Characteristics of rain-induced landslides in the Indian Himalaya: a case study of the Mandakini Catchment during the 2013 flood

Landslides triggered by monsoon rainfall are a recurring hazard that lead to loss of life and cause enormous property and infrastructure damage in the Indian Himalaya. This study is focused on understanding the role of extreme rainfall and physical factors in causing landslides in the Indian Himalaya, particularly in the Mandakini Catchment where an enormous landslide and flood disaster occurred in June 2013 following a two-day extreme rainfall event. Results indicate that sub-daily extreme rainfall depths causing landslides vary with elevation across the catchment. Antecedent rainfall six days prior to the extreme rainfall event was found to have substantial depths that could have primed the area for landslides. Except for aspect of slopes, the causative factors including land use/land cover, lithology, elevation, slope, river network, distance to roads, and total extreme rainfall as a triggering factor were found to be statistically significant in causing landslides in the catchment. The final product of the study is a new landslide susceptibility map that better delineates the landslide prone regions in the disaster-prone Mandakini Catchment after the June 2013 extreme rainfall event. The Map was prepared using logistic regression that shows medium and high susceptibility zones at upper sections of the catchment as well as along the Mandakini River and its tributaries where major sacred shrines, tourist spots and human establishments are located