intense precipitation over time outweighs differences between catchment morphometry. We aim to analyze (i) how the longterm increase in debris flow activity since 1920 is reflected in the short term sediment dynamics of multiple alluvial fans, (ii) whether we can observe trends or heterogeneous activity on all fans within this phase of overall enhanced activity, (iii) how the vegetation cover changed within 7 decades, (iv) which sedimentation patterns we can reveal with geophysical methods and (v) the amount of geomorphic work carried out in the catchments over the last 7 decades.
How to cite: Kiefer, C., Barbosa, N., and Krautblatter, M.: Deciphering increasing debris flow activity as a composed signal of 54 contributing catchments over the last 70 years: combined terrestrial and lake record (Plansee, AT), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18498, https://doi.org/10.5194/egusphere-egu25-18498, 2025.
Ice-rock avalanches generate unusual debris flows known for their high mobility, long runout distances, and potential hazard. Ice is thought to reduce friction and, during larger time intervals, reduce shear resistance because of increased pore pressure associated with melting. In the context of climate warming, a degrading cryosphere redistributes stresses and destabilizes slopes in high alpine regions as well as at ice-clad volcanoes. This can lead to more frequent ice-rock avalanches threatening communities downstream. Consequently, ice-rock avalanches have recently received more attention. However, most studies are based on numerical models, rotating drums, or small-scale flume experiments, which exhibit problematic scaling effects (for example, disproportional effects of pore water pressure, viscous flow resistance, and grain inertia) and thus not represent physical processes well.
We present results from the large-scale experimental USGS debris flow flume (95 m long, 2 meters wide, 1.2 m deep inclined on a 31° slope that tapers off onto a 2° runout pad towards its end) showing how ice affects debris flow mobility and initiation processes. In a series of mobility experiments, sediment-ice mixtures were placed behind a gate that was suddenly opened. In a series of initiation experiments, the flume was modified by attaching a retaining wall inside the flume, placing the sediment-ice mixture behind the wall, and watering the mixture (emulating groundwater inflow) until failure occurred. We conducted six large-scale debris flow experiments (8 m3 mixtures) with ice volume ranging from 100% to 0 %, at 20% intervals, and three initiation experiments (6.2 m3 mixtures) with volumetric ice content of 65%, 30%, and 0% ice. To isolate the effects of ice, we used sediment containing no silt and clay, which are known to enhance mobility by maintaining elevated pore pressure within the flow. The sediment-ice mixture was fully saturated at the start of each mobility experiment. Increasing ice content created a nonlinear trend of decreased mobility, in terms of runout distance and velocity, until a critical ice content was reached. As ice content increased beyond a critical value, mobility and velocity of the mixture increased and surpassed that of debris flow with no ice.
During initiation experiments, sediment-ice mixtures and sediment only (control) experiments were saturated until slope failure. Mixtures containing ice caused pore water pressures to stay elevated longer than those without ice before the failure. However, peak pore-water pressure of the sediment-ice mixtures during slope failure was lowered than that of the control (no ice) experiment and exhibited a hampered or sluggish failure.
How to cite: Obryk, M., George, D., Mirus, B., and Rengers, F.: The effects of ice on debris flow mobility and initiation processes–results from the large-scale experimental USGS debris flow flume., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13254, https://doi.org/10.5194/egusphere-egu25-13254, 2025.
Posters virtual: Mon, 28 Apr, 14:00–15:45 | vPoster spot 3
EGU25-3920 | Posters virtual | VPS12
A Deep Learning-Based CAE-LSTM Model for Enhanced Long-Term Prediction of Flood Wave PropagationMon, 28 Apr, 14:00–15:45 (CEST) | vP3.8
Predicting the dynamics of flood processes is paramount for effective disaster prevention and mitigation. Recently, Physics-Informed Neural Networks (PINNs) have been employed for flood dynamic prediction, demonstrating commendable performance in wave propagation forecasting. However, PINNs, which rely on traditional fully connected neural networks, exhibit certain limitations. Notably, their capacity for learning long-term wave propagation processes remains insufficient, and they struggle to generalize across diverse, previously untrained scenarios.In this study, we propose an innovative model that integrates a Convolutional Autoencoder (CAE) with a Long Short-Term Memory network (LSTM) to overcome these challenges. Drawing inspiration from the finite-difference method employed to solve the Shallow Water Equations (SWE), the CAE-LSTM model adeptly captures and predicts flow characteristics from both spatial and temporal dimensions. The CAE harnesses the power of convolutional neural networks to extract spatial features and generate compact latent representations, thereby reducing the complexity inherent in the physical system. Meanwhile, the LSTM captures the temporal dependencies within the latent feature space, enabling the prediction of the dynamic process based on time-series data.The efficacy of this model was validated through three classical two-dimensional dam-break scenarios. In the 60-second rolling prediction case, the accuracy of CAE-LSTM surpassed that of PINNs by approximately 60%, while its computational efficiency was enhanced by a factor of approximately 100. These results underscore the potential of CAE-LSTM to effectively capture the intricate dynamic behaviors of fluids, thereby offering a robust tool for predicting flood dynamics.
How to cite: Han, Z., Long, G., Li, C., Li, Y., Su, B., Xu, L., Wang, W., and Chen, G.: A Deep Learning-Based CAE-LSTM Model for Enhanced Long-Term Prediction of Flood Wave Propagation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3920, https://doi.org/10.5194/egusphere-egu25-3920, 2025.
EGU25-4951 | Posters virtual | VPS12
Application of Virtual Reality in Debris Flow Control Engineering PlanningMon, 28 Apr, 14:00–15:45 (CEST) | vP3.9
On 1 November 2000, an intense rainfall event triggered a catastrophic debris flow in the Dacukeng Creek region of Ruifang Township in Taiwan, resulting in seven fatalities, one missing person, and extensive damage to residential structures and farmland. This disaster underscored the critical need for integrated debris flow mitigation strategies and rigorous engineering interventions within a comprehensive regional disaster prevention framework. In response, the present study developed a multifaceted approach combining high-resolution UAV-based terrain mapping, advanced numerical modeling, and immersive virtual reality (VR) simulations to quantitatively characterize debris flow dynamics and facilitate stakeholder engagement in risk assessment and mitigation planning. First, unmanned aerial vehicles (UAVs) were utilized to capture high-precision topographic data, which were processed with ContextCapture to generate a detailed 3D photogrammetric model. Next, FLO-2D simulations were employed to approximate debris flow rheology, analyzing flow depth, velocity, and inundation extents under various rainfall intensities. The resulting data were subsequently imported into Blender to create dynamic 3D visualizations illustrating potential flow pathways and associated hazards. Finally, a VR-based debris flow mitigation platform was constructed in Unity, featuring six degrees of freedom for user movement and interactivity. This platform enables engineers, policymakers, and community stakeholders to virtually navigate realistic hazard scenarios and evaluate the efficacy and cost-effectiveness of different structural and non-structural mitigation measures. By merging cutting-edge computational modeling with immersive visualization, the proposed framework allows for enhanced comprehension of debris flow mechanisms, fosters more productive communication among diverse stakeholders, and supports evidence-based policymaking. The real-time and interactive nature of the VR environment promotes deeper public engagement, improves collaborative planning, and ultimately strengthens regional resilience against debris flow hazards.
How to cite: Tsai, Y.-F., Gao, C., Wei, H.-Y., and Yang, M.-C.: Application of Virtual Reality in Debris Flow Control Engineering Planning, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4951, https://doi.org/10.5194/egusphere-egu25-4951, 2025.
EGU25-7529 | ECS | Posters virtual | VPS12
Dynamic susceptibility assessment of glacial debris flows on the southeastern Tibetan Plateau under future climate change scenariosMon, 28 Apr, 14:00–15:45 (CEST) | vP3.10
Glacial debris flows are prevalent across the southeastern Tibetan Plateau, driven by climate change-induced glacier retreat in this region. This retreat has facilitated an increased frequency of debris flow events, underscoring the need for a comprehensive understanding of their susceptibility to enhance hazard mitigation strategies. However, significant gaps remain in integrating climate change projections and glacier retreat dynamics into susceptibility assessments. This study presents a novel method for predicting the susceptibility of glacial debris flows under future climate change scenarios on the southeastern Tibetan Plateau. The proposed approach incorporates dynamic variables into susceptibility modeling, including annual precipitation, average annual temperature, projected glacier extents, and anticipated land cover changes. The analysis utilizes combined scenarios from Representative Concentration Pathways (RCPs) and Shared Socioeconomic Pathways (SSPs), specifically SSP1-2.6, SSP2-4.5, and SSP5-8.5, to evaluate the impacts of future climate conditions. Results indicate a notable increase in the number of glacier catchments with very high annual average temperatures from SSP1-2.6 to SSP5-8.5, particularly in the eastern portion of the study area, while annual precipitation exhibits minimal change. Land cover projections for 2030 suggest a shift from shrubland to bare land, signaling land degradation. Additionally, glacier retreat is evident, with a growing number of catchments projected to have a glacier area percentage below 0.05% by 2030. The susceptibility analysis reveals an increase in glacier catchments with high and very high susceptibility from SSP1-2.6 to SSP5-8.5. Notably, the number of catchments with very high susceptibility under SSP5-8.5 exceeds that of 2010 and closely resembles 2020 levels. These findings emphasize the escalating risks posed by climate change and glacier retreat, providing critical insights for developing adaptive hazard mitigation strategies in the region.
How to cite: Zhao, F., Gong, W., Biachini, S., and Tang, Y.: Dynamic susceptibility assessment of glacial debris flows on the southeastern Tibetan Plateau under future climate change scenarios, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7529, https://doi.org/10.5194/egusphere-egu25-7529, 2025.
