Landslide Volume Research Articles

An analysis of the supply process of loose materials to mountainous rivers and gullies as a result of dry debris avalanches

A dry debris avalanche will produce different volumes of colluviums or depositions (loose materials), which can have a significant impact on mountainous rivers or gullies. The loose material supply process caused by a debris avalanche is an important issue for understanding secondary disasters that form via the coupling of water flow and loose materials. Two flumes were designed for laboratory tests of the loose materials supply process to rivers/gullies, and the related impact factors were analyzed. Experimental results show that the supply of loose materials is a continuous process that directly relates to the avalanche’s mass movement processes. The sliding masses with smaller particle sizes are more sensitive to the flume slope and exhibited a longer supply time. The time-consuming for the debris avalanche travel in the flume decreased with the increasing particle size (such as flume B, time-consuming is decreased 0.2 s when the particle size increased from <1.0 to 20–60 mm), landslide volume and flume slope (flume A, consuming 1.6–2.1 s when flume slope is 29° decreased to consuming 1.3–1.5 s when flume slope is 41°), which means the increasing mobility of loose materials. The total supply time increased with the increasing landslide volume or decreasing particle size and flume slope. An empirical model for the process is presented based on numerous laboratory tests and numerical simulations, which can successfully describe the supply process for loose materials to a river/gully. The supply process of loose materials to mountainous gully from a dry debris avalanche is controlled by the material compositions of sliding masses, topographical conditions, landslide volume and bed friction, where large-volume debris avalanches that occur in mountainous river regions are more likely to obstruct the river flow and form a landslide-dammed lake.

Deslizamiento Las Torres, volcán Irazú, Costa Rica: definición de su volumen y su dirección preferencial de movimiento

Se ha efectuado un estudio de inestabilidad de laderas en el sector oeste del volcán Irazú, el cual comprende la definición de un marco geomorfológico, la aplicación de la técnica de elementos finitos conocida como reducción de la resistencia al corte, para analizar la estabilidad del sector definido como en proceso de desestabilización y la definición del volumen de material potencialmente deslizable. El Deslizamiento Activo Río Sucio Oeste (DARSO) se identificó como el único deslizamiento activo en el sector estudiado. Adicionalmente, se ha establecido que el Deslizamiento Inactivo Retes (DIR) muestra evidencias de reactivación en el sector de su escarpe principal. Por otra parte, no se espera que la geoforma DSPD presente un movimiento hacia el suroeste en el futuro y las deformaciones mostradas por el modelo de un desprendimiento hacia el noroeste se tornan significativas una vez que a las propiedades de resistencia al corte se les aplica un factor de reducción de 1,30; desarrollándose el colapso de la ladera en una dirección de deslizamiento hacia el noroeste. Si se considera que el factor de seguridad es de alrededor de 1,30, se debe contar con un factor de disparo para que el deslizamiento se desarrolle. Finalmente, el volumen del deslizamiento se estima en 7 millones de metros cúbicos.

Empirical prediction for travel distance of channelized rock avalanches in the Wenchuan earthquake area

Abstract. Rock avalanches are extremely rapid, massive flow-like movements of fragmented rock. The travel path of the rock avalanches may be confined by channels in some cases, which are referred to as channelized rock avalanches. Channelized rock avalanches are potentially dangerous due to their difficult-to-predict travel distance. In this study, we constructed a dataset with detailed characteristic parameters of 38 channelized rock avalanches triggered by the 2008 Wenchuan earthquake using the visual interpretation of remote sensing imagery, field investigation and literature review. Based on this dataset, we assessed the influence of different factors on the runout distance and developed prediction models of the channelized rock avalanches using the multivariate regression method. The results suggested that the movement of channelized rock avalanche was dominated by the landslide volume, total relief and channel gradient. The performance of both models was then tested with an independent validation dataset of eight rock avalanches that were induced by the 2008 Wenchuan earthquake, the Ms 7.0 Lushan earthquake and heavy rainfall in 2013, showing acceptable good prediction results. Therefore, the travel-distance prediction models for channelized rock avalanches constructed in this study are applicable and reliable for predicting the runout of similar rock avalanches in other regions.

Debris-flow modeling at Meretschibach and Bondasca catchments, Switzerland: sensitivity testing of field-data-based entrainment model

Abstract. Debris-flow volumes can increase due to the incorporation of sediment into the flow as a consequence of channel-bed erosion along the flow path. This study describes a sensitivity analysis of the recently introduced RAMMS (Rapid Mass Movements) debris-flow entrainment model, which is intended to help solve problems related to predicting the runout of debris flows. The entrainment algorithm predicts the depth and rate of erosion as a function of basal shear stress based on an analysis of erosion measurements at the Illgraben catchment, Switzerland (Frank et al., 2015). Starting with a landslide-type initiation in the RAMMS model, the volume of entrained sediment was calculated for recent well-documented debris-flow events at the Bondasca and the Meretschibach catchments, Switzerland. The sensitivity to the initial landslide volume was investigated by systematically varying the initial landslide volume and comparing the resulting debris-flow volume with estimates from the field sites. In both cases, the friction coefficients in the RAMMS runout model were calibrated using the model, whereby the entrainment module was (1) inactivated to find plausible values for general flow properties by adjusting both coefficients (ξ and μ) and then (2) activated to further refine coefficient μ, which controls erosion (patterns). The results indicate that the model predicts plausible erosion volumes in comparison with field data. By including bulking due to entrainment in runout models, more realistic runout patterns are predicted in comparison to starting the model with the entire debris-flow volume (initial landslide plus entrained sediment). In particular, lateral bank overflow – not observed during these events – is prevented when using the sediment entrainment model, even in very steep (≈ 60–65 %) and narrow (4–6 m) torrent channels. Predicted sediment entrainment volumes are sensitive to the initial landslide volume, suggesting that the model may be useful for both reconstruction of historical events and the modeling of scenarios as part of a hazard analysis.

A comparative study between popular statistical and machine learning methods for simulating volume of landslides

This study attempts to compare popular statistical methods (linear, logarithmic, quadratic, power and exponential functions) with machine learning methods (multi-layer perceptron (MLP), radial base function (RBF), adaptive neural-based fuzzy inference system (ANFIS) and support vector machine (SVM)) for simulating the volume of landslides based on their surface area (VL~AL) in the Kurdistan province, Iran. Performances of the models were validated using some commonly error functions including the Adjusted R2, F-test and AIC (Akaike Information Criteria). The results showed that the power model demonstrates the best performance compared to other statistical methods whereas the ANFIS model outperforms other machine learning approaches. Furthermore, the comparative results showed that machine learning methods indicate better performances than simple statistical methods for simulating the volume of landslides in the study area. In practice, the outputs of this research can help managers and investigators decrease the cost of field surveys and measurements of volumes of landslides in landslide hazard management projects.

Earthquakes drive focused denudation along a tectonically active mountain front

Earthquakes cause widespread landslides that can increase erosional fluxes observed over years to decades. However, the impact of earthquakes on denudation over the longer timescales relevant to orogenic evolution remains elusive. Here we assess erosion associated with earthquake-triggered landslides in the Longmen Shan range at the eastern margin of the Tibetan Plateau. We use the Mw7.9 2008 Wenchuan and Mw6.6 2013 Lushan earthquakes to evaluate how seismicity contributes to the erosional budget from short timescales (annual to decadal, as recorded by sediment fluxes) to long timescales (kyr to Myr, from cosmogenic nuclides and low temperature thermochronology). Over this wide range of timescales, the highest rates of denudation in the Longmen Shan coincide spatially with the region of most intense landsliding during the Wenchuan earthquake. Across sixteen gauged river catchments, sediment flux-derived denudation rates following the Wenchuan earthquake are closely correlated with seismic ground motion and the associated volume of Wenchuan-triggered landslides (r2>0.6), and to a lesser extent with the frequency of high intensity runoff events (r2=0.36). To assess whether earthquake-induced landsliding can contribute importantly to denudation over longer timescales, we model the total volume of landslides triggered by earthquakes of various magnitudes over multiple earthquake cycles. We combine models that predict the volumes of landslides triggered by earthquakes, calibrated against the Wenchuan and Lushan events, with an earthquake magnitude–frequency distribution. The long-term, landslide-sustained “seismic erosion rate” is similar in magnitude to regional long-term denudation rates (∼0.5–1 mm yr−1). The similar magnitude and spatial coincidence suggest that earthquake-triggered landslides are a primary mechanism of long-term denudation in the frontal Longmen Shan. We propose that the location and intensity of seismogenic faulting can contribute to focused denudation along a high-relief plateau margin.

Influence of topography and volume on mobility of loess slides within different slip surfaces

Mobility of loess slides has been evaluated using an empirical approach based on a detailed field investigation and remote sensing image interpretation. For all the loess slides, the affected area increases with increasing loess slides volume. From the statistical analysis it is seen that the travel distance has an increasing trend, while the coefficient of friction has a decreasing trend with the increase in landslide volume. Landslide volume determine its travel distance and coefficient of friction, that can be shown with a regression equation having simple power law form, which indicates that the mobility of loess slides increases with increasing volumes. By analogy, the greater the energy of the sliding loess mass, the stronger is the mobility of loess slide. A plot of the travel distance of loess slide versus fall height shows a significant positive power law correlation indicating the increase in mobility of loess slide with fall height. The negative power law correlation observed between the travel distance and slope inclination implies that the mobility decreases with the increase of slope inclination. Three datasets of loess slides characterized by different slip surfaces were distinguished. The red clay contact landslides have the strong mobility than landslides in loess and bedrock contact.

Coupling fluvial processes and landslide distribution toward geomorphological hazard assessment: a case study in a transient landscape in Japan

This study quantified the relationship among deep-seated gravitational slope deformations (DGSDs), landslides, and river rejuvenation in the upper reaches of the Kumano River in the Kii Mountains of Japan, an area of frequent bedrock landslides. River profiles and hillslope landforms were examined, and high-resolution digital elevation models (DEMs) were used to identify DGSDs and landslides. Many of the deep-seated landslides were associated with rainstorms in 1889 and 2011. Landslide volumes were related to landslide areas on the basis of 52 deep-seated landslides that failed during the 2011 rainfall, providing basic data for landscape denudation and sediment yield. River rejuvenation occurred stepwise, incising moderate relief paleosurfaces and forming two series of knickpoints and V-shaped inner gorges that are up to 400-m deep. More than 65% of DGSDs and 75% of the landslides were located in association with the incised inner gorges along the peripheries of the paleosurfaces or were entirely contained within the inner gorges. DGSDs and landslides associated with the incised inner valley slopes tended to be larger than those developed within the paleosurfaces and may be long-term transient hillslope responses to river incision. Hillslope undercutting caused by rejuvenated river incision may play an important role in long-term slope stability and distribution of mass movements, and could serve as an indicator of landslide hazard.

Estimación del volumen de los depósitos asociados a deslizamientos a través de geoformas, en el flanco SW del volcán Pico de Orizaba, Puebla-Veracruz

Landslides that occur along river systems are very common and have the potential to cause harm to human, to its infrastructure or affect their socio-economic activity. This dynamic is magnified in territories where morphological contrasts are very marked; as in the border between the mountains and subhorizontal land. This is especially true for volcanic terrains where volcanic activity can trigger voluminous landslides along stream systems by sector and flank collapse and where high seasonal rainfall on terrains covered by poorly consolidated materials produces small but hazardous landslides and debris flows that occur continually along stream systems during the volcanic repose periods. Those type of landslides can deliver volumes of hundreds and millions cubic meters that create a potentially hazardous situation for people and property down the valleys. The study of landslides in volcanic terrains through a Geographic Information System (gis) and under a geomorphological criterion, have allowed to develop a comprehensive methodology linked to the development of multi-temporal inventory, with susceptibility and volume estimation of displaced material. The aim of this research is to develop a method (protocol) for landslide susceptibility and landslide volume assessment of potentially unstable volcanic landscapes in order to be helpful in mitigating landslide damages to human settlements. Pico de Orizaba volcano is the highest volcano in Mexico. The volcano has been affected by large flank collapse landslides throughout its geological history. These events have partially destroyed the cone as it happened in Bezymianny volcano and St. Elena volcano. In this volcano, the risk associated with landslide and debris flows, is increased by the growing of human settlements along the hillslopes and by the subsistence agriculture, and deforestation. This situation is favored by a volcanic calm that has lasted 147 years, approximate. These conditions create a dangerous situation for more than 360 000 people living on the southern flank of the volcano Pico de Orizaba, where landslides along the hillslopes and the river system threaten towns like Cordova, Orizaba, Rio Blanco, Nogales and Ciudad Mendoza. Today the most common and dangerous landslides are associated with unconsolidated volcanic deposits and heavy seasonal rains.In this paper, the cause, distribution, and link between landslides and the volcanic landscape relief susceptibility are analyzed. Similarly, the volume of displaced material is estimated in order to characterize the landslide instability in volcanic terrains. The Río El Estado watershed on the southwestern flank of Pico de Orizaba volcano is selected to describe and analyze susceptible areas of gravitational processes. The study area allows to show a systematic methodology for landslide mapping and volume calculation in areas with scarce information. The methodology encompasses three main stages of analysis. In the first stage, background information is collected to provide context and establish a generalized characterization of landslide processes, landsforms and volumes within the study area. Background information includes the following maps: topographic, geologic, land use, climate, slope, slope curvature, contributing area, flow direction, saturation, reclassified hypsomety, reclassified slope, and morphography. By retrieval and on-off switching of the background information in the gis, a base map is created to assist in the digitizing of landslides. The base map and the theoretical aspects of the geomorphological mapping help to develop a conceptual base of support for mapping landslides. Landslides are digitized directly into a geographic information system (gis), and in parallel, a spatial geodatabase of landslides attributes (eg. size, volume, activity, landslide type, etc.) is constructed. Previous landslide mapping in the study area is verified and new landslides are added to the landslide inventory.Once the locations of landslides are mapped and evaluated, similar potential landslide areas are grouped into individual landforms. During the second stage, the volcanic relief is analyzed under a geomorphological criterion based on aerial photographs, fieldwork, and detailed mapping and the results are adjusted to the landslide hazard zonation protocol from Washington State, Department of Natural Resources, USA. For each volcanic landform a semi-quantitative susceptibility rating is obtained from values that correspond to the total area of landslides and the number of landslides within each landform; and they are normalized for the total period of time spanned between sets of aerial orthophotographs (fourteen years period). These normalized variables are referred to as the landslide area rate and the landslide frequency rate, respectively.Finally, for the third stage, the volume of material delivered by landslides to the main river is estimated by using an empirical area-volume relationship. The results allow us to understand the long-term evolution of the fluvial system in southwestern flank of Pico de Orizaba volcano. They also show a useful mapping methodology for developing inventories, assessing susceptibility, and estimated volumes associated with landslides in volcanic terrains.

An offline–online Web-GIS Android application for fast data acquisition of landslide hazard and risk

Abstract. Regional landslide assessments and mapping have been effectively pursued by research institutions, national and local governments, non-governmental organizations (NGOs), and different stakeholders for some time, and a wide range of methodologies and technologies have consequently been proposed. Land-use mapping and hazard event inventories are mostly created by remote-sensing data, subject to difficulties, such as accessibility and terrain, which need to be overcome. Likewise, landslide data acquisition for the field navigation can magnify the accuracy of databases and analysis. Open-source Web and mobile GIS tools can be used for improved ground-truthing of critical areas to improve the analysis of hazard patterns and triggering factors. This paper reviews the implementation and selected results of a secure mobile-map application called ROOMA (Rapid Offline–Online Mapping Application) for the rapid data collection of landslide hazard and risk. This prototype assists the quick creation of landslide inventory maps (LIMs) by collecting information on the type, feature, volume, date, and patterns of landslides using open-source Web-GIS technologies such as Leaflet maps, Cordova, GeoServer, PostgreSQL as the real DBMS (database management system), and PostGIS as its plug-in for spatial database management. This application comprises Leaflet maps coupled with satellite images as a base layer, drawing tools, geolocation (using GPS and the Internet), photo mapping, and event clustering. All the features and information are recorded into a GeoJSON text file in an offline version (Android) and subsequently uploaded to the online mode (using all browsers) with the availability of Internet. Finally, the events can be accessed and edited after approval by an administrator and then be visualized by the general public.

Volume determination of the Selo landslide complex (SW Slovenia): integrating field mapping, ground penetrating radar and GIS approaches

The Selo landslide complex in the Vipava Valley (SW Slovenia) is a large fan-shaped sedimentary body that differs significantly from other slope deposits in the area in its exceptional size and considerable runout length. The landslide is predominantly composed of carbonate gravel deposited on a flysch paleo-relief. To determine the volume and geometry of the landslide and its potential source area, we integrated geological mapping, ground penetrating radar (GPR) and GIS techniques. The landslide deposits cover an area of about 10 km2 with an average thickness of 10 m (maximum thickness reaching 56 m) and a maximum length of 5500 m. The volume of carbonate gravel was estimated from geological cross sections and GPR profiles. The base and top surfaces were interpolated by inverse distance and kriging methods, for which the Cut/Fill method was used in ESRI ArcGIS to determine the original landslide volume before the erosion. The estimated original volume is 190 × 106 m3. The recent volume after the erosion is 96 × 106 m3. The calculated volume of the Selo landslide, angle of reach θ = 10° and H/L ratio of 0.18 are in accordance with data for landslides of a comparable size. The most reasonable explanation for the development of the Selo landslide complex is a slope collapse involving the breakdown of the rock mass and the development of a high-mobility rock avalanche.

The La Pintada landslide, Guerrero, Mexico: hints from the Pre-Classic to the disasters of modern times

A landslide triggered by rainfall derived from hurricane Manuel took place on Independence Day, 16 September 2013, in the small village of La Pintada in Guerrero state, Mexico. There were 78 fatalities, 8 missing persons and 8 injured. Estimated cumulative rainfall in La Pintada during 1–16 September was 278.6 mm. The depth of the failure surface was 8 m in the middle and lower areas and 10–14 m at the top. Landslide volume was estimated at ∼125,000 m3. This paper provides a general account of the factors leading to hillslope instability in the region of La Pintada in terms of hazard understanding and offers a hypothetical view of the historical-cultural aspects of the foundation of the village, as a potential expression of past landslide activity.

A seismological overview of the April 25, 2015 Mw7.8 Nepal earthquake

This paper aims to determine the damage distribution and to analyze the available strong motion records of the April 25, 2015 Nepal earthquake and its eight aftershocks. For this purpose, an earthquake investigation team was dispatched to Nepal from May 6 to 11, 2015 to evaluate the damages of the epicentral region and the four affected cities containing Kathmandu, Bhaktapur, Gorkha, and Pokhara. Based on the observations from the damages to the built environment, an iso-intensity map is prepared on the EMS-98 intensity scale in which the maximum intensity in the epicentral region is estimated to be about VIII. However, based on the geological and geotechnical evidences such as landslide volumes and ground fissures, the maximum intensity can be inferred about IX or X on the International Union for Quaternary Research (INQUA) intensity scale. In addition, the available strong motion data of the 2015 Nepal mainshock and its eight large aftershocks recorded at the KATNP accelerometric station in Kathmandu were processed and analyzed. In order to investigate the probable site effects, the Fourier amplitude spectra (FAS) of the horizontal north-south (N) and east-west (E) components and the average of them (H avg) were divided to the FAS of the vertical (Z) component and thus, the $$ \raisebox{1ex}{$ N$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. $$ , $$ \raisebox{1ex}{$ E$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. $$ , $$ \raisebox{1ex}{${H}_{\mathrm{avg}}$}\!\left/ \!\raisebox{-1ex}{$ Z$}\right. $$ spectral ratios were calculated. Based on these horizontal to vertical spectral ratios, a low-frequency peak at about 0.2–0.3 Hz (3.5–5-s period) is observed clearly in all the records. Accordingly, the repeated results might imply site amplification due to the thick alluvial deposits and the high groundwater level at the KATNP accelerometric station within the Kathmandu basin. It should be noted that all the horizontal to vertical spectral ratios of the aftershocks show a high peak at around 1.5–3 Hz, which is missed in the horizontal to vertical spectral ratio of the mainshock. On the other hand, considering the low angle of the causative fault plane, a near-source directivity effect on the fault normal direction (here, the vertical component) of the April 25, 2015 mainshock rupture may exist. Therefore, vertical to horizontal spectral ratios ( $$ \raisebox{1ex}{$ Z$}\!\left/ \!\raisebox{-1ex}{$ N$}\right. $$ and $$ \raisebox{1ex}{$ Z$}\!\left/ \!\raisebox{-1ex}{$ E$}\right. $$ ) were also calculated to find the vertical peak more clearly. The figures confirmed a peak at the frequency of 1.5–3 Hz in the mainshock spectra which is not repeated on the aftershock spectra and thus can probably be attributed as the pulse of directivity effect toward Kathmandu. This inferred directivity pulse can be also well distinguished on the velocity and displacement time histories of the mainshock.

The size, distribution, and mobility of landslides caused by the 2015 Mw7.8 Gorkha earthquake, Nepal

Coseismic landslides pose immediate and prolonged hazards to mountainous communities, and provide a rare opportunity to study the effect of large earthquakes on erosion and sediment budgets. By mapping landslides using high-resolution satellite imagery, we find that the 25 April 2015 Mw7.8 Gorkha earthquake and aftershock sequence produced at least 25,000 landslides throughout the steep Himalayan Mountains in central Nepal. Despite early reports claiming lower than expected landslide activity, our results show that the total number, area, and volume of landslides associated with the Gorkha event are consistent with expectations, when compared to prior landslide-triggering earthquakes around the world. The extent of landsliding mimics the extent of fault rupture along the east-west trace of the Main Himalayan Thrust and increases eastward following the progression of rupture. In this event, maximum modeled Peak Ground Acceleration (PGA) and the steepest topographic slopes of the High Himalaya are not spatially coincident, so it is not surprising that landslide density correlates neither with PGA nor steepest slopes on their own. Instead, we find that the highest landslide density is located at the confluence of steep slopes, high mean annual precipitation, and proximity to the deepest part of the fault rupture from which 0.5–2Hz seismic energy originated. We suggest that landslide density was determined by a combination of earthquake source characteristics, slope distributions, and the influence of precipitation on rock strength via weathering and changes in vegetation cover. Determining the relative contribution of each factor will require further modeling and better constrained seismic parameters, both of which are likely to be developed in the coming few years as post-event studies evolve. Landslide mobility, in terms of the ratio of runout distance to fall height, is comparable to small volume landslides in other settings, and landslide volume-runout scaling is consistent with compilations of data on larger slope failures. In general, the size ratios of landslide source area to full landslide area are smaller than global averages, and hillslope length seems to largely control runout distance, which we propose reflects a topographic control on landslide mobility in this setting. We find that landslide size dictates runout distance and that more than half of the landslide debris was deposited in direct connection with stream channels. Connectivity, which is defined as the spatial proximity of landslides to fluvial channels, is greatest for larger landslides in the high-relief part of the High Himalaya. Although these failures are less abundant than those at lower elevations, they may have a disproportionate impact on sediment dynamics and cascading hazards, such as landslide reactivation by monsoon rainfall and landslide dams that lead to outburst floods. The overall high fluvial connectivity of coseismic landsliding in the Gorkha event suggests coupling between the earthquake cycle and sediment/geochemical budgets of fluvial systems in the Himalaya.

Earthquake-triggered landslides along the Hyblean-Malta Escarpment (off Augusta, eastern Sicily, Italy) – assessment of the related tsunamigenic potential

Abstract. Eastern Sicily is affected by earthquakes and tsunamis of local and remote origin, which is known through numerous historical chronicles. Recent studies have put emphasis on the role of submarine landslides as the direct cause of the main local tsunamis, envisaging that earthquakes (in 1693 and 1908) did produce a tsunami, but also that they triggered mass failures that were able to generate an even larger tsunami. The debate is still open, and though no general consensus has been found among scientists so far, this research had the merit to attract attention on possible generation of tsunamis by landslides off Sicily. In this paper we investigate the tsunami potential of mass failures along one sector of the Hyblean-Malta Escarpment (HME). facing Augusta. The HME is the main offshore geological structure of the region running almost parallel to the coast, off eastern Sicily. Here, bottom morphology and slope steepness favour soil failures. In our work we study slope stability under seismic load along a number of HME transects by using the Minimun Lithostatic Deviation (MLD) method, which is based on the limit-equilibrium theory. The main goal is to identify sectors of the HME that could be unstable under the effect of realistic earthquakes. We estimate the possible landslide volume and use it as input for numerical codes to simulate the landslide motion and the consequent tsunami. This is an important step for the assessment of the tsunami hazard in eastern Sicily and for local tsunami mitigation policies. It is also important in view of tsunami warning system since it can help to identify the minimum earthquake magnitude capable of triggering destructive tsunamis induced by landslides, and therefore to set up appropriate knowledge-based criteria to launch alert to the population.

The Vulnerability of People to Landslides: A Case Study on the Relationship between the Casualties and Volume of Landslides in China.

The lack of a detailed landslide inventory makes research on the vulnerability of people to landslides highly limited. In this paper, the authors collect information on the landslides that have caused casualties in China, and established the Landslides Casualties Inventory of China. 100 landslide cases from 2003 to 2012 were utilized to develop an empirical relationship between the volume of a landslide event and the casualties caused by the occurrence of the event. The error bars were used to describe the uncertainty of casualties resulting from landslides and to establish a threshold curve of casualties caused by landslides in China. The threshold curve was then applied to the landslide cases occurred in 2013 and 2014. The validation results show that the estimated casualties of the threshold curve were in good agreement with the real casualties with a small deviation. Therefore, the threshold curve can be used for estimating potential casualties and landslide vulnerability, which is meaningful for emergency rescue operations after landslides occurred and for risk assessment research.

The Potential Role of Tree Diversity in Reducing Shallow Landslide Risk.

Recently, interest in utilizing ecosystems for disaster risk reduction has increased, even though there remains considerable uncertainty regarding the role of ecosystems in buffering against natural hazards. This ecosystem role can be considered an ecosystem service. Although a strong body of evidence shows that biodiversity enhances ecosystem services, there are only a few studies of the relationship between biodiversity and the role of the ecosystem in reducing the risk of natural disasters. To explore the desired state of an ecosystem for disaster risk reduction we applied the finding that biodiversity enhances ecosystem services to evaluate the role of woody vegetation in reducing the frequency and severity of shallow landslides. Using information related to shallow landslides and woody vegetation in Japan as a case study, we compared the severity of shallow landslides (i.e., landslide volume) with tree species richness. Although we provide no direct evidence that tree species richness reduces shallow landslide volume, we found that the predictability of the model, which evaluated relationships between landslide volume and environmental variables in watersheds throughout the Japanese Archipelago, increased with tree species richness. This finding suggests that biodiversity is likely associated with shallow landslide risk reduction, emphasizing a possible reduction of spatial and temporal uncertainty in the roles of woody vegetation. Our study identifies a need for socioecological systems to build new approaches found on the functionality of such ecosystems.

SPH propagation back-analysis of Baishuihe landslide in south-western China

BackgroundLandslides and landslide dams are a major natural hazard causing high socioeconomic risk in inhabited mountainous areas. This is also true for vast parts of south-western China, which are highly prone to slope failures due to several factors, such as a humid climate with high precipitation in the summer months, geological predisposing factors with highly weathered sedimentary rocks and a high seismicity. In order to assess possible run-out distances and the potential of landslides to block rivers, it is crucial to understand which factors influence landslide propagation and how they can be quantified. Since it is often difficult or impossible to measure related geotechnical parameters in the field, their back analysis with a numerical modelling approach can be useful. In this study a numerical modelling analysis was implemented for the case of a complex landslide in south-western China, which transformed into a debris flow and blocked the river and a major road after heavy rainfall. For this purpose a quasi-3D smoothed particle hydrodynamics (SPH) model that can account for geotechnical slope parameters, run-out distance, velocities, and deposition heights was used. Based on field observations regarding initial landslide volume and final deposition volume, height, and length, the mechanical properties of the landslide were estimated in a back-analysis.ResultsThrough stepwise parameter optimisation the best reconstruction of the observed deposition phenomena could be achieved considering an initial landslide volume of about 0.5 million cubic meters, a triggering height of 15 m, an height of the water table equal to half the soil thickness, initial pore water pressures of about 0.6 of the liquefaction value, and non-negligible bed entrainment, which resulted in a deposition with a volume of about one million cubic meters, a length of 615 m and a mean height of 11 m. Compared to models with other parameter combinations, here the total error was minimal, while the final deposition dimensions were only slightly overestimated with regard to the observations in the field.ConclusionsThe paper outlines the potential for quantitatively interpreting the field evidence for the propagation of a complex flow-like landslide and related cascading processes, such as landslide damming. However, the analysis should take into account multiple features of the whole processes, such as the initial conditions at the landslide source area, the propagation pattern, the total volume mobilised, and the deposition characteristics. By doing so, the estimated model parameters can be implemented in future studies for the forward modelling of events at the same site, or other sites along this slope, in order to assess the potential of future river blockings through landslide deposits.

Landslide Susceptibility Analysis (LSA) using Deterministic Model (Infinite Slope) (DESSISM) in the Kota Kinabalu Area, Sabah, Malaysia

A practical application for landslide susceptibility analysis (LSA) based on two dimensional deterministic slope stability (infinite slope model) (DESSISM) was used to calculate factor of safety (FOS) and failure probabilities for the area of Kota Kinabalu, Sabah. LSA is defined as quantitative or qualitative assessment of the classification, volume (or area) and spatial distribution of landslides which exist or potentially may occur in an area. In this paper, LSA value can be expressed by a FOS, which is the ratio between the forces that make the slope fail and those that prevent the slope from failing. An geotechnical engineering properties data base has been developed on the basis of a series of parameter maps such as effective cohesion (C’), unit weight of soil ,)?(depth of failure surface (Z), height of ground water table (Zw), Zw/Z dimensionless (m), unit weight of water ,)w?(slope surface inclination (s) and effective angle of shearing resistance (?). Taking into consideration the cause of the landslide, identified as groundwater change, the maximum groundwater level recorded corresponding to the actual situation of the most recent landslide is considered in this study. The highest probability value of the various scenarios was selected for each pixel and final LSA map were constructed. It has been found from this study that s and Zw parameters have the higher influence on landslide instability. The result validation between the examined LSA map and result of landslide distribution map (LDM) were evaluated. This DESSISM had higher prediction accuracy. The prediction accuracy is 84%. The resulting LSA maps can be used by local administration or developers to locate areas prone to landslide area, determine the land use suitability area and to organize more detailed analysis in the identified “hot spot” areas.

Tsunamis generated by long and thin granular landslides in a large flume

AbstractIn this experimental study, granular material is released down slope to investigate landslide‐generated waves. Starting with a known volume and initial position of the landslide source, detailed data are obtained on the velocity and thickness of the granular flow, the shape and location of the submarine landslide deposit, the amplitude and shape of the near‐field wave, the far‐field wave evolution, and the wave runup elevation on a smooth impermeable slope. The experiments are performed on a 6.7 m long 30° slope on which gravity accelerates the landslides into a 2.1 m wide and 33.0 m long wave flume that terminates with a 27° runup ramp. For a fixed landslide volume of 0.34 m3, tests are conducted in a range of still water depths from 0.05 to 0.50 m. Observations from high‐speed cameras and measurements from wave probes indicate that the granular landslide moves as a long and thin train of material, and that only a portion of the landslide (termed the “effective mass”) is engaged in activating the leading wave. The wave behavior is highly dependent on the water depth relative to the size of the landslide. In deeper water, the near‐field wave behaves as a stable solitary‐like wave, while in shallower water, the wave behaves as a breaking dissipative bore. Overall, the physical model observations are in good agreement with the results of existing empirical equations when the effective mass is used to predict the maximum near‐field wave amplitude, the far‐field amplitude, and the runup of tsunamis generated by granular landslides.