A clear and robust evaluation of how ongoing and expected global warming and the resulting climate change can affect these factors and, hence, landslide risk represents a clear key need for practitioners, communities, and decision-makers.
This session aims to provide a discussion forum for studies concerning the analysis of the role of climate-related variables and slope-atmosphere interaction on landslide triggering, propagation, and activity and/or on the effectiveness of protection measures across different geographic contexts and scales. Test cases and investigations (by exploiting monitoring and modelling) to evaluate ongoing and future landslide activity are welcome. Furthermore, investigations focused on data-driven approaches (Machine Learning, AI), through which the variations induced by climate and environmental changes on triggering, dynamics, and hazard are analysed, are greatly welcome.
PICO: Tue, 5 May, 16:15–18:00 | PICO spot 3
Climate change is expected to alter rainfall regimes worldwide, with growing evidence that changes in rainfall characteristics extend beyond precipitation totals to include shifts in intensity, intermittency, and temporal organisation. However, the extent to which such structural changes in rainfall patterns influence rainfall-triggered landslides remains insufficiently explored, particularly in tropical and subtropical regions where empirical evidence is scarce. Moreover, beyond aggregated seasonal or annual metrics, the role of rainfall structure in governing landslide triggering processes remains poorly constrained, motivating renewed methodological approaches to rainfall–landslide analysis.
In this contribution, we investigate multi-decadal changes in rainfall characteristics and their implications for urban landslide occurrence using a long-term daily rainfall record (1940–2024) from the Santos–Saboo rain gauge, together with a harmonised inventory of 2,252 urban landslides from Santos and Cubatão (420 km²), São Paulo state (Brazil) spanning 1988–2024. Rainfall structure is characterised through analysis of annual totals, annual mean event intensity, seasonal intensity patterns, and event-based intensity distributions. Long-term trends are assessed using Mann–Kendall tests with Sen's slope, together with the Standardised Precipitation Index (SPI) computed at multiple accumulation timescales. This approach explicitly evaluates shifts in rainfall concentration and temporal organisation beyond simple magnitude-based assessments.
Results show no significant long-term trend in total annual rainfall at Santos–Saboo. In contrast, clear modifications in rainfall structure are observed, characterised by increasing annual mean event intensity (+0.031 mm day-1 year-1, p<0.01) and amplification of extreme event intensity (95th percentile: +0.081 mm day-1 year-1, p<0.05), with particularly strong winter intensification. These patterns suggest a tendency towards more concentrated rainfall delivery within events, which is consistent with expected climate-driven changes in precipitation regimes. Landslide frequency across the study period exhibits high inter-annual variability (±86 events/year) but no statistically significant long-term trend (p=0.09, Sen's slope=0.71 events/year), despite a weak positive tendency. Similarly, seasonal analyses show non-significant trends across all seasons. This points towards landslide activity remaining episodic and primarily controlled by individual extreme rainfall events, potentially obscuring long-term climatic signals in event frequency.
The findings highlight the importance of rainfall structure diagnostics for understanding climate-related changes in landslide hazard and for informing threshold-based early warning systems. Despite clear intensification of rainfall characteristics, the absence of increases in proportional landslide frequency suggest complex landscape responses, potentially influenced by countervailing factors such as improvements in urban drainage, slope stabilisation measures, changes in exposure, or early warning effectiveness. Overall, the study demonstrates the value of combining long-term station records with rainfall structure metrics. This approach provides a robust foundation for future methodological expansion, by using additional gauges, satellite rainfall products, and broader landslide inventories in underrepresented tropical and subtropical regions.
How to cite: Pereira Hader, P. R. and Irigaray, C.: Climate-driven changes in rainfall structure and urban landslide dynamics in subtropical Brazil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20911, https://doi.org/10.5194/egusphere-egu26-20911, 2026.
Landslides in mountainous regions are major climate-related hazards that are expected to increase in frequency with greenhouse warming and intensified rainfall. Coarser-resolution Earth System models participating in the Coupled Model Intercomparison Project are not adequate to resolve atmospheric responses in steep terrains, such as the Himalayas or the Andes. Here, we use km-scale, global cloud-resolving greenhouse warming simulations conducted with the coupled OpenIFS-FESOM2 model (AWI-CM3) to investigate how extreme rainfall and soil moisture characteristics in steep mountain regions change in response to greenhouse warming. Precipitation extremes, along with large-scale atmospheric dynamics, are analyzed across different slope angles to diagnose orographic lifting and convective enhancement mechanisms. Our findings reveal a pronounced increase in high-intensity precipitation on slopes steeper than 30°, particularly in the Himalayas and the Andes, with significant implications for future rain-induced landslides. This increase is primarily driven by thermodynamic changes rather than by relatively weak upslope motion. By using high-resolution (9 km) and higher-resolution (4 km) simulations, we provide a robust framework for enhancing global landslide hazard assessments in the context of climate change.
How to cite: Jadhav, J., Timmermann, A., Moon, J.-Y., Lee, S.-S., Streffing, J., and Jung, T.: Estimating future landslide hazards from km-scale greenhouse warming simulations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15932, https://doi.org/10.5194/egusphere-egu26-15932, 2026.
Precipitation-induced landslides are a major hazard worldwide, and their frequency and intensity are expected to rise under climate change, especially in the Alps, which are warming at twice the global average rate. This study reconstructs past landslide susceptibility trends in South Tyrol (Italy) from 1980–2020 using a data-driven model that integrates dynamic precipitation factors—both antecedent and triggering—alongside static terrain attributes. After addressing inventory incompleteness and spatial bias, the model estimates the expected daily landslide susceptibility at 30x30 meters spatial resolution, providing a baseline for climate impact assessments.
To explore atmospheric drivers, landslide susceptibility predictions were associated with the Jenkinson and Collison Weather Types classification scheme. Such synoptic classification was based on daily mean sea-level pressure data from NCAR/NCEP Reanalysis at 2.5º resolution, using a 16-grid-point configuration. Given the broad spatial influence of the weather types, landslide probability predictions were averaged over the entire South Tyrol region, allowing the analysis to focus exclusively on their temporal evolution.
Changes in landslide probability prediction, in relation to the reference period 1980-1995, were analysed seasonally (April to September and October to March). Results for each season were decomposed into frequency effects, capturing how changes in the occurrence of specific weather types affected the overall landslide susceptibility, and impact effects, quantifying how the susceptibility associated with particular weather types has changed over time.
Results show an increase in landslide susceptibility, with a clear seasonal shift toward later peaks in winter. The winter increase is predominantly impact-driven and is stronger in association with the southerly and cyclonic regimes, which carry warm, moist Mediterranean air, while the summer months display smaller increase, mostly associated with frequency changes.
Overall, the findings highlight that evolving atmospheric circulation—particularly enhanced susceptibility under moist advection regimes—rather than uniform shifts in circulation frequency, is intensifying landslide hazard. This underscores the need for adaptation strategies that account for changing hydro-meteorological conditions within circulation patterns, especially during the cold season.
How to cite: Zennaro, B., Lemus-Canovas, M., Pittore, M., Zebisch, M., Steger, S., and Comiti, F.: Reconstructing landslide probability trends in the Alps: the role of atmospheric circulation patterns, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19122, https://doi.org/10.5194/egusphere-egu26-19122, 2026.
The evolution of future rainfall regime (intensity, frequency, season) induced by climate change is likely to change the intensity and frequency of hydro-meteorological induced hazards. Several studies already suggest that the frequency of landslide occurrence should increase with climate change. In this context, the quantification of the local evolution of the rainfall triggering conditions constitutes a key step.
In this study, we detect and analyse landslide-prone rainfall events in an ensemble of 15 climate model simulations dynamical downscaled and bias-corrected at a 8km resolution and quantify their changes over the period 2006-2100. Three greenhouse gas emission scenarios (or Representative Concentration Pathways) are analysed: RCP2.6, RCP4.5, and RCP8.5. A statistical analysis is conducted to identify predominant trends across models, applied to the 23 mountainous massifs of the French Alps at different altitudes.
Our results highlight contrasted evolutions depending on the massif, altitude, season and scenario. In the northern and western Alpine massifs, our projections suggest a significant increase of the annual frequency of landslide-prone events, which is further pronounced under high GHG emission scenarios. These changes are also found for the southern, with a lesser magnitude, however. The extreme trends are also significantly increasing. This is particularly true for the Northern massifs and for high altitudes. The cumulative rainfall associated with the landslide-prone events clearly shows some differences between North and South of the Alps, with a higher increase of cumulative rainfall for extreme events in the South than in the North. These future evolutions also exhibit a clear seasonal dependence, with more pronounced changes in winter and spring. Our findings provide a scientific basis for guiding adaptation strategies in mountainous regions.
How to cite: Bernardie, S., Thieblemont, R., Vanderhagen, A., and Boucard, A.: Investigating the Impact of Climate Change on Landslide activity in the French Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7874, https://doi.org/10.5194/egusphere-egu26-7874, 2026.
Tree-ring series serve as an archive of past landslide movements. Dendrogeomorphological approach is a powerful method for estimating the timing of landslide events. This study applies a multi-proxy dendrogeomorphological approach—including abrupt growth changes-based growth disturbance, stem scar recovery, tree-ring eccentricity, and the establishment age of shade-intolerant trees—to evaluate and complement historical records of landslide activity at the Kamitokitozawa landslide in Akita Prefecture, Japan. Tree-ring analyses from 25 tree-ring cores, 18 disks, and 6 shade-intolerant trees revealed landslide signals during 1997–2022. The multi-proxy dataset also clarified spatial differences in slope deformation, with stem scar recovery, establishment age of shade-intolerant trees, and abrupt growth changes capturing discrete episodes of landslide scarp enlargement, while tree-ring eccentricity, stem scar recovery, and the establishment age of shade-intolerant trees highlighted enlargement internal landslide body movement. The estimated landslide signals were compared against a historical landslide chronology derived from geological surveys, mining records, and forest road construction data. The comparison showed that dendrogeomorphological proxies not only matched the timing of landslide activity documented in the historical chronology but also revealed additional periods of slope movement that were not recorded in existing archives. Moreover, the presence of older geomorphic features such as buried wood fragments suggests that landslide activity may have occurred prior to the dendrochronological window, possibly linked to volcanic and seismic events.
How to cite: Kawakami, R., Tsou, C.-Y., Ishikawa, Y., Ogita, S., Hayashi, K., Kuriyama, D., and Ito, K.: Verification and complementing of historical landslide records using multi‑proxy tree‑ring analyses at the Kamitokitozawa landslide, Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16445, https://doi.org/10.5194/egusphere-egu26-16445, 2026.
In Joetsu City, Niigata Prefecture in Japan, the Gampei landslide is located in a heavy-snowfall area, where snow depth can exceed 5 m in heavy snow season. In this regions, the influence of snow cover on landslide activity has not yet been fully clarified. This study investigates the factors controlling landslide motion during the snow-covered season at the Gampei landslide in a heavy-snowfall area. Field observations included continuous monitoring of displacement using GNSS surveys and vertical extensometers, as well as measurements from pore water pressure gauges, groundwater level loggers, soil moisture sensors, ground temperature sensors, and time-lapse cameras for snow depth. In addition, surface deformation was analyzed using LiDAR surveys conducted with an unmanned aerial vehicle (UAV).
The results indicate that pore water pressure and groundwater level remain high and stable with small fluctuations from the snow-covered period through the snowmelt season. In contrast, during snow-free periods, both parameters respond to rainfall and show rapid fluctuations, particularly in summer. These observations suggest that soil saturation induced by continuous autumn rainfall is maintained by snow cover, creating hydraulic conditions favorable for landslide movement during winter. Such conditions are more easily sustained during winter, resulting in larger displacement.
Furthermore, in winters with low snow accumulation, a rapid rise in groundwater level was observed during the snowmelt period compared to heavy snowfall years. During winter, however, no clear increase in pore water pressure associated with groundwater level rise was detected, indicating that groundwater level and pore water pressure may be governed by different processes during the snow-covered period.
How to cite: Sakai, T., Narama, C., Inouoe, Y., Wang, J., and Tatsuta, E.: Seasonal variations in groundwater level and pore water pressure at the Gampei landslide, Joetsu City, Japan, a heavy-snowfall area, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16787, https://doi.org/10.5194/egusphere-egu26-16787, 2026.
Earthquake-induced landslides are a primary driver of surface distribance in alpine canyon regions, exerting long-lasting impacts on vegetation dynamics. This study investigates landslides triggered by the 2017 Ms 6.9 Milin earthquake in the Yarlung Zangbo Grand Canyon. Getis-Ord Gi* analysis was used to delineate the spatial extent of vegetation disturbance, while the Vegetation Damage Area (VDA) and Vegetation Recovery Rate (VRR) indices derived from multi-temporal NDVI data were used to quantify vegetation disturbance intensity and identify the temporal evolution of vegetation recovery. Results indicate that landslide activity persisted for several years post-seismic, with the total number of landslides increasing by 142 and the cumulative landslide area expanding by 21.49 km². Vegetation degradation was not confined to mapped landslide polygons; the most pronounced negative effects extended 20-30 m beyond landslide boundaries, forming a highly sensitive belt of severe vegetation damage. From 2017 to 2023, the VDA consistently accounted for over 50% of the newly triggered landslides areas, peaking at 97.54% in 2017. Although the VRR indicates an overall recovery trend, most affected regions have yet to return to pre-earthquake conditions, with more severely disturbed areas exhibiting significant recovery lags. These findings highlight the prolonged evolution of earthquake-triggered landslides and their sustained influence on alpine ecosystems, providing quantitative evidence to support ecological restoration and long-term geohazard management.
How to cite: Zhao, B. and Yang, L.: Vegetation damage and recovery characteristics of landslides triggered by earthquake in the Yarlung Zangbo Grand Canyon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3426, https://doi.org/10.5194/egusphere-egu26-3426, 2026.
Landslide monitoring plays an important role to reduce risk for communities and infrastructures within areas affected by slope instability. In this study, we utilize high resolution thermal and RGB data acquired by using drone camera to detect surface temperature variations and identify potential precursory indicators of landslide. The proposed approach is applied to two different landslide case studies, the Montaguto earthflow in the Apennines and the Melendugno rockfall along the Apulian coastline, in southern Italy. Seasonal surveys were conducted to capture temporal changes in surface thermal patterns, enabling the detection of anomalous temperature zones that may indicate early slope movement. The primary tool to detect such surface temperature anomalies is thermal imagery, whereas an RGB image is used to validate thermal observations and provide more detailed data on slope morphology, cracks, vegetation and other topographic features. The combination of thermal and RGB data allows for a comprehensive analysis, correlating surface thermal anomalies with geomorphological features to enhance the reliability of detected precursors. Repeated thermal surveys, both in the summer and winter seasons, provide an insight to interpret the conditions and morphology of the surface to evaluate landslide susceptibility in the study areas. This technique, therefore, provides high resolution thermal information that can improve the ability to monitor landslide risk zones and can be used as an effective tool for an early warning system in landslide-prone regions.
How to cite: Niaz, J., Lollino, P., Parise, M., Scaringi, G., and Cagnazzo, C.: Surface Temperature Patterns as Indicators of Slope Instability: the Montaguto Earthflow and the Melendugno Rockfall Case Studies, Southern Italy , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7260, https://doi.org/10.5194/egusphere-egu26-7260, 2026.
Rockfalls and slides pose significant hazards in open-pit mines; however, widely adopted tools for non-contact geomaterial characterisation and slope monitoring are still lacking.
This study investigates the application of unmanned aerial vehicle-mounted thermal infrared cameras (UAV-IRT) for observing, detecting, and inferring material parameters in active surface mining environments. A multitemporal UAV‑IRT campaign was conducted to acquire thermal imagery across the full diurnal temperature range, from daily maxima to minima. Results from the thermal images collected at the Jezeří open-pit mine in Czechia showed that cooling indices can be used to estimate material properties, such as porosity, demonstrating strong potential for integration into geotechnical slope-design systems.
On the one hand, the analysis also highlights limitations, particularly when target features receive intense solar radiation, which can reduce the reliability of parameter detection. On the other hand, UAV-based infrared thermography is shown to be a practical tool for characterising surface materials in areas affected by mass wasting—a step toward the development of automated material‑parameter detection algorithms, applicable to both artificial and natural slopes, with the overarching goal of improving safety.
How to cite: Loche, M., Chowdepalli, B., Racek, O., Klimeš, J., Blahůt, J., and Scaringi, G.: UAV‑Based Infrared Thermography for Characterising Unstable Slopes in a Mining Area, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4213, https://doi.org/10.5194/egusphere-egu26-4213, 2026.
Our research investigates the complex thermo-mechanical coupling within landslide shear zones, specifically focusing on how temperature variations influence the residual shear strength of clayey soils. This parameter is a critical determinant for the stability of reactivated, slow-moving landslides.
In our laboratory investigations, we utilised a modified ring-shear apparatus equipped with a temperature-control system to conduct heating-cooling cycles (typically between 20 °C and 70 °C) on various soil samples. We have tested materials ranging from low-plasticity mountain soils to high-plasticity marls and bentonites. Our findings reveal that the thermal response of soil is sensitive to both mineral composition and rate of shearing.
Regarding slope modelling, we developed numerical frameworks, utilising finite-element analysis, that incorporate temperature-dependent failure criteria. By simulating scenarios from the 1960s to the 2060s based on historical and projected climate data, our results suggest that gradual ground warming may increase the factor of safety in certain clay-rich slopes, potentially transitioning active landslides into long-term dormancy. We also quantified the nonlinear coupling between temperature variations and groundwater table fluctuations, demonstrating that their combined impact on stability is more significant than the sum of their individual effects.
Our field monitoring and regional activities involved extensive sampling at disaster-prone sites and the calibration of thermal parameters using historical meteorological data to accurately reproduce ground temperature profiles. Furthermore, we have implemented spatial probability analyses at a national scale, utilising soil composition and topographic data to map expected changes in slope stability under global warming scenarios.
In the future, we plan to incorporate the soil-vegetation-atmosphere nexus into our framework. By evaluating how vegetation and root systems modulate heat and moisture fluxes, we should be able to capture the thermo-mechanical behaviour of the shallow subsurface more accurately. Additionally, we intend to expand our experimental investigations to a broader range of soil compositions and refine testing protocols to objectively assess the thermal sensitivity of landslide-prone formations.
How to cite: Scaringi, G., Klimeš, J., Balek, J., Blahůt, J., Chowdepalli, B., Das, S., Dhakal, O. P., Hartvich, F., Jerman, J., Kadlíček, T., Loche, M., Mladý, T., Moniaci, R. M., Nguyen Duy, M., Racek, O., and Roháč, J.: Thermo-mechanical coupling in landslide shear zones: from laboratory characterisation to slope-scale modelling under climate change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9910, https://doi.org/10.5194/egusphere-egu26-9910, 2026.
On 3 April 2024, Mw 7.4 earthquake struck Hualien County. A total of 779 landslides were recorded following the earthquake, affecting 433.93 hectares. So, when excessive rain courtesy of Typhoon Wipha arrived in July, which triggered a landslide blockading a flushed Matai’an creek. The resulting 200-meter-tall barrier lake could hold up to 86 million cubic meters of water, and intense rainfall brought by super typhoon Ragasa triggered the overtopping of the landslide dam at Matai’an in Taiwan on 23 September 2025. The flood resulted in 19 deaths. From the disaster zone, 717 were rescued, 157 injured, and 5 remain missing. Over 8,000 people encompassing 3 villages were directly impacted by this incident. In certain parts of Guangfu, the receding waters left behind sludge up to 2 meters deep. What happened in Guangfu Town is a significant compound disaster example. It challenges the present warning, forecasting and response system of debris flow. New concepts and new procedures are necessary to cope with the compound disasters triggered by extreme heavy rainfall.
The remote location of the landslide dam and the lack of road access, as well as the soft soil and rocks of the dam body, and ongoing landslides in the surrounding area all pose difficult restrictions. In addition, the risks of typhoons, heavy rainfall, and earthquakes all need to be taken into consideration. All of these factors make machinery access to the construction site very difficult and highly hazardous. The government had installed rain gauges, water gauges, and CCTV surveillance cameras around the dam area. These are linked to the downstream water level station and surveillance images of the river to keep abreast of the latest conditions at all times. However, due to the steep terrain of the dam crest, the lack of access roads, and mountainous climate conditions, the installation of the instruments has proved challenging. The rainfall hydrograph shows long-duration, high-intensity, high-accumulation and large-extent characteristics. It suggests the correlation of each disaster type with the rainfall characteristics by reference to the report of eyewitness memory. The causality between those in Guangfu Town occurred disasters could then be deduced. In order to characterize the disaster and suggest a strategy, it is necessary to try to rebuild the temporal order and spatial distribution of the disaster processes.
This study describes briefly each single disaster, the relationship among those disasters and the approach to rebuild the disaster process by field investigation, topographic survey and satellite image processing. The results serve to intensify the disaster prevention system of debris flow and shallow landslide which then could be applied to the warning system of deep-seated landslide and landslide dam. The derivative issues and the approach to compound disaster prevention are suggested. The related discussions, evaluation and assessment are also summarized as the reference of further tasks.
How to cite: Lai, W.-C., Lee, S.-P., and Tsang, Y.-C.: Investigation of catastrophic deep-seated landslides and landslide dams in Taiwan ~ Lessons from Matai'an landslide dam disaster, 23rd Sep. 2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6905, https://doi.org/10.5194/egusphere-egu26-6905, 2026.
Despite extensive literature on the effectiveness of drainage systems and documented cases of landslides linked to leaking and burst pipes, malfunctioning drainage systems are rarely incorporated into hazard modelling. Porewater pressure is a major control of landslides, commonly managed through the installation of drainage systems. Paradoxically, such an intervention can act as a landslide driver rather than a mitigation measure. Malfunctioning drainage systems and burst pipes may disrupt slope hydrological connectivity and, in some cases, lead to oversaturation, thereby elevating localized pore water pressure. This study aims to quantify in data scarce regions, through numerical simulations, the influence of malfunctioning drainage systems on landslide dynamics, from initiation to propagation.
The complex Hofermühle landslide in Lower Austria is an illustrative case of the interplay between natural and anthropogenic processes. Previous activities of this landslide and its proximity to a stream have led to the installation of subsurface drainage for decades to dewater the hillslope. We develop a landslide conceptual model of a mudflow event that occurred on 21 April 2013 using long-term monitoring data, residents' reports, 2D seepage and slope stability analyses, and propagation modelling (r.avaflow). The seepage and slope stability analysis demonstrates that the malfunctioning drainage scenario is the most plausible trigger of the reported landslide event.
Our results indicate that a drainage capacity of less than 40% and an antecedent malfunction of at least 68 days before failure were likely factors in the 2013 landslide. The mudflow results from sufficient water storage, localized porewater pressures, seepage emergence, and, thus, slope failure which transformed into a flow. The preliminary propagation analysis showed that a minimum volume of 100 m-3 is necessary to propagate the initial landslide mass downstream. Our findings suggest that abandoned drainage infrastructure may play a crucial role in landslide occurrences. The backward simulation is a demonstrative example of a process that may become increasingly important as projected future urbanization and associated hillslope modifications unfold.
How to cite: Jiménez Donato, Y. A., Bogaard, T., Mergili, M., Ozturk, U., Marr, P., and Glade, T.: Impact of malfunctioning drainage systems on landslide initiation and propagation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10691, https://doi.org/10.5194/egusphere-egu26-10691, 2026.
Abstract
An extreme rainfall event affected the mountainous area of the Tzoumerka Mountains (NW Greece) during 18–22 November 2025, with cumulative precipitation exceeding 1000 mm on a monthly basis. This exceptional hydrometeorological episode was characterized by prolonged and high-intensity rainfall and triggered widespread slope instabilities across a geomorphologically complex and tectonically active region. Numerous failures were recorded, impacting settlements, road infrastructure, and retaining structures within the Municipality of North Tzoumerka, causing significant disruption to local communities and transport networks.
This study presents the results of detailed post-event field surveys and an integrated engineering geological assessment of rainfall-induced landslides developed primarily within flysch formations and their associated weathered mantles. The investigated area is characterized by steep slopes, thick weathering profiles, and heterogeneous lithological conditions, which strongly influence slope stability under extreme hydrological loading. The observed failure mechanisms include shallow translational landslides, debris and mud flows, surface erosion phenomena, and failures of retaining structures, often occurring in close spatial association.
Particular emphasis is placed on the hydrogeological conditions governing slope instability. Field evidence indicates the development of temporary perched groundwater within the weathered mantle and along permeability contrasts between permeable colluvial deposits and the underlying low-permeability flysch formations. These conditions promoted rapid infiltration, accumulation of subsurface water, and limited drainage capacity, leading to critical pore-water pressure build-up during the rainfall event.
Field observations and qualitative assessments suggest that prolonged and intense rainfall resulted in a rapid increase in pore-water pressures, reduction of effective shear strength, and progressive degradation of slope stability. In several locations, anthropogenic factors significantly aggravated slope instability, including inadequate surface drainage systems, road excavations that altered natural slope geometry, and retaining structures founded on weathered or poorly characterized materials.
The results highlight the high susceptibility of flysch-dominated terrains to extreme precipitation events and underline the critical role of coupled hydrogeological and engineering geological processes in landslide initiation and evolution. The study emphasizes the importance of post-event field investigations for understanding failure mechanisms and supports the need for integrated hazard assessment, improved drainage design, and targeted mitigation strategies in mountainous regions increasingly exposed to extreme rainfall conditions under a changing climate.
How to cite: Gkountoulas (Gudulas), K., Paschos, P., and Makri, K.: Rainfall-Induced Landslides in Flysch-Dominated Terrains of the Tzoumerka Mountains (NW Greece): A Post-Event Engineering Geological and Hydrogeological Assessment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1766, https://doi.org/10.5194/egusphere-egu26-1766, 2026.
