Geological data of Nepal's Gorkha Earthquake 2015 affected area

Large landslide dams are one of the most disastrous natural phenomena in mountainous regions all over the world Such dams are formed most commonly in tectonically active settings where high mountains border narrow and steep valleys and earthquakes occur frequently. Landslide dams are very diverse in terms of their formation, geotechnical characteristics, longevity, stability, and flood hazard. The two major causes of landslide dam formation are precipitation and earthquake. About 50% of dam-forming landslides are brought about by rainstorms and snowmelts, 40% by earthquakes, and 10% by other factors Geometry of valley in relation to geometry and volume of debris and discharge of damming river are some of the factors which are responsible for the development of landslide dams. Schuster et al. (1998) mentioned four groups of governing factors responsible for the spatial distribution of landslide dams. They are i) seismic intensity, ii) slope gradient and topography, iii) lithology and weathering properties, and iv) soil moisture and groundwater content. Landslide dams are generated by various types of mass movements, which range from rock falls and rockslides in steep walled, narrow canyons to earth slumps in flat river lowlands. Managing landslide-dam hazards requires an understanding of the temporal and spatial scales on which such phenomena occur. Many previous works on landslide dams have been mainly descriptive in character, and have produced a multitude of documented case studies and inventories (e.g. Costa and Schuster, 1988; Costa and Schuster, 1991). More recent work is focused on quantitative methods of determining the post-formation development, in particular, the controls on dam longevity.

大型滑坡坝是全球山地范围内极具破坏性的自然现象之一。此类坝体最常形成于构造活跃区域——该区域多为高山毗邻狭窄陡峭河谷，且地震活动频发。滑坡坝在成因、岩土特性、存续寿命、稳定性以及洪水风险等方面均表现出极强的多样性。滑坡坝形成的两大主要诱因为降水与地震：约50%的成坝滑坡由暴雨与融雪引发，40%由地震触发，剩余10%则源于其他因素。河谷形态与碎屑物几何特征、体积以及壅塞河道的径流量等，均为影响滑坡坝发育的关键因素。舒斯特（Schuster）等学者（1998年）提出了四类控制滑坡坝空间分布的主导因素：分别为①地震烈度；②坡度与地形地貌；③岩性与风化特性；④土壤含水率与地下水含量。滑坡坝由多种类型的块体运动形成，涵盖陡峭狭窄峡谷区域的岩崩与岩石滑坡，乃至平坦河谷低地的土体滑坡。对滑坡坝灾害的防控，需建立在对该类现象发生的时空尺度的认知基础之上。过往诸多关于滑坡坝的研究多以描述性为主，催生了大量记录完备的案例研究与编目数据集（如科斯塔（Costa）与舒斯特（Schuster），1988；科斯塔（Costa）与舒斯特（Schuster），1991）。而近期的研究则聚焦于成坝后演化过程的定量分析方法，尤其是针对坝体存续寿命的控制机制。