Research on precipitation characteristics and dynamic critical thresholds of flash flood disasters

Serious harms of flash flood can be caused by heavy precipitation. Based on flash flood disasters, soil moisture information and the historical precipitation data, etc. from January 2013 to December 2016, the temporospatial distribution characteristics of precipitation and flash flood over China and in several typical regions (Yunnan Province, Guizhou Province, Sichuan Province and Chongqing Province) are preliminarily analyzed. The method of static critical precipitation of flash flood is developed by establishing the relationship between flash flood events and precipitation at different time-scales (1 h, 6 h, 12 h and 24 h) before each flash flood event. Combined with the characteristics of the relative soil moisture in different layers (10~50 cm) at different time period before disasters, the dynamic critical precipitation threshold is calculated as well. The dynamic critical precipitation threshold model of flash flood in national and regional domains is proposed in the paper. The results show that the models perform well, and the hit ratio of the dynamic model reaches 73%, which is better than the static model.