Study on Two-Dimensional Numerical Simulation of Rainstorm and Torrent in Small Watershed Based on Lidar Data

Abstract

To analyze the process and mechanism of slope confluence of rainstorm and flood in small watersheds, a two-dimensional hydrodynamic model was built based on high-precision lidar data of point cloud and the field flood process of the Baogaisi watershed in Hunan Province was simulated in 2017. Then the simulation results were compared with the hydrological model simulation results and observations. In the process of model simulation, a graphics processing unit (GPU) parallel algorithm was applied in approaching the problems of a large number of grids and slowing the operation speed. The results show that high-resolution topographic data collected by laser lidar are helpful in accurately simulating the rainfall-runoff process on the slope of a watershed and the effect of microtopography on the flood process, and then the flood confluence process on the whole watershed can be obtained. The GPU parallel algorithm increased the computational efficiency of the model nearly 50 times, so that the computational time was less than the runoff confluence time of the watershed. The peak-to-present time error of hydrodynamic model calculations is 1 h, and the peak error is 19.8%, which indicates that the calculations of the model have good accuracy. The model is available for forecasting, warning, and three-dimensional deduction of torrential rains and mountain torrents.