Identification and quantitative analysis of flash flood risks for small catchments in China: a new operational modelling approach

Abstract

Under the influence of multiple factors, such as extreme weather conditions and human activities, flash flood disasters occur frequently in China and are very difficult to predict and anticipate. Based on the national flash flood disaster investigation and assessment project, this article focuses on small (10–50 km2) catchments and extracts 83 alternative indicators from the perspectives of rainfall, underlying surfaces, present social and economic conditions, flood control capacity, wading engineering, and monitoring and early-warning facilities. A dimension reduction processing is conducted using a principal component analysis, and 10 core and independent indicators are obtained. A risk evaluation indicator system is proposed that establishes the risk cube model, which is verified with data from 53,235 historical flash flood events in China from 1949 to 2018. The results show that flash flood risk identification based on small watersheds may effectively reflect the disaster response relationship based on rainfall and the underlying surface. In addition, 91% of historical flash floods occurred in high-, medium-, and low-risk areas, and the occurrence density in high-risk areas was double of that in low-risk areas. These evaluation results provide data support for the accurate defence, forecasting and early warning of flash flood disasters in China.

Keywords

• Flash flood disasters
• principal component analysis
• risk identification
• risk cube
• small catchment
• Catastrophes d'inondation éclair