NH3.4

Impact of climate change on landslides and soil erosion: the role of precipitation, temperature, and land use

Global warming is unequivocal: the frequency and intensity of heavy precipitation events increased since the mid-20th century in all regions in which observational data were sufficient for trend analysis. And heavy precipitations and related effects are projected to intensify and be more frequent in most regions.
In this framework, particular attention should be paid to all the ground events triggered by rainfall, among which landslides and soil erosion.
Changes in temperature also have been shown to affect the hydraulic and mechanical behavior of soils and rocks in multiple ways, suggesting the importance of monitoring and modelling thermal variables alongside the hydraulic ones.
The influence of climate variables on the triggering, frequency, and severity of slope failures and soil erosion can be different according to the area, the time horizon of interest, and the specific trends of weather variables. Similarly, land use/cover change can play a pivotal role in exacerbating or reducing such hazards.
Thus, the overall impacts depend on the region, spatial scale, time frame, and socio-economic context addressed. However, even the simple identification of the weather patterns regulating the occurrence of such phenomena represents a not trivial issue, also assuming steady conditions, due to the crucial role played by geomorphological details. To support hazards’ monitoring, predictions, and projections, last-generation and updated datasets with high spatio-temporal resolution and quality - as those from the Copernicus Services’ Portals - are useful to feed models, big-data analytics, and indicators’ frameworks enabling timely, robust, and efficient decision making.
The Session aims at presenting studies concerning ongoing to future analysis on the impact of climate change on landslide triggering and dynamics, and soil erosion hazard, across different geographical contexts and scales. Either investigations including analyses of historical records and related climate variables, or modeling approaches driven by future climate exploiting downscaled output of climate projections are welcome. Studies assessing variations in severity, frequency, and/or timing of events and consequent risks are valuable.
Moreover, a focus on all aspects of landslide thermo-hydro-mechanics, from experimental studies to field and remote-sensing monitoring, from microstructural analyses to geomechanical modelling at various spatial and temporal scales, is proposed.

Co-organized by CL3.2/SSS2
Convener: Stefano Luigi GarianoECSECS | Co-conveners: Guido Rianna, Monia Santini, Alfredo RederECSECS, Séverine Bernardie, Gianvito ScaringiECSECS, Luigi LombardoECSECS, Carolina Segui
Presentations
| Wed, 25 May, 08:30–11:46 (CEST)
 
Room 1.34

Presentations: Wed, 25 May | Room 1.34

Chairpersons: Guido Rianna, Alfredo Reder, Stefano Luigi Gariano
08:30–08:33
08:33–08:34
08:34–08:41
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EGU22-8302
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Virtual presentation
Niamh Cullen and Mary Bourke

Globally landslides are triggered by a myriad of singular and complex causes however the response of the Irish landscape to predicted climate changes are unknown. Some limited data suggest that there may be an increasing trend observed in the frequency of landslides in Ireland, clustered around specific high magnitude rainfall events. Whether this trend is associated with a changing climate trend is unclear. None of the several peer reviewed compendiums that include regional landslide studies and climate have a dedicated contribution on Irelands landscape. We provide a summary of the climate of Ireland from Holocene to future modelled predictions. We present a qualitative assessment of the role of Irish climate and climate change on landslides by identifying specific climate aspects which are important for slope instabilities including precipitation receipts, intensity and variability; the tracks of storms and other rain bearing weather systems and temperature changes. We examine published case studies and an inventory of known landscape response to past weather to consider, qualitatively, the likely response of landslides to predicted future climate trends. We also present rainfall data for three recent landslides events in Ireland and identify areas that require further landslide research. Our review finds that climatic factors which are predicted for Ireland, are cited in the published literature as contributors to slope failures in the Irish landscape. Analysis of rainfall data for the three recent slope failures further support this. Our review suggests that Ireland may see an increase in the frequency of landslide occurrence in the future. Although the data suggests that the majority of failures occur in peat, we highlight a paucity of data for coastal slope failures.  

How to cite: Cullen, N. and Bourke, M.: The potential impact of predicted climatic change on future slope stability in Ireland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8302, https://doi.org/10.5194/egusphere-egu22-8302, 2022.

08:41–08:48
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EGU22-2681
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On-site presentation
Katrin M. Nissen, Uwe Ulbrich, and Bodo Damm

In this study we assess the influence of changes in the relevant meteorological conditions on the probability for rockfall in German low mountain regions. The study is based on data from a rockfall data base for Germany (Rupp and Damm, 2020) and a data set supplied by the Deutsche Bahn (German railway company) covering the periods 1838-2018 and 2015-2020, respectively. 

In a first approach, a logistic regression model for the probability of rockfall at a given location developed by Nissen et al. 2021 was applied to gridded meteorological station observations (RADOLAN and EOBS) ranging from the year 1950 to 2019. The logistic regression model quantifies the influence of daily precipitation, a proxy for pore water and freeze-thaw cycles on rockfall probability. A probability forecast was made for each day and location. The day-to-day variability in rockfall probability at the individual sites is high. Thus, the sign of the trends is site specific, but the majority of sites is showing a negative trend over the 70-year period investigated. The significance of the trends at most sites is below the 95% level. Sites at which the trend is statistically significant almost all show a negative trend, down to -4% per decade in terms of the annual number of days with a higher than climatological hazard. The mean probability decreased by as much as -2.3% per decade. 

The second approach is based on large-scale weather patterns. An analysis identified 3 weather pattern that occur on average at 9% of all days but include  19% of the days on which a rockfall event occurred. The trend in the number of these patterns was determined for the last 40 years. It suggests a decrease by -2.2% per decade and is not statistically significant. 

How to cite: Nissen, K. M., Ulbrich, U., and Damm, B.: A decrease in rockfall probability associated with changing meteorological conditions in Germany, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2681, https://doi.org/10.5194/egusphere-egu22-2681, 2022.

08:48–08:55
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EGU22-13399
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On-site presentation
Guido Rianna and Alfredo Reder

The study is aimed at verifying the reliability of the ERA5 reanalysis in reproducing histories of soil water fluxes exchanges (in terms of precipitation and evapotranspiration) leading to landslide events that actually occurred in Campania Region (Southern Italy). In the specific, the investigation deals with landslide events affecting pyroclastic covers result of repeated eruptions of Vesuvius and Campi Flegrei over the course of millennia. Indeed, for many events occurred in the last years, it is hard to retrieve continuous and reliable atmospheric data provided by weather stations in the vicinity of the affected slopes. Under such constraints, it could be difficult to identify the weather patterns triggering the events and then how they could vary in a climate change perspective. To deal with these issues, the fifth generation of atmospheric reanalysis made available by European Centre for Medium-Range Weather Forecasts (ECMWF) can represent a valuable support. ERA5 and its downscaling ERA5land return hourly data with an horizontal resolution of respectively 31km and 9 km over the entire globe. The data are available since Fifties and they are continuously updated with a delay of only 5 days for ERA5 and few months for ERA5land. Well-documented test cases over Campania Region for which long datasets of atmospheric data and details about the landslide events are available, are exploited to assess the capabilities of ERA5 reanalysis in reproducing antecedent and triggering soil water fluxes exchanges histories. Then, strengths and potential gaps are identified and thoroughly explained to permit a reliable adoption of the datasets.

How to cite: Rianna, G. and Reder, A.: Interpreting recent landslide events in Campania Region (Southern Italy) by using innovative approaches, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13399, https://doi.org/10.5194/egusphere-egu22-13399, 2022.

08:55–09:02
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EGU22-4314
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Virtual presentation
Joana Araújo, Alexandre M. Ramos, Pedro M.M. Soares, Raquel Melo, Sérgio C. Oliveira, and Ricardo M. Trigo

It is expected that landslide events will occur more frequently, throughout the century, as a direct consequence of climate change. The main triggering factor, over Portugal mainland, is extreme precipitation. Thus, the aim of this study relied on the assessment of the projected future changes in the extreme precipitation over Portugal mainland and quantifying the correlation between extreme rainfall events and landslide events through Rainfall Triggering Thresholds (RTT). This methodology was applied for two specific locations within two Portuguese areas of great geomorphological interest.

To evaluate the possible projected changes in the extreme precipitation, we used the Iberia02 dataset and the EURO-CORDEX models’ runs at a 0.11º spatial resolution. First, it was analyzed the models’ performance to simulate extreme values in the precipitation series. The simulated precipitation relied on RCM-GCM models’ runs, from EURO-CORDEX, and a Multimodel ensemble mean. The extreme precipitation assessment relied on the values associated to the highest percentiles, and to the values associated to the RTTs’ percentiles. To evaluate the possible future changes of the precipitation series, both at the most representative percentiles and RTTs’ percentiles, a comparison was made between the simulated values from EURO-CORDEX historical runs (1971-2000) and the simulated values from EURO-CORDEX future runs (2071-2100), considering two emission scenarios: RCP 4.5 and RCP 8.5. In the models’ performance, the Multimodel ensemble mean appeared to be within the best representing models. As for the projected changes in the extreme precipitation for the end of the century, when following the RCP 4.5 scenario, most models projected an increase in the extreme values, whereas, when following the RCP 8.5 scenario, most models projected a decrease in the extreme values.  

 

Acknowledgements

This work was financed by national funds through FCT–Portuguese Foundation for Science and Technology, I.P., under the framework of the project BeSafeSlide (PTDC/GES-AMB/30052/2017)

How to cite: Araújo, J., Ramos, A. M., Soares, P. M. M., Melo, R., Oliveira, S. C., and Trigo, R. M.: Landslide events in Portugal under future climate change scenarios, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4314, https://doi.org/10.5194/egusphere-egu22-4314, 2022.

09:02–09:09
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EGU22-2299
Keh-Jian Shou

Due to the impact of climate change, the increasing frequency of extreme rainfall events, with concentrated rainfalls, commonly cause landslide hazard in the mountain areas of Taiwan. Although the extraordinary rainfall behavior is critical for the geohazard, it is significantly affected by the factors such as topography, the route of typhoon, etc. Therefore, there are uncertainties for the predicted rainfall as well as the landslide susceptibilities.

This study employs rainfall frequency analysis together with the atmospheric general circulation model (AGCM) downscaling estimation to understand the temporal rainfall trends, distributions, and intensities in the adopted study area in Central Taiwan. The uncertainties within the rainfall prediction was investigated before applied to the landslide susceptibility analysis. The catchments in Taiwan, including Tachia River, Wu River, and Chuoshui River, were adopted as the study area. To assess the hazard of the landslides, logistic regression methods and supporting vector machines method were applied, in which the control factors were analyzed and discussed. The results of predictive analysis with the consideration of uncertainties can be applied for risk prevention and management in the study area.

How to cite: Shou, K.-J.: Impact of Climate Change on Landslide Susceptibility – for the Case in Taiwan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2299, https://doi.org/10.5194/egusphere-egu22-2299, 2022.

09:09–09:16
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EGU22-2507
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ECS
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On-site presentation
Silvia Puliero, Sansar Raj Meena, Filippo Catani, and Mario Floris

Frequent and extreme meteorological events can lead to an increase in landslide hazard. A multi-temporal inventory plays an essential role in monitoring slope processes over time and forecasting future evolution. In recent years, the province of Belluno (Veneto Region, NE Italy) was affected by two relevant and intense meteorological phenomena that occurred on October 27-30, 2018 (i.e. windstorm Vaia) and on December 4-6, 2020. Both events were characterized by heavy rainfall of up to 600 mm in 72 hours, triggering widespread landslides throughout the area. The analyses conducted on some local rain gauges in the sectors most affected by each storm show very high return periods (over 100 years) for both events, even though they occurred in a two-year time frame. This study aims to evaluate whether these strong meteorological phenomena are characterized by an increase in their frequency in the province of Belluno and to see what influence they have on slope instabilities, which are important for assessing landslide risk. The rainfall data available since 1950 have been investigated through statistical analysis to achieve these goals. The spatial and temporal evolution of slope instabilities has been examined through remote sensing techniques to compare landslides triggered in 2018 and 2020 with past instability phenomena in the same area. The results show the importance of multi-temporal databases for landslide hazard assessment after extreme meteorological events at the regional scale.

How to cite: Puliero, S., Meena, S. R., Catani, F., and Floris, M.: Impact of multi-temporal landslide inventories on landslide hazard assessment: a case study in the province of Belluno (Veneto Region, NE Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2507, https://doi.org/10.5194/egusphere-egu22-2507, 2022.

09:16–09:23
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EGU22-13409
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On-site presentation
Helen Brooks, Ross Stirling, Anthony Blake, Jessica Holmes, Zelong Yu, Arnaud Watlet, James Whiteley, Kevin Briggs, Alister Smith, Paul Hughes, Joe Smethurst, Jonathan Chambers, and Neil Dixon

Long-life, long linear geotechnical assets such as road, rail and flood embankments provide vital transport and flood defence infrastructure. Slope failures can close transport networks and cause delays, or can reduce the protection provided against flood hazards. This creates huge economic cost and can cause a risk to life for those using affected transport networks or resident on the floodplain. Where emergency repair is needed, the estimated cost of this is 10 times that of scheduled maintenance making effective asset management an industry priority (Glendinning et al., 2009).

However, projected climatic changes pose a threat to the stability of these assets. The most recent IPCC report highlighted projected future changes to temperatures and rainfall. These climatic changes alter the natural cycles of wetting and drying experienced by assets, which results in deterioration of asset performance. Deterioration can occur due to a variety of processes, including crack formation and propagation, downslope plastic strain accumulation and geochemical or mineralogical changes. These ultimately influence the strength, stiffness, permeability and water retention of the soil, which can often mean the construction standard of the asset is not maintained (Stirling et al., 2021).

The ACHILLES project aims to improve understanding of how these processes occur and how they may be affected by projected climatic change. Here, we introduce three large-scale field monitoring sites, including a purpose-built trial embankment, flood embankment and highway cutting. These assets are heavily instrumented to measure soil deformation, soil hydrology and local weather conditions, amongst others. Data from these sites are analysed to further understand deterioration processes and inform future design, construction, monitoring and management of these earthworks. We will discuss key insights from this project, including implications for stakeholders.

References:

Glendinning S, Hall J, Manning L (2009) Asset-management strategies for infrastructure embankments. Proc Inst Civ Eng Eng Sustain 162:111–120

Stirling RA, Toll DG, Glendinning S, Helm PR, Yildiz A, Hughes PN, Asquith JD. Weather-driven deterioration processes affecting the performance of embankment slopes. Géotechnique 2021, 71(11), 957-969.

How to cite: Brooks, H., Stirling, R., Blake, A., Holmes, J., Yu, Z., Watlet, A., Whiteley, J., Briggs, K., Smith, A., Hughes, P., Smethurst, J., Chambers, J., and Dixon, N.: Climate-driven deterioration of long-life, long-linear geotechnical infrastructure, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13409, https://doi.org/10.5194/egusphere-egu22-13409, 2022.

09:23–09:30
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EGU22-7465
Douglas Maraun, Raphael Knevels, Aditya N. Mishra, Heimo Truhetz, Emanuele Bevacqua, Herwig Proske, Giuseppe Zappa, Alexander Brenning, Helene Petschko, Armin Schaffer, Philip Leopold, and Bryony L. Puxley

Landslides are a major natural hazard, but uncertainties about their occurrence in a warmer climate are substantial. The relative role of rainfall, soil moisture, and land-use changes and the importance of climate change mitigation are not well understood.  Here, we develop and apply a storyline approach to address these issues, considering a severe event from June 2009 in Austria with some 3000 landslides as showcase. The approach leverages on convection permitting simulations that realistically represent the meteorological event while sampling uncertainties.  Depending on the changes of rainfall and soil moisture, the area affected during a 2009-type event could grow by 45% at 4 K global warming, although a slight reduction is also possible. Such growth could be reduced to less than 10% by limiting global warming according to the Paris agreement. Anticipated land-use changes towards a climate resilient forest would fully compensate for such a limited increase in hazard.

How to cite: Maraun, D., Knevels, R., Mishra, A. N., Truhetz, H., Bevacqua, E., Proske, H., Zappa, G., Brenning, A., Petschko, H., Schaffer, A., Leopold, P., and Puxley, B. L.: A severe landslide event in the Alpine foreland under possible future climate and land-use changes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7465, https://doi.org/10.5194/egusphere-egu22-7465, 2022.

09:30–09:37
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EGU22-11120
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ECS
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On-site presentation
Davide Danilo Chiarelli, Giovanni Martino Bombelli, Daniele Bocchiola, Renzo Rosso, and Maria Cristina Rulli

Shallow landslides (SLs) imply downhill movements of soil, rocks, debris. These typically occur on steep terrains, in mountainous, and hilly areas, representing a major risk for people and infrastructures. Properly mapping of shallow landslides in space and time is fundamental for prediction, forecast, and setting up of countermeasures. However, modelling of shallow landslides is complex, given (very) local nature of the phenomenon. Recently investigation started about the role of snow melt in triggering shallow landslides, displaying increasing evidence of catastrophic events at thaw. Little was done hitherto in modelling snow melt triggered SLs, especially in terms of physically based modeling. Under the umbrella of the recent project MHYCONOS, funded by Fondazione CARIPLO of Italy, we developed a robust, and parameter-wise parsimonious model, able to mimic triggering of SLs accounting for the combined effect of precipitation duration and intensity, and snowmelt at thaw. In our model, when temperature is below 0 °C, precipitation is stored as snowpack on the soil surface, and released later in thaw season. Storage of melting water during springtime increases soil moisture, so creating potential for SLs. The model is demonstratively applied to the Tartano river valley, in the Alps of Lombardia region of Italy. In this region mass movements and flash-floods in the wake of intense storms are common. Currently from our model about 26% of the Tartano valley displays (permanent) unstable conditions, more than 40% of it influenced by soil moisture changes. Conversely, by applying a traditional rainfall-based analysis, only 19% of the basin is predicted as potentially unstable, mainly in fall, when intense rainfall occurs. When including snowmelt as a cause of SLS triggering, one finds anticipation of the (modeled) peak of instability to springtime, during April and May. Forcing the model under 6 different climate change scenarios of IPCC at 2050, and 2100, an increase is expected in temperature (i.e. with rapider snow melt), and extreme precipitation events, further aggravating SLs hazard. Mapping zones prone to instability in space and time under present conditions, and future scenarios, will help to prevent casualties, and damages in the short-term, while providing base for structural mitigation measures in the long term, during periods of potential instability, even at low to medium rainfall rates.

How to cite: Chiarelli, D. D., Bombelli, G. M., Bocchiola, D., Rosso, R., and Rulli, M. C.: Snow melt triggering of shallow landslides under climate change. The case study of Tartano valley, Italian Alps., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11120, https://doi.org/10.5194/egusphere-egu22-11120, 2022.

09:37–09:38
09:38–09:45
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EGU22-8247
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On-site presentation
Laura Longoni, Lorenzo Panzeri, Michele Mondani, and Monica Papini

The frequency and intensity of heavy precipitation events increased since the mid-20th century and, considering the climate crisis, it is important also to analyze the effects of processes and events that lead to faster snow mantle melting cycles in mountain areas.

Shallow landslides are induced by extreme hydrological events such as the occurrence of short and intense rainfall or by events of medium intensity but prolonged over time. Such slips involve generally reduced portions of land both in area and in thickness, however, they are dangerous due to the absence of warning signals and the lack of knowledge regarding their possible evolution.

This work deals with the experimental study of these landslides through the laboratory simulations on a small-scale slope, reproduced at the LIMAG Lab - Laboratory of mountain hydraulics and applied geology of the Lecco Campus and in situ seasonal processes observation at a mountain closed basin nearby Champoluc village in Aosta Valley region.

The central objective is to study the evolution of shallow landslides in reduced scale caused by external factor as snowmelt and rainfall and to compare the observations done in laboratory with the ones in situ. In order to investigate the behaviour of shallow landslides in these critical conditions, a series of sensors have been installed on the simulator. This technology includes three modified pressure transmitters for the pore water pressure evaluation which have been accompanied by other support instrumentation consisting of GoPro’s cameras, TDR (Time Domain Reflectometry) and georesistivimeter; all of them provide a cross check of phenomena processes.

Throughout the downscaled simulations with snow cover it was possible to observe several processes. The direct interaction between snow and ground does not favor the infiltration of a large amount of water. The protective role of snow lies in keeping the first film of soil at 0 degrees and loading the soil by decreasing its infiltrative capacity; this no longer occurs when the water melted by the snow flows downstream and begins to infiltrate into uncovered and warmer soils. Without thermal or overload barriers, the water pours into the ground. Therefore, a potential susceptible area can be the subject of different filtering and infiltrative contributions from upstream, saturating quickly and collapsing.

These laboratory experiments are the starting point for the in-situ analyses and provide a comparison with the observations made by means of ad hoc instrumentation set up at the Champoluc station. Highly detailed information is obtained concerning the density and thickness of the snowpack during seasonal processes. These contribute to defining the hydrogeological processes within the terrain, already studied in the laboratory, and to establishing the water balance.

How to cite: Longoni, L., Panzeri, L., Mondani, M., and Papini, M.: Experimental analysis of seasonal processes in shallow landslide in a snowy region through downscaled and in situ observation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8247, https://doi.org/10.5194/egusphere-egu22-8247, 2022.

09:45–09:52
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EGU22-8176
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ECS
Unnur Blær A. Bartsch, Guðrún Gísladóttir, and Harpa Grímsdóttir

Permafrost is perennially frozen ground occurring in about 24% of the exposed land surface in the northern hemisphere. The soil categorized as permafrost is named cryosol (or gelisol). Cryosol is widely spread in the Arctic, where it is continuous in the polar regions while in the sub-arctic it is discontinuous or sporadic. Iceland is located on the edge of the Arctic, and therefore permafrost can be found in many regions of the island. In addition, the frost effect is great, due to the unique climate and weather conditions and the high sensitivity of the Icelandic soil (volcanic soil – andosol). Although the distribution of permafrost is widespread it is in many respects dependent on the weather. As the climate warms, as it does now, the permafrost retreats rapidly, causing major changes in the earth’s surface. These changes can be accompanied by various dangers. In Iceland the retreat of permafrost in high mountains has led the top slopes to become unstable, leading to increased risk of landslides and similar hazards. In this project, permafrost in Iceland will be examined, more specifically the areas where permafrost is considered to be thawing and the dangers that accompany that thawing. The research area is by Strandartindur mountain in Seyðisfjörður. On the slope of Strandartindur is a rock glacier, which is in motion, but it is believed that permafrost is hidden in the ground beneath. The area is a well-known landslide area, where the source of landslides high up in Strandartindur is thick sediments that are partly considered permafrost or rock glaciers. Rock glaciers and thawing of permafrost in the vicinity and/or in the glacier threaten settlements in the area, due to landslides. This will be a threefold multidisciplinary project where aspects of natural hazards and society will be tied together; (i) data from soil thermometers and InSAR data will be examined, (ii) discussed and examined how permafrost can be included in monitoring, (iii) and how information on the dangers associated with permafrost can be disseminated to residents and the general public. The project will be useful for monitoring the hazard area at Strandartindur, while also for monitoring comparable areas in the country. It is hoped that the product of this project will be a monitoring research proposal. The result will show how best to measure permafrost, how best to monitor its thawing and how best to provide information to residents and the general public.

How to cite: A. Bartsch, U. B., Gísladóttir, G., and Grímsdóttir, H.: Permathawing permafrost , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8176, https://doi.org/10.5194/egusphere-egu22-8176, 2022.

09:52–09:59
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EGU22-1241
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ECS
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Virtual presentation
Lijuan Yang, Chunmei Wang, Chunmei Zhang, Guowei Pang, Yongqing Long, Lei Wang, Baoyuan Liu, and Qinke Yang

 Soil erosion seriously damages land resources, which is a global environmental problem. Gully erosion is an important manifestation of soil erosion, in recent years, frequent extreme rainstorms have aggravated the occurrence and development of gully erosion. In order to study the formation and development patterns of newly formed gullies under the condition of climate change, this paper takes the Wangwugou Small Watershed of the Chabagou Watershed on the Loess Plateau in Northern Shaanxi as the research area, and takes the “7·26” extreme rainstorm in Northern Shaanxi Province in 2017 as the main research object based on UAV images, to analyze the occurrence regularity of newly formed gullies, and discuss its development characteristics, its difference with the development of existing gullies before 2017, and its relationship with topographic parameters in the following three years. The results showed that: (1) during the “7·26” extreme rainstorm in Northern Shaanxi, there were 45 newly formed gullies in the Wangwugou Small Watershed, which are about 101 gully/km2, and they could be divided into four categories: slope surface gullies, terraced field gullies, unpaved roadway gullies and bottom gullies. The slope surface gullies were the largest, and the bottom gullies and terraced field gullies were wider and larger in area. Production roads, check dam farmland and sloping farmland are most prone to the occurring of gullies under rainstorm conditions. (2) In the three years after the formation of the new gullies, the development of the new gully heads was faster than that of the original existing gullies, and 34.48% of the heads of newly formed gully was further advanced, which was 1.32 times of the original existing gullies. The average gully head retreat distance of newly formed gullies is 3 times that of the original existing gullies, which is up to 0.58 m/a, and the maximum speed could reach 2.12 m/a. (3) The increase of the drainage area could significantly promote the development of gully heads, which is an important topographic index to simulate the retreat rate of gully heads. Under extreme rainfall conditions, the soil erosion situation is highly serious in the study area, and the source of newly formed gullies could be traced more rapidly within three years after their occurrence. Therefore, special attention and enhanced management should be attached to the prevention and control of such gullies.

How to cite: Yang, L., Wang, C., Zhang, C., Pang, G., Long, Y., Wang, L., Liu, B., and Yang, Q.: Study on the Occurrence and Development of Gullies under extreme Rainstorm Conditions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1241, https://doi.org/10.5194/egusphere-egu22-1241, 2022.

Coffee break
Chairpersons: Gianvito Scaringi, Luigi Lombardo, Stefano Luigi Gariano
10:20–10:27
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EGU22-729
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ECS
Yi-Ting Li, Guei-Lin Fu, and Cheng Hsiu Tsai

Taiwan has unique geographical characteristics. Located in a subtropical monsoon region, it is plagued annually by exceptional meiyu (East Asian rainy season) in May and June, and numerous typhoons from July to October. This unique climate often brings torrential rains and combined with Taiwan’s steep topography and short rivers, frequently triggers severe floods. Moreover, Taiwan lies at the intersection between the Eurasian Plate and the Philippine Sea Plate and is among the areas with the world’s most frequent felt earthquakes. Natural hazards here can roughly be categorized into four types: earthquake, typhoon, flood, and hillside disasters; manmade disasters include: industrial disasters, residential/commercial fire, road traffic accident, and shipwreck. When disasters strike, they often cause grave impacts and tolls in human lives and properties. In recent years, there has been a rising trend in both their frequency and scale due to rapid urbanization and growing environmental vulnerability.
According to World Bank’s 2005 publication, Natural Disaster Hotspots - A Global Risk Analysis, Taiwan tops the world in the land area simultaneously exposed to three or more natural hazards (73%) and in the population under disasters’ threat (73%). Additionally, there has been an increase in potential hazards such as disease outbreaks and severe public safety accidents. Therefore, when large-scale disasters strike and the impact is beyond what the affected municipalities can or have resources to handle, the key to minimizing death and injuries as well as financial losses becomes how nearby municipalities can offer support, participate rapidly in the emergency response, integrate resources effectively, enhance response effectiveness and prevent the disaster’s spread.
The “Operational Compact for Emergency Management Mutual Aid between Municipality and County Governments” passed in 2005 has now been in effect for four years. Yet, a comprehensive review of recent years’ severe disaster experiences indicates that the chief rescue and relief responsibilities still fall on the central government; the rare implementation of the above Compact by local authorities exposes the inadequacy of the actual system. Thus, this paper examines the literature on relevant ordinances, operating models, and case studies in the American and Japanese regional mutual aid systems to emergency management, in order to offer suggestions for improvement towards a more complete regional mutual aid system, a significant upgrade on municipalities’ disaster response capabilities and effective functional integration and collaboration.

How to cite: Li, Y.-T., Fu, G.-L., and Tsai, C. H.: Study on Establishing the System of Enterprises’ Participation in Flood Disaster Prevention, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-729, https://doi.org/10.5194/egusphere-egu22-729, 2022.

10:27–10:34
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EGU22-1284
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On-site presentation
Ugur Ozturk

Multivariate logistic regression models are the most popular in estimating landslide susceptibility by assessing various landslide causes—covariates—in mapped landslides or hindcasting landslides by including landslide triggering information such as rainfall. Although the sensitivity of these models to the variety of input data is frequently tested, the influence of data quality on the model accuracy is rarely discussed. For example, accurately representing spatial rainfall variability that triggered landslides may be essential in hindcasting models. Additionally, the properties of the mapped landslides, such as sample size, location, or time, are crucial to set a robust susceptibility model. Using an inventory that predominantly covers larger landslides would hinder a model by broadly covering the diversity of the factors leading to slope instability. Whereas smaller landslides could fail to capture sufficiently the range of values in the covariate space, likely decreasing the model performance. Another aspect is whether the number of mapped landslides is enough to estimate the susceptibility accurately or does more data means a better model. We developed several simple logistic regression models to answer all the above-listed questions relevant to assessing the model sensitivity. The model first demonstrated that global grid rainfall products could not accurately represent spatial rainfall distribution, which has a major influence on a landslide hindcast model. We have further found out that using only part of the individual landslides surprisingly may suffice to make accurate susceptibility estimates. Using smaller landslides in a susceptibility model outperforms a model that relies on larger landslides. Lastly, the model performance marginally varied after progressively adding more landslide data in a pilot study.

How to cite: Ozturk, U.: Role of baseline landslide inventory and grid rainfall precision on the sensitivity of susceptibility or hindcast models, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1284, https://doi.org/10.5194/egusphere-egu22-1284, 2022.

10:34–10:41
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EGU22-12658
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ECS
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Virtual presentation
Nicola Dal Seno and Matteo Berti

Landslide risk is one of the most relevant hazard that affects the Emilia-Romagna Region. Almost 80,000 landslides were mapped in the mountainous part, and the percentage of land covered by landslides exceeds in some areas 25%. Although most of the regional landslides are relatively slow, the economic impact is critical: in 2019, 1 million euros was allocated for urgent safety interventions, and it is estimated that at least another 80 would be needed to complete the plan. These numbers place the Emilia-Romagna Region among the areas with the highest landslide risk in the world. The geological characteristics of the Region, combined with the growing exploitation of the territory and the climatic changes underway, are making this problem more and more dramatic. It is now clear that emergency responses are no longer sufficient and that they must be accompanied by prevention actions devoted to mitigate the risk. 

The main objective of this work is to develop Artificial Intelligence models for the prediction of landslides in the Emilia-Romagna Region. The idea is to exploit the data collected by the University of Bologna in the last 15 years, as part of the research activities carried out in collaboration with the Regional Agency for Civil Protection and the Geological Survey of the Emilia-Romagna Region.

Available data consist of time series of rainfall, soil moisture, snow cover and displacement of some active landslides that have occurred in the region in recent years. The displacement data comes from permanent GPS stations, wire strain gauges, and robotic total stations installed in several landslides for emergency purposes. These data show clear relationships between precipitation and rate of movement. However, such relationships are difficult to reproduce using physically-based approaches.

The proposed machine learning approach was applied to the Emilia-Romagna Region of Italy taking advantage of the historical landslide archive, which includes more than 2210 rainfall events  that triggered 2363 landslide, and of the genetic classification algorithm TPOT (Tree-based Pipeline Optimization Tool) with more than 1million combinations of hyperparameters. The results show that landsliding in the study area is strongly related to rainfall event parameters (Precipitation during the event, The day of the event and in which location happened) while antecedent rainfall seems to be less important (Precipitation 30 and 60 days before the rainfall event). The distribution of landslides in the rainfall precipitation - day of the year chart shows that after the dry summer season a rain event of at least 90-100 mm is necessary to trigger a landslide. However, this number decreases as the day of the year increases, and then arrives in spring where many landslides are shown have been triggered with modest rain events (15-30 mm). The algorithm also provided an F1 test result score of 0.825, which means that it can predict a true positive (rainfall event triggers landslide) with a 70% of precision and with 95.5% about true negative (rainfall event do not triggers landslide).

How to cite: Dal Seno, N. and Berti, M.: Development of AI Algorithms for landslides prediction (Emilia-Romagna Region, Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12658, https://doi.org/10.5194/egusphere-egu22-12658, 2022.

10:41–10:48
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EGU22-938
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On-site presentation
Ali Yalcin

In this study, zone of Gundogdu (Rize) located in the Eastern Black Sea Region were examined in terms of landslide susceptibility and its stability analyzes were conducted. The study area is the region with the highest rainfall in Turkey. Heavy rainfall plays a major role in triggering landslides in this region. In this study, the relationship between precipitation and landslide was investigated. In addition, the effect of precipitation on weathering also determined the geological characteristics of the area. First of all, 1/25.000 scale geological map of Gundogdu and its surrounding was provided, the units are listed as Melyat Formation (Middle Eocene) and alluvium (Quaternary) from older to younger. 1/500 scale cross sections were generated for nineteen different landslides happened at Gundogdu in 2010, 2015, 2018, and 2021 years. Then stability analyzes were done with these data. Angle of internal friction (φ), cohesion (c), saturated unit weight, natural unit weight, dry unit weight and submerged unit weight (ϒd, ϒn, ϒk, ϒ'), specific gravity (Gs), porosity (n), saturation degree (SR), void ratio (e) and grain size distribution were determined with laboratory tests of soil samples which were taken to determine the engineering properties of soils located in places which stability calculations would be held. Following the results of these experiments, stability analyzes were done with 4 different methods (The Zero angle of Shearing Resistance Method, Ordinary Method of Slice, Bishop Method of Slices, and Janbu Method) according to the possible sliding surfaces that were plotted from geological section of landslide. As a result of these data, this region poses a great danger specially after rainfall with the effect of weathering. For this purpose, needs to be done for the prevention of landslides have been introduced.

How to cite: Yalcin, A.: Gundogdu (Ri̇ze) landslides and its surrounding slope susceptibility, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-938, https://doi.org/10.5194/egusphere-egu22-938, 2022.

10:48–10:55
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EGU22-5098
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ECS
Rachael Lau, Carolina Segui, Al Handwerger, Nate Chaney, and Manolis Veveakis

Fast disasters happen slowly. Two of the most notorious “rapid-onset” disasters – earthquakes and landslides – have a common dependency on a single determining parameter known as the Gruntfest number. Deep-seated landslides, seemingly rapid-onset to the naked eye, have historically been monitored with in-situ monitors and borehole sampling to understand conditions within the shear band. These in-situ monitoring techniques, however, are high-cost and labor-intensive. As satellite data and resources expand, remote sensing has become a more cost-effective and realistic option for monitoring gradual ground deformation caused by the creep of a deep-seated landslide. Differential interferometric synthetic aperture radar (InSAR), specifically, can be used to measure displacements on the Earth’s surface with precision to a few centimeters or less. Here we use InSAR and pre-existing borehole data for the Canillo landslide in Andorra to characterize the evolution of temperature and thereby the Gruntfest number from August 2018-December 2021. Our results reinforce the characteristic models for deep-seated landslides in Segui et. al (2020), suggesting that there exists a critical Gruntfest value where the landslide is catastrophically unstable. Given the anticipated increase in extreme climate with climate change, we expect it to become more frequent for landslides to reach this critical Gruntfest value, therefore necessitating a more robust analysis of the evolution of the Gruntfest number and the overall destabilization process for future work.

How to cite: Lau, R., Segui, C., Handwerger, A., Chaney, N., and Veveakis, M.: Forecasting and mitigating natural hazards with remote and in-situ monitoring , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5098, https://doi.org/10.5194/egusphere-egu22-5098, 2022.

10:55–10:57
10:57–11:04
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EGU22-7282
Ondřej Racek and Jan Blahůt

Thermo-rock: influence of temperature on rock slope properties

Rock slope stability is closely linked with the mechanical properties of the rock slope mass. These properties are influenced by numerous factors including meteorological, thermal and hydrogeological. Even short-term temperature cycles caused by direct sunlight, together with water saturation cycles can change mechanical properties of rock slope surficial zone. To partially quantify these influences, we have carried out short-term experiments at a former quarry test site. Geotechnical instrumentation of partial blocks with crack meters, surface and microcracks deformation monitoring using strain gauges, geophysical ERT monitoring, subsurface temperature and humidity monitoring, and  IR camera surface temperature sensing were used during 24-hour monitoring campaigns. Additionally, surface hardness was repeatedly measured using Schmidthammer. Before and after monitoring campaigns, rock mass samples from different depths were collected, to perform basic geomechanical tests. Using these complex data, the influence of short-term temperature changes on the rock slope surficial layer properties were estimated.

How to cite: Racek, O. and Blahůt, J.: Thermo-rock: influence of temperature on rock slope properties, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7282, https://doi.org/10.5194/egusphere-egu22-7282, 2022.

11:04–11:11
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EGU22-8429
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ECS
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On-site presentation
Gianvito Scaringi and Marco Loche

The residual shear strength is the sole available strength in regular shear zones of landslides after large displacements. While it does not depend on the stress history, it has been shown to depend on the rate of shearing. Various mechanisms have been proposed to explain the shear-rate strengthening and weakening observed, in particular, in soils containing clay minerals. Frictional heating has been shown to be involved in shear weakening under very large shearing rates. However, changes in temperature (imposed as boundary conditions and propagating into the shear zone) also can affect the residual shear strength, even in drained condition, but evidence in the literature is scarce.

Here, we show results of temperature-controlled ring-shear tests on two pure clays (a commercial bentonite, very active, and a commercial kaolin, inactive), conducted under a wide range of shear displacement rates (0.02–45 mm/min) and normal stresses (50–150 kPa) typical of slow to rapid landslides. After attaining the residual shear strength under the chosen stress and displacement-rate conditions at room temperature (20 °C), we increased the temperature of the cell up to 55 °C and kept it constant over a sufficient shearing distance before gradually decreasing it back to the initial value.

We observed a clear effect of temperature on the residual shear strength of the active clay. We evaluated, in particular, a shear strengthening under slow shearing (up to +1.5 %/°C) which turned into a shear weakening under fast shearing (-0.5 %/°C) under any normal stress. We evaluated that the transition between the two behaviours occurred at a shear displacement rate of 0.1–1 mm/min, which is consistent with the range for the onset of shear rate-dependent behaviours. The effect produced by the increase in temperature was shown to be reversible, although in some cases we noticed a net decrease in strength that could be attributed to an improved alignment of the clay platelets resulting from the thermal cycle. Notably, little thermal effects were seen for the inactive clay, suggesting that such effects should originate from changes in physico-chemical forces of interaction at the microstructural level, which are indeed especially relevant in active clays.

Changes in residual shear strength with temperature could be related to changes in landslide activity (particularly for creeping landslides in clay soils) in terms of seasonal/progressive acceleration or deceleration driven by external hydro-meteorological forcing. Furthermore, these changes could also control the potential for runaway motion if a transition from a strengthening to a weakening behaviour occurs. 

How to cite: Scaringi, G. and Loche, M.: Effects of temperature and shearing rate on the residual shear strength of two pure clays, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8429, https://doi.org/10.5194/egusphere-egu22-8429, 2022.

11:11–11:18
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EGU22-10442
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ECS
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Virtual presentation
Luis M. García, Edwin A. Soncco, Núria M. Pinyol, and Antonio Lloret

The available strength on slip surfaces in landslide after a significant displacement and at motion is the residual strength. The residual strength depends on the soil properties including both solid skeleton (mineralogy, particle shape and size, index properties) and pore fluid (chemical and rheological properties). The available strength also depends, as extensively reported in the literature, on several factors that may not remain constant in time and affect the landslide stability and dynamics: applied stress, accumulated displacement and shear strain rate. With a less extensive literature related to, the effect of temperature on the residual strength have been also observed.

This work reports on the results of a large number of ring shear tests under controlled rate and temperature performed on different types of soils. The results are interpreted in terms of the influence of mineralogy, clay content and plasticity on temperature effects on residual strength.

How to cite: García, L. M., Soncco, E. A., Pinyol, N. M., and Lloret, A.: Temperature effect on the residual shear strength., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10442, https://doi.org/10.5194/egusphere-egu22-10442, 2022.

11:18–11:25
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EGU22-7549
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Virtual presentation
Núria Pinyol, Mauricio Alvarado, and Luis Lemus

Landslide motion can be affected by the thermal effects resulting from the dissipation in heat of the frictional work generated in shearing bands. This problem was initially addressed for simple landslide geometries which have to be defined a priori. In this context, these analyses assume the motion of a rigid block and the thermal-hydro-mechanical phenomena were solved at basal shearing bands and their vicinity.

Later on, in order to generalize the analysis and to face more complex geometries and features, governing equations were implemented in the material point framework. This numerical method (MPM) is able to model large strains and displacements thanks to the double discretization of the domain by means of a Eulerian computational mesh and Lagrangian material points. A new approach was proposed to deal with the pathological dependence of the frictional work generation and the computational mesh element size. The methodology consists in the definition of computational embedded joints whose thickness is defined as a material parameter. 

The presentation will show the formulation of the thermal pressurization phenomena in MPM. First, the methodology will be evaluated under triaxial conditions and simple landslide geometries using different mesh sizes.

Real cases are later analyzed and modelled in MPM. The first case refers to an incipient landslide induced by a drawdown. The potential risk of acceleration induced by thermal pressurization is analyzed. The non-accelerated behavior observed in the field is explained combining the frictional heating induced weakening with non-linear velocity dependent frictional hardening. The results show that increments of a few degrees of the frictional angle with slide velocity can counteract the heating induced acceleration. 

The second case discussed is a coseismic landslide whose acceleration and large run-out cannot be justified by means of simple strength law unless imposing an extremely and probably unrealistic strain softening.

How to cite: Pinyol, N., Alvarado, M., and Lemus, L.: Thermal pressurization effect on landslide motion. Analysis with material point method., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7549, https://doi.org/10.5194/egusphere-egu22-7549, 2022.

11:25–11:32
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EGU22-8407
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ECS
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On-site presentation
Marco Loche, Gianvito Scaringi, Ali P. Yunus, Filippo Catani, Hakan Tanyaş, William Frodella, Xuanmei Fan, and Luigi Lombardo

Geostatistical models of landslide susceptibility do not usually account for thermal data, although these data are widely available, and experiments demonstrate that temperature does influence the mechanical and hydraulic behaviours of soils and rocks via a variety of thermo-hydro-mechanically coupled processes.

We took the epicentral region of the 2008 Wenchuan earthquake in China as our study area, for which a rich multi-temporal inventory of landslides is available. We built a landslide susceptibility model using a generalised additive model with a slope-unit partitioning of the area (~500 km2, comprising 42 sub-catchments), and a minimal set of covariates, including the map of peak ground acceleration of the mainshock and Landsat 7 land surface temperature (LST) data retrieved from Google Earth Engine.

We demonstrated that the LST relates to the decay of post-earthquake landslide activity, and in particular that warmer slopes seems to be comparatively more affected by prolonged landsliding. We also verified that LST data provided different insight from that offered by the normalised difference vegetation index (NDVI), by running our model with NDVI maps instead of LST maps. The two input maps showed little collinearity, and the variable effects of the NDVI in the model output showed less complexity compared to those of the LST. This hints at the presence of thermo-mechanical effects in slopes in addition to the known hydrological effects, the latter being associated with changes in evapotranspiration and thus in principle capturable by the NDVI.

Even though studies in other regions, seismic and non-seismic, are necessary, we suggest that thermal data should be used in landslide susceptibility modelling more systematically because they could potentially improve the model results and suggest physically-based relationships influencing slope stability.

How to cite: Loche, M., Scaringi, G., Yunus, A. P., Catani, F., Tanyaş, H., Frodella, W., Fan, X., and Lombardo, L.: Effect of temperature on post-earthquake landsliding near the epicentre of the 2008 Wenchuan earthquake, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8407, https://doi.org/10.5194/egusphere-egu22-8407, 2022.

11:32–11:39
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EGU22-9678
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ECS
Ondřej Racek, Jan Blahůt, and Filip Hartvich

This presentation is dedicated to a short description of a combined rock slope thermal monitoring system. The newly designed system is affordable and modular, which predisposes it to installation at multiple sites. This system is being used to monitor four different rock slopes in Czechia for a period of up to 3 years. Slopes differ by lithology, structural setting aspect and modes of instability. The monitoring system consists of a climate station, rock mass surface zone thermal monitoring and unstable blocks crackmeter monitoring. Since 2018 we have instrumented 11 blocks, which differ in terms of shape, volume and mode of destabilization. Analyses of crackmeter, thermal and climatic time-series showed influences of weather and temperature cycles on the crackmeter aperture. Consequently, short-term (diurnal) and medium-term (annual) temperature cycles on the rock slope surficial zone were described. Data show high variability linked to the partial blocks geometry and rock slope properties.

How to cite: Racek, O., Blahůt, J., and Hartvich, F.: Multi-site rock slope thermal monitoring: Initial results, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9678, https://doi.org/10.5194/egusphere-egu22-9678, 2022.

11:39–11:46
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EGU22-13375
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ECS
Saeed Tourchi, Antonio Gens, Jean Vaunat, and Gianvito Scaringi

In recent years, interest in argillaceous rocks has increased because they are being considered as potential host geological media for underground repositories of high-level radioactive waste (HLW). The host rock around the repository cells, containing the exothermic waste canisters, will be submitted to various coupled mechanical, hydraulic, and thermal phenomena. For a proper understanding and appropriate modelling of the excavation damaged zone around repository cells at elevated temperatures, the combined effects of those phenomena should be considered in an advanced constitutive model. The thermo-hydro-mechanical (THM) model presented herein is dedicated to non-isothermal unsaturated porous media. The model is developed within the framework of elastoplasticity, which includes features that are relevant for the satisfactory prediction of THM behaviour in argillaceous rocks: anisotropy of strength and stiffness, behaviour nonlinearity and occurrence of plastic strains prior to peak strength, significant softening after peak, time-dependent creep deformations, permeability increase due to damage, and shrinking of the elastic domain and the degradation of stiffness and strength parameters with temperature.

The model was applied to the numerical simulation of a full-scale in situ heating test conducted on Callovo-Oxfordian (COx) claystone, in the Meuse / Haute-Marne Underground Research Laboratory, simulating a heat-emitting, high-level radioactive waste disposal concept. The interpretation of the test was assisted by the performance of a numerical analysis based on a coupled formulation incorporating the relevant THM phenomena. Initial and boundary conditions for analysis, as well as material parameters, were determined from a comprehensive field and laboratory experimental programme. Thermal, hydraulic, and mechanical observations in COx claystone were discussed. The numerical analysis was able to accurately reproduce the behaviour of the experiment.

The performance and analysis of the in situ test have significantly enhanced the understanding of a complex THM problem, and have proved the ability of the theoretical formulation to provide adequate modelling capacities.

How to cite: Tourchi, S., Gens, A., Vaunat, J., and Scaringi, G.: Thermo-hydro-mechanical modeling of clayey geological medium: Theoretical framework and numerical study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13375, https://doi.org/10.5194/egusphere-egu22-13375, 2022.