Surface runoff simulation and application using WRF-Hydro for city flood in China

WRF-Hydro is a coupled model which integrates the Weather Research and Forecast (WRF) and components of terrestrial hydrological models. WRF-Hydro has modularized component model coupling interfaces for many typical terrestrial hydrological processes such as surface runoff, channel flow, lake/reservoir flow, sub-surface flow, land-atmosphere exchanges. Therefore, it is possible used for the surface runoff simulation and forecast, which is a potential usage for the city flood. In this work, a case study of the precipitation and surface runoff simulation is performed for Beijing heavy rainfall on 21th July 2012. This heavy rainfall event has more than 200mm rainfall during 24-h and caused serious flood in center downtown area and killed on people due to the heavy depth of surface water. It also caused a big mud-rock flow in Fangshan district of Beijing in mountain area. Using WRF-Hydro for the city flood forecast is an initial effort to explore the possibility of establish the city alert flood system. Our study shows that based on the high resolution and good precipitation simulation, it is possible to have a reasonable surface runoff simulation. The resolution of weather model and topography have significant impact on the surface runoff amount simulation.