Drivers of flash floods in the Indian sub-continental river basins

Abstract

Flash floods occur every year during the summer monsoon season in India, causing substantial damage to agriculture, infrastructure, and human life. Despite their profound implications, flash flood hotspots remain unknown, hindering adaptation efforts. Here, we use hydrological and geomorphological characteristics to map the flash flood prone sub-basins in the Indian sub-continent. Flash flood hotspots are mainly centered in Himalayas, West Coast, and Central India, with geomorphological factors driving flash floods in the Himalayas and hydrological factors (flashiness) in the West Coast and Central India. The combination of extreme precipitation and wet antecedent conditions trigger most (~ 3/4th) flash floods while the remaining (~ 1/4th) are solely driven by extreme precipitation. Several non-flash flood prone basins have experienced a significant increase in extreme precipitation frequency and intensity, highlighting that the warming climate can lead to newer flash flood hotspots in the future.