Simulation Outputs of Major Debris Flows in Garhwal Himalaya: A Geotechnical Modeling Approach for Hazard Mitigation

Landslides, one of the major geological hazards, contribute to natural disasters in mountainous region around the globe owing to a wide variety of causative as well as triggering factors like heavy rainstorms, cloudbursts, glacial lake outburst (GLOF), earthquakes, geo-engineering setting, unplanned human activities, etc. In different parts of the Himalaya, landslide has evolved as a frequent problem which severely affects life, property, and livelihood of this mountainous area thriving mainly on pilgrimage, tourism, and agriculture (Anbalagan et al. 2015; Anbalagan 1992; Champati Ray and Chattoraj 2014; Gupta et al. 1993; Kumar et al. 2012; Onagh et al. 2012; Sarkar et al. 1995, 2006; Sundriyal et al. 2007). With the background of higher elevation, rough hilly landscape, scanty cultivated land, strong monsoonal effect, and less industrial growth restricting economic progress, repeated landslide events keep human life and property at stake (Champati Ray et al. 2013a, b, 2015; Ketholia et al. 2015; Paul and Bisht 1993). Landslides in the Himalayan region are on an average smaller in dimension and have shallow depth, but these are more recurring in nature and thereby do not get noticed by authorities but cause higher cumulative losses over a period of time. Landslides, in the Himalaya, are observed particularly in highly fractured and sheared rock mass close to faults and also in weathered hard rocks. The climatic factors play an important role in weathering and disintegration of rock mass that are finally brought down by gravity (Kumar et al. 2007, 2012). Most of these landslides wreak havocked not only on life and property but manifest changes in landform due to large-scale mass wasting, landslide-dammed lake formation, and breaching leading to large-scale landform modification (Champati Ray 2013; Champati Ray et al. 2015).