NH3.9 | Alpine mass movements, landslide dams, and associated hazards

NH3.9

EDI

Mountain regions are a complex system of different glacial and non-glacial environments rapidly adapting to a changing climate. In this context, short-term landscape evolution is affected by, e.g. glacier motion and a variety of mass movements driven by different processes, evolving at different rates and potentially ending in catastrophic failures. In some cases, deposits may block rivers and form landslide dams that might fail and cause flood waves travelling far from the initial source areas. Such cascading events can pose risks to lives, human activities and infrastructures. With the current state of knowledge, it is very challenging to forecast the exact timing, location and magnitude of such events, raising important scientific and societal questions in terms of when, where and how big the next catastrophic failure may be.

In this session, we bring together researchers from different communities interested in a better understanding of the physical processes controlling mass movements and their associated hazards. The main goals are to present: (i) new examples of large catastrophic slope failures, in particular those causing river-damming; (ii) hitherto unpublished inventories of landslide dams, including statistical analyses of datasets and detailed analyses of case studies, which could be included in a Springer book currently being compiled, iii) insights from field observations and/or laboratory experiments; (iv) statistical and/or artificial intelligence methods to identify and map mass movements; (v) new monitoring approaches (in-situ and remote sensing) applied at different spatial and temporal scales; and (vi) models (from conceptual frameworks to advanced numerical models) for the analysis and interpretation of the governing physical processes.
The session also aims at triggering discussions on strategies applicable for hazard assessment and mitigation and on effective countermeasures that can be implemented to increase preparedness and risk reduction.

Co-organized by GM4
Convener: Andrea Manconi | Co-conveners: Anja Dufresne, Federico Agliardi, Andrea Wolter, Xuanmei Fan, Mylene JacquemartECSECS, Chiara CrippaECSECS
Orals
| Fri, 28 Apr, 08:30–10:15 (CEST)
 
Room C
Posters on site
| Attendance Fri, 28 Apr, 16:15–18:00 (CEST)
 
Hall X4
Orals |
Fri, 08:30
Fri, 16:15

Orals: Fri, 28 Apr | Room C

The oral presentations are given in a hybrid format supported by a Zoom meeting featuring on-site and virtual presentations. The button to access the Zoom meeting appears just before the time block starts.
08:30–08:35
Alpine mass movements
08:35–08:45
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EGU23-13466
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NH3.9
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Virtual presentation
Charlotte Wolff, Tiggi Choanji, Li Fei, Amalia Gutierrez, Marc-Henri Derron, Michel Jaboyedoff, Andrea Pedrazzini, and Carlo Rivolta

The Ticino Canton, located in the Swiss Alps, is characterized by steep valleys with important slope instabilities. It particularly affected by rock avalanches and landslides especially after important precipitations.
One of those is the Cima del Simano gneissic mountain in the Blenio valley. The top, reaching an altitude of 2550m, is strongly weathered and presents one main 500 meters-long open fracture and several smaller fractures. Some preliminary satellite InSAR results highlight downward movements. This instability is worthy to be studied since it represents a risk for the road passing at the bottom or villages implanted on its slopes. 
Nevertheless, this mountain is challenging to study because of (1) its bad accessibility: the top without access roads is covered by snow half of the year and (2) the atmospheric effects: the top is often hidden by clouds.  
For those reasons, the study is carried by combining several remote sensing techniques to acquire a maximal amount of information on the instability movements such as rockfalls, topplings and slow deep-seated landslides. Those techniques are extensometers, GNSS, Lidar, satellite InSAR, Ground-Based InSAR (GB-InSAR) and drones Structure from Motion (SfM). They are aimed at confirming the failure scenarios, predicted based on field observations and by structural analyses.  
With Lidar and SfM point clouds one is able to detect small blocks in toppling or sliding, which are confirmed by the results of GNSS and GB-InSAR campaigns, as well as zones of accumulations of rock avalanches debris. By means of GB-InSAR and satellite InSAR one can detect more long-term moving areas (few mm/year). We estimate the limits of those instabilities and their corresponding volume with structural analyses of the discontinuities using Coltop3D and by applying the Slope Local Base Level (SLBL) method. 
For the main fracture, we try to delimit the contours of the instability, but such an aperture and hypothetical instability edges are hardly explained by the actual topography. One explanation is that this fracture was inherited from an older important gravitational event, whose involved material collapsed and was washed out since the event occurred.

How to cite: Wolff, C., Choanji, T., Fei, L., Gutierrez, A., Derron, M.-H., Jaboyedoff, M., Pedrazzini, A., and Rivolta, C.: Use of combined monitoring remote sensing techniques for the study of active fractures in a remote area: Case of Cima Del Simano rockslide, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13466, https://doi.org/10.5194/egusphere-egu23-13466, 2023.

08:45–08:55
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EGU23-15632
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NH3.9
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ECS
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On-site presentation
Nina Jones, Tazio Strozzi, and Frank Paul

Global atmospheric warming and associated deglaciation effects lead to the increasing development of slope instabilities in glacier forefield environments. The primary drivers are debuttressing effects due to retreating glaciers, exposure of previously contained rock masses and thawing of permafrost. Such effects can lead to a decrease in slope stability and possible resulting failure in the generally rough and steep terrain encountered in high mountains, such as the densely populated European Alps, calling for extensive hazard analyses of such features.

Within the framework of the ESA Regional Initiatives for the Alps, the AlpGlacier project analyses capabilities to monitor glaciers in the Alps from the Copernicus Sentinel satellites. The derived products are: (a) snow cover and (b) flow velocities, both on glaciers, as well as (c) pro-glacial lakes and (d) slope instabilities, both in glacier forefields. Synergies through a combination of sensors, with focus on Sentinel-1 and -2, are tested and sensor limits identified. The presented work focusses on the slope instability product. The specific challenges to detect slope instabilities are the highly variable rates of movement combined with the long-lasting presence of snow cover, requiring the application of diverse DInSAR processing approaches and a detailed visual analysis of the observed changes. We present a comparison of standard and advanced DInSAR methods using Sentinel-1 data to evaluate the possibilities and limitations to detect slope displacements in three selected study regions in the European Alps. The Mattertal region in Switzerland, Mont Blanc region in France/Italy and Ötztal Alps in Austria are characterised by steep relief, the occurrence of permafrost, dense infrastructure and known slope instabilities. All sites experience glacier retreat since the Little Ice Age that leads to the potential formation of glacier lakes and slope instabilities. Continuous Sentinel-1 acquisitions exist for each site, which are used in multiple DInSAR techniques to detect and map slope instabilities, allowing an assessment of the variability of detected surface motion and suitability of the applied methods.

Results show a widespread distribution of slope instabilities moving at <2 cm/year to >30cm/year. Movements include soil and rock slides, rock falls, rock slope deformations as well as permafrost-related movements and rockglaciers. Time series extracted for exemplary movements occurring along retreating glaciers in each study region show distinct accelerations in the last 5 years that may be related to deglaciation effects. The results are validated with optical and SAR offset tracking methods.

How to cite: Jones, N., Strozzi, T., and Paul, F.: Slope instability mapping in glacier forefield environments of the Alps using standard and advanced DInSAR techniques, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15632, https://doi.org/10.5194/egusphere-egu23-15632, 2023.

08:55–09:05
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EGU23-15433
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NH3.9
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ECS
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On-site presentation
Alessandro De Pedrini, Christian Ambrosi, Andrea Manconi, and Federico Agliardi

Spaceborne synthetic aperture radar interferometry (InSAR) is commonly applied in mountain environments to detect and monitor mass movements to support local or regional natural hazard evaluation. InSAR technology is being increasingly used thanks to the recent open data policies or relatively low costs. Despite the remarkable advantage of observing wide regions, the technology presents intrinsic limitations which are emphasized or reduced depending on the satellite and the characteristics of the area investigated. Satellites with different revisiting times and operating in various bands, namely in the X (wavelength lambda = 3.1 cm), C (lambda of 5.6 cm), and L (lambda of 23.1 cm) bands, are suitable for observing mass movements with different characteristics depending on mountain relief, vegetation, and displacement rates. However, the use of a certain satellite can result in misleading displacement rates or a lack of measurements.

In this work, we compare the data from different satellites to highlight the capabilities and the general limitations of the method for application in a 1’500 km2 wide area of the Southern Swiss Alps, covering the Canton Ticino and a portion of Canton Grisons. The main valleys have a north-south orientation, characterized by steep slopes of altitudes between 2’000 and 3’000 meters a.s.l., covered by typical alpine vegetation. The dataset processed includes the ERS, Envisat, Sentinel-1, and RadarSAT missions, both ascending and descending geometries for a time frame of several decades. The distribution of the instabilities of the whole region is provided by the update “Catalog of the instabilities of Canton Ticino, 2016” expanded to the adjacent Calanca and Mesolcina valleys of Canton Grisons. The mapping has been made by the Institute of Earth Sciences of the University of Applied Sciences and Arts of Southern Switzerland (SUPSI) in the framework of the Interreg AMALPI 18 project and the mapping of the geological maps Osogna, Grono, Biasca, and Mesolcina of the Swiss Geological Atlas AG25. We validate the InSAR results by comparing the surface velocities with terrestrial monitoring, field observations, and historical information that describe the rock slope failure activity.

From the statistical information obtained by the comparison of slope displacements detected through the Permanent Scatterers technique PS, the areas affected by instability, and different movement rates, we make considerations on the use of the PS for monitoring rock slope failures of different types and rates of displacement in a mountain context.

How to cite: De Pedrini, A., Ambrosi, C., Manconi, A., and Agliardi, F.: Evaluation of rock slope failure activity by comparison of multi-sensor InSAR datasets in the Sothern Swiss Alps, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15433, https://doi.org/10.5194/egusphere-egu23-15433, 2023.

09:05–09:15
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EGU23-12711
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NH3.9
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ECS
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On-site presentation
Emilie Lemaire, Anja Dufresne, Pooya Hamdi, Bretwood Higman, and Florian Amann

The interaction between glacier retreat and rock slopes has gained considerable attention in the past years due to climate change. Glaciers shape mountain slopes and can daylight zones of weakness as they recede. Glaciers can act as a preparatory factor or trigger for slope failure. A retreating glacier at the slope's toe is often cited as the cause of failure. However, the relationship between glacier retreat and rock-slope stability is much more complicated, particularly for landslides that lack an explicit trigger. We studied a paraglacial slope failure at Grewingk Lake and Glacier in southcentral Alaska, United States. The collapse occurred on October 14, 1967, with no specific trigger, such as heavy rain or seismic activity on the day of the event. Grewingk Glacier is a lake-terminating glacier that has experienced and continues to experience rapid retreat, as have most glaciers around the world. The rapid retreat and the location of the glacier at the time of the collapse could lead to the conclusion that this was the cause of the collapse. However, a thorough examination of the structural geology of the slope and processes that could contribute to reduce the slope stability showed that the retreat of the glacier is only part of the tale. The structural preconditioning, together with an accumulation of seismic activity and daylighting fracture planes progressively contributed to the slope's destabilization. Our study emphasizes the value of examining the temporal trends of paraglacial rock-slope failures in situations in which there was no evident trigger at the time of the collapse.

How to cite: Lemaire, E., Dufresne, A., Hamdi, P., Higman, B., and Amann, F.: Evaluation of factors that led to the 1967 paraglacial slope failure at Grewingk Lake and Glacier, Alaska, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12711, https://doi.org/10.5194/egusphere-egu23-12711, 2023.

09:15–09:25
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EGU23-11642
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NH3.9
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ECS
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On-site presentation
Małgorzata Chmiel, Fabian Walter, Lena Husmann, Johannes Gassner, and Christian Kienholz

The Kandersteg region, Switzerland, has a history of catastrophic rock slope failures that repeatedly occurred throughout the Holocene, with volumes reaching hundreds of millions of cubic meters. In recent years, the rock slope near "Spitze Stei" has exhibited elevated displacement rates exceeding 10 cm per day, suggesting a growing instability of up to 20 million m3.

Due to the destructive potential of the Spitze Stei rockslide, extensive monitoring has been put in place since 2018, including borehole temperature logging, water pressure measurements and surface displacement monitoring. Borehole temperature measurements and direct observations highlight the presence of degrading permafrost, possibly on planes of enhanced gliding and shear deformation. However, point-like borehole measurements and sensing technology focusing on the slope surface cannot fully describe processes influencing slope dynamics, such as freeze-thaw cycles, varying water pressure, and progressive damage within the slope. These processes have lateral and depth-dependent sensitivity, causing changes in the rock's elastic properties, thus impacting seismic velocities. Here, we aim to provide a better understanding of these primary processes driving the dynamics of Spitze Stei. To this end, we analyze variations in relative seismic velocities (dv/v) measured through continuous seismic data and seismic interferometry. With this technique we transform seismic noise into coherent signals through cross-correlations of data from five 3-component seismometers.

The initial results of the time series of relative seismic velocity variations (dv/v) constrain the lateral and depth-dependent extent of subsurface changes. The results indicate that a substantial decrease in relative seismic velocity occurs at the times of rather heavy rain (rainfall >10 mm d-1). This suggests that dv/v reflects material changes caused by pore pressure increase and reduction in material strength. The shallowest dv/v measurements agree with surface displacements displaying cyclic slipping of material.

We discuss how our observations help identify the primary processes controlling the dynamics of the Spitze Stei rockslide, give quantitative insight into rock damage, and allow separating effects from irreversible damage growth and reversible thermoelastic and hydrologic variations. This knowledge is needed to better understand the development of large rock failures and potentially improve warning systems.

How to cite: Chmiel, M., Walter, F., Husmann, L., Gassner, J., and Kienholz, C.: Towards a better understanding of large-scale rock slope dynamics with seismic interferometry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11642, https://doi.org/10.5194/egusphere-egu23-11642, 2023.

09:25–09:35
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EGU23-7888
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NH3.9
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ECS
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On-site presentation
Josefine Umlauft, Christopher Whilliam Johnson, Philippe Roux, Daniel Taylor Trugman, Albanne Lecointre, Andrea Walpersdorf, Ugo Nanni, Florent Gimbert, Bertrand Rouet-Leduc, Claudia Hulbert, and Paul Allan Johnson

During the RESOLVE project ("High-resolution imaging in subsurface geophysics: development of a multi-instrument platform for interdisciplinary research"), continuous surface displacement and seismic array observations were obtained on Glacier d'Argentière in the French Alps for 35 days during May in 2018. This unique data set offers the chance to perform a detailed, local study of targeted processes within the highly dynamic cryospheric environment. In particular, the physical processes controlling glacial basal motion are poorly understood and remain challenging to observe directly. Especially in the Alpine region for temperate based glaciers where the ice rapidly responds to changing climatic conditions and thus, processes are strongly intermittent in time and heterogeneous in space. Spatially dense seismic and GPS measurements are analyzed with machine learning techniques to gain insight into the underlying processes controlling glacial motions of Glacier d'Argentière.

Using multiple bandpass-filtered copies of the continuous seismic waveforms, we compute energy-based features, develop a matched field beamforming catalogue and include meteorological observations.Features describing the data are analyzed with a gradient boosting decision tree model to directly estimate the GPS displacements from the seismic records.

We posit that features of the seismic noise provide direct access to the dominant parameters that drive displacement on the highly variable and unsteady surface of the glacier. The machine learning model infers daily fluctuations as well as longer term trends and the results show on-ice displacement rates are strongly modulated by activity at the base of the glacier. The techniques presented provide a new approach to study glacial basal sliding and discover its full complexity.

How to cite: Umlauft, J., Johnson, C. W., Roux, P., Trugman, D. T., Lecointre, A., Walpersdorf, A., Nanni, U., Gimbert, F., Rouet-Leduc, B., Hulbert, C., and Johnson, P. A.: Mapping glacier basal sliding applying machine learning, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7888, https://doi.org/10.5194/egusphere-egu23-7888, 2023.

Landslide dams
09:35–09:45
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EGU23-7131
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NH3.9
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ECS
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On-site presentation
Roshanak Shafieiganjeh, Marc Ostermann, Barbara Schneider-Muntau, and Bernhard Gems

Landslide dams are counted as one of the most destructive mountain hazards. They pose flood hazards downstream and damming effects upstream. Assessing their stability requires either a detailed case study or relying on geomorphic indices. A case-study project, while being accurate, is time-consuming and cannot be implemented during emergencies. Therefore, geomorphic indices which are calibrated based on the landslide dam inventories facilitate the stability assessment of these dams.

Landslide dam inventories generally include qualitative and quantitative parameters of geographical location, landslide, dam, lake, and upstream catchment. In the current research, a comparison is made on the applicability of the existing geomorphic indices on a developed data inventory of Western Austria, Bavaria, and Northern Italy. The comparison indicates that the geometrical parameters can solely or in combination with each other stand as resisting and driving forces and that the stability assessment based on these parameters is reliable. According to the results, the volume and height of the dam are the most representative parameters of the dam's stability. However, the catchment characteristics such as area, slope, and ruggedness act as the determining destructive force. To evaluate the reliability of the methods used in the calculation or estimation of the geometric parameters, a statistical assessment is conducted based on the data from other published inventories. A wide range of variations in the mean value of the landslide and dam volume indicates the results' dependency on the study areas' geomorphological characteristics. On the other hand, the dam height of the current dataset, the datasets of Japan, New Zealand, and a worldwide database varies in only a 15 m range indicating a close estimation in different geographical regions. This emphasizes the necessity of the existence of a determining procedure for the estimation of such representative parameters in the landslide dam inventories.

How to cite: Shafieiganjeh, R., Ostermann, M., Schneider-Muntau, B., and Gems, B.: Significant parameters of a landslide dam inventory from the stability assessment aspect - data analysis based on the 'part of the Eastern Alps' data inventory, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7131, https://doi.org/10.5194/egusphere-egu23-7131, 2023.

09:45–09:55
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EGU23-9848
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NH3.9
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ECS
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On-site presentation
Anne-Laure Argentin, Thomas Hauthaler, Moritz Liebl, Jörg Robl, Stefan Hergarten, Günther Prasicek, Bernhard Salcher, Daniel Hölbling, Claire Pfalzner-Gibbon, Lisa Mandl, Michael Maroschek, Lorena Abad, and Zahra Dabiri

Perennial landslide dams interrupt the sediment connectivity of rivers. Although most landslide dams do not persist for more than a few days, those that do can exhibit significant sediment trapping capacity. While water can pass through or over the dam, the sediment load is trapped upstream of the dam until the dam breaks or gradually erodes, or is completely filled with deposits. The volume of sediment stored in this way can reach up to three times the volume of impounded water, as we find by back-analyzing the lake Hintersee in southeastern Germany. In this work, we reconstruct the pre-landslide topography using Petrel and then use the Gerris shallow-water flow solver with a Voellmy rheology to back-analyze this landslide-dammed lake in the Bavarian Alps. We test several landslide release scenarios and different landslide rheologies to obtain the best-fitting reconstruction of the dam topography. We then fill the landslide dam with water and sediment using simple slope algorithms and validate the results against the current topography. Finally, we compare the landslide deposit thicknesses, water depths, and trapped sediment thicknesses of our different scenarios in order to provide new insight into the damming and sediment trapping capacity of landslides.

How to cite: Argentin, A.-L., Hauthaler, T., Liebl, M., Robl, J., Hergarten, S., Prasicek, G., Salcher, B., Hölbling, D., Pfalzner-Gibbon, C., Mandl, L., Maroschek, M., Abad, L., and Dabiri, Z.: Quantification of the damming and sediment trapping capacity of landslides and their dammed lakes: the example of the Hintersee landslide dam, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9848, https://doi.org/10.5194/egusphere-egu23-9848, 2023.

09:55–10:05
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EGU23-8382
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NH3.9
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On-site presentation
Sergio A. Sepulveda, Stella M. Moreiras, Pilar Jeanneret, Mariana Correas Gonzalez, Kimberly Bravo, Jacqueline Azanero, and Marisol Lara

Large volume landslides are common features in the high-topography Andes of central Chile and Argentina (31°-35°S). Many of these landslide deposits, mostly dating from Late Pleistocene to Holocene and related to a combination of deglaciation effects, seismicity and climate pattern changes, were large enough to block the glacial valleys and form landslide dams, some of which remain holding lakes until today. In this paper, we review and investigate some conspicuous landslide dams deposits from prehistoric times in the Andes Main Range in Chile and Argentina and the Andes Frontal Range in Argentina. A bibliographic review is followed by remote sensing analysis to obtain the main morphometric parameters of the landslides and the dams, complemented with field investigations in some of them. The landslide dams related with the rock slope failures of Portillo (1.1 km3, ~13 ka), Salto del Soldado (0.2 km3, 14- 9 Ka) Mesón Alto (4.3 km3, 4.7 Ka), Cortaderas-San Nicolás (2.4 km3, Holocene) and the Pangal complex (0.3 km3 , 40-11 ka) in the Chilean Western slope and the Laguna Blanca (81 hm3, ~12 ka), Horcones (0.35 km3, ~11-8 Ka), Negro (~18 Ka), Amarillo (~8Ka), and Laguna Atuel (56 hm3,~3 Ka) landslides in the Argentinean Eastern slope are described. Eldest rock avalanches associated with a seismic triggering mechanism that generate dammed lakes were previously studied in the Central Argentinean Andes such as Tigre Dormido (1.7 km3, ~46 Ka), Placetas Amarillas (1.6 km3, ~150 ka), and Piedras Blancas (0.89 km3, ~130 Ka). In these cases, the fine lake sequences reach 30 m in thickness but no outburst terraces were identified downstream, hardly supporting their catastrophic drainage.

In both Chile and Argentina, most preserved damming collapses correspond in general to huge rock avalanches, even though some slides and debris flows also blocked narrow valleys. In general, studied ancient dams are isolated in mountain remote areas but they show evidences of catastrophic ruptures that emphases their importance in the cascade hazard scenarios. While the large majority of identified dams in the region are thousands of years old, some historic cases show that these processes still occur and pose a geological hazard. Given the large area that can be affected by outburst floods downstream the usually remote landslide sites, potentially impacting villages as well as mining, energy, and transportation infrastructure, these geohazards must be considered in risk reduction strategies in the Andean region.

How to cite: Sepulveda, S. A., Moreiras, S. M., Jeanneret, P., Correas Gonzalez, M., Bravo, K., Azanero, J., and Lara, M.: Investigation of prehistoric landslide dams in the central Andes of Chile and Argentina, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8382, https://doi.org/10.5194/egusphere-egu23-8382, 2023.

10:05–10:15
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EGU23-11125
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NH3.9
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Virtual presentation
Akshat Vashistha, Srikrishnan Siva Subramanian, and Josodhir Das

In mountainous terrains, coseismic landslide dams are catastrophic geological hazards that induce devastating and cascading effects on humanity. Identification of historical landslide dams is necessary to mitigate the long-term effects it may cause in the future. If not controlled or necessary mitigation measures are not appropriately applied, the landslide dam deposits may have longer implications in generating cascading hazards through geological time. Coseismic landslide dams in the Indian Himalayas are not explored more except for very few studies. Here, we propose a framework to examine the potential for coseismic landslide damming and analyze the possible mitigation strategies to minimize the effects. We use the framework to analyze the potential of coseismic landslide damming in Uttarakhand, India, in the western part of the Himalayas. In addition, to make a coseismic landslide dam susceptibility map, we identified around a dozen landslide dams along major river systems in Uttarakhand which were not mapped or identified earlier. We found that many landslides during the Chamoli 1999 earthquake triggered many dams. While major earthquakes after 1999 did not occur in Uttarakhand, the possibility of coseismic landslide disasters should not be overlooked, and preparedness and mitigation strategies become inevitable to avoid cascading damages by landslide damming. 

How to cite: Vashistha, A., Subramanian, S. S., and Das, J.: Co-seismic landslide damming in the Indian Himalayas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11125, https://doi.org/10.5194/egusphere-egu23-11125, 2023.

Posters on site: Fri, 28 Apr, 16:15–18:00 | Hall X4

The posters scheduled for on-site presentation are only visible in the poster hall in Vienna. If authors uploaded their presentation files, these files are linked from the abstracts below, but only on the day of the poster session.
X4.27
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EGU23-5083
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NH3.9
Alin Mihu-Pintilie and Anja Dufresne

The states and territories of Europe extend from the Ural mountains in the East to the Black and Mediterranean Seas in the South and are enclosed by the Atlantic Ocean West and North. With a variety of landscapes prone to slope failures, only few inventories exist of the resulting landslide deposits and river-damming (past and present) locations. In this chapter of the planned Springer Book „Landslide Dams around the World“ we are compiling data from published inventories, search for and add unpublished data, and aspire to present as complete a story as possible of landslide dams in Europe. Whilst extensive inventories exists for Austria, Italy, Norway, and Switzerland, few other countries feature published landslide dam datasets (e.g., Romania). Case studies exist for larger dams and some datasets are stored (but not always available) with regional geological surveys. We hence call for collaboration across Europe to complete the database and pursue the following objectives: (i) create a comprehensive landslide-dam database for the European territory, (ii) statistically analyse the data for clusters, geomorphic and temporal correlations, (iii) identify influencing factors (e.g., regional, climatic, hydrologic, anthropogenic) on landslide-dam occurrence and stability, and (iv) make the data available for researchers and stakeholders alike.

How to cite: Mihu-Pintilie, A. and Dufresne, A.: Landslide dams in Europe – distribution, data gaps, and further research, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5083, https://doi.org/10.5194/egusphere-egu23-5083, 2023.

X4.28
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EGU23-1145
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NH3.9
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ECS
Andrea Wolter, Regine Morgenstern, Biljana Lukovic, Simon C. Cox, Dan Bain, Akansha Sirohi, Zane Bruce, Dougal Townsend, Brenda Rosser, Katie Jones, and Chris Massey

As key components of multi-hazard, cascading slope-to-river systems around the world, landslide dams can have severe consequences. They form when landslides block a watercourse and can result in catastrophic flooding if they fail rapidly. Nonetheless, they are under-researched given the potentially high consequences of sudden dam breach and failure. Their formation, longevity, and breaching behaviour are not well understood, which is important information needed for effective risk management.

We present an Aotearoa New Zealand database of landslide dams, spanning pre-historic to historic natural dams compiled from several existing datasets and inventories. The database includes ~1030 landslide dams, as well as information for each dam such as catchment properties, landslide and dam dimensions, dam type, and dam stability where available. Where possible, quantitative attributes have been calculated automatically using arcpy (a Python site package that utilises ArcGIS processing tools), which allows consistency and repeatability in the database. A data quality ranking scheme has also been developed to assess the reliability of each dataset. The database will be available online on the OSF platform in mid-2023.

Several case studies, including the Hapuku, Stanton, Leader, Linton, and Conway landslide dams that formed during the 2016 Mw 7.8 Kaikōura earthquake, have been analysed in detail. Multiple field and remote sensing campaigns completed since 2016 – including field mapping, RTK surveying, drone photogrammetry, and LiDAR surveys – show the evolution of the landslide deposits and dams, providing high-resolution spatiotemporal data on their formation and breaching characteristics.

The database is currently being analysed to improve our understanding of dam formation potential and longevity, as well as breaching behaviour. These analyses will contribute to improved hazard management and avoidance.

How to cite: Wolter, A., Morgenstern, R., Lukovic, B., Cox, S. C., Bain, D., Sirohi, A., Bruce, Z., Townsend, D., Rosser, B., Jones, K., and Massey, C.: A National Landslide Dam Database for New Zealand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1145, https://doi.org/10.5194/egusphere-egu23-1145, 2023.

X4.29
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EGU23-3171
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NH3.9
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ECS
Kai-Yi Chiu and Su-Chin Chen

Due to the young geology, unique climates, and location in the Pacific Rim seismic zone, complex sediment disasters frequently occur in Taiwan.  After the Chi-Chi earthquake in 1999, more than ten landslide dams appeared in the mountain regions with disaster potential to the neighbor.  The process of landslide dam breach is complex, often accompanied by abundant sediment and floods that cause damage to the downstream environment.  Therefore, analyzing the landslide dam breach process is an important subject.

The study area is located in Landau Creek in Huisun Forest, Nantou County.  Landao Creek is a tributary of the Beigang River, a potential debris flow torrent.  The soil and rocks on site were used to build a natural dam for the dam failure experiment.  The process of dam failure was recorded with cameras and UAVs.  In order to understand the relationships between the dam and the water level, some water pressure gages were set inside the dam and in upstream to measure the water pressure over time.  Because it is difficult to observe the change of the underwater breach with the naked eye during the dam failure process, triaxial sensors were placed in the dam body to determine the change of dam breach by recording the time when the sensors were scoured away from their original position.  The analysis showed that the groundwater level gradually increased during the dam failure, and the downward trend would slow down over time.  The underwater breach shape was similar to a parabolic or trapezoid shape.

How to cite: Chiu, K.-Y. and Chen, S.-C.: Influence of dam failure flow on water level in dam and the underwater breach topography, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3171, https://doi.org/10.5194/egusphere-egu23-3171, 2023.

X4.30
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EGU23-12136
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NH3.9
Tzu-Yao Chang, Wei-An Chao, and Chi-Yao Hung

In the case of dam breaches in natural rivers, there is a lack of systematic studies understanding how the changes in the river bed elevation. This study aims to understand the characteristics of erosion and deposition along the river channel. Two field-scale dam breach experiments were conducted in Landao Stream, which is a tributary of Beigang River, length about 1,952 km and average altitude 1,200 meters. The total length of the experiment area is 280 m, and the average slope is 6.3°. Experiment I is a case of single dam and Experiment II is single dam with spur dike. In Experiment I, a seismic array of 20 stations was installed along the left and right banks of the river. In Experiment II, a seismic array of 12 stations was first deployed along the center of the river channel with station spacing distances of 10 m. Then, a seismic impact experiment was carried out to obtain the associated seismic parameters for seismic physical models. After the impact experiment, the seismometers were reinstalled on the left and right banks of river. For each experiment, the surveys of sediment grain size distribution and digital elevation model were conducted before and after experiment, which can provide information on erosion and deposit of river bed. Additionally, the water level, surface flow velocity, time-lapse photos, and temporal changes in beach shape were also monitored during experiment. With the available data of fluvial measurements, topographic changes in riverbeds, grain size survey, and seismic parameters, our study suggested that the riverine seismic signals can record the ground motions caused by water flow, sediment transport, and debris flow. Results of a series of time-frequency analysis presented the additional information about the erosion and sedimentation of river bed. Finally, our proposed mechanisms based on seismic physical models (e.g., turbulent flow, bedload saltation, and debris flow) will be discussed with the previous results of numerical simulation. Our results demonstrated that the riverine seismic signals of seismic array can effectively and immediately quantify downstream sedimentary erosion and deposition characteristics after the dam breaching.

How to cite: Chang, T.-Y., Chao, W.-A., and Hung, C.-Y.: Using a seismic array to study sediment redistribution after dam breaching, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12136, https://doi.org/10.5194/egusphere-egu23-12136, 2023.

X4.31
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EGU23-5214
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NH3.9
Anja Dufresne, Xuanmei Fan, and Wolter Andrea

Landslide dams are an important component of slope-fluvial systems, particularly given their potentially disastrous consequences if they breach suddenly. To further research on dam longevity, stability, and failure mechanisms effectively, comprehensive landslide dam dataset are essential. Yet, such datasets from around the world are heterogeneous in their completeness and data-collection approaches, and we still see many geographical “blind spots” where research on landslide dams appears absent, at least within the published literature.

As part of a project to collate and compile a global, accessible landslide-dam database, we present some of the challenges involved in its construction. In addition to data heterogeneity and data gaps, biases and parameter definitions will be discussed and highlighted by several landslide-dam case studies from around the world. The aim of the discussion is to acknowledge these data biases, such as geopolitics, funding, accessibility, and triggering-event factors, and offer solutions for the global research community. We will also clearly define terms that have been vague in landslide-dam research so far. For example, dam height, volume, length and width are not used consistently – even what exactly constitutes a landslide dam can sometimes be a defined differently.  

How to cite: Dufresne, A., Fan, X., and Andrea, W.: Landslide dams around the World – case studies to global datasets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5214, https://doi.org/10.5194/egusphere-egu23-5214, 2023.

X4.32
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EGU23-12132
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NH3.9
Shu-Yun Yang and Wei-An Chao

In eastern Taiwan, a landslide dam formed on February 4, 2021 in the Danan River. The lithology of the collapsed material is composed of schist and meta-sandstone with a thickness of a few centimeters to tens of meters. The landslide dam partially breached on August 7, 2021, and completely broke in October 2021. In the event of a dam failure, the downstream influence area includes residents along the river of Tongxin Village, the power plant, and an important artificial channel to transport farmland around Tongxin Village for irrigation. Therefore, real-time monitoring of dam failure is needed to provide early warnings of impending floods. The traditional monitoring method is to install a water level gauge behind the landslide dam for emergency response. However, it is impossible to establish a water gauge monitoring system on site because landslides usually occur in rugged mountainous areas. In this study, seismic analysis is adopted to capture seismic signals possibly caused by landslide dam failure, and to track the location of flooding after landslide dam failure. In this study, after the formation of the landslide dam, a real-time broadband velocity-type seismometer station (station code DALB) was deployed on the top of a mountain, and two Geophones stations (station code DALU, DALD) were installed in the midstream and downstream, respectively. Combined the difference between the arrival time of seismic waves and the distance along the river channel, the flow velocity can be measured. Optical satellite images were used to constraint the time range of dam failure based on the change in the highest elevation of the dammed lake surface. Finally, by using the riverine seismic signals, the time point of dam breaching can be determined, and the flow velocity of water and sand in the river channel can be estimated. Our studies can provide an early warning of few minutes to the downstream. The results of the time-frequency analysis also showed that the front reach of the breach is dominated by debris flow.

How to cite: Yang, S.-Y. and Chao, W.-A.: Seismic signature of landslide dam breaching and it’s possible early warnings., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12132, https://doi.org/10.5194/egusphere-egu23-12132, 2023.

X4.33
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EGU23-14251
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NH3.9
Erik Kuschel, Christian Zangerl, Ursula Laa, Vinzent Klaus, Alexander Prokop, Eric Bernard, Jean-Michel Friedt, Léo Duvernet, and Florian Tolle

Landslide processes are one of the dominant agents of erosion and sediment transport in alpine terrain, which often pose a significant risk to communities and infrastructure around the world. Climate change generates a wide range of processes such as glacier retreat, permafrost degradation or changing precipitation patterns, which are projected to decrease the stability of mountain slopes and thus will lead to increased landslide activity. However, the empirical evidence is lacking as meteorological boundary conditions altered by climate change, may have different and often contrasting effects on landslide formation and activity. As a result of the Arctic amplification, high-arctic environments are an important field laboratory for investigating current and future landslide processes.

The ongoing paraglacial response of sediment-mantled slopes through landslide processes has been assessed and mapped around the globe. However, investigations on the impact of meteorological factors on shallow landslide formation modifying sediment-mantled slopes in the surroundings of retreating glaciers is in many cases not possible due to the lack of long-term high-resolution terrain data. The Austre Lovénbreen glacier basin in Svalbard (Norway) is a particularly relevant location to study the modification of slopes through landslides, as the area has been affected by the recent global warming characterized by the greatest temperature increase during the last three decades.

The objectives of this study are i) to provide data utilizing multi-temporal high-resolution terrestrial laser scans of the glacier and the surrounding slopes, ii) identify and quantify landslide processes found on sediment-mantled slopes, iii) investigate failure mechanisms and derive a conceptual model describing the adaptation of the periglacial talus slopes to the retreat of the glacier and iv) investigate the driving factors for the temporal and spatial evolution of landslides in the Austre Lovénbreen Basin.

The Austre Lovénbreen glacier basin represents a highly dynamic environment, which is in an unstable state, caused by the rapid retreat of the glacier and by climatic conditions. We show that, in contrast to the established literature, shallow debris slides are the primary source of sediment transport on steep sediment-mantled slopes in a high-arctic environment and that meteorological parameters control their spatial and temporal evolution.

How to cite: Kuschel, E., Zangerl, C., Laa, U., Klaus, V., Prokop, A., Bernard, E., Friedt, J.-M., Duvernet, L., and Tolle, F.: Investigating the effects of meteorological conditions on landslide formation in a high-arctic glacier basin using terrestrial laser scanning (Ny-Ålesund, Svalbard), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14251, https://doi.org/10.5194/egusphere-egu23-14251, 2023.

X4.34
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EGU23-16264
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NH3.9
Andrea Manconi, Yves Bühler, and Andreas Stoffel

Large compound landslides show long-term evolution, which is characterized by non-steady velocities, sudden accelerations and potential failure events. Accurate data is hence important for the analysis and the interpretation of their kinematic behavior, as well as associated hazard potential. Remote sensing techniques have demonstrated to be a valid complement to standard in-situ monitoring. Here we show how frequent acquisitions with remote Remotely Piloted Aircraft Systems (RPAS) can be used to study large landslide complexes. We performed an extensive analysis at the Brienz/Brinzauls landslide complex, located in canton Graubünden (Switzerland), based on 20 photogrammetric flights acquired between 2018 and 2023. Dem-of-Differences (DoD) and displacements from Digital Image Correlation (DIC) are computed to reconstruct the spatial and temporal evolution of the surface changes. We compare the results with independent monitoring data, and we perform a strain analysis to highlight areas of strain accumulation and identify possible relationships between kinematic domains, geological boundaries, as well as tectonic structures and rock mass discontinuities. The aim of this contribution is to demonstrate how spatial and temporal resolution of the datasets might deeply influence the interpretation of displacements in complex landslide scenarios.

How to cite: Manconi, A., Bühler, Y., and Stoffel, A.: Analysis of spatial and temporal evolution of the Brienz/Brinzauls deep-seated landslide, Switzerland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16264, https://doi.org/10.5194/egusphere-egu23-16264, 2023.

X4.35
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EGU23-3000
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NH3.9
Yu-Chung Hsieh, Ying-Hung Tung, Mien-Ming Chen, Hsi-Hung Lin, and Chung-Chi Chi

In the mountain area, Deep seated gravitational slope deformation (DSGSD) was a phenomenon that causes rock mass deformation under long-term gravity. In the Slate Belt of the Backbone Range, Taiwan where mainly slate distributed, it is more susceptible to develop DSGSD. After Typhoon Morakot (2009), the high-resolution airborne LiDAR topographic data of the entire island of Taiwan completed by 2016, which will be regularly updated every five years. This high-resolution airborne lidar topographic data could be applied to visual interpretation with the potential landslide area, multi-period data with activity of slope deformation. In this study, we used existing high-resolution LiDAR topographic data and the latest computerized 3D environments to conduct and explore preliminary geological information at the regional scale and potential large-scale landslide distribution with detailed topographical characteristics. The area of slow-moving landslides could be found by comparing multi- period LiDAR topographic data and UAV images. Through field investigations and UAV application in Lusan area of central Taiwan, the features caused by regional tectonic effects or DSGSD could be clarified and discussed activity and possible mechanism of rock mass failure caused by these DSGSD. The results help to understand the deformation mechanism of the slate area in the Central Range of Taiwan. In the future, we could further explore the possible causes of why DSGSD transform into catastrophic landslides.

How to cite: Hsieh, Y.-C., Tung, Y.-H., Chen, M.-M., Lin, H.-H., and Chi, C.-C.: Deep-Seated Gravitational Slope Deformation and Slow-Moving Landslides Revealed by Multi-Period LiDAR and UAS Data in the Slate Belt of the Backbone Range, Central Taiwan, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3000, https://doi.org/10.5194/egusphere-egu23-3000, 2023.

X4.36
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EGU23-9308
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NH3.9
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ECS
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Varvara Bazilova, Tjalling de Haas, and Walter Immezeel

Debris flows and floods and flash floods pose hazards to the densely populated areas of High Mountain Asia (HMA). The continuous decline in the cryosphere across the region such as glacier mass loss and permafrost thaw leads to exposure of the unconsolidated debris material and sediment deposits. This has led to changes in the magnitude and frequency of debris flows and floods. We aim to identify the controlling parameters and quantify the likelihood of debris flow and floods and the change in likelihood due to projected regional climate and cryosphere changes. Based on visual inspection of alluvial deposition and surface properties of the alluvial fans, we identified catchments across HMA where floods or debris flows occur. We built a database with morphometrical (e.g. catchment area, perimeter, slope, elevation range, Melton ratio) and climatic features (e.g. temperature and precipitation regime, freeze – thaw cycles, glacier and permafrost area) and build a CatBoost gradient boosting based machine learning classifier. We identify that debris flows are more likely to occur in small catchments, defined as catchments with small Melton ratio and high slope. Projected regional climate change will decrease the probability of the debris flows. It will also increase the probability of the flood being a dominant process in the catchment across the entire HMA.

 
 
 

How to cite: Bazilova, V., de Haas, T., and Immezeel, W.: Spatial distribution and changes in the debris flow hazard across High Mountain Asia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9308, https://doi.org/10.5194/egusphere-egu23-9308, 2023.