NH3.1 | Debris flows: advances on mechanics, monitoring, modelling and risk management
EDI
Debris flows: advances on mechanics, monitoring, modelling and risk management
Convener: Alessandro Leonardi | Co-conveners: Jacob Hirschberg, Sara Savi, Marcel Hürlimann, Xiaojun Guo
Orals
| Mon, 15 Apr, 14:00–15:45 (CEST), 16:15–18:00 (CEST)
 
Room 1.15/16
Posters on site
| Attendance Tue, 16 Apr, 10:45–12:30 (CEST) | Display Tue, 16 Apr, 08:30–12:30
 
Hall X4
Orals |
Mon, 14:00
Tue, 10:45
Debris flows are among the most dangerous natural hazards that threaten people and infrastructures in both mountainous and volcanic areas. The study of the initiation and dynamics of debris flows, along with the characterization of the associated erosion/deposition processes, is of paramount importance for hazard assessment, land-use planning, design of mitigation measures and early-warning systems. In addition, climate change may expose more mountain areas to higher hazard, and further research is needed to understand the consequences of this.

A growing number of scientists with diverse backgrounds are studying debris flows and lahars. The difficulties in measuring parameters related to their initiation and propagation have progressively prompted research into a wide variety of laboratory experiments and monitoring studies. However, there is a need of improving the quality of instrumental observations that would provide knowledge for more accurate modelling and hazard maps. Nowadays, the combination of distributed sensor networks and remote sensing techniques represents a unique opportunity to gather direct observations of debris flows to better constrain their physical properties. At the same time, computer-aided hazard assessment and mitigation design are undergoing a revolution due to the widespread adoption of AI and of data-driven numerical models.

Scientists working in the field of debris flows are invited to present their recent advancements. In addition, contributions from practitioners and decision makers are also welcome. Topics of the session include field studies and documentation, mechanics of debris-flow initiation and propagation, laboratory experiments, modelling, monitoring, impacts of climate change on debris-flow activity, hazard and risk assessment and mapping, early warning, and alarm systems.

Orals: Mon, 15 Apr | Room 1.15/16

Chairperson: Xiaojun Guo
14:00–14:05
Experiments & Processes
14:05–14:15
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EGU24-9580
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On-site presentation
Colin Ginot, Guillaume Chambon, Maxime Wallon, Paul Vigneaux, and Pierre Philippe

In a context of climate change, sediment availability and occurrence of heavy rainfall episodes are tending to increase, resulting in a likely rise in frequency and magnitude of debris flows. For effective hazard management, predicting the velocity, depth, and run-out of these flows in realistic settings, while considering all relevant processes, is crucial. In particular, as debris flows may exhibit viscoplastic characteristics, a better understanding of the interplay between inertia, rheology and topographical features is necessary. We report on well-controlled laboratory experiments of viscoplastic surges flowing down a model topography. A volume of viscoplastic fluid (Carbopol) is released onto four 3D-printed topographies featuring different patterns of mounds and ridge. Using Moiré projection, we monitor flow depth with a temporal resolution of 250 Hz, exploring a wide range of configurations involving varying volumes and fluid rheological properties. This set-up enables us to investigate the front velocity, the deviation and accumulation of fluid induced by the obstacles and the shape of the deposit. Two distinct flow regimes are observed. Initially, a rapid regime develops with a high front velocity, and the fluid spreads in both transversal and longitudinal directions. This regime is driven mainly by inertial forces. Subsequently, the front velocity drops drastically and the fluid flows mainly along the slope. In this second regime, controlled by rheological effects, the flow is strongly influenced by the topography with various mechanisms depending on the case (deceleration, accumulation, channelization, etc.). These experimental results are then systematically compared with depth-averaged numerical simulations based on shallow-water hypothesis. We compare the outcomes of two models implementing different representations of the complex rheology. The experimental data serves as a benchmark to assess the predicting capabilities of the models and evaluate the resulting uncertainties. These findings offer new insights into the physical processes driving debris flows, and they will ultimately contribute to the enhancement of simulation tools used in hazard management.

How to cite: Ginot, C., Chambon, G., Wallon, M., Vigneaux, P., and Philippe, P.: Experimental study of viscoplastic surges down complex topographies and comparisons with numerical simulations., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9580, https://doi.org/10.5194/egusphere-egu24-9580, 2024.

14:15–14:25
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EGU24-9068
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ECS
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Highlight
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On-site presentation
Oscar Polanía, Emilien Azéma, Mathieu Renouf, Nicolas Estrada, and Miguel Cabrera

Landslides and debris flows are massive geophysical processes that could occur in subaerial or submerged conditions. They involve granular materials in a wide range of Grain Size Distributions (GSD). In such processes, granular materials are subjected to large deformations, reaching a state where strains accumulate at constant shear stress. This state is known in the geotechnical community as the residual or critical state. The influence of the GSD on the residual state has been a matter of discussion between conflicting experimental and numerical observations. In this work, we confirm, at a grain scale and in dry conditions, that the residual shear strength is independent of the GSD. Moreover, we experimentally validate this result on dry granular flows, comparing the influence from monodisperse materials (materials with one grain size) to well-graded materials (materials with multiple grain sizes) on the mobility of a granular column. In this configuration, a granular column is let to collapse by self-weight and spread horizontally. The column mobility can be interpreted as a macro representation of the material's effective shear strength. Furthermore, we explore the effect of the GSD in immersed columns, finding a strong dependence of the GSD on the flow dynamics arising from the evolution of basal pore pressure P. At the flow initiation, negative P changes beneath the column produce a temporary increase in the column strength. This positive change lasts longer and with a larger amplitude in granular flows with well graded materials than in monodisperse ones. Then, during the column horizontal spreading, positive changes of P provoke a decrease in shear strength. For column collapses of graded materials, the excess of P lasts longer, allowing the collapses to reach farther distances compared with collapses of monodisperse materials. Finally, considering the relevance of mobility in granular flows, we propose a mobility model that scales the final runout with the collapse kinetic energy. This model works for both dry and immersed flows with different GSDs and has been validated for results from different authors, methodologies, and grain characteristics. Our results offer a novel perspective on the influence of GSD on the complex relationships between solid and fluid phases in granular flows, highlighting features that can be extended to massive natural processes.

How to cite: Polanía, O., Azéma, E., Renouf, M., Estrada, N., and Cabrera, M.: Grain size distributions, from a single grain size to well-graded distributions, on dry and immersed flows, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9068, https://doi.org/10.5194/egusphere-egu24-9068, 2024.

14:25–14:35
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EGU24-7750
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ECS
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On-site presentation
Caroline Friedl, Lonneke Roelofs, Joëlle Hansen-Löve, Christian Scheidl, and Tjalling de Haas

While there are field observations and studies on erosion of debris flows over loose sediment, bedrock erosion by debris flows has not yet been studied comprehensively. Nevertheless, traces of erosion in the bedrock channel after debris-flow events, such as scars, ridges, grooves or individual impacts, indicate a non-negligible entrainment of material as a result of process-related impact and shear forces. In the Alps, such erosion phenomena are often found in the upper steep and inaccessible parts of the catchment areas and are thus difficult to analyse.

In this study we therefore investigate the potential erosion capacity of debris flows of different rheological characteristics on immobile channel beds with a small-scale physical model. We try to understand how bedrock strength influences erosion and if shear or impact forces dominate bedrock erosion by debris flows. To this end, erosion rates in terms of volume and the forces causing erosion are examined in over 100 laboratory experiments. We also compare and scale these rates to natural bedrock erosion caused by debris flows.

In our small-scale laboratory investigation, polyurethane foam boards act as bedrock surrogates. This material has already been used as a bedrock simulant in studies into fluvial bedrock erosion. The boards were installed in the lower 2.5 m of the flume channel, which has a total length of 5.6 m. Different board strengths ­­– indicating different erosion susceptibility – were tested with three different debris-flow mixtures. The slope of the channel was kept constant at 34°. After each debris flow, the change in bed elevation was measured with a laser scanner to determine erosion rates at submillimeter accuracy. Laser distance sensors, pore water pressure sensors, a load cell and a geophone were used to quantify debris-flow dynamics and different erosion forces, including shear and impact.

Our results show an exponential increase in erosion with a decreasing tensile strength of the bedrock simulant. While impact and shear forces both influence erosion rates, the decisive erosion force component appears to depend on the proportion of gravel and clay in the debris-flow mixture. The results of this study serve to deepen our understanding of the debris-flow process and expand our knowledge of erosion processes in the upper reaches of debris-flow catchments. In addition, our results can be used to tune existing models for longer-term landscape evolution.

How to cite: Friedl, C., Roelofs, L., Hansen-Löve, J., Scheidl, C., and de Haas, T.: Hitting rock bottom - Experimental study of bedrock erosion by debris flows, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7750, https://doi.org/10.5194/egusphere-egu24-7750, 2024.

14:35–14:45
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EGU24-13638
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ECS
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Highlight
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On-site presentation
Alexandra Waring and Andy Take

Landslide runout analyses are conducted to predict the motion and distal reach of potential future landslides to inform landside hazard zonation, risk management, and the design of the optimal location and height of mitigation strategies such as barrier systems. A key uncertainty in these analyses relates to the erodibility and entrainment of sediment which may unexpectedly increase the volume of the landslide and affect travel distance. In this study we explore the case of a landslide overriding and entraining loose saturated valley floor sediments; in particular, whether such a scenario may cause the overridden sediments to liquefy, and if so, the extent to which that liquefaction affects the depth of erosion of the bed material and mobility of the slide.

The presence of a loose saturated layer of soil at the base of a slope inherently introduces a soil region potentially prone to static liquefaction. This scenario fulfills the criteria required for instability: a) loose contractive soil, which happens to be co-located in an area that is both b) fully saturated, and c) within reach of a shear trigger (i.e., being overridden by the landslide). This scenario was reproduced in the Queen’s landslide flume, using a horizontal liquefiable bed of saturated fine sand 2 m in width, 7 m in length, and 0.3 m in height located at the bottom of the inclined portion of the flume. Landslides of up to 1,200 kg of granular material were then released from the top of a 6.5 m long slope inclined at 30 degrees to impact the bed at speeds of up to 6 m/s. Behaviour of the sand bed 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. Preliminary results of experiments attempting to liquefy the valley floor sediments are presented as we explore the requisite conditions for different rates of entrainment, and in extreme cases, liquefaction, of the sand bed, as well as the effect of liquefaction and entrainment on the speed and volume of the slide.  

How to cite: Waring, A. and Take, A.: Exploring the entrainment of liquefied bed material in landslides, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13638, https://doi.org/10.5194/egusphere-egu24-13638, 2024.

14:45–14:55
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EGU24-10832
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ECS
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On-site presentation
Alessandro Zuccarini, Elena Ioriatti, Marco Redaelli, Luca Albertelli, Mauro Reguzzoni, Edoardo Reguzzoni, Nikhil Nedumpallile Vasu, Vanessa Banks, Elisabeth Bowman, Alessandro Leonardi, and Matteo Berti

Debris flows are extremely fast landslides whose complex dynamics are still not fully understood, primarily due to challenges in acquiring direct field measurements. In modern monitoring stations, cameras represent cost-effective data sources, providing essential information for characterising the documented events.

Digital Particle Image Velocimetry (DPIV) algorithms have been extensively employed in the literature to reconstruct velocity fields in laboratory physical models under controlled conditions. However, the resolution of field camera footage is typically suboptimal due to weather and lighting conditions, as well as non-zenithal recording geometry, hindering a straightforward application of DPIV. Landslide flume experiments, conducted in collaboration with the Civil and Structural Engineering Department of the University of Sheffield and the British Geological Survey office in Keyworth, revealed that also suboptimal quality footage can be effectively utilised provided appropriate orthorectification algorithms are applied to eliminate the original image distortions.

In this study, the methodology established through the laboratory flume experiments was applied to analyse a real debris flow event in an active catchment in the Camonica Valley (Lombardia, Italian Alps) between the municipalities of Ono San Pietro and Cerveno. The Blè Stream catchment, with a drainage area of approximately 3.5 km², a maximum elevation of 2,527 m a.s.l.,  and a main channel length of about 2.9 km, experienced a debris flow event on October 22, 2022. This was documented by several monitoring stations equipped with cameras and a flow-depth radar sensor along the main channel track.

The frame-by-frame orthorectified surface velocity field of the recorded debris flow was obtained through a DPIV analysis, employing two open-source tools in Matlab sequentially: PIVlab (Thielicke & Stamhuis 2014) and RIVeR (Patalano et al. 2017). The discharge at a specific instant along a reference section was computed as the product of the reconstructed flow velocity distribution and the area of the section defined by its topography, known from pre- and post-event LiDAR and drone surveys, and the measured flow level. Throughout this phase, careful consideration was given to assessing the primary sources of uncertainty arising from the continuously changing section geometry and the measured surface velocity, which typically overestimates the actual depth-averaged velocity, with a divergence depending on flow rheology. Calculating the discharge for each frame along the reference section ultimately yielded the hydrograph of the documented debris flow event, along with an estimate of the involved volume of material.

 

References:

Patalano A, García C, Rodriguez A, 2017. Rectification of Image Velocity Results (RIVeR): A simple and user-friendly toolbox for large scale water surface Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV). Computers and Geosciences. 109. 323-330. 10.1016/j.cageo.2017.07.009.

Thielicke W, Stamhuis EJ, 2014. PIVlab – towards user-friendly, affordable and accurate digital Particle Image Velocimetry in MATLAB. J. Open Res. Softw. 2 http://dx.doi.org/10.5334/jors.bl. 

How to cite: Zuccarini, A., Ioriatti, E., Redaelli, M., Albertelli, L., Reguzzoni, M., Reguzzoni, E., Nedumpallile Vasu, N., Banks, V., Bowman, E., Leonardi, A., and Berti, M.: Estimating the hydrograph of a debris flow event through low-cost field camera monitoring and Digital Particle Image Velocimetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10832, https://doi.org/10.5194/egusphere-egu24-10832, 2024.

Modelling & Mechanics
14:55–15:05
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EGU24-14924
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ECS
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Virtual presentation
Yu Zhuang, Brian McArdell, and Perry Bartelt

The experimental-based μ(I) rheology is now prevalent to describe the movement of gravitational mass flows. Though the μ(I) rheology has been successfully applied to the modelling of historical debris flows and rock avalanches, its physical implication is not fully understood. In this study, we re-formulate the μ(I) rheology as a Voellmy-type relationship, which is composed of a Coulomb friction term and a turbulent term. We find that different from the classic Voellmy rheology (ξ is a constant), the turbulent coefficient ξ in the μ(I) rheology is heavily dependent on the avalanche height and velocity, indicating the shear-thinning features. However, as μ(I) rheology is a pure function of velocity (for a constant height), the friction exhibits no change during the acceleration and deceleration stage. With this purpose, we introduce a newly proposed μ(R) rheology that relates the friction to the production and decay of fluctuation energy (granular temperature) R. Using one-dimensional block models, we show the equivalence of I and R, and elucidate why similar results of μ(I) and μ(R) rheologies are easily obtained. Ultimately, this comparative analysis offers valuable insights into improving geophysical flow models, enhancing our understanding of flow behavior's dependence on various factors and leading to more accurate assessments and mitigation of geophysical hazards.

How to cite: Zhuang, Y., McArdell, B., and Bartelt, P.: Comparative Analysis of Geophysical Flow Models: Voellmy, μ(I), and μ(R) Rheologies , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14924, https://doi.org/10.5194/egusphere-egu24-14924, 2024.

15:05–15:15
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EGU24-11956
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On-site presentation
Shiva P. Pudasaini and Martin Mergili

Earthflows are landslide processes characterized by the viscous movement of predominantly fine-grained and often water-saturated material down a slope or gully. They occur at a broad range of velocities, but generally do not display extremely rapid movement (such as debris flows, snow avalanches, or rock avalanches). Examples include the Gschliefgraben earthflow in the Austrian Alps and the Chirlești earthflow in the Romanian Carpathians. Although earthflows are common mass movement processes, they have not received the same attention as extremely rapid flows when it comes the development of dynamic simulation models. Here, we present a novel mechanical model and dynamical solution technique for earthflows. We develop a strategy of balancing the flux, viscous, and other forces. Our model essentially employs the flux-controller, viscosity-controller, and the deformation-controller. Within a single unified frame, we can now simulate a broad range of earthflows for different viscous, plastic, or visco-plastic behaviors and any degree of mechanically controlled deformation over a wide spectrum of time scales. We demonstrate the performance of the new earthflow model and its applicability with the advanced open-source computational mass flow simulation tool r.avaflow. Simulated earthflow deformation and motion are very smooth, typical of a hugely viscous material, as it is anticipated for earthflows as commonly observed for real-world events. As expected, the motion and deformation are exceptionally sensitive to the changes in the viscosity of the earthflow.

How to cite: Pudasaini, S. P. and Mergili, M.: A dynamic earthflow model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11956, https://doi.org/10.5194/egusphere-egu24-11956, 2024.

15:15–15:25
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EGU24-20635
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On-site presentation
Andrea Pasqua, Alessandro Leonardi, and Marina Pirulli

Debris flows are characterized by rapid movement of a mixture of water, mud, and unsorted debris along natural channels due to gravity. With propagation speeds exceeding 5 m/s and lack of premonitory signals, evacuating local populations is challenging, mitigation measures like barriers become necessary . The current difficulties in designing barriers regard the simplified methods employed that overlook event variability, hindering optimal structural design.

In this study, continuum numerical models, specifically depth-averaged (DA) and three-dimensional (3D) models, are employed to investigate debris flows. DA models depth-average Navier-Stokes equations, reducing the number of variables, allowing for efficient analyses of entire mountain valleys in a short timeframe. However, due to depth-averaging, essential details of vertical momentum transfer are missing, crucial for studying flow-structure interaction (FSI). By contrast, 3D models faithfully replicate FSI but are computationally demanding, making their application challenging for valley-scale flow propagation studies.

The study proposes a novel approach by coupling DA and 3D models to comprehensively investigate a flow propagating in a mountain valley and impinging against barriers. This approach combines the efficiency of DA models with the precision of 3D models, without neglecting upstream flow evolution. The DA model is employed when the flow is far from barriers, and a coupling section is placed upstream of a barrier, with the DA results as input for the 3D model to study the FSI.

The DA-3D coupled model is validated through replicating a laboratory experiment and a real-world event, with the same rheological law in DA and 3D frameworks for consistency.

A laboratory experiment with glass beads in a flume was replicated. Using µ(I) rheology, the study initially compared 3D results with the original experiment. Subsequently, the DA-3D model, employing µ(I) rheology, replicated the experiment. Striking similarity were found in DA-3D results when compared with 3D and experimental results. Additionally, forces on the barrier were compared between the 3D and DA-3D models, affirming results consistency and effectiveness of the DA-3D model.

In the site-scale investigation of an event occurred in St. Vincent (Aosta Valley, Italy), the study focused on a filter barrier installed to mitigate the risk associate to debris flows in the area. Field data are available because  the barrier was monitored to evaluate forces.  In this scenario, the DA-3D model was utilised, avoiding the the µ(I) rheology due to calibration challenges and because it was formulated for dry flows. Instead, the study opted for Voellmy rheology, extensively used in DA frameworks and specifically adapted for the 3D framework. The examination of debris flow impact on the barrier involved a comparison of field data with numerical values. The findings highlighted the realistic representation of FSI and forces by the DA-3D model at the site scale, emphasizing its potential for the comprehensive study of debris flows.

Acknowledgments

This study was carried out within the RETURN Extended Partnership and received funding from the

142 European Union Next-GenerationEU (National Recovery and Resilience Plan – NRRP, Mission 4,

143 Component 2, Investment 1.3 – D.D. 1243 2/8/2022, PE0000005) – SPOKE VS 2.

How to cite: Pasqua, A., Leonardi, A., and Pirulli, M.: The impact of debris flow on mitigation structures: a novel depth-averaged and three-dimensional coupled model for the flow dynamic simulation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20635, https://doi.org/10.5194/egusphere-egu24-20635, 2024.

15:25–15:35
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EGU24-9914
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ECS
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Highlight
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On-site presentation
Zhengyang Su, Shun Wang, and Dianqing Li

Corresponding author: Shun Wang       E-mail: shun.wang@whu.edu.cn

Abstract: Overtopping failure of landslide dams is a complex process that involves strong soil-water coupling and structural failure. Physically based numerical models are needed for breach mechanism as well as failure process and flood prediction. In this study, we establish an SPH-DEM dam-break model that considers the combined effect of seepage and overflow. The key feature of the proposed high-fidelity dam-break model is that both solid and fluid phases are solved simultaneously in two different sets of Lagrangian particles using their own governing equations. In the numerical framework, the water phase is modeled as weakly-compressible Newtonian fluid using the SPH method, and the soil phase is modeled using the DEM method. The interactions between these two phases including drag force, buoyancy and adhesion. The capillary force generated by the meniscus between two soil particles is solved to characterize the saturated and unsaturated processes of soil. The model is validated by three benchmarks including the simulations of seepage through an earth dam, a small-scale dam-break test and the whole progress of dam profile erosion. In a small-scale dam break test, the calculation error of overtopping peak flow is 3.5%. Simulation results predicted by the SPH-DEM dam-break model show good agreements with the finite element method and experimental results. Furthermore, the high-fidelity dam-break model is able to simulate many other soil-water coupling processes, such as reservoir water infiltration, dam slope erosion and collapse, breach development, and dam failure. In the future, the proposed SPH-DEM soil-water coupling framework could be applied to the modeling of geohazard chain triggered by rainfall-induced landslides, blocking river and dam outburst flood.

Keywords: landslide dam; overtopping modeling; SPH-DEM; soil-water coupling

How to cite: Su, Z., Wang, S., and Li, D.: High-fidelity modeling of landslide dam overtopping failure using SPH-DEM method , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9914, https://doi.org/10.5194/egusphere-egu24-9914, 2024.

15:35–15:45
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EGU24-1051
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ECS
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On-site presentation
James Christie and Georgie Bennett

Lahars are a common and potentially long-lived hazard in river basins affected by explosive volcanic eruptions. They result from the hydrological disturbance of surrounding landscapes, driven by the destruction of vegetation and deposition of pyroclastic material. These modifications typically result in heightened rainfall runoff responses, via reduced interception and infiltration, leading to increased water and sediment flux, manifesting as lahars. With time, landscapes recover via removal of sediment, establishment and stabilisation of channels, and the redevelopment of vegetation. This recovery subsequently reduces the runoff response to rainfall and in turn limits the potential magnitude and frequency of lahars. Numerical modelling is an important approach for assessing the hazard posed by lahars. Most modelling approaches related to lahars consider the remobilisation susceptibility of pyroclastic deposits under particular conditions, or the runout/inundation potential of individual or probabilistic ensembles of flows. To date, very limited research has sought to address the longer-term (years to decade) evolution of lahar activity in affected catchments as they respond to and recover from disturbance. Here we present and discuss SedCas_Volcano, a simple model designed to simulate the longer-term evolution of lahar incidence in a catchment on the island of Montserrat that has been repeatedly disturbed by episodic volcanic activity since 1995. Using this simple and computationally inexpensive numerical framework, we account for variability in sediment supply, vegetation cover, and rainfall. Here we will discuss the merits of this model and identify possible next steps for continued model development.

How to cite: Christie, J. and Bennett, G.: SedCas_Volcano: a novel approach to modelling decadal evolution of lahar hazard in response to episodic volcanic eruptions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1051, https://doi.org/10.5194/egusphere-egu24-1051, 2024.

Coffee break
Chairperson: Marcel Hürlimann
16:15–16:20
Geomorphology & Susceptibility
16:20–16:30
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EGU24-13891
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ECS
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On-site presentation
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Ping Shen, Tengfei Wang, Fucheng Lu, and Hui Kong

Enhancing the study of channelized debris flow necessitates precise and high-resolution mapping of channel topography and deposit conditions. Existing mapping technologies like satellite imaging and drone photogrammetry face challenges in accurately observing the interiors of extensive mountainous gullies, particularly in regions affected by events like the Wenchuan Earthquake. Despite the emergence of Simultaneous Localization and Mapping (SLAM) as a 3D mapping technology, its efficacy is hampered in rugged gullies due to two primary challenges: (1) Unusual terrain features and (2) Severe sensor swaying and oscillation, causing significant deviations and noise in SLAM-generated results. Addressing these challenges, we propose an innovative SLAM-based debris-flow channel detection and mapping system. It incorporates three key enhancements to refine SLAM outcomes: (1) A deviation correction algorithm assisted by digital orthophoto maps effectively mitigates systematic errors; (2) A point cloud smoothing algorithm significantly reduces noise levels; and (3) A cross-section extraction algorithm enables quantitative assessment of channel deposits and alterations. Conducting field experiments in Chutou Gully, Wenchuan County, China, in February and November 2023—representing pre and post-rainy season observations—validated the system's capabilities in markedly improving SLAM results. This advancement facilitates SLAM's efficacy in mapping challenging terrains, compensating for existing technology limitations in detecting debris flow channel interiors. The system aids in delineating detailed channel morphology, erosion patterns, deposit differentiation, volume estimation, and change detection. By rectifying the shortcomings of current methodologies, this methodological approach serves to augment the understanding of full-scale debris flow mechanisms, long-term post-seismic evolution, and hazard assessment in affected regions.

How to cite: Shen, P., Wang, T., Lu, F., and Kong, H.: A SLAM-based high-resolution full-character debris-flow channel morphological mapping system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13891, https://doi.org/10.5194/egusphere-egu24-13891, 2024.

16:30–16:40
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EGU24-7378
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On-site presentation
Markus Hrachowitz, Leonard Sklar, and Roland Kaitna

As a natural hazard in mountainous terrain, debris flows cause considerable disruptions, human casualties and economic damage in many regions world-wide. However, the spatially localized nature of debris flows together with the lack of data at sufficient temporal and spatial resolutions make the triggering processes difficult to describe. As a result, debris flows are problematic to predict. Effective regional and local early warning systems, built on both process-based or statistical models, have therefore so far remained elusive. Even more, common statistical models, such as  precipitation-intensity threshold models, rely on precipitation. As debris flows are essentially in-channel processes, precipitation is an indirect predictor and proxy for in-channel processes. As such it is not surprising that precipitation has limited predictive power. In spite of recent progress, general and detailed descriptions of in-channel processes that control debris flow triggering only start to emerge. Most generally, sediment supply and channel flow magnitudes can be considered major direct controls on debris flow occurence. As both are difficult to observe, they have so far not been systematically exploited and quantitatively described for their role as debris flow triggers.  


Based on 20-year records of hydro-climatic data, several dozens of well documented debris flow events in three contrasting head-water catchments in the Central Alps and a semi-distributed, process-based hydrological model, the objectives of our analysis are to (1) quantify the critical channel runoff magnitudes that have triggered past debris flows and to establish whether characteristic magnitudes can be found as a function of topography, soils, geology and other factors, (2) identify the relevance of snow melt vs. rainfall for the generation of debris flow triggering critical channel runoff, and (3) to test whether modelled critical channel runoff has higher power to predict debris flows than standard precipitation-intensity models.


Overall, we have found that indeed, relatively well-defined minimum critical channel flows as lower limits above which debris flows occur feature each of the three study catchments. It was also found that the general magnitudes are highly site specific. In spite of that, no obvious relation between the average critical flow magnitudes and landscape characteristics, such as local terrain or channel slopes, vegetation cover, soil type or geology at the three sites could be identified. In general, it was found that flow peaks, generated by short-duration, high-intensity rainfall events, mostly during summer, dominated the debris flow trigger dynamics at the study sites. In addition, several instances when debris flows were triggered by flow peaks of similar magnitudes but generated by high-intensity snow melt in combination with rain-on-snow were observed, highlighting the importance of quantifying liquid water input dynamics instead of bulk precipitation as system input that causally leads to the occurrence of debris flows. Intrinsically accounting not only for this distinction but also additional effects by evaporation, modelled channel flow magnitudes were found to be better predictors of debris flows, with respect to both, higher rates of true positives (correctly predicted debris flows) and lower rates of false positives (predicted but not occurred in reality), than traditional precipitation thresholds. 

How to cite: Hrachowitz, M., Sklar, L., and Kaitna, R.: Critical channel runoff as direct trigger of debris flows in mountainous terrain., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7378, https://doi.org/10.5194/egusphere-egu24-7378, 2024.

16:40–16:50
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EGU24-6819
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ECS
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On-site presentation
Tzu-Yin Kasha Chen, Leonard Sklar, Bryanna Pilkington, Emily Dickson, and Roland Kaitna

Debris flows pose significant natural hazards in mountainous regions globally, with the potential to cause substantial damage to villages and infrastructure in lowland areas. To effectively mitigate these hazards, it is essential to identify catchments prone to delivering debris flows to fan areas. Topographic metrics such as fan slope and catchment Melton number are useful at a regional scale but in recently deglaciated alpine landscapes do not explain high variability in debris flow frequency among neighboring catchments. Here we assess debris flow susceptibility by quantifying the spatial extent of sediment cover across upstream catchment areas and the connectivity of potential debris flow source areas to fans at catchment outlets.

The Pitztal Valley in the Austrian Alps serves as the study site, benefiting from elevation data (digital terrain model) and historical debris flow event data since the 1950s for 28 catchments, along with sediment cover maps for 18 catchments. To assess the likelihood that debris flows originating within sediment covered areas could reach the fan, we calculated the minimum mean slope angle along every flow path to the fan apex. Source areas with minimum angles lower than a dynamic friction angle are assumed to be disconnected from the fan apex because potential debris flows would come to rest and form coarse deposits upstream of the fan. This concept is utilized to calculate the fractional connectivity for sediment areas in each catchment as a function of dynamic friction angle.  Rather than assume a single friction angle, we compare catchments based on the angle corresponding to a connectivity rate of 50% for the sediment covered areas (referred to as the 50% connectivity angle).

We find a highly significant positive exponential correlation between the 50% connectivity angle and the historical debris flow frequency (in units of debris flow events per square kilometer of catchment area) using data from the 18 catchments with sediment cover maps. Validation is performed in 10 additional catchments where we identified sediment covered areas using a new algorithm that can distinguish bare bedrock from sediment deposits from the local topographic roughness. The observed debris flow event frequencies align closely with or fall within the confidence bounds predicted by the 50% connectivity angles, confirming that the combined evaluation of catchment connectivity and sediment availability successfully explains debris flow frequency in this landscape.

Lastly, the results are compared to models employing previously published metrics of connectivity and debris flow susceptibility, providing insights into the contribution and efficacy of this new approach.

How to cite: Chen, T.-Y. K., Sklar, L., Pilkington, B., Dickson, E., and Kaitna, R.: Assessing Debris Flow Susceptibility in Deglaciated Alpine Catchments: A Novel Approach Integrating Flow-path Connectivity and Sediment Availability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6819, https://doi.org/10.5194/egusphere-egu24-6819, 2024.

16:50–17:00
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EGU24-3161
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ECS
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On-site presentation
Martino Bernard, Matteo Barbini, Matteo Berti, Mauro Boreggio, Massimiliano Schiavo, Alessandro Simoni, Sandivel Vesco Lopez, and Carlo Gregoretti

In the Dolomites area, steep rocky cliffs are incised by several chutes that concentrate runoff and deliver it to the scree at their base. This interaction prompts erosive actions, creating channels for debris flows. After intense, short-lasting rainfall, the resulting runoff carries a significant amount of loose debris, forming a solid-liquid surge. This surging flow entrains boulders, gravel, and sand along its path, transforming into an increasingly substantial stony debris flow. To explore how headwater rocky catchments respond hydrologically and trigger stony debris flows, we utilize data gathered from three monitoring stations placed in distinct debris-flow catchments. These stations, located in the debris-flow initiation area of the basins, capture videos and flow-stage data, enabling us to observe the timing and type of the incoming flows. Over 15 years of monitoring, numerous instances of runoff and mass-transport phenomena have been documented. This comprehensive dataset is precious for analyzing the hydrological behavior of small, steep headwater basins and investigating stony debris flow initiation. An existing hydrological model has been partially reformulated, and its updated version was calibrated using the hydrographs measured via a sharp-crested weir. Testing this updated model against observations from two larger debris-flow catchments affirms its capability to replicate the initial phases of a debris flow, particularly when the sediment concentration is quickly increasing. Moreover, combining simulated runoff volume with the entrained sediment volume in the Rovina di Cancia catchment, estimated through DEM of Differences for the debris-flow events that occurred from 2009 to 2022, provides values for solid concentration suitable for predicting sediment volumes carried by debris flows.

How to cite: Bernard, M., Barbini, M., Berti, M., Boreggio, M., Schiavo, M., Simoni, A., Vesco Lopez, S., and Gregoretti, C.: Prediction of runoff-generated debris flows using hydrological modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3161, https://doi.org/10.5194/egusphere-egu24-3161, 2024.

17:00–17:10
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EGU24-5317
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ECS,ECS
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On-site presentation
Impacts of Glacier Activity on Glacier Debris Flow Evolution in a Changing Climate
(withdrawn)
Yao Li and Yifei Cui
Case Studies & Monitoring
17:10–17:20
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EGU24-17806
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ECS
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On-site presentation
Raphaël Kerverdo, Sara Lafuerza, Christian Gorini, Alain Rabaute, Didier Granjeon, and Eric Fouache

2nd October 2020, the Atlantic storm « Alex » triggered an exceptional Mediterranean flood event in the south-eastern region of France, affecting the coastal Alpine valleys of the Tinée, Vésubie and Roya rivers. The event is considered exceptional due to the unprecedented rainfall recorded within a 24-hour period, surpassing 650 mm at Mesche dam and the elevated liquid peak flows around 1 350 m3/s at Breil-sur-Roya. Geomorphological changes consequence of the flood event includes river-related effects such as debris flows, landslides and partial destruction of the forest cover on the slopes, together with the destruction of bridges, roads, and houses.

Our study focuses on the Viévola sub-watershed upstream of the Roya river, made up of 4 confined torrential sub-valleys: Dente, Morte, Para, Scabrie and Rabay valleys. Theses generated numerous of debris flows feeding the Viévola alluvial fan. Our observations show that these valleys were responsible for massive input of sediment which led to widening of the active channel of Roya river,bank erosion and embankments during the Alex flood event.

The major areas of sediment accumulation were quantified in order to determine the balance between the 'initial' volumes eroded such as upstream gullies sediments and landslide deposits and the 'deposited' volumes (Viévola alluvial fan). The sediment volumes were quantified by Digital Elevation Model of Differences (DoD) from aerial imagery available before and after the flood.

Pre-flood topographical data is of low quality while post-flood topography are better thanks to LiDAR datasets acquired in october 2020 and june 2021. A statistical study of tree heights on tributary slopes, using aerial and infrared images, allowed us to subtract them from the pre-flood digital surface model, creating a tree-free pseudo topographic surface.

Our results show that the Viévola sub-watershed produced approximately 304,000 m3 of sediment within a 24-hour period, with a margin of error of +/- 40,000m3 (an average error of 13%). The gullies at the head of the Dente and Rabay valleys produced 125,000 m3 of sediment, with an error margin of +/- 21,000 m3. These initial inputs from these gullies caused significant bank erosion in the Dente valley, resulting in the release of over 140,000 m3 of sediments, with an error margin of +/- 5,000 m3. This erosion led to a considerable widening of the Dente torrent channel, which expanded from an average width of 6.1m before the flood to 18.6m after the event. Based on field studies, we found that the cause of the bank erosion is linked to the debris flows that occurred in the Dente valley.

Comparatively, the Morte, Para and Scabrie valleys primarily contributed sediment from landslides, totalling around 21,000 m3, with an error margin of +/- 6.300m3. On average, the width of the torrents in these valleys doubled, with a factor of 2.1. Moreover, an alluvial cone formed at the Vievola holiday resort, resulting in a deposited volume of approximately 90,000 m3, with an error margin of +/- 20,000 m3. Consequently, an estimated 214,000m3 of sediment was exported to the Roya River.

How to cite: Kerverdo, R., Lafuerza, S., Gorini, C., Rabaute, A., Granjeon, D., and Fouache, E.: Budgeting sediment volumes mobilised during Storm Alex in the upper part of the Roya valley, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17806, https://doi.org/10.5194/egusphere-egu24-17806, 2024.

17:20–17:30
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EGU24-13686
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ECS
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On-site presentation
Krishna Priya Vk, Rajaneesh Ambujendran, Nikhil Nedumpallile-Vasu, Vanessa J Banks, Christian Arnhardt, and Sajinkumar Ks

To accurately assess landslide susceptibility and model debris flow paths, acquisition of high-resolution elevation data is essential. These data enable precise topographical analysis, considering factors like slope and curvature. But most of the time such high-resolution data will have inaccuracies due to vegetation, especially in tropical region. This study proposes a comprehensive approach that integrates field data and Structure from Motion (SfM) technology to rectify such DEM inaccuracies caused by dense vegetation. The goal is to enhance the accuracy of landslide simulations and volumetric analysis for effective post-disaster management. The Western Ghats, running parallel to India's western coast, has experienced a surge in rainfall-induced landslides, resulting in significant casualties in recent years. Notably, the Pettimudi village landslide in 2020 caused 70 deaths. The unique geomorphological features of the Western Ghats, such as concave curvature, colluvium deposits, and evidence of paleo landslides, contribute to the area's susceptibility. The study emphasizes the need for detailed assessment and mitigation strategies. The proposed method aims to improve the post-event high-resolution DEM accuracy by integrating field-collected elevation values and utilizing Agisoft Metashape software with the SfM algorithm. The rectification process involves combining elevation differences measured during a field study with photogrammetric elevation data. The field-collected elevation differences are crucial for rectifying these points, and enhancing the Digital Elevation Model (DEM) accuracy. The inaccessible source region is improved using a SfM-created DEM from drone footage, resulting in a more accurate post-event DEM. Correcting the 1 m DEM using an SfM-generated DEM proves challenging but significantly improves detail and accuracy, especially over the landslide source area. The impact of the rectification on accuracy is assessed by comparing volumes calculated from the initial DEM and the newly corrected DEM. The difference in volumes of debris depletion and accumulation, computed using initial and corrected DEMs, highlights variations, with depleted volumes being significantly larger due to the extensive depth increase over the landslide source region. These volumes are then utilized in Rapid Mass Movement Simulation (RAMMS) to validate the rectification process and enhance landslide impact predictions. Debris flow simulations in RAMMS, utilizing the rectified 1 m DEM, show specific outcomes at the landslide source region and toe of the landslide. The study emphasizes the importance of integrating SfM technology with field data to improve DEM accuracy, acknowledging the significance of additional field data for further refinement. The potential adoption of highly precise aerial imagery from Unmanned Aerial Vehicle (UAV) surveys is suggested to further enhance the SfM DEM. Debris flow modeling with RAMMS serves as a vital step in validating the accuracy and reliability of the rectified elevation model.

Keywords: Landslides, Western Ghats, Pettimudi, Digital elevation model (DEM), Structure-from-Motion (SfM) technology, Rapid Mass Movement Simulation (RAMMS)

How to cite: Vk, K. P., Ambujendran, R., Nedumpallile-Vasu, N., J Banks, V., Arnhardt, C., and Ks, S.: Integrated UAV and Field Data Analysis for High-Resolution DEM Enhancement, Rectification, and Debris Flow Modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13686, https://doi.org/10.5194/egusphere-egu24-13686, 2024.

17:30–17:40
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EGU24-20781
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ECS
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On-site presentation
Isabelle Cheff, Julie Taylor, Andrew Mitchell, Kathleen Horita, Darren Shepherd, Steven Rintoul, and Rob Millar

Hydrogeomorphic hazards are natural hazards that involve the mobilization, transport, and deposition of mixtures of water and debris or sediment and can take the form of floods, debris floods and debris flows. Such hazards occur in a continuum with varying size and concentration of entrained sediment and debris. Within this continuum, debris floods occur when large volumes of water in a creek or river entrain the gravel, cobbles, and boulders on the channel bed; also known as “full bed mobilization”. Debris floods have transient behaviour over the duration of the event with pulses of sediment laden (i.e., boulders and woody debris) flow and more diluted (i.e., water-like) flows. There is limited guidance in available literature on the hydraulic modelling of debris floods, in particular, Type 2 debris floods (i.e., diluted debris flows). There are several fluid dynamics models that could be used, and several rheologies that can be used to parametrize the flows, however, the complexity of real debris flood behaviour generally needs to be simplified to an equivalent fluid rheology in practice.

Following heavy, prolonged rainfall in southwestern British Columbia, Canada, in mid-November 2021, several road and railway crossings were damaged by hydrogeomorphic hazards and erosion. These events highlight the need for the design and construction of bridge crossings able to withstand hydrogeomorphic hazards for transportation network resiliency. The modelling work described in this study was in support of the design of an armoured channel for a site that was impacted by a debris flood in November 2021.

The proposed crossing is a steep and complex channel geometry, with channel slopes between 8 and 35%. Estimates of, flow depths, velocities, and shear stresses, were required for design. To capture the full effects of the steep and complex geometry of the proposed channel, debris floods were modelled in both two-and three-dimension using HEC-RAS and FLOW-3D, respectively. To provide conservative but realistic design values, multiple debris flood scenarios were modelled with the intention of capturing the range of transient behaviour expected over the duration of a debris flood and evaluate the uncertainties in the model parameterization. The debris flood model parameterization included a high and low mobility Bingham rheological parameters set (e.g. viscosity and yield stress) and modelling the flood as laminar or turbulent flow. The higher mobility turbulent flows are more representative of a flood condition that has a lower sediment concentration during the later stages of a debris flood event, while the lower mobility laminar cases are expected to be more representative of surge fronts with a higher sediment concentration.

Different debris flood cases provided critical design values for different parameters. Generally, the low mobility laminar flow was the most conservative for flow depth. Modelled velocity and shear stress were not only dependent on the debris flood case, but varied within the channel sections between the two and three-dimensional results. Design values were proposed using a percentile of the amalgamated results of all debris flood cases modelled to capture the variation of the modelled cases.

How to cite: Cheff, I., Taylor, J., Mitchell, A., Horita, K., Shepherd, D., Rintoul, S., and Millar, R.: Evaluating uncertainty in debris flood modelling for the design of a steep built channel, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20781, https://doi.org/10.5194/egusphere-egu24-20781, 2024.

17:40–17:50
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EGU24-3898
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ECS
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On-site presentation
Massimiliano Schiavo, Martino Bernard, Matteo Barbini, Mauro Boreggio, Sandy Lopez, and Carlo Gregoretti

Debris flow phenomena are difficult to predict because their occurrence depends on multiple factors (e.g. availability of sediment, volume, and rainfall intensity, as well as slope conditions before an intense rainfall event, etc.). When they occur, debris flows can significantly modify the topographic surface of conical-shaped fans and cones via erosion and deposition phenomena.
This contribution aims, for the first time, to use a Monte Carlo approach to simulate the most probable avulsion paths of debris flows and define those conveying a certain drainage area with a minimum occurrence probability. We rely upon various digital terrain models (DEM) available for the Fiames area (Cortina d'Ampezzo, BL), covering approximately 1.6 km2 , and the average local elevation and the standard deviation of each cell of the domain are evaluated. We then generate N=2000 Monte Carlo realizations of possible topographic (equiprobable) surfaces, according to the geostatistical procedure known as Sequential Gaussian Simulations (SGSIMs). On each topographic surface obtained, the optimal drainage network is extracted using algorithms that guide the flow, by gravity, along the directions of maximum slope, as commonly used in hydrology. It is therefore possible to obtain as many drainage networks as there are simulated topographies. The ensemble of drainage networks (networks) is used to obtain the most probable network, extracted from the average topographic surface among the simulated ones.
Furthermore, we set a threshold on the drainage area variable, thus it is possible to calculate the probability of having, in a domain's location, a flow conveyance (per unit of area) higher than the threshold one. Finally, it is possible to (at least preliminarily) evaluate the probability of existing infrastructure vulnerability by appraising the probability that they are located along possible drainage routes or not. The presented approach moves the analysis of avulsion paths within the probability space. It can be validated by verifying the correspondence between a part of the probable (synthetic) pathways with those that historically occurred. Furthermore, it allows us to define routes and (synthetic) triggering points different from the historical ones.

How to cite: Schiavo, M., Bernard, M., Barbini, M., Boreggio, M., Lopez, S., and Gregoretti, C.: Probabilistic delineation of debris-flow routing pathways in cones and fans within a Monte Carlo framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3898, https://doi.org/10.5194/egusphere-egu24-3898, 2024.

17:50–18:00
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EGU24-9638
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ECS
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On-site presentation
Jiewei Zhan and Zhaowei Yao

On October 5, 2021, a landslide-debris flow disaster chain occurred suddenly in Hanping village, Shaanxi Province, China. This catastrophic disaster chain damaged 7 houses, 41.9 hectares of arable land and 3 roads and resulted in 1 death. Based on a detailed field investigation of the disaster site, we analyzed the dynamic evolution of the disaster chain by using experimental analysis, unmanned aerial vehicle (UAV) photogrammetry, satellite remote sensing interpretation and the SBAS-InSAR technique and then preliminarily revealed the movement process and causal mechanism of the disaster chain. The results suggested that the first landslide initiated in the upper part of Canger cliff, which is the result of the combined effects of slope structure, earthquake damage, engineering disturbance, and rainfall infiltration. Among them, extreme rainfall events are the primary factors that induce landslides. Before the landslide, InSAR results showed that deformations had already appeared in the source area, and the deformation rate had a strong correlation with precipitation. Then, the potential-to-kinetic transformation effect and air cushion effects generated by the landslide movement in the narrow and steep section of Canger cliff led to the disintegration of the sliding body. With replenished surface runoff, the clastic flow gradually transformed into debris flow. Moreover, due to the dam-breaching effects at bayonets and bends and the entrainment effect of the high-density debris flow along the gully, the scale of debris flow increases gradually, resulting in catastrophic damage during the movement. The findings of this study provide a significant reference and guidance for understanding the chain-generation mechanism of landslide-debris flow disaster chains, as well as informing disaster prevention and mitigation strategies.

How to cite: Zhan, J. and Yao, Z.: Characteristics and mechanism of a catastrophic landslide-debris flow disaster chain triggered by extreme rainfall in Shaanxi, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9638, https://doi.org/10.5194/egusphere-egu24-9638, 2024.

Posters on site: Tue, 16 Apr, 10:45–12:30 | Hall X4

Display time: Tue, 16 Apr, 08:30–Tue, 16 Apr, 12:30
Chairperson: Alessandro Leonardi
X4.50
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EGU24-15247
Chi-Yao Hung and I-Ling Tsai

Debris flow, a prevalent natural hazard in mountainous terrains, exhibits distinct flow dynamics depending on its occurrence over a bedrock (rigid bed) or atop a substantial deposition (erodible bed). The investigation of this flow transition is imperative for the comprehension and mitigation of debris flow dangers. This study introduces a unsteady, and non-uniform model, conceptualized to simulate the transition between rigid and erodible beds in debris flows. The model's foundation lies in the principles of mass, momentum, and kinetic energy conservation. It integrates a linearized mu(I) rheology to articulate granular flow deformation, thereby capturing the intricate interplay among particles during flow. Additionally, the model considers the impact of Coulomb friction along the sidewalls. To derive numerical solutions, the governing equations undergo depth integration, employing the HLL scheme (Harten, Lax, and Van Leer) in synergy with a finite volume numerical method. Furthermore, to corroborate the model's predictions, a novel granular dam break experiment was conducted. These experiments utilized a narrow glass channel (3.5 meters in length and 0.04 meters in width), with variations in the initial deposit depth downstream to establish diverse basal boundary conditions. High-speed camera footage facilitated the application of the Particle Tracking Velocimetry (PTV) method for capturing granular motion and generating a velocity field. A thorough analysis of the measured velocity field enabled the validation of the model's predictions, affirming its efficacy in accurately simulating the flow transition between rigid and erodible beds in debris flows.

How to cite: Hung, C.-Y. and Tsai, I.-L.: Simulating Flow Dynamics in Debris Flows: Transition from Rigid to Erodible Beds in Granular Dam Break Experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15247, https://doi.org/10.5194/egusphere-egu24-15247, 2024.

X4.51
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EGU24-17437
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ECS
Katharina Boie, Verena Stammberger, and Michael Krautblatter

Erosion and entrainment can significantly increase the volume and hazard potential of a debris flow. Therefore, understanding those processes is crucial for creating numerical models that can accurately predict the extend of depositions and impact forces. The quantitative controls of erosion and entrainment are however still not fully understood nor implemented in predictive models. In this work, the erosivity along eight different debris flows is analysed. Data on the eroded volumes was acquired using geomorphic change detection on aerial and terrestrial laser scans from before and after the debris flow events. Flow width, flow velocity, momentum, basal shear stress, flow pressure and flow height were determined using back-calculated RAMMS Debris Flow models. Erosion was implemented in those models by successively increasing the flow volume in 20 m intervals along the debris flow channel based on the geomorphic change detection results. Additionally, channel characteristics like the average slope for each interval as well as the geologic conditions were considered. For all analysed parameters correlations with erosivity were found. However, among the observed debris flows, the parameters that correlate best differ and they have varying degrees of significance. The geological setting has a notable effect on erosivity as well as the correlations. Peaks in erosivity can be observed at transitions from a bed with lower erodibility, like bedrock, to a more easily erodible bed. Using the parameters that correlate best with erosivity for each individual debris flow, linear and multiple regression models were created, that relate erosivity to the respective parameters for each site.

How to cite: Boie, K., Stammberger, V., and Krautblatter, M.: Constraining erosion in debris flow models: A correlation analysis in contrasting erosional settings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17437, https://doi.org/10.5194/egusphere-egu24-17437, 2024.

X4.52
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EGU24-19520
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ECS
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Laura Bozzoli, Alice Crespi, Stefan Steger, and Mateo Moreno

Debris flows represent a typical hazard of Alpine mountainous areas, which can generate serious impacts on natural and socio-economic systems of affected territories. In the recent years, intense precipitation events caused numerous damage-causing erosional processes and mass movements, including debris flows, within Alpine torrential channels. Changes in the intensity or frequency of heavy precipitation events under climate change are likely to influence debris-flows occurrence. Understanding ongoing and future changes in debris flow hazard is essential for risk management procedures in Alpine territories, in particular for delineating current and future hazard zones. Since the underlying debris-flow simulations frequently build upon historical statistics of triggering rainfall intensities, accounting for non-stationary precipitation conditions may be relevant for further improving the management of debris-flow risk in the context of climate change.

This work tests a modelling workflow to explore how changes in the intensity and frequency of heavy rainfall, can be incorporated into official hazard assessment procedures and if such changes lead to relevant alterations in the current zonation patterns. Possible changes in the Intensity-Duration-Frequency (IDF) curves are derived from observations and climate model projections and corresponding hydrological responses are simulated through the Peakflow model. Hydraulic processes are then modelled by entering resulting hydrographs as input of the WEEZARD software and outcomes for the current and future climate conditions are compared. The contribution presents the first results obtained for the Toverino river test basin in the Province of South Tyrol (Eastern Italian Alps), and it discusses the strengths and limitations of integrating a climate-change perspective into standardized debris-flow hazard zonation procedures.

The research leading to these results has received funding from Interreg Alpine Space Program 2021-27 under the project number ASP0100101, “How to adapt to changing weather eXtremes and associated compound and cascading RISKs in the context of Climate Change” (X-RISK-CC).

How to cite: Bozzoli, L., Crespi, A., Steger, S., and Moreno, M.: Incorporating climate change projections into operational debris flow hazard mapping: Initial insights from the Toverino River Basin in South Tyrol (Eastern Italian Alps)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19520, https://doi.org/10.5194/egusphere-egu24-19520, 2024.

X4.53
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EGU24-19786
Brian McArdell, Jacob Hirschberg, and Perry Bartelt

Many different rheological models describing the behavior of debris flows are available, yet there is no general agreement on the appropriate rheology for a given problem. Here we report on full-scale observations of friction in debris flows, which can be used to help constrain the selection of flow rheology. Using measurements from a large force plate (area = 8m2), we investigate the frictional behavior using the ratio of shear (s) to normal force (n) of debris flows recorded at the Illgraben debris flow observation station, in southwest Switzerland. Due to practical constraints the force plate is installed in a horizontal concrete structure in the channel bed, and not tilted to match the slope of the natural channel bed upstream of the force plate (slope S=0.08), which may induce a small deceleration of the flow, which we assume is negligible, especially for flows with large depths. Flow depth is recorded at the center of the force plate using either a laser sensor (point measurement) or radar sensor (average value). Debris flows are characterized with relatively large friction values (s/n ~0.15) at the front of the flows which are about twice as large as the slope of the channel bed. This result is consistent with ideas from the literature describing large friction at the flow front. Flood flows, in contrast, have frontal friction values (s/n ~0.1) approximately equal to the slope of the channel, indicating approximately steady and uniform flow over periods of 10’s of seconds.  Several transitional events have been recorded with properties intermediate between debris flows and flood flows, with corresponding s/n values also intermediate between debris flows and floods. These friction observations were recently incorporated into a debris flow model (Meyrat et al., 2023) which is capable of predicting the transition between debris-flows and glacial-lake outburst floods. While these results are promising, more research is necessary to further explore the controls on debris-flow friction, also for events characterized by multiple roll waves or erosion-depostion waves.

 

Citation:

Meyrat, G., Munch, J., Cicoira, A., McArdell, B., Müller, C. R., Frey, H., & Bartelt, P. (2023). Simulating glacier lake outburst floods (GLOFs) with a two-phase/layer debris flow model considering fluid-solid flow transitions. Landslides. https://doi.org/10.1007/s10346-023-02157-w.

How to cite: McArdell, B., Hirschberg, J., and Bartelt, P.: Measurement of friction in debris flows, floods, and intermediate flows, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19786, https://doi.org/10.5194/egusphere-egu24-19786, 2024.

X4.54
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EGU24-20566
Wei Qian, Juan Du, Bo Chai, Hong yuan Kang, and Yu Wang

Global warming induces the number of glacial lakes and the risk of glacier lake outburst of debris flow (GLODF) increasing in the high-mountain region, especially in Peru and the Himalayan region. GLODF Susceptibility assessment is a critical work that uses the spatial occurrence probability of debris flow to guide risk management and mitigation. Multiple glacial lakes in the basin could trigger GLODFs. The possibilities of multiple glacial lake outburst floods, flood flow paths, the likelihood of transformation into debris flows, and the overlapping relationships of flow paths within the river basin need to be considered in susceptibility assessment, which is a system instability problem characterized by multiple triggering factors and pathways. This paper considered the system failure of GLODF and proposed a new method to analyze it. The method includes seven steps, i.e. setp1-Determine the range of the assessment area or watershed, step2-Screen and classify glacial lakes and gullies, step3- Draw flow path and key node diagram, step4-Label the switches and conductance parameters, step5- Construct the series relationships of flow paths, step6- Evaluate the susceptibility of GLODF and step7- Zone the susceptibility grade. Moreover, the susceptibility indexes of GLODF were proposed in this paper, which considered the main factor affecting glacial lake outbursts and debris flow along the gully. This method was applied to a case that is in the Congduipu River basin in Tibet, China. The river basin is approximately 366 km2 and has 6 glacial lakes (>0.1 km2), 11 gullies, and more than 4 GLODF events. The results indicate that among the evaluated glacial lakes, one has a very high probability of outbursts, two have a high probability, and there are three instances each of debris flow disasters with very high and high susceptibility, respectively. The historical disaster records and field investigation results in the Congduipu River basin have verified the evaluation method. This method is applicable to quickly evaluate the susceptibility of GLODF in the river basin with multiple glacial lakes and gullies. 

How to cite: Qian, W., Du, J., Chai, B., Kang, H. Y., and Wang, Y.: Susceptibility Based on System Failure: A Case Study of the Congduipu River Basin in Nyalam , Tibet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20566, https://doi.org/10.5194/egusphere-egu24-20566, 2024.

X4.55
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EGU24-21785
Increased frost-heaving hazard of synthetic water repellent soil
(withdrawn after no-show)
Huie Chen, Xiang Gao, Miao Li, Qing Wang, Boxin Wang, Jianping Chen, Fengyan Wang, and Qingbo Yu
X4.56
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EGU24-21821
Thickness of the shear band of silty clay–concrete interface: a case study of Songnen Plain, China
(withdrawn after no-show)
Boxin Wang, Jingjing Pan, Qing Wang, Jiaqi Liu, and Huie Chen
X4.57
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EGU24-21970
Alessandro Leonardi and Miguel Angel Cabrera

Physical modelling of debris flow has been instrumental for decades in enhancing our understanding of these processes. The geotechnical centrifuge plays a crucial role in this regard, enabling the creation of scaled models with stress fields closely resembling real-world scenarios. Despite its potential, the utilization of the geotechnical centrifuge is limited due to various challenges. Firstly, the technological complexity of designing and conducting experiments involving runout within the confined space of a centrifuge box poses a significant obstacle. Moreover, the interpretation of experimental results is hindered by the presence of apparent Coriolis acceleration, particularly for all kinematic processes. The Coriolis acceleration can potentially disrupt traditional scaling laws used for kinematic processes and lead to instability in simulated flows. Investigating this issue requires testing the same configuration on centrifuges of different radii, which is a formidable task.
In light of these challenges, this study proposes employing high-fidelity numerical simulations to examine the behaviour of an idealized granular flow in a centrifugal acceleration field. These simulations, based on the discrete element method, replicate an acceleration field analogous to that found within a geotechnical centrifuge. Unlike experimental setups, simulations are not constrained by technological limitations, allowing for the exploration of fully realized, steady-state flows under various conditions. The findings from the simulations indicate that traditional scaling can still be applicable, provided a sufficiently large centrifuge is utilized. However, in certain configurations, the Coriolis acceleration may induce instability, causing the flow to dilute, lose coherence, and disperse.

How to cite: Leonardi, A. and Cabrera, M. A.: Kinematics and scaling of granular flows within a centrifugal acceleration field, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21970, https://doi.org/10.5194/egusphere-egu24-21970, 2024.

X4.58
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EGU24-4018
|
ECS
Daniel Mckinnell and Chris Johnson

Debris flows are composed primarily of densely packed
particles of rock, surrounded by water. Excess pressure (that is greater
than hydrostatic) in the water decreases the stress supported the
granular matrix, and correspondingly reduces the overall frictional
resistance of the debris flow, allowing for larger velocities. Waves in
these flows can increase their run-out by creating deeper fronts of high
fluid concentration and high fluid pressure. Continuum models of debris
flows have been refined with the inclusion of variation in excess fluid
pressure. In this talk we will aim to examine the mechanisms in this
model by studying the idealised case of flow on an inclined plane. We
will solve for periodic waveforms to show the impact of varying fluid
pressure throughout the wave, and examine unexpected behaviour within
the model.

How to cite: Mckinnell, D. and Johnson, C.: Waveform behaviour in pressure varying debris flow models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4018, https://doi.org/10.5194/egusphere-egu24-4018, 2024.

X4.59
|
EGU24-4141
|
ECS
Riccardo Bonomelli, Marco Pilotti, and Payam Heidarian

In steep mountain areas, rapid mass movements such as avalanches and debris flows are surface processes which are characterized by large masses of granular material flowing at high speed. These processes may pose a serious threat whenever their path crosses populated areas, or damage key infrastructures. Numerical methods describing the motion of granular material coupled with remote sensing are the only option to assess run-off distance, velocity and depositional height, ultimately used to construct hazard maps. State of the art numerical modelling include three-dimensional and multiphase description of the phenomena. Despite the technical advancement provided by these implementations, which tend towards a complete model, in which both solid and liquid phases are considered, complexity, computational burdens and calibrating parameters scale accordingly. However, due to the intrinsic unknowns connected to debris flows (e.g. rheology, availability of sediments, liquid discharge), in the context of hazard mapping using a monophasic assumption regarding the physics of the flow is still a viable option because of the relatively low model complexity and computations times, allowing the user to perform multiple simulations to account for uncertainties. In the literature there are various numerical codes able to describe monophasic granular flow on complex topography both commercial (e.g. RAMMS, FLO-2D), and open source (e.g. HEC-RAS Mud and Debris flow), with different rheologic assumptions. Most models solve the classical Shallow Water Equations (SWE) which may not be valid in steep mountain bathymetry. Furthermore defining the flow depth orthogonally to the bottom may lead to practical difficulties in some situations, only solvable by introducing laborious pre- and/or post- processing calculations which may be complex on irregular topography. In this contribution we present some advances on a shock-capturing finite volume numerical scheme able to solve the recently introduced monophasic 2D Steep Slope Shallow Water Equations (SSSWE) on an unstructured grid using a set of different rheological laws (Manning, Voellmy and O’Brien). The use of an unstructured grid allows the user to capture in a simplified way the interaction between the flow and the buildings or channel beds naturally present in the computational domain regardless of the mesh size used. Furthermore, we present a novel analytical solution of a dam break test case on a sloping channel in presence of the O’Brien rheology, useful to benchmark existing numerical models. The numerical model implemented is called DEBRA (Debris-flow Evolution and Behaviour for Risk Assessment) and we assess its performance against other widely used commercial software for debris flow simulation.

How to cite: Bonomelli, R., Pilotti, M., and Heidarian, P.: DEBRA: A multi-rheological 2D steep shallow water finite volume scheme for debris flow propagation in mountain areas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4141, https://doi.org/10.5194/egusphere-egu24-4141, 2024.

X4.60
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EGU24-7084
Jinbo Tang, Peng Cui, Hao Wang, Yu Lei, and Yu Wang

Debris flows are prevalent natural hazards in mountainous regions, posing threats to human safety and resulting in property damage. Recent research has focused increased attention on characterizing the dynamic properties of these flows, especially in the vertical direction. The present study puts forth a mathematical model to describe the physics of debris flows. Specifically, concentration-weighted averaging is employed to represent the mass and momentum balance equations of the bulk granular-fluid mixture. Furthermore, an evolution equation for the slip velocity between the granular solid and liquid phases is derived in order to capture the separation between these constituents. The model determines the particle pressure based on frictional-collisional relations and the fluid stress via a Herschel-Bulkley rheological formulation. The coupled differential equations are solved numerically using a two-step finite difference projection method. The free surface profile is tracked using a volume of fluid approach. Favorable comparisons with experimental measurements validate the numerical model. Finally, analyses provide insight into the influence of the slip velocity on the dynamics of granular-liquid flows.

How to cite: Tang, J., Cui, P., Wang, H., Lei, Y., and Wang, Y.: Depth-resolved model for debris flows based on a two-phase fluid, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7084, https://doi.org/10.5194/egusphere-egu24-7084, 2024.

X4.61
|
EGU24-7312
Migration patterns of source materials and their potential indication for debris flow initiation in Wenchuan seismic area
(withdrawn after no-show)
Wen Zhang
X4.62
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EGU24-12479
Roland Kaitna, Benedikt Becsi, Matthias Schlögl, Tobias Schöffl, Markus Hrachowitz, Harald Rieder, and Herbert Formayer

Debris flows represent a severe hazard in Alpine regions. The initiation of debris flows is connected to several hydro-meteorological and geomorphological factors. For operational early warning and assessment of climate change impact, knowledge about critical rainfall conditions is needed. For several regions of the European Alps intensity-duration (I-D) thresholds for debris flows have been derived in recent years. In this study we provide triggering rainfall conditions of high temporal and spatial resolution for > 3700 documented torrent processes including debris flows that occurred in Austria between 2003 and 2022. Additionally, we estimate the change in their probability of occurrence in a future climate, based on an ensemble of bias corrected and localized EURO-CORDEX simulations. We find slightly steeper I-D curves for debris flows than for torrent floods and no clear trend indicating substantial influence of antecedent rainfall on the triggering rainfall. For all process types, it is shown that both the probability of occurrence and the areas affected by triggering precipitation events increase substantially in the future, with clear dependences on the emission scenarios (RCPs). The results of this study provide a basis for improved event forecasting in a changing climate. 

How to cite: Kaitna, R., Becsi, B., Schlögl, M., Schöffl, T., Hrachowitz, M., Rieder, H., and Formayer, H.: Triggering rainfall for torrent floods and debris flows in Austria and assessment of climate change impact, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12479, https://doi.org/10.5194/egusphere-egu24-12479, 2024.

X4.63
|
EGU24-8554
|
ECS
Furkan Karabacak and Tolga Görüm

As in many high mountainous regions of the world, Türkiye is also a country heavily affected by landslides. Considering that Turkey has the highest number of landslide-related deaths in Europe (14 per year), debris flows also have a devastating impact on the southern part of the country. On July 13, 1995, a debris flow killed 74 people and destroyed 180 houses in Senirkent District in Barla Mountain. Barla Mountain, where physical weathering is predominantly effective on widespread limestone, exhibits mainly arid/semi-arid climatic conditions. After the 1995 event, check dams were built within the scope of debris flow prevention. This study aims to perform susceptibility analyses of debris flow hazard using a spatially distributed empirical model (Flow-r) on the northern slopes of the Barla Mountain Belt.

All sub-catchments along the Barla Mountain Belt where the model was applied were afforested to mitigate debris flows. The Flow-r model consists of two stages: identifying potential source areas and calculating areas that could be affected by debris flows using flow direction algorithms. Potential debris flow source points and a digital elevation model with a spatial resolution of 5 m were used as model inputs. Model results were calibrated in each basin through reports of previous debris flow events (for Senirkent), aerial photographs, and field observations. Regarding the study's results, 7°-15 m/s model output was determined as the worst-case scenario, and 6°-17 m/s model output was determined as the extreme scenario. Through the field observations, physical weathering and debris production continued at elevations higher than the timberline depending on lithology and climate, and we observed that the check dams were filled with debris. According to the validation results of the Flow-R model we performed at this site, the accuracy, precision, and positive predictive power are 87.78%, 46.45%, and 23.03%, respectively. As a result of the study, considering the complex structure of debris flows, regional-scale debris flow susceptibility maps were produced with minimum data requirements and short computation times, and a primary source was provided in pre-disaster risk management studies. In the Barla Mountain, our findings identified differential weathering variations of limestone lithologies attributes and substantial debris generation as factors contributing to areas with a discriminating likelihood of debris flows under worst-case scenarios. Furthermore, the results of the model supported by the field observations revealed that the check dams in the region have lost their functionality. Moreover, on hillslopes subjected to afforestation, our findings indicated that the model's predicted spread areas did not align with historical debris flow occurrences.

How to cite: Karabacak, F. and Görüm, T.: Regional scale debris flow susceptibility mapping in Barla Mountains (NW Taurus), Türkiye, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8554, https://doi.org/10.5194/egusphere-egu24-8554, 2024.

X4.64
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EGU24-10028
Domenico Doronzo, Dario Delle Donne, Eliana Bellucci Sessa, Vincenzo Convertito, Mattia de'Michieli Vitturi, Sandro de Vita, Federico Di Traglia, Rosa Nappi, Lucia Nardone, Rosella Nave, Fabio Sansivero, and Mauro Di Vito

Lahars, landslides and debris flows are rapid natural phenomena that can heavily impact on and modify the environment, not only that from which they are triggered but also the one in which they propagate or leave deposits. In particular, lahars can reach significant runout distances from source areas (e.g., several km) and this can mainly depend, among other factors, on the morphology experienced by such propagation. There are cases in the recent history of natural occurrences in which lahars impacted catastrophically on rural and urban settings, such as for example at Nevado del Ruiz volcano (Colombia) in 1985 causing the death of thousands of people living around there. A more recent event occurred on November 26, 2022 at Ischia island (Italy), which is an active volcano particularly subjected to the recurrence of these phenomena. In this case, the emplacement of some lahars caused the death of a few tens of people and the damaging of tens of building, besides the direct impact on local agriculture and tourism. In the nearby Neapolitan volcanic area, several other lahar events occurred in the historical past, not only during but also after or well after explosive eruptions, as the evidence that these phenomena are still to be considered as complex and often unpredictable extreme natural events, also exacerbated by the climate changes, but also that they have some recurrence that cannot be neglected. Such kind of recurrence is mainly related to the local weather, which can even affect the intrinsic behavior of the flows that detach from the source areas and invade the territory. On the other hand, this is not a strictly statistical issue, as there are instrumental measurements that support the fact that heavy rains can exacerbate a landscape already prone to sliding, avalanching, and other catastrophic phenomena. For this, the November 26, 2022 Ischia case study was chosen with the goal of reconstructing the physical features that led to the lahar generation and invasion, which is something that might occur in the future but that should be experienced with a dedicated scientific and territorial consciousness. What was done is an integration of multidisciplinary approaches, corroborated by data from the INGV-OV monitoring network installed on the volcano, capable of detecting the otherwise lost flow timing and dynamical behavior. In particular, the seismic evidence that accompanied the Ischia lahar events, along with the consideration of some lithological features leading to an estimation of flow velocity and dynamic pressure, allow to discriminate multiple lahar pulses over the early morning of November 26, 2022. The main findings of this contribution are that the potential of the Ischia lahars had a sort of recharge timespan which depended on the local weather and lithological features, while the threshold of the lahar trigger depended on the hydrogeological conditions. The seismic reconstruction of the entire event allowed to quantify the first of these two critical issues at Ischia island.

How to cite: Doronzo, D., Delle Donne, D., Bellucci Sessa, E., Convertito, V., de'Michieli Vitturi, M., de Vita, S., Di Traglia, F., Nappi, R., Nardone, L., Nave, R., Sansivero, F., and Di Vito, M.: On the still unpredictable but recurrent lahars: the November 26, 2022 case study at Ischia island (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10028, https://doi.org/10.5194/egusphere-egu24-10028, 2024.

X4.65
|
EGU24-12866
An Acoustic-Seismo Station for Detection and Early Warning of Debris Flows in Chile
(withdrawn)
Jose Luis Palma Lizana and Oscar Bello
X4.66
|
EGU24-14131
|
Highlight
Shuai Li, Xiao-qing Chen, Xiao-jun Guo, Jian-gang Chen, Hua-yong Chen, and Xu-yan Wu

Predicting the deposition of debris flow is of great significance for hazard mapping, disaster reduction designing, construction of engineering, and settlements in vulnerable areas. There are many factors affecting debris flow deposition, such as landform, geological structure, debris flow characteristics, etc. However, these factors are finally realized by changing the migration and redistribution of particles in debris flow (particle sorting effect), and then through pore water pressure, shear force, friction resistance and momentum transfer. To this end, the laboratory flume experiments were conducted, focusing on the runout distance, deposit area, and maximum height, under different initial and boundary conditions such as water mass fraction and particle size. The experimental results reveal that the deposit morphology (e.g., runouts distance, deposit depth, and deposit width) of debris flow is closely related to the degree of particle size-segregation. Increasing water content first increase the degree of particle size-segregation which leads to longer longitudinal distance, however, too much water then reduced the degree of particle size-segregation, thus decreased the deposit distance. That is, the optimal water fraction corresponds to the well-distributed particle size-segregation, resulting in the longest deposit distance. In this condition, the friction among particles causes coarse particles to tend to move upward and forward, eventually accumulating at the front and surface, whereas fine particles tend to flow backward and downward, finally accumulating at the bottom and middle. Changing coarse particles size can only increases runout a little. However, well-distributed coarse particles can promote runout significant. The research can improve the understanding of debris flow accumulation and have important significance for quantitative risk assessment and risk zoning of debris flow.

How to cite: Li, S., Chen, X., Guo, X., Chen, J., Chen, H., and Wu, X.: Prediction of debris flow deposition based on particle segregation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14131, https://doi.org/10.5194/egusphere-egu24-14131, 2024.

X4.67
|
EGU24-14834
|
ECS
Matteo Barbini, Martino Bernard, Stefano Lanzoni, and Carlo Gregoretti

The bi-phase governing flow equations of a solid-liquid mixture are numerically integrated within the shallow water approximation using the finite volume method. The one-dimensional FORCE scheme is extended to the two-dimensional case and reviewed for use with a structured computational grid comprising quadratic cells.  The intermediate points, at which the solution is computed at time , correspond to the corners of a cell, and this solution is derived from the values of the four surrounding cells adjacent to the corner. Consequently, the solution for a (i, j) cell within the domain depends on the four intermediate solutions computed at the corners: ,, ,. Subsequently, for a (i, j) cell, the t+1 solution is reliant on the value of the at that cell and the values of its eight neighbouring cells. The model is used for replicating the flow depth, velocity, and solid concentration values observed in a systematic series of flume experiments documented in the literature. The comparison shows good agreement for solid concentration and satisfactory alignment for flow depth and velocity values. Finally, the model is used for reproducing the flow pattern of the debris flow that occurred on Rio Lazer on November 4th, 1966. The comparison results are satisfactory.

How to cite: Barbini, M., Bernard, M., Lanzoni, S., and Gregoretti, C.: A finite volume code for simulating debris-flow routing: preliminary results, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14834, https://doi.org/10.5194/egusphere-egu24-14834, 2024.