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.

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.

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.

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.