On 5 August 2025, Dharali town (Uttarkashi district, Uttarakhand, India) experienced a devastating mudslide–flash flood sequence triggered by an intense localized rainfall event associated with the southwest monsoon. Rapid mobilization of morainic and glacio-fluvial debris in the Kheer Gad catchment produced a high-velocity flow (~ 43 km h⁻ 1 ), destroying over 148 buildings, causing four fatalities, depositing a ~ 20 ha debris fan at the Kheer Gad–Bhagirathi confluence, and disrupting key transport routes. The event reflects the interaction of fragile Himalayan geology, steep paraglacial terrain, and evolving climatic drivers. Preliminary assessments indicate multiple potential triggers, including reactivated landslides, glacier- or lake-breach mechanisms, atmospheric moisture convergence from the Arabian Sea–Bay of Bengal systems, and anthropogenic interventions. A northward shift of the Inter-Tropical Convergence Zone likely enhanced moisture transport and convective rainfall intensity. Geologically, the Higher Himalaya’s fractured crystalline bedrock, thick debris mantles, and active tectonics predispose slopes to failure. Human activities such as road widening, blasting, tunneling, deforestation, etc. have further destabilized slopes. The Dharali disaster underscores the compounded hazard created by unstable geomorphology, climate-driven extreme rainfall, and poorly regulated infrastructure. Hazard mitigation requires geoscience-based land-use planning, avoidance of active debris flow corridors, and strict control of excavation, blasting, and vegetation loss in paraglacial terrain.
Ratan Das (Wed,) studied this question.