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About this book

This volume contains peer-reviewed papers from the Third World Landslide Forum organized by the International Consortium on Landslides (ICL) in June 2014. The complete collection of papers from the Forum is published in three full-color volumes and one mono-color volume.

Table of Contents

Frontmatter

Physical Modeling and Material Testing

Frontmatter

Introduction: Physical Modeling and Material Testing

Physical modeling and material testing play important roles for investigation, analysis, design and countermeasure planning of landslides. This introductory article briefly describes the nature of the diversified range of papers included in Section B1, Volume 2 of the Proceedings of the World Landslide Forum 3.

Binod Tiwari, Baoping Wen, Yasuhiko Okada, A. A. Virajh Dias

Laser Scanner Application in Monitoring Short-Term Slope Deformation

In order to develop a method to estimate the risk of secondary disaster during rescue activities at a site suffering from slope failure, a method for using repeated surveying by means of laser scanner installed on the ground is proposed. Eight experiments of slope failure including one carried in a natural slope were done. To improve the accuracy in the deformation, spatial stacking of data was adopted. Availability and reliability of the method, characteristics of deformation measured are discussed.

Kiminori Araiba, Naoki Sakai

Experimental Research of Risk Parameters in the Process of Bedding Rock Landslide Motion

Bedding rock landslide is a common slope failure. The intensity of landslide is closely related to rock structure and terrain. It is important to assess landslide risk based on the geological structure. Firstly, the geological structure model of landside was set up based on the affecting factors pertinent to the analysis of landslide motion. Then, a physical experimental set up was built to measure the kinematics parameters of bedding rock landslide with different geological structures. Lastly, intensity parameters of bedding rock landslides were proposed by applying test data based on risk theories. It indicates that: (1) bedding rock landslide can be divided into three structures, i.e. similar granular, layer and blocky structure. Layer structure could be divided into three subcategory considering terrain, rock structure and slip surface; (2) Three dynamic parameters of final velocity on active-slide segment(

v

t

), accumulation range (L1) and impact strength (φ1) are sorted as follows: layer rock (α) > blocky rock (χ) > similar granular rock (ϕ); (3) The blocky rock (χ) has the largest of accumulation range L1, but the multilayer rock (α) has the largest of impact strength φ1. (4) The intensities within sliding mass are sorted as follows: blocky rock (χ and δ) > multilayer rock (α and β) > granular landslide (ϕ) > single layer rock (I). Intensities in the beginning of landslide deposit area are (α, β and δ) >χ>I>ϕ; Intensities on the top edge of deposit area are α>δ>χ>β>I.

Bo Chai, Huanying Pan, Xiang Li

Calculation of Permeability of Clay Mineral in Natural Slope by Using Numerical Analysis

A natural landslide is mainly occurred by rainfall, snowmelt, earthquakes and construction works. Especially, the role of rainfall or snowmelt in slope stability is very important because it causes a decrease in shear strength by reducing the soil cohesion. If clay exists in the weathered soil, the physical characteristics such as viscosity and permeability are generally different from the condition without the clay. In this case, changes of permeability or viscosity due to the rainfall or snowmelt are dependent on the content of clay in soil. In order to calculate the variation in permeability according to the content of clay in soil, many researchers have conducted laboratory experiments or in-situ tests in the field. However, it is difficult to determine the property of the clay such as a viscosity because of its poor crystalline property. In order to solve this problem and to calculate permeability of clay under various dry densities, we used molecular dynamic (MD) simulation to examine the viscosity of micro scale and homogenization analysis (HA) method to expand micro material property to macro scale. In this research, we determined the permeability of clay with various dry densities due to the rainfall or snowmelt conditions by using MD/HA method.

Junghae Choi, Byung-gon Chae, Katsuyuki Kawamura, Yasuaki Ichikawa

Study on the Microscopic Structure Characteristics of the Gray Matter Slate

The changes of the stress state and strength of the slip zone in a landslide are determined by the material composition, micro-structural feature, and formation mechanism of the slip zone. It affects the activities of the landslide. In this paper, the mineral composition of the slip zone, which is composed of soft rock of the gray matter slate, is identified by DMAX-3C X-ray diffractometer, polarizing microscope, and scanning electron microscope (SEM). Results show that the content of calcite reaches up to 68 %. There are no changes in the slickensides composition of the sliding surface material. The microscopic structure has been analyzed by different experiments. The results show that the weak zone is composed of the banded calcareous tuffaceous slate, and its structure is characterized by gray black striped fine grains, heterogranular and irregular, and cryptocrystal texture. There is clay on these surfaces, and can be cut into pieces, so it is easy to track and accommodate the shear failure surfaces.

Maolin Deng, Qiang Xu, Xing Zhu, Guojun Cai, Guang Zheng

Effect of Vertical Load on Shear Characteristics of Micro-Piles in Landslide

In recent years, micro-pile has been widely applied to landslide treatment engineering due to its advantages in application and construction. Its engineering effect is quite evident. At present, some researchers focus on studying the effects and failure mode of micro-pile in landslide reinforcement. However, only few of them discussed how the pile works with shearing force and vertical load. By numerical simulations, a part of which were compared with the results from large-scale physical model tests, effects of vertical load on shear characteristics of micro-piles in landslide were analyzed. Each row of piles simultaneously sheared with vertical loads, which played an active role in increasing anti-sliding force. According to the analysis, the four rows of piles, installed close to trailing edge, were mainly affected by compression, comparing to the rows installed in front, which are affected with tension.

ShuFeng Wang, YuePing Yin

Geotechnical Centrifuge Modelling for Rock Slope Failure: A Brief Overview

Geotechnical centrifuges are used widely worldwide for rock mechanics. This paper gives a brief overview of rock slope failure modeling using geotechnical centrifuges. Several cases involving centrifuge modeling for rockslide mechanisms have been recorded. Two methods of small-scale geotechnical centrifuge modeling for large scale problems, such as landslide form massive rock slope failure, are presented. Furthermore, model materials for structures are introduced considering the structures dominating rock slope stability. Finally, a short discussion regarding difficulties in rock slope failure modeling is given.

Zhen Feng, Yueping Yin

Physical Model of the Mechanism for Thermal Wedging Failure in Rocks

Cyclic diurnal and annual temperature variations acting upon rocks are rarely considered among triggers of slope movements. The importance of temperature change is viewed mainly as a precursor of failures, where the triggers are rainfall or seismic activity. This paper aims to determine the limit conditions in which plastic deformation develops in a situation where one or more blocks fallen into an open crack create a wedge, causing non-elastic displacement of a block resting on an inclined plane. A physical model was prepared to study this phenomenon in a thermal dilatometer, in which the displacements were measured using linear variable differential transformer (LVDT) sensors for blocks with different block/wedge ratios, while temperature was varied in a controlled manner. Nine physical models of sandstone blocks were tested over a cyclic temperature change of ΔT = 35 °C while measuring the permanent displacements of a block in order to confirm the existence of this type of failure mechanism. Further, a series of cyclic tests were performed on all nine physical models to determine the threshold temperature change at which plastic deformation occurs for different block/wedge ratios. Results showed plastic deformation resulting from a cyclic wedging mechanism for a block/wedge ratio 0.5 and total model size of 50 mm, reaching a permanent displacement of 4.23 × 10

−3

mm for a block resting on an inclined plane with a slope of 7°. For these conditions, a temperature change which caused permanent block displacement by thermal wedging was as low as 6 °C. The results of the physical model are in agreement with a proposed analytical solution by Pasten (2013) and measurements of Bakun-Mazor et al. (2013) at a site at Masada, Israel.

Vladimir Greif, Ivana Simkova, Jan Vlcko

Shallow Modes of Slope Failure in Road Earth Cuttings in Sri Lanka

Road associated failures in Sri Lankan landslides that have been investigated to date were highly dependent on geological setting of the cut slope. Numbers of cut slopes and their failure modes were studied in order to understand the influence of factors: slope height and angle, bed rock geology, seepage, overburden geology and geometry of the cut slope on the slope failure. Shallow failure mode (height of failed mass less than 4 m) is a very common feature in these cut slopes when exposed to intense rainfall due to extensive saturation. Slope stability can be evaluated with the use of geometry, shear strength characteristics and geological setting. Importance of geological setting and characteristics of failure modes must be considered when designing structural measures to improve the stability. An understanding of combined effect of geomorphology and overburden geology, which sets stability of a road cutting, is an essential parameter and helps in understanding sliding potential of the immediate upper slope. This study emphasises importance of geological setting, which determines the characteristics of failure modes when designing structural measures to improve the stability. Combined effect of geomorphology and overburden geology, which sets stability of a road cutting, is an essential parameter for designing of remedial measures by reducing sliding potential of the immediate upper slope.

H. M. Janaki M. K. Herath, Sudheera S. I. Kodagoda, A. A. Virajh Dias

Discussion on the Method of Intact Loess Humidification Considering Water Content Uniformity

Soil mass strength has a direct correlation with soil mass water content. The shearing test for soil under different water contents is the most important method of analyzing landslide (sliding belt) soil mass strength. According to the humidification requirements on the intact loess for indoor test, we should pay attention to the uniformity of humidification for the intact loess. Through comparative studies on three humidification methods, it is considered that when the same loess samples have reached the same preset humidity, the loess sample with the pre-wetting method for 24 h can reach the uniform water distribution; the loess sample using the burying method can reach to the uniform water distribution after 10 days and the loess sample using the steaming method can reach the uniform water distribution after 8 h. The burying method can get the large water content range for humidification and saturated loess samples can be obtained through humidification, whereas the saturated loess samples cannot be obtained through the pre-wetting and steaming method.

Kai He, Bin Li

Undrained Shear-Strength Variation of Salt-Rich Clay: Implications for Fast-Moving Clay Landslides

It is well recognized that the shear strength of salt-rich clay is reduced after leaching and under drained conditions, as commonly occurs in reactivated landslides or in slow-moving landslides of such clay. This is due to loss of the physical and/or chemical bonds provided by the salt, demonstrating the physic-chemical effect of pore water on the shear strength of the clay. However, is there a similar effect when such clay is subjected to undrained conditions after leaching, as in fast-moving landslides in the clay following rainstorms or irrigation? To gain better understanding of the mechanisms of fast-moving landslides of salt-rich clay, the shear strength of a salt-rich clay under undrained conditions was investigated after being leached repeatedly. The clay was weathered mudstone from Heifangtai, Gansu, China. Test results showed that the clay’s undrained shear strength was remarkably reduced after leaching, mainly through water-soil physical-chemical interactions. The effective friction angle and cohesion of the clay may be reduced due to loss of the bonding salts, similar to the variation of its strength parameter under drained conditions. In addition, higher pore water pressure could build up during shearing due to an increase in the clay fraction caused by disaggregation of silt-size particles, leading to a decrease in effective normal stress and then shear strength.

Lei He, Bao-ping Wen, Xiu-juan Xu

Analysis of Engineering Geological Properties of Sliding-Zone Soil in Large-Scale Landslides in the Weibei Loess Tableland Area

Hipparion laterite exists extensively below the thick loess units on the northern bank of the Weihe River in Shaanxi, and its engineering geological properties control the occurrence of landslide hazards. Through hipparion laterite tests, this study shows the following: (1) the clay content of hipparion laterite is high including expansive clay minerals, such as ascanite or illite-smectite. The specific surface area values are as high as 262.9 m

2

/g. This property is due to the expansive clay, and this indicates that the material is physically and chemically active; (2) the hipparion laterite is characterized by micro-fissures, poor cementation, and disintegration. Its natural gumbo-like state changes to a plastic or soft plastic state when saturated and exhibits significant expansibility; (3) the natural intensity of hipparion laterite is relatively high. Its cohesion and internal friction angle are greatly reduced when saturated, and reduction from peak to residual shear strength is 47–63 %. Therefore, for a slope structure of thick loess, hipparion laterite, and bedrock, the strength of hipparion laterite greatly decreases under the effect of underground water. It then becomes a weak layer in high and steep slopes, forming shear zones that control the development and distribution of landslides in the Weibei loess tableland area.

Bin Li, Shuren Wu, Jusong Shi, Zhen Feng

Dynamic Centrifuge Modelling Tests for Sliding Rock Slopes

Sliding rock slope models with intermittent rock planes and secondary rock joints are built of synthetic material, and tested in a centrifuge testing system to study the failure process of rock slopes during an earthquake. The models are made of synthetic material containing gypsum, sand and pure water with certain mix ratio through strictly controlled casting procedure. New methods are invented to build the bedding planes with full contact and no gaps; special casting method is invented to add unbroken bedding plane parts inside each bedding plane. The results of the dynamic centrifuge tests reveal that the secondary rock joints inside the rock slope serve to weaken the dynamic stability of the sliding rock slope significantly, and could affect the dynamic failure mechanism of the slopes, making the rock layers collapse into smaller rock masses during sliding along the bedding planes.

Xianglong Li, Joseph Wartman, Huiming Tang, Jinkai Yan, Hongming Luo, Wei Hu

Changes in Shear Strain and Subsurface Flow Prior to Rainfall-Induced Landslide in Flume Experiments

Two shallow landslides were induced in a large-scale model slope by artificial heavy rainfall, in which the heights of sand layers were set at 0.7 and 0.5 m. A total of 2,931 s of rainfall produced a relatively large landslide in a whole steep slope section in the 0.5 m high sand layer. On the contrary, only a small landslide was produced by a total of 4,000 s of rainfall in the lower half of a steep slope section in a sand layer that was 0.7 m high. Changes in shear deformation and subsurface flow were monitored in the experiments. By tracing the movements of markers imbedded inside the sand layers, the changes in shear strain were analysed and expressed in a form of Mohr’s circle. In addition, by approximating the equi-potential lines from the observed data of pore-water pressure, the changes in subsurface flow directions were calculated. It has been shown that, although the sand layers were packed to be uniform, the observed shear deformation and subsurface flow conditions were not homogeneous; just before the landslide initiation, water tables were formed in almost all slope sections, but a sliding surface was not necessarily formed below the water table. Directions of maximum shear strain and subsurface flow were more in general agreement with the direction of slope base in the parts inside the landslide, indicating their possible influence on the landslide initiation.

Yasuhiko Okada

Geotechnical Properties of Landslide Sites in Korea with Differing Geology

The goal of this study is to find out the relationship between geotechnical properties and landslide occurrence in areas with differing geology in Korea. The soil properties were measured in three study areas (Jangheung, Sangju and Pohang) which are underlain by gneiss, granite and sedimentary rock, respectively. Many landslides occurred in these areas during the rainy season. To investigate the factors that influence the landslides, a landslide survey was made, and a series of laboratory soil tests were carried out. The results of soil tests show that the average porosity of the soils originated from the gneiss of Jangheung and the granite of Sangju is greater than that of soils originated from the sedimentary rocks of Pohang. The average coefficient of permeability of the soils originating from the granite of Sangju is higher than that of soils from the gneiss of Jangheung and the sedimentary rocks of Pohang. The average coefficient of permeability of soils obtained from the landslide sites is greater than that of soils obtained from landslide-free sites in the same geology. The average shear strengths of soils obtained from the landslide sites are smaller than those of soils obtained from the landslide-free sites. It is confirmed that soils with low shear strength and high permeability are especially vulnerable to landslide occurrence.

Young-Suk Song, Kyeong-Su Kim

Modelling Fragmentation in Rock Avalanches

The physical description of rock masses travelling down a slope is a complex problem, involving bouncing, rolling, sliding, flowing, fracturing and/or combinations of these. Modelling serves as a valuable tool to study these systems which are rarely monitored at high resolution in nature. Often, granular models (e.g. loose sand) are used to study rock avalanches in experimental simulations. For such granular models, one has to assume that the rock mass disintegrates instantaneously after detachment and that fragment size does not reduce further during the movement. We present a new method that overcomes this limitation by simulating dynamically fragmenting gravitational mass movements.

We have developed a material that fails in a brittle manner at lab scale conditions. The material is produced by cementing sand with gypsum (anhydrite) or potato starch, which allows controlling the shear strength over a wide range. Experiments are performed by releasing the material down a slope and monitoring with a digital camera at frequencies of 50 or 250 Hz. Two techniques are used to quantify the experimental results: particle image velocimetry which quantifies the surface velocity field, and optical image analysis to derive geometric (e.g. fragment size distribution) and mechanical properties (e.g. basal friction) of the model.

Preliminary results from the experiments illustrate the different dynamics of the gravitational mass movement as a function of shear strength.

Øystein Thordén Haug, Matthias Rosenau, Karen Leever, Onno Oncken

Experimental Modelling for the Effect of Rainfall and Earthquake on Slope Stability of Engineered Fill

The collapse of several houses in some residential developments in Sendai during the M9 Tohoku earthquake warranted the health monitoring of several slopes in southern California. Majority of the houses developed in southern California are in engineered fill and the qualities of compaction may not be sufficiently checked. Due to recent trend of unpredictable rainfall and being located in the high seismic activity area, houses constructed on slopes in southern CA have strong potential to slide during earthquake or heavy rainfall. This study involves a systematic study of an engineered fill at Mission Viejo, California for potential slide activities. The materials borrowed from the site were compacted in a Plexiglass container at the field density, moisture content, and field slope angle. The slope was poured with the 100 year return period rainfall expected in the area using, a rain simulator. Variation in suction in the soil mass was recorded with duration of rainfall. Slope stability analyses were performed to evaluate the effect of earthquake in those slopes in reducing the factor of safety. The study result shows that the combined effect of antecedent rainfall and seismic shaking has significantly high effect on slope stability, compared to strong magnitudes of either rainfall or seismic acceleration acting separately.

Binod Tiwari, Santiago Caballero, Wissam Zalzali

Experimental Modelling of Seepage in a Sandy Slope

Rainfall-induced shallow landslides cause significant damage to infrastructure every year. Among the major causes of shallow landslides is an increase in degree of saturation with rainfall. Partially saturated slopes have high factors of safety due to the apparent cohesion induced by soil suction. In this study, sandy soil was used to prepare slopes with four different angles of inclination and two different void ratios. Utilizing a rain simulator, the slopes were provided with different intensities and durations of rainfall, ranging from 30 mm/h to 240 mm/h. The movement of the water front was recorded during the rainfall at an interval of 5 min. The experimentally recorded values for the depth of water front with time was used to develop relationships between the velocity of seepage, void ratio and angle of inclination of the sandy slope. The proposed equations can be utilized to evaluate the stability of sandy slopes during rainfall.

Binod Tiwari, Adam Lewis

Curvature of Failure Envelopes for Normally Consolidated Clays

Shear strength parameters play an important role in the stability of slopes. Accuracy of the analysis result depends on the nature of the failure envelopes used, especially in the case of shallow landslides, where the shear strength is mobilized at low effective vertical stresses (

σ

n

′). Ten normally consolidated samples prepared from mixtures of montmorillonite, kaolinite and quartz were sheared in a constant volume simple shear device at the normal stresses ranging from 25 to 800 kPa. From the results, it was noted that correlations for undrained shear strength should be selected with respect to the anticipated failure mechanism. The power function can be used to represent the curvature in failure envelopes. Direct shear results suggests a lack of curvature in the effective failure envelopes for normally consolidated clays. However, results from the simple shear testing show that failure envelopes are curved for low effective normal stresses and thus, the use of a linear c′−ϕ′ envelope can be unconservative for shallow landslides.

Binod Tiwari, Beena Ajmera

Experimental and Numerical Studies on the Effect of Rainfall on Triggering Shallow Landslides

Rainfall is considered one of the major triggering factors for shallow landslides. The effect of rainfall in causing landslides depends on the intensity and duration of rainfall, the type of soil, the inclination of the slope, and ground water conditions. The majority of slope stability problems in shallow slides involve partially saturated soils. Although experimental modelling of slopes subjected to various intensities and durations of rainfall are ideal to evaluate the effect of rainfall on slope stability, it is time consuming and expensive. Numerical simulation of such experimental modelling can save a great deal of time and cost. In this study, slope models were prepared at angles of inclination of 30° and 45° with double washed construction sand, at a void ratio of 0.7. The slopes were subjected to 30 mm/h of rainfall for 3 h. Spatial variation of suction during the rainfall and depth of water front with time were measured for the entire rainfall period. The depth of water front and spatial variation of suction were also calculated through the finite element model (FEM) that was developed based on a hydro-mechanical model developed for the partially saturated soil. The numerical and experimental results provided identical results. The numerical result was extended to predict the spatial variation of suction, depth of water front and deformation of slope subjected to higher intensity of rainfall.

Binod Tiwari, Katsuyuki Kawai, Adam Lewis, Phommachanh Viradeth

Feasibility Analysis of Loess Slope Improved by Lime Pile

Lime has powerful characteristics of hygroscopicity, expansibility and gelation with soil, so a slope can be strengthened by placement of lime piles. In this paper, experiments have been performed to investigate the diffusion characteristic of lime in loess, and the influence of lime to the physical and mechanical properties of loess also have been examined, in order to verify the feasibility of using pile to improve the stability of slope. The results show that it is feasible to improve stability of slope by lime piles. Pile spacing should be set about 8.5 times as many as the diameter of the pile when the pile holes arranged according to the plum flower form from this test. Moreover, lime piles strengthen the loess slope mainly by gathering and cementing the clay grains in loess.

Wanjiong Wu, Shouyun Liang, Fanyu Zhang, Xude Yan, Jianji Zhou

Effect of Soaking on Shear Strength of Weathered Argillaceous Rocks Susceptible to Landsliding in the Three Gorges Area of China

Slope stability in the Three Gorges reservoir has been one of the greatest concerns for both researchers and officials in China since inundation of the Three Gorges reservoir area. Shear-strength reduction of the inundated slope materials may be one of the major causes leading to slope failures. In this study, the shear strength of three kinds of weathered argillaceous rocks that are most susceptible to landsliding was experimentally investigated after soaking the material for different periods. It was found that reduction in shear strength of all the three weathered argillaceous rocks and their strength parameters occurred significantly after soaking for about 35 days, and that a very minor reduction was observed after soaking for a longer period. The weathered argillaceous rocks with more particles coarser than silt showed a greater reduction in internal friction angle, while those with more clay and silt displayed a greater decrease in cohesion. Particle analysis of the weathered argillaceous rocks after soaking, the compositions of their clay minerals and chemical analysis of the soak water suggested that shear strength reduction of the weathered argillaceous rocks may be attributed to a combination of slaking of rock fragments coarser than silt, hydration of clay minerals, and dissolution of calcite, as well as hydrolysis of feldspar due to soaking.

Baoping Wen, Hui Li, Kaihao Ke

Creep Behavior of the Slip Zone of a Giant Slow-Moving Landslide in Northwest China: The Suoertou Landslide as an Example

The Suoertou landslide, a giant landslide with a volume of 72.85 × 10

6

m

3

in Zhouqu County, Gansu province of China, has been reactivated with a rate ranging from 300 to 600 mm/year since 1990s. The slow-moving dynamic nature indicates that the creep nature of its slip zone may play one of the predominant roles in the reactivation of the landslide. To clarify this, creep behavior of the saturated soil collected from the landslide’s slip zone was investigated via a series of direct shear creep tests. It was found that the creep behavior of the landslide’s slip soil was strongly dependent on the stress-level for both normal and shear stresses. It was also found that the accelerated creep stage could not be reached until the shear stress exceeded 125, 187.5 and 300 kPa and the initial strain rate at 3.141, 3.688 and 4.5 min

−1

, under the normal stresses of 100, 200 and 400 kPa, respectively. Moreover, both the critical shear stresses and the initial stain rates at which the accelerated creep stage begins seem to have a linear correlation with the normal stress.

Xiu-zi Jiang, Bao-ping Wen

Data Collection and Processing for Measurement of Time-Variable Gravity Erosion in the Laboratory Study

Researchers face great difficulties that few measurable data of gravity erosion on the Loess Plateau are found due to a lack in observation techniques. A problem common to all of the existing methods is that the data were observed after the failure events, and the gravity erosion was not separated from other forms of erosion. This study presents a novel experimental technique and a reliable data processing method that quantitatively measures the time-variable gravity erosion on the steep loess slope in the laboratory test. A structure with laser based gauge and the Topography Meter was designed and fabricated to monitor the dynamic variation of the steep slope topography under rainfall simulation. As the slope landform deforms over time, the process will be recorded in the video, and then imported into the computer to acquire a snapshot image at particular time instance. Given depth in ArcGIS, the 3D geometric shape of the target surface can be computed accurately. All erosion data in every rainfall event, including the amount of each failure mass, the total amount of soil loss, the total amount of hydraulic erosion, etc., could be calculated according to the videos caught by the Topography Meter. It is recommended to make 3D surface together with R2V and ArcGIS, although ArcGIS is sufficient for 3D surface modelling, because contour tracing in R2V is implemented on the undistorted original image, and R2V is also in much smaller size and easy to operate.

Xiang-Zhou Xu, Song Zhan, Qiao Yan, Ming-Dong Zhu

Study on the Effect of Plant Roots for Stability of Slopes

There have been several studies on the properties of plants, which are beneficial to critical slopes in preventing failures. However, the impacts of the tensile properties of the plant roots have to be studied in detail. In this study, three different situations were addressed: completely dry, saturated and unsaturated. Under these three situations, stability of different slopes with different soil conditions was studied. Some roots were tested through the tensile testing machine normally used for yarn testing and some were tested with the traditional tensometer. Variation of root diameter was established by measuring the roots of tea plants available at cut slopes. Literature was found on the variation of tensile strength of tea roots with its diameter. Slopes of the tea estates were modeled considering the number of tea plants available in a particular slope. This was later converted to a percentage cover and values of factor of safety (FOS) were compared by changing different soil properties with the percentage of cover. It was found that the FOS tends to increase with the percentage cover under completely dry, saturated and unsaturated situations. However, it was learnt that the impact of tensile capacity of roots had not been so high under dry and saturated cases for cohesionless soils compared to the same situation under unsaturated condition which had high FOS values due to the plant properties.

Udeni P. Nawagamuwa, S. Sarangan, B. Janagan, S. Neerajapriya

The Dynamic Process and Sensitivity Analysis for Debris Flow

The dynamic process and sensitivity in the debris transportation process are important topics in the study of rapid landslides and debris flows. The motion process of debris flow is recognised as a dynamic interaction between the original moving material and the entrained basal topsoil shearing along their non-slip contact surface. In this paper, we employed numerical modelling to clarify the erosional effects, and use statistical method to compare the influence degree of rheological parameters on the runout behavior. The simulated results show that unconfined flows typically exhibit a wide range of entrainment and deposition volume, whereas confined flows yield moderate volumes of entrainment and small volumes of deposition. The basal topography is an important factor in influencing the debris transportation and deposition processes. The velocity, runout distance, and deposition area and volume are more sensitive to underlying surface conditions, particles of debris, pore water pressure; and can affect the debris intensity, disaster area and scale to a large extent. Conversely, the velocity, runout distance, and deposition area and volume, are less sensitive to the source volume of debris flows, and can only affect the velocity to a little extent. The proposed suggestions can be utilized conveniently in general geotechnical engineering practices.

Guoqiang Yu, Maosheng Zhang, Hong Chen

Evaluation of Sensitivity of the WAA and SINMAP Models (Static) for Landslide Susceptibility Risk Mapping in Sri Lanka

Shallow landslides are one of the most common types of failures occurring frequently in steep slopes, overburden soil and landscapes in different climatic zones. The effect of topography, slope angle, slope drainage, vicinity of road and infrastructure, overburden soil depth and geology are important factors for the interpretation of the recurrence of shallow landslides. Data, although insufficient in number, has stimulated the debate about the effect of geology and topography on the susceptibility of shallow landsliding. An Analytical Hierarchical Process is applied in order to derive the weights associated with attribute map layers. Based on these weights, GIS datasets are combined by weighted Average Analysis (WAA) and the landslide susceptibility map of the study area is created. The resulting information was compared with the landslide susceptibility map derived through the Stability Index Mapping (SINMAP) model. Both outputs are useful for a better understanding of landslide susceptibility and their origins and prioritization of efforts for the reduction and mitigation of future landslide hazards. Sensitivity of both approaches was fine tuned with the overburden soil strength parameters, geomorphological evidences and field verification techniques.

A. A. Virajh Dias, A. A. J. K. Gunathilake

The Method for In-situ Large Scale Shear Test of Saturated Soils and Its Application

Due to inherent uncertainties associated with laboratory testing, such as sampling disturbance and size effect, and the limitation that conventional in-situ large scale shear tests are generally carried out for soil masses of natural water content, soil mass strength parameters determined by back analysis instead of testing are, mostly, used for geotechnical stability analyses and engineering designs. In this study, based on conventional in-situ large scale shear test apparatus, two modes of apparatus, the vertical soaking mode and the lateral soaking mode, were developed to accommodate testing techniques for saturated soil. With the apparatus, seven in-situ large scale shear tests were carried out on saturated loess masses in Heifangtai, Gansu province. The results show that the loess masses could be saturated by both modes. Compared with the lateral soaking technique, vertical soaking often causes more sample disturbance, even failure, although it takes less time to saturate. Compared with parameters from in-situ large scale shear tests of the loess masses with natural water content, cohesion from in-situ large scale shear tests of the saturated loess masses decreased sharply from 44.65 to 17.35 kPa, while internal friction angle decreased marginally from 14.18° to 11.95°. Compared with parameters obtained through consolidated quick direct shear tests on the saturated loess, the increments of cohesion and the internal friction angle from in-situ large scale shear tests of the saturated loess masses were about 4 kPa and 3° respectively. To improve the method, it is necessary to carry out comparative tests in order to improve the uniformity of water distribution and degree of saturation, as well as select more pervious materials.

Maosheng Zhang, Wei Hu, Lifeng Zhu, Ying Pei, Junbo Bi

Microstructural Characteristics of Qinyu Landslide Slip Soil, NW China

Slip zones are closely related to landslides. The microstructural analysis of slip soil has become one of the important contents on landslide researches. Based on two slip zone profiles of Qinyu landslide, the microstructural characteristics of slip soil and its geological implications were studied by the means of scanning electron microscope (SEM). The results showed that: (1) the microstructures of slip soil are mainly characterized by flocculated-clotted texture, fine and meso-pores; (2) on the slip zone profile in front of the main landslide, the closer to the centre of the slip zone, the greater amount of pores, the narrower and longer shape of pores, as well as the smaller apparent porosity and probability entropy of pores become. Obviously, the amount of pores is negatively related to apparent porosity, while probabilistic entropy is positively related to the shape factor; (3) on the slip zone profile in the upstream side of the secondary landslide, the amount and apparent porosity of pores are smaller as a whole. In addition, higher orientation, especially, near the upper slip surface in the profile has revealed the microscopic mechanism that Qinyu landslide is relative stable on the whole, while the secondary landslide was in a constant active state.

Xuemei Jia, Shouyun Liang, Chenyi Fan

An In-situ Darcy Method for Measuring Soil Permeability of Shallow Vadose Zone

This paper presents an in-situ Darcy test for measuring permeability of soil in shallow vadose zone. The equipments of the test was designed based on the theory of classic

Darcy Test

comprising water infiltration system, water supply system and measuring system. During the experiment, the soil was submerged by water with constant head maintained by a Marriott tube. Volume of water consumed and the corresponding water head in a time series were recorded when the soil was saturated. Then soil permeability was obtained using the Darcy’s law. Three groups of the in-situ Darcy tests were conducted at the loess plateau in north western China, and average values of permeability were obtained to range from 0.84 to 2.22 m/d. It is shown that the original structures of soil can be well considered with the in-situ test compared to the classic in-door

Darcy Test

. Furthermore, the data record was more intuitive and the operations are easier compared to the other in-situ tests to measure the soil permeability.

Pingping Sun, Maosheng Zhang, Lifeng Zhu, Ying Pei, Xiujuan Cheng

Discussion on Assessment in the Collapse of Loess: A Case Study of the Heifangtai Terrace, Gansu, China

Collapsibility is a unique feature of loess. Besides foundation deformation and subsurface erosion, slope failures can also be resulted from the collapse of loess. Based on analysis of the collapse of loess at the Heifangtai terrace, Gansu, China, a notable difference between the theoretically calculated and actual values of collapse were observed. The theoretical value was less than 50 % of the actual one. Based on this difference, the assessment of the collapse of loess, including definition of collapsible loess and calculation of the collapse are discussed. It is found that collapsible loess is a kind of typical unsaturated soil. Therefore, water content and types of structures were essential factors affecting the collapsibility of loess. Assessment of the collapse of loess, from

why collapse

to

how collapse

, can be achieved by applying parameters representing both water content and types of structure, using the theory of unsaturated soil mechanics.

Pingping Sun, Maosheng Zhang, Lifeng Zhu, Qiang Xue, Wei Hu

Quantitative Deformation Analysis of Landslides Based on Multi-period DEM Data

Quantitative deformation analysis of landslides is a difficult problem in landslide study. The quantitative deformation analysis model of landslide based on multi-period DEM data is established by ArcGIS using four periods of topographic maps obtained in 1977, 1997, 2001, and 2010, in order to reveal the processes of landslide evolution in the Heifangtai Irrigation Area. The deformation amount and deformation rate were calculated in stages for 32 landslides along the margins of Heifangtai platform in Yongjing, Gansu Province. The mean retrograde eroding velocity of landslide scarp was 4.47 m/a from 1977 to 1997, 3.46 m/a from 1997 to 2001, and 1.10 m/a from 2001 to 2010. At the same time, the relational formula between irrigation amount and landslide deformation amount was established, and the landslide evolution tendencies were predicted. The calculation results show that the average retrograde distance of the landslide scarps will be 0.79 m by 2015 and can be reduced to 0.20 m by 2020.

Qiang Xue, Maosheng Zhang, Lifeng Zhu, Xiujuan Cheng, Ying Pei, Junbo Bi

Research on Prediction Methods of Surges Induced by Landslides in the Three Gorges Reservoir Area of the Yellow River

The risks of surges in the Three Gorges Reservoir area of the Yellow River cannot be neglected. Empirical equations are efficient evaluation methods which should be considered as a priority. Field survey was carried out on the loess landslide and surge which occurred in Jiaojiayatou in the Three Gorges Reservoir area of the Yellow River on 7th February, 2012. Then features of the loess landslide and surge were analyzed. Nine classical equations for landslide-triggered surges were adopted to calculate characteristic parameters of the surge, including initial surge height and run-up height on the opposite bank. Compared with field survey results, characteristic parameters of the surge derived by empirical equations, including ASCE recommended method, method of China Institute of Water Resources and Hydropower Research, Huber and Hager model and Panjiazheng method, are close to those of the real model. The verification coefficients are 2.14, 1.92, 0.6 and 0.66 respectively. After comprehensive comparisons of safety and economical efficiency, Panjiazheng method is recommended to predict similar hazards in the Three Gorges Reservoir area of the Yellow River.

Wei Hu, Maosheng Zhang, Lifeng Zhu, Pingping Sun, Xiujuan Cheng, Jun Jia

Analyses of the Changes of Loess Engineering Properties Induced by Irrigation

Irrigation has changed the original environment of loess. In the process of moistening and saturating after irrigation, engineering properties of loess such as microstructure, physical properties, mechanical properties and water-physical properties have been changed, which become important conditions inducing loss due to geo-hazards. Taking Heifangtai of Gansu province as a studied irrigation area, systematic studies were carried out on loess ranging from in-situ tests to laboratory tests, from traditional soil mechanics to mechanics for unsaturated soils, from microstructures to macro properties. Based on the study, the changes of engineering properties of loess due to irrigation were revealed. The results show that irrigation destroys the primary structures of loess with general decrease of the total amount of voids, as well as disappearance of overhead voids. Due to irrigation, natural water content, in-situ density and dry density all increase while natural void ratio decreases. Collapsibility of loess decreases. The shear strength decreases dramatically. In terms of soil mechanics for unsaturated soils, irrigation causes the increase of water content of loess and decrease of matric suction. As a result, the strength parameters for unsaturated loess show decreasing trends.

Wei Hu, Lifeng Zhu, Maosheng Zhang, Ying Pei, Junbo Bi

Deformation Behavior of Mechanically Stabilized Earth Walls with Geocomposite Drainage Under Seepage Condition

Both external and internal stabilities are main concerns in design and construction manuals for the mechanically stabilized earth (MSE) wall. Literature showed that the failure of the MSE walls, especially in mountainous areas, is mainly caused by the attack of seasonal heavy rainfall. The seepage through the MSE wall due to the rainfall causes the increase in the lateral stress and the reduction in the effective stress, stiffness and strength of the backfill; hence the reduction in the factors of safety against external and internal failure. This paper investigates the flow and mechanical behaviors of the MSE wall with and without geocomposite grain under seepage condition. The investigation is performed using laboratory physical model tests. It is found that the water pressure significantly controls the performance and the failure of the MSE wall. As the water pressure increases, the settlements in the unreinforced zone increase. The failure of the MSE wall is caused by the piping of the reinforced soil. The geocomposite drainage reduces the water pressure and water content in the reinforced zone, hence the improvement of the stability of the MSE wall. For the same water pressure, the MSE wall with geocomposite drainage sustains lower settlements.

Avirut Chinkulkijniwat, Somjai Yubonchit

Loess Landslides Respond to Groundwater Level Change in Heifangtai, Gansu Province

Change in the ground water level induced by irrigation is a vital factor to geological hazards in Heifangtai areas. Based on the loess water system affecting the stabilities of slopes the most, the evolutionary process of groundwater system induced by irrigation is analyzed, and the relationship of the evolutionary process with occurrence frequency and volume of loess landslides are analyzed comparatively. It indicates that four times sliding have happened since people started irrigation in this area. It shows that groundwater level will continuously go up if present irrigation volume is maintained. Loess landslides may move repeatedly because the volume of shearing-tension plasticity areas enlarges significantly. For this reason controlling the groundwater level can be a significant measure to protect slopes from moving.

Ying Dong, MaoSheng Zhang, Jie Liu, Pingping Sun, Jun Jia

Application of Numerical Modeling Techniques to Landslides

Frontmatter

Introduction: Application of Numerical Modelling Techniques to Landslides

Numerical modelling techniques can be used in conjunction with detailed site investigation and slope monitoring to gain a better understanding of the factors controlling the deformation or failure mechanism of a particular slope. A wide range of numerical modelling techniques are also available to assess the post-failure behaviour of mass movements. The numerical modelling techniques for the pre- or post-failure behaviour of a landslide can be based on empirical relationships, continuum mechanics, or discontinuum mechanics. These techniques have been calibrated based on numerous back-analysis of various mass movement types and can now be used as a numerical laboratory to evaluate the mechanical behaviour of landslide for a variety of scenarios.

Marc-André Brideau

Numerical Simulation on the Deformation and Failure of the Slope Treated by Building by Cave Dwellings

There are a large number of cave dwellings existing in the loess area. Building houses at the base of slope by the cave dwellings lead to the instability of numerous slopes, resulting the loss of large number of properties. Building houses by the cave dwellings is quite popular in the loess area, therefore, it is important to conduct stability analysis on this kind of slopes. This article focuses on a typical slope selected in North Shaanxi, the stress and strength variation trend on the critical slip surface for five scenarios such as the natural slope, artificial cut slope, cave dwellings constructed on the foot of the slope, building houses by the cave dwellings for short and long term are studied and the deformation failure mechanism of the slopes are investigated. The result shows that construction by cave dwellings increases the water content of loess, which changes the distribution of stress in the middle and the foot of the slope. And finally the failure of slope occur by the cave dwellings collapse when the sliding force at the bottom of the critical slip surface exceeds the shear resistance.

Chunli Chen, Kai He, Tonglu Li

Long-and Short-term Controls on the Spriana Rockslide (Central Alps, Italy)

Deep-seated rockslides in alpine valleys involve huge volumes and evolve over a long time under the action of multiple triggers. Scenario assessment and early warning systems based on monitoring activities are often the only effective ways to mitigate related risks, and require a sound understanding of complex interacting controls. We discuss the Spriana rockslide, affecting the left-hand flank of Val Malenco (Italian Central Alps). Documented rockslide activity dates back to 1912, with major acceleration stages in 1960 and 1977–1978 and later minor reactivations. The rockslide is a compound slide involving up to 50 Mm

3

of slope debris and fractured rock, with a basal failure zone up to 90 m deep and two main scarps. Rock mass characterisation based on laboratory and field analyses provided inputs to 2D Finite-Element modelling of long-term slope evolution. The results allowed re-evaluation of the mechanisms of the Spriana rockslide, accounting for both long-term controls related to valley deglaciation and the short-term complexity of groundwater response to rainfall inputs. We suggest that modelling long-term slope evolution may be required to correctly understand large rockslides in changing geomorphic systems.

Federico Agliardi, Giovanni B. Crosta

Engineering Geology and Numerical Modelling of a Steep Rock Slope for the Ensi-Qianjiang Expressway, China

This paper describes the site investigation and engineering geological characterization of steep engineered rock slopes at the site of a major 280 m single span arch bridge. The rock slopes comprised predominantly carbonaceous limestone with reduced rock mass quality due to the influence of faulting and shearing. The carbonaceous limestone occurs as lenticular bodies with smooth, tectonically disturbed, variably dipping (37°–57°) bedding planes. The rock slope was excavated to a total height of 90 m, including a bridge foundation excavation depth of 30 m and a final permanent engineered slope height of 60 m. The engineered rock slope was excavated at 60°–90° and the natural rock slope is between 50° and 70°. Construction of the bridge foundation required the excavation of three rock slopes, two perpendicular to bedding and one parallel to the strike of the bedding. In the two rock slopes excavated perpendicular to bedding, one exhibited potential bedding plane controlled failure and the other potential toppling instability. The intact rock properties were characterized using laboratory testing and selected discontinuities tested in direct shear. Using the derived properties and the results of the engineering geological mapping numerical modelling was undertaken using a discontinuum model, (UDEC). The deformation of the rock mass during the stages of excavation was simulated and the results used to develop plans for safe construction and reinforcement of the rock slopes.

Xiuwen Hu, Doug Stead, Longxiang Zhai, Hongyan Jin, Dezhi Kong

Determination of the Effective Computing Region for Rock Slope Stability Based on Seismic Wave Theory

In order to detect the initiation of a rockslide efficiently, FEM and BEM numerical methods are employed to analyze the dynamic response of a slope. The boundary condition (effective computing region) should be selected carefully to maximize both the computational efficiency and precision of the model. The effective computing region can be determined based on the tension damage criterion and the principle of dynamic responses. The seismic wave theory is employed to solve the dynamic response, detect the initialization of cracks and establish the critical sliding zone (comprising all potential sliding surfaces). The relationship between the location of the sliding surface and the excitation frequency, is also investigated. The focus of this study to identify the effective computing region and to discuss the sliding fracture that occurs in the region based on the seismic theory analysis. The shaking table model results and the time-history analysis of displacement vectors are adopted for investigating the reliability of theoretical analysis.

Chen Zhenlin, Hu Xiao

Factors Controlling Kinematic Behaviour of a Huge Slow-Moving Landslide in China

Xieliupo landslide, located in the Zhouqu County of northwest China and with volume of 72 × 10

6

m

3

, is a slow-moving landslide for more than 100 years. Several violent slide events have been recorded during its active history. However there has been an argument among professionals about mechanism of the landslide, particularly factors controlling its kinematic behaviour. A detailed investigation found that kinematic behaviour of the landslide may be affected by either an active fault with strike displacement rate of 1.4 mm/a, or river incision at its toe or a combination of those above, apart from its gravity and soft nature of its materials. To understand roles of these factors in slow-moving behaviour of the landslide, a numerical modelling was carried out. Results of the modelling show that gravity of the landslide and visco-plastic nature of its materials may play predominant roles in activity of the landslide followed by the active fault and river incision. The active fault accelerates the landslide velocity by 20–30 %, whereas the lateral incision by the river water may just locally intensify activity of the landslide, mainly in the zone behind the river bank 50–70 m.

Shu Jiang, Baoping Wen, Cheng Zhao, Ruidong Li

Finite Element Simulation for an Earthquake-Induced Catastrophic Landslide Considering Strain-Softening Characteristics of Sensitive Clays

In the present study, a strain-softening constitutive model for sensitive clays originating from weathered pumice is applied to simulate an earthquake-induced catastrophic landslide that occurred during the 2011 Great Tohoku and Kanto Earthquake in Japan. The upper part of the slope sliding about 200 m and 13 people were killed. The failure could be related to shear strength degradation of the sensitive clay layers in the slope during the earthquake.

The strain-softening characteristics of the sensitive material in the slope have been investigated in a series of laboratory tests involving undisturbed samples. The observed stress-displacement relationships under cyclic loading are numerically modelled using a proposed elasto-plastic constitutive model, based on the dynamic finite element method. The observed phenomena are appropriately simulated by the proposed model.

Akihiko Wakai, Fei Cai, Keizo Ugai, Tsutomu Soda

Numerical Modelling of Deformation for Partially Saturated Slopes Subjected to Rainfall

Rainfall is one among the most common contributing factor and trigger for landslides. In the majority of the cases, slopes are at partially saturated condition when they are subjected to rainfall. While analysing stability of those slopes, deformation analysis is performed in a conservative way assuming the slope to be in a fully saturated condition. In this research, a fully coupled hydro-mechanical finite element model is described based on the constitutive model developed for partially saturated soil condition. A 1.2 m long and 0.6 m high sandy slope was modelled in laboratory and was subjected to 30 mm/h of rainfall for 3 h. Values of suction measured after 3 h were very close to the numerically calculated values based on the finite element method developed by the authors. This model was used to calculate deformation of slope for different intensities of rainfall and at different angles of slopes in order to predict the amount of deformation or failure condition when a slope is subjected to a continuous rainfall of different intensities and durations.

Binod Tiwari, Katsuyuki Kawai, Phommachanh Viradeth

Feasibility Study of Dumping Area on Bearing Capacity and Slope Stability Analysis

Open pit mining, especially coal mining, needs cleaning and cutting of overburden. It needs an area for dumping overburden material. This area called disposal or dumping area. We need engineering geological mapping, analysis of bearing capacity, and slope stability analysis for preventing the failure of the dumping area. Therefore, this research aims to identify the best location of dumping area and the design of stable dumping area.

Methods that were used in this research are: (1) field engineering geological mapping, soil and rock sampling from either outcrops or three bore holes i.e.: GT01, GT02, and GT03; (2) laboratory analysis method for gaining information about UCS, angle of friction, cohesion, and unit weight, and (3) office method be in the form of analysis of engineering geological map, bearing capacity (Terzhagi’s Formula), and slope stability. Then the design of stable dump could be made according to the result of slope stability analysis.

The result shows that value of bearing capacity is different in each borehole. The location that suggested for dumping area is around boreholes GT03 (Engineering Geological Unit of Fine Soil II) because it has highest bearing capacity, among other boreholes, it is about 494.452 t/m

2

for continuous foundation. The simulation and analysis of slope stability show that safe design of dump is: single slope 25.6°, overall slope 15.5°, and maximum dump height is 50 m.

Twin Hosea W. Kristyanto, Iskandar, Dicky Muslim, Febri Hirnawan

Modelling Rockslide Displacements with Delayed Plasticity

To model the temporal evolution of complex landslides, a 1D pseudo-dynamic visco-plastic approach, based on Perzyna’s theory, has been modified. In the original version of the model, the viscous nucleus has been assumed to be bi-linear: where irreversible deformations develop uniquely for positive yield function values whereas, in a more general case, it can also develop for negative values. In this work the model has been enriched by considering: (1) an exponential viscous nucleus, (2) a strain-rate softening to reduce friction angle as the sliding velocity increases and (3) block interaction forces to cope with complex 3D geometries for the sliding mass.

The application of the proposed model to the Vajont slide emphasizes the role played by the strain-rate softening while the application to the La Saxe rockslide (Italy) clearly shows how a relatively simple model can be applied to a complex landslide by considering a spatial discretization of the sliding mass.

Gabriele Frigerio, Riccardo Castellanza, Giovanni Battista Crosta, Claudio di Prisco

Remote Sensing Techniques for Landslide Mapping and Monitoring

Frontmatter

Introduction: Remote Sensing Techniques for Landslide Mapping and Monitoring

Remote sensing is an effective tool for landslide mapping and monitoring. This chapter provides a general overview of the recent applications of optical and radar images for landslide detection, mapping and monitoring with special attention to SAR interferometry that has proved as a promising technique in landslide studies.

Veronica Tofani, Yang Hong, Vern Singhroy

Landslide Susceptibility Assessment Based on Remote Sensing and GIS in Lombok Island of Indonesia

In many cases, landslide that are causing severe disasters in populated downstream valleys occur in remote mountainous areas of Lombok Island. Those areas are difficult to access and to investigate by conventional ground-based mapping. Remote sensing contributes a way to collect data and information on remote and inaccessible terrain. Statistical approach using probability and weighting methodology has been applied to characterize landslide-prone ground. The methodology combines elements of techniques published by Greenbaum (Project summary report: rapid methods of landslide hazard mapping. Technical Report WC/95/30. International division. British Geological Survey. Key worth, Nottingham, UK, pp 12, 1995) and by Lee and Min (Environ Geol 40:1095–1113, 2001) allowing for increase of reliability of the landslide susceptibility map as the final product. Landslide inventory was supported through, and most of factors data have been derived through GIS processing and interpretation of satellite remote sensing data. Maps of factors weighted for significance in terms of landslide accountability and probability. The landslide susceptibility index (LSI) is the summation of each factors’ weight multiplied by the class value of each pixel, pixel by pixel. This produces an interim landslide susceptibility map as the preliminary result. Validation of the results in the field composes the final landslide susceptibility assessment of Lombok Island. The study area was classified into five categories of landslide susceptibility: very low, low, moderate, high and very high.

Arifianti Yukni, Teerarungsigul Suree, Cita Akbar, Kuehn Friedrich, Fuchs Michael

Application of Remote Sensing and GIS Techniques in Landslide Hazard Zonation of Hilly Terrain

Himalayan terrain comprise of rolling mountainous and steep topography. The deep gorges, bank less streams, sprawling catchment area, perennial snow and valley areas form the landscape in Himalayan region. It is well known that the occurrence of landslides is controlled by a lot of morphological, geological, and human factors. Prominent factors include steep slopes, underlying lithology, structure, geomorphology, land use, drainage and vegetation cover. Information on landslides and some of these influencing factors can be extracted from remotely-sensed data products through visual and digital image processing techniques. A comprehensive spatial database can be created in Geographic Information Systems (GIS) incorporating other ancillary information. In this paper a landslide hazard map is prepared using the information value method. Information Values are computed using all the thematic layers. The road network is draped over this hazard map and the road stretch that falls in the highly landslide prone area is identified. Finally an alternate route has been proposed ensuring safety from landslide hazard.

Rajeshwar Singh Banshtu, Chander Prakash

Mapping the Deformation of Shuping Landslide Using DInSAR and Offset Tracking Methods

Shuping landslide, belonging to Zigui county, Hubei province, is located on a north-inclined slope at the south bank of Yangtze River and about 50 km away from the Three Gorges Dam. The landslide occupies less than 1 km

2

and is covered by densely vegetations. Since the first impoundment of the Three Gorges Reservoir ended on June 15, 2003, the landslide has suffered obvious deformation. The maximum value of Shuping landslide in special month is up to several decimetres.

Concerning Shuping landslide displacement mapping, both DInSAR and offset tracking methods have been limited by the multi-metric spatial resolution of the previous generation of space-borne SAR sensors (e.g. ENVISAT ASAR or PALSAR).

In this paper we use 4 TerraSAR-X Spotlight images with submetric spatial resolution and apply both DInSAR and offset tracking method to map the deformation field of Shuping landslide. Three images acquired in January, 2012 are processed with DInSAR method. And the other one acquired in January, 2013. As for the offset tracking method, 1 pair with time baseline near 1 year is processed.

After the deformation field mapping, two deformation cones are identified by both DInSAR and offset tracking methods. It is shown by our work that high spatial resolution SAR data can provide an unprecedented level of high density and high precision measurement for recognizing the landslide surface deformation. Simultaneously, the measurement has the guiding function for selecting point location to GPS and leveling.

Jinghui Fan, Hao Lin, Ye Xia, Hongli Zhao, Xiaofang Guo, Man Li

Rainfall-Triggered Shallow Landslides Mapping Through Pleiades Images

This paper presents the analysis of Pleiades images for the detection and the mapping of rainfall-induced shallow landslides in an area located in the Northern Apennines of Italy. The high resolution of the used images allowed to efficiently recognize also the landslides with small size and to quickly create an inventory map of these phenomena. Field investigations carried up for checking the real presence of the mapped landslides showed a good agreement with the detected through Pleiades images landslides, also in terms of appearance and size of these phenomena. For these reasons Pleiades images can be an useful device for identifying landslides events and to create a complete database of susceptible areas.

Davide Zizioli, Claudia Meisina, Massimiliano Bordoni, Francesco Zucca

Monitoring the Activity of Landslides in the Coastal Zones of Reservoirs with SAR Interferometry

This work presents the preliminary results of the exploration of Synthetic Aperture Radar (SAR) data archives of Envisat and TerraSAR-X data with multitemporal interferometric techniques like Persistent Scatterers Interferometry (PSI) and Small Baseline Interferometry (SBAS). The analyses were performed on two test areas located in vicinity of Rożnów reservoir in Southern Poland and Three Gorges area in Hubei province in China. Both areas are very challenging for interferometric techniques due to the very rough topography, sparse urbanization, dense vegetation and forest cover. Therefore big part of the work was devoted to improvements of algorithms and data processing chain.

It was found that the number of detected Persistent Scatterers (PS) could be increased by improvements applied to interferograms generation. In terms of PSI processing a multi criteria Persistent Scatterers Candidates selection method was used. The authors noticed that for such problematic areas it is still possible to successfully detect a number of PS but, the interpretation of the associated deformation is difficult and requires further studies.

Zbigniew Perski, Guang Liu, Tomasz Wojciechowski, Fan Jinhui, Antoni Wójcik

Relative Age Estimation at Landslide Mapping on LiDAR Derivatives: Revealing the Applicability of Land Cover Data in Statistical Susceptibility Modelling

In statistical landslide susceptibility modelling the identification of appropriate explanatory variables describing the predisposing and preparatory factors for the landslides of a given inventory is important. In this context information on the age and the respective land cover at the time of occurrence is beneficiary. The potential of mapping very old (or prehistoric) landslides using LiDAR derivatives has not been analysed yet. Additionally, performing a visual interpretation of derivatives of a single LiDAR DTM it is not possible to assign the accurate age or date of the occurrence of the event to each mapped landslide. Therefore, commonly no information on the land cover at the time of landslide occurrence for these very old landslides (but also for younger ones) is available. The objective of this study is, to estimate the relative age of landslides during the mapping and to explore differences of the recent land cover distribution in the relative ages of the landslides. This is performed to evaluate the sustainability of including recent land cover data into susceptibility modelling. The relative age of the landslides is estimated for each landslide according to its morphological footprint on the LiDAR DTM derivatives and to its appearance on the orthophoto. The different relative ages assigned are “very old”, “old”, “young” and “very young”. The study area is located in three districts of Lower Austria, namely Amstetten, Baden and Waidhofen/Ybbs. The resulting inventory includes 1834 landslides and shows that the “very old” and “old” landslides (60 % of all mapped landslides) are mainly covered by forest (~60 % of all land cover types). We conclude that using this inventory including recent land cover data in the susceptibility model is not appropriate for Lower Austria. There is a potential of mapping “old” or “very old” landslides on the LiDAR derivatives. The absolute age remains unknown.

Helene Petschko, Rainer Bell, Thomas Glade

Automated Remote Sensing Based Landslide Detection for Dynamic Landslide Inventories

Dynamic landslide inventories are important for objective landslide hazard and risk assessment. Multi-temporal satellite remote sensing has the potential for automated landslide detection at a regional scale. For this purpose a new automated approach has been developed based on analysing temporal trajectories of NDVI values derived from a co-registered multi-temporal RapidEye data stack. Specific temporal footprints of vegetation changes enable identification of landslide events. Applying this approach to a 12,000 sqkm study area in Southern Kyrgyzstan, about 250 landslide events could be automatically detected between 2009 and 2012. Subsequent field checks have revealed that the vast majority of these events have been correctly identified. Thus, the developed approach is capable of automatically detecting different kinds of mass movements under diverse natural conditions.

Sigrid Roessner, Robert Behling, Karl Segl, Darya Golovko, Hans-Ulrich Wetzel, Hermann Kaufmann

Persistent Scatterer Interferometry (PSI) Technique for Landslide Characterization and Monitoring

Dealing with landslide, the availability of long time series of displacement often represents the most effective method to define its state of activity, to observe relationship with triggering factors and to assess the effectiveness of the mitigation measures. Moreover, the presence of a dense grid of measurements is essential to map correctly the boundary of the mass movements, to reconstruct the actual vector of displacement and to identify the deformation pattern. Persistent Scatterer Interferometry (PSI) represents an effective tool to measure landslide displacement, as it offers a synoptic view that can be repeated at different time intervals and at various scales. In this paper, PSI interferometry and conventional ground-based monitoring techniques have been integrated to characterize and to monitor the earth rotational slide threatening the Santo Stefano d’Aveto village in the Northern Apennines (Italy). On one hand, the in situ information recorded by inclinometers can help in defining the actual location of the sliding surface and the involved volumes of material. On the other hand, PSI measurements have allowed better redefining of the boundaries of the landslide, its state of activity and have allowed a better understanding of landslide geometry and kinematics. The integration of ground-based monitoring data and PSI data have provided sound results for landslide characterization.

Veronica Tofani, Federico Raspini, Filippo Catani, Nicola Casagli

Persistent Scatterers Interferometry Provides Insight on Slope Deformations and Landslide Activity in the Mountains of Zhouqu, Gansu, China

We present the results of Persistent Scatterers Interferometry (PSI) applied to investigate slope instabilities in a remote high mountain region of Southern Gansu, known to be prone to large magnitude (M7-8) earthquakes and catastrophic slope failures. The PSI processing of high resolution (~3 m) COSMO/SkyMed (CSK) satellite images produced spatially dense information (more than 1,000 PS/km

2

) on ground surface displacements in the area of Zhouqu, a town located in the Bailong River valley. A substantial portion of the radar targets showed significant displacements (from few to over 50 mm/year), denoting widespread occurrence of slope instabilities. In particular, the PSI results provided valuable information on the activity of some very large, apparently slow landslides that represent a persistent hazard to the local population and infrastructure. Monitoring movements of large long-lived landslides is important especially when, as in the case of the Bailong valley, they are known to undergo periods of increased activity resulting in river damming and disastrous flooding. Given the general lack of monitoring data on large landslides at Zhouqu and on other similar major failures that are common in Southern Gansu, the PSI-derived displacements offer unique information, which, following expert judgment, can be used for preliminary wide-area assessments of hazards linked to landslide activity. Furthermore, this study shows that with the high resolution CSK data resulting in high radar target density, PSI can also assist in slope/landslide-specific assessments.

Janusz Wasowski, Fabio Bovenga, Tom Dijkstra, Xingmin Meng, Raffaele Nutricato, Maria Teresa Chiaradia

Landslide Hazard Investigation and Assessment Using Remote Sensing in the Three Gorges Reservoir Area

Landslides can result in enormous property damages and human casualties in mountainous region, which are controlled and influenced by many temporal and spatial factors. Comprehensive understanding of landslides should be based on multi-source data collection, information extraction and data analysis. In this paper, landslide-prone area from Zigui to Badong in the Three Gorges Project reservoir area is chosen for the study area to landslide information extraction and hazard analysis based on multi-source data, which focused on the integration between remote sensing and non-RS data for landslide investigation and hazard analysis. And ten thematic maps were generated from multi-source data, namely landslides inventory map, slope map, slope structure map, geotechnical map, land cover and its changes map etc. The Support Vector Machine (SVM) model is employed for landslide susceptibility mapping. The results show a convincing success to distingusih the high and low landslide susceptibility regions.

Runqing Ye, Wenming Cheng, Xiaolin Fu, Runze Wu, Jianying Yang, Ruiqing Niu

Landslides Susceptibility Mapping in Oklahoma State Using GIS-Based Weighted Linear Combination Method

Oklahoma experiences approximately 20 reported landslides per year, which cause damage to transportation corridors and infrastructure. A refined regional hazard map has the potential ability to assist the state with detecting landslide hotspots and prevent future transportation corridor blockages. Combining the Geographic Information System (GIS) and high resolution satellite images, a first-cut landslide susceptibility map over the state of Oklahoma has been generated through the following two steps. The top four key landslide-controlling factors, including slope, soil texture type, land cover and elevation, were derived from a comprehensive geospatial database. After that, GIS-based weighted linear combination (WLC) method was utilized to assign the factor weight for each controlling parameter to generate the landslide susceptibility values, which are classified into five categories. Our study indicates that the entire state can be divided into five levels of susceptibility, namely very low (7.80 %), low (38.32 %), medium (45.15 %), high (8.09 %) and very high (0.64 %). These results match the historical landslide risk map well, especially in the south eastern and north western corner of the state. Further comparison with the landslide inventory data provided by the Oklahoma Department of Transportation (ODOT) and U.S. Geological Survey (USGS) shows that, 17 out of 19 (ODOT) and 60 out of 86 (USGS) events are located in category “high” or “very high”, which demonstrates the ability of WLC method in predicting landslide prone areas.

Xiaogang He, Yang Hong, Xiaodi Yu, Amy B. Cerato, Xinhua Zhang, Marko Komac

InSAR-Based Landslide Location and Monitoring in Alpine Valley Region

Synthetic Aputure Radar Interferometry (InSAR) has become an important technique for monitoring ground movement and it has the advantage that other method cannot compare on the wide area dynamic investigation and monitoring. Thus, InSAR technology has been widely used in the investigation of geologic hazards, such as subsidence, landslide, earthquake, and volcanic activity. But, it is still in the research and practice application stage for the landslide investigation and monitoring of InSAR technology in the complex terrain area. In this paper, based on the rationale and algorithms of InSAR technology, combined with the topography and landform characteristic of landslide disasters, the ground local incidence angle of each point is derived by the geometric model which is established by the satellite Line-of-sight inclination, the slope and aspect of the ground point. And then, the reliable interference areas are determined by the relationship analysis among the local incidence angle, the backward scattering and the coherence of InSAR. Finally, the application example is achieved by using L-band Synthetic Aperture Radar data of the Advanced Land Observing Satellite, potentially moving landslide areas and landslide hazard areas are located, at the same time, the monitoring results of the typical landslide are analyzed in detail.

Guijie Wang, Yueping Yin, Mowen Xie, Weilun Wu

Use of Satellite and Ground Based InSAR in Hazard Classification of Unstable Rock Slopes

A newly developed hazard classification system for large unstable rock slopes depends on the evaluation of a number of criteria. These criteria include both displacement rates and the structural development of the unstable slope. Satellite and ground-based interferometric radars have the potential to measure the displacement of active rockslides. By using several complimentary InSAR datasets, with different viewing geometries, we are able to assess both movement criteria and a number of criteria related to structural development of the bounding surfaces.

We have collected five years of high resolution satellite imagery using several viewing geometries for the Gamanjunni 3 rockslide in northern Norway. In addition, we have collected radar using a ground-based radar. The results show a clearly defined block moving as a wedge. However, the decrease in movement velocity and steepness towards the lower part of the slope, along with the lack of visible basal structures, indicates that rock creep acts at the base of the slide body.

John F. Dehls, Tom Rune Lauknes, Reginald L. Hermanns, Halvor Bunkholt, Tom Grydeland, Yngvar Larsen, Harald Ø. Eriksen, Trond Eiken

Hazard Mapping

Frontmatter

Introduction: Hazard Mapping

Twenty papers were accepted into the session on landslide hazard mapping for oral presentation. The papers presented susceptibility and hazard analysis based on approaches ranging from field-based assessments to statistically based models to assessments that combined hydromechanical and probabilistic components. Many of the studies have taken advantage of increasing availability of remotely sensed data and nearly all relied on Geographic Information Systems to organize and analyze spatial data. The studies used a range of methods for assessing performance and validating hazard and susceptibility models. A few of the studies presented in this session also included some element of landslide risk assessment. This collection of papers clearly demonstrates that a wide range of approaches can lead to useful assessments of landslide susceptibility and hazard.

Rex L. Baum, Toyohiko Miyagi, Saro Lee, Oleksandr M. Trofymchuk

Landslide Hazard Evaluation Using Artificial Neural Networks and GIS

Lantau Island within the territory of Hong Kong has natural and undeveloped terrain (Dai et al. 2001), along with intense and frequent rainfall. It is thus a suitable area for preparation of a landslide susceptibility map of the area. The methods of using Landslide Susceptibility Values (LSV) and artificial neural networks (ANN) were applied in the GIS environment of ArcGIS 9.3 to prepare two landslide susceptibility maps of Lantau Island. The application of LSV and GIS to produce a landslide susceptibility map included the determination of LSV values of causative factors and calculation of a cumulative Landslide Susceptibility Index (LSI) for each pixel which was used to decide zones susceptible to landslides. The application of ANN required initially the preparation of input vectors from causative factors and output vectors of landslide susceptible zones by taking the LSV-produced map as the reference. The neural networks were trained and tested using the Neural Network Toolbox in MATLAB. The best network was obtained and applied further to predict the landslide susceptible zones for the whole study area and a landslide susceptibility map was prepared. These maps were compared with each other and with the landslide susceptibility map produced by Dai et al. (2001) using a logistic regression model. The landslide susceptibility map produced by applying ANN predicted more landslide susceptible regions with high and moderate susceptibility in the study area compared to the map produced using LSV. However, for some regions of the study area the LSV method performed better than the ANN method. Nevertheless, both methods produced quality maps and the performance of ANN was satisfactory, even with a small training dataset.

Alok Bhardwaj, G. Venkatachalam

Landslide Susceptibility Mapping Using Remote Sensing and GIS: Nueva Colombia, Chiapas, Mexico.

In Mexico, landslides are one of the most important natural hazards as they cause considerable human and economic losses. Such phenomena are recurring due to the physical characteristics of the country, characterized by mountain ranges with steep slopes, diverse geology and intensive seasonal rains. The physical environment coupled with the impact of human activities, for example, deforestation and land use change, worsen the conditions of the landscape increasing landslide susceptibility.

The village of Nueva Colombia, situated in the municipality of Angel Albino Corzo in the state of Chiapas, is often affected by the occurrence of landslides. In 2005 and 2010, rainfall triggered landslides seriously damaged crops, destroyed housing and disrupted the main infrastructure.

Located in the southern sector of the state of Chiapas, the town is situated in the mountainous part of the Sierra Madre del Sur. Tropical weather of the area involves a strong rainy season, which combined with the mountainous conditions produces high level of susceptibility to landsliding. This situation is of great importance due to the vulnerability of the exposed population, particularly people of the village of Nueva Colombia.

A landslide inventory using SPOT images was used to generate a susceptibility map by implementing the weights of evidence method. This process relied on remote sensing techniques and geographic information systems (GIS). Preliminary results are presented in this paper.

Ixtlitzin Bravo-Carvajal, Ricardo J. Garnica-Peña, Luis C. López-Bravo, Irasema Alcántara-Ayala

Landslide Susceptibility Model Validation: A Routine Starting from Landslide Inventory to Susceptibility

The main purpose of the present study is to evaluate the model validation stage of a routine landslide susceptibility mapping. For the purpose, model validation is assessed in three stages; (1) during model data production, (2) during model construction, and (3) during the production of model consequences; landslide susceptibility maps. As the results of these evaluations, it is revealed that training and testing data sets should be separated considering an appropriate separation ratio which is about 80 % and 20 % of the presence (1) data after completion of inventory studies. Correct classification percentages, error matrices, and the Kappa index are suggested to be considered for the training data sets during model construction. Additionally, again the correct classification percentage and the Root Mean Square Error (RMSE) should be considered during this stage for the testing data sets as well. In order to evaluate the spatial performance of the produced landslide susceptibility maps, the use of the Receiver Operating Characteristic (ROC) curves and the Area Under Curve (AUC) statistics is recommended. In the present study, the maximum Kappa index (k) value was calculated to be 0.459 for both the random sampling 1 (Rnd1) in the model 1 and for the random sampling 2 (Rnd2) in the model 2 during the model construction stage. The AUC values were calculated for these random samplings to be 0.781 and 0.790 respectively during the production of the model consequence stage in the study.

Gulseren Dagdelenler, Hakan A. Nefeslioglu, Candan Gokceoglu

GIS-Based Landslide Susceptibility Mapping Using a Certainty Factor Model and Its Validation in the Chuetsu Area, Central Japan

The principal aim of this study is to assess the landslide susceptibility in the Chuetsu area, Niigata Prefecture, Central Japan, using a certainty factor model in a GIS environment. The landslide inventory data used in this study were obtained from the National Research Institute for Earth Science and Disaster Prevention (NIED). The data were divided into two groups: one for training the model and the other for its validation. Seven relative factors, elevation, slope angle, slope aspect, density of geological boundary, density of drainage network, plan curvature, and lithology were utilized for this susceptibility analysis. Based on the aforementioned correlative factors, a landslide susceptibility map was produced and then verified using receiver operating characteristics (ROC). The value of area under the ROC curve (

AUC

) of the constructed CF model is 0.82. A model with such a high

AUC

value is considered good and therefore acceptable in predicting landslides. The landslide susceptibility map prepared in this study can hence be used to mitigate risks associated with landslides in the study area.

Jie Dou, Takashi Oguchi, Yuichi S. Hayakawa, Shoichiro Uchiyama, Hitoshi Saito, Uttam Paudel

Landslide Susceptibility Mapping Using a Grid-based Infiltration Transient Model in Mountainous Regions

Rainfall-induced landsliding is the major sediment-related disaster in the mountainous regions of Korea. Landslide susceptibility mapping, which is the principal approach to identifying areas prone to landslides, provides decision-makers with the policy priorities for mitigation and prevention measures. A revised TRIGRS (Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis) model was employed to estimate areas that would be unstable after rainfall occurred. Design rainfall data was statistically derived and input into the model. The influence of trees was considered in terms of tree surcharge and tree root cohesion. A regional estimate of landslide-prone areas was then conducted using the model. Unstable hillslope conditions vary temporally and spatially on a regional scale with soil, topography, and land use/cover.

Dongyeob Kim, Eun Jai Lee, Byungkyu Ahn, Sangjun Im

Evaluating a Slope-Stability Model for Shallow Rain-Induced Landslides Using Gage and Satellite Data

Improving prediction of landslide early warning systems requires accurate estimation of the conditions that trigger slope failures. This study tested a slope-stability model for shallow rainfall-induced landslides by utilizing rainfall information from gauge and satellite records. We used the TRIGRS model (Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis) for simulating the evolution of the factor of safety due to rainfall infiltration. Using a spatial subset of a well-characterized digital landscape from an earlier study, we considered shallow failure on a slope adjoining an urban transportation roadway near the Seattle area in Washington, USA.

We ran the TRIGRS model using high-quality rain gage and satellite-based rainfall data from the Tropical Rainfall Measuring Mission (TRMM). Preliminary results with parameterized soil depth values suggest that the steeper slope values in this spatial domain have factor of safety values that are extremely close to the failure limit within an extremely narrow range of values, providing multiple false alarms. When the soil depths were constrained using a back analysis procedure to ensure that slopes were stable under initial condtions, the model accurately predicted the timing and location of the landslide observation without false alarms over time for gage rain data. The TRMM satellite rainfall data did not show adequately retreived rainfall peak magnitudes and accumulation over the study period, and as a result failed to predict the landslide event. These preliminary results indicate that more accurate and higher-resolution rain data (e.g., the upcoming Global Precipitation Measurement (GPM) mission) are required to provide accurate and reliable landslide predictions in ungaged basins.

Soni Yatheendradas, Dalia Kirschbaum, Rex L. Baum, Jonathan W. Godt

Landslide Susceptibility Modeling on Regional Scales: The Case of Lower Saxony, NW Germany

This paper presents a regional landslide susceptibility model for the Federal State of Lower Saxony, NW Germany. A modified Information Value approach has been developed, which uses bivariate statistics to identify the spatial probability of landslide occurrence. To optimize the approach for regional applications, several modifications have been made: landslide pixel mapping is replaced by point representation and the weighting function uses landslide densities based on attribute areal coverage. The input data of the landslide susceptibility model include a spatial inventory of about 900 landslides and different data sets of geomorphometry, lithology, and land use.

The model predicts that about 2 % of Lower Saxony shows significant landslide susceptibility. Most of the unstable terrain is concentrated in three key areas in the Lower Saxon Uplands. The spatial patterns of landslide susceptibility are strongly correlated with the regional relief. The most relevant predisposing factors are slope gradients between 21° and 49° as well as different types of Mesozoic sedimentary rock, especially lime- and claystone formations. In conformity with lithology, land use can be of stabilizing or destabilizing influence, but its significance is less important.

The developed approach provides the capability to manage critical problems of regional data processing and proves to be an effective modeling tool for regional applications. Although the model validation indicates good predictive power and high spatial accuracy, the study has shown that regional landslide susceptibility modeling has major data-related and conceptual deficits. Some of these shortcomings are discussed in this paper in detail.

Martin Klose, Daniel Gruber, Bodo Damm, Gerhard Gerold

Regional Scale Landslide Susceptibility Mapping in Emilia Romagna (Italy) as a Tool for Early Warning

The Emilia Romagna region (22,446 km

2

, Northern Italy) is widely affected by landslides. The Civil protection Agency of the Emilia Romagna Region uses a regional scale warning system (WS) for the management of the risk related to rainfall induced landslides. The WS is used to perform a temporal forecasting of landslides, as it provides an alert level for each of the eight subdivisions (called alert zones—AZ) of the regional territory.

To improve the spatial information of the WS, we developed a susceptibility map and we tested the feasibility of coupling the temporal forecasting of the WS with the spatial forecasting of the susceptibility map.

To map the landslide susceptibility at regional scale, we adopted a simple implementation of the Random Forest (RF) classification family. Random forest is a combination of tree (usually binary) Bayesian predictors that allows relating a set of contributing factors with the actual landslides occurrence. As a non-parametric model, it is possible to incorporate a wide range of numeric or categorical data layers and there is no need to select unimodal training data.

Many classical and widely acknowledged landslide predisposing factors have been taken into account as mainly related to lithology, land use and morphometry (primary and secondary attributes derived from the DTM). The use of random forest enabled us to estimate the relative importance of the single input parameters and to select the optimal configuration of the regression model: an automated procedure selected the optimal configuration of parameters discarding the uninfluential and the pejorative ones. To develop the susceptibility map we considered the parameter set characterized by the lowest misclassification probability. To calibrate the model we used a training set and a test set considering the 10 % of the study area with random sampling. Following this approach we obtained a regional scale susceptibility map with 100 m resolution.

We verified that the majority of the landslides forecasted by the WS in the past 7 years (this dataset is completely independent from the one used for the susceptibility assessment) occurred in areas mapped as highly (53 %), very highly (26 %) or moderately (19 %) susceptible to landsliding. Therefore, we concluded that the regional scale susceptibility map can be fruitfully exploited by Civil Protection Authorities to better focus their efforts in case of warnings issued by the regional warning systems.

Daniela Lagomarsino, Samuele Segoni, Riccardo Fanti, Filippo Catani, Nicola Casagli

GIS-Based Probabilistic Analysis of Shallow Landslide Susceptibility Using a Transient Hydrogeological Model and Monte Carlo Simulation

This study proposes a GIS-based probabilistic analysis method for rainfall-induced shallow landslide susceptibility over an extensive area by integrating a transient hydrogeological model with a Monte Carlo simulation. The geomechanical parameters (such as cohesion and friction angle) used in the slope model have been considered as random variables due to the uncertainty and variability caused by complex geological conditions and spatial variability. Therefore, to properly account for the uncertainty in geomechanical parameters, a probabilistic analysis method should be used and Monte Carlo simulation was used in this study. In addition, the transient hydrogeological model was coupled with an infinite slope model to assess the pore-pressure response caused by transient rainfall infiltration. This process was performed in GIS-based environments, since GIS has strong spatial data processing capacity. The proposed approach was applied to the Inje area, Korea, which experienced a large number of landslides in July 2006, in order to evaluate its feasibility. The spatial database for input parameters and the landslide inventory map were constructed in a grid-based GIS environment. To evaluate the performance of the model, the results of the landslide susceptibility assessment were compared with the landslide inventory using receiver operating characteristics (ROC) graphs. The proposed approach demonstrated good predictive performance when compared with landslide occurrence locations. In addition, the probabilistic analysis showed better performance than the deterministic analysis.

Jung-Hyun Lee, Hyuck-Jin Park

Collapse Landslide and Mudslides Hazard Zonation

This paper aims at finding out the functional relationship between collapse landslide mudslides and its impact factors through statistical analysis under logistic regression model and certainty factor. This study tries to map hazard zonation according the level of risk of collapse landslide and mudslides occurring in Guizhou Province using GIS technology. The result shows that the hazard zonation method based on logistic regression model and certainty factor for collapse landslide and mudslides is effective.

Mingxue Liu, Xiang Chen, Shanni Yang

Mapping and Management of Landslide Risk in the City of Azazga (Algeria)

The management of major landslides faces several difficulties especially when important stakes are exposed to risk. The landslide of the city Azazga is one of the most extensive cases observed in Algeria. This is an instability reactivated by specific climate events such as floods of 1974 and snow of 2012. Landslides affect the center town of the region of Azazga situated 20 Km East of Tizi-Ouzou (northern Algeria). They affect a highly urbanized area and endanger vital structures such as the regional hospital. Managing this risk requires the development of an effective management methodology as well as a good knowledge of site conditions, the causes and the extent of the landslide. To better characterize this extensive instability, a geographic information system was created for the study site. This GIS greatly facilitates the interpretation of spatial data.

The aim of this work is to investigate the potential risk posed by landslides in the city of Azazga. This potential is estimated from observations and exploration of the site using the method of Djerbal and Melbouci (2013). A risk management methodology is then developed for this site. The results obtained show that the very strong hazard affects a large area of the city Azazga.

Lynda Djerbal, Nassima Alimrina, Bachir Melbouci, Ramdane Bahar

Landslide Susceptibility Analysis of Belgrade City Area

This article presents preliminary results of a recent analysis of landslide susceptibility over the wider Belgrade City area. Suburban areas of Belgrade have been of particular interest because they are sprawling rapidly and without regulations, so the city needs a regulation plan in these areas. Landslide susceptibility mapping, which has been demonstrated in this work, provides one of the criteria (relative stability of the terrain) for developing such a plan. The analyses of susceptibility involved a state-of-the-art technique based on a machine learning algorithm. The procedure required input data in the form of thematic raster datasets, represented by various geological, geomorphological, and environmental features of the area, as well as a valid landslide inventory for training the algorithm. The resulting map depicts zones of relative (high–low) susceptibility and correlates well with the existing inventory.

Miloš Marjanović, Uroš Ðurić, Biljana Abolmasov, Snežana Bogdanović

Study on Earthquake-Triggered Landslide Hazard Assessment Under Rainfall Condition

Landslides’ occurrence results from not only the environmental background conditions of slopes, but also triggering factors, such as rainfall and earthquake etc. This study selected Pengzhou, Dujiangyan, Chongzhou and Dayi cities as the research area, which were affected severely by Wenchuan Ms 8.0 Earthquake. At the aim of assessing regional landslide hazard under the conditions of heavy rainfall and Ms 8.0 earthquake, Newmark model and hydrological distribution model were adopted based on GIS technology. First, the whole study area was divided into cells with grid size 30 m × 30 m and the Newmark displacement of each grid in the region was calculated under the roles of heavy rainfall and earthquake. And then, make a coupling analysis between the Newmark displacements and landslides inventory map to establish a curve equation, which will give the hazard degree to each grid. Finally, the earthquake-triggered landslide hazard assessment map was completed. The result shows that the moderate and high hazardous regions cover 37.1 % area and are containing about 82 % landslides. The landslide density has a great relationship with hazard degree and it is increasing with the hazard level increase, which implies the result is accord with the reality and can be used to provide the research foundation for the landslide risk management and the reference for the regional reconstruction planning.

Meng Wang, Jianping Qiao, Lili Shi

A GIS Approach to Analysis of Deep-Seated Slope Stability in Complex Geology

We demonstrate the computer model r.rotstab.layers to explore the possibilities of GIS for catchment-scale deep-seated slope stability modelling in complex geology. This model makes use of a modification of the three-dimensional sliding surface model proposed by Hovland and revised and extended by Xie and co-workers. It evaluates the slope stability for a large number of ellipsoidal random slip surfaces which may be truncated at the interfaces between geological layers. This results in a spatial overview of potentially unstable regions. After demonstrating the functionality of the model with an artificial cone-shaped terrain, we test r.rotstab.layers for the 10 km

2

Ripoli area in Umbria, central Italy. According to field observations in the Ripoli area, morpho-structural settings play a crucial role for deep-seated landslide distribution. We have prepared a model of the geological layers based on surface information on the strike and dip of each layer, and we use this model as input for r.rotstab.layers. We show that (1) considering the geological layers is essential for the outcome of deep-seated slope stability modelling, and (2) the seepage direction of the groundwater is a major source of uncertainty.

Ivan Marchesini, Martin Mergili, Mauro Rossi, Michele Santangelo, Mauro Cardinali, Francesca Ardizzone, Federica Fiorucci, Barbara Schneider-Muntau, Wolfgang Fellin, Fausto Guzzetti

Risk Evaluation of Landslide Topographic Area by Aerial Photointerpretation

Landslide topographies are widely distributed in Japan and amount to more than 300,000 sits. The area has potential for various kinds of slope disaster such as reactivation, and high potential of slope failure because of the weak geology. Some landslide deposits are stable already.

Consequently, some method of the risk evaluation is needed. The authors review the history of landslide risk evaluation. The approach started by aerial photointerpretation. The comparative study between the surface features and inner characteristics has a long history. And the AHP approach for risk evaluation is also established.

Toyohiko Miyagi, Eisaku Hamasaki

Accounting for Variability in Rain-Event Intensity and Initial Conditions in Landslide Triggering Return Period Mapping via a Monte Carlo Approach

In this study, a Monte Carlo simulation approach is proposed for mapping landslide hazard in terms of return period, in order to account for both rainfall high frequency variability and antecedent precipitation that determine initial conditions. The Monte Carlo approach combines a stochastic rainfall generator with a physically-based landslide triggering model. More in detail, the Monte Carlo simulation methodology comprises the following elements: (a) a seasonal Neyman-Scott Rectangular Pulses (NSRP) model to generate 1,000-years of synthetic hourly point rainfall data; (b) a module for rainfall event identification and separation from dry intervals; (c) the Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability (TRIGRS) model, version 2 (Baum et al. 2008, 2010) to simulate landslide triggering by rainfall infiltration, integrated with (d) a water table recession (WTR) model aimed at computing the initial water table height to be used in simulating rainfall events with event-based model TRIGRS.

An application of the method is carried out to map landslide triggering hazard in the Loco catchment, located in the Peloritani Mountains, Sicily, Italy, an area highly prone to landslide risk.

Results show that return period estimation may be significantly affected by both rainfall high-frequency variability and antecedent precipitation. Comparison with results obtained from the IDF-based procedure, shows that the latter widely-used approach generally leads to an overestimation of the return period of landslide triggering, i.e. a non conservative estimation of landslide hazard. Hence the IDF-based approach should be properly modified to account for at least the effect of antecedent precipitation.

David J. Peres, Antonino Cancelliere

Predictive Capability of Deterministic and Statistical Models in Weathered Granite Soil Watershed

Every year, the Republic of Korea experiences numerous landslides, resulting in property damage and casualties, especially in weathered granite soil slopes.

This paper compares the predictive capability of two different models, namely shallow landslide stability (SHALSTAB), deterministic model and relative effect (RE) model, a statistical bivariate model for producing shallow landslide susceptibility maps.

Deokjeok-ri Creek was selected for the study. The watershed is mainly covered by granitic soil. For SHALSTAB analysis a digital elevation model was used. The soil strength parameters and physical properties of soil were determined in the laboratory. For the statistical model, the input layers of the landslide conditioning factors were prepared in the first stage. The effects of causative factors on slope stability were mapped on topographical maps of 1:5,000 scale. Mainly geomorphic (slope, aspect, elevation, internal relief, and slope shape), hydrology based (drainage distance, stream power index, topographic wetness index, sediment transport index, drainage density and soil drainage characters), soil type and soil depth distribution and forest type and timber age causative factors and field inventory were used for statistical susceptibility mapping. Model performance was assessed using accuracy curve approach. Results show that accuracy is as high as 88.21 % for SHALSTAB, while it is 86.3 % for RE model. Although SHALSTAB has certain drawbacks, as described by previous researchers, this study concluded that in a small watershed and using accurate geotechnical data SHALSTAB can predict the probability of slope failure in Korean mountainous regions.

Ananta Man Singh Pradhan, Jeong-Rim Oh, Min-Su Jung, Yun-Tae Kim

Area Based Landslide Hazard and Risk Assessment for Penang Island Malaysia

The demand for infrastructure development and building construction has encouraged development over new areas of challenging terrain and encroachment into existing, otherwise stable, highland areas. In 2008, The Slope Engineering Branch (CKC) of The Public Works Department had initiated a Slope Hazard and Risk Assessment in Hulu Kelang Ampang Area. In 2010, CKC again has extended the slope hazard and risk assessment to other critical areas i.e., Penang Island which is in line with the long term plan in the National Slope Master Plan. Penang Island has a history of landslide damages following heavy rains. As many development and housing projects are taking place at the hilly terrain, the hill slopes are not exempted for building platforms and excavation in the hilly areas around Penang island is rapidly increasing, amidst regulatory concerns. This has resulted in incidences of geotechnical instability causing numerous landslips, some of which are fatal.

In view of formulating medium term and long term measures towards an effective policy of inspection and monitoring of development in Penang island, An area based landslide hazard assessment was proposed to initiate a slope hazard assessment and mapping for the proposed area. Geographical Information System (GIS) was adopted as the base machine for the production of the landslide hazard and risk map. This paper highlights the area based landslide hazard and risk assessment using GIS application. The landslide hazard and risk assessment methodology and map preparation using GIS application for the study are also highlighted.

Shabri Shaharom, Low Tian Huat, Mohd Asbi Othman

Landslide Hazard Mapping Using a Poisson Distribution: A Case Study in Penang Island, Malaysia

Landsliding is one of the most destructive natural geohazards in Malaysia. Landslide hazard maps are very useful for urban development planning. This paper presents landslide hazard mapping using a new approach, i.e. a Poisson distribution, and compares the result with previous probabilistic approaches, i.e. frequency ratio (FR), statistical index (SI) and landslide nominal susceptibility factor (LNSF). These approaches were implemented in Penang Island to produce landslide hazard maps. The landslide causative factors considered are elevation, slope gradient, slope aspect, curvature, land cover, vegetation cover, distance from nearest road, distance from nearest stream, distance from nearest fault line, geology, soil texture and precipitation. Landslide hazard maps were assessed using the Receiver Operating Characteristics (ROC) method. Accuracy obtained for FR, SI and LNSF are 78.52 %, 78.12 % and 72.93 % respectively. Poisson distribution approach gives high accuracy of 78.51 % as FR.

Lea Tien Tay, Habibah Lateh, Md Kamrul Hossain, Anton Abdulbasah Kamil

Shallow Landslide Susceptibility Mapping for Zagreb Hilly Area, Croatia

The aim of this study is to map the landslide susceptibility of the hilly area of Mt. Medvednica located in the northwestern part of the City of Zagreb, Croatia. Landslides in this region are mostly shallow movements of superficial deposits along contacts with fresh deposits of soil and cause significant economic losses by damaging houses and the urban infrastructure. The method used here is the deterministic slope stability analysis model SINMAP which is developed by Pack et al. (A stability index approach to terrain stability hazard mapping. SINMAP user’s manual, 1998; A stability index approach to terrain stability hazard mapping. SINMAP user’s manual, 2005). SINMAP is a raster based slope stability predictive tool based on coupled hydrological-infinite slope stability model. This approach applies to shallow translational landsliding phenomena controlled by shallow ground water convergence. The input data required for this model are (1) inventory of past landslides in a point vector format, (2) Digital Elevation Model (DEM) of the study area, (3) geotechnical data such as soils strength properties, thickness of soil above the failure plane, and (4) hydrological data such as soil hydraulic conductivity and the rainfall. Because the geotechnical data and hydrological data are highly variable in both space and time, the method does not require numerically precise input and accepts ranges of values that represent this uncertainly. The major output of this model is the stability index grid theme, which can be used as a landslide susceptibility map. The results also provided slope area plots and statistical summary for each calibration region in the study area facilitating the data interpretation. The landslide susceptibility map which is developed in this study is also compared with the results from the Analytic Hierarchy Process (AHP) method and aerial photo interpretation.

Chunxiang Wang, Snjezana Mihalić Arbanas, Hideaki Marui, Naoki Watanabe, Gen Furuya

Hazardous Activation of Landslides Within Western Carpathian Region (Ukraine)

The Western Carpathian Region (Zakarpatska territory of Ukraine) occupies 2 % of Ukrainian territory but about 5 % of total quantity of landslides (22,000) are situated there. Specific spatial density of landslides is four times greater than the rest of the territory. Anomalous levels of the landslide activity within the Western Carpathian Region is the result of active interaction tectonic (high density of faults), hydrological (dense river net) and hydrometeorological (regional precipitations two times more) factors. During the last two to three decades regional landslide activation is connected with the influence of global climate changes (GCC). Main factors of the GCC influence on the additional landslide activation are the following:

Increasing of the storm rainfall;

Rising of the river water level during flooding.

Olexandr Trofymchuk, Olexandr Kolodyazhnyy, Evgeniy Yakovlev

Monitoring, Prediction and Warning of Landslides

Frontmatter

Introduction: Monitoring, Prediction and Warning of Landslides

The WLF3 B5.Session Monitoring, prediction and warning of landslides, as a part of WLF3 session Group B. Sessions for Methods of Landslide Studies, gathers the main elements in the landslides risk reduction and landslides sustainable disaster management: monitoring, prediction and warning of landslides. Sixteen contributions from eleven countries around the world have been submitted and, after review process, accepted for publishing. The best practice techniques and experiences on monitoring, prediction and warning of landslides caused by different triggering factors are presented in this Session. In this introduction to the WLF3 B5 Session Monitoring, prediction and warning of landslides, a short summary of each of the accepted papers is presented divided regarding to their general topics.

Željko Arbanas, Teuku Faisal Fathani, Ziaoddin Shoaei, Byung-Gon Chae, Paolo Tommasi

Suggestion of a Landslide Early Warning Method Using a Gradient of Volumetric Water Content

This study involved the installation of a real-time monitoring system to observe physical property changes in soils in a slope during rainfall events. This monitoring included the measurement of volumetric water content, which was compared with the results of laboratory flume tests to identify landslide indicators in the soils. The response of volumetric water content to rainfall events is more immediate than that of pore-water pressure, and volumetric water content retains its maximum value for some time before a slope failure. Therefore, an alternative method for landslide monitoring can be based on the observation of volumetric water content and its changes over a time at shallow soil depths. Although no landslide occurred, the field monitoring results showed a directly proportional relationship between the effective cumulative rainfall and the gradient of volumetric water content per unit time (

t/t

max

). This preliminary study thus related slope failure to the volumetric water content gradient as a function of rainfall. Laboratory results showed that a high amount of rainfall and a high gradient of volumetric water content can induce slope failure. Based on these results, it is possible to suggest a threshold value of the volumetric water content gradient demarcating the conditions for slope stability and slope failure. This threshold can thus serve as the basis of an early warning system for landslides considering both rainfall and soil properties.

Byung-Gon Chae, Junghae Choi, Yong-Seok Seo

RADAR Images Supporting Rescue and Recovery Actions for Landslide and Flood Disasters: A Rio de Janeiro State Case Study

The use of RADAR images for monitoring natural disasters has two advantages compared to optical satellite images: RADAR images can be collected day or night, and regardless of weather. In major disasters related to landslides or floods, weather conditions are adverse and generally includes dense cloud cover that prevents use of optical satellite images. In a project approved between the Japan Aerospace Exploration Agency and the University of Rio de Janeiro State, there was an agreement to transfer up to twenty PALSAR2 images (with up to one meter spatial resolution) for monitoring natural disasters related to landslides or floods in Rio de Janeiro State. The procedure for monitoring is to collect ten images before the Brazilian rainy season (which in Rio de Janeiro starts in November-December and finishes around March-April. This is the opposite of Asia, which is in the dry season, so the satellite can be provided quickly in this period) to be used to obtain reference images for the follow methods: Coherent Change Detection (CCD) and Differential/Polarimetric Interferometry (DInSAR/Pol-InSAR). When a disaster with landslides or floods happens, it will be possible, to quickly and without any weather problems, detect if some land has slipped (mapping potential areas to slip), and if some areas are flooded. The main objective of this project is to subsidize the creation of maps for government agencies to use in planning strategies to minimize the hazard impacts and to assist governmental agencies at two stages: (1) during the disaster: helping rescuers and rescue efforts, indicating priority areas to be worked on and the numbers of people affected; and (2) after the disaster: mapping the extent of the affected areas, to assist in planning the recovery of these areas.

Francisco Dourado, Aline Freitas, Nelson Fernandes

Application of Low-Cost Tools and Techniques for Landslide Monitoring

This paper proposes a low-cost landslide monitoring system using the Reverse Real-Time Kinematic (RRTK) technique. The server-based processing technique, which utilizes the two-way communication channel for the computation and transmission of the user’s accurate position, is discussed. The basic infrastructure requirements for RRTK in low-cost landslide monitoring application are described. In order to implement the proposed RRTK algorithm, real-time data streaming of raw Global Positioning System (GPS) data of both the reference and rover station(s) to the control centre, are performed. A high pass filtering technique was employed to detect outliers in the observations. Finally, the autocorrelation of GPS time series was investigated to validate the presence of white and coloured noises in the GPS observations.

Etim Eyo, Tajul Musa, Kamaludin Omar, Khairulnizam M. Idris, Temel Bayrak, Ifeanyi Onuigbo

An Adaptive and Sustained Landslide Monitoring and Early Warning System

Areas prone to mass movement are widespread in Indonesia. The potential for landslide disasters in several regions is controlled by the geotechnical and geological conditions and triggered by high intensity rainfall and/or earthquake activity. The vulnerability to landslides is made worse by intensive land-use development. The urgent issues to be addressed are the dense populations residing in areas prone to mass movement and the failure to relocate the local people to safer areas for socio-economic reasons. Therefore, landslide monitoring, prediction, and early warning systems are urgently required to guarantee the safety of communities living in such areas. A long running and sustainable community-based landslide monitoring and early warning system (EWS) has been developed in Indonesia, with establishment of collaboration among the local government, universities, private sectors, NGOs, and the disaster management community. The main purpose of the program is to establish a strategic approach for disaster risk reduction through the implementation of information flow (for warning levels) and order/command systems (for evacuation). These activities have already met the community needs, helped save lives, and continued to obtain solid community support. In order to extend the effort, further challenges are to expand the project coverage, and propose more effective landslide monitoring, early warning, analysis, and visualization. In addition, the capabilities in socio-economic risk assessment need to be expedited to help identify those most at risk within the community. This paper describes the achievements and the current activities of the IPL Project (IPL-158) “Development of Community-based Landslide Early Warning System”.

Teuku Faisal Fathani, Dwikorita Karnawati, Wahyu Wilopo

Early Warning and Real-Time Slope Monitoring Systems in West and East Malaysia

This paper presents the application of slope safety warning systems on two slopes along strategic roads in Malaysia. The systems are used as an alternative to further structural reinforcement or remedial work. Their purpose is to provide long-term monitoring and early warning to facilitate the understanding of slope behaviour, and to manage landslide risk faced by road users. The first application is in West Malaysia. It is a slope cut that is located at the 46th km of the Simpang Pulai—Kuala Berang Highway. The second case is an embankment fill located at the 50.4th km of the Federal Road 500 between Penampang and Tambunan of Sabah. The first slope has had a long history of continual slow deformation, while the behaviour of the latter is closely linked with rainfall conditions. In view of the distinct slope movement patterns, on-site instrumentation techniques are different, and geodetic, geotechnical and hydrogeological monitoring techniques are utilised. As the slopes are situated in mountainous terrain, unfavourable weather conditions and remoteness of the sites pose serious challenges to the specification of lightning protection, power supply and data communication systems. Although the on-site system components are site specific, they are controlled by the same web-based instrumentation data management system. To allow representative indices of slope instability to be used in the warning module of the systems, diverse criteria are adopted. Apart from the conventional ones that make use of rainfall, groundwater level and soil deformation/movement, for the slope in Perak, creeping as described by landslide velocity is incorporated as a warning indicator. To reduce the likelihood and consequences of catastrophic collapse, understanding of slope behaviour is a pre-requisite. Such understanding is possible with systems that provide timely measurement of actual slope performance, and an early warning for impending danger.

William H. T. Fung, Richard J. Kinsil, Suhaimi Jamaludin, Sashi Krishnan

A National Warning System for Rainfall-Induced Landslides in Slovenia

In Slovenia intense short and less intense long-duration rainfall is a primary cause of shallow landslides that some estimates put at 10,000, or approximately one landslide per two square kilometres. These events impose a huge burden on local and state budgets, occasionally even taking lives. At least part of the damage (and the loss of lives) could be prevented with a reliable near real-time landslide hazard forecast system that would continuously draw from three data/model pillars: the precipitation forecast model, the landslide susceptibility model and the rainfall triggering values for landslide occurrence. Each of the three pillars brings some uncertainty to the landslide hazard forecast. A project was set up to forecast the possible occurrence of rainfall-induced landslides in Slovenia (acronym “Masprem”), tackling all three pillars, but focusing primarily on the rainfall triggering values. With the goal of an automated near real-time landslide hazard forecast that will eventually be promptly available online to the general public, the challenges of precipitation forecast data conversion and transfer between two servers, continuous forecast model development and serving the intermediate forecast results on the web were dealt with. The project set up a challenging task, to model the landslide hazard through time for the whole of Slovenia at a coarser scale and to model the same hazard for selected municipalities at a more detailed scale. The results and lessons learned will be presented in this paper.

Marko Komac, Jasna Šinigoj, Mateja Jemec Auflič

Monitoring of Critical Himalayan Landslides and Design of Preventive Measures

The entire Himalayan road network suffers extensive damage from a large number of landslides of different shapes and sizes. A large number of landslides on each highway have occurred repeatedly during every year for many decades, causing extensive risk to life of commuters, loss of revenue from direct and indirect losses and hardship for the people, thus influencing the socio-economic conditions of the region. One of the important highways of the country, which connects the north western Himalayan state of Uttarakhand to rest of the country, suffers from large numbers of such landslides. Two of the most critical landslides have been selected as pacesetter examples for investigation, monitoring and prevention. These two landslides have been monitored using a very simple system consisting of specially designed grooved steel pedestals, total station and DGPS (Differential Global Positioning System). The results of monitoring have encouraged utilising the same system for other Himalayan landslides of a recurring nature instead of investing in heavy-duty, costly and sophisticated instrumentation. This paper gives a detailed account of two landslides and the monitoring processes followed in a scheme of remedial measures for their long-term prevention.

Kishor Kumar, Pulikanti Subramanya Prasad, Anil Kathait, Indervir Negi

Geotechnologies for Surveys and Catastrophic Events of Rio de Janeiro Geological Survey: A Case Study

Automatic collection of field data enhances task speed and reduces the number of database input errors. The Geological Survey of Rio de Janeiro (DRM-RJ) has accumulated a large volume of information regarding mass movements in the state during recent years. A huge volume of surveys are requested by the Municipal and State Civil Defenses, generating an even larger amount of reports, photographs, sketches and other documents associated with these field activities every year. In recent years, the volume has significantly increased as a result of major disasters that occurred in the state (in Angra dos Reis, the Morro do Bumba in Niterói and a “Megadisaster” in Mountain Region) which demanded thousands of surveys. Resulting from technical cooperation between the DRM-RJ, State University of Rio de Janeiro, Federal University of Rio de Janeiro and the Federal Rural University of Rio de Janeiro, a data management system related to the geological risk of the Rio de Janeiro State was developed to support field teams and bring more practicality and organization during field assessment activities. The system consists of the assemblage of a georeferenced database to organize field-collected data related to mass movement assessments. The GIS VICON/SAGA—Vigilance and Control (

http://www.viconsaga.com.br

) was designated to support this database. It provides interfaces for data collection, querying, filtering, and report and map generation. The database was structured to store the event location, measure susceptible or affected areas, retrieve information such as number of people affected or killed, and buildings affected or destroyed by mass movements. GIS brings two specific interfaces for data input: from a PC, using web browsers or from the field, using mobile devices, on an Android OS application. For information retrieving, some interfaces were developed, such as a query system for alphanumeric-tabular reports and for other spatial query procedures for map generation.

Tiago Marino, Francisco Dourado, Claudio Amaral, Jorge Xavier-da-Silva

Automated Inclinometer Monitoring Based on Micro Electro-Mechanical System Technology: Applications and Verification

The paper illustrates the efficiency of a novel inclinometer device by comparing results obtained from some prototypes installed in three landslides and those derived from classic inclinometers. The new device, called Modular Underground Monitoring System (MUMS) is intended to be applied for natural and artificial slope deformation monitoring and landslides dynamics control, assessment and forecasting. The MUMS instrumentation was developed from the idea of replacing the standard measurement procedure by locating nodes at known distances along a connecting cable placed within a vertical borehole. Each node measures its local orientation (related to the National Elevation Dataset (NED)) by means of a micro electro-mechanical system (MEMS) formed by a 3D digital linear acceleration sensor and a 3D magnetic sensor. This allows us to determine the direction cosines of the borehole axis in each node and calculate its 3D shape and deformation along the whole borehole. This paper compares the classic instruments and the new MUMS device, with evidence of the advantages of measurement automation and economy in the use of the proposed device, which could also be equipped with other electronic instruments that would allow the measurement of other interesting physical quantities (i.e. pore pressure, temperature, stresses etc.) together with displacement components. The comparison is carried out through the examination of few installation in various types of landslides, with particular attention to the accuracy and repeatability of the measurements that are automatically made.

Andrea Segalini, Luca Chiapponi, Benedetta Pastarini, Corrado Carini

Energy Demodulation-Based All-Fiber Warning System for Landslides

In this paper, a new landslide warning technology, called the energy demodulation-based all-fiber warning system, is introduced. The system can measure the signal of energy change in fiber caused by micro-bending or breakage associated with the displacement of a landslide, and sends alarms at once when the signal intensity in the fiber weakens to a defined threshold. Compared with conventional monitoring technologies, this technology has many unique advantages, such as graded alarming, real-time response, remote monitoring, low cost, and a passive optical network. It is a very convenient and applicable landslide warning system. At present time this system has been developed and used in landslide warning in China.

Xing Wang, Guangqing Wei, Bin Shi, Fenggao Xu, Hengjin Tong

Evaluation of ‘Wig-Wag’ Landslide Warning Signs

This paper presents technical and perceptual evaluations of a novel form of landslide warning road sign. The signs, known as ‘wig-wags,’ incorporate a standard rockfall/landslide red warning triangle, flashing lights and a sub-plate that warns of ‘higher risk when lights flash’ (i.e., during periods of high rainfall) and have been trialled at an important debris-flow site in Scotland. It is broadly concluded that the trial has had a satisfactory technical outcome, albeit that the rainfall triggers used to activate the signs need further development. The results of the perceptual evaluation indicate that, in general, desired driver behaviours are promoted by the use of the signs.

Mike G. Winter, Neale Kinnear, Barbara Shearer, Louise Lloyd, Shaun Helman

Latest Developments of Hong Kong’s Landslip Warning System

The Geotechnical Engineering Office (GEO) has been operating, in conjunction with the Hong Kong Observatory (HKO), a territory-wide Landslip Warning System for over 35 years. The objective of the System is to alert the general public of possible landslide risks during periods of heavy rainfall. The GEO operates an extensive network of automatic raingauges which provides real-time rainfall information for use in the Landslip Warning System. Over the years, various measures have been implemented to enhance the efficiency and reliability of the raingauge system. Rainfall-landslide correlation models, which support the algorithm of the Landslip Warning System, have recently been updated to incorporate the most recent landslide and rainfall data using advanced geospatial and statistical techniques. This paper gives an overview of the major components of the Hong Kong Landslip Warning System and describes the technical basis of the System.

A. C. W. Wong, S. M. Ting, Y. K. Shiu, K. K. S. Ho

A Multi-Scaled Early Warning Method for Rainfall-Induced Mountain Hazards

The magnitude 8 (8M) earthquake (“Wenchaun earthquake”) that hit Sichuan province on May 12, 2008 highlighted the need for the development of large-scale early warning systems in the region surrounding the Longmenshan fault. Many of the deaths from this disaster were not from the earthquake itself, but from the landslides and other hazards that it caused. To this end, real-time monitoring and early warning of mountainous hazards (e.g. landslides, debris flows) are efficient non-engineering measures for disaster prevention and mitigation. Thus, to ensure effective disaster prediction and reduction within this region, a system of real-time regional and site-specific monitoring of mountainous hazards, coupled with early warning, is necessary. We propose here a multi-scaled, real-time early warning method. It combines large-scale regional hazard calculations and site-specific hazard monitoring with subsequent early warning. Real-time monitoring and early warning systems were constructed in five mountain hazard sites along the Longmenshan fault line, including three debris flow and two landslide zones. For early disaster warning, the threshold value of precipitation needed to trigger the post-earthquake mountainous hazard should be measured. However, identification of such threshold values is one of the most difficult issues for regional and site-specific mountainous hazard monitoring and early warning systems. To account for this difficulty, this study utilized a natural coseismic landslide from the Taziping Village of Hongkou County in Dujianyan City to identify the critical values and threshold parameters that resulted. After this experimental field test, the correlation of rainfall intensity with rainfall duration was calculated. The results indicated that the experimental field test was capable of identifying the threshold factors for the rainfall-induced mountain hazards.

Zong-ji Yang, Jian-ping Qiao, Dong Huang, Hong-ling Tian, Yuan-jun Jiang, Lili Shi

Laboratory Studies on Slope Stability Monitoring Using Distributed Fiber-Optic Sensing Technologies

The advances in distributed fiber optic sensing (DFOS) technologies enable automatic, remote and long-distance slope monitoring and early-warning of potential geological disasters. Compared with conventional geotechnical instruments, the fiber optic sensors have a number of advantages such as higher accuracy and repeatability, better durability, and enhanced integration capability. In this paper, the quasi-distributed Fiber Bragg Grating (FBG) and fully-distributed Brillouin Optical Time-Domain Analysis (BOTDA) sensing technologies are applied for monitoring of slope stability problems in laboratory model tests. The sensing principles and the implementation methods are introduced, followed by two case studies. The fiber optic sensors were embedded in the model slopes for strain monitoring of a soil mass during seepage and surcharge loading, respectively. The reliability of the DFOS based slope monitoring systems has been verified through the analyses of the strain monitoring results.

Hong-Hu Zhu, Bin Shi, Jun-Fan Yan, Cheng-Cheng Zhang, Jie Zhang, Zhan-Pu Song

A Landslide Monitoring and Early Warning System Using Integration of GPS, TPS and Conventional Geotechnical Monitoring Methods

An advanced comprehensive monitoring system was designed and used on the Grohovo Landslide in Croatia. Equipment selection was based on scientific requirements and consideration of possible ranges of monitored values and sensors precision. Establishment of an early warning system and defining of alarm thresholds is based on existing knowledge of the landslide behavior as well as collected comprehensive monitoring data. The focus of the early warning system establishment at Grohovo Landslide was on an effective combination of sensors (equipment fusion) with respect to detecting device malfunctions and reducing false alarms in the future. The weakest component in the Grohovo Landslide monitoring system is power supply based on solar devices, field data collecting and the data transmitting from the field PC to the control room at the University of Rijeka. This paper presents the main ideas and advances of the monitoring equipment fusion as well as weaknesses of the applied monitoring system at the Grohovo Landslide.

Željko Arbanas, Kyoji Sassa, Osamu Nagai, Vedran Jagodnik, Martina Vivoda, Sanja Dugonjić Jovančević, Josip Peranić, Kristijan Ljutić

Review of Monitoring Parameters of the Kostanjek Landslide (Zagreb, Croatia)

Since 2011, in the framework of the Croatian-Japanese SATREPS FY2008 Project, scientists have been working on the establishment of the Kostanjek landslide monitoring system in the City of Zagreb (Croatia). External triggers at Kostanjek landslide are measured with rain gauge and accelerometers. Displacements at the surface are measured by GNSS sensors and extensometers, while subsurface displacement is measured by vertical extensometers and inclinometer. Hydrological measurements consist of groundwater level measurements, discharge measurements, chemical and isotope analysis. Monitoring sensors recorded landslide reactivation due to external triggers in the winter period of 2012/2013. During the period from September 2012 to March 2013 the total cumulative precipitation was 793.7 mm and horizontal displacements were in the range of 9–20 cm. The installed monitoring sensor network proved to provide reliable data for the establishment of relations between landslide causal factors and landslide displacement rates aimed at establishing threshold values for early warning system.

Martin Krkač, Snježana Mihalić Arbanas, Željko Arbanas, Sanja Bernat, Kristijan Špehar, Naoki Watanabe, Osamu Nagai, Kyoji Sassa, Hideaki Marui, Gen Furuya, Chunxiang Wang, Josip Rubinić, Koji Matsunami

Risk Assessment

Frontmatter

Introduction: Risk Assessment

Landslides can result in enormous casualties and huge economic losses in mountainous regions. In recent years, interest in landslide risk assessment has grown substantially. Landslide risk assessment aims to determine the expected degree of loss due to landslides and the expected number of fatalities, people injured, damage to property and disruption of economic activity. This session addresses the landslide risk assessment, to establish criteria for ranking risk posed by different types of mass movements, to quantify the impact that mass movements have on population, structures and infrastructures, and to enhance strategies for avoiding or mitigating landslide risk.

Huabin Wang, Rejean Couture, Cees Van Westen

Site Selection Study for Hazardous Waste Based on Fuzzy Comprehensive Evaluation Method

This paper takes sites engineering geological environmental conditions as the main line. On the basis of full data collection, this paper chooses natural and geographical factors, geological structure, lithology, surface water system, hydro-geological conditions, and the distribution of geological disasters as index. According to defined index system and index weight defined by experts, fuzzy mathematics method is used to establish the mathematics models of the three sites. By calculation and analysis, the 3# site is the best as solid waste disposal center site in Chengdu, which can provide references for site selection of hazardous solid waste in mountainous cities.

Jiang Bing, Wei Yunjie, Xu Mo, Han Caiyi

Research of Stability of an Fossil Landslide on the Urban Fringe of Metropolitan Region in Beijing, China

This paper study an fossil landslide on the urban fringe of metropolitan Region in Beijing, China. Topographical features, lithologic condition, formation conditions, as well as the formation conditions of landslide was detailed analysis. We adopt the method of qualitative analysis and quantitative method to research the stability of the fossil landslide. The calculation results show that, under heavy rain conditions, although landslide is still in a stable state, but the safety coefficient decreased more, but the stability became stable. Detailed geotechnical investigations for evaluating the stability of the landslide are carried out in this study with due consideration for future risk. Finally, the corresponding engineering activities in the process of prevention and prevention measures are given according to our research.

Dong-hao Liu, Cheng Sun

Estimation of Direct Landslide Costs in Industrialized Countries: Challenges, Concepts, and Case Study

This paper presents a short summary of the challenges and concepts in previous landslide loss studies and introduces a methodological framework for the estimation of direct landslide costs in industrialized countries. A case study of landslide losses for federal roads in the Lower Saxon Uplands (NW Germany) exemplifies the application of this methodology in a regional setting.

Globally, the costs of landslide damage are proven to be of economic significance, but yet efforts for their systematic estimation are still rare. The evaluation of landslide costs requires the consideration of complex causalities and high spatiotemporal variability. Landslide impacts on economic systems vary as a function of their level of development, and specific methodologies are required for different geographic areas due to the difficulty of comparing widely dissimilar types of economies.

In this approach, landslide costs are spatially extrapolated from sub-regional levels after their calculation in representative case study areas. In the first step, cost survey is closely linked with methods of cost modeling, which in turn take advantage of landslide database information. The cost extrapolation to large-scale levels is realized by a landslide susceptibility model combining cost figures with indices of infrastructure exposure.

Martin Klose, Lynn Highland, Bodo Damm, Birgit Terhorst

Estimation of Landslide Impact Disaster by Discrete Element Method: Jiangping Hydropower Station, Hubei, China

An evaluation model of landslide risk is established with PFC in order to study the impact effect of landslide on existing buildings in Jiangping hydropower station, Hubei, China. The corresponding numerical parameters of parallel bonding are obtained during the calibration step, in which some biaxial compression tests are carried out. The conversions of energies among body force work, kinetic energy, strain energy, friction work and bond energy during the process of landslide motion are discussed based on the law of conservation of energy. Then the relationships among the impact energy, the geotechnical strength parameters and the outrun distance of landslide are studied. The results show that the calculated impact energy gotten from the proposed landslide model is far less than that gained from the rigid body model. The calculation of the proposed method is on the safe side. The total energy carried by the landslide is originated from the loss of potential energy. The calculated impact force has a less effect on the buildings because the dissipation of the friction energy caused by medium disintegration is neglected in the later. The weaker the degree of the medium cementation is, the greater the proportion of the friction energy dissipation is, and the smaller the corresponding proportion of landslide impact energy is. The landslide impact energy has a linear relation with the bond force between particles, and the maximum landslide impact energy decreases exponentially with the increase of the landslide horizontal movement distance. The simulation also shows that the ratio of the impact energy accounting for the total loss of potential energy in the proposed weak bond model is more than about two times of the sledge model, as well as more than about three times of the strong bond model. The proposed model is closer to the actual landslide motion process, so it has great promise in estimating the hazard of landslide on buildings.

S. N. Wang, Chong Shi, Weiya Xu, Yulong Zhang, Hailong Zhang

Assessing the Effect of Mitigation Measures on Landslide Hazard Using 2D Numerical Runout Modelling

Landslide mitigation measures are used to reduce the risk affecting mountain communities. The quantitative estimation of the change or reduction in risk, after implementing mitigation measures, requires modeling of past events and the forward prediction of possible future occurences. However, the forward-prediction of landslide hazard is subjected to uncertainties due to the lack of knowledge on some key aspects like the possible source volume that can be triggered and model parameters that determine the landslide runout. In this study, a back-analysis of a debris flow event was carried out using MassMov2D to create a set of parameter ranges for forward-predicting runouts with mitigation measures. We approached the issue of uncertainty by systematically sampling parameters from wide ranges and running hundreds of different runout scenarios. Simulations from back-analysis were compared with the forward-predicted models to determine changes in the spread and intensity of debris flows affecting elements at risk (e.g. houses and roads). This study is a first step towards a quantitative risk assessment (QRA) being carried out within the EC FP-7 funded CHANGES network (Grant Agreement No. 263953).

Haydar Y. Hussin, Roxana Ciurean, Simone Frigerio, Gianluca Marcato, Chiara Calligaris, Paola Reichenbach, Cees van Westen, Thomas Glade

Remedial Measures and Prevention Works

Frontmatter

Introduction: Remedial Measures and Prevention Works

The session “Remedial Measures and Prevention Works” deals with contributions which are focussed on the scientific background and also practical experiences. Ways of sustainable disaster management and disaster prevention will be demonstrated.

Rolf Katzenbach, Sebastian Fischer

Study of a Landslide in Dafnoula Village, Epirus Region, Greece

Landslide phenomena are very common in western Greece due to high rainfalls. The current study refers to a landslide that occurred during the winter of 2010 in the residential area of Dafnoula village. Dafnoula is located in northwestern Greece, Epirus perfecture, on a slope with an average inclination of 25°. The formation affected by the landslide was the flysch soil mantle of the Ionian geotectonic zone, whereas the bedrock remained intact. The landslide caused a wide range of damage, including the collapse of a house, a warehouse, and an artificial embankment-terrace and its concrete retaining wall. At the foot of the landslide there was a backfilling of the road below and the complete destruction of its pavement. For this study a 20 m depth borehole and five research pits were opened. A study of the fluid–solid coupling phenomenon and a slope stability analysis, with the use of the Finite Element Method was initially performed. Furthermore, a landslide analysis was carried out using a conventional Limit Equilibrium Method under the DIN Design Standards. Finally, remedial measures were proposed, including the construction of a retaining piled wall, in combination with the use of reinforced shotcrete, the partial substitution of the in situ unstable soil with crushed stone, and the construction of a drainage trench.

Michael Bellas, Georgios Voulgaridis

Seismic Damage Assessment of Gravity Retaining Walls Based on Grey Correlation and Fuzzy Mathematics

Strong earthquake shaking in the Longmen Mountain area in 2008 led to severe damage to many retaining structures. How to assess damaged retaining walls in the earthquake zone was a problem that required an urgent solution. This paper summarizes five types of retaining-wall failure modes through analysis of earthquake damage in the research area, including sliding failure, settlement failure, toppling failure, material failure, and overtopping failure. Then the factors influencing seismic safety evaluations were qualitatively analysed and classified on the basis of comprehensive principles, important principles and scientific principles. Along with the failure modes of retaining walls, we also examined the critical factors and some general factors. We took a value of 60 % damage to be a critical factor, and the general factors divided into two levels, and 10 indexes: the sliding distance, the settlement depth, the inclination angle, the number of cracks, the ratio of crack length and the retaining wall length, the ratio of crack depth and the retaining wall thickness, the crack width, the dislocation distance, the range of retaining wall collapse, and the coverage of rock and soil on the retaining wall. The seismic safety evaluation system for retaining walls was built by grey correlation analysis and fuzzy mathematic theory. Its use can allow prevention to replace repair and can aid post-earthquake recovery and reconstruction.

Zheng Da, Liang Lidan

Effectiveness of Hybrid Anchor Soil Nails in Stabilizing Slopes and Stability Assessment Based on Mechanics

Soil nailing has been a well accepted technique for stabilizing slopes. It is particularly useful when there is a limited working area, for example on slopes along highways, where the system can be installed directly in the slope without any major earthworks. The nail shaft will tie down the potential sliding segment to the interior stable ground. Nevertheless there have been many failures in this system where creep movement of the shaft results in the loss of stabilizing friction. In passive soil nails the stabilizing effect is considered to come from the shear capacity of the nail shaft and thereby the shaft demands no initial tension force. On the other hand, for active soil nail systems, despite applying a tension force to the nail shaft, the concept of stabilizing is considered exactly as for the passive system. Apparently, based on effective stress concepts, whenever the nail shaft is subjected to tension force, the weak frontal zone will be pulled against the interior stable ground and this thereby increases the effective stress along the potential failure surface. In turn, the shear strength along the surface will be increased and thereby stabilize the slope. This is a more appropriate mechanical design and will be presented in this paper. An innovation to the conventional soil nail system is the application of hybrid anchor at the free end to provide passive pressure resistance to effectively hold down the frontal supporting wall. This involves a special drilling technique for the installation of hybrid anchors. Using this technique, creep is prevented and thus the tension in the nail shaft will provide a long-lasting effective stress along the potential failure surface and thereby effectively stabilize the slope. The design of the hybrid anchor and its in situ pullout behaviour, with and without grout will be presented.

M. J. Md. Noor, M. A. Saidin, S. M. Tahir

A Vigorous Debris-Flow Incident at Al-Hada Descent and Remedial Measures

Al-Hada descent lies in the western region of Saudi Arabia; it begins at an elevation of about 2,000 m, and is characterized by sharp cliffs. The Al-Hada descent road was constructed with an elevation difference of 1,500 m between the highest and lowest heights along the road. The road alignment is intersected by 14 very steep gullies of almost 60–80°. The gullies contain large quantities of consolidated and unconsolidated mud, old levees and large rock blocks. The Al-Hada descent road was hit in April 2012 by heavy rainfall lasting almost 2 h. The rainstorm initiated 11 debris flows in steep gullies, which travelled rapidly down and hit the road with speeds of 25 m/s along the gully channel. Once the debris flow dropped from a height of about 150 m elevation and reached a less confined area at the retaining wall, it partially destroyed the gabions layer, right side gabions, and edges of the retaining walls across the gullies and overflowed them, as they received more rolling, sliding and bouncing rocks from higher steep elevations along the gully. The moving debris flows spread out, lost speed and was deposited beyond the highway descent route, and dropped to the lower side of the gully towards the valley.

The study suggests a temporary solution which is removing about 150,000 m

3

of the debris accumulation in the gully and to scale the remaining debris body to an angle of less than 35°. Another suggestion is to implement a permanent solution by constructing a number of high-capacity mesh barriers along the gully.

Bahaaeldin Sadagah

Application of Reinforced Concrete Retaining Walls for the Rehabilitation of Landslides on Roads

In this study we will analyze the use of reinforced concrete retaining walls in the case of the remediation of landslide “Potoci” on a local road in Srebrenik, in the northeastern part of Bosnia and Herzegovina. This landslide occurred on the part of the road toward the Old Town of Srebrenik and due to landsliding the road was damaged over a distance of about 60 m. Deformation of the landslide is reflected in depressions, folds and fissures on the hillside terrain and two damaged facilities, one residential building and one outbuilding (garage with storage). At this location, the drainage of rainwater is completely uncontrolled, and pours from the asphalt road down the hillside terrain. The catchment area of this site covers a considerable area. During major and long-lasting precipitation most of the water flows down the slope below the road, and part infiltrates into the soil through cracks, which has led to the emergence of the landslide, and slope and road instability. In addition, unplanned construction of residential buildings resulted in an overloading of the slopes and is an additional factor that affects the occurrence of landslides. Based on the general properties determined for the landslides and the causes and mechanisms of initiation of earth masses from an engineering-geological point of view, permanent remedial measures are proposed. These permanent measures include the application of appropriate support structures and technically suitable drainage of rainwater (surface) and underground water.

Nedim Suljić

A Simplified Analytical Model for the Design of Flexible Barriers Against Debris Flows

A debris flow is usually represented by a mixture of solid particles of various sizes and water, flowing along a laterally confined inclined channel-shaped region; debris flow protection barriers are the focus of this research. In particular the paper presents a simplified structural model of cable-like retention barriers based upon the equation of equilibrium of wires under large displacements condition. Inputting the debris flow features, the model returns restraining forces and cable stresses that can then be used for an appropriate barrier design. Some parametrical tests were performed to analyze how the impact velocity and the mass density of the debris influence the maximum tensile force and the acting load in the cables: also the energy associated with debris flow is assessed. Results are here presented and discussed.

Andrea Segalini, Roberto Brighenti, Gessica Umili

Engineering Solutions for Elimination of the Risk of Destruction of Moraine

In the upper reaches of the Kumtor River (Kyrgyztan, Inner Tien Shan), behind the young end moraine, a new lake formed at approximately 3,735 m at the turn of the twentieth century. With the feeding glacier degrading, due to climate reasons, the volume of accumulated water mass has increased (up to 70 mln cu.m by 2013). The lake’s natural retaining dam, composed of permafrost rocks with inclusions of buried ice blocks, is subject to thermokarst processes. Conditions for possible dam failure have formed and have been developing. Such a failure will lead to the creeping and sloughing of slopes of the developing washout channel and to a debris flow, which may be catastrophic for the infrastructure and tailings dump of the operating Kumtor gold mine. Based on analysis of the developing geotechnical situation and on multi-variate consideration of possible discharge routes and various construction designs of outlet works, a phased water level drawdown (water volume reduction) of the lake via a cascade of gabion structures during summer, in a route and mode as to achieve the best technical and economic execution and minimum engineering risk, has been accepted as a solution.

Eduard Zaporozhchenko, Aleksandr Butenko

Risk Reduction Strategy

Frontmatter

Introduction: Risk Reduction Strategy

Active and passive measures for reducing the risk associated with landslides are an important part of a successful landslide risk management strategy at local, regional and national levels. The papers in this session outline various strategies for landslide risk reduction. The majority of the papers focus on non-structural measures for landslide risk reduction, in particular community preparedness, public awareness campaigns and active application of land use plans. This is in line with the latest trends in risk management for natural hazards, and demonstrates that importance of involving the affected population and other stakeholders in the decision-making process for risk reduction.

Farrokh Nadim

Place-Conscious Education for Disaster Prevention in Risk-Prone Areas of Sao Paulo

This paper outlines the importance of the use of place-conscious pedagogy in non formal education courses developed to prevent accidents and disasters in hydrological at-risk areas. In the city of São Paulo, according to the Risk Area Mapping made by the “Instituto de Pesquisas Tecnológicas—IPT” (Technological Research Institute) together with São Paulo’s City Hall, São Paulo has many at-risk areas, but the major part of them are in the city’s suburb areas. With the intention of working with non structural measures, the City Hall of São Paulo offered, during 2012 and 2013, some non formal education courses for inhabitants, technicians, and people concerned with the subject. The courses were given in many places in the city with three different focuses: “Risk Perception”, “Urban and Environmental Risk: a Prevention Approach” and “Capacity for Mapping at-Risk Areas”. Those courses used the place-conscious pedagogy by presenting the physical and social problems of the local environment, and, also, through the intention of creating in the local inhabitants attitudes that could contribute in a social and environmental mode to the community where they live. The place-conscious’ notion is an important instrument to be used in those kinds of courses. Only with an enlarge knowledge of the place where they live, those at-risk area inhabitants can integrate and participate of public politics helping to chose decisions which can contribute to decrease the inhabitants vulnerability.

Erica Akemi Goto, Jefferson de Lima Picanço

Landslide Community Mapping and Public Awareness in the Region of Chichonal Volcano, Chiapas, Mexico

The Chichonal is an active volcano situated in the North of Chiapas State, in the Southeast of Mexico; 60 km to the Southeast of Villahermosa, State of Tabasco and 70 km to the Northeast of Tuxtla Gutierrez, the capital of the State of Chiapas. The region comprises important areas of eight municipalities, some of them still inhabited by Zoque indigenous population.

The last eruption of Chichonal volcano occurred in 1982. Non-consolidated volcanic deposits derived from this period of activity are very susceptible to the occurrence of landslides. Landsliding frequently takes place during the rainy season (April–October) and also are associated with floods, although high seismicity is common in the region. What is more, lithological units such as sandstones, lutites and limestones are susceptible to landsliding too.

By means of participatory cartography, and based on the communities experience, residents of the municipalities situated around the Chichonal volcano developed different general landslide hazards maps. Additionally, a landslide susceptibility map was generated by means of weights of evidence using GIS. The later, considered physical variables including geological and geomorphological features.

According to the produced map, the eastern sector is the most susceptible area for landslides since slopes are high and there is a presence of ancient landslides on limestones and lutites. In the western area, there are also some strips of landslide susceptibility on high slopes formed by sandstones and lutites. Moreover, in this same area, potential lahars can also take place along the gullies on the Chichonal volcanic edifice.

In this paper, we present the experiences of landslide community mapping in the region of Chichonal volcano that took place within the context of a series of workshops that were organised in order to raise landslides public awareness.

Guadalupe Hernández-Moreno, Ricardo J. Garnica-Peña, Irasema Alcántara-Ayala

Community-Based Rainfall Observation for Landslide Monitoring in Western Nepal

This paper discusses community-based approach applied for observing rainfall to monitor landslide probability in Bhanu village development committee (VDC), Tanahun District, Nepal. Vulnerable communities were supported with geological study to make them understand the causes of landslides. Participatory assessment was conducted to acquire information and perceptions regarding their risks, vulnerabilities, and capacity. Participatory assessment revealed that communities perceive rainfall as a major triggering factor for landslide. Literature were reviewed to reckon rainfall-based landslide probability. Historical landslide events were correlated with rainfall data to scrutinize the relationship between rainfall and landslides. Two types of rainfall measuring systems, automatic and manual, were installed in the community for rainfall observation. Both short duration-high intensity and long duration-low intensity rainfall can trigger landslide probability. Therefore, communities are monitoring rainfall for two periods: 1-h rainfall and 24-h rainfall. Based on the literature review, past landslides events and rainfall data, communities made agreement for disseminating alert message when rainfall amount surpasses either 50 mm in 1 h or 200 mm in 24 h. The rainfall data of two monsoons (2012 and 2013) showed that the rainfall amount never reached to the identified limits. Nonetheless, communities were alert and in frequent communications with rainfall monitor during the monsoon. This case study of Bhanu VDC concludes that localized rainfall observation by communities is not only important for exploring rainfall-based empirical thresholds for landslide probability but also to assess, analyse, and act to reduce the risk associated with landslide. This approach reckons the benefit that communities are empowered and self-reliant to take their own decisions. Support on scientific knowledge, however, could be the limitation after the withdrawal of external facilitation.

Yuwan Malakar

Landslide Risk Reduction in Poland: From Landslide Inventory to Improved Mitigation and Landuse Practice in Endangered Areas

Poland is moderately prone to natural hazards, yet floods and landslides are key threats resulting in major economic losses. Like floods, landslides here are generally triggered by precipitation. Landslides that occurred in the Flysch Carpathians and at their foreland in between 1997 and 2010 were widespread and particularly devastating. These disasters pointed to a vital need for an improved system of landslide data acquisition, hazard awareness building and developing mitigation measures. An initially developed landslide damage recovery programme evolved into a risk reduction strategy. Nowadays, the core is formed by the ongoing project named Landslide Counteracting System

LCS

(SOPO

in Polish

) combined with DBMS, meant to register landslides on a country-wide basis. However, the second streamline is focused on structural remediation measures that aim at maintaining stability and functioning of public infrastructure for foreseeable future conditions. For that, the task-oriented engineering geology documentation has to be approved by Polish Geological Survey with respect to reliability of landslide recognition and feasibility of proposed treatments. This provides technical credibility which was not present in years past.

Information on spatial distribution of landslides is, by law, to be considered in regional land use planning documents. To avoid unnecessary spending, municipal authorities draw upon previously experienced landslide threats and resultant damages, and create local management policies which impose restrictions on construction in landslide-prone terrains. Finally, risk reduction strategy involves landslide monitoring for warning purposes or remediation performance.

Teresa Mrozek, Izabela Laskowicz

Quantitative Multi-risk Modelling and Management Using Bayesian Networks

In many regions of the world, several natural hazards may act within the same time frame. Neglecting or underestimating interactions among different hazards may lead to underestimation of the overall risk and further to poor risk management. Implementation of effective and efficient risk management strategies requires that all relevant threats are assessed and considered. However, due to the differing characteristics of hazards, few quantitative models exist that can perform all the computations required for a complete multi-risk assessment. In this paper, a quantitative multi-risk management model using Bayesian networks (BaNMuR) is proposed, which could account for the assessment of cascading hazards, time-dependent vulnerability estimation and selection of optimal risk management strategies. The model was developed as part of the EU FP7 Collaborative Research Project MATRIX. An application example of the BaNMuR model for assessing the risk of tsunami triggered by rockslide is presented in the paper. The proposed multi-risk modelling evaluates the effect of interaction between single risks quantitatively, provides a more rational estimate of multiple risks and helps the decision-makers choose the best risk reduction strategy.

Zhongqiang Liu, Farrokh Nadim, Bjørn Vidar Vangelsten, Unni Eidsvig, Bjørn Kalsnes

Inventory and Database

Frontmatter

Introduction: Landslide Inventories and Databases

This is a short introduction to the Session B9 of the WLF3 entitled “Inventory and Database” with summarized overview of all contributions. Papers included in this part of the volume deals with landslide mapping and landslide identification techniques as well as with presentation of landslide inventories and data bases. There are examples of landslide identification and inventory development from Southern Kyrgyzstan, Mexico, Turkey and Croatia. Event and seasonal landslide inventories are presented in the form of Global Landslide Catalog and simple seasonal inventory from Croatia. National landslide databases encompass large archives of landslide data from Poland, Germany and Switzerland.

Snježana Mihalić Arbanas, Marko Komac, Candan Gokceoglu, Gabriel Legorreta Paulin

Landslide Database for the Federal Republic of Germany: A Tool for Analysis of Mass Movement Processes

This contribution deals with an initiative to develop a national landslide database for the Federal Republic of Germany. The paper highlights the structure and contents of this database and outlines its system architecture that underlies the current database transformation. With this background, the paper examines the database potential for research on landslide disaster impacts and hazard mitigation.

Due to systematic and continuous regional data compilation, the landslide database offers a differentiated data pool of more than 5,000 data sets and over 13,000 single data files. It dates back to 1137 AD and covers landslide sites throughout Germany. Besides closing an important data gap at the European level, the database has a key function in the country, as it integrates several existing landslide archives.

In seven major data blocks, the database stores information on landslide types, dimensions, and processes as well as the connection of landslides to soil and rock properties, geomorphometry, and climatic conditions. The database also includes data on land-use effects and damage impacts, disaster mitigation, and landslide costs. A useful feature is its capacity to support development of statistical data products, including time series, index and threshold values, data tables, and diagrams.

The upcoming migration to PostgreSQL/PostGIS improves data storage and geospatial data exploration. Furthermore, it enables the implementation of a WebGIS information platform for knowledge transfer.

Bodo Damm, Martin Klose

Landslide Inventory of the Eastern Part of the Gallipoli Peninsula (Canakkale, Turkey)

In Turkey, landslides cause several types of damage in addition to causalities in every year. Because of the losses caused by landslides, applications to reduce damage and losses require the knowledge of current and potential spatial distribution of mass movements, called a landslide inventory. For the present study, a comprehensive landslide inventory of a landslide-prone area in Turkey, a part of Canakkale, Gallipoli Peninsula, was prepared. A total of 211 landslides were identified and mapped; most are rotational. Employing the landslide inventory, the possible causative factors of the landslides, considering their types and dimensions are discussed.

Gulseren Dagdelenler, Hakan A. Nefeslioglu, Candan Gokceoglu

GIS-Based Integration of Heterogeneous Data for a Multi-temporal Landslide Inventory

Southern Kyrgyzstan is a region of high landslide activity that frequently endangers human lives and infrastructure. So far, precise spatio-temporal information on landslide activity has been limited, although landslide occurrence in this area has been investigated for the last 60 years by local authorities. The establishment of a comprehensive landslide inventory is a prerequisite for carrying out objective landslide hazard assessment. For this purpose, multiple sources of information about slope failures are analyzed with the goal of establishing a spatially and temporally consistent multi-temporal landslide inventory at a regional scale. In this context, the potential of satellite remote sensing and GIS based analysis is investigated. The paper describes the developed approach for multi-source landslide mapping and demonstrates its application to the Budalyk valley test site.

Darya Golovko, Sigrid Roessner, Robert Behling, Hans-Ulrich Wetzel, Hermann Kaufmann

Investigating and Managing Shallow Landslides in Switzerland

During the past 40 years, shallow landslides triggered by intensive rain fall caused damage costs of >520 million Euros in Switzerland. These landslides have been mainly associated with relatively few storm events of extreme intensity. The Swiss Federal Office of the Environment, together with partners from cantons, research institutes and private companies, systematically investigated such events with regard to the occurrence and properties of shallow landslides. Comprehensive inventories of shallow landslides were collected, e.g. in the regions of Sachseln (1997), Appenzell (2002) and Emmental (2002 and 2005), resulting in a national data base that is currently being developed. This data base of observed shallow landslides will be a key-tool for future risk management in Switzerland, e.g. as a basis to support the generation of hazard maps and early warning systems. Risk management is also promoted by ongoing focused research on the triggering of shallow landslides, which is carried out within the ETH Competence Centre Environment and Sustainability (CCES).

Josef Hess, Christian Rickli, Brian McArdell, Manfred Stähli

Global Catalog of Rainfall-Triggered Landslides for Spatial and Temporal Hazard Characterization

It is well known that extreme or prolonged rainfall is the dominant trigger of landslides; however, there remain large uncertainties in characterizing the distribution of these hazards and meteorological triggers at the global scale. We have developed a Global Landslide Catalog (GLC), available from 2007 to the present, which contains information on reported rainfall-triggered landslide events around the world using online media reports, disaster databases, etc. This database is being input into a map-based viewable interface. Three applications of this landslide database are outlined in this study. These applications include: (1) characterizing the spatial and temporal distribution of reported landslides and fatalities over the GLC record; (2) evaluating the co-occurrence of precipitation and rainfall-triggered landslides globally; and (3) calibrating and validating a regional landslide hazard algorithm for Mesoamerica.

Dalia Kirschbaum

Landslide Counteracting System (SOPO): Inventory Database of Landslides in Poland

The project named the Landslide Counteracting System (SOPO in Polish) is the national landslide inventory project and was launched in 2008. The end-users of the project are administrative bodies, environmental protection inspectorates as well as non-governmental organizations. The project, commissioned by Ministry of Environment and financed by the National Fund for Environmental Protection and Water Management, is managed by Polish Geological Institute—National Research Institute in the framework of geologic survey tasks.

Information on triggering events and landslide-related damage are compiled as attributes in documentary forms. Prior to being uploaded to the database, the collected information is verified by experts with respect to data consistency and reliability. The SOPO inventory is available via Web application (

http://osuwiska.pgi.gov.pl

) and is progressively updated. The service architecture is based on Esri ArcGIS Server and uses JavaScript API. Numerous spatial data (including vector and raster data sets) are served by Oracle DB through Esri ArcSDE. In order to improve speed, most static layers have been cached and are stored locally on servers as tiles. Dynamic data are served on demand. Users are grouped into a few roles, which allows for different levels of access to the data. Till April 2014, the database handles about 39,464 landslides, covering 1031.9 km

2

, mapped in 161 municipalities. In parallel, information on monitored landslides is stored.

Teresa Mrozek, Marcin Kułak, Dariusz Grabowski, Antoni Wójcik

Development of a Landslide Inventory for a Region in Mexico Using Very High Resolution Satellite Stereo-Images

In recent years, the analysis of stereo-pairs of Very High Resolution (VHR) satellite images has represented a valid alternative to aerial photographs for landslide recognition and mapping. The availability of images with even higher spatial resolution and improved digital visualization and analysis techniques have encouraged investigators to use satellite images to detect and map recent and old landslide features. In this paper we present the results of a landslide geomorphological inventory prepared for the municipality of Pahuatlan, Mexico, based on stereoscopic interpretation of GeoEye 1 VHR images.

A 54 km

2

study area was defined for landslide recognition. In the study area, elevations range from 450 m to 1,500 m above sea level. The study area has a mountainous terrain with deep ravines and high summits derived from orogenesis of the Sierra Madre. Mesozoic rocks, including conglomerates, shale, siltstones and limestone, outcrop in the area. The climate is temperate, with abundant precipitation all year and a mean annual rainfall of 2,500 mm. Vegetation types are rain and coniferous forest, with a high level of deforested areas also present.

According to the landslide inventory, in Pahuatlan municipality, there are 385 recent landslides, 171 old landslides and 21 very old landslides. The total landslide density is 10.5 landslides per km

2

. The area most affected by landslides was concentrated in 34 km

2

and it was measured using Double Pareto analysis. In addition, stereo-images were used to generate a very high resolution Digital Elevation Model (10 m spatial resolution).

VHR satellite images are efficient for landslide identification; they reduce the time to acquire information and allow a continuous stereo-model view without changing the set of images, although the associated costs are quite high.

Franny G. Murillo-García, Federica Fiorucci, Irasema Alcántara-Ayala

Inventory of Precipitation Triggered Landslides in the Winter of 2013 in Zagreb (Croatia, Europe)

The subject of this paper is inventory of precipitation induced landslides in Zagreb in the period of extreme weather conditions in the winter of 2013. Long-lasting heavy rainfall and a thick snow cover triggered more than 60 landslides in the hilly area of the Medvednica Mt. which belongs to the City of Zagreb. Basic data about landslide event locations, received from records of the City Office of Emergency Management (OEM), are analyzed. We present the results of preliminary temporal distribution analysis of landslide occurrence during the following extremes: cumulative monthly precipitation in January, February and March in 2013 was 130–190 % higher than the average monthly values for the period from 1862 to 2012; and cumulative precipitation for a 3-month period in 2013 has the highest value in the last 150 years. Spatial distribution analysis shows that most of the analyzed landslide events were triggered in engineering soils of Pontian age (approximately 1 landslide per 2 km

2

). Presented landslide inventory map provide a solid basis for organizing further research aimed at the analysis of landslide triggering rainfall thresholds as well as development of landslide inventory map which will depict landslide contours.

Sanja Bernat, Snježana Mihalić Arbanas, Martin Krkač

Landslide Inventory in the Area of Dubračina River Basin (Croatia)

Systematic landslide mapping was performed for an area of 9.35 km

2

of the geomorphological unit of hills in the Dubračina River Basin. Based on the visual interpretation of LiDAR imagery, supplemented by field reconnaissance mapping of damaged roads and structures, 48 landslides were identified. In this first phase of landslide inventory preparation for the area of the Dubračina River Basin, a preliminary landslide inventory map presents data on locations of all identified landslides. Three examples of identification of landslide contours are given to show different possibilities in visual interpretation of airborne LiDAR imagery.

Petra Đomlija, Sanja Bernat, Snježana Arbanas Mihalić, Čedomir Benac

Backmatter

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