Orals: Mon, 28 Apr | Room L1
In May 2023 the village of Brienz/ Brinzauls, Switzerland was evacuated due to high landslide risk, drawing national and international attention. On June 15, 2023, a significant collapse occurred at the site, with a volume of 2 Mm³. This collapse followed a prolonged acceleration phase of a section of an old, partially active deep seated gravitational slope deformation (DSGSD). The Insel compartment is composed of ductile clay-schist at its base, overlaid by porous rauhwacke and brittle dolomites. In the present work, we analyse the complete dynamic and structural evolution of the Insel compartment using data from various monitoring systems, including 3D displacement measurements from a robotic total station (RTS, operational since 2012), bi-annual LiDAR surveys, Doppler radar monitoring of rockfall activity, ground-based InSAR monitoring (since 2018), and automated digital image correlation of high-resolution time-lapse images. We additionally developed simple analytical dynamic models to investigate the behaviour of viscoplastic and frictional materials.
The current study identified three key phases of the Insel compartment's evolution: (i) the compartment formation phase, (ii) the Insel acceleration and (iii) the terminal phase. During the formation phase (2018-2022), the compartment extended laterally and in the down-slope direction, and a transition from toppling to sliding kinematics was observed. The acceleration phase started in summer 2022 and was characterized by a prolonged exponential increase in displacement rates, occasionally interrupted with linear growth phases, persisting until early May 2023. In the terminal phase, four short-term surge episodes (lasting days to weeks) were noted, defined by rapid exponential velocity increases followed by stagnation. Surge episodes became more frequent towards the date of collapse and strongly influenced the short-term applicability of classical velocity prediction models such as the Voight’s model.
Based on the available data we developed a kinematic model of the Insel compartment, resulting in a two-wedge compound rockslide which moves on a bi-linear sliding plane. The upper, active wedge comprised brittle, heavily fractured dolomites, while the lower, passive wedge primarily consisted of ductile clay-schists. Intense subsidence at the top of the active wedge suggested the formation of a graben structure along pre-existing large-scale lineaments. The sliding planes dipped southward at 50° (active wedge) and 25° (passive wedge), with a sub-vertical internal shear/deformation zone (ISP) evolving at the kink point of the bi-linear sliding plane. The passive wedge exhibited decreasing displacement in downslope direction, indicating internal shearing and rupturing. At least one rupture plane formation was identified within the passive wedge, causing a rapid acceleration followed by velocity stabilization.
We could replicate the velocity characteristics of surge episodes by combining analytical dynamic models using viscoplastic and frictional materials. This led us to the conclusion that a complex interplay between rupturing within the passive wedge, displacements along the ISP and mass balance changes due to frontal collapses caused the complex dynamic evolution and hence the difficulties in the short-term applicability of Voight’s model. This comprehensive investigation offers new insights and valuable field observations of the complex interplay of structural, mechanical, and external factors driving the dynamics of compound rockslides.
How to cite: Schneider, M., Loew, S., Thoeny, R., and Aaron, J.: Structural and Dynamic Evolution of Compound Rockslides – Insights from the Brienz Rockslide Collapse of June 2023, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17802, https://doi.org/10.5194/egusphere-egu25-17802, 2025.
In June 2023, the "Insel" compartment of the Brienz/Brinzauls landslide system in Switzerland failed, mobilising approximately 1.9 million m³ of rock and almost reaching the village of Brienz/Brinzauls. As the event occurred at night, it could not be directly observed, highlighting the need for numerical modelling to better understand its initiation mechanism and kinematics.
Mechanical numerical modelling provides a powerful tool for investigating slope instabilities, allowing researchers to test hypotheses about failure processes and gain insights into kinematical behaviour when direct observations are not available. To explore the influence of mechanical and geometrical properties on the "Insel" failure, we conducted a parameter study using the distinct element code 3DEC. The study makes use of the extensive monitoring data available for the Brienz/Brinzauls landslide system, examining the effects of varying rock mechanical properties, sliding surface characteristics, joint orientations, sliding surface geometry, model resolution and dimension on the failure behaviour.
Our results highlight the critical role of accurately representing geological structures, such as bedding orientations and block shapes, as well as the sliding surface geometry. These factors significantly influence the model outcomes and the simulated failure dynamics. The model successfully reproduced the observed depositional patterns within the rupture zone and provided insights into the internal movements and temporal evolution of the “Insel” compartment during the failure offering a deeper understanding of the event and its underlying mechanisms.
How to cite: Pierhöfer, L., Kenner, R., and Gaume, J.: Modelling the influence of rock mechanical properties and rock structure on the 2023 Brienz “Insel” failure, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18302, https://doi.org/10.5194/egusphere-egu25-18302, 2025.
The initiation of rockslides on metamorphic rock slopes is often linked to the reactivation of pre-existing structures, accompanied by the progressive formation of new fractures over time. To demonstrate the crucial role of these progressive rock mass fracturing processes, we present an active rockslide within an anisotropic, fractured, foliated metamorphic rock mass, involving a failure volume of approximately 670,000 m3. The rockslide is located on the mountain ridge of the Mittlerer Burgstall (MBug, 2933 m a.s.l.), adjacent to Austria’s highest peak, the Großglockner. During the maximum glacial extent of the Little Ice Age, the MBug was a nunatak that was completely surrounded by the Pasterze Glacier. However, it has experienced rapid deglaciation in recent decades. To unravel the critical role of rockslide-related fracturing on the MBug, we applied an integrated methodological approach, encompassing field surveys, remote-sensing campaigns, laboratory analyses, process reconstructions, and a twofold numerical modelling approach.
The field investigations comprised geological and structural surveys. Laboratory analyses, including powder X-ray diffractometry and microscopic analysis, were conducted to determine the mineralogical composition and microstructures of the outcropping lithologies. Direct shear tests completed the rock mass characterization and helped to evaluate the shear strength properties of a critical shear zone. By multitemporal drone-photogrammetry campaigns performed annually since 2019, we reconstructed the rockslide process and derived high-resolution digital terrain models. The rock mass characterization and the process reconstructions further served as input parameters for our twofold numerical approach, which included discrete element (DEM) and finite discrete element modelling (FDEM). By utilizing the advantages of each approach, we study the effect of rock mass fracturing in the rockslide process and validate the model results with our process reconstructions.
The preliminary results show that the MBug exhibits a compound rock sliding mechanism, with steep fractures in the head area and a shallower dipping shear zone at the rockslide foot. The compound rockslide involves an active wedge bounded by the steep head fractures and a passive wedge that slides along the critical basal shear zone. In this compound architecture, rock mass fracturing is crucial, especially in the transition zone between the active and the passive wedge. This was reproduced in both DEM and FDEM numerical approaches and validated with the process reconstructions. Based on this comprehensive data basis, we discuss the crucial role that progressive rock mass fracturing has in this compound rockslide, which formed on a recently deglaciated, heavily foliated, metamorphic rock slope.
How to cite: Gerstner, R., Avian, M., Frießenbichler, M., Schneider-Muntau, B., Stauber, M., and Zangerl, C.: Unravelling the Critical Role of Rock Mass Fracturing in an Extensive High-alpine Rockslide, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9868, https://doi.org/10.5194/egusphere-egu25-9868, 2025.
Accurate identification and effective support of key blocks are crucial for ensuring the stability and safety of rock slopes. In previous studies, the number of structural planes and rock blocks was limited by considerations related to computational efficiency and capabilities, limiting the accurate characterization of complex rock slopes and hindering the identification of key blocks, potentially compromising stability and safety.
In this paper, a knowledge-data dually driven paradigm for accurate identification of key blocks in complex rock slopes is proposed. Our essential idea is to integrate key block theory into data-driven models based on finely characterized structural features to accurately identify key blocks in complex rock slopes. The proposed novel paradigm consists of (1) representing rock slopes as graph-structured data based on complex systems theory, (2) identifying key nodes in the graph-structured data using graph deep learning, and (3) mapping the key nodes of graph-structured data to corresponding key blocks in the rock slope.
Verification experiments and real-case applications were conducted using the proposed method. The verification results demonstrate excellent model performance, strong generalization capability, and effective classification results. The real case application is conducted on the northern slope of the Yanqianshan Iron Mine. The results show that:
(1) The proposed method has advantages in accurately representing the structural characteristics of complex rock slopes, which enhances the accuracy of key block identification;
(2) Integrating scientific knowledge of key block theory into GNNs facilitates the learning and capturing of internal structural characteristics of rock block systems and the distribution patterns of key blocks; and
(3) Our proposed paradigm is capable of accurately identifying key blocks from extremely imbalanced rock block systems, providing effective support and instability prevention of rock slopes.
How to cite: Qi, X., Meng, H., Xu, N., Mei, G., Peng, J., Mariani, S., and Vecchia, G. D.: A knowledge-data dually driven paradigm for accurate identification of key blocks in complex rock slopes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2926, https://doi.org/10.5194/egusphere-egu25-2926, 2025.
SLAB3D is a newly developed numerical model designed to address the practical needs of engineers evaluating the risks related to alpine mass movements. Based on the Material Point Method (MPM) and finite-strain elasto(visco)plasticity, SLAB3D incorporates various material models representing snow, ice, rock, and water. This enables detailed simulations of a wide range of materials under different flow regimes. In particular, a rate-dependent cohesive Drucker-Prager model, which recovers the liquid μ(I) granular rheology under flow, has been implemented and validated. Key features of SLAB3D include: 1) physical input data that can be derived from classical geotechnical or field experiments; 2) explicit simulation of bed entrainment; 3) the ability to simulate interactions with complex mitigation structures at very high resolution, achieving scales as fine as decimeters and evaluating the resulting impacts. The model is designed with practical applications in mind, integrating seamlessly with GIS tools to automate the visualization and interpretation of results in three-dimensional terrain. Validation against well-documented cases such as the Vallée de la Sionne and Salez snow avalanches, the 2023 Brienz rock avalanche, the 2017 Piz Cengalo and Vajont landslide tsunami events demonstrates SLAB3D's potential to replicate and predict real-world phenomena with high fidelity. Additionally, its application to dam overflow analysis highlights its potential for simulation-guided recommendations for the design and optimization of mitigation measures. As a tool for hazard assessment and engineering design, SLAB3D represents a promising step forward in modeling alpine mass movements, enabling us to perform tailored simulations for engineers and provide them with practical and versatile solutions.
How to cite: Gaume, J., Blatny, L., Kyburz, M., Vicari, H., and Wissmann, P.: SLAB3D: a practice-oriented 3D software for alpine mass movement simulations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19780, https://doi.org/10.5194/egusphere-egu25-19780, 2025.
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Change Detection and Clustering: Eroded blocks and rockfall changes are identified using DBSCAN clustering and centroid proximity.
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Volume Estimation: 3D point cloud data are converted into voxel and mesh representations for accurate volume estimation of eroded blocks.
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Erosion Rate and Density Calculations: Poisson Surface Reconstruction is applied to calculate the cliff face area and consequently calculate the erosion rates.
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Cluster Shape Classification: Clusters are classified based on a tyranny plot of rock shape relationships, and outputs are visualized through plots and summary statistics.
How to cite: Althuwaynee, O. F., Rosser, N., and Brain, M.: Automated Rockfall Feature Extraction using High-Resolution 3D Point Clouds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9404, https://doi.org/10.5194/egusphere-egu25-9404, 2025.
The Grafenhöfe site in Innervillgraten, Austria, has been affected by ongoing rockfall activity following the destabilization of a steep rock slope due to storm-induced deforestation (storm Vaia in 2018) and subsequent mass movements. The slope, composed primarily of marble and mica schist, experienced initial failures in September 2023, leading to repeated rockfall events and the partial infill of the Grafenbach torrent. In January 2024, further destabilization resulted in large-scale rock detachments, prompting immediate safety measures, including the evacuation of a farmstead.
To enhance safety during the construction of protective dams, the Austrian Torrent and Avalanche Control (WLV) implemented a pulse-Doppler Radar system (IBTP Koschuch) for real-time rockfall detection. The system provided continuous high-resolution monitoring, triggering alarms within two seconds upon detecting rockfall movement. This allowed for rapid response and significantly reduced exposure of construction workers to hazards on-site. For monitoring the deformation of the detached rock mass, an automatic continuous terrestrial survey was installed on the opposite slope. This provided insight into the development of the slope's deformation, allowing for the avoidance of construction during a potential large-scale failure of the rock mass.
The radar system, which was specifically developed for alpine settings, detects Doppler spectra, ensuring reliable detection independent of weather and light conditions. Integrated with an automated alerting network, it facilitated direct communication with construction teams and authorities, enabling proactive safety management. Beyond immediate hazard mitigation, the radar data provided a valuable basis for refining WLV's safety strategy, as evidenced by the correlation of rockfall detections with rainfall data, revealing a strong dependency: all detected rockfalls coincided with precipitation events, while rainfall did not always led to rockfall. This enabled an optimised risk management approach, where construction activities were suspended during rainfall, effectively minimising exposure to potential rockfall events.
This study underscores the effectiveness of real-time monitoring for adaptive hazard mitigation during high-risk construction projects. Future work will focus on refining detection algorithms and integrating AI-based predictive models to enhance early warning capabilities for rockfall hazards.
How to cite: Koschuch, R., Jocham, P., Hübl, J., and Schöffl, T.: Real-Time Rockfall Monitoring for Construction Safety Using Pulse-Doppler Radar at Grafenhöfe, Austria, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18127, https://doi.org/10.5194/egusphere-egu25-18127, 2025.
Mountain forests play a crucial role in mitigating natural hazards such as rockfalls and avalanches. Recent studies show that the presence of deadwood within these forests enhances the protective effect by increasing surface roughness, leading to a reduction of jump heights, kinetic energies and run-out lengths of rockfalls as well as an additional stabilisation of the snow cover to prevent avalanche releases. Conversely, deadwood provides a habitat for bark beetles, which can lead to significant tree mortality on a large scale, compromising the protective effect of the forest in the long term. These two contrasts form a key part in the discussion of mountain forest management with the main question whether deadwood should be cleared or not.
This paper explores a less common aspect of this discussion, focusing on the damage potential of sliding deadwood as a new, unknown form of natural hazard itself. Recent events in Switzerland reveal deadwood logs with lengths of up to 35 metres, which were mobilised and travelled several hundred metres of elevation in a single rapid descent, causing damage to civil infrastructure.
By adapting the non-smooth mechanics framework of RAMMS::Rockfall in combination with hard contact laws and Coulomb friction, we develop a physical model to simulate potential trajectories of such sliding deadwood logs from mobilisation to deposition. The model parameters are preliminarily calibrated with five well-documented case studies from Switzerland.
Preliminary results show that a specific predisposition of the deadwood in temporal and spatial dimensions is essential for the occurrence of such events. Firstly, for a sliding motion, a low friction to slope angle ratio is required. The low friction can either occur due to terrain conditions (e.g. wet soil, snow, foliage cover), the condition of the deadwood (wet log without bark and branches) or, in most cases, a combination of both. Secondly, the deadwood must be of a specific age, with sufficient decay to lose bark and branches but also sufficient residual strength so that it does not break on impact with the ground or standing trees (decay stages II – III after Maser & Trappe).
This new simulation tool contributes to the discussion of mountain forest management, indicating potentially dangerous areas for deadwood clusters as well as the critical decay stages of individual logs or snags to further optimise existing forest management strategies for an efficient and sustainable protection against natural hazards.
How to cite: Borner, J., Bebi, P., Ringenbach, A., Bartelt, P., Christen, M., and Leine, R.: Adaptation of a 3D rockfall code to assess the hazard of sliding deadwood logs in mountain forests, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19826, https://doi.org/10.5194/egusphere-egu25-19826, 2025.
Accurately identifying hazard-prone areas is critical for mitigating risks from gravitational natural hazards such as landslides and rockfalls. Although many models exist to simulate these rapid mass movements, there are often trade-offs between simplicity, robustness and precision. This study builds upon the well-established energy line principle by reinterpreting the energy line angle as a kinetic friction coefficient, enabling the derivation of equations of motion that describe the forces driving mass movements. Using the Lagrange formalism for a sliding friction block, the equations of motion are developed and solved numerically with an Euler-based algorithm applied to digital terrain models. This force-based perspective retains the energy line principle’s simplicity and robustness while offering improved accuracy. In this study, the method is evaluated using two case studies with 36 documented landslide and 6 rockfall events in northern Italy. The results were compared with those of a traditional energy-based approach as well as with documented past events. The refined model produces smaller, more differentiated runout zones, achieving 41% resp. 11% higher true positive and 65% resp. 16% lower false positive rates compared to the energy-based approach for reproducing the past rockfall and landslide events. These findings demonstrate that the developed approach enhances accuracy without increasing computational complexity. This enhancement has the potential to extend the application of the energy line principle beyond preliminary analyses, enabling more detailed and reliable hazard mapping at larger spatial scales.
How to cite: Marras, E., May, D., Dorren, L., and Giadrossich, F.: Enhancing the Energy Line Principle: A Force-Based Perspective for Simulating Gravitational Hazard Runout Zones, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16377, https://doi.org/10.5194/egusphere-egu25-16377, 2025.
Deep-seated landslides are widespread in mountain belts, and creep for long periods affecting large rock slopes and posing risks to human lives and infrastructures. They are controlled by rock type, structure, and progressive failure processes, and exhibit complex deformation patterns characterized by kinematic segmentation, heterogeneity, and nested sectors which might be prone to collapse. Additionally, displacement of shallow debris often obscure signs of deeper movements. Mitigating the risk associated with deep-seated landslides requires detecting and characterizing spatial and temporal movement patterns over wide areas. Satellite SAR interferometry (InSAR) generated from Sentinel-1 has proven to be valuable to this aim, however, with some limitations. High-quality interferograms enable effective wrapped phase fringe interpretation and unwrapped displacement maps, offering a more continuous picture of landslide kinematics. However, they are susceptible to noise or unwrapping errors, especially in heterogeneous and segmented landslides, reducing their accuracy. Multitemporal methods such as Persistent Scatterer Interferometry (PSI) provide accurate velocity estimates at specific points, but often fail capturing spatial segmentation or signals of processes occurring at different timescales.
To address these issues, we propose a stacking approach that leverages wrapped InSAR interferograms generated with the ESA SNAP software. The method involves selecting temporal baselines suitable to capture the processes of interest based on geological constraints, generating and manually choosing multiple interferograms covering overlapping time windows, and calculating median stacked phase values and residuals for each pixel. As we aim at analyzing slow, permanent deformation, we assume that our target signals in single interferograms never reach 1-fringe (2.8 cm for Sentinel-1). We also developed ad hoc descriptors to test pixel-wise the validity of such assumption. This approach, implemented in the MATLAB™ script AMSTACK, was validated with synthetic interferograms simulating different landslide rheology, segmentation, and noise. The method was then applied to slow-moving rock slope deformations in Valfurva (Central Alps, Italy), where glacial valley flanks up to 1500 m high are carved into phyllites and mica-schists of Austroalpine tectonic units. These slopes exhibit structurally complex gravitational deformations with sharp morpho-structural features and nested rockslides in various stages of maturity. Using Sentinel-1 images from snow-free periods between 2015 and 2023, we generated over 120 interferograms with a 1-year temporal baseline, without applying APS corrections. The application of our stacking approach to manually-selected wrapped interferograms allowed to: a) enhance signal-to-noise ratios, quantifying displacement patterns, rates, and segmentation for specific slope sectors without unwrapping errors; b) distinguish shallow from deep-seated movements in InSAR signals; and c) identify nested sectors susceptible to catastrophic collapse. Validation with field and multitemporal InSAR data confirmed the method’s reliability. This provided robust interpretations where the slow permanent deformation occurs, while residuals offered additional insights into areas with high phase gradients, nonlinear temporal trends, and shallow mass movements.
How to cite: Agliardi, F., Manconi, A., Morandi, A. V., and Reyes Carmona, C.: Deciphering complex landslide kinematics through DInSAR wrapped phase stacking, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7357, https://doi.org/10.5194/egusphere-egu25-7357, 2025.
Research on granular material flows has gained significance due to their critical role in various industrial applications and processes occurring on planetary surfaces. However, experimental studies examining granular flows under high-stress conditions where significant grain breakage occurs, as seen in phenomena like rock avalanches, fault ruptures, and post-impact crater formations are relatively scarce. This study presents findings from high-speed rotary shear experiments conducted on eight types of crushable granular materials and non-crushable materials, exploring different shear velocities and normal stress levels. We analyzed variations in shear resistance and viscosity during the experiments. After undergoing large strains, both shear resistance and viscosity stabilized, exhibiting independence from normal stress and material composition, but showing dependence on shear velocity. Our investigation identified two distinct behaviors: the strain-hardening regime and the strain-weakening regime. For crushable materials, there was a general trend towards velocity hardening at shear velocities below 0.1 m/s. However, a notable power-law weakening in steady-state shear resistance was observed with increasing velocity for shear rates exceedingly approximately 0.1 m/s, signaling potential material instability. Similarly, non-crushable glass beads displayed a comparable response. In the strain-weakening regime, all crushable materials adhered to a common set of power-law relationships, while non-crushable materials followed a different set. The transition from the strain-hardening regime to the strain-weakening regime can elucidate the onset of rock avalanches following prolonged creep deformation. Additionally, the pronounced weakening observed at higher velocities accounts for the enhanced fluidity and hypermobility characteristic of large geophysical grain flows. Under conditions of high-speed shear, the steady state of granular flow demonstrated that normal stress and material composition do not influence shear resistance and viscosity. However, the rate of weakening and the slip weakening distance are affected by these factors and are correlated with WEIBULL modulus.
How to cite: Gou, H., Hu, W., Li, Y., Zheng, Y., and Ge, Y.: The impact of normal stress, along with the material composition and shear velocity, on both the steady-state shear resistance and viscosity of rapid dry granular flows, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5348, https://doi.org/10.5194/egusphere-egu25-5348, 2025.
Glacier retreat and permafrost warming amplify geomorphological activity, increase rockfall frequency, and contribute to the preparation or triggering of rock slides and rock avalanches, often involving millions of cubic meters of material. However, high-magnitude rock slides situated in the cryosphere are rarely anticipated, primarily due to the remoteness and inaccessibility of the terrain, leaving pre-failure activity undocumented. Such events typically gain attention only after the occurrence, often due to the transition into long-runout rock avalanches that visibly impact large areas, potentially endangering alpine communities several kilometers distant from the rock slide source zone. The glaciated Vernagtferner basin (Austria, Tyrol) is a prime location for glaciology research, offering abundant data to also study the interactions between changing cryosphere and mass movements. It features highly weathered metamorphic rock slopes, ridges, and peaks, making it an exemplary site for studying typical alpine permafrost morphology and landslide processes. In this study, we characterize the geomorphic activity of the Vernagtferner basin through a landslide catalog and erosion rates assessed in three-year intervals from 2015 to 2024. Ultimately, we investigate the event of a recent rock slide/rock avalanche in spring 2024, originating from a permafrost ridge at 3,395 m asl, with over 50,000 m³ of volume loss in the source zone. The event exhibited an extended runout over snow and glacier surfaces. We combine seismic analysis, meteorological records, permafrost modeling, and rock mechanical modeling to identify the preparatory factors. With numerous potential failure sites distributed over vast areas and complex failure processes, spatial-scale rock slide prediction remains challenging today. Therefore, we focused on deciphering past events and the processes leading to them. This study's preliminary results help improve future predictive capabilities and mitigate increasing risks.
How to cite: Pfluger, F., Leinauer, J., Barbosa, N., Wegmann, P., and Krautblatter, M.: Crumbling Mountains: Pre-failure and failure analysis of the 2024 Permafrost Rock Slide and bifurcated Rock Avalanche (Platteikogel, Austria), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11904, https://doi.org/10.5194/egusphere-egu25-11904, 2025.
Permafrost rock slopes have been extensively studied, but seasonally frozen zones are often neglected. However, these rocks are subject to progressive destabilization driven by complex thermal and mechanical interactions. Their thickening in response to atmospheric warming is critical as pressurized water within them can induce short-term warming and thawing at depth through non-conductive, more efficient heat transport, potentially enhancing the destabilization of the rock slope.
This study focuses on the collapse of a 20 cubic meter, free-standing rock pillar on the Matterhorn Hörnligrat ridge on 13 June 2023, leveraging a unique long-term, multi-method monitoring dataset initiated in 2008. The pillar’s behavior was assessed through differential GNSS measurements, inclinometers, seismic monitoring, time-lapse imagery, weather data, and permafrost ground temperature records. These data reveal a strong seasonality in displacement patterns, with significant acceleration starting in 2022 and visually detectable changes two weeks before the collapse. Seasonal snowmelt infiltration into frozen fractures emerged as the primary driver of observed displacement patterns, a hypothesis corroborated by controlled laboratory experiments and thermo-mechanical modeling.
A 2D mechanical modeling framework (UDEC) was employed to evaluate the effects of seasonal freezing and thawing on fracture behavior, integrating results from laboratory shear tests conducted on Matterhorn rock samples under dry/wet and frozen/unfrozen conditions. The results highlight the critical role of a thawing-induced drop in the coefficient of friction along fractures, which drives shear stress changes and kinematic responses.
By integrating long-term field monitoring, laboratory experiments, and numerical modeling, this research provides insights into the destabilization of permafrost-affected rock slopes. It underscores the importance of incorporating seasonally frozen layers and their thermo-mechanical behavior into stability assessments, particularly under accelerating climate change.
How to cite: Weber, S., Bast, A., Beutel, J., Dietze, M., Kenner, R., Leinauer, J., Mühlbauer, S., Pfluger, F., and Krautblatter, M.: How percolating snowmelt water progressively destabilizes a free-standing rock pillar on permafrost: Field observations from Matterhorn (CH), laboratory experiments and mechanical modeling, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13130, https://doi.org/10.5194/egusphere-egu25-13130, 2025.
Steep alpine rock slopes in periglacial environments are complex systems, due to the strong interplay between weathering and sediment production, mass movements with different dynamics, and associated hazards. In the climate change context, permafrost degradation can trigger slow and fast mass movements (rockslides, rockfalls, debris slides), as well as destabilise rock glaciers on steep terrain. It is thus essential to clearly differentiate between these interplaying processes, along with their mechanisms, rates and controlling factors, to assess potential geohazard scenarios. In this perspective, we selected a rock slope in Val Cedec (Central Alps, Lombardy, Italy) as a natural laboratory. The slope is a 750-m-high glacial valley flank made of phyllitic mica-schists, covering approximately 5 km², with maximum elevations of 3000 m.a.s.l. and likely hosting permafrost above 2500.
We performed a conventional geomorphological survey based on photointerpretation of aerial images, fieldwork and analysis of DEM-derived products. We applied spaceborne InSAR products derived from C-band Sentinel-1 images (2017-2021) using data from different processing techniques (dual-pass DInSAR, multitemporal) and coherence maps to decouple the kinematics and timescales of the observed processes. We also applied thermographic techniques, combining Landsat-8 satellite images (2017-2021) with time-lapse thermograms captured by a high-resolution thermal camera during field surveys (July 2021 and August 2023).
Our preliminary observations reveal a complex interplay of mass movements, where shallow periglacial processes are coupled with deep slope deformations. The deep-seated movement is outlined by a double-crested ridge, and hosts shallower nested rockslides, whose scarps and fronts are source areas for rockfalls. Two rock glaciers occur in the upper-middle slope sector, one of which shows evidence of segmentation and destabilisation. In the lower part of the slope, at least three solifluction lobes have been identified, that redistribute the abundant debris produced by frozen rock masses disrupted by the deep-seated movement, and by rock glacier destabilisation. From the different temporal baselines of wrapped interferograms (6 and 12 days, 1 and 3 months, 1 year), we inferred a significant temporal variation in the displacement and coherence of rock glacier, rockslides and solifluction processes. Time series of ground surface temperature obtained by thermal images allowed mapping of slopes sectors likely to host permafrost. By combining this information with precipitation and air temperature data, we analysed the controlling factors of the different mass movements. Our preliminary results suggest that periglacial conditions favour the development of cascading mass movement processes, involving slow deep-seated and fast shallow movements that result in enhanced debris production feeding periglacial landforms prone to destabilisation. Accurately defining these processes and their interplay is crucial to define potential hazard scenarios.
How to cite: Reyes-Carmona, C., Agliardi, F., Gallia, L., Burrows, K., and Dini, B.: Timescales and interplay of complex mass movements in a periglacial alpine rock slope revealed by geomorphological, InSAR and thermal data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6387, https://doi.org/10.5194/egusphere-egu25-6387, 2025.
Rockfall events occur particularly in steep mountain areas and represent a major hazard for infrastructure and settlements. Complex interactions between susceptibility and triggering factors pose a great challenge for forecasting and managing this hazard. The increased rockfall activity in the Alps during the hot summer of 2003 has contributed to the growing interest in the link between rockfall occurrence and climatic changes caused by global warming. Rockfall inventories contain geographical and typological information on rockfall events and can serve as an important basis for obtaining information on the impacts of global warming on rockfall activity. However, such inventories are often incomplete, and the recording standards have changed over time, which may impair comparability.
In the present study, data from the regional rockfall inventory of the canton of Grisons (CH) with more than 1300 rockfall events were used to analyze their frequency over time and with regard to the climatic factors temperature and precipitation. We considered events from 1950-2023, with most of the release zones lying below the permafrost boundary. To avoid biases due to varying recording standards and completeness of the data, several observation intervals were defined, for which the data was analyzed separately.
The results show an increase in rockfall events over the last twenty years, regardless of the volume of the events. The increase is particularly evident in the rising number of summer events. Together with the increasing ratio of summer events to the total number of events over the past twenty years and a clearly negative trend in the number of winter events to the total number of events, this reveals a potential link to climate change. The highest frequency of rockfall events was observed in the spring months. In addition, an increased frequency was identified in the summer months, which is in line with the results of other studies.
The results of the temperature analyses were less clear. There are both negative and positive deviations in the average temperature on the day of the event compared to the long-term average in connection with rockfall events. The analysis of the temperature amplitude also showed no decisive results. The analyses of precipitation proved to be difficult due to the high daily variability. However, an increase in events related to precipitation was observed. During the event week, precipitation sum tends to be higher than in the weeks without an event, which underlines the importance of precipitation as a trigger factor.
The results of the study underline potential impacts of climate change on rockfall occurrence. They further illustrate the complexity of the relationships between climatic factors, geographical conditions and rockfall events. Finally, the study also underlines the importance of complete and detailed hazard inventory data at regional level.
How to cite: Moos, C., Stalder, A., and Erbach, A.: How does climate change impact rockfall occurrence at low elevations? Insights from a regional data set of historical events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7091, https://doi.org/10.5194/egusphere-egu25-7091, 2025.
Rockfalls pose significant risks to infrastructure, leading to safety hazards, road closures, and substantial economic losses from detour delays and damages to transport. These risks are expected to intensify due to the increased frequency and severity of storms, adverse weather events driven by climate change, and seismic activity, all of which accelerate rock slope deterioration. Current rockfall mitigation approaches present notable challenges. Short-term methods, such as scaling and blasting, are both costly and hazardous, as they require personnel to work directly on unstable slopes. Meanwhile, longer-term solutions, such as rock bolting or nailing, are often financially prohibitive for widespread application. Compounding these challenges is the subjective, ad-hoc nature of rockfall mitigation assessments, which creates uncertainty around the actual effectiveness and longevity of slope improvements. In many cases, slopes may return to a similarly hazardous or even more precarious state after mitigation, leading to ongoing cleanup and maintenance costs. This highlights the need for quantitative, objective methods to enhance rockfall mitigation practices, optimize maintenance strategies, and improve overall asset management. In response to this need, this research investigates the use of the morphological classification system, specifically the Rockfall Activity Index, to assess the effectiveness of mitigation techniques. A controlled field site was established to monitor post scaling morphological changes of the slope over several years with terrestrial laser scanning. By examining changes in magnitude-frequency relationships, activity rates, block sizes, precarious overhangs, and potential energy associated with slope failures, this study aims to provide actionable insights into more effective and sustainable rockfall management practices.
How to cite: Olsen, M., Leshchinsky, B., Wartman, J., and Bolkas, D.: Scaling New Heights: A Quantitative Approach to Understanding the Effectiveness of Rockfall Mitigation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3363, https://doi.org/10.5194/egusphere-egu25-3363, 2025.
The spatial distribution of landslide landforms provides critical information for predicting potential slope failures and generating susceptibility maps. While this approach is confined to the spatial domain and does not account for the timing of landslide events, it is highly valuable for spatial management and landscape evolution modeling. Effective implementation, however, requires not only a robust selection of predictors but also high-quality historical data on landslide occurrences, which serve as response variables for model training. Once a local model is established, the next step involves testing its applicability to new areas characterized by differing predictor ranges and variations in landslide features, such as shape and density. This is particularly important for landslide modeling in Norway, where the landscape, significantly reshaped during the Pleistocene, exhibits distinct topography and sediment deposits. Furthermore, the region's high-latitude setting imposes unique precipitation and temperature regimes, adding complexity to landslide prediction.
We applied machine learning techniques, including Random Forest and XGBoost, to identify the optimal model for calculating landslide spatial probability. Our analysis used databases of detected and mapped landslides from two regions affected by extreme precipitation events in 2019 and 2023. Model testing revealed low spatial transferability between regions, likely due to dataset quality and predictor characteristics. We examined multiple scenarios, including a global model incorporating landslides from both events. Key factors limiting prediction accuracy include the quality and quantity of historical landslide data, the range and properties of potential predictors, and the inherent characteristics of the response variable—namely, debris flows, which are highly elongated and tend to form clustered patterns.
The study has been supported through the NAWA Bekker fellowship (No BPN/BEK/2023/1/00055).
How to cite: Pawlik, L. and Fredin, O.: Modeling and prediction of landslides in Norway – a machine learning approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8825, https://doi.org/10.5194/egusphere-egu25-8825, 2025.
This research provides a comprehensive analysis of snow avalanche behavior in the Kullu region of the Indian Himalayas, integrating climate data, terrain characteristics, and field validation to develop a refined hazard zonation model. Over recent decades, the region has seen an increase in avalanche frequency and intensity, linked to rising temperatures, changing precipitation patterns, and human-induced factors such as infrastructure development. The study explores the intricate relationship between meteorological variables like snow temperature and wind speed, and the topographical features that influence avalanche susceptibility.
Using Object-Based Image Segmentation (OBIS) analysis, combined with field surveys and existing literature, the research enhances the precision of avalanche risk identification. This method allows for a more accurate delineation of high-risk areas, improving prediction models for avalanche occurrences. The findings also suggest that ongoing climate change trends will likely escalate the frequency and severity of avalanches, increasing the risks to local populations, infrastructure, and biodiversity in the region.
In addition to its local impact, the study offers valuable insights for global avalanche risk assessment and climate adaptation strategies in mountainous regions. It underscores the need for targeted disaster risk reduction efforts and the development of resilient infrastructure to protect vulnerable mountain communities and ecosystems. The research highlights the importance of incorporating climate change projections into risk management frameworks to mitigate future hazards. By advancing understanding of avalanche dynamics, this study contributes to broader efforts aimed at enhancing the resilience of high-altitude regions worldwide.
How to cite: Bansal, J. K. and Goswami, A.: Snow Avalanche Hazard Zonation and Climate Change Trends in Kullu Region of Himachal Pradesh, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-551, https://doi.org/10.5194/egusphere-egu25-551, 2025.
Posters on site: Mon, 28 Apr, 16:15–18:00 | Hall X3
Landslides are highly dynamic events in which the erosion and entrainment of basal sediment can greatly enhance landslide mobility and energy, extending travel distances and intensifying impact forces. Understanding under which erosive conditions the mobility of landslides will be enhanced or reduced, thus, is critical for improving hazard assessments. Yet, empirical models are still limited in quantifying and predicting these dynamics accurately, due to an insufficient understanding of the underlying physical conditions.
We aim to experimentally test and verify a recently proposed mechanical model for the mobility of erosive landslides (Pudasaini & Krautblatter, 2021). This model suggests that landslide mobility is governed by three distinct erosion-driven energy regimes (gain, loss, or neutrality), arising from the change in inertia and momentum production as bed material is eroded and entrained. Our goal is to generate laboratory landslides that maintain a uniform flow at the landslide-bed erosion interface to enable precise velocity measurements of sliding mass, erosion, and entrainment under pre-defined mechanical conditions. We developed an experimental setup, inclinable to 40° and comprising a 5 m long and 0.25 m wide landslide flume with transparent sidewalls, to study sediment transport processes across a 2 m long erodible bed in two dimensions. To achieve the proposed landslide energy regimes of gain, loss, or neutrality, the erodible bed is designed to be inertially weaker, stronger, or neutral relative to an initial sliding mass. For single-phase flows, this is accomplished by using different granular bed materials of varying densities relative to the initial sliding mass. For two-phase flows, the water content of the bed is adjusted relative to that of the initial sliding mass.
Here we present new experiments on dry and partially saturated flows suggesting that the inertia of the erodible bed influences slide mobility and affects the deposition morphology. We further show how Particle Tracking Velocimetry can be used to distinguish between landslide, erosion and entrainment velocities, which is essential for the calibration and validation of the proposed theoretical framework.
How to cite: Wetterauer, K., Müller, S., Pudasaini, S. P., Krautblatter, M., Boie, K., and Baselt, I.: Flume experiments on the mobility of landslides with erosion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6666, https://doi.org/10.5194/egusphere-egu25-6666, 2025.
Extreme glacial lake outburst floods (GLOFs) are characterized by flow velocities and peak discharges far exceeding those of “classical” floods. As such, GLOFs are frequently associated with extraordinary geomorphic impacts and remobilization of large volumes of material. However, surprisingly little is known about specific hydraulic and topographic conditions that drive and facilitate the erosion, transport and deposition of very large boulders (diameter > 3 m) during GLOFs. To bridge this gap, we analyzed examples of major GLOF events from around the globe and compiled the information about the remobilization of large boulders, using the analysis of time series of very high-resolution satellite images. Based on the interpretation of visual changes between pre- and post-event images, we distinguish: (i) eroded boulders (i.e., those only present in the pre-event images, not traceable in the post-event images); (ii) deposited boulders (i.e., those only present in the post-event images, not traceable in the pre-event images); and (iii) transported boulders (i.e., those traceable in both pre-and post-event images). We characterize each boulder (shape, dimensions, location, distance from the lake), its trajectory and surrounding topography (travel distance, minimum and mean slope of the trajectory, valley width) as well as the causal GLOF (GLOF mechanism, peak discharge). Our preliminary findings suggest that: (i) major GLOFs in mountain regions are capable transporting boulders exceeding 10 m in diameter; (ii) these boulders typically originate from a breached moraine dam or colluvial valley infill; (iii) the deposition of large boulders clusters in locations where the valley widens and/or the slope of the trajectory decreases. Since dimensions of transported boulders are linked to flood hydraulics, large boulders can be used as indicators of GLOF magnitude and can help to define boundary conditions for GLOF modelling studies. Our ongoing work covers a development of empirical relationships between the characteristics of mapped boulders, topography and GLOF characteristics, and the confrontation of observations with hydraulic theory and modelling studies.
How to cite: Emmer, A., Hrebrina, J., and Pummer, E.: Towards understanding the hydraulic and topographic controls of large boulders movement during glacial lake outburst floods (GLOFs), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6384, https://doi.org/10.5194/egusphere-egu25-6384, 2025.
Landslides in volcanic and sedimentary tablelands rank among the largest mass movement phenomena globally, yet their spatial patterns and prevailing mechanisms remain insufficiently investigated. Our landslide inventory, covering 517,000 km² of volcanic tableland in extra-Andean Patagonia, provides insight into the spatial distribution of various landslide types. Nearly continuous landslide rims along plateau edges are mostly formed by lateral spreads and rotational slides. However, flow-type landslides, particularly earthflows, are also remarkably prominent. These flows are predominantly concentrated in the wetter, higher-altitude western tableland regions that were glaciated by the Patagonian Ice Sheet (PIS) during the Pleistocene. In these formerly glaciated areas, landslides with flow element account for three-quarters of the total landslide area. Nevertheless, some of the longest flow-type landslides, exceeding 10 km in length, occur in steep, arid regions beyond the extent of the PIS. Statistical analysis underscores the critical role of caprock thickness in controlling flow-type landslide occurrence. A thinner caprock results in a higher proportion of weaker sedimentary/volcaniclastic underlying units being exposed along escarpments, thereby increasing susceptibility of the escarpments to viscoplastic deformations. Further investigation focusing on the geotechnical properties of these weak sub-caprock units is essential for a better understanding of the lithological drivers of the flow-type landslides in the Patagonian tableland.
How to cite: Kilnar, J., Pánek, T., Břežný, M., and Winocur, D.: When tableland flows: flow-type landslides in the extra-Andean Patagonia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10261, https://doi.org/10.5194/egusphere-egu25-10261, 2025.
Alpine mass movements, such as rockslides and rock avalanches, pose significant natural hazards and drive landscape evolution in steep terrains. Understanding rock slope degradation, fragmentation, and the dynamics of failure and transport mechanisms is crucial for hazard prediction and mitigation strategies. This study examines the effects of rock fragmentation on the mobility and deposition behaviour of rock avalanches through experimental and theoretical approaches.
We investigate the role of internal bonding strength in influencing fragmentation dynamics and subsequent runout behaviour. A novel experimental setup simulates dynamic rock fragmentation in rock avalanches using a model block with varying internal bonding configurations. Therefore, graphite connectors of varying strength and number per block are used, combined with different layering techniques. These connectors undergo prior shear strength testing, allowing us to predict the force required to achieve specific fragmentation patterns. Additionally, they facilitate flexible variation not only in the material of the fragments but also in the way the connections between fragments are formed. Unlike previous research, this experiment stands out by employing connectors that link fragments at discrete points using pins rather than continuous surface bonding. This method enables the creation of complex geometric shapes for model blocks and facilitates the investigation of a wide range of block configurations in a controlled laboratory setting. This two-zone model allows for significant impulse changes and analysis before and after impact. By quantifying fragmentation patterns in the runout zone, such as angular distribution, lateral and longitudinal deposits, energy dissipation, and the force required for fragmentation, we highlight the influence of internal structures on avalanche mobility.
Our findings provide valuable insights into rock avalanches and address gaps in existing research regarding experimental block geometries and internal structures. The variation of input parameters in these small-scale experiments supports the validation and calibration of dynamic fragmentation models, which can be used for hazard zone mapping. This study emphasizes the importance of integrating experimental research with practical applications to improve hazard preparedness, risk reduction strategies, and community resilience in vulnerable areas.
How to cite: Hilgert, F., Hübl, J., and Baselt, I.: Influence of Rock-Avalanche Fragmentation - Mobility Analysis focused on inter-fragment bonding strength , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5525, https://doi.org/10.5194/egusphere-egu25-5525, 2025.
Deep-seated landslide formations in rock slopes are common in areas with steep hillside geophysical features and torrential rainfall. These slopes commonly experience heavy rainfall during typhoons and extreme weather conditions, which reduce rock mass strength, leading to the failure of slopes. The Lushan slope in the middle of Taiwan has continuously slid due to typhoons and heavy rainfall for recent decades. The geological conditions and analysis parameters of natural slopes are difficult to grasp causing uncertainties and affecting the slope stability results. Considering these uncertainties, analyzing its collapse probability can provide a more objective assessment of the stability of the slope. This study will use the Finite Element Method (FEM) software PLAXIS 2D Mohr-Coulomb (MC) model and Van-Genuchten (VG) unsaturated model combined with rainfall infiltration displacement coupling analysis to establish and simulate the slope model of the Lushan landslide area from rainfall duration and groundwater level data. The rock mass strength, unsaturated and saturated parameters were back-calculated and sensitivity analyses were performed to explore the impact of these parameters on the rise of groundwater levels. The probability density functions (PDFs) of dependent parameter groups and independent parameters were determined to consider their uncertainties. Stochastic Finite Element Method (SFEM) analysis was conducted by combining Monte Carlo Simulation (MCS) method with FEM to perform random sampling and determine different parameter combinations of the chosen parameters as random variables with uncertainty. Finally, the probability of slope collapse was evaluated by considering the safety factor as the criterion for judgment. The PDF of the safety factor is used to infer the collapse probability of Lushan slopes under the conditions of different return periods and rainfall delays. In this study, the uncertainty of mechanical and hydraulic parameters is considered to explore the probability of deep collapse which can be used as a reference for the risk assessment and warning systems of large-scale collapse.
How to cite: Chakraborty, A. and Chang, K. T.: Integrating Numerical Methods to Assess Failure Probability of Rock Slopes Considering Uncertainties in Mechanical and Hydraulic Properties, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2129, https://doi.org/10.5194/egusphere-egu25-2129, 2025.
Many landslides occur in crystalline schist in the central Shikoku Mountains of Japan. Although landslides are thought to occur frequently in areas with inclined schistosity planes, an area in the southern Shirataki unit of the Sanbagawa metamorphic complex exhibits mesoscopic to microscopic folds (MMFs); the geological structure is horizontal at the mountain scale, but several rapid and catastrophic landslides have occurred over time. Most of these folds are upright, with an east–west strike and nearly horizontal hinge lines, and are associated with prominent cleavage planes parallel or at a steep angle to the axis plane. In this study, the relationships between landslides and MMFs in the southern Oboke area were examined along with detailed surveys of the recent Toyonaga, Iwahara-Tojiyama, and Aruse rockslides. The results showed that many landslides occurred in the north–south direction along cleavage planes. Among the landslides investigated in detail, there were detachment surfaces along cleavage planes, rupture surfaces along both cleavage planes and schistosity planes, and dense fissures that opened along cleavage planes and became rainwater pathways deep into the rock.
How to cite: Yamasaki, S.: Frequent landslides controlled by steep cleavage planes: A case of crystalline schist area in the central Shikoku Mountains where metamorphic processes superimposed, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5051, https://doi.org/10.5194/egusphere-egu25-5051, 2025.
The western slope of Sasso Maurigno (3057 m, Valgrosina, Sondrio, Italy) is affected by frequent instability events (mainly rockfall), the most recent occurring on 25 June and 11 October 2022. This study aimed to conduct geomorphological and geological-technical field surveys and geotechnical laboratory tests to characterize the Sasso Maurigno rock masses and set up a conceptual model of their behaviour. The output of field surveys and geotechnical laboratory tests (Geological Strength Index – GSI and Rock Mass Rating – RMR values, resistance parameters of intact rock and discontinuities) became the input parameters of a numerical stress-strain model which was developed, with the distinct element method (DEM) and the numerical code UDEC7 (Universal Distinct Element Code). Modelling was carried out for two scenarios: post glacial (Late Glacial), simulating the mechanical behaviour of the slope no longer affected by the Würmian glacial cover, and present-day. The mechanical characterisation of the materials in the post-glacial context was determined by increasing the present-day GSI and strength values by 15%.
At the highest elevations of the Sasso Maurigno slope, granitoid gneisses of the Grosina Unit (middle Austroalpine) outcrop and present a GSI of 40 and a RMR of 38.9. The gneisses are also characterized by five sets of discontinuities that led to the development of a wide tensile fracture at the top of the slope.
Modelling results show that in the post-glacial scenario, the deformations appear limited, but they are already visible at the top of the slope (up to 0.85 m). In the current context, the deformations increase by an order of magnitude (up to 4.89 m), describing an instability concentrated at the highest elevations and attenuating towards the foot of the slope and with depth. The recent rockfall episodes are in good agreement with the results of the numerical calculation, demonstrating how the field survey and laboratory investigations were able to characterise, objectively and reliably, the mechanical and strength components of the materials. The agreement between the numerical calculation and the real context also appears considering the position of the tensile crack observed at the summit of Sasso Maurigno, which is also highlighted in terms of displacements by the model.
Modelling has thus successfully described the behaviour of the slope in stationary terms, becoming an expression of the mechanical parameters collected on the terrain and in the laboratory and identifying the factors predisposing to collapse. The study and inclusion of the weather, climate and hydrogeological elements could promote the development of a conceptual model capable of considering triggering factors, also from a climate change perspective.
How to cite: Casarotto, C., Citrini, A., Morcioni, A., and Camera, C. A. S.: Field, geomechanical and laboratory investigations to develop and parametrize a numerical stress-strain model for the reconstruction of the Sasso Maurigno instability events (Valgrosina, northern Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11430, https://doi.org/10.5194/egusphere-egu25-11430, 2025.
The determination of the so-called design block is one of the central elements of the Austrian guideline for rockfall protection ONR 24810. It is specified as a certain percentile (P95–P98, depending on the event frequency) of a recorded block size distribution. Block size distributions may be determined from the detachment area (in-situ block size distribution) and/or from the deposition area (rockfall block size distribution). Deposition areas, if present, are generally accessible and measurable without technical aids. However, most measuring methods are subjective, uncertain, not verifiable, or inaccurate. There is no specification of minimum measurements, which influences the reliability of the block size distributions (the more measurements the more reliable). Also, rockfall blocks are often fragmented due to the preceding fall process. The in-situ block size distribution is (also) required for meaningful rockfall modelling. The statistical method seems to be the most efficient and cost-effective method to determine in-situ block size distributions with many blocks within the whole range of block sizes. Illeditsch & Preh (2023) have introduced a new approach to evaluate rockfall hazard using synthetic rock mass models based on Discrete Fracture Networks (DFNs). A general stochastic DFN approach assumes that fractures are planar discs and treats the other geometrical properties (e.g. position, frequency, size, orientation) as independent variables obeying certain probability distributions derived from field measurements of outcrops. Using DFNs it is possible to carry out exact rock mass block surveys and to determine in-situ block size distributions. Various distribution functions were fitted to several determined in-situ block size distributions of different lithologies. Their correlations were compared using the Kolmogorov–Smirnov test and the mean-squared error method. It is shown that the generalized exponential distribution function best describes the in-situ block size distributions across various lithologies compared to 78 other distribution functions. This approach could lead to more certain, accurate, verifiable, holistic, and objective results.
How to cite: Preh, A., Illeditsch, M., and Schagerl, A.: Deriving reliable block size distributions using synthetic rock mass models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18407, https://doi.org/10.5194/egusphere-egu25-18407, 2025.
With population growth, construction in high-risk areas increases, leading to more people and structures being adversely affected. Rockfalls constitute a significant portion of these natural events. However, in combating these disasters, advancing unmanned aerial vehicle (UAV) technologies and three-dimensional rockfall simulations provide highly accurate results in detecting rock blocks with fall potential, identifying hazardous zones in inaccessible slopes, and predicting possible movement trajectories. These technological advancements significantly contribute to field studies, saving considerable time and effort. Rockfalls occurring in the low-strength, Oligo-Miocene sandstone-siltstone-claystone alternation succession on the cliffs of Istanbul-Silivri District cause damage to people and structures along the coast. Additionally, the presence of bird nests on the cliffs affects the design of the reclamation project planned to be carried out in the study area. Within the scope of this study, high-precision mapping was conducted in the study area using RTK (Real Time Kinematic) and PPK (Post-Processed Kinematic) photogrammetric measurement techniques. Consequently, 2.58 cm/pix resolution orthophoto, a point cloud of the study area and 3D stereoscopic optical model of the terrain were produced. Subsequently, an engineering geology study was carried out in the area. Representative samples were collected for laboratory experiments and the orientations of joint systems such as layers, faults etc. were measured. Thin sections of these samples were prepared and petrographic examinations were carried out. Mechanical tests with the index were conducted to obtain the geomechanical parameters of the rock. Afterward, to evaluate the rockfall potential, a kinematic analysis was performed using the DIPS software with discontinuity measurements obtained from the field, revealing the presence of wedge-topple type rockfall potentials in the area. In the second part of the risk assessment, the geomechanical parameters obtained and data from field observations were evaluated collectively to develop an engineering geology model of the study area. This model was integrated with a digital elevation model, and a finite element analysis (FEM) of the slope was conducted using the RS2 program, based on the Hoek-Brown failure criterion. In the final stage, rocks at risk of falling were identified using high-resolution 3D terrain models and field observations. To determine the run-out distance, bounce height, velocity, and total kinetic energy of the falling blocks, three-dimensional rockfall analysis were performed using the RocFall3 software. In conclusion, the risks and hazards in the area were mapped along the cliff with their spatial distributions. Protective structures and remediation methods were then proposed to minimize these risks and hazards.
How to cite: Doğu, M. M., Ündül, Ö., and Nasery, M. M.: Assessment of Rockfall Hazards in Weak Rock Environments and Urban Texture-Compatible Solution Proposals: The Case of Istanbul/Silivri, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5237, https://doi.org/10.5194/egusphere-egu25-5237, 2025.
Yosemite National Park attracts millions of visitors each year that arrive to enjoy views of the iconic 1000-m-high granitic rockwalls. This setting, and the access roads to the park, are coincidentally prone to rockfall hazards due to their geology (e.g., exfoliating granite) and complex geomorphological features (e.g., glacially sculpted landscape). Because U.S. National Park policies limit engineering mitigation on natural slopes, rockfall hazard management along roadways typically rely on traffic management strategies informed by local risk assessment.
The access roads to Yosemite Valley (El Portal Road, Big Oak Flat Road, and Wawona Road), where most visitors travel, pass through areas characterized by a variety of rock types (generally variations of Cretaceous granitic rock) and geomorphological settings, such as high-relief glacial valleys with steep rock walls and talus deposits, as well as areas with lower local relief characterized by gentle, subdued topography, intense weathering, and thick granular soils. These characteristics influence the nature and severity of rockfall hazard and risk along access roads. To assess rockfall hazard and risk along the park’s roadways, a probabilistic risk analysis was conducted to estimate annual probability of loss of life for visitors on the three entrance roads to Yosemite Valley. The analysis was based on 3D rockfall simulations performed using the Hy-STONE rockfall runout modeling software and on rockfall event and vehicle traffic data collected by the National Park Service. Rockfall runout simulations leveraged high-resolution data (1-m LiDAR-derived DEM and canopy height models, geology, and vegetation maps), a unique database of rockfall events (1857-2023), and focused field surveys to map slope deposits, rockfall evidence, and potential source zones.
A probabilistic rockfall hazard analysis (PRHA) was performed to determine the kinetic energy that could be exceeded in N years for each 10-m-long segment of road, for each travel lane (inbound and outbound from Yosemite Valley) on the three access roadways. This analysis considered different rockfall volume scenarios (0.01-100 m3) and model uncertainties. By combining these expected kinetic energies with annual rockfall frequency and an exposure analysis based on vehicle speed and size, the study calculated the dynamic annual probability of loss of life considering weekly and seasonal variations.
The results indicate that, depite vehicle traffic conditions, rockfall risk is lower in high areas with low local relief, where rockfalls are frequent but tend to be small in size and have limited runout distances. In contrast, areas with high local relief (i.e., Yosemite Valley and adjacent Merced River gorge) exhibit higher rockfall risk, due to larger, more frequent rockfalls with greater hazard potential. These findings highlight the importance of considering the specific characteristics of each area when assessing and managing rockfall risk. Adopting an approach using detailed modeling of all park access roads provides a more complete and integrated understanding of rockfall risk, with potential applications in risk management and land use planning. Consequently, this study will offer park managers valuable tools to make adaptive, datadriven decisions for managing risk in response to dynamically changing conditions in space and over time.
How to cite: Bruschetta, R., Agliardi, F., Frattini, P., Stock, G. M., and Collins, B. D.: Towards integrated management of rockfall risk along the access roads to Yosemite Valley (California, USA), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5882, https://doi.org/10.5194/egusphere-egu25-5882, 2025.
Many factors can trigger slope failure, with rainfall and groundwater variation being the primary causes. The failure time of rainfall-induced slope failure may be affected by the depths of the sliding surface and rainfall types, including rainfall patterns, duration, and the return period. Hourly accumulated rainfall may not be an efficient parameter for predicting slope failure, considering rainfall type variations or sliding surface depths. This study examines the appropriate rainfall parameters and thresholds for predicting slope failure with shallow and deep sliding surfaces at 10m and 40m depths.
This study adopted PLAXIS LE 3D, the limit equilibrium method, to obtain the factor of safety variation by time under different rainfall patterns, return periods, and durations. By accumulating rainfall over various periods, we derived various rainfall curves, referred to as” rainfall parameter curves” in this study. Using the rainfall parameter curves and the factor of safety variation, we can find the suitable rainfall parameters for shallow or deep sliding surfaces and then obtain corresponding rainfall thresholds for early warning. The result showed that short-term rainfall parameters and small threshold values are more appropriate for alarming slope failure with shallow sliding surfaces. On the other hand, long-term rainfall parameters and large threshold values are more appropriate for alarming slope failure with deep sliding surfaces. The rainfall parameters and the threshold values have a stronger relationship with the depths of sliding surfaces than with the types of rainfall.
How to cite: Liu, P.-C. and Chang, K.-T.: Study on Early Warning of Landslides by Using Rainfall Parameters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2647, https://doi.org/10.5194/egusphere-egu25-2647, 2025.
Geological structures, such as bedding, faults, folds, joints and fractures often contribute to decreased stability of rock slopes according to their strike and dip with respect to the general orientation of the main slope. Additionally, a rock slope may undergo many forms of gravitational displacement-induced (e.g. toppling), erosional (e.g. river undercutting) and/or weathering-induced destabilisation.
A variety of deep-seated very large (with a volume of > 107 m3) rock slope failures have been analyzed according to their structural characteristics. Studies include field surveys with structural geology measurements and image collection with Unmanned Aerial Vehicles (UAVs). The latter were then used to construct digital twins of the rockslide sites. Structural elements were analysed by using stereoplot tools that can also produce 3D outputs of the studied planes. In a few cases additional geophysical data were collected in the field (both on the rockslide deposits and on bedrock around the scarps). All those data were then combined within 3D geomodels of the studied sites and related 3D representations were integrated in immersive virtual environments.
One first practical objective of the use of 3D constructions from UAV imagery within Virtual Reality is to investigate sites that are barely accessible in the field, such as the rock outcrops within high and very steep rockslide scarps. Second, 3D geomodels help reconstruct the subsurface domain and allow for viewing the geological structures from all sides in order to understand better the spatial relationships between different structural elements (including different joint families, and toppling-related folding and fracturing).
For a few cases, also numerical models have been developed to study the influence of structural and geomechanical elements on (potentially seismically induced) rock slope failure. The main goal is to identify features that would allow us to distinguish seismic trigger modes from climatic ones, notably on the basis of the source zone rock structures. For instance, anti-dip slope bedding orientation may hint at a seismic origin, but we also consider a series of mixed structural types, which are more difficult to be interpreted as markers for a seismic or of climatic rocsk slope failure origin.
Most of our studied rockslide sites are located in seismically active mountain ranges (southeastern Carpathians, Caucasus, Tien Shan, Eastern Tibet and Longmenshan). However, outcomes of this study could also help identify rockslides with a partly seismic origin in less seismically active mountain regions, such as the northern and western Carpathians and the Alps. In the Alps, sites previously studied include the Fernpass, Tamins, and the Oeschinensee and Kandersteg rockslides and avalanches.
How to cite: Havenith, H.-B., Piroton, V., and Goire, J.: UAV surveys, 3D geomodels and Virtual Reality supporting the structural geology analysis of large rockslides, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1480, https://doi.org/10.5194/egusphere-egu25-1480, 2025.
The "ONR 24810: Technical Rockfall Protection – Terms, Impacts, Design and Structural Development, Monitoring, and Maintenance" provides a comprehensive technical guideline for planning and dimensioning of technical rockfall protection measures in Austria. This standard encompasses all steps in mitigation planning, from site assessment and impact analysis to construction and maintenance. For rockfall protection fences, detailed sections cover for structural verification, anchor design, non-standard impacts, construction guidelines and service life considerations.
With the planned transition of ONR 24810 into an OENORM, it is crucial to evaluate its applicability in practice. An OENORM is a fully developed standard that can be legally binding, while an ONR is not legally binding unless explicitly referred to in contracts, laws, or regulations. OENORMS are designed to align with European (EN) or international (ISO) standards where possible.
This contribution focuses on different aspects such as on comparing 2D and 3D rockfall models used in dimensioning safety measures under the ONR 24810 framework. By analysing their respective strengths, limitations, and suitability for different terrain conditions, we aim to provide insights into their practical implementation. Key aspects include the definition of design blocks, jump height differences, model accuracy, and the implications for designing effective protection systems in different countries. These findings will inform the ongoing development of ONR 24810 into a more robust OENORM standard, ensuring it remains a practical and reliable guideline for rockfall protection.
How to cite: Hormes, A., Garcia, B., Noël, F., Fleris, E., Hübl, J., and Melzner, S.: How to apply ONR24810 in practice – a critical review of the applicability, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20677, https://doi.org/10.5194/egusphere-egu25-20677, 2025.
Posters virtual: Mon, 28 Apr, 14:00–15:45 | vPoster spot 3
EGU25-9241 | Posters virtual | VPS12
Challenges in rockfall modelling in active tourism gorges: The case study of Caminito del Rey (Malaga, Spain)Mon, 28 Apr, 14:00–15:45 (CEST) | vP3.29
Rockfall modelling in Caminito del Rey (Málaga, Spain) represents a scientific and technical challenge due to the high geomorphological complexity of the environment, characterized by vertical cliffs, numerous overhangs, and complex geometries. In this context, within one of Malaga’s most visited tourist attractions (more than 300,000 people per year), a comprehensive study was required to address challenges across all phases, from the detailed characterization of the inventory to trajectory modelling. To address these difficulties, the most advanced technology currently available for remote data adquisitation (UAV, LIDAR and satellite) and three-dimensional modelling was used, along with the development and application of ad hoc methods and techniques specifically tailored to this study.
The high-precision georeferenced digital rockfall inventory had to tackle issues such as data heterogeneity, limitations in the available documentation, and errors related to mapping accuracy of the trail layout. On the other hand, the modelling process required a multiscale approach, examining all sections of Caminito del Rey with a focus on detailed scales for individual blocks. Custom input data were obtained for this purpose: (i) elevation models accounting for overhangs and both gorge walls; (ii) source areas for rockfalls derived using probabilistic approaches; (iii) block size estimation based on lithology type; and (iv) calibration and validation of the three coefficients maps in narrow and vertical sections (i.e., dynamic rolling friction, normal energy restitution, and tangential energy restitution) that simulate energy loss by a boulder when rolling and bouncing at impact points.
Reducing uncertainty in each input dataset is essential not only for improving the reliability and accuracy of analytical models but also for effectively establishing preventive measures. Furthermore, it plays a key role in identifying critical areas that require continuous monitoring. This abstract was supported by the KINGSTONE project, the Rockfall Susceptibility Study in Caminito del Rey (a collaboration among IGME-CSIC, the University of Granada, the University of Jaén, and the Caminito del Rey UTE), and the SARAI project (PID2020-116540RB-C21), funded by MCIN/AEI/10.13039/501100011033.
How to cite: Sarro, R., Galve, J. P., Martínez-Corbella, M., Fernández-Naranjo, F. J., Miranda-García, P. V., López-Vinielles, J., Jerez-Longres, P. S., Ruiz-Fuentes, A., Béjar-Pizarro, M., Guardiola-Albert, C., Azañón, J. M., and Mateos, R. M.: Challenges in rockfall modelling in active tourism gorges: The case study of Caminito del Rey (Malaga, Spain), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9241, https://doi.org/10.5194/egusphere-egu25-9241, 2025.
