Regional-scale landslide susceptibility assessment for the hilly state of Himachal Pradesh, NW Himalaya, India

Himachal Pradesh (HP), one of the 11 states of the Indian Himalayan Region, has a prolonged history of landslides and related mass-movement activities. In recent years, landslide incidences have increased significantly in the state due to changing climatic patterns and enhanced anthropogenic interventions. Therefore, to understand the spatial distribution of landslide-prone zones, regional-scale landslide susceptibility mapping for the entire state has been carried out using two bivariate methods, i.e. weight of evidence and information value. The results depict that 25-30% of the total area of the state is confined in the high to very high landslide susceptible (LS) zones. These are dominantly confined to three regions: Kinnaur, Lahaul, Chamba and upper Kangra. It is also ascertained that a higher percentage of high and very high LS zones are located at an elevation of 2000-4000 m and on the slopes facing south with an inclination >40 degrees. Moderate and low to very low LS zones comprise similar to 27% and similar to 43-48% of the total area respectively, and are confined to the Outer and Lesser Himalaya. These maps were validated using the success rate curve and prediction rate curve, indicating that both models have more or less similar efficiency and accuracy.