A Comprehensive Flash Flood Risk Assessment Framework for Mountainous Regions: A Case Study in Chongqing, China

Quantitative risk assessment of flash floods is crucial for developing disaster prevention and mitigation strategies. This study developed a refined framework that innovatively integrates field-validated data from Chongqing’s flash flood disaster investigation project with AHP, factor analysis, and cluster analysis to quantify hazard, vulnerability, resistance, and risk indicators at a 30 m grid. Unlike existing coarse-scale assessments that rely on generic indicators, this hybrid model, calibrated by observed disaster evidence, significantly enhanced the local relevance and reliability of risk zoning. The validity of this framework was confirmed through validation against objective weighting methods and historical flash flood locations. The results indicated that the risk value of flash floods in Chongqing was between 0.24 and 0.69, with extremely high-risk and high-risk zones covering 42,388 km2 (51.47%) of the study area. This accurately identifies areas at high risk of flash floods and provides a basis for government decision-making regarding priority areas for disaster risk reduction investments. Verification showed that 83.44% of historical disaster points fall within medium-risk or above zones, confirming the framework’s accuracy in identifying flood-prone hotspots and providing actionable support for targeted early warning and resource allocation.