Abstract
Flash floods are becoming annual events in various Himalayan valleys (India). This study aims to identify and delineate the flash flood hazard-prone landforms and terrain features as unsuitable areas for setting up new habitations and also reveals the risk posed to the existing human habitations in such hazardous areas. Enhancing resilience to cope with the extreme rainfall-induced Himalayan flash floods calls for developing a thorough understanding of the terrain, followed by the safe siting of new habitations and reducing the risk to the existing ones. This study delves into the survey of flash flood-prone landforms through various means, namely, available past records and/or historical records on locations of past flash flood incidents, followed by the examination of satellite images, available topographical maps, and field investigations. The major finding of this study is the identification of flash flood-prone Himalayan landforms, namely, lower terraces of rivers, alluvial cones (drained by perennial or dry streams), flow lobes or the downslope areas of debris flows or flow slides, solifluction lobes, and abandoned channels. Anthropogenic actions, namely, constructions within the floodplains of hill rivers, blocking or diverting the course of even small seasonal drains, have been identified as risk enhancers. The investigation highlights the avoidance of these flash flood risk-prone landforms for setting up new habitations or even for new constructions in parts of Bhagirathi, Yamuna, Mandakini, and Pinder valleys of Uttarakhand Himalaya. The disaster management strategy elaborated for coping with Himalayan flash floods proposes a national program on extreme climatic event-induced flood forewarning and emphasizes the need for developing a robust system for the dissemination of flash flood warnings. Capacity building of village disaster management committees and mechanisms for the rehabilitation of hamlets of villages located in the high-risk zones, strict adherence to the land use regulations, and training of vulnerable communities of high-risk areas in reading signs of extreme rainfall-induced flash floods have also been discussed. Identification of extreme rainfall-induced flash flood-prone landforms and discouraging them as sites for human settlements is the new finding of this study. The signs of extreme rainfall-induced flash floods elaborated in this study can be relied upon to a limited extent only because the time window between extreme rainfall and consequent flash floods or debris flow slides is so narrow that it hardly leaves much time for emergency evacuation of the immediate downstream area. Overall, an attempt has been made toward evolving a holistic approach for advising the dos and don'ts for developing resilience to extreme rainfall-induced hazards in the Himalayan region through the combined efforts of all the stakeholders, including the scientific fraternity, disaster managers, and the community. The dos and don'ts discussed in this article will also help develop resilience to similar types of disasters in other parts of the country, including in the other hill states of the Himalaya and the Arakan mountains, and also in the Western Ghats of India, which have witnessed catastrophic debris mud flows on July 30, 2024.