Landslide hazard zonation mapping of Tapovan - Helong hydropower project area, Garhwal Himalaya, India, using univariate statistical analysis

Abstract

Landslide hazard zonation mapping of Tapovan - Helong area of Garhwal Himalaya, where a hydropower scheme of 520 MW is proposed on Dhauli Ganga was carried out. The study area lies in the Main Central Thrust (MCT) zone, which receives majority of the southwest summer Monsoon. The study area belongs to Central Crystalline zone consisting of medium to high grade-quartz-plagioclase-muscovite-biotite-garnet-kyanite and sillimanite bearing crystalline rocks. In the present study statistical analysis of various geo-environmental factors such as the lithology, slope, structure, relative relief, landuse and hydro-geological conditions were used. For preparing the landslide hazard zonation map a quantitative approach called landslide hazard evaluation factors (LHEF) rating has been used. The study indicates that structures, peri-glacial material resting on steeper angle of hill slopes and rainfall plays major role in triggering landslides in this part of the Himalaya. The main aim of this study was to select the best locations for the construction of barrage and sedimentation tank, selections of sites for the tunnels portal and the switchyard area and finally appropriate slope stabilization measures were also suggested. The study further suggests that in the investigation stage for river valley projects, landslide hazard evaluation factor (LHEF) rating scheme can provide rapid hazard assessment in a mountainous terrain.