Two-dimensional numerical simulation of flash floods in watershed from LIDAR point cloud data

To analyze the formation of confluence on a slope due to storm floods in Baogaisi, a small watershed in Hunan Province, a two-dimensional hydrodynamic model was constructed from high-precision LIDAR point cloud data．The hydrodynamic model was used to simulate flood events in 2012．The simulation was compared with the hydrological simulation, and the actually measured data．To solve the problem of large number of grids and slow computing speed, GPU parallel algorithm was applied to the model．It was found that with high-resolution topographic data, the rainfall runoff process on the slope of small watershed could be simulated rather well, obtaining the flood convergence process in the whole basin．The hydrodynamic simulation was in good agreement with the hydrological simulation, and with the measured data．Peak time error and flood peak error as calculated by the hydrodynamic model were found to be 1 h and 23% respectively．The hydrodynamic model could be applied to high resolution terrain data．The use of GPU parallel algorithm was found to improve computation efficiency by 50 times, shortening the calculation time significantly．This model could be used for forecasting, warning and three-dimensional deduction of storm floods．