Large and Highly Dynamic Landslides (Bergstürze) in Bavaria

Despite significant progress in the development of advanced technologies for detecting and monitoring unstable slopes, accurately predicting catastrophic landslides remains a challenge. To tackle this challenge, our research integrates advanced prediction models and granular systems theory to provide insights into regime shifts within slow-moving deep-seated landslide dynamics. Our approach is designed to discern exceptional departures from historical landslide dynamics. The approach leverages the “group dynamics,” crucial for identifying precursory failure indicators, according to the generic dynamics of the precursory failure regime in granular systems. We select three different monitored slow-moving landslides as test cases. We employ an error correction cointegration vector autoregression model together with an exogenous regressor to encode historical spatiotemporal landslide dynamics and predict displacement at multiple locations by considering the historical landslide motion and relationship with external triggers. Displacement residuals are obtained by computing the difference between predicted and measured displacement for a given historical calibration time window. Threshold values for the displacement residuals are determined by analyzing the historical distribution of these residuals. Lastly, persistence in time of the threshold exceedance and the number of monitoring points that exceed the threshold at the same time are considered to encode the group dynamics. This approach offers several advantages, including the effective identification of critical regime shifts, adaptability, and transferability, and it introduces regime shift information into local landslide early warning systems. This approach can enhance confidence in the resultant alert, particularly when integrated with conventional alert systems, thereby improving the reliability of landslide warning systems.

Petrologic and structural controls on geomorphology of prehistoric Tsergo Ri slope failure, Langtang Himal, Nepal

Received 24 January 2011; revised 23 June 2011; accepted 30 June 2011; published 4 October 2011. [1] Landslides dynamics prediction remains difficult in spite of a considerable number of studies. The runout distance is widely used in analysis of landslide dynamics and in the calibration of the rheological parameters involved in numerical modeling. However, the unknown impact of the significant uncertainty in the shape of the initial released mass on the runoutdistanceandontheoverallshapeofthedepositraisesquestionsabouttherelevanceof these approaches. The impact of the initial scar geometry on flow and distribution of the deposits is studied here using satellite data and numerical modeling of theoretical landslides, and Martian landslides informed by geomorphological analysis, by varying the initial scar geometry from spoon‐shaped to steep wall geometry. Our results show that the runout distance is a very robust parameter that is only slightly affected by the change in the geometry of the initial scar. On the contrary, the lateral extent of the deposit is shown to be controlled by the scar geometry, providing unique insights into the initial landsliding conditionsonMarsandmakesitpossibletoaccuratelyrecoverthevolumeinitiallyinvolved, an essential ingredient for volume balance calculation. A feedback analysis of Valles Marineris landslides can be drawn, showing good agreement between numerical results and geomorphological analysis; the geometry of the initial scar inferred from numerical modeling is strongly correlated with the regional tectonic history in Valles Marineris area.

Long-runout landslides usually cause a significant loss of life and property because of their hypermobility and immense energy to travel long distances at high velocities, attracting a global focus on the dynamics and mechanism of long-runout landslides. In the past few decades, a great number of past studies on long-runout landslides have seen a surge in a range of innovative ideas and vigorous debates contributing to the advancement of understanding the dynamics and mechanism of the hypermobility of long-runout landslides. As a consequence, a review of the dynamics of long-runout landslides has been conducted by comprehensively and systematically summarizing the data and achievements of long-runout landslides over the past few decades in terms of the phenomenon and characteristics, mobility, dynamic process, dynamic mechanism, and models of long-runout landslides. This review would be of great significance in providing a comprehensive reference in understanding the dynamics of long-runout landslides.

Dynamics of landslides

Progressive slope steepening can trigger episodic dry sand avalanches, resembling landslides commonly observed in natural environments. Similarly, gradual river incision can induce periodic slope instability and failures. To thoroughly investigate the impact of gradual river incision on catchment topography and slope dynamics, we conduct a series of idealized dry sandbox experiments. This simple setup is expected to provide a deeper understanding of the patterns and dynamics of landslides in mountainous regions.In the experiments, dry sand is removed by applying negative suction pressure through a nozzle traversing prescribed paths over the topography. This process simulates river channel incision into the sand substrate and triggers avalanches on adjacent slopes. The experimental setup consists of a simple box filled with dry sand, equipped with a suction mechanism inspired by the extrusion nozzles used in 3D printing. Unlike 3D printing, where material is added, negative pressure at the nozzle is used to extract material instead.To validate the system, we first employ a vertically descending suction nozzle at a controlled rate to produce an expanding conical pit. This simple setup allows us to test the suction mechanism and ensure consistent material removal. Subsequently, we simulate river incision by utilizing an idealized curved path designed to mimic the geometry of an incising river. Initially, the nozzle was manually guided along this path to replicate the incision process. In later experiments, a computer-controlled traversing system is implemented to ensure greater precision and reproducibility.We then explore imposed motions along the main river channel and incorporate tributaries to explore the river incision processes. The results, including the formation of ridges, avalanches, and slope adjustments, are analyzed and compared with computational predictions derived from an eikonal model. This comparison provides valuable insights into the behavior of slopes under conditions of gradual river incision and elucidates the mechanisms driving slope instability and morphological evolution in natural catchments.

Landslides threaten more than before the urbanized areas and are a worldwide growing problem for the already affected communities and the local authorities committed to landslide risk management and mitigation. For this reason, it is essential to analyze landslide dynamics and environmental conditioning factors. Various techniques and instruments exist for landslide investigation and monitoring. Out of these, Multi-temporal Synthetic Aperture Radar Interferometry (MT-InSAR) techniques have been widely used in the last decades. Their capabilities are enhanced by the availability of the active Sentinel-1 mission, whose 6-day revisiting time enables near real-time monitoring of landslides. Interferometric results, coupled with ground measurements or other approaches such as numerical modeling, significantly improve the knowledge of the investigated surface processes. In this work, we processed the C-band SAR images of the available European Space Agency (ESA) satellite missions, using MT-InSAR methods to identify the surface deformations related to landslides affecting the Iași Municipality (Eastern Romania). The results (i.e., velocity maps) point out the most active landslides with velocities of up to 20 mm/year measured along the satellite Line of Sight (LOS). Following, we focused on the most problematic landslide that affects the Țicău neighborhood and is well-known for its significant implications that it had. To better understand its behavior and the sensitivity of the displacements to the environmental factors (i.e., rainfall), we carried out 2D numerical modeling using a finite difference code. The simulated displacement field is consistent with the InSAR displacements and reveals the most active sectors of the landslide and insights about its mechanism.

The shear strength is a fundamental mechanical parameter that controls the occurrence and propagation of landslides. In pure clays, this parameter is temperature-dependent according to the clay’s mineral composition and hydro-mechanical boundary conditions. Landslide soils are typically heterogeneous mixtures with a variable content of clay minerals. Particularly for low-plasticity soils, the impact of changes in temperature on the mechanical response remains to be determined, and little can be said about possible macroscopic alterations of slope stability or landslide dynamics.In this study, we conducted ring-shear tests using natural soils from the Melamchi catchment in central Nepal, which suffered widespread instabilities and rainfall-induced debris flows. We performed experiments under typical landslide stress levels (50-150 kPa) in water-saturated conditions and under a constant rate of shearing (0.1 mm/min). We controlled the temperature during testing and performed a heating-cooling cycle (20-50-20 °C) only after attaining the residual shear condition. We prepared multiple samples from the same soil by retaining its finest portion under different cutoff grain sizes (0.125-0.020 mm) to evaluate the fine fraction's role in the thermo-shear response.As expected, we observed a decrease in shear strength with the clay fraction increasing. Samples with a coarser cutoff (and hence a lower clay fraction) did not exhibit any change in shear strength during the heating-cooling cycle. However, as the clay fraction increased, a heating-induced weakening emerged, corresponding to up to a 1° difference in friction angle in the samples with a 0.020 mm cutoff. In the specific case study, this weakening may be minor and will not affect evaluations of slope stability in simple limit equilibrium analyses, especially in the absence of explicitly accounting for spatial heterogeneities in soil properties and boundary conditions. Nevertheless, incorporating this effect into physically-based models, either entailing advanced soil constitutive models or equations for surface flows (both of which can include additional temperature-dependent parameters), may provide useful insights into the complexity of thermo-hydro-mechanical responses and their effects on landslides at the local and regional scales.

Precise estimations of greenhouse gas budgets for countries contribute to sharpened policies on the national and international level to tackle climate change. Soils pool a considerable amount of carbon and nitrogen within terrestrial ecosystems and a quarter of the Austrian terrestrial surface is dedicated to grassland. In the clay-rich Flysch zone thousands of landslides have been observed. We argue that a better understanding of mechanisms that lead to both phenomena — greenhouse gas fluxes and landslide dynamics — could provide insights into untangling the complexity of the soil carbon and nitrogen cycles and improve greenhouse gas models on active landslides. To achieve this, we enrich long-term observation of the two landslides in Gresten and Hofermühle, Lower Austria with monitoring of greenhouse gas in different soils, vegetation and land use and of landslide dynamics. Employment of non-steady-state chambers with combination of comprehensive physico-chemical soil analyses, vegetation and land use surveys reveal interconnections between greenhouse gas fluxes and landslide activity. Inclusion of land displacement data gained by inclinometer measurements link our geoecological findings with in-depth landslide movements. Hydrological soil properties, such as moisture content and water-filled pore space (WFSP), impact both greenhouse gas fluxes and landslide activity the most. Additionally, slow-moving landslides alter microrelief, which consequently affects the land use management in grasslands. We conclude that greenhouse gas fluxes and landslide activities not only share the common preconditionary factors, but also slow-moving landslides influence greenhouse gas fluxes indirectly. Hereby, land-use management is of crucial importance. These findings could ultimately improve current computational greenhouse gas models for territories prone to landslides and support climate policy development.

Eastern Part of the Czech Republic in the Outer Western Carpathians (OWC), particularly the Javorníky Mts. range along the Czech-Slovakian border, has been traditionally considered a geologically stable region with documented low contemporary seismic activity. However, recent geomorphological analyses and field investigations reveal compelling evidence of prehistoric large-scale and highly mobile mass movements, potentially triggered by paleo-earthquakes. This study integrates high-resolution LiDAR mapping, field investigations and trenching, geophysical surveys, radiometric dating, and numerical modeling to reconstruct the paleo-seismic characteristic of the region. We identified those paleo-landslide features using high-resolution LiDAR data and assumed their relationship to past seismic activity by their close vicinity to a Holocene polyphase surface rupture of the Lidečko Fault. LiDAR mapping combined with the Electrical Resistivity Tomography (ERT) analyses provide valuable insights into the structural geology, lithology, failure mechanisms of paleo-landslides. Trenching and dating techniques, including radiocarbon and optically stimulated luminescence (OSL), help establish the timing of these events and their possible seismic triggers. Structural analysis of the Lidečko revealed the active strike-slip and oblique reverse kinematics with surface ruptures and liquefaction features, supporting the hypothesis of the landslides´ earthquake-induced origin.Distinct three generations of landslides were identified as half-ellipsoidal depleted source zones about 400 m long, 200 wide and about 25 m deep with remnants of their accumulations at the toe and in the valley floor and different state of subsequent reworking by shallow slope processes. The fluidized mass was displaced for up to 1 km, of which up to 600 meters comprised totally flat riverbed. Radiometric dating of associated landslide-dam deposits revealed the landslides´ ages about 91 ka, 45 ka and 1.8 ka ago.To accurately assess their potential coseismic origin, synthetic seismic acceleration data derived from waveform records in the OWC region is integrated into both Newmark Displacement Analysis (NDA) with the Velocity-Dependent Friction Law (VDFL) and the distinct element numerical modeling. This combined approach improves the simulation of rock mass and landslide dynamics under seismic loading conditions and ensures a more precise analysis of earthquake-induced slope processes. Specifically, PFC3D numerical modeling is employed to reconstruct the paleo-topography and simulate the long run-out behavior of paleo-landslides under various earthquake scenarios. These simulations provide deeper insights into the triggering mechanisms and movement patterns of such landslides.The estimated magnitudes of past earthquakes challenge assumptions about the OWC's seismic stability and suggest significant unrecorded events. This study improves understanding of earthquake-induced landslides in stable regions and offers a framework for assessing long-term seismic hazards. The methods used can be applied to other areas with uncertain seismic histories, helping to better understand the connection between tectonics and landscape evolution.The research was funded by the Grant Agency of the Czech Republic (GC22-24206J) and Taiwanese National Technological and Science Council (MOST/NTSC 111-2923-M-008-006-MY3).

One and a half centuries after the founding of the IAG, geodetic imaging (GI) represents a golden age in geodesy, and a bonanza of never-before-available quantitative information for research in related fields of science. Airborne LiDAR (light detection and ranging) observations, and such derived products as ‘bare earth’ digital elevation models, are being used to study: earthquake deformation fields, fault slip rates, folding mechanisms, landslide dynamics, channel network evolution, soil mantle development, bedrock surface cracking, landscape response to tectonics, lava flow fluxes, marsh evolution, salmon habitat, beach erosion, forestry, and archaeological sites. LiDAR technology is still developing rapidly, with high priority being given to multi-color systems, and miniaturization that will enable the deployment of LiDAR in remotely piloted aircraft, a.k.a., drones. As such technological improvements become operational new scientific problems will be brought within reach of an increasingly diverse community of researchers.

The study of landslide dynamics is a fundamental tool to aid in proactive responses to reduce landslide disaster risk, which has become intensified by the increasing development of mountain slopes due to economic and population growth in many developing countries Landslide risk is also increasing due to extreme rainfalls caused by changing climate in many landslide-prone areas in the world. Natural landslide phenomena would have initially attracted attention through the observation of ground deformation/movement which changed the natural scenery in the mountains and sometimes affected people’s living areas before the era of industrialization. Geological and geomorphic studies started at this stage. Civil engineering works to construct roads, bridges, dams and river banks, and engineering works to mine hard rocks, limestones, coals, valuable metal and minerals developed during the industrialization of human society. They caused artificial geomorphic changes and often triggered landslides. To avoid triggering landslides due to human activities and to stabilize landslide slopes, industry-centered landslide studies were developed. The main tool was slope stability analysis based on soil and rock mechanics. In the post-industrialization period, people-centered disaster risk reduction studies integrating natural sciences, social sciences and engineering to save people’s lives have developed. The initial global scale initiative was the International Decade for Natural Disaster Reduction (IDNDR) from 1st January 1990 to the end of 1999. Peoples are rarely killed by either slow-speed or short-distance landslides. The landslides affecting people’s lives are rapid and long-runout landslides, which they cannot escape from. Landslide studies to assess the velocity and travel distance of landslides must be developed. This is topic is landslide dynamics. This paper describes the core concepts and the important aspects of landslide dynamics as the fundamentals of ISDR-ICL Landslide Teaching Tools, which aim to support landslide risk reduction efforts through reliable landslide risk assessment and the early warning and land-use changes.

We propose a new model for landslide dynamics under the assumption of a delay failure mechanism. Delay failure is simulated as a delayed interaction between adjacent blocks, which mimics the relationship between the accumulation and feeder part of the accumulation slope. The conducted research consisted of three phases. Firstly, the real observed movements of the landslide were examined to exclude the existence or the statistically significant presence of background noise. Secondly, we propose a new mechanical model of an accumulation landslide dynamics, with introduced delay failure, and with variable friction law. Results obtained indicate the onset of a transition from an equilibrium state to an oscillatory regime if delayed failure is assumed for different cases of slope stiffness and state of homogeneity/heterogeneity of the slope. At the end, we examine the influence of different frictional properties (along the sliding surface) on the conditions for the onset of instability. Results obtained indicate that the increase of friction parameters leads to stabilization of sliding for homogeneous geological environment. Moreover, increase of certain friction parameters leads to the occurrence of irregular aperiodic behavior, which could be ascribed to the regime of fast irregular sliding along the slope.

Open image in new window The main aim of this study is to test the effectiveness of Sentinel-1A Synthetic Aperture Radar (SAR) data in monitoring scarcely urbanized slopes affected by slow-moving instabilities. To this end, geological and geomorphological surveys were carried out, satellite SAR data were processed and a GPS network system was installed. The study area, named Rovegliana, is located in the North-Eastern sector of the Italian pre-Alps. Rovegliana slopes are covered by eluvial, colluvial and landslide debris deposits which are mainly affected by superficial phenomena such as creep and soil slips. In situ surveys and Advanced Differential SAR Interferometry (A-DInSAR) processing of ERS, ENVISAT and COSMO Sky-MED SAR data pointed out that the instabilities are active with constant velocities up to 10 mm/year. Only the central and eastern sectors of the area were subjected to an acceleration after an exceptional rainfall event occurred in November 2010. GPS monitoring started in October 2015 and has been implemented through four campaigns made up of high precision geodetic measures of possible soil deformations of 22 vertices of a Global Navigation Satellite System (GNSS) static network. These vertices have been connected by a network to obtain a robust system. Comparing results from historical interferometric data, GPS measurements and interferometry processing of Sentinel SAR data acquired in the period 2015–2016, make it possible to verify if Sentinel data, characterized by short revisiting time, can be used as useful tool to define the spatio-temporal evolution of the recorded instabilities, overcoming the limits of applying interferometric techniques caused by temporal decorrelation due to the presence of vegetation cover, increasing the possibility to obtain significant information about landslide dynamics from SAR data. Moreover, we expect that the high number of planned acquisitions will improve the accuracy of deformation measurements.

<p>Fjord environments are subject to submarine mass wasting events due to their steep slopes, high sedimentation rates, and tectonic activity driven by glacial-isostatic rebound. In specific cases, these events can generate tsunami waves whose coastal heights are strongly influenced by the physiography, both subaerial and submarine, of the fjord. Here we present modeling simulations of a potential tsunami initiated by a submarine landslide in Pangnirtung Fjord, eastern Baffin Island (Nunavut, Canada). Pangnirtung Fjord, a 43 km long, 1 to 3 km wide, and 165 m deep fjord, is fed by numerous rivers that transport sediment from the surrounding high-relief, partially glaciated landscape. Collapse of the Kolik River delta, situated directly across from the hamlet of Pangnirtung, is the likely cause of the largest submarine landslide (2.1 km<sup>2</sup>) identified in the fjord using multibeam bathymetric data and 3.5 kHz sub-bottom profiles collected in 2019. The mapped landslide extends across the flat basin and features a blocky deposit directly downslope of the delta. The landslide dynamics, the consequent water waves generation and propagation were simulated by means of codes developed by the Tsunami Research Team of Bologna University. The landslide parameters characterizing the downslope motion have been retrieved by matching the landslide dynamics with the observed deposit. As the landslide impulses to the water column are considered, the propagation of the waves inside the fjord is determined through the shallow water approximation of the Navier-Stokes set of equations. The waves reach the hamlet (3.5 km from the landslide source) in 200 s, and the surrounding fjord coasts in approximately 800 s. Maximum wave height values of approximately 2 m were modeled and used to construct an inundation map for the area, over a 2 m regularly spaced grid for the hamlet of Pangnirtung.</p>