Impact Of Landslides Research Articles

Interaction between submarine landslides and suspended pipelines with a streamlined contour

ABSTRACTRecently, the security and stability of submarine pipelines have attracted much attention in ocean engineering. In this paper, pipelines with a streamlined contour (wedge, airfoil, double-ellipse, and arc-angle hexagon) are designed in hopes of defending against the impact of submarine landslides, and the computational fluid dynamics (CFD) approach is used to investigate the interaction between submarine landslides and streamlined pipelines. The results show that the peak interactional force is more representative of the hazard level of pipelines imposed by submarine landslides. It is also found that the streamlined pipelines possess a significant advantage in reducing the drag force and lift force of landslide–pipeline interaction with a maximum lessening percentage of 66.32 and 40.17%, compared with a conventional circular pipeline. In addition, the influence of applying streamlined pipelines to engineering is briefly discussed, and the empirical equation for estimating the drag force and lift force of streamlined pipelines induced by landslides is recommended based on the numerical test results.

A hybrid DEM-SPH model for deformable landslide and its generated surge waves

Reservoir bank landslide and its generated surge waves are catastrophic hazards which may give rise to additional sedimentation, destroy hydraulic structures, and even cause fatalities. Since this process is very complex involving landslide impact, wave generation and propagation, it cannot be well captured with traditional numerical approaches. In this paper, a hybrid DEM-SPH model is presented to simulate landslide and to reproduce its generated surge waves. This model consists of discrete element method (DEM) for solid phase and smoothed particle hydrodynamics (SPH) for fluid phase as well as drag force and buoyancy for solid–fluid interaction. Meanwhile, the δ-SPH algorithm is employed to eliminate spurious numerical noise on the pressure field. Submarine rigid block slide is numerically tested to validate the proposed hybrid model, and the computed wave profiles exhibit a satisfactory agreement with the experiment. The hybrid model is further extended towards the submarine granular deformable slide which generates smaller and less violent surge waves. Kinetic and potential energy of both solid and fluid particle system are extracted to throw a light upon the process of landslide water interaction from an energy perspective. Finally, a sensitivity analysis on particle friction coefficient indicates that the lubrication of the solid particles is another important effect influencing the underwater landslide movement in addition to the drag effect.

Runup of granular landslide‐generated tsunamis on planar coasts and conical islands

AbstractLarge‐scale physical model experiments of tsunamis generated by granular landslides and volcanic flank collapses are conducted to study the wave runup on both the hill slope laterally adjacent to the landslide and an opposing hill slope. A pneumatic landslide tsunami generator was deployed on planar and convex conical hill slopes to simulate deformable landslides with various geometries and kinematics. On the landslide hill slope, maximum runup and rundown were observed in the landslide impact region followed by adjacent second maxima after the lateral waves were fully formed. The runup and rundown decayed asymptotically from the second maxima. In the conical island scenario, a localized runup amplification was measured on the lee side of the island. Outside the landslide impact region, the effects of the landslide granulometry on the lateral wave runup are minimal. The lateral wave runup on the planar hill slope was generally larger than on the convex conical hill slope outside the landslide impact region. The convex conical hill slope traps less lateral wave energy. The zeroth mode of the edge wave dispersion relation matched the first and second lateral waves on the planar hill slope and the first wave on the convex conical hill slope. Predictive equations for the laterally propagating wave characteristics are derived and a method to predict the runup on an opposing hill slope is presented. The predictive wave and runup equations are benchmarked against the 2007 landslide‐generated tsunami in Chehalis Lake, British Columbia, Canada.

COMBINING FUZZY LOGIC AND INFORMATION THEORY FOR PRODUCING A LANDSLIDE SUSCEPTIBILITY MODEL

The main objective of the present study was to develop a landslide susceptibility model by combining Fuzzy logic and Information Theory in order to estimate the spatial probability of landslide manifestation, in the mountains of central Tzoumerka, Greece. Specifically, Fuzzy logic was enabled for weighting the landslide related variables based on expert knowledge and in respect to landslide susceptibility, while the Shannon’s entropy index, an index from Information Theory, was calculated to weight the significance of each landslide related variable based on the available data. The final landslide susceptibility map was produced by applying the weighted sum method. Engineering lithological units, slope angle, slope aspect, distance from tectonic features, distance from river network and distance from road network were among the six landslide related variables that were included in the landslide database used in the training phase. The landslide inventory map was constructed by interpreting aerial photographs, satellite images and field surveys and was separated into two datasets, one for training and one for validating the model. The outcomes of the validation process illustrated that the developed methodology efficiently provided the most susceptible areas and was in good agreement with the actual landslide locations. The area under the curve was estimated to be for the training and validating datasets 0.7575 and 0.7828 respectively. The produced landslide susceptibility map could be regarded from local and national authorities as a valuable mean to evaluate strategies or to prevent and mitigate the impact of landslides. Keywords: slope stability, fuzzy weighting, Shannon’s entropy index, Tzoumerka, Greece.

Impact of landslides on soil characteristics: Implications for estimating their age

The slopes of Mount Elgon, a complex volcano at the border between Uganda and Kenya, are frequently affected by landslides with disastrous effects on the livelihood of its population. Since local people greatly depend on the land for crop production, this paper examines if and how fast physico-chemical characteristics in landslide scars recover. A chronosequence of 18 landslides covering a period of 103years was sampled in order to explore differences between topsoil inside and outside landslide scars. For each landslide, two topsoil samples were taken within the landslide and two in nearby undisturbed soils to compare their physico-chemical characteristics. Samples inside the landslides were located at the transition zone between the depletion and accumulation zone, which is situated at the contact line between the plan concave and plan convex section of the landslide. No differences were found for available phosphorus, Ca2+, Mg2+ content or for the fine earth texture. Recent landslides had however lower content of soil organic carbon (OC) and K+, and higher content of rock fragments and Na+ than the adjacent soils. Soil OC content increased significantly with age and reached levels of the corresponding undisturbed soils after ca. 60years. Older landslides had even higher OC contents than soils adjacent to the landslide. Hence landslide scars act as local carbon sink. We suggest that the occurrence of rock fragments in the topsoil is a useful indicator for mapping past landslides. Moreover, the difference in soil OC content between landslide scars and adjacent soil could be used for estimating the age of landslides in data-poor regions.

Fuzzy gamma operator model for preparing landslide susceptibility zonation mapping in parts of Kohima Town, Nagaland, India

Growing population and expansion of settlements over hilly areas have largely increased the impact of landslide. This paper deals with the use of Geoinformatics technology and Fuzzy Gamma Operator model to map the landslide susceptibility zones in part of Kohima Town, Nagaland. For this study, eight landslide inducing parameters such as slope gradient, slope aspect, curvature, elevation, land use and land cover, drainage density, lineament density, and topographical wetness index were considered and prepared with the help of toposheet, high resolution satellite imagery such as World View II, LISS IV, DEM data and field data. Landslide inventory was the first step for the geospatial database generation which involves the mapping of past landslide details. Landslide susceptibility maps were generated by calculating relationship between the landslide inducing factors with past landslide locations using frequency ratio and fuzzy gamma operator model. The ratios were normalized between the range of 0 and 1 to obtain fuzzy membership values. The landslide susceptibility zonation (LSZ) map were prepared by integrating all the causative factors with fuzzy membership values and classified into five different susceptibility classes based on Jenks natural breaks classification viz. very high (37.51%), high (32.21%), moderate (20.97%), low (7.97%), and very low (1.34%). The LSZ map were compared with the landslide inventory map and validated with best prediction accuracy using area under curve (AUC) with the accuracy level and R-Index.

Assessing future changes in the occurrence of rainfall-induced landslides at a regional scale

According to the fifth report of the Intergovernmental Panel on Climate Change, an increase in the frequency and the intensity of extreme rainfall is expected in the Mediterranean area. Among different impacts, this increase might result in a variation in the frequency and the spatial distribution of rainfall-induced landslides, and in an increase in the size of the population exposed to landslide risk. We propose a method for the regional-scale evaluation of future variations in the occurrence of rainfall-induced landslides, in response to changes in rainfall regimes. We exploit information on the occurrence of 603 rainfall-induced landslides in Calabria, southern Italy, in the period 1981–2010, and daily rainfall data recorded in the same period in the region. Furthermore, we use high-resolution climate projections based on RCP4.5 and RCP8.5 scenarios. In particular, we consider the mean variations between a 30-year future period (2036–2065) and the reference period 1981–2010 in three variables assumed as proxy for landslide activity: annual rainfall, seasonal cumulated rainfall, and annual maxima of daily rainfall. Based on reliable correlations between landslide occurrence and weather variables estimated in the reference period, we assess future variations in rainfall-induced landslide occurrence for all the municipalities of Calabria. A +45.7% and +21.2% average regional variation in rainfall-induced landslide occurrence is expected in the region for the period 2036–2065, under the RCP4.5 and RCP8.5 scenario, respectively. We also investigate the future variations in the impact of rainfall-induced landslides on the population of Calabria. We find a +80.2% and +54.5% increase in the impact on the population for the period 2036–2065, under the RCP4.5 and RCP8.5 scenario, respectively. The proposed method is quantitative and reproducible, thus it can be applied in similar regions, where adequate landslide and rainfall information is available.

Evolution of Mass Movements near Epicentre of Wenchuan Earthquake, the First Eight Years.

It is increasingly clear that landslides represent a major cause of economic costs and deaths in earthquakes in mountains. In the Wenchuan earthquake case, post-seismic cascading landslides continue to represent a major problem eight years on. Failure to anticipate the impact of cascading landslides could lead to unexpected losses of human lives and properties. Previous studies tended to focus on separate landslide processes, with little attention paid to the quantification of long-term evolution of multiple processes or the evolution of mass movements. The very active mass movements near the epicentre of the Wenchuan earthquake provided us a unique opportunity to understand the complex processes of the evolving cascading landslides after a strong earthquake. This study budgets the mass movements on the hillslopes and in the channels in the first eight years since the Wenchuan earthquake and verify a conservation in mass movements. A system illustrating the evolution and interactions of mass movement after a strong earthquake is proposed.

Flow-type landslide fragility of reinforced concrete framed buildings

Flow-type landslides may be triggered by several events such as heavy rainfalls, typically producing huge losses. Landslide risk may be rationally evaluated and mitigated with probabilistic approaches. In this paper, physical vulnerability of reinforced concrete buildings to flow-type landslides is assessed. Fragility analysis was carried out by assuming flow velocity as intensity measure, several damage states, and different mechanical models for beams, columns and masonry infill walls. Uncertainties in landslide impact loading, material properties, size and reinforcement of members, and capacity models were taken into account. Both earthquake-resistant and gravity-load designed framed buildings were assessed as being representatives of two building classes. Based on Monte Carlo simulation and a specific fragility analysis methodology, a set of landslide fragility curves were derived. Analysis results show that landslide fragility significantly depends on the presence and type of infill walls, which influences both out-of-plane and in-plane failure modes of walls themselves and RC frames. In addition, the proposed landslide fragility curves demonstrate that seismic design of RC buildings also plays a key role in the mitigation of their flow-type landslide fragility.

Numerical Simulation of Impulsive Water Waves Generated by Subaerial and Submerged Landslides Incidents in Dam Reservoirs

The water wave generation by a freely falling rigid body is examined in this paper. Landslides on the margins of dam reservoirs may generate large waves that can produce flooding over the banks or overtopping the dam crest. In the present investigation, landslide generated waves are studied using a numerical model based on Navier-Stokes equations. Impulse wave amplitude, period, energy is studied in this work. The effects of bed slope angle on energy conversion from slide into wave are also investigated, and the numerical model we used in this study is the full three dimensional commercial code Flow-3D. Results of the Navier-Stokes model show that waves generated are highly dependent upon the details of slide mechanism and kinematics. Numerical solutions for the velocity fields, pressure distributions, and turbulence intensities in the vicinity of the falling rigid body are also presented. Results show that the general pattern of wave in all cases is the same but the amplitude and period are different. Data analysis shows that the maximum wave crest amplitude in subaerial induced waves is strongly affected by bed slope angle, landslide impact velocity, thickness, kinematics and deformation and by landslide shape.

Impact of earthquake-induced landslide on the habitat suitability of giant panda in Wolong, China

Massive geological landslides and unstable landslide areas were triggered by the 2008 Wenchuan earthquake. These landslides caused deaths, damaged infrastructure and threatened endanger species. This study analyzed the impact of landslides on giant pandas and their habitats from the following aspects: threatening pandas’ lives, damaging pandas’ habitat, influencing giant panda behavior, increasing habitat fragmentation; the final aspect, and blocking gene flow by cutting off corridors. A habitat suitability map was created by integrating the landslide factors with other traditional factors based on a logistics regression method. According to the landslide inventory map, there are 1313 landslides, 818 rock debris flows, 117 rock avalanches and 43 mud flows occurred in the study area. A correlation analysis indicated that landslides caused the pandas to migrate, and the core landslides within 1 km2 had greater influence on panda migration. These core landslides primarily occurred in mid-altitude regions characterized by high slopes, old geological ages, large areas and large rock mass volumes. The habitat suitability assessment results for the Wolong Natural Reserve had better prediction performance (80.9%) and demonstrated that 14.5%, 15.9%, 20.5%, 47.6% and 1.5% of the study area can be classified as very high, high, moderate, low and very low giant panda suitability areas, respectively. This study can be used to inform panda and panda habitat research, management and protection during post-quake reconstruction and recovery periods in China.

A novel flexible barrier for landslide impact in centrifuge

Experimental investigations aimed at understanding the impact mechanism of debris-resisting flexible barriers have been hindered by limitations associated with small-scale modelling and poor temporal predictability of real landslide debris events. The geotechnical centrifuge provides a means to simulate landslide impact by scaling the flow volume, impact energy and stress state appropriately. Nonetheless, a technical challenge remains in simulating large non-linear deformation of flexible barriers observed in a prototype. In this letter, the development and verification of a novel model flexible barrier for centrifuge testing are described. This model barrier consists of a series of spring elements to simplify the complex loading behaviour and to capture the key bilinear load–displacement response of a prototype flexible barrier. By measuring the dynamic response of barrier cables, no obvious peak impact load was captured. The shear strength of dry granular flow results in an attenuating pileup impact mechanism. It is apparent that the geometry of the debris front has a strong influence on impact response. In addition, as debris impacts and deposits behind the barrier, the debris–barrier interaction results in an active failure mode of the deposited material, which is a surrogate of reduced pressure acting on the barrier.

A statistical study of precursor activity in earthquake-induced landslides

In this paper, a statistical study of precursor activity in earthquake-induced landslides by means of spring block models is presented. The dynamic behavior of the rock/soil slope can be studied by using the statistics of the different distribution of slip events at the interface between the soil and the bedrock. It is shown that by introducing earthquake-induced cracks of certain length within the interface, a robust 2D spring-block model can be formulated for studying triggered landslides. A cellular automaton is built in order to examine the dynamic behavior and the stability of rock/soil slopes during and after a neighboring earthquake. The type and nature of the failure plane, as well as the triggering intensity, is studied. The different dynamic evolution modes of the slope can be mapped to different statistical evolution characteristics of specific shape parameters of the corresponding incremental displacements’ distributions. Within the proposed context, spring-block models can be used in order to understand, predict and minimize the impact of catastrophic landslides triggered by earthquakes.

A Simplified Numerical Approach for the Prediction of Rainfall‐Induced Retrogressive Landslides

AbstractRetrogressive landslides are common geological phenomena in mountainous areas and on onshore and offshore slopes. The impact of retrogressive landslides is different from that of other landslide types due to the phenomenon of retrogression. The hazards caused by retrogressive landslides may be increased because retrogressive landslides usually affect housing, facilities, and infrastructure located far from the original slopes. Additionally, substantial geomorphic evidence shows that the abundant supply of loose sediment in the source area of a debris flow is usually provided by retrogressive landslides that are triggered by the undercutting of water. Moreover, according to historic case studies, some large landslides are the evolution result of retrogressive landslides. Hence the ability to understand and predict the evolution of retrogressive landslides is crucial for the purpose of hazard mitigation. This paper discusses the phenomenon of a retrogressive landslide by using a model experiment and suggests a reasonably simplified numerical approach for the prediction of rainfall‐induced retrogressive landslides. The simplified numerical approach, which combines the finite element method for seepage analysis, the shear strength reduction finite element method, and the analysis criterion for the retrogression and accumulation effect, is presented and used to predict the characteristics of a retrogressive landslide. The results show that this numerical approach is capable of reasonably predicting the characteristics of retrogressive landslides under rainfall infiltration, particularly the magnitude of each landslide, the position of the slip surface, and the development processes of the retrogressive landslide. Therefore, this approach is expected to be a practical method for the mitigation of damage caused by rainfall‐induced retrogressive landslides.

Simple criteria for ploughing and runout in post-failure evolution of submarine landslides

This paper extends shear band propagation analysis of slope failures to the investigation of ploughing and runout phenomena in submarine landslides. The ability to predict the two different modes of post-failure landslide evolution is critical for determining the tsunami hazard and type of landslide impact on offshore structures. The proposed analysis is based on the analogy between ploughing and spreading failures. It uses the energy balance approach to develop the criterion for progressive shear band propagation driven by accumulation of sliding material on top of the stable slope. This criterion is then combined with the kinematic passive block mechanism to produce analytical ploughing failure criteria formulated in terms of the critical rise in the seabed level. If the minimum rise of the seabed level at which ploughing can take place is larger than the maximum possible free-standing step in the seabed surface, the first passive failure block will start crumbling over top the stable zone causing the landslide to runout. Application of the derived criteria to the analysis of observed geomorphological features is demonstrated using an example of a paleolandslide complex in the Caspian Sea.

Landslide Risk Reduction in the United States—Signs of Progress

Scientific literature is replete with papers describing advances in applying new technologies to the study of landslides and advances in our understanding of factors affecting landslide occurrence, distribution, and movement. Far fewer papers look at how this knowledge is implemented to achieve landslide risk reduction. State and local governments exercise the greatest control on how landslide risk reduction is accomplished. Data generated from a questionnaire to state geological surveys, review of their agency Web sites, and two case studies demonstrate that progress has been made during the last 20 years in implementing actionable policy changes and programs to achieve a reduction is landslide risk in the United States. Progress is evident from the pivotal role played by state and local government in the areas of: (1) developing guidelines and training, (2) increasing public awareness and education, (3) implementing loss reduction measures, and (4) conducting emergency preparedness, response, and recovery. The number of states requiring registration for practicing geologists has nearly doubled during the last 20 years. This increase was accompanied by a shift from individual state tests as part of determining competency to a uniform national test. During this period, state geological surveys established Web sites as a primary means for promoting public awareness and education about landslide hazards. Measures reducing the impact of landslides have included providing information specific to residents and landowners, as well as supporting land-use planning efforts by local governments. Many state geological surveys are involved with emergency management of landslide hazards.

Model Experiment on Rainfall-induced Slope Failures with Moisture Content Measurements

The aim of the study is to investigate the controlling parameters of flowslide initiation experimentally through laboratory flume. Landslide is still a major frequent hazard in many parts of world despites of number of studies have been done related to slope failure. The most of slope failures are because of rainfall, as rainfall increases the moisture content and the pore pressure that reduce the shear strength of the soil. The slope after failure shows different modes, however every slope failure not produced same damages. The impact of landslide directly related to failure mode, velocity and distance travelled. There are different types of slope failure, however the flowslide is the most dangerous than other type of landslide. The flowslide type of failure occur suddenly without any warning and have fluid like motion that makes it more dangerous. In this study experiments conducted in laboratory through flume in order to investigate the parameters that initiate the flow type of failures. After the preparation of the model slope the sensors installed for the moisture content and the pore pressure. The moisture content measured with advanced sensor Imko Trime Pico-32. From the experiments it was observed that density of soil slope plays an important role in the initiation of flow type of failure. The pore pressure developed after the failure depends upon the thickness and velocity of sliding mass. The pore pressure and moisture content higher at the toe and the pore pressure higher at the base as compared to shallow depth. In the case of antecedent moisture conditions the runoff appeared at the horizontal part of the slope that erode the toe. The flowslide occur from smaller to higher depth of soil slope and significant depth of soil layer involved in flowslide type of failure. From the experiments it was observed that by installing the moisture sensors from toe to mid of the slope at the shallow depth the failure can be predicted.

Communication strategies to address geohydrological risks: the POLARIS web initiative in Italy

Abstract. Floods and landslides are common phenomena that cause serious damage and pose a severe threat to the population of Italy. The social and economic impact of floods and landslides in Italy is severe, and strategies to target the mitigation of the effects of these phenomena are needed. In the last few years, the scientific community has started to use web technology to communicate information on geohydrological hazards and the associated risks. However, the communication is often targeted at technical experts. In the attempt to communicate relevant information on geohydrological hazards with potential human consequences to a broader audience, we designed the POpoLazione A RISchio (POLARIS) website. POLARIS publishes accurate information on geohydrological risk to the population of Italy, including periodic reports on landslide and flood risk, analyses of specific damaging events and blog posts on landslide and flood events. By monitoring the access to POLARIS in the 21-month period between January 2014 and October 2015, we found that access increased during particularly damaging geohydrological events and immediately after the website was advertised by press releases. POLARIS demonstrates that the scientific community can implement suitable communication strategies that address different societal audiences, exploiting the role of mass media and social media. The strategies can help multiple audiences understand how risks can be reduced through appropriate measures and behaviours, contributing to increasing the resilience of the population to geohydrological risk.

Remote Sensing and GIS Application in Landslide Risk Assessment and Management

Small as well as large scale landslides are common in the Himalayas, especially in the monsoon period. This natural disaster occurs in all the physiographic divisions of the Himalayas. Landslide is the result of a wide variety of processes which include causative and triggering factors. A complete landslide hazard assessment requires an analysis of these factors leading to instability in the region. Therefore, there is a need of multidisplinary studies of landslide hazards, which combines geology, hydrogeology and, geomorphology. The landslide risk is directly associated with the development activities, which will increase with increasedurbanization and development, continued deforestation in landslideprone areas, increased precipitation and seismic activity. In order to reduce the landslide risk, it is necessary to understand the underlying the processes, study the impact of landslides on the socioeconomic development of the affected areas, prepare landslide hazard zonation maps to minimize the risk involved in developmental schemes, evolve a methodology for mitigation and control measures, monitor change in land use pattern and landslide occurrence, establishing early warning system and development landslide 'databank' on national level and identify potential landslides zones and prepare population maps of the critical areas.

Earthquake-triggered increase in biospheric carbon export from a mountain belt

On geological time scales, the erosion of carbon from the terrestrial biosphere and its burial in sediments can counter CO2 emissions from the solid Earth. Earthquakes may increase the erosion of this biospheric carbon and supply it to mountain rivers by triggering landslides, which rapidly strip hillslopes of vegetation and soil. Over the long term, elevated river sediment loads may promote more efficient carbon burial. However, riverine export of earthquake-mobilized carbon has remained poorly constrained. Here we quantify biospheric carbon discharge by the Zagunao River following a large earthquake with a unique set of samples collected before and after the A.D. 2008 M w 7.9 Wenchuan (China) earthquake. Radioactive and stable carbon isotopes are used to isolate the biospheric carbon, accounting for rock-derived organic carbon inputs. River discharge of biospheric carbon doubled in the downstream reaches, characterized by moderate landslide impact, following the earthquake. The rapid export of carbon from earthquake-triggered landslides appears to outpace its degradation on hillslopes while sediment loads are elevated. This means that enhanced river discharge of biospheric carbon following large earthquakes can link active tectonics to CO2 drawdown.