Preliminary Assessment of Flash Flood and Debris Flow at Chashoti, Kishtwar, Northwest Himalaya

ABSTRACT The North West Himalaya, characterized by its unique topography and climate, is increasingly becoming susceptible to extreme hydrometeorological events, particularly cloudbursts. On the day of 14 August, 2025, Chashoti village of Kishtwar district in Jammu and Kashmir experienced a localized event in which more than 70 people lost their lives and around 32 are still missing besides the huge loss of property and damage to geoenvironment. This study seeks to understand the nature of this event, its drivers, and the interrelationships among meteorological, geomorphic, and geological factors that led to a high-intensity flash flood in the Chashoti nala (streamlet). The terrain characteristics observed through satellite imageries, rainfall data and field assessment highlight the complex interaction between atmospheric trigger, local geomorphic and geological setup. The field visit upstream of Chashoti village along the nala demonstrates that the cloudburst occurred around 8 km upstream. The left bank of the nala has deposited a large sediment load into the Chashoti nala, thereby being the source of the flash flood. Huge sediments were contributed to the Chashoti nala by the lower order stream joining from the left bank due to active landslides and debris material. This debris material with a significant amount of water has gained momentum due to the steep gradient, further 2km downstream from the zone of origin of the flash flood. The stream channel analysis suggests a drop of 40m in altitude within 1km upstream of Chashoti village. This prominent geomorphic feature, coupled with continuous sedimentation from landslides along the nala banks and damming at places for short intervals, increased the kinetic energy of debris-laden flash floods, making this a destructive natural disaster. Based on the terrain characteristics, we conclude that the Chashoti nala catchment, like many fragile Himalayan watersheds, is prone to extreme hydro-meteorological events that caused widespread geomorphic changes, slope instability, and damage to human settlements in the form of similar extreme events in the past.