Assessment of flash flood vulnerability zonation through Geospatial technique in high altitude Himalayan watershed, Himachal Pradesh India

Himachal Pradesh is in the western part of the Indian Himalaya which is environmentally fragile and susceptible to natural disasters. Flash flood disaster is a major problem in the state due to its diverse topography combined with meteorological and morphological conditions. In the present study, detailed terrain information was used to identify the causes of natural disaster. Remote Sensing data such as Landsat 8 satellite data and ASTER (DEM) coupled with geological and geomorphological data were utilized in a Geographical Information System (GIS) environment for the estimation of flash flood risk in 20 sub-watersheds of Beas valley. Morphometric analysis was used to estimate the flash flood risk levels of sub-watersheds. Drainage characteristics, slope, and wetness index were analyzed by a set of parameters relevant to flash flood risks. All the sub-watersheds were assigned with a rank according to the compound value analyzed for all the given parameters. After analysis of compound values, it was observed that an area of 555 km2 which is 47% of the total area was in very high priority and very highly susceptible to the flash flood occurrences. In the entire watershed, more than 90% of the total area was found to be highly vulnerable to flash floods. Such zonations using RS/GIS can assist policymakers in taking appropriate and timely measures for the reduction of flash floods. This can initiate appropriate corrective measures and reduce the risk of heavy loss of life and property.