Modeling of rainfall-triggered shallow landslide

By integrating hydrological modeling with the infinite slope stability analysis, a rainfall-triggered shallow landslide model was developed by Iverson (Water Resour Res 36:1897-1910, 2000). In Iverson’s model, the infiltration capacity is assumed to be equivalent to the saturated hydraulic conductivity for finding pressure heads analytically. However, for general infiltration process, the infiltration capacity should vary with time during the period of rain, and the infiltration rate is significantly related to the variable infiltration capacity. To avoid the unrealistically high pressure heads, Iverson employed the beta-line correction by specifying that the simulated pressure heads cannot exceed those given by the beta line. In this study, the suitability of constant infiltration capacity together with the beta-line correction for hydrological modeling and landslide modeling of hillslope subjected to a rainfall is examined. By amending the boundary condition at ground surface of hillslope in Iverson’s model, the modified Iverson’s model with considering general infiltration process is developed to conduct this examination. The results show that the unrealistically high pressure heads from Iverson’s model occur due to the overestimation of infiltration rate induced from the assumption that the infiltration capacity is identical to the saturated hydraulic conductivity. Considering with the general infiltration process, the modified Iverson’s model gives acceptable results. In addition, even though the beta-line correction is applied, the Iverson’s model still produces greater simulated pressure heads and overestimates soil failure potential as compared with the modified Iverson’s model. Therefore, for assessing rainfall-triggered shallow landslide, the use of constant infiltration capacity together with the beta-line correction needs to be replaced by the consideration of general infiltration process.     

Impact of the Trans-Himalayan Landslide Lake Outburst Flood (LLOF) in the Satluj catchment, Himachal Pradesh, India

Landslide Lake Outburst Floods (LLOFs) are common in the Himalayan river basins. These are caused by breaching of lakes created by landslides. The active and palaeo-landslide mapping along the Satluj and Spiti Rivers indicate that these rivers were blocked and breached at many places during the Quaternary period. In the present article, we document LLOFs during 2000 and 2005 caused by the breaching of landslide lakes created in the Trans-Himalayan region along the Satluj River and Paree Chu (stream), respectively, both in the Tibetan region of China and its impact on the channel and infrastructure in the Kinnaur district of Himachal Pradesh, India. It has been observed that the loss of life and property due to these LLOFs is directly related to the disposition of the Quaternary materials and the different morphological zones observed in the area.     

Evaluation of landslide triggering mechanisms in model fill slopes

Hong Kong is particularly susceptible to landslide risk due to the steep natural topography and prolonged periods of high intensity rainfall. Compounding the risk of slope failure is the existence of loose fill slopes which were constructed prior to the 1970s by end-tipping. A clear understanding of the underlying triggering mechanisms of fast landslides in fill slopes is required to analyse landslide risk and to optimise slope stabilisation strategies. The work described here had the objective of evaluating two candidate triggering mechanisms—static liquefaction and the transition from slide to flow due to localised transient pore water pressures—against observations of slope behaviour obtained from highly instrumented centrifuge model tests. These results indicate that static liquefaction is unlikely to occur if the model fill is unsaturated and the depth to bedrock large, as the high compressibility and mobility of air in the unsaturated void spaces allows the model fill slope to accommodate wetting collapse without initiating undrained failure. In contrast, high-speed failures with low-angle run-outs are shown to be easily triggered in model fill slopes from initially slow moving slips driven by localised transient pore water pressures arising from constricted seepage and material layering.     

Spatio-temporal estimation of shallow landslide hazard triggered by rainfall using a three-dimensional model

A shallow landslide triggered by rainfall can be forecast in real-time by modeling the relationship between rainfall infiltration and decrease of slope stability. This paper describes a promising approach that combines an improved three-dimensional slope stability model with an approximate method based on the Green and Ampt model, to estimate the time–space distribution of shallow landslide hazards. Once a forecast of rainfall intensity and slope stability-related data, e.g., terrain and geology data, are acquired, this approach is shown to have the ability to estimate the variation of slope stability of a wide natural area during rainfall and to identify the location of potential failure surfaces. The effectiveness of the estimation procedures described has been tested by comparison with a one-dimensional method and by application to a landslide-prone area in Japan.     

香溪河流域白家堡滑坡变形监测初步分析

白家堡滑坡受三峡大坝蓄水及强降雨影响变形较为明显,且仍在变形过程中.利用GDM600S型全站仪及cx-03D型钻孔测斜仪分别对滑坡地表及滑坡深部位移进行监测.监测结果表明:白家堡滑坡体呈 "D" 型整体运动;滑坡后缘滑动面(带)和中部滑动面(带)分别在地下11 m和28.5 m左右;滑坡整体滑动方向大致为NE 55°,且滑坡变形具有自后缘向前缘递减的趋势.     

The influence of rainstorm pattern on shallow landslide

In this study, the influence of the rainstorm pattern on shallow landslide is examined. The physically-based shallow landslide model is used to conduct this examination with considering four representative rainstorm patterns including uniform, advanced, central, and delayed rainstorms. The results show that in spite of the rainfall duration and the rainfall pattern, the rainstorm with less than the minimum landslide-triggering rainfall amount will not trigger landslide. However, for the rainstorm with greater than the minimum landslide-triggering rainfall amount, the occurrence of landslide significantly depends not only on the rainfall duration but also on the rainfall pattern. Among the four representative rainstorm patterns, the delayed rainstorm has the greatest rainfall duration threshold for landslide occurrence, followed by the central rainstorm, and then the uniform rainstorm. In addition, for each rainstorm pattern, the corresponding rainfall duration threshold for landslide occurrence decreases with the increase of rainfall amount, and seems to be constant for large rainfall amount.     

The chaotic characteristics of landslide evolution: a case study of Xintan landslide

A new method based on the chaos theory is used to assess the evolution process of a slope system. The method is applied to the Xintan landslide and the results show: (1) the slope movement is a complex process of the slope going in and out of the stable and chaotic state; (2) the method reveals the evolution process of the slope pointing to the slope failure while the observed movement shows a simple monotonic increase with time; (3) the method is not sufficiently mature to precisely predict the time of failure but it has potential for improvement with further research and more field data for analysis.     

金沙江结合带高位远程滑坡灾害链式特征遥感动态分析

金沙江结合带由于地质构造发育,地震活动频繁,河谷切割强烈,岸坡高陡狭窄, 岩体极为破碎,历史上发生过多起大型滑坡堵江事件。以白格滑坡两次堵江事件（2018年10月11日、2018年11月3日）为例,采用2009年12月4日至2020年10月16日多期、多源卫星遥感数据源,通过遥感判识、对比分析等方法对滑坡体滑前斜坡变形特征、滑后滑坡堆积特征、滑后斜坡残留体变形特征进行特大型堵江滑坡链式特征遥感动态分析。根据多期遥感影像,将白格滑坡变形特征划分为早期滑动变形阶段（2009—2011年）、稳定变形阶段（2011—2015年）、快速变形阶段（2015—2017年）、剧烈变形阶段（2017—2018年）、变形破坏阶段（2018年以后）等5个阶段。根据滑坡第一次滑后的变形破坏特征,将滑坡划分为滑源区、铲刮区、堆积区以及拉裂变形区。根据滑坡第二次滑后的变形破坏特征,将滑坡划分为二次滑坡滑源区、二次滑坡堆积区（堰塞体）、二次铲刮（堆积）区、二次铲刮区影响区以及拉裂变形区。基于上述研究成果,对白格滑坡灾害链式特征进行总结分析,为金沙江结合带高位远程滑坡灾害链式特征研究提供参考。     

Impact of predicted climate change on landslide reactivation: case study of Mam Tor, UK

Global change is expected to result in worldwide increases in temperature and alteration of rainfall patterns. Such changes have the potential to modify stability of slopes, both natural and constructed. This paper discusses the potential effect of global climate change on reactivation of landslides through examination of predicted changes in rainfall pattern on the active landslide at Mam Tor, Derbyshire, UK. This landslide is of Pleistocene origin and is crossed by a road that is now abandoned. Damaging winter movement is known to occur when precipitation reaches both 1-month triggering and 6-month antecedent thresholds. Return periods for threshold exceedence is modelled statistically, and the climate change data from the UKCIP 2002 report (Hulme et al. 2002) is applied to this model. For the predicted changes in precipitation, it is shown that the instability threshold could decrease from 4 to 3.5 years by the 2080s for the medium–high climate change scenario. However, predicted temperature changes could influence the response of the landslide through increased evapotranspiration leading to a change in the triggering precipitation thresholds, and this will help counter the impact of changes in precipitation. Analysis of sources of uncertainty in the model has been used to establish the factors that contribute to the predicted changes in stability. Assessment of these factors can provide an indication of the potential impact of climate change on landslides in other areas of the UK.     

Centrifuge modelling of landslides and landslide hazard mitigation: A review

Landslides are serious geohazards that occur under a variety of climatic conditions and can cause many casualties and significant economic losses. Centrifuge modelling, as a representative type of physical modelling, provides a realistic simulation of the stress level in a small-scale model and has been applied over the last 50 years to develop a better understanding of landslides. With recent developments in this technology, the application of centrifuge modelling in landslide science has significantly increased. Here, we present an overview of physical models that can capture landslide processes during centrifuge modelling. This review focuses on (i) the experimental principles and considerations, (ii) landslide models subjected to various triggering factors, including centrifugal acceleration, rainfall, earthquakes, water level changes, thawing permafrost, excavation, external loading and miscellaneous conditions, and (iii) different methods for mitigating landslides modelled in centrifuge, such as the application of nails, piles, geotextiles, vegetation, etc. The behaviors of all the centrifuge models are discussed, with emphasis on the deformation and failure mechanisms and experimental techniques. Based on this review, we provide a best-practice methodology for preparing a centrifuge landslide test and propose further efforts in terms of the seven aspects of model materials, testing design and equipment, measurement methods, scaling laws, full-scale test applications, landslide early warning, and 3D modelling to better understand the complex behaviour of landslides.     

Implementing low-cost landslide risk reduction: a pilot study in unplanned housing areas of the Caribbean

Landslides pose a serious physical and environmental threat to vulnerable communities living in areas of unplanned housing on steep slopes in the Caribbean. Some of these communities have, in the past, had to be relocated, at costs of millions of dollars, because of major slides triggered by tropical storm rainfall. Even so, evidence shows that: (1) risk reduction is a marginal activity; (2) there has been minimal uptake of hazard maps and vulnerability assessments and (3) there is little on-the-ground delivery of construction for risk reduction. This article directly addresses these issues by developing a low-cost approach to the identification of the potential pore pressure changes that trigger such slides we seek to address these three commentaries directly. A complex 45–60° slope site in St Lucia, West Indies was selected as a pilot for a modelling approach that uses numerical models (FLAC and CHASM) to verify the need for surface water management to effectively reduce landslide risk. Following the model confirmation, a series of drains were designed and constructed at the site. Post-construction evidence indicates the methodology to be sound, in that the site was stable in subsequent 1-in-1 to 1-in-4 year rainfall events. A critical feature of the approach is that it is community-based from data acquisition through to community members participating in construction.     

Landslide Hazard Zonation using Remote Sensing and GIS: a case study of Dikrong river basin, Arunachal Pradesh, India

Landslides are among the most costly and damaging natural hazards in mountainous regions, triggered mainly under the influence of earthquakes and/or rainfall. In the present study, Landslide Hazard Zonation (LHZ) of Dikrong river basin of Arunachal Pradesh was carried out using Remote Sensing and Geographic Information System (GIS). Various thematic layers namely slope, photo-lineament buffer, thrust buffer, relative relief map, geology and land use / land cover map were generated using remote sensing data and GIS. The weighting-rating system based on the relative importance of various causative factors as derived from remotely sensed data and other thematic maps were used for the LHZ. The different classes of thematic layers were assigned the corresponding rating value as attribute information in the GIS and an “attribute map” was generated for each data layer. Each class within a thematic layer was assigned an ordinal rating from 0 to 9. Summation of these attribute maps were then multiplied by the corresponding weights to yield the Landslide Hazard Index (LHI) for each cell. Using trial and error method the weight-rating values have been re-adjusted. The LHI threshold values used were: 142, 165, 189 and 216. A LHZ map was prepared showing the five zones, namely “very low hazard”, “low hazard”, “moderate hazard”, “high hazard” and “very high hazard” by using the “slicing” operation.     

Regionalization of rainfall thresholds: an aid to landslide hazard evaluation

 Rainfall, soil properties, and morphology are major factors controlling shallow landsliding. A series of meteorological events that triggered soil slips in northern Italy were studied to define rainfall thresholds and to evaluate a possible regionalization. Soil properties, triggering rainfall, and local lithological and morphometrical settings of different sites were used as input to an infiltration model. The approach allows the recognition of several triggering conditions in the Piedmont, Pre-Alpine and Alpine regions. This suggests the need for different rainfall thresholds with respect to those derived with other methods. Intensity versus rainfall duration relationships become particularly important when related to soil permeability and thickness, and demonstrate the role of antecedent precipitation. Events with exceptional water discharge from obstructed road culverts reveal the role played by anthropic structures in triggering such phenomena. Different approaches to slope stability analysis are shown, taking into account bedrock lithology, topography, seepage, and local saturation conditions. Received: 23 October 1997 · Accepted: 25 June 1997     

坡地地质灾害的减灾策略——以降雨预警基准为例

降雨是诱发坡地地质灾害的重要原因,因此掌握降雨的趋势与分布规律,可有效地用于坡地灾害预警,但由于降雨预测精度、灾害资料统计的不足与坡地地质条件的不确定性,实际应用降雨预警基准仍存在许多困难。通过分析台风诱发坡地地质灾害的降雨特性,来说明降雨预警基准在防灾减灾工作上应用的条件与限制。结果表明,对于不同类型之坡地灾害与降雨分布特性,需采用不同的雨量预警基准。唯有通过岩土力学、工程地质学与气象学的整合研究,才能有效提高降雨预警基准预测的准确率,因此各学科的整合是未来防灾减灾研究工作的发展趋势。     

The role of rainfall in the landslide hazard: the case of the Avigliano urban area (Southern Apennines, Italy)

Mass movements varying in type and size, some of which are periodically reactivated, affect the urban area of Avigliano. The disturbed and remoulded masses consist of sandy–silty or silty–clayey plastic material interbedded with stone fragments and conglomerate blocks. Five landslides that were markedly liable to rainfall-associated instability phenomena were selected.

The relationships between landslides and rainfall were investigated using a hydrological and statistical model based on long-term series of daily rainfall data. The model was used to determine the return period of cumulative daily rainfall over 1–180 days. The resulting hydrological and statistical findings are discussed with the aim of identifying the rainfall duration most critical to landslides.

The concept of a precipitation threshold was generalized by defining some probability classes of cumulative rainfall. These classes indicate the thresholds beyond which reactivation is likely to occur. The probability classes are defined according to the return period of the cumulative rainfall concomitant with landslide reactivation.     

Landslide hazard zonation by deterministic analysis (Veľká Čausa landslide area, Slovakia)

A practical application of a simple and economical solution to landslide hazard zonation based on slope stability analysis was carried out in the Veľká Čausa landslide, Horná Nitra region, central Slovakia. The region is prone to different types of slope deformation controlled by geological structure, physical and mechanical properties of materials, complicated hydrogeological setting, undulating morphology, and man-made influence. Taking into consideration the cause of the landslide, identified as groundwater change, two scenarios of landslide activity have been investigated. Scenario 1 considers the maximum groundwater level recorded from March 1995 to October 1998, corresponding to the period starting from the most recent landslide activity up to the end of remediation work. Scenario 2 considers the maximum groundwater level recorded from November 1998 to December 2004, after the remediation works, and corresponding to the actual situation of the landslide. It has been found from this study that slope angle has the highest influence on landslide instability in the Veľká Čausa landslide. Therefore, high resolution Digital Elevation Model (DEM) is essential for obtaining reasonable results. In addition, an appropriate selection of the model input parameters (e.g., shear strength) is very important. The validation between the calculated landslide hazard zonation map and results of monitoring survey were examined. The results show moderate to good agreement with the inclinometric and geodetic measurements. It was also verified that the most active part of the landslide is the north-western side.     

Slope stability analysis on a regional scale using GIS: a case study from Dhading,Nepal

A spatially distributed physically based slope stability model combined with a hydrological model is presented and applied to a 350-km² area located in Dhading district, Nepal. Land slide safety factor maps are generated for five cases, including three steady state conditions assuming either completely dry soils, half saturated soils, or fully saturated soils, and two quasi-dynamic conditions, i.e. soil wetness resulting from storm events with, respectively a 2 or 25-year return period. For the quasi-dynamic cases, two methods are used, one based on accumulation of groundwater flow from upstream areas, and the other on accumulation of soil water from direct infiltration. The methodology delineates areas most prone to shallow land sliding in function of readily available data as topography, land-use and soil types. For the study area only 29% of the soils are unconditionally stable, while 25% of the soils are found to be unstable under fully saturated conditions. The comparison between the methods based on contributing area or on infiltration for quasi-dynamic conditions show that the approach based on infiltration is more reliable for the study area. The proposed methodology for predicting landslide susceptibility on a regional scale, based on basic data in GIS form, may be useful for other remote regions where detailed information is not available.     

An historical review of landslide research in the South Wales coalfield

Summary The areal density of landslides in the coalfield of South Wales is one of the highest in the UK. During the past 100 years landsliding has had considerable impact, causing structural damage and loss of life. Most of the landslides were initiated under periglacial conditions but many became reactivated due to the activities of humans, particularly during the late 19 th century when widespread urban and industrial development commenced in the Welsh valleys. A number of the area's larger landslides are first-time slides which occurred during the past 100 years. This paper sets out to chart the history of landslide research in the coalfield, which began through work by mining engineers.     

三峡水库区万州独生基滑坡稳定性分析

独生基滑坡位于重庆市万州区长江右岸。为百安坝斜坡松散堆积层沿下伏软弱层面滑动的滑坡体。属于降雨及地表生活排水诱发、人类工程活动加剧变形而形成的新滑坡。论文在分析和研究滑坡区地质环境背景、平剖面形态、特征及诱发因素的基础上,采用传递系数法计算了滑坡体各工况及荷载组合条件下的稳定系数。通过计算,滑坡在天然状态、加载及暴雨条件下均处于不稳定状态。最后根据滑坡特征、主要诱发因素及其稳定性,针对滑坡体失稳特征,通过防治方案对比,初步拟定以抗滑桩工程进行治理,以保证滑坡体的稳定。     

The application of GIS-based bivariate statistical methods for landslide hazards assessment in the upper Tons river valley,Western Himalaya,India

Landslides are one of the most frequent and common natural hazards in many parts of Himalaya. To reduce the potential risk, the landslide susceptibility maps are one of the first and most important steps in the landslide hazard mitigation. Earth observation satellite and geographical information system-based techniques have been used to derive and analyse various geo-environmental parameters significant to landslide hazards. In this study, a bivariate statistics method was used for spatial modelling of landslide susceptibility zones. For this purpose, thematic layers including landslide inventory, geology, slope angle, slope aspect, geomorphology, slope morphology, drainage density, lineament and land use/land cover were used. A large number of landslide occurrences have been observed in the upper Tons river valley area of Western Himalaya. The result has been used to spatially classify the study area into zones of very high, high, moderate, low and very low landslide susceptibility zones. About 72% of active landslides have been observed to occur in very high and high hazard zones. The result of the analysis was verified using the landslide location data. The validation result shows significant agreement between the susceptibility map and landslide location. The result can be used to reduce landslide hazards by proper planning.