Assessment of 2025 cloudburst-induced flash flooding in Thunag village, Mandi, Himachal Pradesh, India

Cloudburst-induced flash floods are among the most destructive hydro-meteorological hazards in the Himalayas, yet their localized nature makes them difficult to assess using sparse ground observations. This study investigates the June 29–July 1, 2025 cloudburst-induced flash flood in Thunag village, Himachal Pradesh, using an integrated remote sensing and hydrodynamic modelling framework. Half-hourly Global Precipitation Measurement Integrated Multi-satellite Retrievals (GPM IMERG) rainfall, high-resolution topographic data, mapped building footprints, and post-disaster field observations were integrated with the two-dimensional HEC-RAS 6.7 Rainfall-on-Topography model to reconstruct flood inundation and evaluate building-level impacts. GPM IMERG captured the spatiotemporal evolution of the localized cloudburst, while simulations reproduced rapid runoff concentration, high flow velocities, and severe channelized flooding associated with floodplain encroachment. Validation against 215 building footprints from the Himachal Pradesh Government Post Disaster Needs Assessment survey achieved 95.34% accuracy, demonstrating excellent agreement with observed building damage under data-scarce conditions. The integrated framework also estimated direct economic losses of INR 6.2–7.8 crore. These findings demonstrate the effectiveness of combining satellite precipitation, hydrodynamic modelling, and field validation for rapid post-disaster assessment and support the wider application of integrated remote sensing frameworks for flood risk management in data-scarce mountainous regions.