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 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 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 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.

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.

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.