LIU Changjun, WEN Lei, ZHOU Jian, ZHAO Xuantao, GUO Liang and WEI Yongqiang

Abstract: For the fine simulation of flash flood in small watersheds,this paper proposes a spatial and temporal source-variable mixed runoff model in small watershed, and builds a distributed simulation model of stormwater flash flood with small watershed as the unit, The visual distributed hydrological model software FFMS and hydrodynamic calculation software FHMS are developed. Taking the calculation of the storm flood in the small watershed of Baogai Temple as an example, the hydrological and hydrodynamic methods were used respectively to calculate the storm flooding process in the small watershed,and analyzed the calculation accuracy, efficiency and practicability of the two methods. The results of the case study show that:First, hydrological and hydrodynamics can simulate the stormwater flash flood in small watershed, and the simulation results are basically consistent with the actual measurements; Second, for calculation of storm floods in ungauged small watersheds,the hydrological modeling has faster modeling speed and higher computational efficiency compared with hydrodynamic method modeling;Third,when dealing with the formation mechanism and evolution process of storm floods under complex terrain conditions, the hydrodynamic calculation results are more precise and accurate; For flood forecasting and warning in small and medium watersheds in mountainous areas,the hydrological method is more practical.

Keywords: flash flood; spatio-temporal variable source mixed flow production model; modular distributed hydrological model; hydrodynamic method; flash flood simulation