ALBERT

Description: The fluctuation of the water level in a reservoir may induce various types of slope movements. Some of these movements are new, whereas others are old but reactivated. Many ancient landslide accumulations are distributed in the deep valleys of the eastern Qinghai–Tibet Plateau margin in China and will likely be reactivated after the completion of reservoirs and pose a risk to reservoirs, dams, facilities, and towns near mountainous areas. The Shuangjiaping ancient landslide, located in the Dadu River, Sichuan Province, China, is an example of this case. Since August 2010, the western part of the accumulation body has seen the gradual appearance of deformations. The Pubugou reservoir water level rises and inundates the front edge of the accumulation body, thus threatening the safety of the national highway G108 and 37 houses on it. This study is based on field work investigation, drilling work, aerial photography, and profile survey. The site-scale investigation shows that the deformation area is only a part of an ancient landslide accumulation, with an area of approximately 50.4 × 10 4  m 2 and a volume of ca. 956 × 10 4  m 3 . Boundary and deposit characteristics of landslide accumulation are specified, which could be divided into four zones, namely, zones A and C, which are an avalanche accumulation area mainly composed of large blocks with diameter ranging from 1 to 3 m (some blocks have a diameter ranging from 5 to 10 m), zone B, a residual integrated rock mass accumulation area with “fake bedrock,” and zone D, a fine material accumulation area. A conceptual model is proposed to explain the mechanism and sliding process of this ancient landslide. The model includes translational sliding, stopping and hanging in air, avalanche accumulating, and transforming. The saltation of topography, material structure, and kinematic characteristics is the evidence used to identify the ancient landslide in deeply incised mountain areas. The current activity is found to be a surficial deposit displacement, and the whole landslide accumulation is stable or quasi-stable.

Description: The initiation of debris flows is commonly attributed either to fluidization as a result of rainfall-induced landslides or to gully erosion induced by concentrated runoffs. A series of flume tests have been performed to show how the initial soil moisture influences the initiation of debris flows. At the start of each experiment, surface runoff was generated over loose granular deposits, triggering debris flows. These experimental debris flows enacted different scenarios according to the small variations among the initial soil moistures. In the loose granular deposits with initial soil moistures ranging from 1 to 5 %, most runoff water could infiltrate and trigger a landslide, which accelerated within 1 s to speed over 1 ms −1 and then transformed into a debris flow. In the same soil deposits with initial moistures 〉5 or 〈1 %, the debris flow was initiated by slow gully erosion with episodic events of damming and breaching due to small-scale landslides occurring on the side-slopes of the erosion valley. The slope failures were not triggered by positive pore pressure but by a decrease in suction due to the wetting of the soil. This suction decrease in initially unsaturated slopes explains why the transformation of these slope failures into debris flows are due not only to an increase of pore pressure leading to soil liquefaction, which is one of the expected triggering mechanisms, but also to a loss of the cohesive strength of the soil.

Description: This paper presents a methodology for constructing fragility functions to characterise slope stability under a range of catastrophic earthquakes and rainfalls. The procedures for creating fragility functions, including the first-order reliability method (FORM) and the copula-based sampling method (CBSM), are demonstrated using a selection of typical slopes. The most common failure modes are included, such as the shallow sliding of an infinite slope, circular slip surface of a homogeneous slope, and tetrahedral wedge failure in a rock slope. Owing to the proposed approach, the fragility function can be applied to quantify the failure probabilities over a range of loading conditions with ease, as these are attributed to a function, rather than a design point. The advantage of these definitions is that the uncertainties of correlated soil shear strengths can be incorporated into the reliability models. The established procedure can provide a basis for describing vulnerable behaviour of a slope under various loading conditions and geometries.

Description: Early warning systems (EWSs) rely on the capacity to forecast a dangerous event with a certain amount of advance by defining warning criteria on which the safety of the population will depend. Monitoring of landslides is facilitated by new technologies, decreasing prices and easier data processing. At the same time, predicting the onset of a rapid failure or the sudden transition from slow to rapid failure and subsequent collapse, and its consequences is challenging for scientists that must deal with uncertainties and have limited tools to do so. Furthermore, EWS and warning criteria are becoming more and more a subject of concern between technical experts, researchers, stakeholders and decision makers responsible for the activation, enforcement and approval of civil protection actions. EWSs imply also a sharing of responsibilities which is often averted by technical staff, managers of technical offices and governing institutions. We organized the First International Workshop on Warning Criteria for Active Slides (IWWCAS) to promote sharing and networking among members from specialized institutions and relevant experts of EWS. In this paper, we summarize the event to stimulate discussion and collaboration between organizations dealing with the complex task of managing hazard and risk related to active slides.

Description: Rock avalanches onto glacier surfaces, involving volumes 1 Mm 3 or more, are common in the glacier environments of NW North America. We analyse the Mount Munday rock avalanche (British Columbia) which occurred in July 1997. It involved the initial movement of 3.2 Mm 3 of granitic gneiss that underwent a high degree of fragmentation as it was emplaced on Ice Valley Glacier as a thin 2.6-km 2 debris sheet. The total height of the path was 850 m, and its length was 4,163 m yielding a fahrböschung of 10°, suggestive of a long runout in relation to volume. Potential energy expended in the movement was calculated as 4.33 × 10 13  J and its specific energy was estimated at 5,204 J/kg. A simulation of the movement using 2D DAN-W and DAN 3D strongly supports the idea that debris sheet geometry (runout and thickness) and behaviour (velocity profile) resulted from movement on a low friction surface (glacier ice). Our analysis of the debris sheet geometry of 23 unconstrained rock avalanches on glacier surfaces in NW North America indicated that the debris sheets are distinct from those in non-glacial environments in that they are (a) longer in relation to volume and (b) more extensive in area in relation to volume. These two effects result in a very thin supra-glacial debris sheet. Using image analysis software, we found that ∼85 % of the initial source rock volume was fragmented to fragment sizes less than 4.7 m 3 in volume during emplacement, and that within the debris sheet, the highest degree of fragmentation is associated with the thinnest debris. In the emplacement of rock avalanche debris sheets on glacier surfaces, the low friction glacier surface drives debris sheet thinning through spreading, which in turn results in the fragmentation of its entire thickness. We thus propose low friction surface-driven fragmentation as a process that contributes to long runout of rock avalanches on glacier surfaces and explains their distinctive debris sheet geometry.

Description: Sliding mass of landslides highly endangered the area along travel path, especially landslides with long travel distance. It is necessary to develop an effective prediction model for preliminarily evaluating landslide travel distance so as to improve disaster prevention and relocation. This paper collected 54 landslides with 347–4,170 m travel distance triggered by the 2008 Wenchuan earthquake to discuss the effectiveness of various influential factors on landslide travel distance and obtained an empirical model for its prediction. The results revealed that rock type, sliding source volume, and slope transition angle were the predominant factors on landslide travel distance. The validity of proposed model was verified by the satisfactory agreement between observations and predictions. Therefore, this model might be practically applicable in Wenchuan earthquake area and other similar geomorphological and geological regions.

Description: An ensemble algorithm of data mining decision tree (DT)-based CHi-squared Automatic Interaction Detection (CHAID) is widely used for prediction analysis in variety of applications. CHAID as a multivariate method has an automatic classification capacity to analyze large numbers of landslide conditioning factors. Moreover, it results two or more nodes for each independent variable, where every node contains numbers of presence or absence of landslides (dependent variable). Other DT methods such as Quick, Unbiased, Efficient Statistic Tree (QUEST) and Classification and Regression Trees (CRT) are not able to produce multi branches based tree. Thus, the main objective of this paper is to use CHAID method to perform the best classification fit for each conditioning factors, then, combined it with logistic regression (LR) to find the corresponding coefficients of best fitting function that assess the optimal terminal nodes. In the first step, a landslide inventory map with 296 landslide locations were extracted from various sources over the Pohang-Kyeong Joo catchment (South Korea). Then, the inventory was randomly split into two datasets, 70 % was used for training the models, and the remaining 30 % was used for validation purpose. Thirteen landslide conditioning factors were used for the susceptibility modeling. Then, CHAID was applied and revealed that some conditioning factors such as altitude, soil drain, soil texture and TWI, as terminal nodes and reflected the best classification fit. Then, a proposed ensemble technique was applied and the interpretations of the coefficients showed that the relationship between the decision tree branch nodes distance from drain, soil drain, and TWI, respectively, leads to better consequences assessment of landslides in the current study area. The validation results showed that both success and prediction rates, 75 and 79 %, respectively. This study proved the efficiency and reliability of ensemble DT and LR model in landslide susceptibility mapping.

Description: There is a clear need for integrated research on landslide disaster risk. Landslide disasters have major impacts in developing countries due to the increasing social vulnerability of both rural and urban communities. In recent decades, landslide disasters in Latin America triggered by both precipitation and earthquakes have also increased considerably. Thus, scientific contributions based on integrated risk research are quite urgent for improving the knowledge base for reducing the vulnerability of exposed communities to landslides. Thus, there is a parallel necessity to promote capacity building for young scientists in Latin America by considering the shift of disaster paradigm to recognize the “unnaturalness” of disasters. Under such a framework, there are particular goals to be pursued including: (1) Development of landslide regional networks with a commitment for understanding risk as a socially constructed process; (2) Engagement of young scientists in integrated landslide risk research; (3) Inducing a scientific multi- and transdisciplinary approach for integrated landslide risk research; (4) Development and implementation of capacity building; (5) Contributing to the dissemination and application of common methodologies on landslide disasters investigations; and (6) Strengthening collaboration on integrated landslide disaster risk research in Latin America. In this paper, we present one of the main activities of the ICL Latin-American network in terms of capacity building carried out in 2013; to that end, the first international workshop on forensic investigations of disasters associated with landslides was held in the University of Sciences and Arts of Chiapas in the city of Tuxtla Gutierrez, Chiapas, Mexico, from June 26th to July 4th, 2013.

Description: The gently concave piedmont of the marginal slope of the Flysch Carpathians in the Czech Republic has long been considered to comprise a system of pediments or coalescent alluvial fans. However, within one of the typical sections of this piedmont, large successive landslides with long travel distances of ~2.5 km have been identified through geophysical measurements and the investigation of an extensive artificial exposure. Accelerator mass spectrometry (AMS) radiocarbon dating and pollen analysis demonstrate that the uppermost generations of landslide deposits have originated since ~56 ka BP during the warmer and more humid interpleniglacial conditions of Marine Isotope Stage 3 (MIS 3). The geomorphological evidence for landsliding during MIS 3 has almost completely disappeared from this region due to intensive periglacial processes operating during the Last Glacial Maximum and subsequent fluvial and anthropogenic processes operating during the Holocene. The considerable antiquity of the studied terrestrial landslide bodies is unique within the context of Europe. This study shows the value of re-examining landscape development using new techniques and fresh exposures.

Description: During the five rainy seasons following the 2008 Wenchuan earthquake, at least eight catastrophic events of multiple debris flows occurred in the Yinchanggou area of Baishui River basin, in southwestern China. The deposits had some serious impacts on the transportation, communication, and reconstruction activities. It indicates the start of a period with a high-frequency debris flow activities. In this paper, a detailed review is made of the latest 12 debris flow events, which occurred on 18th August 2012. Field reconnaissance and measurements, supported by a remote sensing interpretation, were conducted to reveal the locations and morphological characteristics of debris flow catchments. A total volume of 50.26 million m 3 co-seismic landslides, triggered by the Wenchuan earthquake, served as source materials for these debris flows and/or shallow landslides. Bedrocks, which were on the hanging wall of the Yingxiu-Beichuan Fault with a mean slope gradient larger than 30°, were the most susceptible for these seism-triggered failures. The volume of debris flow deposits on individual fans vary by many orders of magnitude from 2,900 to 223,500 m 3 . The huge amount of reserves of source material compared to debris flow volumes currently deposited and taking into account the relatively low morphology index values form an indication of the early stage in the development of debris flows and the immense potential for debris flow occurrence in the future. There are two patterns of debris flow initiation which can be distinguished in this study: (a) the channel initiation pattern of concentrated overland flow erosion in the channel beds and (b) the slope initiation pattern which shows the development of new landslides and a transition into debris flows during a heavy rainfall. A catastrophic debris flow in the Haihuiqiao watershed of the Yinchanggou area was selected to show in detail the mechanism of debris flow initiation as a result of intensive erosion in loose debris materials. The critical rainfall threshold in terms of daily precipitation decreased by 77 % compared to the pre-earthquake threshold. A primary rainfall intensity–duration ( ID ) threshold curve was constructed for debris flows for an early-warning system and compared with other global rainfall thresholds. The discussion is focused on the initiation mechanisms of debris flows and the assessment of the critical meteorological threshold.

Description: This paper presents a new methodology for ex post assessment of direct landslide costs for transportation infrastructures. The methodology includes tools to compile, model, and extrapolate landslide losses on different spatial scales over time. A landslide susceptibility model enables regional cost extrapolation by means of a cost figure obtained from local cost compilation for a representative case study area. On a local level, cost survey is closely linked with cost modeling, a toolset for cost estimation based on landslide databases. Cost modeling uses landslide disaster management process models (LDMMs) and cost modules to simulate and monetize cost factors for certain types of landslide damage. The landslide susceptibility model provides a regional exposure index and updates the cost figure to a cost index which describes the costs per kilometer of traffic route at risk of landslides. Both indexes enable the regionalization of local landslide losses. The methodology is applied and tested in a cost assessment for highways in the Lower Saxon Uplands, NW Germany, in the period 1980 to 2010. In this 7,400-km 2 large mountain region, 77 km of highway is located in landslide hazard area. Annual average costs of US$52,000 per km of highway at risk of landslides are identified as cost index for a local case study area. The cost extrapolation results in annual average costs for highways in the Lower Saxon Uplands of US$4.02 million. This test application as well as a validation of selected modeling tools verifies the functionality of this methodology.

Description: Massive rock avalanches form some of the largest landslide deposits on Earth and are major geohazards in high-relief mountains. This work reinterprets a previously reported glacial deposit in the Alai Valley of Kyrgyzstan as the result of an extremely long-runout, probably coseismic, rock avalanche from the Komansu River catchment. Total runout of the rock avalanche is ~28 km, making it one of the longest-runout subaerial non-volcanic rock avalanches thus far identified on Earth. This runout length appears to require a rock volume of ~20 km 3 ; however, the likely source zone in the Trans Alai range likely contained just ~4 km 3 of rock, and presently, the deposit has a volume of only 3–5 km 3 ; a pure rock avalanche volume of 〉10 km 3 is therefore impossible, so the event was much more mobile than most non-volcanic rock avalanches. Explaining this exceptional mobility is crucial for present-day hazard analysis. There is unequivocal sedimentary evidence for intense basal fragmentation, and the deposit in the Alai Valley has prominent hummocks; these indicate a rock avalanche rather than a rock-ice avalanche origin. The event occurred 5,000–11,000 yr B.P., after the region’s glaciers had begun retreating, implying that supraglacial runout was limited. Current volume—runout relationships suggest a maximum runout of ~10 km for a 4-km 3 rock avalanche. Volcanic debris avalanches, however, are more mobile than non-volcanic rock avalanches due to their much higher source water content; a rock avalanche containing a similarly high water content would require a volume of about 8 km 3 to explain the extreme runout of the Komansu event. Rock and debris avalanches can entrain large amounts of material during runout, with some doubling their initial volume. The best current explanation of the Komansu rock avalanche thus involves an initial failure of ~4 km 3 of rock debris, with high water content probably deriving from large glaciers on the edifice that subsequently entrained ~4 km 3 of valley material together with further glacial ice, resulting in a total runout of 28 km. It is as yet unclear whether glacial retreat has rendered a present-day repetition of such an event impossible.

Description: The Son Poc rockfall took place on the 6th of March 2013 in the municipality of Bunyola, on the southern side of the Tramuntana Range (Mallorca) and after a rainy and cold period on the region. A volume of rock of 4.000 m 3 was detached from the cliff crowning the peak falling down by toppling. The impact of the boulder caused its fragmentation, and numerous boulders bounced and rolled downslope with volumes from 1 to 35 m 3 , following two trajectories: southwest (SW) and southeast (SE). The SE trajectory, with a larger runout (376 m), reached an urban area, where some of the boulders hit the roofs and walls of nearby houses, stopping others in their gardening areas. Fortunately, no fatalities occurred despite of the presence of some people at that moment, but the event caused great concern in a region which lives from and for tourism. The Son Poc rockfall has been simulated using RocPro3D software which uses GIS technology to produce 3D rockfall trajectories lines, estimated velocity and energy of falling blocks, as well as bounce heights, impacts, and stopping points. The results are in agreement with field observations and with a very good accuracy between real and modeled outcomes.

Description: Permafrost decline, observed in the last few decades as a result of climate change, causes an activation of cryogenic landslide processes. This study on Olkhon Island in Lake Baikal (Eastern Siberia), located within the discontinuous permafrost zone, was aimed to determine how strongly the landslide forms found there are associated with climatic conditions and if they can react to climate change. It was also important to identify which type of landslides in this area is the most sensitive indicator of the observed changes and to what extent they can react to them. For this purpose, landslides were identified, and their morphology, geological structure, and thermal parameters were assessed. The results show that the key process is the increase in thickness of the active layer, partly due to the presence of Miocene lake clays and changes in water level in Lake Baikal.

Description: This paper focuses on characteristics of debris flows from the lower part of the Lotru River basin (South Carpathians, Romania). The damage produced by these debris flows has included burial of agricultural land, roads covered by debris flows, and even the obstruction of the Lotru River. Simple statistical analysis has been used to emphasize the characteristics of the debris flow sites. The collected data show that heavy rainfall is the main triggering mechanism of debris flow events in the Lotru hydrographic basin. The daily rainfall data for this region show that important debris flow events generally occur when rainfall exceeds 40 mm in 24 h, while rainfall levels between 25 and 40 mm in 24 h result in hyperconcentrated flows. For 11 of 14 studied debris flow sites, the fan area is greater than the source area, probably due to the thickness of the regolith, which is up to 5–10 m deep. Both source area and deposition area are very dynamic. The retreat rate calculated for five debris flow sites ranges from 5 to 30 m in 30 years (from 1975 to 2005). Channel cross section measurements on one of the debris flows show that velocity values vary from 1.31 to 2.64 m/s; corresponding discharge values vary from 4 to 10.03 m 3 /s.

Description: Existence of soil pipes is reported in many collapsed slopes indicating their influences on landslide initiation. Flume model tests with different soil pipe configurations, (a) no pipe, (b) closed pipe and (c) open pipe, were conducted to understand the influence of soil pipes on slope stability during rainfall. Porewater pressures, discharges through the soil pipe and seepage from the slope end were recorded. Open pipe works as a hillslope drainage and reduces the porewater pressure of an entire slope, but if blocked, porewater pressure close to the lower end of pipe rises up rapidly, leading to immediate soil mass movement. Average hillslope saturation at the time of failure in a hillslope with “initially open but later blocked” pipe is lower than that in other cases. Discharge measurement shows that soil pipe even if ended within the hillslope, increases hillslope discharge. In all the three cases of experiments, shallow retrogressive sliding occurred. However, backward progress is faster in the hillslope without soil pipe because of more uniform distribution of moisture throughout the slope than the other two cases. The simple numerical analysis developed is able to predict the timing of the first crack for piped and no-piped hillslope.

Description: A debris-flow hazard assessment was conducted for the Medano Creek drainage basin, at Great Sand Dunes National Park and Preserve, following the 2,400  ha Medano Fire in 2010. Debris-flow probability and volume predictions were made using empirical regression models. Model parameters include burn severity, rainfall intensity, topographic characteristics, and soil properties. Model results provided park resource managers with information on potential sub-basin-specific hazards to park visitors, roads, and campsites. Monitoring of the first significant rainfall events following the fire and the resulting debris-flow responses provided means for model validation. Of the three probability models utilized, two predicted high probability of debris-flow occurrence for all sub-basins that produced debris flows, with numerous false positives, while the third failed to predict high probability in any of the sub-basins. The volume model predicted volumes within approximately one order of magnitude higher than those measured.

Description: This paper illustrates the quantitative estimation of specific risk (i.e., the product of hazard and vulnerability) for 39 buildings located upon the Ancona landslide based on the characterization of landslide kinematics presented in a companion paper. Hazard is quantified based on intensity, intended as the damaging potential of the kinetic and/or geometric attributes of the landslide, and is expressed in terms of expected exceedance of preset cumulative displacement thresholds for a set of five reference time intervals, ranging from 1 to 100 years. The estimation of hazard relies sequentially on (1) Monte Carlo simulation of displacement series, with sampling distributions of average yearly displacement defined on the basis of the statistical processing of inclinometer and radar interferometer data; and (2) the subsequent spatialization of displacement using radial basis interpolation as described in the companion paper. The vulnerability of the set of buildings relies on a quantitative model in which vulnerability is a function of landslide intensity and the resilience of the buildings. Resilience is a function of a set of indicators including structural type, age, and foundation type and is temporally variable due to the progressive structural degradation. Hazard, vulnerability, and specific risk are estimated for the set of five aforementioned reference time intervals. The magnitude and temporal dependence of hazard, vulnerability, and specific risk are assessed critically.

Description: The rehabilitation construction in the reservoir area of Xiangjiaba hydropower station in Southwest China has caused many landslides. A shallow progressive failure that occurred on the resettlement site of Xin’an Town of Pingshan County in Sichuan Province was selected as a case study. This landslide occurred in a long and gently inclined area by slope excavation under rainfall conditions. It is about 3.0 m deep with a total length of 35 m and is composed of some subfailures. Undisturbed samples were retrieved, on which the basic properties, shear strength, expansive potential, mineral compositions, and microstructures were tested and analyzed. The results show (1) the landsliding materials belong to medium expansive soil, consisting of the clay minerals of illite–smectite (I/S) and chlorite–smectite (C/S); (2) shear strength of the soil is sensitive to water, which greatly decreases once saturated; and (3) many fractures and relatively large pores are developed in the soils. Back analysis of the landslide shows that the shear strength at failure is less than the residual shear strength obtained from lab tests, indicating that some processes contributing to the slope failure could not be reflected by the shear box test. Based on the above analysis, the progressive process of the slope failure was interpreted, and it is inferred that the rainfall entered into the slope mainly through fractures and relatively large pores in the soil. It caused not only the great decrease in soil strength but also the swelling trend. The latter one would lead to growth, interaction, and coalescence of the fractures. Soon after, these fractures formed the shear planes (zones), which further decreased the resistance of the landslide. Under these favorable conditions, the slope excavation directly triggered the failure.

Description: Hummocks are topographic features of large landslides and rockslide-debris avalanches common in volcanic settings. We use scaled analog models to study hummock formation and explore their importance in understanding landslide kinematics and dynamics. The models are designed to replicate large-scale volcanic collapses but are relevant also to non-volcanic settings. We characterize hummocks in terms of their evolution, spatial distribution, and internal structure from slide initiation to final arrest. Hummocks initially form by extensional faulting as a landslide begins to move. During motion, individual large blocks develop and spread, creating an initial distribution, with small hummocks at the landslide front and larger ones at the back. As the mass spreads, hummocks can get wider but may decrease in height, break up, or merge to form bigger and long anticlinal hummocks when confined. Hummock size depends on their position in the initial mass, modified by subsequent breakup or coalescence. A hummock has normal faults that flatten into low-angle detachments and merge with a basal shear zone. In areas of transverse movement within a landslide, elongate hummocks develop between strike–slip flower structures. All the model structures are consistent with field observations and suggest a general brittle-slide emplacement for most landslide avalanches. Absence of hummocks and fault-like features in the deposit may imply a more fluidal flow of emplacement or very low cohesion of lithologies. Hummocks can be used as kinematic indicators to indicate landslide evolution and reconstruct initial failures and provide a framework with which to study emplacement dynamics.

Description: This paper proposes a hydro-geomechanical finite element model to reproduce the kinematic behaviour of large slow landslides. The interaction between solid skeleton and pore fluids is modelled with a time dependent u – p w formulation and a groundwater model that takes into account recorded daily rainfall intensity. A viscoplastic constitutive model based on Perzyna’s theory is applied to reproduce soil viscous behaviour and the delayed creep deformation. The proposed model is applied to Portalet landslide (Central Spanish Pyrenees). This is an active paleo-landslide that has been reactivated by the construction of a parking area at the toe of the slope. The stability analysis reveals that, after the constructive solutions were undertaken, the slope is in a limit equilibrium situation. Nevertheless, time-dependent analysis reproduces the nearly constant strain rate (secondary creep) and the acceleration/deceleration of the moving mass due to hydrological changes. Overall, the model reproduces a 2-m displacement in the past 8  years that coincides with in situ monitoring data. The proposed model is useful for short- and mid-term predictions of secondary creep. However, long-time predictions remain uncertain, stability depends strongly on the position of the water table depth and new failures during tertiary creep due to soil temporal microstructural degradation are difficult to calibrate.

Description: Dam-breaches that cause outburst floods may induce downstream hazards. Because landslide dams can breach soon after they are formed, it is critical to assess the stability quickly to enable prompt action. However, dam geometry, an essential component of hazard evaluation, is not available in most cases. Our research proposes a procedure that utilizes post-landslide orthorectified remote sensing images and the pre-landslide Digital Terrain Model in the Geographic Information System to estimate the geometry of a particular dam. The procedure includes the following three modules: (1) the selection of the reference points on the dam and lake boundaries, (2) the interpolation of the dam-crest elevation, and (3) the estimation of dam-geometry parameters (i.e., the height, length, and width), the catchment area, the volumes of barrier lake and landslides dam. This procedure is demonstrated through a case study of the Namasha Landslide Dam in Taiwan. It was shown the dam-surface elevation estimated from the proposed procedure can approximate the elevation derived from profile leveling after the formation of the landslide dam. Thus, it is feasible to assess the critical parameters required for the landslide dam hazard assessment rapidly once the ortho-photo data are available. The proposed procedure is useful for quick and efficient decision making regarding hazard mitigation.

Description: The primary objective of this paper is to present a semiautomatic procedure that, integrated with traditional methods, can be useful for a rapid definition of rock fall susceptibility scenarios with the purpose of civil protection. Due to its morphology (steep slopes and narrow valleys), regional seismicity, and rock mass characteristics, the Nera Valley (Valnerina, Umbria Region, Italy) is characterized by high rock fall risk. With the aim of covering a wide range of features and investigating the main advantages and drawbacks of the proposed approach, data collection (terrestrial laser scanning (TLS) and geomechanical surveys) was carried out at three different slopes. Detailed three-dimensional (3D) models were created to reconstruct the shape and volume of the most unstable blocks, to define the position of the main rock fall source areas, and to precisely distinguish the outcropping materials and the position of the elements at risk for reliable runout analyses. The proposed approach can be useful in supporting proper maintenance and land management programs both in ordinary and in emergency circumstances.

Description: We present a new approach for mapping open cracks and tension fractures within rock slope instabilities and rock cliffs, which resides in high-resolution ground-based and airborne infrared thermography (IRT). The method is restricted to cold seasons, and its utility is demonstrated through three examples from the Flysch Belt of the Outer West Carpathians (rockslides at Kopce Hill and Mt. Kněhyně) and from the Northern Calcareous Alps (deep-seated gravitational slope deformations in Gschliefgraben/Mt. Traunstein). The approach is based on a contrast between temperatures deep within the rock mass, which at a depth of few meters represent local mean annual values, and winter-time temperatures of the ground surface. In winter, warmer, buoyant air from depth rises to the ground surface through open cracks and joints, and the temperature contrast can be detected by IRT. Our test survey was conducted in the beginning of February 2012, in order to achieve the best contrast between temperatures around open tension cracks and the adjacent ground. For temperature sensing, we used a FLIR B360 thermal camera; for airborne surveys in the ambient air, temperatures at the time of our surveys ranged from approximately −19 to −7 °C. IRT results conclusively revealed the presence of open cracks, loosened rock zones, and pseudo-karst caves over a distance sometimes greater than 1 km. The IRT approach proved useful for rapidly assessing the distribution of open cracks and tension fractures, key information required for assessing rockfall and rockslide hazard.

Description: In the last 15 years, a series of catastrophic flowslides involving pyroclastic unsaturated soils has caused severe damage and a number of fatalities in the Campania region (southern Italy), where flowslides occur within the pyroclastic cover resting on the limestone massif. Rainwater infiltration is considered to be the triggering mechanism that leads to slope failure by reducing matric suction in unsaturated soils, hence reducing its shear strength. Therefore, knowledge of the groundwater regime is an important factor for slope stability evaluation as well as for predicting slope conditions prone to landslides triggered by water infiltration. The quality of prediction can be greatly improved if observations from in situ monitoring are available. This paper describes the results of an ongoing experimental research project on flowslides based on monitoring a test site in a typical geological environment in western Campania. The site was selected to carry out extensive laboratory and in situ testing. The test programme consisted of field monitoring of climatic conditions, matric suction and volumetric water content. The instrumentation and measuring techniques used in this research are systematically described to provide an example of good practice for use at other sites with similar features. With the use of the collected data, the seasonal fluctuations of the hydraulic regime in the subsoil may be observed and the critical periods for flowslide triggering identified. Measurements of matric suction from the test site are interpreted and directions of groundwater flow vectors in the subsoil are shown. Moreover, once the current state of the subsoil is known, slope stability conditions can be calculated using a simple infinite slope model that would provide continuously updated information on the current slope safety level.

Description: Development of landslide inventories based on remote sensing techniques has become one of the main tools in assessment of hazards and risk. Among those techniques, visual and automatic and semi-automatic analysis of high- and very high-resolution (VHR) satellite images, or a combination of these, has recently been considered as a promising way to identify and map landslides at local and regional scales. In this context, a landslide inventory for the municipality of Pahuatlán, Puebla, in central Mexico was prepared by combining three techniques: (1) visual analysis of stereoscopic pairs of VHR satellite images (GeoEye-1), (2) visual analysis of monoscopic VHR satellite images (SPOT 5 and Google Earth images), and (3) field surveying. In this paper, particular attention is given to landslide identification and mapping based on the GeoEye-1 stereo-pairs. Additionally, as a preliminary step in the use of VHR imagery, a general review is presented of the available VHR satellite images, software and hardware that can be useful for digital mapping of landslides. The landslide inventory included a total of 577 landslides, corresponding to an average density of 10.5 landslides per km 2 . Of these, 385 were classified as recent, 171 as old, and 21 as very old, regardless of state of activity. The total mapped area was 54.9 km 2 ; 57.7 % of it had been affected by landsliding. The mean area occupied by recent landslides was of the order of 1,066 m 2 ; for old landslides, it was 82,559 m 2 and for very old landslides 1,173,952 m 2 . Debris flows were the most frequent type of movement (217), followed by 167 translational slides, 97 complex movements, 79 rotational slides, and 17 falls and topples. The cost–benefit relationships of a number of these techniques remain debatable because of the high cost of some of the VHR images and the related software and hardware. However, the appearance of new satellite sensors is likely to generate market competence, so this type of image will probably be available at a much lower cost in the near future. Additionally, it is important to consider that the use of several stereo-high-resolution images involves no cost, as downloading high-resolution images from Google Earth, using Google Earth Pro is currently available. The relative rapidity of these techniques can be highly valuable after a regional landslide disaster has occurred, since damage to roads and infrastructure usually prevents the rapid and accurate evaluation of the impact of landsliding. Most importantly, these techniques can be of great value for hazard evaluation of potentially unstable inhabited slopes.

Description: In this work we analyse the performance of advanced land observing satellite (ALOS) phased array type L-band syntetic aperture radar (PALSAR) images for mapping and monitoring of very slow landslides using conventional differential interferometry in the Tena Valley (Central Pyrenees, Spain). These results are compared with those retrieved in previous works where multi-band advanced differential interferometric synthetic aperture radar (DInSAR) analysis was performed for the same area using PSI techniques. The study area is largely underlain by slates (ca. 80 %) where large deep-seated very slow earth flows are dominant. The results reveal that DInSAR analysis is able to measure displacements of landslides with a greater spatial coverage than PSI analysis, but for a lower amount of them (nine against 51). Overall, the combination of the DInSAR and multi-band PSI analysis permitted to map and monitor 68 % of the landslides in Tena Valley. From this amount, 63 landslides are considered as active. The main advantage of DInSAR with respect to PSI analysis is the capability to detect faster movements (up to 145 cm year −1 ) derived from the 46 days interferograms. That is the case of Sextas and La Selva landslides where an acceleration of the moving mass was measured after intense rainfall periods producing major damages to linear infrastructures. The combination of measured displacement from ALOS interferograms, with the observed damages on the A-136 road, was useful to assess the potential damage that could cause these slow movements. In general, it is demonstrated that even though PSI analysis provides a better performance in terms of landslide mapping, L-band DInSAR analysis provides an added value for landslide hazard assessment through radar remote sensing. For this reason it is necessary to encourage the launch of new satellite missions similar to ALOS PALSAR that could operate with shorter revisiting time periods.

Description: Bedding planes are a known factor that controls the type, abundance and pattern of landslides. Where layered rocks crop out, the geometrical relationships between the attitude of the bedding and the geometry of the terrain is crucial to understand landslide phenomena. Obtaining information on bedding attitude for large areas through field surveys is time-consuming, and resource intensive, hampering the possibility of quantitative investigations on the control of bedding planes on landslides. We propose a GIS-based method to extract information on bedding planes from the analysis of information captured through the visual interpretation of stereoscopic aerial photographs and a digital representation of the terrain. We tested the method in the Collazone study area, Umbria, Central Italy, where we used spatially distributed information on beddings and terrain information obtained from a 10 × 10-m DEM to determine morpho-structural domains. We exploited the morpho-structural terrain zonation, in combination with landslide information for the same area, to investigate the role of beddings in controlling the distribution and abundance of landslides in the study area. We found that beddings condition the location and abundance of relict and deep-seated landslides, most abundant in cataclinal slopes, and do not condition significantly the shallow landslides. We expect the method to facilitate the production of maps of morpho-structural domains in layered geological environments. This will contribute to a better understanding of landslide phenomena and to foster the preparation of advanced landslide susceptibility and hazard models.

Description: The Paonia-McClure Pass area of Colorado has been recognized as a region highly susceptible to mass movement. Because of the dynamic nature of this landscape, accurate methods are needed to predict susceptibility to movement of these slopes. The area was evaluated by coupling a geographic information system (GIS) with logistic regression methods to assess susceptibility to landslides. We mapped 735 shallow landslides in the area. Seventeen factors, as predictor variables of landslides, were mapped from aerial photographs, available public data archives, ETM + satellite data, published literature, and frequent field surveys. A logistic regression model was run using landslides as the dependent factor and landslide-causing factors as independent factors (covariates). Landslide data were sampled from the landslide masses, landslide scarps, center of mass of the landslides, and center of scarp of the landslides, and an equal amount of data were collected from areas void of discernible mass movement. Models of susceptibility to landslides for each sampling technique were developed first. Second, landslides were classified as debris flows, debris slides, rock slides, and soil slides and then models of susceptibility to landslides were created for each type of landslide. The prediction accuracies of each model were compared using the Receiver Operating Characteristic (ROC) curve technique. The model, using samples from landslide scarps, has the highest prediction accuracy (85 %), and the model, using samples from landslide mass centers, has the lowest prediction accuracy (83 %) among the models developed from the four techniques of data sampling. Likewise, the model developed for debris slides has the highest prediction accuracy (92 %), and the model developed for soil slides has the lowest prediction accuracy (83 %) among the four types of landslides. Furthermore, prediction from a model developed by combining the four models of the four types of landslides (86 %) is better than the prediction from a model developed by using all landslides together (85 %).

Description: The site investigation of low-gradient slopes composed by marly rocks usually focuses on shallow slides in weathered mantling material as it is assumed that the underlying bedrock has higher strength, but deeper investigations may reveal larger, active, deep-seated movements. A typical example of this is found in Montemartano (Perugia, Central Italy). Here aerial photo interpretation and field observations indicate that active movements involve the shallower portion of the slope, formed by a very old and large landslide body extending over an area of about 0.5 km 2 . Borehole core logging and probe inclinometer monitoring reveal that the area corresponding to the deep-seated landslide is moving at a maximum rate of 70 mm/year down to a maximum depth of 40 m. A comparison of inclinometer and piezometer data indicates that the movement seasonally reactivates even when rainfall and piezometer levels are below average values and suggests that structural setting of the whole slope influences both groundwater flow and movement kinematics. This hypothesis is reinforced by seepage analyses and stability analyses yielding a mobilized shear strength close to residual strength of the clayey interbeds of the marly limestone formations. This implies that instability occurs along bedding over a large part of the slide. The importance of these phenomena in land management policy is discussed and the critical aspects of their investigation and monitoring are addressed. The reconstruction of landslide geometry/stratigraphy and geotechnical characterization of the materials is closely considered, particularly as these are complicated by the limited representativeness of field and laboratory investigations in this type of material.

Description: Debris flows represent dangerous occurrences in many parts of the world. Several disasters are documented due to this type of fast-moving landslides; therefore, natural-hazard assessment of debris flows is crucial for safety of life and property. To this aim, much current work is being directed toward developing geotechnical-hydraulic models for the evaluation of debris flow susceptibility. A common base for such current models is parameterization of background predisposing and triggering factors such as inherent characteristics of geo-materials, topography, landscape and vegetation cover, rainfall regime, human activities, etc. which influence the occurrence of these processes on slopes. The same factors are also taken into account in soil erosion prediction models. Consequently, it seems worth investigating the effectiveness of the soil erosion index as debris flows susceptibility indicator. To this aim, a logistic regression analysis was carried out between the erosion index assessed by means of the Revised Universal Soil Loss Equation (RUSLE) model and the inventory of debris flows that have occurred in an area in Sicily (Southern Italy). Model assumptions were verified and validated by means of a series of statistical tools. Different possible scenarios were also evaluated by considering hypothetical changes in soil erosion rate under different rain erosivity conditions. Notwithstanding the rough approximations in model data collection, the outcomes appear encouraging.

Description: In slopes formed by tectonized clayey turbidites, the soil fissuring recurrently influences the hydro-mechanical soil properties, determining an impoverishment in strength and an increase in permeability of the slope that make them predisposing factors of landsliding. This paper presents three case histories of slopes within tectonized clayey turbidites that are representative of several others in the Southern Apennines and, more widely, in the southern Mediterranean. The paper reports a novel attempt to connect tightly the slope geomorphological and hydro-mechanical features to the slope geological history, through an introductory presentation of the geological setting and history of the chain where the slopes occur. The slopes, location of very slow landslides, have been reconstructed based upon field surveys and investigations, multi-aerial photo-interpretation, laboratory testing, monitoring and numerical modelling. Furthermore, novel is the attempt to present, all together, the behaviour of the soils involved in the three landslide case studies, in the light of the mechanical modelling approach to fissured clays recently presented in the literature.

Description: Slope–channel coupling in geomorphologically active regions represents a topic with numerous implications, from both fundamental and applied perspectives. Landsliding and erosion combine under the influence of the morphostructural and lithological, seismic, climatic, and anthropic factors, and their interaction may materialize in landslide dams, forms which are conditioning the future slope and river morphology and morphodynamics. The proper understanding of the predisposition and preparing and triggering factors in case of landslide dams could provide significant information in the risk analysis, assessment, and management. The occurrence in July 2013 of a landslide dam in the Buzău Mountains (along the Bâsca Mare river), caused by the partial reactivation of a dormant deep-seated landslide, allowed the outlining of the entire agents–forms–processes framework, offering in the meantime the background data for a future multi-hazard assessment. Since the Vrancea seismic region (area that comprises the Curvature Carpathians of Romania) represents one of Europe’s most slope/channel/seismically active regions, the case–study offers important insight information that allows in the meantime the analysis of multi-hazard at a regional scale.

Description: The Island of Ischia is a densely populated, active volcanic island located in the Tyrrhenian Sea, approximately 30 km WSW from the city of Naples in Southern Italy. The Island is a debris-flow prone area due to its steep slopes covered by loose volcanic lithologies, and the whole territory is vulnerable to such phenomena due to an unregulated urbanization. On April 30th 2006, following several hours of rainfall, four soil slips were triggered on the slopes of Mt. Vezzi (about 400 m a.s.l.) in the SE portion of the island. The soil slips changed quickly into debris flows that reached the inhabited at the foot of the hill. In spite of their limited size, the landslides caused four victims and destroyed several buildings, forcing the evacuation of 250 inhabitants. This paper presents the analysis of the triggering and propagation phase of the phenomena. In particular, to model the triggering conditions, a finite element analysis was used to reconstruct the fluctuations in pore water pressure during the storm in transient conditions. The limit equilibrium (Morgenstern and Price, 1965 ) slope-stability method was then applied using the temporal pore water pressure distributions derived from the seepage analysis. The dynamic modeling of the propagation phase was carried out by means of two dynamic codes DAN-W and FLO2D, with the aim of evaluating the residual hazard linked to other potential debris flows recognized in the same area. The model calibration was based on the thickness and areal extension of the deposits, on flow velocity and runout. The results have been subsequently compared to adopt a combined approach to the modeling. Once the DAN-W and FLO2D models satisfactorily reproduced the 30th April events, the simulations were extended to a larger area, whose susceptibility to future landslide events has been determined through a detailed geomorphological survey and a following GIS analysis. Several scenarios related to these potential events were used to estimate the inundation areas, flow velocities, and deposit thicknesses.

Description: Argillaceous rocks can display a wide range of durability behavior after excavation and in cut slopes. In this paper, we propose a classification of argillaceous rocks based on their textural characteristics. Three main components of the classification scheme are the clastic framework, the fine-grained matrix, and the cementing agent. Unlike other schemes, the unlithified argillaceous sediments are included as well. The names proposed for the rocks broadly follow the existing nomenclature used in petrographic classifications. The durability of some argillaceous rock types has been assessed by taking into account a set of degradation features of the excavated slopes. It has been observed that the ratios of these textural components exert a strong control on the long-term durability of slopes.

Description: Step-path failure is a typical instable mode of rock slopes with intermittent joints. To gain deeper insight into the step-path failure mechanism, six rock slopes with different intermittent joints are studied using the 2D Particle Flow Code (PFC). Three different step-path failure modes, i.e., shear, tensile, and mixed tensile–shear failure, are observed by focusing on the crack initiation, propagation, and coalescence in the rock bridges. The cracks develop progressively in the rock bridges, which induce the intermittent joints to coalesce one by one from bottom to top under the action of gravity. The tensile cracks that often appear in the main body and at the crown are nearly vertical to the step-path failure surface. The step-path failure in a rock slope with intermittent joints can be divided into four stages in terms of both stress and crack development in the rock bridges, i.e., elastic deformation, failure of rock bridges at a lower position, progressive failure of rock bridges upward, and final block slide. Therefore, reinforcement is suggested to be applied to the lower part of the slopes. Three equations for calculating the factors of safety are derived with respect to the three failure modes, in which the degree of joint coalescence is considered.

Description: Multitemporal satellite interferometric synthetic aperture radar (InSAR) techniques can characterize line-of-sight displacements of active landslide areas with resolution (mm scale) and accuracy comparable to or higher than differential GPS, sensor network, or photogrammetry techniques. This study improves understanding of the rate of movement and the lateral extent of the active domain of a landslide complex within Salmon Falls Creek Canyon near Twin Falls, Idaho. Specifically, we were able to estimate displacement of yearly motion rates in early and late stages of the event by analyzing a collection of archived radar satellite imagery. Small baseline subset (SBAS) InSAR performed better than persistent scatterer (PS) InSAR for analyzing distributed scatterers because of its ability to capture strongly nonlinear displacement rates. In addition, comparison with GPS field measurements showed agreement with InSAR-derived displacements. Geostatistical analysis was used to describe surface and morphometric characteristics of two separate landslides within Salmon Falls Creek Canyon. Each was divided into representative geomorphologic units, and morphometric analysis focused on two key parameters: topographic texture and mean slope. Scarp units are topographically rough because of their greater relief and steep slopes, while a displaced headwall block has retained a smooth topography. Each landslide upper body has a higher topographic texture than the corresponding body unit. Both landslides display a progressive decrease in mean slope from upper body to toe to body. InSAR SBAS results showed that headwall block and transverse scarp of the landslide complex at Salmon Falls Creek Canyon had the highest mean annual velocity in the radar line-of-sight (LOS) direction. Velocity of movement in each landslide toe and body was less, signifying that LOS movement was more active in the upper reaches of the landslides, although lateral translation may have been greater in the body and toe compared to the headwall region due to the curved shape of the landside detachment surface.

Description: The purpose of this study was the analysis of life and property risks due to landslides in the Three Gorges area, China. A landslide susceptibility map was created using rough set theory and a support vector machine model. A scenario based on the past landslide frequency and magnitude was used to convert the susceptibility into quantitative hazard maps. The vulnerability was defined quantitatively as a function of landslide intensity and the resistance of at-risk elements. The elements at risk (population, buildings, lifeline engineering, and land resources) were extracted from color aerial photographs, and detailed information regarding these elements was collected via fieldwork. Reconstruction-cost and market-cost approaches were used to estimate the value of property. Quantitative risk maps were developed by integrating the value of the at-risk elements with the vulnerability and landslide hazard datasets. The resulting maps are presented on a continuous scale in which the numerical values indicate the distribution of risk, including the probability of expected economic losses in renminbi (RMB) and loss of lives per map unit for property and residents, respectively. Based on the final risk maps, it is clear that high-risk areas are located in Badong County and other towns and with transportation networks and urbanized areas with dense populations and high property values. Areas of moderate risk were primarily distributed in rural areas and cultivated lands. In addition, the maps show the low-level probability of expected losses in areas where landslide hazard control measures are present or where human activity is sparse, such as unutilized areas and forests. The resulting risk values involve uncertainties and are not precise predictions of future losses, but they may nevertheless help in identifying areas where damage is likely to be greater and where mitigation measures are warranted.

Description: In the Grande da Pipa river basin, north of Lisbon, 64 % of the total number of landslides inventoried is totally or partially included in a lithological unit composed by marl, clay, and sandstone intercalation complex that is present in 58 % of the study area. The Persistent Scatterer synthetic aperture radar interferometry technique is applied to a data set of TerraSAR-X SAR images, from April of 2010 to March of 2011, firstly to the Laje-Salema test site and further exported to the Grande da Pipa river basin. This work’s specific objectives are the following: (i) to assess the potential of the Persistent Scatterer displacement maps to the identification of new landslides/unstable areas and in the redefinition of landslide limits, (ii) to update the landslide state of activity, and (iii) to evaluate the capacity of the Persistent Scatterer deformation maps in assessing landslide susceptibility at the regional scale. Based on this approach, it was possible to increment the number of landslides and to redefine the landslide limits in the test site in 3.8 %. For 39 landslides, it was possible to update the landslide state of activity, in particular from dormant to reactivated or dormant-reactivated (23 landslides) or from stabilized to reactivated (5 landslides). Landslide susceptibility map based in Persistent Scatterer deformation rates, independently validated with a deep rotational slide map, obtained the best value of area under the curve (0.668).

Description: The paper deals with the behavior of some characteristic soft rocks found in the Iberian Peninsula. In geological terms, they belong to Tertiary basins, the Keuper period and the Jurassic-Cretacic transition. The discussion is organized around the following aspects: (a) the intact material and its brittle behavior; (b) the weathering action of atmospheric events; (c) the persistent discontinuities and scale effects; and (d) the modification of strength after failure. In all cases, instability phenomena are addressed in connection with several case histories. Regarding material brittleness and the initial stress state, two cases of first time failures are discussed. Practical implications concerning the selection of operative strength will be given. Field observations of the relevance of weathering and, also, on the rate of weathering, are given for a Weald claystone. Field observations emphasize the importance of sharp transitions between weathered and intact (or slightly weathered) levels. A recent long-term laboratory investigation on the nature of degradation will be summarized. Macroscopic variables such as stiffness and tensile strength have been found to be uniquely predicted by a degradation law in terms of the accumulated plastic deformations. Persistent discontinuities and, in particular, sedimentation planes play a dominant role to explain slope failures not related to the shallow failures, usually associated with weathered profiles. The strength of discontinuities in a Weald formation was investigated by means of tests performed at two scales. Finally, the evolution in time of residual strength induced by chemical actions, associated with groundwater flow, is highlighted in connection with actual field data of unstable slopes.

Description: In 2013, a potentially unstable jointed rock slope above a road in the Gold Coast area, Australia, partially failed after a rainfall event. In this study, the rock failure was back analyzed to evaluate the presence of key blocks through block analysis based on photogrammetry surveys. Friction angles of the joint sets at the point of failure were also investigated by means of a parametric study using a 3D distinct element method (DEM). The photogrammetry method was employed to obtain measurements of the orientation of the joint sets of the slope and the shape and size of rock blocks at the inaccessible slope. The joint roughness coefficient (JRC) obtained from the 3D photogrammetry model was utilized to estimate friction angles and the strength of the joint set. Safety factors of the rock mass were computed by both analytical and numerical approaches. Parametric analyses, using a DEM model, assessed the critical friction angle of the joint sets and also demonstrated the failure mechanism of the blocks. The result of this study indicates that the obtained safety factors are in agreement with the block analysis and the results from the numerical analysis performed by the distinct element code “3DEC.”

Description: In this work, a simple methodology is presented for processing high-resolution topographical data over wide areas. It is based on digital elevation model of differences (DEMoD) among high-resolution digital models (HRDEM) produced from light-detection and ranging (LiDAR) data. Because these qualitative approaches based on HRDEMs can be affected by errors related to misalignment between different passes of the airborne sensor and errors in classifying points, a simplified strategy was undertaken for their semi-automatic correction and supervision for analyzing geomorphological changes. Besides, it became possible to detect, delineate, and classify a total of 47 natural landslides and 50 slope-cut failures over an area of 234 km 2 on the basis of the analysis of the LiDAR products (DEMs and DEMoD) and the orthophotography imagery inspection integrated in a geographical information system (GIS). Most of the displacements detected were probably generated during the winter of 2009–2010 when a new record of cumulative rainfall was reached. The displacement rate of these movements cannot be known with precision, but the minimum velocity that can be obtained is 0.3 m/year regarding the period between the two data acquisitions carried out in November 2008 and July 2010. On the other hand, a comparison was made of the existing susceptibility maps with respect to this new inventory, which indicated greater landslide frequency in areas of moderate susceptibility levels. The influence of treating inventories at different temporal scales is discussed.

Description: Quantitative modelling of landslide hazard, as opposed to landslide susceptibility, as a function of the earthquake trigger is vital in understanding and assessing future potential exposure to landsliding. Logistic regression analysis is a method commonly used to assess susceptibility to landsliding; however, estimating probability of landslide hazard as a result of an earthquake trigger is rarely undertaken. This paper utilises a very detailed landslide inventory map and a comprehensive dataset on peak ground acceleration for the 1994 M w 6.7 Northridge earthquake event to fit a landslide hazard logistic regression model. The model demonstrates a high success rate for estimating probability of landslides as a result of earthquake shaking. Seven earthquake magnitude scenarios were simulated using the Open Source Seismic Hazard Analysis (OpenSHA) application to simulate peak ground acceleration, a covariate of landsliding, for each event. The exposure of assets such as population, housing and roads to high levels of shaking and high probabilities of landsliding was estimated for each scenario. There has been urban development in the Northridge region since 1994, leading to an increase in prospective exposure of assets to the earthquake and landslide hazards in the event of a potential future earthquake. As the earthquake scenario magnitude increases, the impact from earthquake shaking initially increases then quickly levels out, but potential losses from landslides increase at a rapid rate. The modelling approach, as well as the specific model, developed in this paper can be used to estimate landslide probabilities as a result of an earthquake event for any scenario where the peak ground acceleration variable is available.

Description: Active landslides in clay shales are widespread in Mediterranean countries. One of their characteristics is that the mobilized shear strength corresponds to the residual strength. The residual friction angle of clays depends on pore fluid composition which, in formations of marine origin, could have changed after emersion from the sea because of a number of processes, e.g., contact with rain or fresh water. This study aims at evaluating the influence of pore fluid composition and of its changes on the behaviour of Costa della Gaveta landslide, used as a case study. The natural pore fluid composition was analysed; then, the influence of such composition on the residual strength, and the effects of its variation on the shear creep behaviour were investigated. The paper shows that the natural pore fluid is a composite salt solution with variable concentration. It exhibits characteristics close to those of seawater at about 30 m depth, whereas it is very dilute close to the ground surface. Salt solutions at various concentrations and distilled water were thus used to simulate in the laboratory tests the effects of the different natural pore solutions. The results show that the residual friction angle varies significantly within the field concentration range. Moreover, exposure to distilled water causes a noticeable decrease in the residual strength during tests under constant shear displacement rate. Consistently, under constant driving shear stresses, time dependent displacements are observed, evolving with primary, secondary and tertiary creep phases, characterized, respectively, by decreasing, constant and increasing displacement rates.

Description: Extreme rainfall during 15–17 of June 2013 triggered numerous landslides and caused widespread damage and loss of life in the Bhagirathi and Alaknanda river valleys, with Kedarnath town bearing the brunt of the disaster. In this paper, we present a corroboration of observations gathered from very high resolution satellite data which indicated that two events in close succession caused damage to the Kedarnath town. While the flooding on June 16, 2013 was due to the reactivation of an old landslide that resulted in breaching of the river training wall, breaching of the moraine dammed Chorabari lake on June 17, 2013 caused further flooding and damage to the Kedarnath town. We also prepared a detailed landslide inventory using multi-temporal Resourcesat-2 images (5.8 m) acquired before and after the event in order to avoid issues related to cloud and shadow. A total of 6,013 landslides were mapped, out of which 3,472 landslides with 30.4 km 2 area were classified as new ones, 1,137 landslides with 9.1 km 2 area were classified as old ones and 1,401 landslides with 11.7 km 2 area were classified as reactivated ones. The frequency-area statistics of the mapped landslides shows near completeness of this event-based landslide inventory. The debris brought down by rivers from these landslides, particularly from the glaciated deposits in upstream areas, caused severe river bank erosion in downstream areas.

Description: A worldwide decline of mountain glaciers is occurring due to the impacts from climate warming. The retreat of mountain glaciers often leads to different kinds of geo-hazards. Serious surges triggered by glacier avalanches often pose a potential threat to the stability of dams. In this article, four different types of blocks with a constant density of about 900 kg/m 3 were used to simulate the glacier avalanches in natural conditions. By considering the raw material properties of the plate and blocks themselves, the plunging velocity of a block was calculated by a theoretical method instead of by video cameras. The effect of the slope angle, distance between the sliding block and the water surface, initial water depth, slide Froude number, geometry, and distance between the plunging point of the sliding blocks and the downstream dam was considered to study the characteristics of the pressure loads acting on the moraine dam. In addition, an empirical equation was obtained to predict the maximum pressure load acting on the dam. Pressure load on the glacier dam is only one of the crucial factors for dam safety analyses. The failure process of a moraine dam, the probable maximum discharge of outburst floods, and the transportation of sediments along the downstream valley should also be considered in future studies.

Description: Landslides are a common hazard in the highly urbanized hilly areas in Chittagong Metropolitan Area (CMA), Bangladesh. The main cause of the landslides is torrential rain in short period of time. This area experiences several landslides each year, resulting in casualties, property damage, and economic loss. Therefore, the primary objective of this research is to produce the Landslide Susceptibility Maps for CMA so that appropriate landslide disaster risk reduction strategies can be developed. In this research, three different Geographic Information System-based Multi-Criteria Decision Analysis methods—the Artificial Hierarchy Process (AHP), Weighted Linear Combination (WLC), and Ordered Weighted Average (OWA)—were applied to scientifically assess the landslide susceptible areas in CMA. Nine different thematic layers or landslide causative factors were considered. Then, seven different landslide susceptible scenarios were generated based on the three weighted overlay techniques. Later, the performances of the methods were validated using the area under the relative operating characteristic curves. The accuracies of the landslide susceptibility maps produced by the AHP, WLC_1, WLC_2, WLC_3, OWA_1, OWA_2, and OWA_3 methods were found as 89.80, 83.90, 91.10, 88.50, 90.40, 95.10, and 87.10 %, respectively. The verification results showed satisfactory agreement between the susceptibility maps produced and the existing data on the 20 historical landslide locations.

Description: The Wenchuan earthquake has caused abundance of loose materials supplies for debris flows. Many debris flows have occurred in watersheds in area beyond 20 km 2 , presenting characteristics differing from those in small watersheds. The debris flows yearly frequency decreases exponentially, and the average debris flow magnitude increases linearly with watershed size. The rainfall thresholds for debris flows in large watersheds were expressed as I  = 14.7 D −0.79 (2 h 〈  D  〈 56 h), which is considerably higher than those in small watersheds as I  = 4.4 D −0.70 (2 h 〈  D  〈 37 h). A case study is conducted in Ergou, 39.4 km 2 in area, to illustrate the formation and development processes of debris flows in large watersheds. A debris flow develops in a large watershed only when the rainfall was high enough to trigger the wide-spread failures and erosions on slope and realize the confluence in the watershed. The debris flow was supplied by the widely distributed failures dominated by rill erosions (14 in 22 sources in this case). The intermittent supplying increased the size and duration of debris flow. While the landslide dam failures provided most amounts for debris flows (57 % of the total amount), and amplified the discharge suddenly. During these processes, the debris flow velocity and density increased as well. The similar processes were observed in other large watersheds, indicating this case is representative.

Description: Integrated in a wide research assessing destabilizing and triggering factors to model cliff dynamic along the Dieppe’s shoreline in High Normandy, this study aims at testing boat-based mobile LiDAR capabilities by scanning 3D point clouds of the unstable coastal cliffs. Two acquisition campaigns were performed in September 2012 and September 2013, scanning (1) a 30-km-long shoreline and (2) the same test cliffs in different environmental conditions and device settings. The potentials of collected data for 3D modelling, change detection and landslide monitoring were afterward assessed. By scanning during favourable meteorological and marine conditions and close to the coast, mobile LiDAR devices are able to quickly scan a long shoreline with median point spacing up to 10 cm. The acquired data are then sufficiently detailed to map geomorphological features smaller than 0.5 m 2 . Furthermore, our capability to detect rockfalls and erosion deposits (〉m 3 ) is confirmed, since using the classical approach of computing differences between sequential acquisitions reveals many cliff collapses between Pourville and Quiberville and only sparse changes between Dieppe and Belleville-sur-Mer. These different change rates result from different rockfall susceptibilities. Finally, we also confirmed the capability of the boat-based mobile LiDAR technique to monitor single large changes, characterizing the Dieppe landslide geometry with two main active scarps, retrogression up to 40 m and about 100,000 m 3 of eroded materials.

Description: This paper describes a characteristic landslide model for landslides typically hosted in Neogene formations in Serbia, especially along the right banks of the Sava and Danube Rivers. It is focussed on the particular landslide Umka near Belgrade, which is a paradigm for numerous landslides in that area. Various field investigations and laboratory tests carried out in several campaigns, including 1979, 1991–1993 and 2005, underpinned the conception of a general model for this typological landslide. Additionally, a new landslide monitoring campaign started in 2010 provided supplementary data support for the model development. Landslide characteristics, sliding mechanism and material properties based on all these data are first summarised and discussed and then featured in a general model. It is assumed that the landslide is hosted in the weathered zone of grey marls and that the main sliding surface typically propagates along the contact between the fresh and weathered marls. Furthermore, the triggering is principally associated with lateral river erosion in the landslide toe, although heavy precipitation and snow melting have been witnessed to be important indirect triggers. Their correlation to the recorded displacements was difficult to determine due to complex hydrogeological relations and an isolated groundwater system, which is another common characteristic of this landslide type. Back analysis on the basis of the adopted model and the determined geotechnical parameters has been performed. The latter analysis is of particular interest because the Umka landslide is currently under consideration for a mitigation and stabilisation plan related to the construction of a new motorway route.

Description: This paper presents a case study of cliff retreat and the progressive development of talus deposits in the vicinity of the Hungtsaiping rockfall area of Taiwan. Geomorphologic analysis and physical modeling identified the types involved in cliff retreat as parallel rectilinear slope retreat transforming to central rectilinear slope retreat. Cliff retreat and talus deposition patterns in Hungtsaiping can be categorized as follows: (1) simultaneous retreat with steep slope; (2) simultaneous retreat with gentle slope; (3) central rectilinear slope retreat with steep slope; (4) central rectilinear slope retreat with gentle slope; (5) parallel rectilinear slope retreat with steep; and (6) parallel rectilinear slope retreat with gentle slope. This paper identifies the fundamental control factors associated with cliff retreat and proposes a possible scenario to explain cliff retreat and the progressive development of talus deposits in the Hungtsaiping area from 1904 to 2006.

Description: Buildings are the element of greatest concern with regard to debris flow hazard risk, and their destruction is mainly caused by the collapse of walls and reinforced concrete (RC) columns. This research classifies the failure modes of the columns in a typical beam–column-framed building based on field investigations and historical data. It also proposes the collapse mechanism for columns damaged by debris flow, with reference to their failure modes. Based on the collapse mechanism, three typical types of RC columns with different strengths, which are usually used in many mountainous areas of Western China, were selected for the damage analysis. The critical velocity of debris flow and the diameter of particles were obtained using theories of material and structural mechanics. The results showed that the critical bearing condition of columns can be indicated by the formation of plastic hinges along columns and by the shear damage in the column section. The development of plastic hinges was mainly determined by the debris flow velocity and diameter and the impact location of large boulders. The energy of viscous debris flow is much larger than that of the dilute flow, and there will be more severe damage for columns under viscous flow impact. The critical velocities for three plastic hinge collapses are about twice those of two plastic hinge collapses. If the diameter of the boulders is larger than 0.5 m, the impact force of the large boulders plays a major role in the column collapse. Otherwise, both the dynamic pressure of debris flow and the impact force of boulders are responsible for column failure. Finally, the critical condition of column failure was applied to Zhouqu’s debris flow hazard. The calculated critical velocity is consistent with the value given by field investigation, which implies that this study can be used for risk analysis and damage estimation in a debris-flow-prone area.

Description: Railways across the Canadian Cordillera have long histories of losses associated with ground hazards. The hazards most frequently reported are rockfalls, which are ubiquitous along the steep rock cuts required to accommodate the railway alignment. Several hazard control measures can be adopted in rockfall areas. However, when rockfall frequencies cannot be controlled, protective structures may be necessary to decrease rockfall-related risks to tolerable levels. Designs of protective structures require knowing rockfall trajectory heights and kinetic energies. This information is difficult to obtain even at locations where comprehensive rockfall records are kept. We present a method to calculate rockfall trajectory heights and velocities based on three-dimensional, lumped mass, rockfall simulations. Rockfall source location, model parameters and model calibration are also discussed. In this regard, the model should be calibrated against observed values of rockfall heights and velocities, and the design parameters should be validated before proceeding with the design of rockfall mitigation measures. The method is illustrated with the analysis of a section of a railway along the Canadian Cordillera. Furthermore, a probabilistic approach is adopted to calculate rockfall trajectory heights and velocities when intersecting the railway alignment. This is consistent with the natural variability of rockfall trajectories and falling block volumes. We illustrate the use of probability distributions of rockfall velocities and volumes to calculate the distribution of kinetic energy at three locations along the study section. The calculated rockfall trajectory heights are also presented in probabilistic terms and discussed. The rockfall kinetic energy distributions are used to assess the type of protective structures that could be required for further reduction of risk levels.

Description: Persistent scatterer interferometry (PSI) is capable of millimetric measurements of ground deformation phenomena occurring at radar signal reflectors (persistent scatterers, PS) that are phase coherent over a period of time. However, there are also limitations to PSI; significant phase decorrelation can occur between subsequent interferometric radar (InSAR) acquisitions in vegetated and low-density PS areas. Here, artificial amplitude- and phase-stable radar scatterers may have to be introduced. I2GPS was a Galileo project (02/2010–09/2011) that aimed to develop a novel device consisting of a compact active transponder (CAT) with an integrated global positioning system (GPS) antenna to ensure millimetric co-registration and a coherent cross-reference. The advantages are: (1) all advantages of CATs such as small size, light weight, unobtrusiveness and usability with multiple satellites and tracks; (2) absolute calibration for PSI data; (3) high sampling rate of GPS enables detection of abrupt ground motion in 3D; and (4) vertical components of the local velocity field can be derived from single-track InSAR line-of-sight displacements. A field trial was set to test the approach at a potential landslide site in Potoška planina, Slovenia to evaluate the applicability for operational monitoring of natural hazards. Preliminary results from the trial highlight some of the key considerations for operational deployments in the field. Ground motion measurements also allowed an assessment of landslide hazard at the site and demonstrated the synergies between InSAR and GPS measurements for landslide applications. InSAR and GPS measurements were compared to assess the consistency between the methods from the slope mass movement detection aspect.

Description: Chalk exposures in coastal cliff faces extend from Yorkshire to Devon in England and from Boulonnais to Normandy in France. The failure of chalk cliffs is a long-recognised hazard along parts of these coastlines; however, variation in the chalk’s lithology, stratigraphy and physical properties coupled with changing topographic relief, means that the nature of the hazard is variable. This paper is concerned with cliff failures that may lead to chalk flow resulting in catastrophic flow slide or sturzstrom-like behaviour. The paper discusses the nature of chalk flows and how they relate to other types of flow-like sturzstroms. Recently published and unpublished work is used to unify simple mechanical index properties between the French and English coastal chalks. Some well-documented studies are then re-examined, using these results and in the light of new findings on sturzstroms to show how runout is controlled by chalk porosity. Finally, a series of physical model tests are described in which some of the controls on runout of the chalk are examined.

Description: In 2008, the Wenchuan M w 7.9 earthquake triggered a large number of landslides in the Longmenshan area. Among them, the Donghekou landslide is a gigantic one, which buried four villages and one elementary school. During the Wenchuan earthquake, large accelerations, especially vertical, were produced, which should to be taken into account in the dynamic analysis of slope stability. However, the vertical acceleration, which can largely influence the acceleration component normal to the sliding surface, is often overlooked in dynamic analysis of slope stability. In this work, the initiation of the Donghekou landslide is analyzed by using Newmark’s sliding block model. Comparative analyses of conditions both with and without an acceleration component normal to the sliding surface, which is contributed mainly by the vertical acceleration, are then conducted to investigate its role in triggering the Donghekou landslide. Research results show that the initiating time of the Donghekou landslide would be earlier considering the acceleration component normal to the slide surface than without it due to larger estimated Newmark displacement. This conclusion is then verified by simulated results on the basis of DEM. It means that initiation of landslides can be influenced significantly by seismic acceleration component normal to sliding surface, especially in the area with large vertical acceleration.

Description: In Italy, rainfall-induced landslides are recurrent phenomena that cause societal and economic damage. Thus, assessing the rainfall conditions responsible for landslides is important and may contribute to reducing risk. The prediction of rainfall-induced landslides relies primarily on empirical rainfall thresholds. However, the thresholds are affected by uncertainties that limit their use in operational warning systems. A source of uncertainty lies in the characterization of the rainfall events responsible for landslides. Objective criteria for the definition of rainfall events are lacking. To overcome the problem, we propose an algorithm that reconstructs the rainfall events, identifies the rainfall conditions that have resulted in landslides, and measures the duration and the cumulated rainfall for the events. The algorithm is independent from the local settings and uses a reduced set of parameters to account for different physical settings and operational conditions. We tested the algorithm in Sicily, Italy, with rainfall and landslide information between January 2002 and December 2012. The rainfall conditions responsible for landslides identified by the algorithm were compared against results obtained manually. The algorithm was proven capable of accurately reconstructing most (87.7 %) of the rainfall events. For each landslide, the algorithm identified a variable number of rainfall conditions responsible for the failures, which are equally likely triggers of the landslide. This opens the possibility of evaluating the uncertainty introduced by different criteria to determine the rainfall events responsible for landslides. Use of the algorithm shall contribute to reducing the uncertainty in the definition of landslide-triggering rainfall events, to compiling large catalogues of rainfall events with landslides and to determining reliable rainfall thresholds for possible landslide occurrence.

Description: The patterns of ground movement were monitored within a large, deep-seated landslide complex at Ventnor in southern England, between May 1998 and June 2002 using automated crackmeters, settlement cells and vibrating wire piezometers. It was found that the landslide maintains a state of marginal instability, such that it is subject to continual very slow deformation. Movement is primarily on a low-angled basal shear surface at 〉90 m depth. The movement record shows a series of distinct deformation patterns that vary as groundwater conditions change. Continuous slow deformation occurs across the landslide complex at rates of between 5 and 10 mm/year. The background pattern of movement does not appear to correlate with local porewater pressure. Periods of more rapid movement (reaching up to c. 34 mm/year during the monitoring period) were associated with a period of elevated groundwater, although the relationship between movement rate and porewater pressure was complex. The patterns of movement and the landslide geometry suggest that the likelihood of a rapid, catastrophic failure is low. Future episodes of faster movement are likely during periods when porewater pressures at the basal shear surface are elevated above a critical threshold. Whilst the resulting surface deformation damages the town, it is unlikely to occur rapidly without significant changes to the landslide hydrogeology or the stress state within the landslide.

Description: In January and February 2013, heavy rainfall during local summer storms triggered a large number of landslides in the Andes Main and Frontal ranges of central Chile and Argentina (32°–34° S). Most of the mass movements classify as debris flows, while rockfalls and debris avalanches also occurred. The major debris flows occurred in the Maipo and Aconcagua valleys (Chile) and along the Mendoza River valley (Argentina). The debris flows caused serious disruption to the international highway connecting both countries and local roads and produced a large impact on the population of major cities downstream, mainly due to potable water supply cutoffs. Debris flow deposits have silt and clay particles usually ranging between 10 and 20 % by weight, which favors the movement of viscous flows in short, steep lateral gullies. Most of the flows tended to channelize, and the materials were deposited in alluvial fans and cones in areas with previous records of such events. This indicates that they constitute a significant hazard that may not have been properly considered in road infrastructure and potable water supply strategies for the region. This potential hazard may become more serious due to climate change in the near future.

Description: This paper presents the results of a combined study, using cosmogenic 36 Cl exposure dating and terrestrial digital photogrammetry of the Palliser Rockslide located in the southeastern Canadian Rocky Mountains. This site is particularly well-suited to demonstrate how this multi-disciplinary approach can be used to differentiate distinct rocksliding events, estimate their volume, and establish their chronology and recurrence interval. Observations suggest that rocksliding has been ongoing since the late Pleistocene deglaciation. Two major rockslide events have been dated at 10.0 ± 1.2 kyr and 7.7 ± 0.8 kyr before present, with failure volumes of 40 and 8 Mm 3 , respectively. The results have important implications concerning our understanding of the temporal distribution of paraglacial rockslides and rock avalanches; they provide a better understanding of the volumes and failure mechanisms of recurrent failure events; and they represent the first absolute ages of a prehistoric high-magnitude event in the Canadian Rocky Mountains.

Description: On February 2011, two landslides took place in Çöllolar the lignite mine within 1 week. The first landslide, which occurred at the permanent slopes located in the southwest of the pit, resulted in one fatality and temporary cessation of production activities. Four days later, a second landslide, larger than the first, occurred in the temporary production slopes (northeast of the same pit). The second landslide, with a volume of about 50 Mm 3 soil, resulted in ten fatalities including geological and mining engineers. In the present study, a series of numerical analyses were carried out using the finite element method and the limit equilibrium method to evaluate factors that caused the landslides. Three different depths were considered for the level of ground water table. The safety factors in the permanent slopes were found to be around one or less even if the level of groundwater table was relatively low. It was concluded that the first landslide at the permanent slopes happened possibly due to the high level of water table which was continuously fed by the Hurman River. On the other hand, despite relatively higher safety factors, the failure of the production slopes was triggered probably due to instability introduced by the first landslide.

Description: Rainfall-triggered shallow slope failures are very common in the western Southern Alps of New Zealand, causing widespread damage to property and infrastructure, injury and loss of life. This study develops a geographic information system (GIS)-based approach for shallow landslide/debris-flow susceptibility assessment. Since landslides are complex and their prediction involves many uncertainties, fuzzy logic is used to deal with uncertainties inherent in spatial analysis and limited knowledge on the relationship between conditioning factors and slope instability. A landslide inventory was compiled using data from existing catalogues, satellite imagery and field observations. Ten parameters were initially identified as the most important conditioning factors for rainfall-generated slope failures in the study area, and fuzzy memberships were established between each parameter and landslide occurrence based on both the landslide inventory and user-defined functions. Three output landslide susceptibility maps were developed and evaluated in a test area using an independent population of landslides. The models demonstrated satisfactory performance with area under the curve (AUC) varying from 0.708 to 0.727. Sensitivity analyses showed that a six-parameter model using slope angle, lithology, slope aspect, proximity to faults, soil induration, and proximity to drainage network had the highest predictive performance (AUC = 0.734). The runout path and distance of potential future landslides from the susceptible areas were also modelled based on a multiple flow direction algorithm and the topographic slope of existing debris-flow deposits. The final susceptibility map has the potential to inform regional-scale land-use planning and to prioritize areas where hazard mitigation measures are required.

Description: This paper presents rainfall-induced landslide thresholds and predicts landslide hazard in Kuala Lumpur metropolitan city and surrounding areas. Landslide events from 2000 to 2012 were collected. The long and short antecedent rainfall days were prepared for landslide and non-landslide days simultaneously. First, threshold analysis was conducted by using data obtained from rainfall stations located in highly urbanized areas of Kuala Lumpur metropolis. Six rainfall gauges were selected, and the study area was divided into six zones according to rainfall gauges: Taman Desa Station (TD-KL), Genting Klang (GK-KL), LDG Edinburgh Station (LDGE-KL), SG Raya Hulu Langat Station (SRHL-Slg), Puchong Drop Station (PD-Slg), and Bukit Antarabangsa (BTA-Slg). After the threshold analysis was conducted for different periods (10, 15, and 30 days) in each station, reliability index test was conducted to optimize the best threshold that limits the predicted events along the study period for each region. Second, the threshold analysis results were used as input in the Poisson probability model to estimate landslide temporal probability ( P T ). Third, the spatial probability ( P S ) analysis was prepared by using the evidential belief function multiplied by the P T to obtain the hazard maps for 1-, 3-, and 5-year scenarios. Finally, a validation process was conducted to test the prediction performance of the resultant hazard map for a 1- and 2-year prediction by using the landslide inventory of 2012 to early 2014, which was not included in the modeling of the hazard map. Results showed a valid correlation between the high and moderate hazardous areas for the six zones. The predicted hazard maps indicated a quantitative assessment of the prone areas and proved to be a valid disaster management tool. The produced hazard maps may play a vital role as input component in risk analysis.

Description: A debris flow is an erosional process that frequently occurs in areas with steep slopes. Although the initiation can be triggered in higher and inhabited altitudes, the propagation and then the deposition can endanger urbanized areas. Frequently, the zones of generation of debris flows are placed in unattainable territories complicating field observations. Moreover, the rapid vegetation’s recovery can hide the scars and tracks created by the occurrence of the flow, unlikely to be recognizable in aerial photos. As a consequence, the assessment of debris-flow susceptibility at regional scale is increasing in interest. Two main techniques can be applied for the regional susceptibility assessment: physical models and statistical models. Here, two physical models are introduced simulating the initiation of debris flow by means of shallow landslides: one based on the lateral groundwater flow and the other on vertical groundwater flow. The presented models’ algorithms are implemented in a toolbox based on GIS environment and declared as open source code. Being applied in a basin of the Spanish Pyrenees where soil properties and dataset of observations have been gathered, the two models have been evaluated. Successively, they have been compared with a statistical model based on a logistic regression. The results have been aggregated in terrain units, built as fluvio-morphological sub-catchments. Each model has been tested based on the gathered observations. It has been observed that the vertical flow-based model enhances by 18 % the performance of the lateral flow-based model in matching debris-flow susceptible areas. Furthermore, the vertical flow-based model performance is found to be similar to that of the logistic regression, having an averaged quality index of about 70 %.

Description: This study investigates the role of bed-material anisotropy in triggering landslides in metamorphic terrains of the Darjeeling-Sikkim Himalaya. The initial disposition of foliation (planar anisotropy) with respect to the hillslopes is found to be a crucial parameter in controlling the scale of landslides. Hillslopes with foliation dipping into the surface slope are mostly affected by deeper-seated larger-scale landslides, as compared with those occurring on hills with down slope-dipping foliations. To verify our field observations, we performed scaled slope–failure experiments in a tilted sandbox, simulating the foliation anisotropy in analogue models. Sand–mica beds with the anisotropy planes dipping into the surface slope developed shear localisation along deep-penetrating listric zones, leading to slope failure in the form of down-sliding blocks of large dimensions. In contrast, models with anisotropic planes dipping down slope produced failure zones restricted to the shallow level. The narrow failure zones in the latter case had little tendency to grow in depth but propagated up the hillslope direction. Using Drucker–Prager’s failure criterion, we also ran experiments with finite element models to substantiate the contrasting effects of bed anisotropy on hillslope failure processes.

Description: On 4 July 2013, three catastrophic debris flows occurred in the Hougou, Majingzi, and Xiongjia gullies in Shimian county and produced debris dams and river blockages, resulting in serious casualties and huge economic loss. Though debris flows have been identified prior to the catastrophic events, their magnitudes and destructive power were far beyond early recognition and hazard assessment. Our primary objective for this study was to explore the formation mechanism and typical characteristics and to summarize the lessons learned from these disastrous events in order to avoid the repeat of such disasters in the future. Based on field investigation and imagery interpretation of remote sensing carried out following the catastrophic events, four conclusions were drawn: (1) The catastrophic debris flows were initiated from surface-water runoff, and the triggering factor was attributed to the local intensive rainfall with an hourly intensity of more than 46.7 mm. (2) Entrainment was the most important sediment-supplying method for the debris flow occurrence, and the source materials transported by debris flows from the three gullies were estimated to be about 97 × 10 4  m 3 in volume altogether. (3) As surface-water runoff eroded and entrained hillslope and channel materials persistently, debris flows were characterized by intensive incision at upper or middle reaches and significant magnification effect in flow discharge and volume downstream. Corresponding peak discharge surveyed at the outlets of the Hougou, Majingzi, and Xiongjia gullies was estimated up to 751.0 m 3 /s, 870.1 m 3 /s, and 758.7 m 3 /s, respectively. (4) Debris flows that occurred from the three gullies all belonged to viscous ones and the bulk densities were calculated more than 1.80 g/cm 3 , indicating a huge carrying capacity and destructive impacting power. In addition, the lessons learned from the catastrophic events were summarized, including recognition and assessment on debris flow hazard and utilization of deposition fan. In this paper, prevention suggestions on debris flow prone valleys with high-vegetation coverage and low occurrence frequency were also put forward. The results of this study contribute to a better understanding on the initiation mechanism, dynamic characteristics, and disaster mitigation of debris flows initiated from intense rainfall and surface-water runoff in mountainous areas.

Description: In recent decades, the concept of cultural heritage has evolved into one that encompasses an understanding of the history of humanity, together with scientific knowledge and intellectual attitudes. This changing concept has prompted a subsequent re-evaluation of what constitutes the outstanding universal values of World Heritage sites and the operational methods for implementing the UNESCO World Heritage Convention. The scope has broadened from studying a single monument in isolation to one that values a multidimensional, multiregional, and inter-disciplinary approach and encapsulates vast spans of human history. Within this broader view, landslides and more generally slope instabilities are an important factor endangering cultural heritage sites, especially prehistoric sites, earth/rock monuments, and archaeological sites affected by environmental processes and degradation. Natural and cultural heritage sites, as well as cultural landscapes, are then tied into a common framework that the Geological Society of America has defined “Men’s legacy to Earth and Earth’s legacy to Man”. On the other hand, not too much effort has been expended in the past to develop conservation policies systematically integrating geological, geomorphological, and engineering geological aspects into daily practices. The purpose of the “LAndslides and CUltural & Natural HEritage” thematic Network (LACUNHEN) is to create a platform for scientists and practitioners who are ready to jointly contribute to safeguarding relevant endangered Natural and Cultural Heritage sites (e.g., Machu Picchu). They will share and disseminate their respective experience, demonstrating how these special “objects” require approaches, techniques, and solutions that go far beyond traditional civil engineering perspectives.

Description: This paper analyzes the effects of a historical rain series on pore water pressure distribution in the Costa della Gaveta landslide, in the Southern Apennine, Italy. The effects of pore water pressure variations on the safety factor and on the displacement rate of the landslide are also analysed. The aim of the investigation is to reach a deeper understanding of the influence of hydrological parameters on the mechanism of movements of the widespread type of active, very slow landslides in fine-grained soils. Pore water pressures were evaluated by means of the 3D finite difference code MODFLOW, applying as boundary condition the long historical rainfall series of the site. The transient analysis carried out with a daily resolution successfully reproduces the trend of piezometric data. The results show that because of the subsoil low permeability ( k  = 10 −8 –10 −9  m/s), pore water pressure variations caused by rain are significant only at depths lower than about 10 m. Furthermore, noticeable depth-depending time lag is evaluated between the external hydrological input and responses of internal pore water pressures. Pore water pressure variations on the shallowest areas of the slip surface have the greatest influence on the 3D limit equilibrium safety factor and thus on the landslide movements. As a matter of fact, the safety factor seems to be well correlated to the displacement rates evaluated by inclinometers at various depths, on the slip surface. The results of the 3D model provide pore water pressure distributions which are significantly different, both in value and in time trend, from those obtained by using 2D models.

Description: Sassa and others in the Disaster Prevention Research Institute (DPRI), Kyoto University, developed a series of undrained ring-shear apparatus to physically simulate landslide initiation and motion, from DPRI-3 (Sassa 1992 ) to DPRI-7 (Sassa et al., Landslides 1(1):7–19, 2004 ). The maximum undrained capacities in the DPRI series ranged from 300 to 650 kPa. Sassa and others in the International Consortium on Landslides (ICL) have developed a new series of undrained ring-shear apparatus (ICL-1and ICL-2) for two projects of the International Programme on Landslides (IPL-161 and IPL-175). Both projects are supported by the Science and Technology Research Partnership for Sustainable Development Program (SATREPS) of Japan. ICL-1 was developed to create a compact and transportable apparatus for practical use in Croatia; one set was donated to Croatia in 2012. ICL-2 was developed in 2012–2013 to simulate the initiation and motion of megaslides of more than 100 m in thickness. The successful undrained capacity of ICL-2 is 3 MPa. This apparatus was applied to simulate possible conditions for the initiation and motion of the 1792 Unzen–Mayuyama megaslide (volume, 3.4 × 10 8  m 3 ; maximum depth, 400 m) triggered by an earthquake. The megaslide and resulting tsunami killed about 15,000 people. The Unzen Restoration Office of the Ministry of Land, Infrastructure and Transport (MLIT) of Japan systematically collected various papers and reports and published two summary leaflets: one in English in 2002 and an extended version in Japanese in 2003. Samples were taken from the source area (for initiation) and the moving area (for motion). The hazard area was estimated by the integrated landslide simulation model LS-RAPID, using parameters obtained with the ICL-2 undrained ring-shear apparatus. The estimated hazard area agrees reasonably with the landslide moving area reported in the Ministry leaflets.

Description: The construction work of the DG22 mega lot, an 11-km segment of the new Jonica national road (southern Italy), mainly involves the Pliocene deposits belonging to the Trubi stiff jointed formation. This paper focuses on the geotechnical studies carried out to explain the kinematics of the instability processes which were observed during excavation work. Two different cases are presented. The first one refers to the movements caused by a 20-m-high slope excavated for a cut and cover tunnel. The second one describes the kinematics of the failure of a shallow tunnel which caused the subsidence of a widely extended area. In both cases, the response of the soil mass to the excavation was governed by the system of discontinuities that characterizes the Trubi clay formation. The influence of the structural features, beyond the knowledge of the mechanical behavior of the soil at the scale of the laboratory sample, was an essential ingredient to find a convincing explanation for both phenomena observed.

Description: Landslide risk assessments provide essential information to develop loss reduction strategies. However, only very few studies produce risk maps. Lack of temporal data on landslides is one of the reasons. This paper develops a methodology to assess the economic risk of landslides when limited landslide hazard information is available. It provides spatially explicit estimates of future landslide risks in a densely populated low-relief area and applies different spatial probability scenarios. In the study area (710 km 2 ), residential buildings cover 7 % of the area with elements at risk, but are responsible for about 86 % of the total risk. Roads cover 8 % of the area with elements at risk but are responsible for about 14 % of the total risk. The annual landslide risk is approximately 50 million to 80 million euros 2011 values depending on the spatial probability scenario considered. This indicates that landslide mitigation efforts would create considerable benefits. Landslide risk would reduce significantly if better land use zoning would be applied to sterilize landslide-prone terrain as particularly the residential buildings and access roads determine the total risk.

Description: A new method, the so-called pressure probe (Pre-P) method, has been developed for detecting and characterizing mechanically weak zones which may not be visible from the surface and which may occur, e.g. due to landslides. On a high bank at Dunaszekcső, Hungary, the fracture system of the loess landslide area was investigated by large resolution applying this method and proved that (1) cracks as small as 2- to 3-cm wide are detectable; (2) the fractures follow each other almost periodically; and (3) on the side of the fractures towards the slump, there are less fractured zones whose width correlates with the width of the given fracture. We also demonstrated that on the passive side of the clearly visible fracture, (1) there are also fractures along which future rock displacement is expected; (2) these fractures are at least as wide as the active side fractures; and (3) the blocks there are about twice as wide as those on the active side. A block several meters wide is expected to fall before the main mass movement. The Pre-P method seems to be the most powerful tool to map the fracture system of such landslides because of its speed, simplicity of application, cost and interpretation. The Pre-P profiles and maps of the fracture system of a landslide enable to understand landslide evolution and delineate endangered areas earlier than by other methods.

Description: The Northwest of Portugal is a steep slope mountain area where high amounts of rainfall (3,000 mm/year) occur especially on winter, promoting high natural propensity to slope failure, mainly shallow landslides. This article aims to assess shallow landslide susceptibility, in Tibo catchment, Serra da Peneda, North of Portugal, using two physically based models— SHAllow Landslide STABility (SHALSTAB) and Safety Factor (SF)—applying a set of mechanical and hydrological parameters, assessed in situ and laboratory testing of soil samples collected in the field, calibrated by back analysis of landslides inventoried in the study area, as well as accurate topographic information derived from a high-resolution digital elevation model (DEM). The validation of results was made using shallow landslide scars, directly inventoried in the field. Both susceptibility model results were validated by scar concentration (SC) and landslide potential (LP). SHALSTAB model was also validated by minimum log q / T . SHALSTAB predicts 50 % of the area to be on unstable classes (log q / T  〈 −2.5), 77 % of the SC on unstable classes and a LP index of 7 and 4.7 % for the two most unstable classes. By minimum log q / T , SHALSTAB predicts 91 % of the scars to occur on unstable classes. Safety factor predicts 47.99 % of the area as unstable, 79.9 % of the SC for unstable classes, and a LP index on unstable classes of 4.63 and 2.77 % on partially unstable class. For the most unstable classes of both models, the greatest values of LP were between 3.5 and 7 %. The simple physically based models used in this study (SHALSTAB and SF) proved to be effective as shallow landslide susceptibility predictors, being in consequence useful tools for municipal planning on landslide hazards, but their application requires, beyond detailed topographical information, good estimates of the mechanical and hydrological soil properties.

Description: This work focuses on the development of a combined statistical-mechanical approach to predict changes in landslide displacement rates from observed changes in rainfall amounts. The forecasting tool FLAME (Forecasting Landslides Accelerations induced by Meteorological Events) associates (1) a statistical impulse response (IR) model to simulate the changes in landslide rates by computing a transfer function between the input signal (e.g. rainfall) and the output signal (e.g. displacement) and (2) a simple 1D mechanical (MA) model (e.g. viscoplastic rheology) to take into account changes in pore water pressure. The models have been applied to forecast the displacement rates at the Super-Sauze landslide (South East France). The performance of different combinations of models (IR model alone, MA model alone and a combination of the IR and MA models) is evaluated against observed changes in pore water pressures and displacement rates at the study site. Results indicate that the three models are able to reproduce the displacement pattern in the general kinematic regime (succession of acceleration and deceleration phases); conversely, extreme kinematic regimes such as fluidization of part of the landslide mass are not being reproduced. The approach constitutes however a robust tool to predict changes in displacement rates from rainfall or groundwater time series.

Description: This paper discusses the effect of the May 12, 2008 Wenchuan earthquake on a landslide where stabilization work had taken place and compares the results to sites without stabilization. Contours of shear strain increment and displacement values obtained using a FLAC3D simulation show that the Wangjiayan landslide, which had stabilization work, was stable before the Wenchuan earthquake. Simulations using input strong motion accelerations from the main shock recorded at Qingping station, within the main seismic fault zone, suggest a shear strain increment about 3,000 times more than it was before the main shock. Although the stability of the stabilized landslide decreased during the earthquake, the displacement values were very small. Modeled displacements suggest that the piles played a major role in keeping the slope from sliding. The anti-slide piles were subjected to high shaking acceleration. The strong ground motion records for a time range of 10 to 30 s show that the piles generally experienced accelerations in the range from 0.0 to 3.0 g, with a few spikes of about 5.0 g. Special observation stations were set up to monitor the slope motion at Qingchuan town, 150 km far from the Wangjiayan landslide, along the main central seismic fault zone, after the Wenchuan earthquake. The variation in acceleration with time and the FOS versus time of the Wangjiayan landslide were investigated using these acceleration records of the aftershocks as input data. The aftershock accelerations did not decrease the stability of the Wangjiayan landslide, but an amplification effect on the acceleration of the slope at different elevations was illustrated.

Description: This research proposes a conceptual approach for analysis and numerical modelling of the hydromechanical behaviour of large landslides, applied to one of the source areas of the Corvara earthflow (Dolomites, Italy). The approach consists of two steps: forward calculation and inverse analysis. For the forward calculations, the geological model of the slope considering several shear zones delimitating landslide units was developed, based on a detailed dataset of field investigation and monitoring data. A viscoplastic constitutive model was used to describe the time-dependent material behaviour, i.e. the creep, of the shear zones. The transient distribution of pore water pressure in the slope was considered by means of an additional purely hydrogeological model. These results were used as averaged hydraulic boundary conditions in the calculation of stress and deformation fields with the continuum finite element method (FEM). The numerical model was then calibrated against ground surface displacement rates measured by D-GPS, by iteratively varying the material parameters of the shear zones. For this task, an inverse analysis concept was applied, based on statistical analyses and an evolutionary optimisation algorithm. The inverse modelling strategy was further applied to gather statistical information on model behaviour, on the sensitivity of model parameters and on the quality of the obtained calibration. Results show that the calibrated model was able to appropriately simulate the displacement field of the earthflow and allow the requirements, difficulties and problems, as well as the advantages and benefits of the proposed numerical modelling concept to be highlighted.

Description: Slope failures world-wide cause many thousands of deaths each year and damage built environment infrastructure, costing billions of pounds to repair, resulting in thousands of people being made homeless and the breakdown of basic services such as water supply and transport. There is a clear need for affordable instrumentation that can provide an early warning of slope instability to enable the evacuation of vulnerable people and timely repair and maintenance of critical infrastructure. An approach, Assessment of Landslides using Acoustic Real-time Monitoring Systems (ALARMS) is described in the paper, and results of a field trial of sensors on an active landslide at Hollin Hill, North Yorkshire, UK, are described. Continuous and real-time monitoring of acoustic emission generated by the deforming slope has been compared to traditional inclinometer slope displacement measurements. Analysis of the results has established that there is a direct relationship between acoustic emission rate and displacement rate trends triggered by rainfall events. The technique has provided insight into reactivated slope movement kinematics.

Description: Hazard and risk assessment of landslides with potentially long run-out is becoming more and more important. Numerical tools exploiting different constitutive models, initial data and numerical solution techniques are important for making the expert’s assessment more objective, even though they cannot substitute for the expert’s understanding of the site-specific conditions and the involved processes. This paper presents a depth-integrated model accounting for pore water pressure dissipation and applications both to real events and problems for which analytical solutions exist. The main ingredients are: (i) The mathematical model, which includes pore pressure dissipation as an additional equation. This makes possible to model flowslide problems with a high mobility at the beginning, the landslide mass coming to rest once pore water pressures dissipate. (ii) The rheological models describing basal friction: Bingham, frictional, Voellmy and cohesive-frictional viscous models. (iii) We have implemented simple erosion laws, providing a comparison between the approaches of Egashira, Hungr and Blanc. (iv) We propose a Lagrangian SPH model to discretize the equations, including pore water pressure information associated to the moving SPH nodes.

Description: On October 25, 2011, an extreme rainfall event affected a wide area along the coasts of Cinque Terre (eastern Liguria, northern Italy). Particularly, in the Vernazza catchment, the event triggered hundreds of shallow landslides and a debris flood that caused three casualties. Investigation of the slope stability after the event was carried out aiming at defining the most effective mitigation measures which may be adopted in future land use planning. To this objective, a susceptibility model was produced and a series of scenarios were simulated using probabilistic methods. The susceptibility model has provided information about landslide conditioning factors on which to act for reducing landslide occurrence and therefore the associated risk. The simulations have taken into consideration the following alternative types of mitigation measures: (1) restoration of abandoned terraces, (2) reforestation of abandoned terraces, (3) use of local structural measures over stretches of potentially unstable hillsides and (4) avoidance of any intervention. The advantages and the disadvantages of the proposed mitigation measures for shallow landslide risk are discussed considering the results of the simulations and taking into account their complex interaction with environmental, historical, cultural and socio-economic aspects. The results show that the most effective mitigation strategy for reducing landslide risk at short term consists of applying structural measures over potentially unstable slopes. However, a long-term programme promoting the development of agricultural or forestry practices on terraced slopes is necessary. In fact, the simulations indicate that if no measures are applied to avoid the degradation of the terraced areas, landslide areal frequency would inevitably increase.

Description: Huangtupo landslide, volumetrically the largest, most complex landslide in the Three Gorges Reservoir region of China, is a dangerous mass on which the district of Badong has been inadvertently situated. Risk remediation efforts include the construction of a large observational tunnel and monitoring system that are unique in the world. This tunnel and its side branches permit detailed mapping of its 3D structure while providing samples for laboratory analysis. The new investigations validate that the Huangtupo landslide is a composite of several independent landslides and that movement occurs along the major rupture zones as well as on interlayer sliding zones in the underlying Badong Formation. Uranium–thorium disequilibrium dating establishes that the northern part of the landslide, called the Riverside Slump, underwent at least two periods of movement at about 100 and 40 ka (ka stands for a thousand years). These events were induced by the steep slope created by the downcutting of the Yangzte River. The results from in situ displacement monitoring over a 7-year period confirm that the central part of the landslide is creeping at a slow, relatively stable rate of about 15 mm/year rather than being in a stage of acceleration under the protection of anchored concrete beams and other defense structures at its toe. Available data suggest that engineering measures can control the independent landslides that together constitute the huge Huangtupo mass, which will avoid the need for costly relocation of thousands of people.

Description: Real-time early warning systems for shallow landslides are typically built upon real-time measurements and forecasts of rainfall and empirical correlations between past patterns of rainfall and landslide occurrence. Whereas these relationships describe whether certain combinations of rainfall and preexisting groundwater levels are of elevated risk of landslide triggering, not all combinations leading to landslide events necessarily have the same consequences in terms of landslide mobility (velocity and distal reach of the landslide). In this paper, the technique of geotechnical centrifuge modeling is used to quantitatively evaluate the hypothesis that the mobility of a landslide triggered under elevated antecedent groundwater conditions is higher than scenarios under drier antecedent conditions. Five identical slope models with a shallow depth to bedrock were subjected to different antecedent conditions ranging from zero groundwater flux to nearly saturated conditions prior to rainfall. The results from these scenarios show that higher antecedent groundwater conditions can result in landslides with velocities about three times higher and travel distances about eight times higher than low antecedent conditions due to static liquefaction of the soil at the base of the slope.

Description: Catastrophic rock avalanches contribute to rapid landscape evolution and can harm humans directly or by secondary effects such as displacement waves. Predicting the volume, timing, and consequences of rock slope failures is therefore essential to managing risk and interpreting landscape response to climatic or tectonic forcing. Here, we synthesize geologic and geodetic observations to document the spatial pattern of movement rates and failure mechanisms at a landslide complex in western Norway, recently identified with systematic interferometric synthetic aperture radar (InSAR) reconnaissance. A differential global navigation satellite system (dGNSS) and global positioning system (dGPS) campaign confirms active slope deformation with horizontal displacement rates of 1.2 to 2.6  mm  year −1 at four points distributed across the landslide’s ~1.8-km width. Displacement vectors are consistent with landslide movement occurring on pre-existing discontinuity sets, and a broad synform controls failure mechanisms within the landslide complex. Two ~1.5 million m 3 blocks are wedge failures, while flexural toppling and planar sliding of smaller blocks occur throughout the landslide complex. Modern movement rates are comparable to or slower than Holocene-averaged displacement rates, suggesting continued steady deformation or stabilization of parts of the landslide with time. However, a large volume failure with typical run-out for rock avalanches would likely reach the subjacent fjord, causing a displacement wave. We suggest that our collaborative approach of integrating a wide variety of geologic and geodetic methods will be useful for more thoroughly documenting additional landslide sites and for making informed decisions about risk management.

Description: Regional-scale forecasting of landslides is not a straightforward task. In this work, the spatiotemporal forecasting capability of a regional-scale landslide warning system was enhanced by integrating two different approaches. The temporal forecasting (i.e. when a landslide will occur) was accomplished by means of a system of statistical rainfall thresholds, while the spatial forecasting (i.e. where a landslide should be expected) was assessed using a susceptibility map. The test site was the Emilia Romagna region (Italy): the rainfall thresholds used were based on the rainfall amount accumulated over variable time windows, while the methodology used for the susceptibility mapping was the Bayesian tree random forest in the tree-bagger implementation. The coupling of these two methodologies allowed setting up a procedure that can assist the civil protection agencies during the alert phases to better define the areas that could be affected by landslides. A similar approach could be easily adjusted to other cases of study. A validation test was performed through a back analysis of the 2004–2010 records: the proposed approach would have led to define a more accurate location for 83 % of the landslides correctly forecasted by the regional warning system based on rainfall thresholds. This outcome provides a contribution to overcome the largely known drawback of regional warning systems based on rainfall thresholds, which presently can be used only to raise generic warnings relative to the whole area of application.

Description: A case study on an open hillside landslide impacting on a flexible rockfall barrier at Jordan Valley, Hong Kong is presented in this paper. The landslide occurred sometime in June 2008. This is so far the only case history of landslide debris having been intercepted by a flexible rockfall barrier in Hong Kong. The landslide scar is 10 m wide and 7 m long, and the landslide volume is about 110 m 3 . The landslide debris was largely retained by the barrier but two of the barrier posts were severely damaged and failed. Debris mobility analysis and structural analysis of this case history have been undertaken with a view to obtaining a better understanding of the possible landslide dynamics and behaviour of flexible barrier upon debris impact. The analyses appear to have reproduced some of the salient field observations. The probable key contributory factors to the failure are highlighted and discussed. Through the study, the possible range of equivalent pseudo-static impact pressure exerted on the flexible barrier by the landslide debris is assessed. The site observations and results of the analyses provide insights pertaining to the importance of robustness in the design and detailing of flexible debris-resisting barriers.

Description: This paper presents a comparison of persistent scatterer interferometry (PSI) monitoring results with in situ displacement measurements at the November 1990 landslide at the Boršt uranium mill tailing deposit site after heavy rain. Although the landslide did not directly endanger people, site remediation works were undertaken due to the subsequent environmental problems. Additionally, in situ monitoring with benchmarks was established in order to detect the ground motion of the landslide body. PSI campaigning in the Škofjeloško-Cerkljansko area, where the uranium mill tailing is situated, performed for the purpose of measuring displacements of natural targets near the active landslide area, also detected displacements, most probably indicating a creeping process. When comparing the pre- and post-remediation velocities at the benchmarks located on the landslide with persistent scatterers (PSs) located near the landslide, the rates could be regarded as background. The results show that the remediation works in the form of a drainage tunnel were very effective as post-remediation velocities at the landslide closer to the PSs resembled the velocities of the PSs, while the velocities of the landslide mass above the drainage tunnel slowed down, even to below the background velocities. The high correlation values between the movements of the benchmarks and the PSs also confirm that the remediation works were effective as the fluctuations in the displacement values of the landslide were very similar to those of the PSs. Nevertheless, although there are several limitations in comparing the two different datasets, the PSI technique can be complementary to conventional in situ methods.

Description: Capacity development is important and urgently needed for landslide disaster risk reduction. This is especially so in developing countries where mountain and urban development is accelerating most rapidly, including construction of highways and railways and residential complexes. However, effective tools to teach practical landslide risk reduction knowledge and skills are not available. Therefore, International Consortium on Landslides (ICL) has decided to compile a collection of landslide teaching tools (Sassa et al. 2013 ) to provide teaching materials to ICL members and other landslide teaching entities to assist in education of university students, local government officers, staff in nongovernmental organizations, and the public. The teaching toolbox contains five parts: (1) mapping and site prediction; (2) monitoring and early warning; (3) testing and numerical simulation; (4) risk management; and (5) country practices and case studies. The teaching toolbox contains three types of tools: (1) TXT tools consisting of original texts with figures; (2) PDF tools consisting of already published reference papers, manuals, guidelines, and others; and (3) PPT tools consisting of PowerPoint® files made for lectures. The initial TXT tools have been published as a full color booklet (405 pages). The PDF tools and PPT tools are contained in a CD. The basic concept and a list of contents of the ICL landslide teaching tools are introduced in this article.

Description: The aim of this study was to produce a map of landslide susceptibility zonation (LSZ) using analytic hierarchy process (AHP) for recognition of a hazardous prone zone in the Bojnurd region, northeast of Iran. A database included nine topographic, geomorphologic, and climatic parameters that affect landslide susceptibility produced by digitizing the elevation data from topographic maps and some spatial analyst procedures in GIS. Some rock falls and landslides were observed dominantly on the steep slopes of limestone formations. The study area were divided into five susceptibility zones, namely, very high, high, moderate, low, and negligible. It demonstrated that about 70.21 % of the region in the south and east are prone to moderate to very high levels of landslide susceptibility. According to landslides inventory map, the most occurred landslides had the well-corresponding with high and very high landslide susceptibility classes in the region. Based on empirical classification of the AHP, the precipitation, geology, land use, and slope were the most heavily weighted factors with weightings of 0.182, 0.176, 0.166, and 0.163, respectively. While based on the spatially crosschecking, the landslide events in the study area strongly correlated with geology and slope, which exhibited on the final LSZ map.

Description: Ten small rock slides (with a volume ranging from 10 1 to 10 3  m 3 ) on a slope affected by working activities were detected, located, and timed using pictures collected by an automatic camera during 40 months of continuous monitoring with terrestrial SAR interferometry (TInSAR). These landslides were analyzed in detail by examining their pre-failure time series of displacement inferred from high-sampling frequency (approximately 5 min) TInSAR monitoring. In most of these cases, a typical creep behavior was observed with the displacement starting 370 to 12 h before the collapse. Additionally, an evident acceleration decrease of the displacement a few hours before the failure was observed in some rock/debris slides, thus suggesting the possibility of a mechanical feature of the slope that differs from the classical creep theory. The efficacy of the linear Fukuzono approach for the prediction of time of failure was tested by back-analyzing the ten landslides. Furthermore, a modified Fukuzono approach named average data Fukuzono (ADF) was implemented and applied to our dataset. Such an approach is able to improve forecasting effectiveness by reducing the error due to anomalies in the time series of displacement, like the acceleration decrease before failure. A prediction with a temporal accuracy of at least 2 h was obtained for all the analyzed rock/debris slides.

Description: Slopes that are terraced by means of dry-stone retaining walls are very common in the alpine environment. In Valtellina, a typical Italian alpine valley, these slopes are widespread and quite often involved in superficial mass movements that can result in severe damage and casualties. For an in-depth understanding of the processes that can trigger these events, numerical modeling of groundwater movement and a related stability analysis were performed on a detailed scale, based on an intensive monitoring of rainfall events and groundwater movement. Field observations suggest that the formation of a perched groundwater table at the contact between the bedrock and the backfill soil of walls as well as the concomitant saturation of this backfill soil are the determining factors of potential slope failure. The numerical models support these observations. In addition, the models are able to explain the mechanisms of formation of perched water tables, highlighting the factors that can influence groundwater levels and slope instabilities.

Description: During the last decade, several rainfall-induced deep-seated large landslides with volumes of the order of 1 million m 3 were triggered in various locations in Slovenia (central Europe), each representing a serious threat to the nearby villages and traffic infrastructure and urging to be mitigated. The Macesnik landslide, triggered in 1989, and the Slano blato landslide, triggered in 2000, were the first two large landslides in Slovenia, where a combination of drainage and retaining works consisting of deep reinforced concrete (RC) shafts/wells was successfully used as a mitigation measure. This paper presents the field conditions and a brief history of the two landslides with emphasis on the design approach and method used for the stability analysis and the design of deep RC shafts/wells. In addition, the paper gives an insight into the problems associated with the execution of works and provides data about the behavior of the two landslides after drainage and retaining works were completed. The monitoring data show that the undertaken mitigation measures were efficient to improve the stability of both landslides and significantly reduce the risk.

Description: A catastrophic rock debris avalanche on one of the highlands demarcating Cameroon and Nigeria, 3 days after a transient period of heavy rainfall in November 2010, killed two people and damaged economic trees, plants and farmlands. Detailed field investigation and sampling were undertaken by a team from the International Programme on Landslide to analyse the slope movement. The investigation was in two phases—5 days and then 7 months after the event to study the effect of alternating dry and rainy seasons on the geotechnical properties of the materials associated with the slope failures. It was also aimed at assessing the effect of time on the morphology of the slip plane as a new approach to understanding the development of potential failure planes and reactivated landslides. Available evidence showed that present failure planes form mini-deposition axes which may become future slip zones as they are still steep enough to accelerate instability. The research also traced the pattern of rock weathering and joints evolution in the area and found that the systematic weathering of feldspar in the basement aggravated slope instability by creating zones of weakness characterized by structures that aid fragmentation. Soils were thin (〈1 m) in some slopes and deep (〉2 m) in others and may represent the differential effect of weathering and erosion on the mountains which are important in analyzing the mechanism and mobility of the failed masses. Samples collected were subjected to various geotechnical laboratory tests such as unconsolidated undrained triaxial, consistency, particle size and permeability tests.

Description: Throughout the history, many lives have been lost due to landslides. Understanding the process of human flight during landslide events is important in assessing the risks posed by future landslides. This study proposes a model for simulating human flight from a quick shallow landslide along a road, quantifies the flight success rate, and identifies the crucial variables that impact flight efficiency. A questionnaire survey was undertaken along a stretch of highway near Yingxiu, China to collect information regarding human responses and behavior in the face of landslide events. The factors influencing human flight are classified into factors related to the evacuees, the landslide intensity, and the flight path. Subsequently, a flight model is proposed to simulate the movements of people randomly located along a road threatened by landslides. Various components of “available time” and “demand time” for escaping from the landslide affected area are treated as random variables. Based on this model, probability analysis is conducted to estimate the flight success rates of the people at risk when fleeing from landslides of various intensities. Sensitivity analysis shows that the pre-failure time and the response time are the most important factors in the flight process. Finally, comparison between the flight success rates from two existing methods and those from the new model is made.

Description: The Ancona landslide is a complex, deep-seated landslide displaying composite rotational–translational kinematisms and affecting a large urban area in the Ancona municipality on the Adriatic coast of central Italy. The landslide was reactivated with a large and destructive event on 13 December 1982 following a long period of precipitation and has remained active since. This paper focuses on the estimation of the landslide kinematics (more specifically, the horizontal and vertical components of average yearly velocity) for subsequent estimation of risk for a set of 39 buildings as presented in a companion paper. The study relies both on the processing of inclinometer and radar interferometer monitoring data through statistical procedures. Triggering factors are not investigated. Outputs from the two sets of monitoring data are compared quantitatively and qualitatively. The inherent limitations in available data are discussed. The validity of the quantitative results in the context of the risk estimation effort is discussed.

Description: Debris flows surge downslope carrying destructive energy and can result in long runout distances. Structural mitigation is commonly installed along the flow path to impede debris flow mobility and protect downstream facilities. An array of baffles is a structural countermeasure frequently designed using empirical methods or prescribed to impede debris flow; nonetheless, its influence on reducing mobility is not well understood. A 5-m-long flume model is used to conduct a series of tests to systematically study the effects of varying baffle height, number of rows, spacing between rows, and degree of transverse blockage on mobility. Froude scaling is adopted to characterize initial upstream conditions. Debris runout, overflow, and frontal velocity reduction resulting from each baffle configuration used are examined. Experimental results reveal that it is imperative to adopt baffle heights taller than the approach flow depth ( h ) in order to suppress overflow and reduce runout. Adopting 1.5  h -tall baffles can reduce runout and peak overflow depth by 19 and 20 % compared to short baffles (0.75  h ), respectively. A single row of baffles is ineffective in reducing frontal debris velocity, whereas increasing the array to three rows leads to 65 % reduction in runout and up to 57 % reduction in frontal velocity. Increasing spacing between successive rows from 0.25 w to 0.5 w can reduce runout by up to 37 %.

Description: Debris flow occurs frequently (ten events on average per year) and displays a great variety of properties in the Jiangjia Gully (JJG) in southwest China. We find that the material of debris flow satisfies a universal grain size distribution (GSD) of P ( D ) =  CD − μ exp(− D / D c ), and the parameters μ and D c are closely related to the dynamical properties such as flow density, velocity, and discharge. A small μ implies a small porosity and possible high excess pore pressure in flow, reflecting high mobility and capacity of transportation, and a large D c means a wide range of grain composition and hence a high grain concentration. A debris flow always achieves a state of certain mobility and density that can be well described by μ and D c , and the parameters impose power law constraints on the fluctuations of debris flow surges. An upper limit of unit-width discharge is estimated as Q u  = 1.25 D c 1.12 . Variation of GSD parameters also describes material exchanges between debris flow and streambed sediment. Intense incision or deposition occurs when remarkable difference of grain composition exists. As the GSD is satisfied universally, the results derived from JJG are expected to be applicable for evaluating the properties and peak discharge of a potential debris flow in other conditions.

Description: In March 2012, during the rainy season in the Altiplano plateau, a 〉100-year return period rainfall event affected the deeply incised valleys of the Precordillera of the Tarapacá Region, northern Chile. This extreme event in a very arid region triggered a number of debris and mud flows that caused severe damage and destruction in several small villages along the Camiña and Tarapacá valleys. The highly vulnerable location of the villages on top of alluvial fans due to socioeconomic and cultural reasons is a key factor to explain the level of destruction in most villages. In this paper, this unusual, remarkable landslide event is described, and the hazard faced by these settlements for future rainfall episodes and possible mitigation measures are discussed.