Reconstruction of the July 12, 2022, flash flood event in Southwest China: integrating emergency management analysis with hydrological modeling

A devastating flash flood hit southwestern China on July 12, 2022, causing 18 fatalities in the Heishui River watershed of Pingwu County, Sichuan Province. Because global climate change and various human activities exacerbate flash flood damage, it is important to apply lessons from typical flood events to inform prevention, mitigation, and emergency strategies. This study used disaster site investigations and hydrological–hydrodynamic simulations to reconstruct the flooding process and response behaviors. Heavy rainfall in the upstream watershed was the direct cause of the flash flood. Indirect causes included the presence of built-up areas in the downstream estuary floodplain, coupled with limited flood risk perception and early warning capabilities in the mountainous regions, leading to slow emergency responses. This case study addresses flash flood modeling challenges in ungauged watersheds by demonstrating how post-disaster field investigations and historical flood mark data provide reliable validation to reproduce flood processes and inform prevention strategies.