Landslide Dynamics Research Articles

Regional, tree-ring based chronology of landslides in the Outer Western Carpathians

Landslides are a type of mass wasting and denote any downslope movement of soil and rock under the influence of gravity; as such they can represent a dangerous natural hazard process, especially in case that they affect inhabited areas or transport infrastructure. Because the occurrence of landslides is typically favoured by terrain and lithological conditions, the process is frequently concentrated in relatively small, isolated regions exhibiting suitable initial conditions of terrain instability. Extensive regional assessments of landslide activity have been used in the past to uncover common triggers and process patterns, mostly in the aftermath of large, regional disasters. By contrast, however, regional reconstructions of past landslide activity have not been realized with dendrogeomorphic techniques, and with the aim to date past landslide histories over extended time periods and with annual dating precision. This study therefore aims at disentangling landslide dynamics at the regional scale (covering ca. 600 km2) by using growth-ring records of trees that grow on active landslides. The studied area of the Hostýnsko-vsetínská hornatina Mts. (Central Europe) is well known for its high landslide activity, but has so far been lacking a detailed chronology of past events. To this end, we dated past activity on 26 landslide bodies using tree-ring series from 1322 disturbed trees to reconstruct 327 landslide reactivations during the last century.The reconstructed landslide database allowed correlations between landslide types and their frequencies or occurrence, as well as inferences between selected morphometric parameters with landslide frequency and magnitude. We also observe periods of increased landslide activity (1940s, 1960s, 1980s, and 1990s) and events of regional importance (e.g., 1961, 1985, and 1997), as well as a significant decrease in landsliding during the last two decades.

Formation, breaching and flood consequences of a landslide dam near Bujumbura, Burundi

Abstract. This paper investigates the possible formation of a landslide dam on the Kanyosha River near Bujumbura, the capital of Burundi, as well as the interplay between the breaching of this landslide dam and the flooding along the river. We present an end-to-end analysis, ranging from the origin of the landslide up to the computation of flood waves induced by the dam breaching. The study includes three main steps. First, the mass movement site was investigated with various geophysical methods that allowed us to build a general 3-D model and detailed 2-D sections of the landslide. Second, this model was used for dynamic landslide process modelling with the Universal Distinct Element Code. The results showed that a 15 m high landslide dam may form on the river. Finally, a 2-D hydraulic model was set up to find out the consequences of the breaching of the landslide dam on flooding along the river, especially in an urban area located downstream. Based on 2-D maps of maximum water depth, flow velocity and wave propagation time, the results highlight that neglecting the influence of such landslide dams leads to substantial underestimation of flood intensity in the downstream area.

Dynamic analysis of a long-runout, flow-like landslide at Areletuobie, Yili River valley, northwestern China

In the analysis reported here, the catastrophic landslide at Areletuobie town in Xinyuan county is used as an example to investigate the formation mechanism and dynamics of a flow-like landslide in Yili River valley. At 0:30 a.m. on July 31, 2012, a catastrophic landslide occurred in Xinyuan, Xinjiang, northwestern China, resulting in the deaths of 28 people when the temporary sheds in the downstream adit mining area were destroyed and buried directly in the path of the landslide. The runout distance of the landslide was about 1800 m, and the accumulative volume was about 600,000 m3. The landslide can be categorized into three regions: the sliding source, impact-shoveling, and flow-accumulative regions. The stability of the landfill slope in the sliding source region was analyzed at two seepage stages of a long period of rain and a sudden heavy rainfall. To improve the accuracy of further hazard assessments of similar types of potential landslides in the same area, we simulated the kinematic and dynamic processes of the impact-shoveling region and the debris flow using the numerical model DAN-W and a combination of the frictional model and Voellmy model. The landslide moved for approximately 139 s downward along the valley, with a maximum velocity of 30 m s−1. This is a typical long-runout flow-like landslide. Finally, we conclude that the identification of the potential geological hazards at Yili River valley area is crucial to prevent any catastrophic flow-like landslide triggered by heavy rainfall. The identified indicators should be properly used as a scientific basis for classifying hazard areas of flow-like landslides as well as for monitoring and early recognition.

Combination of Rainfall Thresholds and Susceptibility Maps for Dynamic Landslide Hazard Assessment at Regional Scale

We propose a methodology to couple rainfall thresholds and susceptibility maps for dynamic landslide hazard assessment at regional scale. Both inputs are combined in a purposely-built hazard matrix to get a spatially and temporally variable definition of landslide hazard: while statistical rainfall thresholds are used to accomplish a temporal forecasting with very coarse spatial resolution, landslide susceptibility maps provide static spatial information about the probability of landslide occurrence at fine spatial resolution. The test site is the Northern part of Tuscany (Italy), where a recent landslide susceptibility map and a set of recently updated rainfall thresholds are available. These products were modified and updated to meet the requirements of the proposed procedure: the susceptibility map was reclassified and the threshold set was expanded defining additional thresholds. The hazard matrix combines three susceptibility classes (S1, low susceptibility; S2 medium susceptibility; S3 high susceptibility) and three rainfall rate classes (R1, R2, R3), defining five hazard classes, from H0 (null hazard) to H4 (high hazard). A key passage of the procedure is the appropriate calibration and validation of the matrix, letting the hazard classes have a precise meaning in terms of expected consequences and hazard management. The employ of the proposed procedure in a regional warning system brings two main advantages: (i) it is possible to better hypothesize when and where landslide are expected and with which hazard degree, thus fostering a more effective hazard and risk management (e.g. setting priorities of intervention); (ii) the spatial resolution of the regional scale warning system is markedly refined because from time to time the areas where landslides are expected represent only a fraction of the alert zone.

Radiocarbon Dating of the Dynamics of Landslides in the Upper Reaches of the Mzymta River Basin (Western Caucasus)

The article contains materials on the study of landslide deposits in the upper reaches of the Mzymta river basin. The results of 14C analysis showed that the youngest landslides are common on the southern slope of the Psekhako Ridge and date back to less than 200 and 390 ± 90, 400 ± 70 cal. years BP and more than 770 ± 150 cal. years BP. The most ancient landslide-collapse on the northern slope of the Aibga Ridge and dates back to 1110 ± 90 cal. years BP.

WCSPH with Limiting Viscosity for Modeling Landslide Hazard at the Slopes of Artificial Reservoir

This work illustrated an application of the FOSS code SPHERA v.8.0 (RSE SpA, Milano, Italy) to the simulation of landslide hazard at the slope of a water basin. SPHERA is based on the weakly compressible SPH method (WCSPH) and holds a mixture model, consistent with the packing limit of the Kinetic Theory of Granular Flow (KTGF), which was previously tested for simulating two-phase free-surface rapid flows involving water-sediment interaction. In this study a limiting viscosity parameter was implemented in the previous formulation of the mixture model to limit the growth of the apparent viscosity, thus saving computational time while preserving the solution accuracy. This approach is consistent with the experimental behavior of high polymer solutions for which an almost constant value of viscosity may be approached at very low deformation rates near the transition zone of elastic–plastic regime. In this application, the limiting viscosity was used as a numerical parameter for optimization of the computation. Some preliminary tests were performed by simulating a 2D erosional dam break, proving that a proper selection of the limiting viscosity leads to a considerable drop of the computational time without altering significantly the numerical solution. SPHERA was then validated by simulating a 2D scale experiment reproducing the early phase of the Vajont landslide when a tsunami wave was generated that climbed the opposite mountain side with a maximum run-up of about 270 m. The obtained maximum run-up was very close to the experimental result. Influence of saturation of the landslide material below the still water level was also accounted, showing that the landslide dynamics can be better represented and the wave run-up can be properly estimated.

Clayey Landslide Initiation and Acceleration Strongly Modulated by Soil Swelling

AbstractLargely unknown mechanisms restrain motion of clay‐rich, slow‐moving landslides that are widespread worldwide and rarely accelerate catastrophically. We studied a clayey, slow‐moving landslide typical of thousands in Northern California, USA, to decipher hydrologic‐mechanical interactions that modulate landslide dynamics. Similar to some other studies, observed pore‐water pressures correlated poorly with landslide reactivation and speed. In situ and laboratory measurements strongly suggested that variable pressure along the landslide's lateral shear boundaries resulting from seasonal soil expansion and contraction modulated its reactivation and speed. Slope‐stability modeling suggested that the landslide's observed behavior could be predicted by including transient swell pressure as a resistance term, whereas modeling considering only transient hydrologic conditions predicted movement five to six months prior to when it was observed. All clayey soils swell to some degree; hence, our findings suggest that swell pressure likely modulates motion of many landslides and should be considered to improve forecasts of clayey landslide initiation and mobility.

Characterizing groundwater flow in a translational rock landslide of southwestern China

Characterizing the groundwater flow pattern in a landslide would help to establish a monitor-warning system to predict the movement of a highly concealed and extremely hazard translational landslide. The complex fracture network in this type of landslide affects the rainfall infiltration process and the groundwater flow. In this paper, multi-tracer tests, injection tests and electrical resistivity tomography were used to investigate the hydrogeological characteristics and groundwater dynamics of the Kualiangzi translational rock landslide, which is located in the northeast of the Sichuan Basin, China. The study results indicate that there are two kinds of groundwater flow mode, in the landslide, the concentrated mode and the dispersed mode. Tracer and injection test results indicate that the groundwater flow in the landslide is mainly controlled by a vertical preferential flow pathway (concentrated mode), of which the direction is approximately perpendicular to the sliding direction of the landslide. The main runoff direction in the middle of this landslide is southwest according to electrical resistivity tomography. The hydraulic conductivity in the preferential direction is more than 3750 times larger than that perpendicular to the direction. The groundwater flow along the weathered sandstone and mudstone media in the vicinity of the slip surface is very slow (dispersed mode). The results reveal the existence of a preferential flow pathway. The hydrogeological conceptual model is considered as an unbounded domain with an anisotropic medium in the whole area. This hydrogeological model clearly describes the hydrological conditions, and can help establish a monitor-warning system in a translational landslide.

Modelling Martian landslides: dynamics, velocity, and paleoenvironmental implications

Landslides on Mars exhibit features such as steep collapse, extreme deposit thinning, and long runout. We study the flow dynamics of Martian landslides particularly in Valles Marineris, where landslides are among the largest and longest. Firstly, we observe that landslides in Valles Marineris share a series of features with terrestrial landslides fallen onto glaciers. The presence of suspected glacial and periglacial morphologies from the same areas of Valles Marineris, and the results of remote sensing measurements suggest the presence of ice under the soil and into the rock slopes. Thus, we explore with numerical simulation the possibility that such landslides have been lubricated by ice. To establish a plausible rheological model for these landslides, we introduce two possible scenarios. One scenario assumes ice only at the base of the landslide, the other inside the rock-soil. A numerical model is extended here to include ice in these two settings, and the effect of lateral widening of the landslide. Only if the presence of ice is included in the calculations, do results reproduce reasonably well both the vertical collapse of landslide material in the scarp area, and the extreme thinning and runout in the distal area, which are evident characteristics of large landslides in Valles Marineris. The calculated velocity of landslides (often well in excess of 100 m/s and up to 200 m/s at peak) compares well with velocity estimates based on the run-up of the landslides on mounds. We conclude that ice may have been an important medium of lubrication of landslides on Mars, even in equatorial areas like Valles Marineris.

New methodology for computing tsunami generation by subaerial landslides: Application to the 2015 Tyndall Glacier landslide, Alaska

AbstractLandslide‐generated tsunamis pose significant hazards and involve complex, multiphase physics that are challenging to model. We present a new methodology in which our depth‐averaged two‐phase model D‐Claw is used to seamlessly simulate all stages of landslide dynamics as well as tsunami generation, propagation, and inundation. Because the model describes the evolution of solid and fluid volume fractions, it treats both landslides and tsunamis as special cases of a more general class of phenomena. Therefore, the landslide and tsunami can be efficiently simulated as a single‐layer continuum with evolving solid‐grain concentrations, and with wave generation via direct longitudinal momentum transfer—a dominant physical mechanism that has not been previously addressed in this manner. To test our methodology, we used D‐Claw to model a large subaerial landslide and resulting tsunami that occurred on 17 October 2015, in Taan Fjord near the terminus of Tyndall Glacier, Alaska. Modeled shoreline inundation patterns compare well with those observed in satellite imagery.

Mapping slow-moving alpine landslides by UAV — Opportunities and limitations

Acquisition of unmanned aerial vehicle (UAV)-based imagery with resolution down to a few centimeters is challenging in alpine conditions. In recent years, UAV-based images have been used in an increasing number of case studies to monitor landslides. Processing of multitemporal high-resolution aerial images provides multitemporal 3D point clouds and multitemporal orthomosaics, which provide substantial information about slope dynamics. Surface processes deciphered from 3D point clouds and orthomosaic temporal sequences supplement on-site geophysical measurements of subsurface structures and dynamics by bringing key spatial and temporal constraints for process interpretation. However, accurate spatial mapping and successful analysis of surface dynamics are functions of the original optical image quality, which in turn relies on the flight system and configuration, camera characteristics and settings, as well as weather conditions and object texture. We evaluate the capabilities and limitations of UAV-based landslide dynamic mapping using illustrative examples gathered from a pioneering low-cost UAV-based imagery data set acquired at the slow-moving (mm-cm/d) Super-Sauze landslide (southeastern France) in 2008 and 2010, which included surface deformations (fissure development and kinematics) and surface conditions (soil moisture, erosion, and sedimentary processes) with very different certainty levels. In a few promising instances, processes detected in the 3D point clouds and orthomosaics could be correlated to geophysical data (passive seismic monitoring of landslide endogenous seismicity and electrical resistivity tomography for water content mapping), thereby validating the UAV analytical approach while providing constraints that improve interpretation of landslide dynamics.

Submarine landslides triggered by destabilization of high‐saturation hydrate anomalies

AbstractSubmarine landslides occur along continental margins at depths that often intersect the gas hydrate stability zone, prompting suggestions that slope stability may be affected by perturbations that arise from changes in hydrate stability. Here we develop a numerical model to identify the conditions under which the destabilization of hydrates results in slope failure. Specifically, we focus on high‐saturation hydrate anomalies at fine‐grained to coarse‐grained stratigraphic boundaries that can transmit bridging stresses that decrease the effective stress at sediment contacts and disrupt normal sediment consolidation. We evaluate slope stability before and after hydrate destabilization. Hydrate anomalies act to significantly increase the overall slope stability due to large increases in effective cohesion. However, when hydrate anomalies destabilize there is a loss of cohesion and increase in effective stress that causes the sediment grains to rapidly consolidate and generate pore pressures that can either trigger immediate slope failure or weaken the surrounding sediment until the pore pressure diffuses away. In cases where failure does not occur, the sediment can remain weakened for months. In cases where failure does occur, we quantify landslide dynamics using a rate and state frictional model and find that landslides can display either slow or dynamic (i.e., catastrophic) motion depending on the rate‐dependent properties, size of the stress perturbation, and the size of the slip patch relative to a critical nucleation length scale. Our results illustrate the fundamental mechanisms through which the destabilization of gas hydrates can pose a significant geohazard.

Energy-Based Analysis of Mechanisms of Earthquake-Induced Landslide Using Hilbert–Huang Transform and Marginal Spectrum

Based on the Hilbert–Huang Transform and its marginal spectrum, an energy-based method is proposed to analyse the dynamics of earthquake-induced landslides and a case study is presented to illustrate the proposed method. The results show that the seismic Hilbert energy in the sliding mass of a landslide is larger than that in the sliding bed when subjected to seismic excitations, causing different dynamic responses between the sliding mass and the sliding bed. The seismic Hilbert energy transits from the high-frequency components to the low-frequency components when the seismic waves propagate through the weak zone, causing a nonuniform seismic Hilbert energy distribution in the frequency domain. Shear failure develops first at the crest and toe of the sliding mass due to resonance effects. Meanwhile, the seismic Hilbert energy in the frequency components of 3–5 Hz, which is close to the natural frequency of the slope, is largely dissipated in the initiation and failure processes of the landslide. With the development of dynamic failure, the peak energy transmission ratios in the weak zone decrease gradually. This study offers an energy-based interpretation for the initiation and progression of earthquake-induced landslides with the shattering-sliding failure type.

The role of seismic triggering in a deep-seated mudstone landslide, China: Historical reconstruction and mechanism analysis

Deep-seated mudstone landslides are widely distributed in northwest China. The Zhengjiamo landslide occurred in 734CE near Taijing, Tianshui region. It was triggered by the main shock of the historical Ms=7.0734CE earthquake. The earthquake also induced a wide range of landslides in this area, with hundreds of fatalities and many houses destroyed by landslide debris. Based on a detailed field survey, borehole data, and mapping, a detailed geological reconstruction of the slope was achieved and the geo-mechanical features of the claystone involved in the landslide were obtained. Using the Particle Flow Code to simulate the mechanism of the Zhengjiamo landslide, the features of the landslide dynamics were obtained using a 5-stage model. During the landslide process, the slip mass at the front and upper edges exhibited higher mobility than at the rear and bottom edges. Furthermore, the contact bond strength of the sliding body gradually weakened. The model indicates that the particle bond strength has a larger influence on the maximum runout distance and landslide debris morphology than the type of weak intercalated layers. The slip mass presented a rotational slide pattern and remained on the slip plane throughout the sliding process. Finally, the earthquake uplifted the slope toe, which prevented the slip mass from gliding. The modelled scenario provided a reasonably good fit to the actual topography, verifying the modelling results. After the historical earthquake, with the clay minerals swelling and shrinking under rainfall and efflorescence conditions, the structure of the soft rock changed, contributing to the weakening of the sliding rock mass. The landslide gradually crept and evolved to its current topography.

Observations of dynamics of landslides within built-up slopes of ravines in the city of Dnipro

Observations of dynamics of landslides within built-up slopes of ravines in the city of Dnipro

A Compact Ground-Based Interferometric Radar for Landslide Monitoring: The Xerém Experiment

A real-time monitoring system based on ground-based synthetic aperture radar interferometry (GB-InSAR) were developed and deployed with the objective to gain understanding of landslide dynamics in an area in Xerém (district of Duque de Caxias - RJ, Brazil). The area is subjected to landslide risk and the deployed system aims to provide subsidies to the authorities to prepare actions related to prevention and evacuation, and serve as the basis for a future early-warning system in the framework of the Civil Defense of Duque de Caxias. The system consists of a compact and rugged X-band GB-InSAR newly developed by Bradar, Brazil. The processing and monitoring methodology are proposed. Two campaigns, totaling six days, were carried out. The acquisitions of the first campaign occurred without rain. In the second campaign, rain events, varying from light to torrential rainfall, occurred for a period of time, in subsequent days, during the radar acquisitions. New insights on landslide dynamics are revealed. The monitoring data show that, approximately 10 h after heavy rainfall, the terrain movement on a slope reached 4 mm/h during ca. 5 to 8 h, resulting in velocities of 20 to 32 mm/day.

Effects of Inter-Particle Frictional Coefficients on Evolution of Contact Networks in Landslide Process

During the process of landslide, its dynamic mechanism is important to understand and predict these kinds of natural hazard. In this paper, a new method, based on concepts of complex networks, has been proposed to investigate the evolution of contact networks in mesoscale during the sliding process of slope. A slope model was established using the discrete element method (DEM), and influences of inter-particle frictional coefficients with four different values on dynamic landslides were studied. Both macroscopic analysis on slope landslide and mesoanalysis on structure evolution of contact networks, including the average degree, clustering coefficient and N-cycle, were done during the process of landslide. The analysis results demonstrate that: 1) with increasing inter-particle frictional coefficients, the displacement of slope decreases and the stable angle of slope post-failure increases, which is smaller than the peak internal frictional angle; 2) the average degree decreases with the increase of inter-particle frictional coefficient. When the displacement at the toe of the slope is smaller, the average degree there changes more greatly with increasing inter-particle frictional coefficient; 3) during the initial stage of landslide, the clustering coefficient reduces sharply, which may leads to easily slide of slope. As the landslide going on, however, the clustering coefficient increases denoting increasing stability with increasing inter-particle frictional coefficients. When the inter-particle frictional coefficient is smaller than 0.3, its variation can affect the clustering coefficient and stable inclination of slope post-failure greatly; and 4) the number of 3-cycle increases, but 4-cycle and 5-cycle decrease with increasing inter-particle frictional coefficients.

ASCHFLOW - A dynamic landslide run-out model for medium scale hazard analysis

Landslides hazard analyses entail a scale-dependent approach in order to mitigate accordingly the damages and other negative consequences at the respective scales of occurrence. Medium or large scale landslide run-out modelling for many possible landslide initiation areas has been a very difficult task in the past. This arises from the inability of the run-out models to compute the displacement with a large amount of individual initiation areas as it turns out to be computationally strenuous. Most of the existing physically based run-out models have difficulties in handling such situations. For this reason, empirical methods have been used as a practical mean to predict landslides mobility at a medium scale (1: 10,000 to 1: 50,000). They are the most widely used techniques to estimate the maximum run-out distance and affected zones not only locally but also regionally. In this context, a medium scale numerical model for flow-like mass movements in urban and mountainous areas was developed. “AschFlow” is 2-D one-phase continuum model that simulates, the entrainment, spreading and deposition process of a landslide or debris flow at a medium scale. The flow is thus treated as a single phase material, whose behavior is controlled by rheology (e.g., Voellmy or Bingham). The model has been developed and implemented in a dynamic GIS environment. The deterministic nature of the approach makes it possible to calculate the velocity, height and increase in mass by erosion, resulting in the estimation of various forms of impacts exerted by debris flows at the medium scale. The developed regional model “AschFlow” was applied and evaluated in well documented areas with known past debris flow events. The “AschFlow” model outputs can be considered as an indication of areas possibly affected with a defined intensity for one or more landslide events. From a user perspective the “AschFlow” model can be seen as a standalone model which can be utilized for a first assessment of potentially impact areas.

Water content dynamics at plot scale – comparison of time-lapse electrical resistivity tomography monitoring and pore pressure modelling

Physically-based dynamic modelling of shallow landslide susceptibility rests on several assumptions and simplifications. However, the applicability of physically-based models is only rarely tested in the field at the appropriate scale. This paper presents results of a spray irrigation experiment conducted on a plot of 100m2 on an Alpine slope susceptible to shallow landsliding. Infiltrating precipitation applied at a constant rate (27.5mm/h for 5.3h) was monitored by means of 2D time-lapse electrical resistivity tomography, combined with time-domain reflectometry sensors installed at various depths. In addition, regolith characteristics were assessed by dynamic cone penetration tests using a light-weight cone penetrometer. The spray irrigation experiment resulted in a vertically progressing wetting front to a depth of 80–100cm. Below that, the unconsolidated material was already saturated by rainfall in the previous days. The observed mean resistivity reduction attributed to infiltrating water during irrigation was scaled to pressure head. Mean variations in pore pressure were reproduced by a linear diffusion model also used in physically-based dynamic landslide susceptibility modelling. Sensitive parameters (hydraulic conductivity and specific storage) were tested over selected value ranges and calibrated. Calibrated parameter values are within published and experimentally derived ranges. The results of the comparison of observations and model results suggest that the model is capable of reproducing mean changes of pore pressure at a suitable scale for physically-based modelling of shallow landslide susceptibility. However, small-scale variations in pore pressure that may facilitate the triggering of shallow landslides are not captured by the model.

Continuous monitoring of surface wave velocity at the Montevecchio earthflow (Forlì-Cesena Province, Northern Apennines)

The Montevecchio landslide is an active earthflow in the province of Forli-Cesena (Northern Apennines of Italy). In the last few years, this landslide reactivated several times. In order to investigate the landslide dynamics, two monitoring systems were installed by combining 3 permanent GPS stations (to measure landslide movement) and 4 geophones (to evaluate surface-wave velocity). In this paper we present the monitoring data collected during the last reactivation of the landslide (24th – 25th of May 2015). The geophones data show a clear relationship between surface-wave velocity (Vr) and displacement rate. In particular, a decrease of Vr value was observed just before an increase of velocity, while higher Vr values were detected when the landslide was slowing down. Moreover, a pressure sensor, buried at low depth beside the geophones, showed an increase in pore water pressure before the failure in correspondence of the critical rainfall event, and while the displacement rate increased the pore water pressure had a positive value (above the ground level), probably due to the undrained compression of the landslide material.